# DC motor theory and model



## Georgia Tech (Dec 5, 2008)

I am looking for software that takes Field pole turns, area, amrature slot count, # poles, Lam Stack length and gives back the constanse for Torque and RPM...


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## GerhardRP (Nov 17, 2009)

Georgia Tech said:


> I am looking for software that takes Field pole turns, area, amrature slot count, # poles, Lam Stack length and gives back the constanse for Torque and RPM...


I don't do that much. I start with measurements on a motor as built and then modify only field windings to get a modified form a DIYer could do. Also to compare motors particularly regarding magnetic losses.


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## GerhardRP (Nov 17, 2009)

I ran across this on another thread:

"You can look at some old Zilla Data capture plots 
I did with *Electrabishi* if it help the explanation
http://home.gci.net/~saintbernard/"

Unfortunately, on first look, I was not even close to the measurements...

Fortunately, the data includes a run at motor voltage=72, the value used on the Warfield dyno..The first attachment shows the two curves. Clearly these motors are different.

Next I evaluated the Electrabishi field map as shown in the second attachment. The solid line is my previous map multiplied by two, It appears that the Electrabishi motor has an armature with twice as many turns as the Warfield dyno'ed unit.

Can anyone shed any light on this matter? Did Netgain change the armature at some point, or is this a re-worked motor?

Gerhard


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## gor (Nov 25, 2009)

thank you, Gerhard

in your model, can you add torque to power/rpm?
2. can you add current curves to voltage curves on tq/rpm plot?
thank you


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## GerhardRP (Nov 17, 2009)

gor said:


> thank you, Gerhard
> 
> in your model, can you add torque to power/rpm?
> 2. can you add current curves to voltage curves on tq/rpm plot?
> thank you


I've added the curent curve as in your request 2. See post #1
I think the other plot would get too messy with torque added, partly because it is so closely related to current.

Gerhard


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## gor (Nov 25, 2009)

GerhardRP said:


> I've added the current curve as in your request 2. See post #1
> I think the other plot would get too messy with torque added, partly because it is so closely related to current.
> 
> Gerhard


thank you, Gerhard
so, on chart: WarP 9 Power vs RPM.pdf (61.0 KB) - if we put torque on the right-side vertical scale, torque curves will be about the same as current curves (1000A, 800A, 600A)?
may be add like: "1000A, 500Nm"?

(if plot it just to try and see if it worth it (or just to make sure where they are) - sometimes it's confusing how they all related) : ))))
preatty interesting - thanks again
something like on pictures attached, but how torque and power will look like on one chart (combined)...
http://www.uqm.com/propulsion_specs.php
http://www.uqm.com/pdfs/hitor%20spec%20sheet%209.22.09.pdfhttp://www.uqm.com/pdfs/PowerPhase 100.pdf


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## GerhardRP (Nov 17, 2009)

gor said:


> thank you, Gerhard
> so, on chart: WarP 9 Power vs RPM.pdf (61.0 KB) - if we put torque on the right-side vertical scale, torque curves will be about the same as current curves (1000A, 800A, 600A)?
> may be add like: "1000A, 500Nm"?


I have noted the nominal torque value for each current line in power vs. RPM. 



> (if plot it just to try and see if it worth it (or just to make sure where they are) - sometimes it's confusing how they all related) : ))))
> pretty interesting - thanks again
> something like on pictures attached, but how torque and power will look like on one chart (combined)...


Torque and power are linearly related... Power = Torque x Speed. Lines of constant torque vs. RPM are straight lines from the origin. 
The charts you show are efficiency maps...cool. Do you have a link to the source for those curves.
Gerhard


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## gor (Nov 25, 2009)

post with charts updated (links)
p.s.well, one version could be bit messy - just to make sure all curves are where you think it should be - while other wersions - clean and easy to read 
(and that's how we can see what layouts works better than the other ....)

thanks 4 update, Gerhard - looks pretty good - informative and intuitive - beautifull 







that's the beauty 
G., with and w/o efficiency curve, pleeeese


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## gor (Nov 25, 2009)

Gerhard, how Tq, Power and RPM curves would look on current and voltage(xy) scale?


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## GerhardRP (Nov 17, 2009)

Added Torque vs. RPM chart to Post #1.
Gerhard


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## gor (Nov 25, 2009)

GerhardRP said:


> Added Torque vs. RPM chart to Post #1.
> Gerhard


gorgeous
reminds hydraulic motors charts
now we have everything- from any point of view : ))))
Gerhard, can you put rpm on Volts(x) Amps axis?
would be great - plain simple: volts increasing(x) - Rpm goes... amps incr/decr -rpm (and torque) curve goes such and such...


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## maxvtol (Nov 11, 2009)

Is there any chart comparable to what the Thunderstruck AC50 has, similar to a conventional ICE chart? I've included a chart below from the source here . I've included battery amps and efficiency. 

I've never seen a Warp 9 or ADC motor chart that shows efficiency below 2158 rpm, so what is the efficiency of a DC motor at lower rpms, is it still in the 85%+ range? And I assume the efficiencies in a DC chart don't include the controller, so how can you compare?

My thinking is that if a DC motor has a higher efficiency from 0 to 2500rpm where the AC motor is low, this may compensate for the regen of the AC motor, ie from 0 to 15 or 20mph where the acceleration and the amps are the highest the DC is more efficient. Both AC and DC seem to be very efficient in the mid range. 

The Wh/mile in the EVAlbum for the AC motors don't seem to be dramatically better than the DC motors. Other than the brush maintenance, I think I'm finding the DC a better solution for my EV project.


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## major (Apr 4, 2008)

maxvtol said:


> Is there any chart comparable to what the Thunderstruck AC50 has, similar to a conventional ICE chart? I've included a chart below from the source here . I've included battery amps and efficiency.
> 
> I've never seen a Warp 9 or ADC motor chart that shows efficiency below 2158 rpm, so what is the efficiency of a DC motor at lower rpms, is it still in the 85%+ range? And I assume the efficiencies in a DC chart don't include the controller, so how can you compare?
> 
> ...


Hi max,

Here is another one. If you study it you can see that low speed efficiency takes a dive at maximum torque output. And the curve you show is just that, max output. I suspect you would see a marked increase in motor/control efficiency if you just went to 90% torque at the lower RPM. But all motors, AC and DC are going to be 0% efficient at 0 RPM. So the DC motor efficiency will taper off as speed decreases also. You are hard pressed to find accurate information on this. 

Which is better, AC or DC? It wouldn't surprise me if they were about the same. And how often and how long do you operate the motor at low RPM and high loads? And low RPM, even at high torque, is not going to command high power. So losses due to a few efficiency points difference may equate to a small amount of power for a short time, meaning not much energy wasted.

AC vs DC? Your choice. Low speed efficiency at maximum output may be a poor metric on which to base your choice, especially with the lack of good data on the available motor/controller products.

Regards,

major


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## maxvtol (Nov 11, 2009)

Thanks major,


major said:


> Here is another one. If you study it you can see that low speed efficiency takes a dive at maximum torque output.


That's still a AC motor curve. I was hoping for DC efficiency at low rpm. But if the efficiency curves vs rpm are similar, that answers my question. I just wonder why you can't seem to find a chart with efficiency at the lower rpms for a DC motor. 



major said:


> And how often and how long do you operate the motor at low RPM and high loads? And low RPM, even at high torque, is not going to command high power. So losses due to a few efficiency points difference may equate to a small amount of power for a short time, meaning not much energy wasted.


