# What is the max size of the wire to the motor.



## esoneson (Sep 1, 2008)

Ok, you suckered me in to answering a question with a question.

Why not put your Ferrite Hall effect sensor around the bus bar that the cable connects to, then you don't have to worry about the size of the cable. Just asking.




bjfreeman said:


> I am working on a Ferrite Hall effect sensor you put the wire/cable through.
> Does any controller have a size bigger than #4?


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## major (Apr 4, 2008)

bjfreeman said:


> I am working on a Ferrite Hall effect sensor you put the wire/cable through.
> Does any controller have a size bigger than #4?


Sure. A lot of EV conversions use 2/0 in the motor loop. Some go to 4/0. AWG, of course


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## bjfreeman (Dec 7, 2011)

esoneson said:


> Ok, you suckered me in to answering a question with a question.
> 
> Why not put your Ferrite Hall effect sensor around the bus bar that the cable connects to, then you don't have to worry about the size of the cable. Just asking.


are you thinking of DC ?
AC the bus will give you total not each phase.
Using a Toroid hall effect that is already manufactured.
They can not accommodate bus bar, as least the ones I use.
I am using it to produce realtime graphs and data.


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## bjfreeman (Dec 7, 2011)

major said:


> Sure. A lot of EV conversions use 2/0 in the motor loop. Some go to 4/0. AWG, of course


Motor loop as in between controller and motor? the word loop 
2/0 is the largest?
I use marine cable it has a thicker coating than most welder cable I see.

yes I am a old hold out still learning the metric and imperial system.


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## major (Apr 4, 2008)

bjfreeman said:


> Motor loop as in between controller and motor? the word loop
> 2/0 is the largest?
> I use marine cable it has a thicker coating than most welder cable I see.
> 
> yes I am a old hold out still learning the metric and imperial system.


AWG is not metric. By motor loop, yes from controller to motor and including reversing contactor, and field to armature in the case of DC series motors. 4/0 is larger than 2/0. And good point about insulation thickness difference.

ref: http://www.powerstream.com/Wire_Size.htm


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## steven4601 (Nov 11, 2010)

If the motor has a junction box, can the CP's be mounted there? A copper adapter could be used then. 

What is the average phase current? 100m2 sounds beefy.


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## bjfreeman (Dec 7, 2011)

major said:


> AWG is not metric. By motor loop, yes from controller to motor and including reversing contactor, and field to armature in the case of DC series motors. 4/0 is larger than 2/0. And good point about insulation thickness difference.
> 
> ref: http://www.powerstream.com/Wire_Size.htm


LOL finally sinks in the 4/0=0000
thanks good to know.
looks like I may have to manufacture new Ferrite Hall effects.
I will have to experiment to see the extremes.
will see if an toroid that accomodates 4/0 will be sensitive enough for #4.


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## bjfreeman (Dec 7, 2011)

steven4601 said:


> If the motor has a junction box, can the CP's be mounted there? A copper adapter could be used then.
> 
> What is the average phase current? 100m2 sounds beefy.


I have run accross some 500 amp bus bar however I am not isolated.
not familiar with 100m2.

I design for max conditions.
like my 200KW takes max 800 amps but on level not accelerating it 29 amps


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## steven4601 (Nov 11, 2010)

ha-ha.that was a typo. Just the though of a 100 square meter conductor.

4/O AWG is (about the) same as metric 100mm2. (mm2 square mili-meter) 


Why do you design for maximum current if it is not the average? Wouldn't it make much more sense to calculate the heating of the conductors during peak-current conditions? From there a temperature rise can be estimated which will determine max safe operating currents for a given cross-section. Not like the vehicle will be slower from using thinner wires, possibly even faster due to the lack of mass!


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## bjfreeman (Dec 7, 2011)

steven4601 said:


> ha-ha.that was a typo. Just the though of a 100 square meter conductor.
> 
> 4/O AWG is (about the) same as metric 100mm2. (mm2 square mili-meter)
> 
> ...


simple answer:
I have seen too many ICE that fail because someone want to be "economical".
I have seen HEV catch fire because it was Under designed.
To be realistic, if you live in a flat land, your usage will be different than those that lives in area that has a lot of 25 to 45 degree grades.
My goal is to be able to climb a mountian pass at highway speeds (60 mph). some of the passes I go through post a 15% Grade for miles.


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## bjfreeman (Dec 7, 2011)

Another thing I am trying to resolve.
4/0 awg says that 380 amp max
what size is being used for these controllers that state 500-1000 amp?
At those currents, the cable would heat and would have power loss through voltage drop, not to mention possible insulation melting or catching on fire.

What am I missing?


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## muffildy (Oct 11, 2011)

you could go up to MCM
http://www.wesbellwireandcable.com/Electricalwire/Electricalwire600.html
and if you were really worried, you could even do 2 or 3 runs of it.

*edit* link to ampacity chart:
http://www.paigewire.com/ampacity_chart.htm


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## Ziggythewiz (May 16, 2010)

bjfreeman said:


> 4/0 awg says that 380 amp max
> What am I missing?


Where did you get that number? Might be the max rating for continuous current.


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## bjfreeman (Dec 7, 2011)

Ziggythewiz said:


> Where did you get that number? Might be the max rating for continuous current.


http://www.powerstream.com/Wire_Size.htm
and when at full throttle climbing a 25 degree grade, is the current not close to continous.


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## bjfreeman (Dec 7, 2011)

muffildy said:


> you could go up to MCM
> http://www.wesbellwireandcable.com/Electricalwire/Electricalwire600.html
> and if you were really worried, you could even do 2 or 3 runs of it.
> 
> ...


have you used this successfully in a EV?


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## major (Apr 4, 2008)

bjfreeman said:


> Another thing I am trying to resolve.
> 4/0 awg says that 380 amp max
> what size is being used for these controllers that state 500-1000 amp?
> At those currents, the cable would heat and would have power loss through voltage drop, not to mention possible insulation melting or catching on fire.
> ...


Hi bj,

This might help: http://www.diyelectriccar.com/forums/showpost.php?p=245897&postcount=6 

major


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## Ziggythewiz (May 16, 2010)

bjfreeman said:


> http://www.powerstream.com/Wire_Size.htm
> and when at full throttle climbing a 25 degree grade, is the current not close to continous.


doesn't say there, but look continuous to me. Continuous is a function of time, not effort, so it depends how long your grade is.


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## bjfreeman (Dec 7, 2011)

Ziggythewiz said:


> doesn't say there, but look continuous to me. Continuous is a function of time, not effort, so it depends how long your grade is.


another approach,
when a controller says it is a 500-1,000 amp, I think in continuous, not 40% duty cycle.
is this advertizing hype?


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## bjfreeman (Dec 7, 2011)

major said:


> Hi bj,
> 
> This might help: http://www.diyelectriccar.com/forums/showpost.php?p=245897&postcount=6
> 
> major


my frame of mind is more with 200KW and more.
Most designs I have seen limit the Current to 300 amp, which means you need to jack up the voltage.
Seeing controllers that say they use 500-1,000 amp puzzle me as to how to wire that to a motor.


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## major (Apr 4, 2008)

bjfreeman said:


> my frame of mind is more with 200KW and more.
> Most designs I have seen limit the Current to 300 amp, which means you need to jack up the voltage.
> Seeing controllers that say they use 500-1,000 amp puzzle me as to how to wire that to a motor.


What I said is adequate for most installations. Even if you have a 1000 Amp controller, if the motor is rated at 200 to 250 Amps continuous (or one hour), size the wire for the rating of the motor, not the controller. Use the average current, not the maximum current for sizing cable. The exception, as I mention, is for enclosed (in conduit) or lengthy cable runs. Also, if it is known that severe overloads will be common, increase the cable size 1 or 2 gauges because the heat is really an I²T function as oppose to an average I * T. Voltage has nothing to do with the actual conductor size (AWG) but would influence the cable insulation. The temperature rating of the cable insulation also influences the cable ampacity rating.


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## bjfreeman (Dec 7, 2011)

major said:


> What I said is adequate for most installations. Even if you have a 1000 Amp controller, if the motor is rated at 200 to 250 Amps continuous (or one hour), size the wire for the rating of the motor, not the controller. Use the average current, not the maximum current for sizing cable. The exception, as I mention, is for enclosed (in conduit) or lengthy cable runs. Also, if it is known that severe overloads will be common, increase the cable size 1 or 2 gauges because the heat is really an I²T function as oppose to an average I * T. Voltage has nothing to do with the actual conductor size (AWG) but would influence the cable insulation. The temperature rating of the cable insulation also influences the cable ampacity rating.


I guess my logic was not clear.
if 4/0 has a resistance that there is a voltage drop at 380 amp as well has heat generated at 300 amps, then any motor that draws over 380 amp, will overload 4/0.
so the limit based on 4/0 is 380 amp so to get more KW you need to raise the voltage, which how the 765 V @ 300 amp got determined. it is hard to go up a gauge when you are @ 4/0.
Your are correct that voltage has nothing todo with the size only the insulation of the cable. My reference to voltage was what the Controller needed to provide to get the KW at 300 amp.
with all that said, there is no one that has run a motor at 500-1,000 amp currently so controllers that hype that are just for impressing.


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## major (Apr 4, 2008)

bjfreeman said:


> there is no one that has run a motor at 500-1,000 amp currently so controllers that hype that are just for impressing.