 So for a 100 v pack and acceleration pulling 300 amps, wouldn't that pull out 30kw from the batteries for the accel period? The charts I've seen have more current drawn on startup for city driving (which mine will be mostly), so over 20+ stops/starts for my typical trip, the "area under the curve" for watts vs time could be significant for the acceleration. So if somehow the DC was more efficient during acceleration, even a small increase could make some difference, say enough to be as efficient as an AC with regen? That's what I was hoping to find out.


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## major (Apr 4, 2008)

maxvtol said:


> So for a 100 v pack and acceleration pulling 300 amps, wouldn't that pull out 30kw from the batteries for the accel period? The charts I've seen have more current drawn on startup for city driving (which mine will be mostly), so over 20+ stops/starts for my typical trip, the "area under the curve" for watts vs time could be significant for the acceleration. So if somehow the DC was more efficient during acceleration, even a small increase could make some difference, say enough to be as efficient as an AC with regen? That's what I was hoping to find out.


Hi max,

You may be looking at motor current, which will be high at high torque regardless of RPM. But battery current will be lower than motor current at lower RPM because the motor voltage is lower than battery voltage. The controller is acting similar to a transformer giving you current multiplication at reduced voltage output. Motor performance curves alone will not show this.

If the mission for your EV has this much low speed (mph) and high torque (fast acceleration) requirement, maybe you need to consider a multi-ratio transmission. Also, that many stops may mean that you can benefit from regeneration more than most. Regeneration is not going to show up as efficiency on any of the curves you're looking at. And probably not in these Whr/mile figures posted for existing EVs. It is probably unwise to count on regeneration for any significant increase in available range using lead-acid batteries. I'm unsure about Lithium batteries as I've never tried it. But I can tell you regeneration is a nice feature. I like it. 

Regards,

major


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## GerhardRP (Nov 17, 2009)

major said:


> Hi max,
> <snip>
> AC vs DC? Your choice. Low speed efficiency at maximum output may be a poor metric on which to base your choice, especially with the lack of good data on the available motor/controller products.


I am modelling the Warp 9 motor, but unfortunately at low RPM the losses are dominated by copper losses and I don't trust the resistances I estimated from Netgain's dyno curves. If you know accurate numbers for the armature and field resistances, I will draw a good low RPM high current efficiency map.
Thanks,
Gerhard


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## major (Apr 4, 2008)

GerhardRP said:


> .........Warp 9 motor.......... If you know accurate numbers for the armature and field resistances.......


Sorry, don't have those numbers. I had one of these motors here for a few months, but don't have a Wheatstone bridge. Even then you still have the pesky problem of brush voltage drop. 

Regards,

major


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## maxvtol (Nov 11, 2009)

major said:


> Motor performance curves alone will not show this.


Thanks major,
With my mechanical engineering background, I guess I'm just trying to compare AC and DC with apples and oranges data, and need to brush up on my electrical basics. 

I love the idea of regen, but my little donor car (still ICE at the moment) is so much fun to drive, I think I'm going to have to go DC to keep the performance and stay within budget. I was just trying to justify DC in my mind, when like you said there's probably not that much difference.


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## maxvtol (Nov 11, 2009)

major said:


> You may be looking at motor current, which will be high at high torque regardless of RPM. But battery current will be lower than motor current at lower RPM because the motor voltage is lower than battery voltage. The controller is acting similar to a transformer giving you current multiplication at reduced voltage output. Motor performance curves alone will not show this.


OK, just jumped on my e-bike and under hard acceleration, the amps on the battery maxes out (like I thought on my earlier question), but of course at steady speed is very low at low rpm like you say. 

I guess my earlier question should have been does a DC motor/system accelerate more efficiently than an AC motor/system. I guess my error was trying to look at steady state chart data to try to figure this out.


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## major (Apr 4, 2008)

Hi max,

Maybe we shouldn't hijack Gerhard's thread 



maxvtol said:


> OK, just jumped on my e-bike and under hard acceleration, the amps on the battery maxes out (like I thought on my earlier question), but of course at steady speed is very low at low rpm like you say.


Beware using an e-bike system to draw conclusions about a high powered EV motor/controller. I've seen such systems where full voltage is used for acceleration due to the resistance in the small motor and battery. And therefore there is no current multiplication.



> I guess my earlier question should have been does a DC motor/system accelerate more efficiently than an AC motor/system. I guess my error was trying to look at steady state chart data to try to figure this out.


The data points from the steady state curve will certainly apply to the infinitesimal points on the dynamic curve, allowing for the torque applied to the rotor inertia. So if the steady state curves for the AC and DC were of similar efficiency and the rotor sizes the same, acceleration efficiency would be similar. The acceleration profile may differ between the AC and DC motor due to the shape of the RPM vs torque curve. 

This is demonstrated in the example of post #25 in this thread http://www.diyelectriccar.com/forums/showthread.php/torque-irrelevant-relevanti-36904p3.html Later in the thread it was calculated that the vehicle with lower power which won the race actually used less energy for the same distance covered at the same GVW. The examples there used motor output profiles and therefore did not look at motor efficiency. I'm not sure you can say that the torque-speed profile of the motor affects the acceleration efficiency, but it looks like it can influence the Whr/m.

Regards,

major


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## maxvtol (Nov 11, 2009)

major said:


> Maybe we shouldn't hijack Gerhard's thread


Agreed, Gerhard does have some nice graphs that I hoped would point to my answer. I was just hoping someone could help me find it. 

I'll just leave it with this simple question:
All things being exactly equal (mass, gearing, resistance, battery volts, etc) to accelerate the vehicle to 20mph in 2 seconds, which would take fewer watthrs out of the battery pack, an AC50 motor from Thunderstruck or a Warp 9 motor from Netgain?

I don't want to take Gerhards thread off tangent, but if if someone had real data, suportable theory or real world experience that could answer that, I would appreciate it.


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## major (Apr 4, 2008)

maxvtol said:


> All things being exactly equal (mass, gearing, resistance, battery volts, etc) to accelerate the vehicle to 20mph in 2 seconds, which would take fewer watthrs out of the battery pack, an AC50 motor from Thunderstruck or a Warp 9 motor from Netgain?


"All things being exactly equal", is telling me the energy would also be equal. It might be that you would be hard pressed to measure the difference. 

But I doubt that any here would argue that the Warp9 with a good controller will blow the doors off the AC50 in a drag race. So using the Warp9 in your "equal" example is probably running it well under its peak, so it may in fact be more efficient than the AC50.

major


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## Dennis (Feb 25, 2008)

I think you should do your graphs the way GE does their series wound traction motors/drill motors here: http://www.getransportation.com/na/en/docs/1136706_1243949620_series wound.pdf. It's up to you though. Just a suggestion.


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## Tesseract (Sep 27, 2008)

Hey major... I'm going to help this guy out and get him some data.

I'd appreciate your comments on how I might best do that given the limitations of my dyno setup:

* - gear-pump dyno that is useless above 3500 rpm but can go down quite a bit lower in RPM than, saw, a water brake dyno (not sure how low, but I know I can't do stall torque testing at more than 200A or so)

* - 240V/105Ah AGM pack that has been... uh... well-abused. I routinely pull 700A from it but it has long since lost the ability to deliver 1000A without the voltage sagging into the dirt.

* - the Soliton1 is, of course, a buck converter configured as a constant current source (0-1000A) but the Warfield data plots seem to be based on operating the motor with a constant voltage source (ie - fixed at 72V then vary the shaft loading to plot RPM vs. torque). Question: would simply limiting the motor voltage output in the Soliton1 to 72V (with the pack at 240V) and cranking the throttle to max be sufficient to duplicate at least some of the Warfield data, or will I need Qer to make a special version of the code that will allow me to "idle" the motor at a constant speed (the ability to idle the motor at a constant speed is in the controller code now, but it is limited for safety reasons to allow no more than 300A to the motor with an RPM range of 500-1500 RPM).

What I am getting at is that in order to validate a testing method - whatever it may be - we first need to see that any data acquired with a my dyno setup at least nominally agrees with what Warfield states when tested using their method and dyno setup (constant voltage, which is kinda goofy for an EV, but, well...).


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> Hey major... I'm going to help this guy out and get him some data.
> 
> I'd appreciate your comments on how I might best do that given the limitations of my dyno setup:
> <snip>
> What I am getting at is that in order to validate a testing method - whatever it may be - we first need to see that any data acquired with a my dyno setup at least nominally agrees with what Warfield states when tested using their method and dyno setup (constant voltage, which is kinda goofy for an EV, but, well...).


Hi Guys,
Let me clarify something: My approach centers on the field map, so every single measurement will produce a point on the field vs. ampere-turn curve. ANY data will be tested against the Warfield values even if taken in a vastly different way.
Now the weaknesses of the Warfield data is in the low voltage and low speed region. If you can set your idle to 500 RPM and then scan from unloaded to max torque that would be wonderful. Be sure to record armature and field voltages separately. This should give a good measure of copper and brush losses. If you can measure temperature that would be cool.
Gerhard

PS If you have a data file of some random measurements, I can start there. g.


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## major (Apr 4, 2008)

Tesseract said:


> Hey major... I'd appreciate your comments on how I might best do that given the limitations of my dyno setup:


HI Tess,

I suggest you do it the way we used to in the old days. We were using water cooled eddy current brakes for the load and very large Sorenson power supplies, multiple 20V,1000A jobs, which were well filtered and regulated.

We would take the data for the normal DC motor performance curve point by point. Typically using current set points like 50,150,200, 250,... Amps while maintaining the proper motor voltage for each current point. I guess in your case, just keep motor terminal voltage at 72 volts. And the low current points may be at too high an RPM for you.

So to get the 200A point for example, set the motor voltage to 72 and adjust the load (shaft torque) until you get the 200 amp draw (motor current). Readjust power supply to get as close to 72V and 200A as possible. Read the torque and RPM from the dyno. You got your point.

I'd strive harder to maintain the 72V and not worry so much about the exact current value. So what if it is 214A. Just record the actual value for the torque and RPM you read. You will eventually take the data and draw a speed torque curve from it anyway.

Repeat this procedure for as many current values as reasonable over your range of interest. If you are testing for the "cold" performance curve, you need to take the points rather quickly and let the motor cool down inbetween points. Cold performance characteristic curves are handy to verify motors at the end of the production line and such. But "warm" performance curves are more indicative of the actual behavior in the application. We would do it both ways.

For the warm performance we typically used 120 degrees rise on the winding temperature. This involved running the motor at the rated load until thermally stable. Then we would deviate from the load for the "performance point" and return to the rated load and let temperature level out again. Then to the next point, and so on.

As you can see, to get a true valid characterization of motor performance, it would be days, maybe weeks in the lab. I forgot to mention that all testing was done with 80% minimum brush seating. And in each direction for reversible motors.

Anyway, just keep the motor voltage constant, adjust load, read the current, torque and RPM for a series of load points and you should have it.

Keep track of the temperature. It may be interesting, but the field voltage Gerhard asked for isn't going to tell you much about field resistance because of the PWM.

Give it a shot and plot it back against torque and see how it looks.

Regards,

major


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## major (Apr 4, 2008)

GerhardRP said:


> ANY data will be tested against the Warfield values even if taken in a vastly different way.


What are Warfield values?


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## GerhardRP (Nov 17, 2009)

major said:


> What are Warfield values?


The points on the first graph on post#1 of this thread are the data posted on the go-ev [Netgain] site. The lines there are my model.
Gerhard


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## major (Apr 4, 2008)

GerhardRP said:


> The points on the first graph on post#1 of this thread are the data posted on the go-ev [Netgain] site. The lines there are my model.
> Gerhard


Sorry Gerhard,

I don't follow. What is the source of the data? Is it this http://www.go-ev.com/images/003_15_WarP_9_Graph.jpg This curve doesn't even agree with itself. I would not consider it a good starting point for a detailed analysis. I'll bet Tesseract can develop a better performance curve with his equipment. Let's see what he comes up with.

Regards,

major


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## GerhardRP (Nov 17, 2009)

major said:


> Sorry Gerhard,
> 
> I don't follow. What is the source of the data? Is it this http://www.go-ev.com/images/003_15_WarP_9_Graph.jpg This curve doesn't even agree with itself. I would not consider it a good starting point for a detailed analysis. I'll bet Tesseract can develop a better performance curve with his equipment. Let's see what he comes up with.
> 
> ...


I used the tabular data also posted there.
What do you mean about the lack of internal agreement?
Gerhard


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## major (Apr 4, 2008)

GerhardRP said:


> What do you mean about the lack of internal agreement?


Hi Gerhard,

http://www.diyelectriccar.com/forums/showthread.php?p=153021#post153021 see post #868.

Also I have a hard time taking a graph seriously which uses Ft/Lbs as units for the x-axis 

And you ran into a discrepancy compared to Mike's data on post #4 in this thread. I think it wise to have Tess run a dynamometer curve at 72V and see just how accurate the published data is for the motor.

major


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## GerhardRP (Nov 17, 2009)

major said:


> Hi Gerhard,
> 
> http://www.diyelectriccar.com/forums/showthread.php?p=153021#post153021 see post #868.
> 
> ...


The post you quote makes it clear that The real Warp 9 is like the Electrabishi and not the one touted by Netgain... Should we charge them with false advertising? The curves are off by a factor of two!
I eagerly await new data... again, random points are as useful as a carefully constructed curve...I can extract the field map and loss factors from wide ranging random values, and then draw whatever curves are usefull.
Gerhard


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## Dennis (Feb 25, 2008)

> The post you quote makes it clear that The real Warp 9 is like the Electrabishi and not the one touted by Netgain... Should we charge them with false advertising? The curves are off by a factor of two!
> I eagerly await new data... again, random points are as useful as a carefully constructed curve...I can extract the field map and loss factors from wide ranging random values, and then draw whatever curves are usefull.
> Gerhard


Or you could have some wrong data. Did you account for armature reaction, armature and series field resistance, brush contact resistance, brush resistance, wire cable resistance, saturation of the iron, and does your formulas also take into account the back EMF of the armature? The actual voltage that runs DC motors is the difference between supply and armature voltage. 

In all honesty your best approach to this is to get someone to test the motor with a stable supply voltage under varying current and stable temperature environment with the motor ran for about 20 minutes at full load. Then start taking different data points from different loads applied to the motor. After you get a curve going, plug this data into Math Cad which can then actually give you the formula of the curve. 

Motor design or reverse engineering the parameters of one is very difficult. In fact Electromagnetic Design Engineers do not design electric motors using the paper and pencil method, but instead use insanely expensive design/simulation software such as ANSOFT and Infolytica.