EVfun does 



EVfun said:


> It can be used as a transmission, in a manner of speaking. That is largely the effect of setting the controller motor current limit higher than the controller battery current limit.
> 
> I have been running the motor current limit as 840 amps while I limit the battery current to 420 amps (7C for my Li cells.) This gives me a flat torque band of about 136 ft-lb or torque up to about 1500 rpm. From 1500 rpm to 3100 rpm I have a flat horsepower band, meaning the torque declines as the rpm rises until I get to about 68 ft-lb of torque at 3100 rpm (40 horsepower.) Above 3100 rpm the motor can see full pack voltage and draw less than 420 amps (declining torque and horsepower as the rpm increases.)
> 
> ...


He runs 840 Amps through his 7.2 inch series motor, and regularly, I suspect, but for short time periods. That particular motor is rated about 200 Amps for one hour (which is pretty close to continuous). I think I recall he uses 2/0 for the motor loop.

We have controllers with legitimate ratings of 1600, 2000 and even 3000 Amps now. These would be short time rated values, but some do carry continuous ratings of 500 Amps when liquid cooled. 

DC motors are common which can handle over 1000 Amps for short times, some up to nearly twice that. Most DC motors (9, 11 & 13") will have one hour ratings in the 200 to 250 Amp range. There are a few monster DC 13 inchers with like 340 Amp one hour ratings.


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## bjfreeman (Dec 7, 2011)

major said:


> EVfun does
> 
> 
> 
> ...


my only response in this thread based on Kirchoff law is his max current is battery current to 420 amps. the rest should be addressed in the original thread.

As far as cable the recommeded max is based on the ohms of the cable. So if you go over the recommeded you will have a voltage drop, hence power loss. this is dependent on cable length in the loop being used, from battery to the motor and back.


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## major (Apr 4, 2008)

bjfreeman said:


> As far as cable the recommeded max is based on the ohms of the cable. So if you go over the recommeded you will have a voltage drop, hence power loss. this is dependent on cable length in the loop being used, from battery to the motor and back.


As an example let's use 10 meters of 2/0 copper cable. Total resistance of that 10 meters is 0.00255Ω. At 200A, there is a 0.51 Volt drop. With a 300V system it represents 0.17% loss. At 1000A it would be 0.85% loss. 

Of course you have a voltage drop and power loss in the cable. And those figures are a fraction of a percent. It is difficult for the DIY hobbyist to relate to such numbers when choosing cable size. That is why they should figure the average current in the cables and use the ampacity charts for the type of cable they intend to use.

And as mentioned before, when determining the average current for the cables, don't forget that motor current is always greater than battery current (except at zero and 100% PWM). For the motor cables it is proper to size them for the motor rated current (use the one hour rating). 

Actually the battery cables should be sized to the fuse rating. Often an over sized fuse is used therefore the suggestion of sizing battery cables to the average battery current.


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## Yabert (Feb 7, 2010)

bjfreeman said:


> with all that said, there is no one that has run a motor at 500-1,000 amp currently so controllers that hype that are just for impressing.


I also does! 
It can pass 1000A in the motors cables when I start from 0 mph, but only for few seconds.
Why? because I reach fast 35 mph and I don't need 1000A to maintain that speed (only 50 to 150A in my case).

So yes, I lose few watt for few seconds (few wh of energy) in my 2/0 cables.

Example for motor cables: 4 feets lenght (0.0003 ohm) = 0.3v drop at 1000A = 300w loss for 3 sec = 0.25 wh of energy loss... that represent a small small small fraction of my battery pack capacity.


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## bjfreeman (Dec 7, 2011)

> don't forget that motor current is always greater than battery current (except at zero and 100% PWM).


based on Kirchoffs law this is not correct. Now if some one uses a multimeter instead of a scope they will get erroneous reading. PWM is like AC except you have duty cycles that are not like a Sinusoidal wave that Meter are intended to measure. AC settings on a Meter displays the RMS of the AC Sinusoidal.
What ever you current is in a series circuit is what the total current is in all the circuit (kirchoffs law). Now if you want to get into resonating circuits then the measuring is different than continous and PWM current.
Next I agree with the short period and 200 amp, yet anyone that has read this thread knows I am speaking of continuous 500-1000 amp. So talking about Short burst is not germane to the thread.
if you live in a flat land enviorment, your average will be closer to 40%, since you peaks are usually just starts. 

The difference is that if you max usage is more towards the continuous, like climbing a mountian or a mile of steep hills The average is closer to continuous, so your choice of cable will be different.
Even in ICE going up steep miles of a grade, have over heated engines, that require them to stop.
The same is True of EV in the same environment, except the damage could be fire or blown semiconductors.


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## Ziggythewiz (May 16, 2010)

Power out will never exceed power in. The battery circuit is series, and so is the motor circuit, but they are separate circuits with a motor controller connecting them.

The motor controller takes the full pack voltage and the required amps to drive the motor at what is effectively (usually) less than pack voltage with the desired amount of power. It's how your motor runs at less than full speed.


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## major (Apr 4, 2008)

bjfreeman said:


> major said:
> 
> 
> > don't forget that motor current is always greater than battery current (except at zero and 100% PWM).
> ...


bj,

The motor controller is not just a series component. The load side (motor) has more than one path. Therefore the motor current is greater than the source (battery) current. The PWM controller is not like a series resistor. It is a buck converter. Do some research on "buck converter" and you will learn about current multiplication. It functions similar to a transformer inasmuch as the output voltage current product equals the input voltage current product. So when the controller reduces the supply voltage to the motor, the motor current is higher than the supply current.

There has been actual test result graphs posted on threads in this forum showing this.

Regards,

major


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## major (Apr 4, 2008)

bjfreeman said:


> yet anyone that has read this thread knows I am speaking of continuous 500-1000 amp.


bj,

This is untrue. I have read this thread, several times. How can the reader know what you mean unless you type it? Here is where you mention 500-1000 amps. 


bjfreeman said:


> Another thing I am trying to resolve.
> 4/0 awg says that 380 amp max
> what size is being used for these controllers that state 500-1000 amp?
> At those currents, the cable would heat and would have power loss through voltage drop, not to mention possible insulation melting or catching on fire.
> ...


I see the word max in there. I do not see continuous.

Now to the point. I have said you need to size the cable to your average current or to the motor rating. If you have a system designed to do much hill climbing, then you have a high average current and a higher than normal motor rating. 

The term average must be taken in context for the particular application. It would be ridiculous to use the average over a year. Also ridiculous over 10 milliseconds. For most EVs, the average for an hour of normal driving works well. If you climb long grades, you may have to use the average over a 10 or 15 minute period.

Regards,

major


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## bjfreeman (Dec 7, 2011)

major said:


> bj,
> 
> The motor controller is not just a series component. The load side (motor) has more than one path. Therefore the motor current is greater than the source (battery) current.


Kirchoff law say the sum of the paths equal the total current.


> The PWM controller is not like a series resistor. It is a buck converter. Do some research on "buck converter" and you will learn about current multiplication. It functions similar to a transformer inasmuch as the output voltage current product equals the input voltage current product. So when the controller reduces the supply voltage to the motor, the motor current is higher than the supply current.


I designed my first Buck converter back in the early 80's, for solar powered SCADA.
what you describe is not a buck converter but a impeadance matching voltage drop.
I use a Buck Circut to boost my battery pack Voltage to my Raw dc bus that feeds my controller. minus the losses of the converter, I have the same Watts but more voltage and less current.


> There has been actual test result graphs posted on threads in this forum showing this.
> 
> Regards,
> 
> major


please give me a link so I can see where the misunderstanding is.


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## major (Apr 4, 2008)

bjfreeman said:


> please give me a link so I can see where the misunderstanding is.


I know I have seen a number of them posted by Tess and Qer for the Evnetics drives. But have trouble finding ones with battery current traces. So here is a good example from Plasmaboy.










You will note that from 3.3 seconds to 6 seconds the green trace (motor current) is about 2000 Amps. During that same period, the pink trace (battery current) is lower. After 6 seconds, the controller is at 100% PWM and motor and battery currents are equal.


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## bjfreeman (Dec 7, 2011)

Ziggythewiz said:


> Power out will never exceed power in. The battery circuit is series, and so is the motor circuit, but they are separate circuits with a motor controller connecting them.


if you trace from one post of the battery pack to the controller to the motor back to the other battery post is one circuit. An AC motor you have 3 circuits to the motor but only one is on at a time hence phases.


> The motor controller takes the full pack voltage and the required amps to drive the motor at what is effectively (usually) less than pack voltage with the desired amount of power. It's how your motor runs at less than full speed.


I agree it accomplishes this, usually, with PWM that turns on the current for less than full current all the time.


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## bjfreeman (Dec 7, 2011)

is there a larger version I can not make our what line is what.
also the setup (where the probess were connected).
and the scope multiplier for each probe


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## Ziggythewiz (May 16, 2010)

bjfreeman said:


> if you trace from one post of the battery pack to the controller to the motor back to the other battery post is one circuit.


So if I trace from one post of my battery pack, to my charger...to your charger, to one post on your battery pack, is one circuit?


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## bjfreeman (Dec 7, 2011)

Ziggythewiz said:


> So if I trace from one post of my battery pack, to my charger...to your charger, to one post on your battery pack, is one circuit?


do you like to be difficult?
are the two connected?


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## dladd (Jun 1, 2011)

BJ, Are you really saying that you don't think the motor current can be higher than the battery current? Just checking, I'm not quite following what you are saying.