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## major (Apr 4, 2008)

Dennis said:


> .......Electromagnetic Design Engineers do not design electric motors using the paper and pencil method,..........


They used to


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## piotrsko (Dec 9, 2007)

major said:


> They used to


I for one think they used to do a better job, too.


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## Tesseract (Sep 27, 2008)

Here's some data on the WarP 9:

Field Resistance: 3.53mΩ (106.0mV drop at 30.0A constant current)
Field Inductance: 9.6uH (which seems low... might need to confirm with another test method)


Armature Voltage vs. RPM at a constant Field Current (separately excited)

```
25A         35A
1000      4.40V     5.65V
1500      6.50V     8.40V
2000      8.64V    11.05V
2500    11.00V    13.80V
3000    13.08V    16.40V
```


My understanding is that you need this data to determine "K". Regardless, I need it to determine the algorithm for regen in the Soliton1 


Constant 72V dyno testing

```
[FONT=Courier New]RPM     Current   Dyno HP  Loading  Input HP      Eff.
2770     290A      15.1      0        28.0        54%
2686     305A      17.1      1        29.4        58%
2571     326A      21.1      2        31.5        67%
2465     350A      24.7      3        33.8        73%
2168     445A      33.5      4        42.9        78%
1565     870A      64.1      5        81.6        79%
[/FONT]
```

Power input (Input HP) refers to the actual electrical power consumed by the motor while Dyno HP is the calculated output power including motor, and dyno losses (with unknown proportioning between the two).


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> Here's some data on the WarP 9:
> 
> 
> Constant 72V dyno testing
> ...


Thanks.. I extracted the field map from Electrabishi's acceleration curves [actually just current, voltage and RPM] The attached plot shows your data on top of the 72 volt curve generated from my fit..NO adjustments were made. Also, the Warfield "data".


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> Thanks.. I extracted the field map from Electrabishi's acceleration curves [actually just current, voltage and RPM] The attached plot shows your data on top of the 72 volt curve generated from my fit..NO adjustments were made. Also, the Warfield "data".


Hey - I didn't get a chance to test at full load on the dyno because my pack was starting to die. I connected up FrankenCharger® while I went to lunch and did some other stuff at the shop and got enough juice back into it for at full dyno load.

Note that in this last test the actual voltage measured at the motor terminals was 69V, and so there is 3V of drop in the 2/0 cables between the controller and the motor. 870A will do that, I guess.

Anyway, looks like there is excellent agreement between electrabishi and me; not so much with Warfield... That's just shocking, I tell you!


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> Anyway, looks like there is excellent agreement between electrabishi and me; not so much with Warfield... That's just shocking, I tell you!


The last point is fine too.. I'll use your other measurements to nail down the low current field.


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> Here's some data on the WarP 9:
> 
> Field Resistance: 3.53mΩ (106.0mV drop at 30.0A constant current)
> Field Inductance: 9.6uH (which seems low... might need to confirm with another test method)
> ...


From the Electrabishi data, I got a total resistance of 7.1mΩ.
Is this data no load, driven by the quoted voltage? If so, I would like to see the same thing at high field current with the armature current reported also. What that would be is a dyno curve at zero net torque and what we get out is the iron losses and maybe the brush losses too.


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> From the Electrabishi data, I got a total resistance of 7.1mΩ.


Keep in mind that it is very difficult to measure extremely low resistances correctly. You have to use Kelvin's technique and a precisely known current. In this case, I used clamps to attach a 30A constant current source to the field terminals then measured the voltage drop across the field by touching my DMM to the top of the studs, outside of the high current loop. I'm pretty sure my reading is accurate.

Now, the field resistance does include any welds, etc., so there will be some variation in resistance - even as much as a few milliohms, even though that might be a 100% or more difference.




GerhardRP said:


> Is this data no load, driven by the quoted voltage?


No - the armature voltage data is the open circuit voltage produced at the specified RPM and constant field current.




GerhardRP said:


> If so, I would like to see the same thing at high field current with the armature current reported also. What that would be is a dyno curve at zero net torque and what we get out is the iron losses and maybe the brush losses too.


That's going to be a tough one as it requires a 0.3V to 0.4V and 100A power supply...

I do have a 200A constant current sink that I could feed with one of these 200Ah LFP cells we have here... that will require a bit of kludging on my part and I don't quite see the merit in such... but if there is any then I'll consider it.


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## GerhardRP (Nov 17, 2009)

The Electrabishi Zilla dump shows motor voltage at 1000 amps at launch where there is virtually no back emf.. gives total resistance..field plus armature plus brush.
The hardest thing to get at in the model is iron loss.. that's why I want the zero net torque measurement.
You could run the test fields in series with another motor loaded with your dyno.
Gerhard


----------



## Tesseract (Sep 27, 2008)

GerhardRP said:


> The Electrabishi Zilla dump shows motor voltage at 1000 amps at launch where there is virtually no back emf.. gives total resistance..field plus armature plus brush.


My dyno can't stall the motor if the current is above 200A or so, even at full load. While I could possibly obtain this data with an actual vehicle, I won't because abruptly lamming one of these WarP motors with 1000A tends to break parts of the drivetrain (we know this for a fact already - aren't anxious to repeat the experience).




GerhardRP said:


> The hardest thing to get at in the model is iron loss.. that's why I want the zero net torque measurement.


Iron losses depend on the PWM frequency, and while this is valuable data, it will also be very time consuming to determine (must measure the rate of temperature rise from a consistent starting temperature at different PWM frequencies...)




GerhardRP said:


> You could run the test fields in series with another motor loaded with your dyno.


You mean duplicate the test as before except wire the second motor's field, only, in series with the first motor? Hmmm... Sure, I could do that. The Soliton1 wasn't designed to be a "lab grade" constant current source, but it can regulate motor current with better than 0.5% stability so this is not an unreasonable task for it.


----------



## GerhardRP (Nov 17, 2009)

Tesseract said:


> Iron losses depend on the PWM frequency, and while this is valuable data, it will also be very time consuming to determine (must measure the rate of temperature rise from a consistent starting temperature at different PWM frequencies...)


Actually, I am talking about the iron losses associated with the armature rotating in the spacially fixed field of the motor. The PWM losses look like resistance to me.


Tesseract said:


> You mean duplicate the test as before except wire the second motor's field, only, in series with the first motor? Hmmm... Sure, I could do that. The Soliton1 wasn't designed to be a "lab grade" constant current source, but it can regulate motor current with better than 0.5% stability so this is not an unreasonable task for i


Not quite the same test.. The Warp 9 should be driven to speed with current it its own armature. I emphasize again that you don't need to regulate anything, just measure it all..field and armature currents and armature voltage and RPM. 
The electrabishi 72 volt plot I showed came from a third gear time series data dump... taken by eye from the graphs.
Gerhard


----------



## Dennis (Feb 25, 2008)

> > Originally Posted by *Dennis*
> > _ .......Electromagnetic Design Engineers do not design electric motors using the paper and pencil method,...._
> 
> 
> They used to


I am surprised at what we could do before calculators and computers came along. Imagine trying to find the 200th root of 555 for example. To be able to solve such a problem with paper and pencil definitely took someone who was dedicated for sure! Today lots a math majors do not even know how to find the sine, cosine, tangent, e, or roots of numbers without calculators.


----------



## GerhardRP (Nov 17, 2009)

Dennis said:


> I am surprised at what we could do before calculators and computers came along. Imagine trying to find the 200th root of 555 for example. To be able to solve such a problem with paper and pencil definitely took someone who was dedicated for sure! Today lots a math majors do not even know how to find the sine, cosine, tangent, e, or roots of numbers without calculators.


I predated computers so I would use my log tables tables:
The answer is antilog(log(555)/200).
Gerhard


----------



## GerhardRP (Nov 17, 2009)

I'm starting to work on my Kostov 11" motor model. I'll start with the 250 volt version.
http://kostov-motors.com/files/productattachments/64518679c80c77a2cde788dbab802c16_F08A7.pdf
http://kostov-motors.com/files/productattachments/04a1d5e7278db48475f2aa409b5df5ce_S192F01.1.pdf
I wonder if someone with that motor can provide one data point: Connect a 12 battery to an unloaded motor and report the Voltage, RPM and current. That will tie down the field map at zero current.


----------



## zwmaster (Nov 23, 2009)

GerhardRP said:


> I'm starting to work on my Kostov 11" motor model. I'll start with the 250 volt version.
> http://kostov-motors.com/files/productattachments/64518679c80c77a2cde788dbab802c16_F08A7.pdf
> http://kostov-motors.com/files/productattachments/04a1d5e7278db48475f2aa409b5df5ce_S192F01.1.pdf
> I wonder if someone with that motor can provide one data point: Connect a 12 battery to an unloaded motor and report the Voltage, RPM and current. That will tie down the field map at zero current.


I have made some preliminary setup just to measure data you need.
Measurements were done in SERIES FIELD MODE and PARALLEL FIELD MODE.

test setup








SERIES FIELD MODE:








Voltage 11.80V
Current 26.84A cold, 25.84A warm
Speed 25.5 1/s (1530 1/min) cold, 26.2 1/s (1572 1/min) warm









PARALLEL FIELD MODE:








Voltage 11.80V
Current 24.02A 
Speed 25.66 1/s (1540 1/min)









Temperature cca. 5degC

I hope it is what you need.


----------



## GerhardRP (Nov 17, 2009)

zwmaster said:


> I have made some preliminary setup just to measure data you need.
> Measurements were done in SERIES FIELD MODE and PARALLEL FIELD MODE.
> 
> <snip>
> ...


Fantastic!
Gerhard


----------



## Tesseract (Sep 27, 2008)

GerhardRP said:


> Fantastic!
> Gerhard


Hold on there, Gerhard... why is there virtually no difference in current and RPM between connecting the fields in series vs. parallel???


----------



## GerhardRP (Nov 17, 2009)

Tesseract said:


> Hold on there, Gerhard... why is there virtually no difference in current and RPM between connecting the fields in series vs. parallel???


 The "real" answer will have to wait until I enter the data from the published curves, but I think the motor is running on the residual field.
Gerhard


----------



## Tesseract (Sep 27, 2008)

GerhardRP said:


> ...I think the motor is running on the residual field.


Hmmm... or maybe it's just like the magnetizing current in a transformer - a certain amount of primary current flows even when the secondary is totally unloaded? Of course, in a motor there is always some load - from windage and bearing friction - but I'd guess that would only amount to a few watts or tens of watts at most.

It would be nice to be able to predict the stall torque of the motor, but what RPM it will reach when fully unloaded seems to be less useful


----------



## major (Apr 4, 2008)

Tesseract said:


> Hold on there, Gerhard... why is there virtually no difference in current and RPM between connecting the fields in series vs. parallel???


Yeah, Tess,

That doesn't make much sense. Even residual doesn't explain it in my mind. You get a current spike when you connect the motor to accelerate it even with no load. That will take you up the sat curve and then when it settles back to 25A, the steel will be worked on a descending air gap line of the magnetization characteristic hysteresis. But an excitation of a couple hundred AT/p (parallel connected) will cause more flux than zero and a couple hundred more AT/p (series connected) will certainly yield more flux. It should show up as different RPM and/or different current draw.

I thought perhaps zw had wired the fields such that they were bucking or canceling out and it was running on residual only. But he posted nice pictures of his set-up and it checks out with Kostov's connection notes.

Then I wonder if his frequency counter is picking up some noise or something to give him a false reading.

And at no load, the largest internal load will be brush friction which will likely be 100s of watts at 1 to 2000 RPM.

Kind of a mystery to me. Must be those darn interpoles 

major


----------



## zwmaster (Nov 23, 2009)

You’re all right.
It’s puzzling to me too. The data is not near what I have expected.
I was hoping someone could give some more idea.
major 
Since I received the motor I was not sure about connections.
Imprints on the holder plastic are saying like marked on the pictures.
D1 and D2 are “short” so this should be one winding.
D3 and D4 also.
A2 and A1 (shouldn’t this be B1?) are connected to brushes. 
Plamen how can we determine winding direction of the coils? 
Where is the coil start (dot on the coil symbol)?
It was cold yesterday so I didn’t bring oscilloscope to the garage.
I will try to do it today. The circuit has filter build in and the signal is relay clean as it was used before.

From what it should be simple test, I now have more questions than answers.
zw.


----------



## GerhardRP (Nov 17, 2009)

zwmaster said:


> You’re all right.
> It’s puzzling to me too. The data is not near what I have expected.
> I was hoping someone could give some more idea.
> <snip>
> ...


Hey zw, do me another favor... Reverse your battery connections only. Repeat the measurements, parallel first then series. The speed should drop maybe 30 RPM for each step.
We're dealing with hysteresis here. It appears that when the fields were last connected to a high current source, they were reversed from your original hookup. I'll post graphs as soon as I see the new data.
grp.


----------



## zwmaster (Nov 23, 2009)

Here are values with switched + and -.
Parallel mode
25.6A
11.5V
Series mode
25,9A
9.4V

Speed is always around 1560 RPM







Signal is clean (it's hard to make snapshot of whole signal...did not study the camera setup). Timebase was set to 10ms per div.

Battery died on the end.


----------



## major (Apr 4, 2008)

zwmaster said:


> Here are values with switched + and -.
> Parallel mode
> 25.6A
> 11.5V
> ...


Hi zw,

This makes me suspect the speed readings even more  As the battery dies and the voltage decreases, are you able to tell if the motor is slowing by sight or sound? 

Got a handheld tach or strobe?

major


----------



## zwmaster (Nov 23, 2009)

major said:


> Hi zw,
> 
> This makes me suspect the speed readings even more  As the battery dies and the voltage decreases, are you able to tell if the motor is slowing by sight or sound?
> 
> ...


Yes speed did fall down to 1380 then I stopped. I actually heard the battery is dieing (was playing with osc. too long) and then checked frequency and voltage.
It could be optical sensor that's the blame. The signal is to clear to not believe it.... 
I had a better sensor but have to find it first.
Wait for results with new sensor (I don’t have strobe).
zw


----------



## zwmaster (Nov 23, 2009)

Here are new data:
SERIES
U = 11.95 V
I = 26.3 A
f = 26.3 Hz -> 1578 min-1
PARALLEL
U = 11.95 V
I = 24.3 A
F = 25.6 Hz -> 1536 min-1

I used another optical sensor and double checked with tacho (it indicated 94.7-94.9V k=0.06V/min-1) and inductive pickup.
All sensors are showing the same in minimum tolerances.


----------



## major (Apr 4, 2008)

zwmaster said:


> Here are new data:
> SERIES
> U = 11.95 V
> I = 26.3 A
> ...


O.K. zw,

How about confirming the fields are not bucking? To do this, just run with half the field, like disconnect D3 and D4. This should give you the same ampere-turns as the parallel connection but twice the field resistance.