I know in my (DC powered) car I routinely hit 500a to the motor when accelerating and have my battery pack limited to 300a. And I'm pretty sure I'm not violating any laws of nature...

The curve Major posted shows it perfectly, just look at the pink and green lines, ignore the rest.


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## major (Apr 4, 2008)

bjfreeman said:


> is there a larger version I can not make our what line is what.
> also the setup (where the probess were connected).
> and the scope multiplier for each probe


I lifted the photo from http://www.plasmaboyracing.com/history/2010.php About 2/3 way down the page. You should be able to blow it up on your computer.

This is a Zilla data dump. Current traces are from current shunts in the Zilla.

Yes, there is a 10 factor multiplier on that chart for voltage and temperature. RPM and Amps are 1 to 1.

I've seen hundreds of such plots over the years and done the measurements myself. Motor current is always higher than battery current at less than 100% PWM. It has been discussed at length many times here.


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## Ziggythewiz (May 16, 2010)

bjfreeman said:


> are the two connected?


If we're on the same nation's grid, then yes. Yes they are.


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## bjfreeman (Dec 7, 2011)

Ziggythewiz said:


> If we're on the same nation's grid, then yes. Yes they are.


my charger is a generator. Not on power grid.


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## major (Apr 4, 2008)

major said:


> I know I have seen a number of them posted by Tess and Qer for the Evnetics drives.


Here's one from Qer: 

http://www.diyelectriccar.com/forums/showpost.php?p=270650&postcount=300


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## bjfreeman (Dec 7, 2011)

major said:


> Motor current is always higher than battery current at less than 100% PWM. It has been discussed at length many times here.


say 40% PWM is passing more current than 100% or full on,
don't does not compute.
by definition amp is based on time. if the current does not flow for 60% it will be less than amp for that time period.


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## Ziggythewiz (May 16, 2010)

bjfreeman said:


> my charger is a generator. Not on power grid.


Ok, so just the rest of us use a single circuit.

My point is that the fact that things are connected does not make them a single circuit, and your whoever's law is being misapplied.


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## bjfreeman (Dec 7, 2011)

dladd said:


> I know in my (DC powered) car I routinely hit 500a to the motor when accelerating and have my battery pack limited to 300a.


so lets get down to how this is accomplished
how do you measure these two parameters.
how do you accomplish the limiting of the battery pack.
how do you allow 500 amp to flow to the motor.


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## major (Apr 4, 2008)

bjfreeman said:


> say 40% PWM is passing more current than 100% or full on,
> don't does not compute.
> by definition amp is based on time. if the current does not flow for 60% it will be less than amp for that time period.


bj,

If you take the time to look at "buck converter" you will learn that the output (motor in our case) current is the sum of the switch current (battery current) and the FWD (free wheeling diode) current. The output inductor (which is the motor itself in the case of the motor control application of a buck converter) stores energy and maintains load current (motor current) during the "off" portion of the PWM when battery current ceases to flow.

This in no way violates Kirchhoff's Law. The buck converter is a simple 4 component circuit. Draw it out and satisfy yourself. At the node for the load you have 3 branches. The switch, the FWD and the load. The load current is the sum of the switch current and the FWD current.

major


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## bjfreeman (Dec 7, 2011)

Ziggythewiz said:


> Ok, so just the rest of us use a single circuit.
> 
> My point is that the fact that things are connected does not make them a single circuit, and your whoever's law is being misapplied.


Not really, you source power for the charger is the generator at the power plant. so if you trace from the power plant to each charger back through the gound to the power plant follows the Kirchoff law of sum of paths equal the total current supplied by the power plant.
and before you bring up multiple power plants, that is the same as paralleled batteries.
Now the orginal was about the car power path when operating so the charge is not connected so there is no common.
you really should learn basic electricity before trying to converse.


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## bjfreeman (Dec 7, 2011)

major said:


> bj,
> 
> If you take the time to look at "buck converter" you will learn that the output (motor in our case) current is the sum of the switch current (battery current) and the FWD (free wheeling diode) current. The output inductor (which is the motor itself in the case of the motor control application of a buck converter) stores energy and maintains load current (motor current) during the "off" portion of the PWM when battery current ceases to flow.
> 
> ...


you finally brought up the key. still the same current but you are adding stored energy the coil. That is why is is called Buck.
so if you map the charging of the coil then releasing it with the standard current, you have the same total current supplied by battery.
you description shows me where you logic is faulty.


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## major (Apr 4, 2008)

bjfreeman said:


> so lets get down to how this is accomplished
> how do you measure these two parameters.
> how do you accomplish the limiting of the battery pack.
> how do you allow 500 amp to flow to the motor.


I can tell you how I do it. Use a motor controller. Put a shunt in the battery cable and another shunt in the motor cable. Connect a separate ammeter to each shunt. The motor controller limits motor current. Lift the throttle to limit battery current.


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## palmer_md (Jul 22, 2011)

I may be way off base, but let me take a stab at it and if y'all feel I'm making things more confusing I'll stop.

The controller is not controlling the current, but rather the voltage applied to the motor. Current is a simple result of the resistance in the circuit to which we apply this voltage. It is essentially a switched mode power supply connected to the motor.

You can say you are controlling the current, but it is an indirect control. You are directly controlling the voltage and it has a relationship to the current which you are trying to control.


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## major (Apr 4, 2008)

bjfreeman said:


> you finally brought up the key. still the same current but you are adding stored energy the coil. That is why is is called Buck.
> so if you map the charging of the coil then releasing it with the standard current, you have the same total current supplied by battery.
> you description shows me where you logic is faulty.


Who's logic is faulty


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## bjfreeman (Dec 7, 2011)

major said:


> Who's logic is faulty


I have been hired may times to bring engineering projects back in budget and on time.
I had to replace PHD, Dr, and BS with one that did not want to argue the correctness of their knowledge but find solutions to get the project to manufacturing in a way it was profitable to build.
I have many projects under my belt.
with that I will let you think the way you want.


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## bjfreeman (Dec 7, 2011)

major said:


> I can tell you how I do it. Use a motor controller. Put a shunt in the battery cable and another shunt in the motor cable. Connect a separate ammeter to each shunt. The motor controller limits motor current. Lift the throttle to limit battery current.


Ah there is the rub.
first ammeter are not geared to PWM.
if you look at the shunt on the output of the controller, through a scope you will see there is a time that no current flows, then there is a rush of current. if you watch the battery shunt the flow is constant.
so the converter is storing current and putting out more but for a shorter time which equals the total current that flowed from battery.


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## dladd (Jun 1, 2011)

bjfreeman said:


> so lets get down to how this is accomplished
> how do you measure these two parameters.
> how do you accomplish the limiting of the battery pack.
> how do you allow 500 amp to flow to the motor.


shunt and ammeter on both sides of the controller. For my part, I just enter the desired current values into the software that is provided by my controller manufacturer. No idea how it's done in the controller, but I suggest that you are missing a basic understanding of how a controller works. If you want to know the details, you need to be willing to learn. I don't see that happening...

I'm a mechanical guy, to me a controller is a black box. The way I see it, power in = power out (minus losses). And power equals volts x amps. The battery pack is a more or less fixed voltage. The motor goes from 0 volts at 0rpm to pack voltage at top speed. In between, due to the all present conservation of energy, it is quite clear that motor amps MUST be higher than battery amps.


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## bjfreeman (Dec 7, 2011)

dladd said:


> shunt and ammeter on both sides of the controller.


I already explained the fallacy of that method to Major.



> For my part, I just enter the desired current values into the software that is provided by my controller manufacturer. No idea how it's done in the controller, but I suggest that you are missing a basic understanding of how a controller works. If you want to know the details, you need to be willing to learn. I don't see that happening...


Unless you know what it is I should know, How do you know I don't know it.


> I'm a mechanical guy, to me a controller is a black box. The way I see it, power in = power out (minus losses). And power equals volts x amps. The battery pack is a more or less fixed voltage. The motor goes from 0 volts at 0rpm to pack voltage at top speed. In between, due to the all present conservation of energy, it is quite clear that motor amps MUST be higher than battery amps.


1) I have built and am running a controller that handles 250Kw That includes the hardware and software.
2) I explained in simple non technical terms why is seems that way.


----------



## major (Apr 4, 2008)

bjfreeman said:


> Ah there is the rub.
> first ammeter are not geared to PWM.
> if you look at the shunt on the output of the controller, through a scope you will see there is a time that no current flows, then there is a rush of current. if you watch the battery shunt the flow is constant.
> so the converter is storing current and putting out more but for a shorter time which equals the total current that flowed from battery.


I have used a scope on such circuits many times. The ammeters reflect the average current very well.



> *The principles*
> 
> *To control the speed of a d.c. motor we need a variable voltage d.c. power source. However if you take a 12v motor and switch on the power to it, the motor will start to speed up: motors do not respond immediately so it will take a small time to reach full speed. If we switch the power off sometime before the motor reaches full speed, then the motor will start to slow down. If we switch the power on and off quickly enough, the motor will run at some speed part way between zero and full speed. This is exactly what a p.w.m. controller does: it switches the motor on in a series of pulses. To control the motor speed it varies (modulates) the width of the pulses - hence Pulse Width Modulation. *
> 
> ...


The diagrams didn't copy. You can view it here: http://www.4qdtec.com/pwm-01.html

And another one:



> *Current multiplication*​
> 
> During acceleration and during reduced speed operation, the Curtis PMC controller allows more current to flow into the motor than flows out of the battery. The controller acts like a dc transformer, taking in low current and high voltage (the full battery voltage) and putting out high current and low voltage. The battery needs to supply only a fraction of the current that would be required by a conventional controller (in which the battery current and motor current are always equal). The current multiplication feature gives vehicles using Curtis PMC controllers dramatically greater driving range per battery charge.​


From the Curtis manual. I think they know how motor controllers work.


----------



## major (Apr 4, 2008)

bjfreeman said:


> I have been hired may times to bring engineering projects back in budget and on time.
> I had to replace PHD, Dr, and BS with one that did not want to argue the correctness of their knowledge but find solutions to get the project to manufacturing in a way it was profitable to build.
> I have many projects under my belt.
> with that I will let you think the way you want.


And so by your logic you can never be wrong. Is that what you believe?


----------



## dladd (Jun 1, 2011)

bjfreeman said:


> Unless you know what it is I should know, How do you know I don't know it.


At least I know what I don't know.

All I'm sayin is it seems like every thread you are in ends with you disagreeing with someone. And usually in a fairly defensive and condescending manner. Clearly you think you are the smartest person in the room, it's tough to learn when you set yourself up with the thought that you are never wrong.


----------



## Duncan (Dec 8, 2008)

Hi Major

I think you are on a looser here - 

Bjfreeman just makes it up as he goes along 

I don't think he has ever done anything he claims - 

he just makes too many incorrect statements for me to believe anything he says


----------



## bjfreeman (Dec 7, 2011)

so how does those description differ from my simpler one
and I think if you challenge this you would get a different response.
what I see is you have learned something without the knowledge and logic to determine it is correct or not.

so for me, this is the end of the discussion.


----------



## major (Apr 4, 2008)

bjfreeman said:


> I use a Buck Circut to boost my battery pack Voltage to my Raw dc bus that feeds my controller. minus the losses of the converter, I have the same Watts but more voltage and less current.


It is strange that you can use a buck converter to boost voltage. I think you have terminology mixed up.

But let's look at something you said there. "I have the same Watts but more voltage and less current." Now if you apply your Kirchhoff logic, how can you get less current? Where does the missing current go?


----------



## major (Apr 4, 2008)

bjfreeman said:


> so how does those description differ from my simpler one


Let me see. 

*



the average battery current is only 50% of the motor current!

Click to expand...

*



> more current to flow into the motor than flows out of the battery


Which is what I have been saying. Motor current is greater than battery current. You disagree. That is how it differs. Can you not see this?


----------



## bjfreeman (Dec 7, 2011)

major said:


> And so by your logic you can never be wrong. Is that what you believe?


I have corrected myself when that is the case on this forum.
don't see many here do that mostly act like like trolls


----------



## DIYguy (Sep 18, 2008)

This is one of my favorite quotes. It was penned by Jeff (Tesseract).

"A lot of people show up on this forum with a swinging dick attitude and what it usually gets them is being ignored by the very people most able to help them."

If you want to get a snapshot of what is going on here. . . you can read this thread http://www.diyelectriccar.com/forums/showthread.php?t=66775
I, mistakenly, attempted to offer assistance . . and after offering several tidbits that BJ obviously didn't know, he ends up reverting to his swinging dick attitude. What also became evident was the repeated flip-flop between what he already has and what he plans to do. . . . I too wonder about the realities vs imagery.

This is a place to visit, learn and hopefully give something back. I hope that I fit into this category as many others certainly do.

Obviously Mr. Freeman, you have it all figured out. Don't waste the time of someone who spends an inordinate amount of time freely giving of his knowledge, wisdom and experience. You sir, are a legend in your own mind.


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## frodus (Apr 12, 2008)

bjfreeman said:


> if you look at the shunt on the output of the controller, through a scope you will see there is a time that no current flows, then there is a rush of current. if you watch the battery shunt the flow is constant.


With regards to Electric Vehicle Motor Controllers:

If you look at a motor with a scope and a shunt, it'l show current flow in the motor loop when the FET's are off, but PWM > 0. All because there's a Free Wheel Diode in that circuit. When the motor is being told to rotate by the controller, there is always current flowing. The motor loop consists of Motor and Free Wheel Diode. The FET or IGBT injects current into that loop. At 0% PWM, you are correct, there is no current flow. 

But, when PWM > 0, and the PWM signal of the FET is on, the FET inside the controller feeds current into the motor loop. Because of the Free Wheel Diode, current flows in one direction in the loop. When the FET turns off, the FWD and Motor are the only thing in the motor loop again, and due to the large inductance of the motor, current stays flowing in that loop. Then the next time the FET turns, current is fed into the motor loop again. As long as the FET turns on before the natural decay of current due to the motor impedance, current continues to flow. If the PWM is removed, the current in the motor loop will quickly degrate due to the impedance of the motor, but current will flow when there is a PWM signal above 0%.


----------



## bjfreeman (Dec 7, 2011)

dladd said:


> At least I know what I don't know.
> 
> All I'm sayin is it seems like every thread you are in ends with you disagreeing with someone. And usually in a fairly defensive and condescending manner. Clearly you think you are the smartest person in the room, it's tough to learn when you set yourself up with the thought that you are never wrong.


usually someone tries to correct me and I freely show them how that is not correct in the context they present in.
and they choose not to research this to see if I am correct.


----------



## frodus (Apr 12, 2008)

a little tidbit about what I'm talking about:
http://homepages.which.net/~paul.hills/SpeedControl/SpeedControllersBody.html


----------



## bjfreeman (Dec 7, 2011)

frodus said:


> With regards to Electric Vehicle Motor Controllers:
> 
> If you look at a motor with a scope and a shunt, it'l show current flow in the motor loop when the FET's are off, but PWM > 0. All because there's a Free Wheel Diode in that circuit.


so where does the current that is flowing through diode comes from.
is it flowing in the same direction as current that came from the battery, or is it due to the field collapse of the motor?
normally refereed to as Back EMF.



> When the motor is being told to rotate by the controller, there is always current flowing. The motor loop consists of Motor and Free Wheel Diode.


always is ambiguous since PWM, only has battery current flows part time then the stored energy flows through FWD the reverse direction this is less but still current from the previous battery cycle of current.



> The FET or IGBT injects current into that loop. At 0% PWM, you are correct, there is no current flow.
> 
> But, when PWM > 0, and the PWM signal of the FET is on, the FET inside the controller feeds current into the motor loop. Because of the Free Wheel Diode, current flows in one direction in the loop.


the flow through the FWD is not my understanding.



> When the FET turns off, the FWD and Motor are the only thing in the motor loop again, and due to the large inductance of the motor, current stays flowing in that loop.


I agree,


> Then the next time the FET turns, current is fed into the motor loop again. As long as the FET turns on before the natural decay of current due to the motor impedance, current continues to flow.


if is a function of the Q of the inductance. The more Q the more is Stored and returned.



> If the PWM is removed, the current in the motor loop will quickly degrate due to the impedance of the motor, but current will flow when there is a PWM signal above 0%.


 Impedance is used in LC circuits It composes of Inductance, capaticitance and resistance and is the Reactive equivalent to resistance. The higher the Resistance component the lower the Q. so the rate of decay is a function of Q.


----------



## dladd (Jun 1, 2011)

bjfreeman said:


> usually someone tries to correct me and I freely show them how that is not correct in the context they present in.
> and they choose not to research this to see if I am correct.


yes. I see that is how you see it. That is not what is happening though.


----------



## bjfreeman (Dec 7, 2011)

DIYguy said:


> This is one of my favorite quotes. It was penned by Jeff (Tesseract).
> 
> "A lot of people show up on this forum with a swinging dick attitude and what it usually gets them is being ignored by the very people most able to help them."
> 
> ...


in that reguards I have my 12 years working with HEV and Commercial applications for Bus Fleets. Getting Greasy with the mechs.
and I get the same tude from some here as well.


----------



## frodus (Apr 12, 2008)

> so where does the current that is flowing through diode comes from.


It comes from from when the FET is ON. The inductor, by nature, keeps the current flowing for a small amount of time. 



> is it flowing in the same direction as current that came from the battery, or is it due to the field collapse of the motor?


 It's flowing in the motor loop in the direction of the diode. Through the diode, into the motor, back out, back into the diode. 

Like this:











> always is ambiguous since PWM, only has battery current flows part time then the stored energy flows through FWD the reverse direction this is less but still current from the previous battery cycle of current.


Not ambiguous at all, just sometimes difficult to grasp. But, Battery current flows continuously as long as PWM > 0. The capacitors in the controller AND the battery supply current when the FET is on. When it's off, current flows from batteries into the capacitor bank. Both motor current and battery current are nonzero as long as PWM > 0.



> the flow through the FWD is not my understanding.


It was hard to grasp for me at first, but sitting down with an Industrial Motor Drive designer for GE Industrial Systems (my father) as well as Ives Meadors from Synkromotive and Bob Simpson of EVdrive, I was able to get it. Current flow into and out of the controller is nonzero when PWM is > 0.

It's much easier to see if you do actually do what was discussed. Take a shunt and put one on the motor side, one on the battery side, and measure the current through them on a scope. Unless the controller PWM = 0, current will be flowing in both loops.



> I agree,
> if is a function of the Q of the inductance. The more Q the more is Stored and returned.
> Impedance is used in LC circuits It composes of Inductance, capaticitance and resistance and is the Reactive equivalent to resistance. The higher the Resistance component the lower the Q. so the rate of decay is a function of Q.