Hope that shows something different.

major


----------



## GerhardRP (Nov 17, 2009)

major said:


> Hi zw,
> 
> This makes me suspect the speed readings even more  As the battery dies and the voltage decreases, are you able to tell if the motor is slowing by sight or sound?
> 
> ...


Trust the measurements.. You are working on a minor hysteresis loop as indicated in the attached sketch


----------



## major (Apr 4, 2008)

GerhardRP said:


> Trust the measurements.. You are working on a minor hysteresis loop as indicated in the attached sketch


Hi Gerhard,

Here is a better diagram. See attachment. Notice how the minor loop touches both the ascending and descending legs of the "large excitation" loop? And since there was no negative excitation, the minor loop would be wholly in quadrant 1, not half into "negative current" as you show.

I'll bet this motor has like 8 T/c, maybe 10 or more. So even if it is working on a minor loop, a difference of a couple hundred AT/p would give increased flux. 

Interesting puzzle 

major


----------



## GerhardRP (Nov 17, 2009)

major said:


> Hi Gerhard,
> <snip>
> Interesting puzzle
> 
> major


Here is my field map from the published Kostov curves.
The points are data and the curves are fits.

ZW:
To be sure what we have, do this sequence.
1 Series connection, polarity "+"
2 Parallel connection, polarity "+"
3 NO field connection, polarity "+"
4 NO field connection, polarity "-"
5 Parallel, polarity "-"
6 Series,polarity "-"
Report as before V, A, RPM.
Gerhard

PS, I see posts with images as thumbnails in the post. Mine are just attachments. How do I display the thumbnail directly?
GRP


----------



## zwmaster (Nov 23, 2009)

I will do this today or tomorrow.
What is "NO field connection"? D3 and D4 disconnected?
zw

To add attachment press lower button like you do to add files.
Then click paper clip icon here in edit window where you write text.
You should see something like:
[ ATTACH ] 5569 [ / ATTACH ]
and the result








Use "Preview Post" button to check if it's ok.


----------



## GerhardRP (Nov 17, 2009)

zwmaster said:


> I will do this today or tomorrow.
> What is "NO field connection"? D3 and D4 disconnected?
> zw


I mean neither field coil connected. BTW, did you note the sense of rotation? CW or CCW?
grp


----------



## major (Apr 4, 2008)

zwmaster said:


> I will do this today or tomorrow.
> .......D3 and D4 disconnected?


Hi zw,

Since you seemed uncertain about the connections, 


zwmaster said:


> Since I received the motor I was not sure about connections.
> Imprints on the holder plastic are saying like marked on the pictures.
> D1 and D2 are “short” so this should be one winding.
> D3 and D4 also.


I thought we could verify it by running the motor with just one of the two field circuits connected and the other unpowered. Each of the field circuits will have 2 coils most likely connected in series to each other inside the motor. If you wire it up, A1 +, A2 to D1, D2 -, and nothing connected to D3 & D4, then you run the motor with just 2 of the 4 coils getting current. It will still be a 4 pole motor and behave the same as a properly connected parallel at no load.

Obviously we don't want you to damage anything. So be ready to disconnect quickly from the battery if any of these tests cause overspeed, over current, or vibration.

Regards,

major


----------



## zwmaster (Nov 23, 2009)

GerhardRP said:


> ZW:
> To be sure what we have, do this sequence.
> 1 Series connection, polarity "+"
> 2 Parallel connection, polarity "+"
> ...


Here are new measurements
Gerhard:
1. Rotating right
U = 12.05 V
I = 25.1 A
f = 26.1 Hz -> 1566 min-1

2. Rotating right
U = 12.05 V
I = 23.7 A
f = 25.7 Hz -> 1542 min-1

3. Rotating right
NO TURNING JUST HIGH CURRENT
It didn’t help by turning the shaft by hand.
I expected that.

4. Rotating right
NO TURNING JUST HIGH CURRENT
It didn’t help by turning the shaft by hand.
I expected that.

5. Rotating right
U = -12.05 V
I = -23.9 A
f = 25.8 Hz -> 1548 min-1

6. Rotating right
U = -11.99 V
I = -24.7 A
f = 25.7 Hz -> 1542 min-1

major:
Case 1: rotating right
D1 -> +
D2 -> A2
A1 -> -

U = 11.92 V
I = -25.0 A
f = 25.9 Hz -> 1554 min-1
Case 2: rotating left
 A1 -> +
 D1 -> A2
 D2 -> -

U = 11.95 V
I = -23.4 A
f = 26.0 Hz -> 1560 min-1

Rotation is looking from behind the motor fan side where I have speed sensor.


----------



## major (Apr 4, 2008)

zwmaster said:


> major:
> Case 1: rotating right
> D1 -> +
> D2 -> A2
> ...


Thanks zw,

Tells me original connection was correnct. No answer to why RPM is same with half the field. Must be those interpoles 

major


----------



## GerhardRP (Nov 17, 2009)

major said:


> Thanks zw,
> 
> Tells me original connection was correnct. No answer to why RPM is same with half the field. Must be those interpoles
> 
> major


My thanks too... possible explanation: The current inrush for the series connection is greater than for the parallel connection for some reason, maybe because the acceleration is slower. That pushes the field farther up the saturatiin curve before it settles back to the operating point as shown in the graph below. The points are from the published data. The full hysteresis field curves are derived only from the 248v Kostov data
.


----------



## Plamenator (Mar 6, 2009)

Hello guys,
I am sorry for this but the Kostov motor mystery is due to my error.
On the website is the outline drawing of the prototype 11" 250V motor, where d3 and D4 are depicted as free standing cables.
In the regular production motors, D3&D4 were converted to exit bolts too which is better as it also saves the losses in the cables.
Unfortunately the connections are now different.
I have uploaded an updated drawing with the correct connections (I hope ) for the bolted version:
http://kostov-motors.com/files/productattachments/85334042b2b06288b2aa14327bcc2c76_F08A7.pdf

In effect, with the old connections, ZWmaster was bypassing 2 of the coils in series mode, hence the number of loops were the same as in parallel mode. Therefore rpm were the same .


----------



## major (Apr 4, 2008)

Plamenator said:


> In effect, with the old connections, ZWmaster was bypassing 2 of the coils in series mode, hence the number of loops were the same as in parallel mode. Therefore rpm were the same .


Thanks Plamen,

This explains it. I hope zw can run a series connected test just to verify and get the data for Gerhard. All this shows the value of bench testing.  It would have been almost impossible to figure out once the motor had been installed in the car.

Regards,

major


----------



## zwmaster (Nov 23, 2009)

Hello guys, 
I am @#%@#$^@$#%!#@$#@!$#@[email protected]#!$
Did you read my question in post #55?!
There I was writing that D1-D2 was one winding and D3-D4 the other.
Look sketch below.








Plamen you have made some corrections but all together are not adding up.
Designations on the motor connection holder (black plastic) and measured value (conductivity) are different from datasheet.
It’s still not clear if we look at the picture and connection numbering and the text for parallel-serial connection.















My suggestion would be (based on my measurements – picture):
- Parallel
D1 and D3 to “+”
D2 to D4 to A2
A1 to “-”
- Serial
D1 to “+”
D2 to D4 
D3 to A2
A1 to “-”

Let’s clear up this before I go to test this one more time. It’s other stuff waiting.
zw


----------



## GerhardRP (Nov 17, 2009)

zwmaster said:


> Hello guys,
> I am @#%@#$^@$#%!#@$#@!$#@[email protected]#!$
> Did you read my question in post #55?!
> There I was writing that D1-D2 was one winding and D3-D4 the other.
> ...