Exactly. So, FET On. Current into motor loop is flowing. FET Off, Current in motor loop is no longer fed by the FET, and decay starts. This is a function of R L and C. Fairly low capacitance in large motors like this, but there's a ton of Inductance, and a bit of Resistance. So if you Give a motor and FWD a pulse, and wait for it to decay, current will stop.

But with controllers, the frequency of that pulse is always designed to be faster than the rate of decay of the RLC circuit and FWD loop.


----------



## bjfreeman (Dec 7, 2011)

frodus said:


> a little tidbit about what I'm talking about:
> http://homepages.which.net/~paul.hills/SpeedControl/SpeedControllersBody.html


yes this is what I agree with, but not what has been communicated here.


----------



## major (Apr 4, 2008)

bjfreeman said:


> major said:
> 
> 
> > don't forget that motor current is always greater than battery current (except at zero and 100% PWM).
> ...


So not to lose track of what we were discussing, who is right, me or bj?


----------



## frodus (Apr 12, 2008)

bjfreeman said:


> yes this is what I agree with, but not what has been communicated here.


We're discussing several interrelated things.

Until we all can understand how a controller works, it's difficult to see why motor current is always greater than or equal to battery current. It's never less than battery current. 

The instantanious current into the FET is equal to the current from the battery + the current from the capacitor bank inside the controller.
A(batt) + A(Cap) = A(FET)

The current in the motor loop after the FET being turned on is equal to the existing current in the motor loop (which is decaying due to impedance) + the current from the FET.
A(motor_after) = A(motor_before) + A(FET)

With those two equations we get
A(motor_after) = A(motor_before) + A(batt) + A(Cap)

That's why it's always more, because the battery isn't the only thing contributing current into the loop.

Even if A(Cap) is nearly zero, you always get:
A(motor_after) = A(motor_before) + A(batt)


----------



## frodus (Apr 12, 2008)

major said:


> So not to lose track of what we were discussing, who is right, me or bj?


I am 

becuz I explain bettererer and I gotz diagramz yo!


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## bjfreeman (Dec 7, 2011)

frodus said:


> We're discussing several interrelated things.
> 
> Until we all can understand how a controller works, it's difficult to see why motor current is always greater than or equal to battery current. It's never less than battery current.


this is what I find misleading. in simplistic terms. 
the current flow into the through one path to charge the inductor (motor) the the path is turned off the fields collapses discharging through another path. What is confusing to many is the motor for the discharge become a generator, releasing the current the Battery charged upl
This is not Double or more current since it was orginally the current from the battery and is flowing between battery current flow times.
nor is it more since it came from the battery originally.


----------



## frodus (Apr 12, 2008)

read up on it some more, it's very interesting to learn.


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## bjfreeman (Dec 7, 2011)

major said:


> So not to lose track of what we were discussing, who is right, me or bj?


based o the original topic we are both off topic.


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## Duncan (Dec 8, 2008)

major said:


> So not to lose track of what we were discussing, who is right, me or bj?



Hi Major
You are right

BJ keeps talking about his experience 

- then immediately says something so silly that it blows away his credibility!


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## bjfreeman (Dec 7, 2011)

frodus said:


> read up on it some more, it's very interesting to learn.


I think you miss my point, most here don't understand and use vernacular that is misleading.


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## major (Apr 4, 2008)

bjfreeman said:


> This is not Double or more current since it was orginally the current from the battery and is flowing between battery current flow times.
> nor is it more since it came from the battery originally.


Sure, it can be double or more. Look at the chart in post #32 at 3.8 seconds. There the battery current is 500A and motor current is 2000A. And the energy comes from the battery. During the "off" period of the PWM, the motor is still in a motor mode and it is incorrect to call this regeneration because no energy is returned from the motor. There is always a generated voltage by the armature when it rotates in the presence of a magnetic field. But during the "off" period, the motor continues to produce torque so it does not become a generator.


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## Ziggythewiz (May 16, 2010)

major said:


> So not to lose track of what we were discussing, who is right, me or bj?


Yes, back to the important part:


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## major (Apr 4, 2008)

bjfreeman said:


> based o the original topic we are both off topic.


Why is that bj? Doesn't the magnitude of motor current determine the size of the wire to the motor? And we are talking about the motor current. One can get into trouble if they were to size the entire power loop to the battery current requirements and operate in modes where the motor current was greater. Wouldn't you agree?


----------



## bjfreeman (Dec 7, 2011)

basics 101:
you apply a voltage and current flows to saturate the coil, then you disconnect the coil 
what happens?


----------



## major (Apr 4, 2008)

bjfreeman said:


> basics 101:
> you apply a voltage and current flows to saturate the coil, then you disconnect the coil
> what happens?


It is irrelevant. No coils are disconnected in the normal PWM operation of the motor. You can't answer my questions after you claim I am incorrect in my explanation of a response to your original query so you start this 101 crap. Please. Just skip the Q & A and get to your point.


----------



## bjfreeman (Dec 7, 2011)

major said:


> It is irrelevant. No coils are disconnected in the normal PWM operation of the motor. You can't answer my questions after you claim I am incorrect in my explanation of a response to your original query so you start this 101 crap. Please. Just skip the Q & A and get to your point.


without a basic foundation we will continue to go in circles
what are fields and armatures made of electrically?
Explain the diagrams red lines in the link that frodus gave.


----------



## major (Apr 4, 2008)

bjfreeman said:


> without a basic foundation we will continue to go in circles
> what are fields and armatures made of electrically?
> Explain the diagrams red lines in the link that frodus gave.


You want to play Q & A? Then you have to answer questions from me and I'll answer your questions. O.K? I'll go first. I think the answer you are looking for is that the motor consists of coils for the electrical path. O.K. Your turn. When are those coils disconnected during the normal PWM operation of a motor?


----------



## bjfreeman (Dec 7, 2011)

major said:


> You want to play Q & A? Then you have to answer questions from me and I'll answer your questions. O.K? I'll go first. I think the answer you are looking for is that the motor consists of coils for the electrical path. O.K. Your turn. When are those coils disconnected during the normal PWM operation of a motor?


when you answer mine that will answer yours.
I will wait till you do.


----------



## palmer_md (Jul 22, 2011)

http://www.4qd.co.uk/fea/battC.html



> *Battery current and motor current*
> 
> A fact that many people do not realise is that a PWM controller operates rather like a transformer (using the motor's inductance) to deliver all the power it takes from the battery to the motor.
> 
> ...


----------



## major (Apr 4, 2008)

bjfreeman said:


> when you answer mine that will answer yours.
> I will wait till you do.


I did: "I think the answer you are looking for is that the motor consists of coils for the electrical path."

It is your turn.

When are those coils disconnected during the normal PWM operation of a motor?


----------



## bjfreeman (Dec 7, 2011)

palmer_md said:


> http://www.4qd.co.uk/fea/battC.html


not entirely true.
yes I know I am going against supposedly authoritative article.
I read a lot on the net that is not valid.


----------



## palmer_md (Jul 22, 2011)

bjfreeman said:


> not entirely true.
> yes I know I am going against supposedly authoritative article.
> I read a lot on the net that is not valid.


can you cite a reference to support your side?


----------



## bjfreeman (Dec 7, 2011)

major said:


> I did: "I think the answer you are looking for is that the motor consists of coils for the electrical path."
> 
> It is your turn.
> 
> When are those coils disconnected during the normal PWM operation of a motor?


nope you have not answered them all yet


----------



## bjfreeman (Dec 7, 2011)

palmer_md said:


> can you cite a reference to support your side?


mostly the laws and electrical formulas that define this. go back through the thread to see some of them.
compare yours to the link that frodus gave a few posts back and see how the two fit.


----------



## major (Apr 4, 2008)

bjfreeman said:


> nope you have not answered them all yet


You mean explain this: 










I already did.

Your turn: When are those coils disconnected during the normal PWM operation of a motor?


----------



## bjfreeman (Dec 7, 2011)

major said:


> You mean explain this:
> 
> 
> 
> ...


ok is Q1 alwasy on?


----------



## major (Apr 4, 2008)

bjfreeman said:


> mostly the laws and electrical formulas that define this. go back through the thread to see some of them.
> compare yours to the link that frodus gave a few posts back and see how the two fit.


bj,

There is nothing in that reference that supports your claim. See post #72 if you have forgotten your claim.

You have done this on previous threads where you claim citations and references support your points when they clearly do not. You have even told me you have many books that support your side, but are too busy to even supply a title and author.

Regards,

major


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## palmer_md (Jul 22, 2011)

Q1 is the MOSFET. When Q1 is on, current flows through the field and armature windings, and the motor rotates. When Q1 is turned off , the current through an inductor cannot immediately turn off, and so the inductor voltage drives a diminishing current in the same direction, which will now flow through the armature, and back through D1 as shown by the red arrow in the figure below. If D1 wasn’t in place, a very large voltage would build up across Q1 and blow it up.

This article says the same thing, in fact if you read down further they provide a reference to the article that I linked you to.



> ... There is a circuit on the 4QD site which does this...


----------



## frodus (Apr 12, 2008)

Just give up guys, it's pointless.

He reminds me of PZigouras....... I bet they could build one hell of a controller together!


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## major (Apr 4, 2008)

bjfreeman said:


> ok is Q1 alwasy on?


Not at less than 100% duty cycle, no. That is what is responsible for the PWM, Q1 switching on and off.

Your turn again. 

When are those coils disconnected during the normal PWM operation of a motor?


----------



## bjfreeman (Dec 7, 2011)

major you seem to go off topic a lot. answer the question or we are done.


----------



## bjfreeman (Dec 7, 2011)

major said:


> Not at less than 100% duty cycle, no. That is what is responsible for the PWM, Q1 switching on and off.
> 
> Your turn again.
> 
> When are those coils disconnected during the normal PWM operation of a motor?


so when Q1 is off is not coils disconnect from the battery.
so in the diagram is Q1 off or on


----------



## frodus (Apr 12, 2008)

bjfreeman said:


> so when Q1 is off is not coils disconnect from the battery.
> so in the diagram is Q1 off or on


It could be in the ON state or the OFF state of a controller that is driving the FET at anything over 0% PWM.

Current ALWAYS flows in the motor loop when PWM is nonzero. 

When PWM is zero, and Q1 is off for a time that is greater than the decay time, that loop current (the red arrow) slowly decays to zero.


----------



## major (Apr 4, 2008)

bjfreeman said:


> so when Q1 is off is not coils disconnect from the battery.


No, the battery is disconnected from the diode. The coil (motor) remains connected to the diode. The coil (motor) is never disconnected during normal PWM operation.



> so in the diagram is Q1 off or on


The red arrow in the diagram indicates a current flow through the FWD, the Q1 must be off or otherwise the FWD would be reverse biased.

My question: Ah shucks, I asked too many already. Just fire away, but make your point soon, please.


----------



## bjfreeman (Dec 7, 2011)

major said:


> bj,
> 
> There is nothing in that reference that supports your claim. See post #72 if you have forgotten your claim.
> 
> ...


I did give references as usually you conviently gloss over them. No I am not going back and find them you spend your time if it important.


----------



## frodus (Apr 12, 2008)

So here's a real life example:

Lets say a controller uses a low PWM frequency of 200hz. Lets say the motor loop decay time is 0.075th of a second.

Now, at 1% PWM, you get a pulse every 1/200ths of a second that is 0.00005 seconds in width (1% of the width between pulses, or (1/200)*0.01). That's how long the FET turns on. 0.00005 is MUCH shorter than the decay time of the motor loop, so the motor loop current never reaches zero.


----------



## bjfreeman (Dec 7, 2011)

major said:


> No, the battery is disconnected from the diode. The coil (motor) remains connected to the diode. The coil (motor) is never disconnected during normal PWM operation.


we are discussing electrical connection
Q1 is a switch. and it disconnect the motor (coils) from the battery. and yes in a PWM it is either on or off when PMW>0 and <100%


> The red arrow in the diagram indicates a current flow through the FWD, the Q1 must be off or otherwise the FWD would be reverse biased.


Now what is the source of the flow of the red arrow?
what determines the Current and voltage of the red arrow?


> My question: Ah shucks, I asked too many already. Just fire away, but make your point soon, please.


that depends on your answers.


----------



## frodus (Apr 12, 2008)

When the FET is off, No current flows from the FET into the motor loop, that is correct. HOWEVER, current still flows through the motor and Free Wheel Diode.


----------



## major (Apr 4, 2008)

bjfreeman said:


> I did give references as usually you conviently gloss over them. No I am not going back and find them you spend your time if it important.


I look at the references you cite. That's how I know they do not support your position. But I can't look at those books you have unless you tell me what they are. You apparently can't remember where you put them or the titles, yet you claim to remember the facts contained within which support your position. Sounds convenient.


----------



## bjfreeman (Dec 7, 2011)

frodus said:


> So here's a real life example:
> 
> Lets say a controller uses a low PWM frequency of 200hz. Lets say the motor loop decay time is 0.075th of a second.
> 
> Now, at 1% PWM, you get a pulse every 1/200ths of a second that is 0.00005 seconds in width (1% of the width between pulses, or (1/200)*0.01). That's how long the FET turns on. 0.00005 is MUCH shorter than the decay time of the motor loop, so the motor loop current never reaches zero.


I am not sure what you want to convey.
right now I am just trying to have the same understanding of the basic principles.


----------



## frodus (Apr 12, 2008)

You two have fun hashing it out, I'm using the rest of the time I have on this planet to do more productive things, like going downtown tonight to chase skirts and drink beer!


/unsubscribing


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## bjfreeman (Dec 7, 2011)

major said:


> I look at the references you cite. That's how I know they do not support your position. But I can't look at those books you have unless you tell me what they are. You apparently can't remember where you put them or the titles, yet you claim to remember the facts contained within which support your position. Sounds convenient.


yes and I see you as a troll, when you in this mode and that is being nice. you will just have to learn how to get over it 
my last comment you have the last word, which you just drooling over


----------



## bjfreeman (Dec 7, 2011)

frodus said:


> It could be in the ON state or the OFF state of a controller that is driving the FET at anything over 0% PWM.


for the sake the basic principle lets say PWM is 100 cycles.




> Current ALWAYS flows in the motor loop when PWM is nonzero.


under 100 cycles not necessary. in my contoller there is a test power up that starts at 1000 cycles ramps up.


> When PWM is zero, and Q1 is off for a time that is greater than the decay time, that loop current (the red arrow) slowly decays to zero.


I agree.


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## major (Apr 4, 2008)

bjfreeman said:


> we are discussing electrical connection
> Q1 is a switch. and it disconnect the motor (coils) from the battery.


You could say it disconnects the motor (coil) and diode from the battery, but it is incorrect to say that the motor (coil) becomes disconnected.



> Now what is the source of the flow of the red arrow?


The red arrow represents the FWD current which I covered previously. I guess you glossed over my explanation. So here you go again. The FWD current is a result of energy stored in the field of the inductor (motor coils).



> what determines the Current and voltage of the red arrow?


The red arrow has no voltage associated with it. The FWD clamps the coil (motor) voltage to forward drop value, about 1 volt. The current in the FWD = Ib * (1/dc - 1). Where Ib is battery current and dc = duty cycle as a fraction (100% = 1, 50% = .5, 20% = .2, etc).


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## bjfreeman (Dec 7, 2011)

major said:


> You could say it disconnects the motor (coil) and diode from the battery, but it is incorrect to say that the motor (coil) becomes disconnected.


well there is one way we don't see eye to eye.


> The red arrow represents the FWD current which I covered previously. I guess you glossed over my explanation. So here you go again. The FWD current is a result of energy stored in the field of the inductor (motor coils).


Nope try again


> The red arrow has no voltage associated with it. The FWD clamps the coil (motor) voltage to forward drop value, about 1 volt. The current in the FWD = Ib * (1/dc - 1). Where Ib is battery current and dc = duty cycle as a fraction (100% = 1, 50% = .5, 20% = .2, etc).


first you say there is no voltage then you say the diode has a volt can't have it both ways


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## major (Apr 4, 2008)

bjfreeman said:


> yes and I see you as a troll, when you in this mode and that is being nice. you will just have to learn how to get over it
> my last comment you have the last word, which you just drooling over


bj,

I was just trying to help you understand the wire size for the motor like you asked in post #1. And now you call me a troll. Thanks a lot. Why don't you finish this discussion in a reasonable manner? Get to the point of why you think I am wrong about motor current being larger than battery current.


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## bjfreeman (Dec 7, 2011)

in that case I have my answer long ago, so this is the end.
as far as my answer to my question "What is the max size of the wire to the motor."


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## major (Apr 4, 2008)

bjfreeman said:


> major said:
> 
> 
> > The red arrow represents the FWD current which I covered previously. I guess you glossed over my explanation. So here you go again. The FWD current is a result of energy stored in the field of the inductor (motor coils).
> ...


So you say that the FWD current is not a result of energy stored in the field of the load inductor. So you tell me because that is the only answer I have. Well, unless your talking about the energy coming from the battery initially, but that is too obvious and really irrelevant once Q1 opens.



bjfreeman said:


> major said:
> 
> 
> > The red arrow has no voltage associated with it.
> ...


An arrow has no voltage. It typically represents a current flow, as it does in this case. You were inquiring about a voltage, so I assumed you meant the motor voltage. So what say you to my answer? 



major said:


> The FWD clamps the coil (motor) voltage to forward drop value, about 1 volt. The current in the FWD = Ib * (1/dc - 1). Where Ib is battery current and dc = duty cycle as a fraction (100% = 1, 50% = .5, 20% = .2, etc).


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## major (Apr 4, 2008)

bjfreeman said:


> first you say there is no voltage then you say the diode has a volt can't have it both ways














major said:


> The red arrow has no voltage associated with it.


In fact the red arrow appears to close on itself and Kirchhoff tells us that the sum of the voltages around a loop must equal zero. That is why I specified the diode voltage.


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## palmer_md (Jul 22, 2011)

http://en.wikipedia.org/wiki/Flyback_diode

This concept seems to be where there is a disconnect.


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## steven4601 (Nov 11, 2010)

It is the same circuit !


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## DIYguy (Sep 18, 2008)

Geez, I went to bed and missed all the fun!

I have a suggestion. . . another practical one.  

Install on your bus (if you actually have it operational) or on any EV with a DC series wound motor, battery side conductors of a size 1/0 (size 0). Then install the same size conductor from the motor controller to the motor. Go for a drive up one of those mountains you talked about. If you get to the top and your vehicle is still functioning, get out, open the hood to see where the smoke is coming from. Now you can look frantically for the fire extinguisher.
After everything cools down, see if you can tell where the problem is rooted.