Hi:Your parallel setup is what you actually used for the measurements, so the coil sense would seem to be correct as your suggested parallel setup above. The series should then be
"+" to D1
D2 to D3
D4 to A2
A1 to "-"
This is consistant with the new text on the drawing.
Gerhard


----------



## major (Apr 4, 2008)

zwmaster said:


> My suggestion would be (based on my measurements – picture):
> - Parallel
> D1 and D3 to “+”
> D2 to D4 to A2
> ...


Hi zw,

The way I read it is how you have it diagrammed. A coil set internally connected to D4 and D3 and the other coil set internally connected to D2 and D1.

Using the DOT notation for coil polarity, I think you put the DOT at the D1 end of that coil and at the D3 end of the other coil. So to keep the polarities correct in the series connection, you need to connect D3 to D2 or D4 to D1. Otherwise the fields will cancel.

I think the revised Kostov text is now correct.

I share your frustration zw, but better to have discovered it now before you put it in your EV. You may have never have known until you serviced the motor and found 2 well seasoned field coils and 2 never used ones.

Personally, I thank you for going thru this. Motor mysteries are better than murder mysteries to me. But this one, like technical quandaries I've had in the past, boils down to trusting facts supplied by the experts (Kostov) in the beginning. When those facts turn out to be factious, you look back at your wasted time and have to call it a learning experience.

Kostov should thank you for discovering this discrepancy. I hope Plamen realizes this.

Regards, 

major


----------



## zwmaster (Nov 23, 2009)

Ok here is my latest SERIES connection and measurements:








U = 12.05 V
I = 16.89 A
f = 19.0 Hz -> 1140 min-1

zw


----------



## major (Apr 4, 2008)

zwmaster said:


> Ok here is my latest SERIES connection and measurements:
> 
> U = 12.05 V
> I = 16.89 A
> f = 19.0 Hz -> 1140 min-1


Now that is what I would expect for series connected fields. 

Thanks for running that, zw.

major


----------



## GerhardRP (Nov 17, 2009)

zwmaster said:


> Ok here is my latest SERIES connection and measurements:
> 
> View attachment 5623
> 
> ...


Thanks... What are the extra wires connected to D1 and D2? Open cables for the parallel mode?
Gerhard


----------



## zwmaster (Nov 23, 2009)

GerhardRP said:


> Thanks... What are the extra wires connected to D1 and D2? Open cables for the parallel mode?
> Gerhard


It's an old picture I used to paint connections on.
Red lines are representing the connection I have made to get series field mode.
zw


----------



## The Toecutter (May 30, 2010)

Interesting information. Back when I was still in the planning stages of my conversion, I had to make quite a few guesses as to what I could expect from an ADC 9" motor when operating over 600A; according to Rich Rudman on the EVDL at the time, accurately modelling this motor at around 1,000A was difficult to do reliably, and at around 4,000 rpm, would be operating around 50% efficiency with that current(hence, ~140 hp peak, instead of a commonly expected 200+ hp).

Have the issues with Gerhard RP's model been resolved yet? The graphs on the first page of this topic appeared to have highly optimistic torque figures at the upper end of the RPM range(> 4,000 rpm), as at 160Vmax, with a 1,000A limit, the ADC 9" motor would see a dramatic reduction in torque output at around 4,000 rpm due to back emf, according to numerous old posts on the EVDL. On paper using the equation T=k*i^n, the ADC 9" theoretically would have close to 400 lb-ft of torque at 1,000A, but that equation neglects all of the losses at that operating point of the motor, and in reality it would make around 200 lb-ft. While the model in this topic does include losses, are they truly accurate at the motor's operating extremes where you are bound to see flux saturation?

Granted, the WarP 9" that Gerhard modelled is not the same as the ADC 9", but I would expect similarities given that the motors had similar designs.


----------



## GerhardRP (Nov 17, 2009)

The Toecutter said:


> Have the issues with Gerhard RP's model been resolved yet? .


The discrepancy between the published Warfield 72V dyno data _vs_. data from the Electrabishi and from Tesseract have not been resolved. 
There are mentions in other threads of data dumps taken or collected by others. If I could get my hands on several of those, I could figure it out.
 My day job has kept me from completing an analysis of the Electrabishi using data I digitized from some old graphs...maybe this weekend. I plan to use acceleration and the mass of the vehicle to end up analysing all the losses involved in that system.
Gerhard


----------



## electrabishi (Mar 11, 2008)

GerhardRP said:


> The discrepancy between the published Warfield 72V dyno data _vs_. data from the Electrabishi and from Tesseract have not been resolved.
> There are mentions in other threads of data dumps taken or collected by others. If I could get my hands on several of those, I could figure it out.
> My day job has kept me from completing an analysis of the Electrabishi using data I digitized from some old graphs...maybe this weekend. I plan to use acceleration and the mass of the vehicle to end up analysing all the losses involved in that system.
> Gerhard


I can get you the actual data dumps from any of those runs you have seen graphs for  Which ones are you most interested in? For Electrabsihi I have no 1/4 mile runs, but I did do a bunch of 0-60 mph data dumps.

Mike


----------



## electrabishi (Mar 11, 2008)

major said:


> Hi zw,
> 
> This makes me suspect the speed readings even more  As the battery dies and the voltage decreases, are you able to tell if the motor is slowing by sight or sound?
> 
> ...


I think I missed the setup of this motor. Are the brushes advanced?

Mike


----------



## major (Apr 4, 2008)

electrabishi said:


> I think I missed the setup of this motor. Are the brushes advanced?


Hi Mike,

It was a Kostov with interpoles, so set to neutral. Turns out the wiring diagram on the Kostov drawing was wrong or something like that. Once he got it wired correctly, it behaved as expected. It's all documented in the thread. Some interesting theories put forth to try to explain what turned out to be "human error". But it really does show the benefit of bench testing. This likely would never have been discovered in the car 

major


----------



## electrabishi (Mar 11, 2008)

Maybe this is more appropriate in this thread. Oh well it can be in 2 places 



electrabishi said:


> ........
> I did find the data you were looking for on the Electrabishi:
> 
> One note, I made a mistake above in that it was the motor voltage that was reading wrong in my particular hairball. You can easily see what it should be during any of the 100% duty cycle events. In that case the motor voltage and battery voltage should be the same. If you notice the graphs show motor voltage way hhigher that what I have it set to. The battery voltages indicated are accurate. So if you do any math using the motor voltage figure out the proper scaling factor and use the 100% duty cycle events to calibrate that factor.
> ...


----------



## GerhardRP (Nov 17, 2009)

electrabishi said:


> Maybe this is more appropriate in this thread. Oh well it can be in 2 places


Fantastic! Thanks.
Gerhard


----------



## GerhardRP (Nov 17, 2009)

electrabishi said:


> Maybe this is more appropriate in this thread. Oh well it can be in 2 places


Hmm. There is something wrong with most of the links, the pages don't open.
Gerhard


----------



## electrabishi (Mar 11, 2008)

GerhardRP said:


> Hmm. There is something wrong with most of the links, the pages don't open.
> Gerhard


Hmm, they are working in 3 different browsers for me.