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## Tesseract (Sep 27, 2008)

bjfreeman: major is right; you are wrong; STFU.


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## DIYguy (Sep 18, 2008)

Tesseract said:


> bjfreeman: major is right; you are wrong; STFU.


I had to look up that acronym. Now I'm cracking up.


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## Tesseract (Sep 27, 2008)

Apropos, no?

Ok... less caustically, bj (though that's not really my style). Modern DC motor controllers are buck converters where the motor acts as both inductor and the load resistance.

Regardless of how you "think" (and I use that term very loosely here) they might work, the following rules always apply to a buck converter:

Power Out = Power In - Losses
Voltage Out ≤ Voltage In

Ergo,

Amperage Out ≥ Amperage In

The freewheeling diode provides a path for motor current to continue flowing when the switch is off. Really. No kidding.


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## EVfun (Mar 14, 2010)

DIYguy said:


> I had to look up that acronym. Now I'm cracking up.


Don't you mean LMAO?


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## bjfreeman (Dec 7, 2011)

DIYguy said:


> Geez, I went to bed and missed all the fun!
> 
> I have a suggestion. . . another practical one.
> 
> ...


I have a 250KW 3phase liquid cooled motor, currently hooked up to a 4 speed manual transmission.
I use 4/0 marine cable about 6 foot each run so it is about 24 feet from one post through the motor back to the other post. And I have about 12 feet total from Generator to the charger section. the connection from the charger to the battery to the convert are all in a case and use copper bus bars.
Batteries are 380 volts with a boost to 765 volts, through a 3phase inverter to the controller.
I have about as much instrumentation as a about 707, well that may be a stretch but as much as New ICE.
works fine. 
the 15 mile trip I take to dump tanks has some pretty steep and lengthy hills Semis have to down shift to negotiate. I pass them.
There is no hood, it is side mounted, not accessible without putting it on hoist.
However this thread started out the max size cable used for a ferrite hall effect sensor. It was not focused on dc or ac motors.
ask me if I care if you believe me.


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## bjfreeman (Dec 7, 2011)

Tesseract said:


> Apropos, no?
> 
> Ok... less caustically, bj (though that's not really my style). Modern DC motor controllers are buck converters where the motor acts as both inductor and the load resistance.
> 
> ...


I would call that a mechanics explanation because they don't know electrical laws.
BTW no one pointed out that the circuit used by major would blow Q1 if used in a real circult.


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## major (Apr 4, 2008)

bjfreeman said:


> I would call that a mechanics explanation because they don't know electrical laws.


Yet it was written by Tesseract who is the designer of motor controllers for EVnetics and most certainly knows the electrical laws better than anybody else on this board. His mechanic's explanation confirms what I told you over and over again starting back on post #25. You claim the motor current is not greater than battery current yet cannot provide a single valid reason or any support to your claim. You are mistaken.


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## bjfreeman (Dec 7, 2011)

major said:


> Yet it was written by Tesseract who is the designer of motor controllers for EVnetics and most certainly knows the electrical laws better than anybody else on this board. His mechanic's explanation confirms what I told you over and over again starting back on post #25. You claim the motor current is not greater than battery current yet cannot provide a single valid reason or any support to your claim. You are mistaken.


If you knew electrical theory you would know the problem.
however if Tesseract is an example of the knowledge level on this board, I can see why the blind is leading the blind.


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## steven4601 (Nov 11, 2010)

Best to stop feeding and lock this thread. 

The efforts are going up, but efficiency of this thread is dropping fast. 
The forum-user with the highest 'resistance' is quite obvious.


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## major (Apr 4, 2008)

bjfreeman said:


> If you knew electrical theory you would know the problem.
> however if Tesseract is an example of the knowledge level on this board, I can see why the blind is leading the blind.


I know electrical theory and I am sure Tesseract does also. All you have to do is tell us what part of that theory makes you believe that motor current cannot be greater than battery current as you claim. It is a simple request. Just tell us why what we know and what we see is false. You have claimed that my statement, and the same in different words by Tesseract, is "not correct". It is only fair and courteous for you to elaborate and support your position. What is the problem?


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## palmer_md (Jul 22, 2011)

steven4601 said:


> Best to stop feeding and lock this thread.
> 
> The efforts are going up, but efficiency of this thread is dropping fast.
> The forum-user with the highest 'resistance' is quite obvious.


I agree. I thought he might be here to learn, but based on the last few posts it seems he is here to troll.


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## major (Apr 4, 2008)

bjfreeman said:


> BTW no one pointed out that the circuit used by major would blow Q1 if used in a real circult.


Wait a minute. You insisted on talking about that circuit. 



bjfreeman said:


> Explain the diagrams red lines in the link that frodus gave.


So I copied it for you.



major said:


> You mean explain this:


Still you evade the real issue:



bjfreeman said:


> major said:
> 
> 
> > don't forget that motor current is always greater than battery current (except at zero and 100% PWM).
> ...


Explain how my statement violates Kirchhoff's law.


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## Gary B (Jun 2, 2011)

Tesseract said:


> Apropos, no?
> 
> Ok... less caustically, bj (though that's not really my style). Modern DC motor controllers are buck converters where the motor acts as both inductor and the load resistance.
> 
> ...


When i looked up the buck converter, i got a diagram where the inductive load got its PRIMARY current THROUGH the capacitor, and the freewheel current through the diode. - That does not agree with the diagram i have of EV motor current supply, which does NOT go THROUGH the the filter or ripple capacitors (other than very indirectly, through the power device, which must be ON to allow that). I would then say that the controller is not a buck converter. The ripple effect current has to pass through the primary current device, thus compensating somewhat for battery current supply. - Which is certainly good. - I would not expect the buck converter voltage and current calculations to be the same for the EV motor hookup or connection. - Perhaps I'm wrong. (?) - But that's my view. - Regarding motor and battery currents, i believe it's a matter of timing. At times, the filter (load leveling) capacitors are supplying part of the current. The current supply sharing between the battery and the capacitors depends on many things. - It is possible, i guess, for there to be some point in time where the capacitors were providing more current than the battery. (But not for long.) - Current doesn't come out of nowhere. - The capacitors get their charge (current) from the batteries in the long run. - Sure! - I have the right to be wrong too! - Best to you. Gary B.


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## rwaudio (May 22, 2008)

major said:


> I know electrical theory and I am sure Tesseract does also. All you have to do is tell us what part of that theory makes you believe that motor current cannot be greater than battery current as you claim. It is a simple request. Just tell us why what we know and what we see is false. You have claimed that my statement, and the same in different words by Tesseract, is "not correct". It is only fair and courteous for you to elaborate and support your position. What is the problem?


bj won't be able to back up his ramblings, they are all over this forum on all sorts of topics distracting from real information and possibly miss leading those that are here to learn. He tries to apply concepts in situations where they simply don't apply. I can't tell if he's trying to spread miss information on purpose or worse yet he thinks he's right and will blindly back it up with garbage. I would imagine that he can't be wrong on everything so I'm guessing there will be one valid concept/theory/formula/law that he will try to use to prove his point where it doesn't apply and is not valid.

This is not meant as an attack, but simply as a warning in general that when building an EV it is up to the builder to do their due diligence in finding what is right, what is wrong, what is safe and unsafe. Nobody should blindly take information from this forum or the internet in general blah blah, I know it's common sense but it doesn't hurt to remind those on the early part of the learning curve to be careful what you treat as fact.


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## major (Apr 4, 2008)

Gary B said:


> When i looked up the buck converter, i got a diagram where the inductive load got its PRIMARY current THROUGH the capacitor, and the freewheel current through the diode. - That does not agree with the diagram i have of EV motor current supply, which does NOT go THROUGH the the filter or ripple capacitors (other than very indirectly, through the power device, which must be ON to allow that). I would then say that the controller is not a buck converter. The ripple effect current has to pass through the primary current device, thus compensating somewhat for battery current supply. - Which is certainly good. - I would not expect the buck converter voltage and current calculations to be the same for the EV motor hookup or connection. - Perhaps I'm wrong. (?) - But that's my view. - Regarding motor and battery currents, i believe it's a matter of timing. At times, the filter (load leveling) capacitors are supplying part of the current. The current supply sharing between the battery and the capacitors depends on many things. - It is possible, i guess, for there to be some point in time where the capacitors were providing more current than the battery. (But not for long.) - Current doesn't come out of nowhere. - The capacitors get their charge (current) from the batteries in the long run. - Sure! - I have the right to be wrong too! - Best to you. Gary B.


Hi Gary,

http://www.diyelectriccar.com/forums/showthread.php?t=48006&highlight=buck In this thread Tess talks about capacitors in the controller in post #5.

major


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## Gary B (Jun 2, 2011)

major said:


> Hi Gary,
> 
> http://www.diyelectriccar.com/forums/showthread.php?t=48006&highlight=buck In this thread Tess talks about capacitors in the controller in post #5.
> 
> major


Your reference is (for me) the clearest explanation of what's going on and the most relevant to the current and cable sizing questions. It goes beyond the timing considerations to which i was referring. It also restates what Tess was trying to say in a way that makes more sense to "me". - 



major said:


> The controller has to be designed with the proper bus capacitor. Tess can tell you why. But once you have the proper capacitor design, the input current is set by the duty cycle of the PWM. These controllers are very efficient, so it is not far off to consider them 100%. Then the input power is equal to the output power. So if you have a 50% PWM and half voltage to the motor, then the battery current will be half of the motor current. Vb * Ib = Vm * Im.


Yes. - Power In=Power Out (or very close to that). It makes most sense to me in terms of a common transformer, where the same thing is true. (Vin * Iin = Vout * Iout). - Now. - Time moves on. - In these modern days, if an "electronic transformer" is termed a "Buck circuit or controller," that's fine with me. I'm caught up with some (very small portion) of terminology. (But the circuit itself is still quite different. The capacitor doesn't perform the same function.) - The bottom line for me is understanding better the relationship between the battery current and the motor current and how they can affect cable selection. - Much appreciated. - Gary B.


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## major (Apr 4, 2008)

Gary B said:


> Your reference is.......... - Much appreciated. - Gary B.


Thanks for the feedback.


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## bjfreeman (Dec 7, 2011)

Gary B said:


> The bottom line for me is understanding better the relationship between the battery current and the motor current and how they can affect cable selection. - Much appreciated. - Gary B.


http://www.diyelectriccar.com/forum...iption-use-fwd-68589.html?p=280620#post280620


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## major (Apr 4, 2008)

bjfreeman said:


> Though the Power semi provide this, a educated engineer will know he does not want spurious Current flowing through circuits when they can stop it..
> from a practical point of view, as you pointed out larger cable is necessary to accommodated this getting back to the controller.


So after all this you go to another thread to acknowledge that the motor current is greater than battery current


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## bjfreeman (Dec 7, 2011)

major said:


> So after all this you go to another thread to acknowledge that the motor current is greater than battery current


what started this is you post
http://www.diyelectriccar.com/forums/showpost.php?p=280132&postcount=23

I have been running the motor current limit as 840 amps while I limit the battery current to 420 amps (7C for my Li cells.) 
the you added
He runs 840 Amps through his 7.2 inch series motor,

this is not accurate 

I tried to get you see the error in this and you changing what you were talking about. Then when I tried to lead you down the logic you would change the subject fogging the topic.

What said, that you misinterpreted, is that the battery current is stored in the magnetic field then is release, when the battery current is not flowing, at a greater rate than the flow from the battery in a shorter time.
since time is key to amp the actually flow is the same using compensate time lines.

I also stated that the greater Current was generated by the motor, which is not in your definition and gives the inaccurate Idea there is more current than the battery supplied. when all it is, stored current from the battfery.


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## bjfreeman (Dec 7, 2011)

an finally if the motor had the FWD at the motor terminal, you would not see the larger current at the controller.


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## DIYguy (Sep 18, 2008)

bjfreeman said:


> with all that said, there is no one that has run a motor at 500-1,000 amp currently so controllers that hype that are just for impressing.


Check it out...... if I look harder, I can show you one with 1200 amps....
This CA is connected to a shunt and is calibrated. It shows peak current and minimum (sagged) voltage at that time..


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## major (Apr 4, 2008)

bjfreeman said:


> what started this is you post
> http://www.diyelectriccar.com/forums/showpost.php?p=280132&postcount=23
> 
> I have been running the motor current limit as 840 amps while I limit the battery current to 420 amps (7C for my Li cells.)
> ...


bj,

It is accurate. EVfun can measure it. I have measured similar cases. So has Tesseract and Plamsaboy. It is a fact that motor current is greater than battery current during PWM. It really does not matter at that point what is happening with fields in the motor. Outside the motor, in the cables, the current which will determine the heating of the wire and needs to be addressed for proper cable sizing, will be greater in the motor loop than the battery loop.

I have tried hard to keep that topic foremost here, and put up several posts solely to get us back on track.

Regards,

major


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## major (Apr 4, 2008)

bjfreeman said:


> an finally if the motor had the FWD at the motor terminal, you would not see the larger current at the controller.


Since all available controllers have the FWD contained within, you again acknowledge that motor current is greater than battery current. Thanks.


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## bjfreeman (Dec 7, 2011)

major said:


> bj,
> 
> It is accurate. EVfun can measure it. I have measured similar cases. So has Tesseract and Plamsaboy. It is a fact that motor current is greater than battery current during PWM. It really does not matter at that point what is happening with fields in the motor. Outside the motor, in the cables, the current which will determine the heating of the wire and needs to be addressed for proper cable sizing, will be greater in the motor loop than the battery loop.
> 
> ...


Nope don't have time to go around with you,


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## bjfreeman (Dec 7, 2011)

major said:


> Since all available controllers have the FWD contained within, you again acknowledge that motor current is greater than battery current. Thanks.


you take things out of context what about my previours post that explains it.
you keep showing you not going to change your view.
I am out of here.


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## DIYguy (Sep 18, 2008)

bjfreeman; said:


> I am out of here.


Aaaaaawwwwwe c'mon! I wanted you to comment on my meter pic! Is it an illusion??


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## bjfreeman (Dec 7, 2011)

DIYguy said:


> Aaaaaawwwwwe c'mon! I wanted you to comment on my meter pic! Is it an illusion??


did not see it till I say this post.
I have no way to validate.
so you have 1000 amp continuous?
if Not how long is this level maintained.?
if so what size cable do you use?


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## Roy Von Rogers (Mar 21, 2009)

bjfreeman said:


> Another thing I am trying to resolve.
> *4/0 awg says that 380 amp max*
> what size is being used for these controllers that state 500-1000 amp?
> At those currents, the cable would heat and would have power loss through voltage drop, not to mention possible insulation melting or catching on fire.
> ...


I'm not sure if anyone has mentioned this (havent read all of it yet)..

That figure is per 100ft.

Roy


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## DIYguy (Sep 18, 2008)

bjfreeman said:


> did not see it till I say this post.
> I have no way to validate.


Wow. Who, on this forum can validate anything. . . other than doing it themselves. A picture comes pretty close. More than i've seen from the other side of the proverbial fence.



bjfreeman said:


> you have 1000 amp continuous?


The Soliton! is capable of 1000 battery amps, 1000 motor amps. . continuous, with adequate water cooling. The hardware was designed by Tesseract . . (the fellow you slammed for not knowing what he was talking about.) He also designed the Jr. and the Shiva



bjfreeman said:


> Not how long is this level maintained.?


My shunt is in the battery circuit and therefore at 100% PWM, the motor current will be approximately the same (minus some inefficiency). It's not possible to maintain the 1000 amp level for very long as the motor spins up, BEMF will force it down. . . however, if I start out in say, 3rd gear, it will hold for more than a few seconds...
My 1000 amps pales in comparison to many racers who routinely draw 2000 amps per controller (some use 2 controllers in the same car)
Stick around for a few months and I will show you some 2500 to 3000 amp draws. 



bjfreeman said:


> so what size cable do you use?


My Calb Cells currently use the supplied interconnects. I use 2/0 for the longer jumpers on the battery side. I have a couple long runs which are 4/0 (overkill). . . but my motor cables are 4/0 and that is not overkill. The get quite warm when I am pushing it. 

For what it's worth, I did once build a system that had the same shunt and meter on both the battery and the motor circuits. It's very clear to see the difference in current from one to the other.


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## John Metric (Feb 26, 2009)

Here is a 2400amp battery draw (at 240V) and two parallel 2000amp motors currents(up to 170V)(shown as 4000amp total. We use 3/0 cable to the motors but are thinking about raising this to 4/0.










Metric


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## ga2500ev (Apr 20, 2008)

Looks like I missed all the fun. I read through the entire thread. I don't believe I saw a clear explanation of what is going on in terms of current multiplication. So just to humor myself, I'll take a crack at it.

I think we can all agree that a motor controller is a switching buck converter using the motor as the inductor in the system. There are numerous diagrams of this action in the thread.

The missing piece of the discussion is the following equation:

Power in (Pin) = Power out (Pout)

The power on both sides of the circuit are equal. 

The power equation (as shown here: http://en.wikipedia.org/wiki/Electric_power) is

P = IV (current times voltage)

So substituting:

Ibatt * Vbatt = Imotor * Vmotor

The basic argument has been the relationship of Ibatt and Imotor. Note they can only be equal if Vbatt and Vmotor are equal. This only happens at 100% PWM and the battery is essentially connected to the motor. At all other PWM values the buck function of the motor controller kicks in, the purpose of which is to reduce the motor voltage relative to the battery voltage. The reason that a motor controller works is that the motor's speed is linked to the voltage across it. So the PWM action of the motor controller creates an average motor voltage that is a fraction of the battery pack voltage. Because of this these equations are true:

Vbatt > Vmotor or Vbatt = Vmotor * k (k > 1)

So substituting using the second equation and solving for Imotor

Vmotor * k * Ibatt = Vmotor * Imotor

Vmotor * k * Ibatt / Vmotor = Imotor

k * Ibatt = Imotor

Since k > 1 (as specified in the beginning) Imotor is greater than Ibatt by some factor.

This the current multiplication that has been discussed in this thread.

I hope this helps...

ga2500ev


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## MPaulHolmes (Feb 23, 2008)

ga2500ev said:


> Power in (Pin) = Power out (Pout)
> 
> The power on both sides of the circuit are equal.


Exactly! 



ga2500ev said:


> Ibatt * Vbatt = Imotor * Vmotor


So, Ibatt = Imotor * Vmotor / Vbatt.

Vmotor/Vbatt is the pwm duty. So...

Ibatt = Imotor * pwm duty.


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