Let me put the raw links here for you for the last two files.
These are just links to a folder on the NEDRA Yahoo Group's Files section:

http://f1.grp.yahoofs.com/v1/ICAKTK...ults/Electrabishi Data/Zilla_DAQ_8Jul06_7.JPG

http://f1.grp.yahoofs.com/v1/ICAKTP...ults/Electrabishi Data/Zilla_DAQ_8Jul06_7.xls


If you PM me your e-mail address I'll just mail them to you ;-)

Mike


----------



## GerhardRP (Nov 17, 2009)

electrabishi said:


> If you PM me your e-mail address I'll just mail them to you ;-)
> Mike


Got the files. Thanks.
Here is the first step of the analysis. 

What I have done is to fit voltage vs. angular speed for the constant current segments. Projecting back to zero speed gives the stalled voltage for each currant. Plotting thosevoltages vs. current yields the brush volrage and the resistance. These will be used as known loss factors and will allow the determination of the motor saturation curve.


----------



## GerhardRP (Nov 17, 2009)

GerhardRP said:


> Got the files. Thanks.
> Here is the first step of the analysis.


Hey Mike, do you know what the gear ratios are on that truck?
Gerhard


----------



## electrabishi (Mar 11, 2008)

GerhardRP said:


> Hey Mike, do you know what the gear ratios are on that truck?
> Gerhard


Yes I do, let me get that for you...I need to find my Mitsubishi log book first (still packed up from the move from Alaska). Otherwise we can do a Google search for a Mitsubishi KM145 tranny ;-) I looked it up once but without my "book of knowledge" in front of me I'm at a loss. I'll be looking for it. My memory says the rear end is a 3.83:1. But I'll look for my notes.

Mike


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## electrabishi (Mar 11, 2008)

Sorry, still haven't found my notebook (I have the Pinto notebook right here in front of me). Have moved ALL my stuff 4 times in less than a year :-( It will turn up and I'm zeroing in on it. Boxes.. upon boxes.. 

What specifically are you needing to find using the gear ratios?

Mike


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## GerhardRP (Nov 17, 2009)

electrabishi said:


> Sorry, still haven't found my notebook (I have the Pinto notebook right here in front of me). Have moved ALL my stuff 4 times in less than a year :-( It will turn up and I'm zeroing in on it. Boxes.. upon boxes..
> 
> What specifically are you needing to find using the gear ratios?
> 
> Mike


Hi Mike,
Soon I will be ready to look at acceleration, so gear ratios and tire size will give the conversion from RPM to meters per second. I could use the speeds noted on the JPGs though.
As an update on the calculations, I have redone the resistance fits after accounting for the motor temperature. I also compressed the data set by averaging in 0.5 second intervals to reduce the noise. I now have resistance is 16.1 milliOhms and brush losss is 1.18 Volts. Subtracting these losses from the motor voltage I get the Back EMF. Dividing by rotational speed in SI units (radians per second), I get the field map as shown in the attached file.
I know you took data a week before the set you recently sent me... I would like to have the 1000 Amp data sets. Also, I would like some data in the low current region to fill things in if you have any.
Yours,
Gerhard


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## electrabishi (Mar 11, 2008)

Yes when I was plotting these out with Excel I was doing a moving average on 1 samples (so 1 second averages) to smooth it out. But that was just for visual display purposes.

Keep in mind the temp reported is not motor temp, its the controller heat sink temp. The trend may track in the same direction but I do not have any accurate temp data on the motors, for th Mitsubishi.

I'll pull up that previous weeks data you mentioned. I have lots of data sets, many of which I have never even opened up to view  Will mail them to you directly.

Mike


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## GerhardRP (Nov 17, 2009)

electrabishi said:


> I have lots of data sets, many of which I have never even opened up to view  Will mail them to you directly.
> 
> Mike


Great...
Did you ever do a coast-down? Start with 60MPH then no throttle down to say 20 MPH to get drag and rolling resistance?
Gerhard


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## electrabishi (Mar 11, 2008)

Nope never did a coast down. The controller right now is in Alaska racing in a Junior Dragster so as soon as it comes back I can do that test.

Here is the tranny and rear end gearing:

Mitsubishi KM145-8 Manual 4WD Transmission
Gear ratios:
First ………………….…………………. 3.967 : 1
Second …………….……………………. 2.136 : 1
Third …………….……………………….1.360 : 1
Fourth ………….………………………... 1.000: 1
Fifth ………….…………………………. 0.856 : 1
Reverse …….…………………………… 3.578 : 1

Rear Differential .................................... 3.909:1

Tires 225-75R15

Mike


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## GerhardRP (Nov 17, 2009)

electrabishi said:


> Nope never did a coast down. The controller right now is in Alaska racing in a Junior Dragster so as soon as it comes back I can do that test.
> 
> Mike


Actuall the typical drive dataset includes a couple of coasting segments. Question is are they on level ground?
The BEMF/Speed from this data set is attached.
Gerhard


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## Tesseract (Sep 27, 2008)

GerhardRP said:


> As an update on the calculations, I have redone the resistance fits after accounting for the motor temperature. I also compressed the data set by averaging in 0.5 second intervals to reduce the noise. I now have resistance is 16.1 milliOhms and brush losss is 1.18 Volts.


We get similar results... the following is the scatter plot of calculated resistance for a Warp 9... not corrected for temperature. The skewing/spreading of the data points at low currents is mainly an artifact of the very low duty cycle.


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## GerhardRP (Nov 17, 2009)

electrabishi said:


> Nope never did a coast down. The controller right now is in Alaska racing in a Junior Dragster so as soon as it comes back I can do that test.
> 
> Here is the tranny and rear end gearing:
> 
> ...


Hey Mike,
What was your commuting distance for the "typical" data set you sent?
Integrating the speed using these gear ratios and finding your shift points, I get 7.93 miles.
Do you have a dataset with 85 MPH on level ground?
Gerhard


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## The Toecutter (May 30, 2010)

Gerhard, thanks for posting that data! What unit is omega supposed to be expressed in within that pdf? Normally, it is 2pi/T, but I'm not sure if that is what you mean with that symbol.

At 5500 rpm, you get 576.66 for omega when expressed in radians per second. At ~0.32 BMEF per omega at 600A, then the torque generated at 600A should be produced at 5500 rpm at 184V. But, 184V and 600A into the motor is 110.4 Kw electrical, and given that at 600A the motor will produce about 120 lb-ft, at 5500 rpm, this is ~94 kW mechanical, giving an efficiency of 85%.

Provided this is correct, that's not too bad! But it seems quite optimistic for power to be made that high in the RPM range, given the dyno results for cars like Otmar's 914 and his 8" motors, and it would also seem optimistic for efficiency to be that high with that amount of current given the amount of losses from heat alone at that current, let alone losses from the high rotational speed of the motor, brush losses, ect.


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## electrabishi (Mar 11, 2008)

GerhardRP said:


> Hey Mike,
> What was your commuting distance for the "typical" data set you sent?
> Integrating the speed using these gear ratios and finding your shift points, I get 7.93 miles.
> Do you have a dataset with 85 MPH on level ground?
> Gerhard


Pretty close. My measured range to work was 7.6 miles based in the trucks odometer. But that was average as I might have taken some side streets on occasion . I don't know if that last set of data I sent you included any 85 mph data. I didn't have too many of those higher speed runs but when I get home tomorrow I'll look to see if I saved any of those.

Mike


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## electrabishi (Mar 11, 2008)

GerhardRP said:


> Actuall the typical drive dataset includes a couple of coasting segments. Question is are they on level ground?
> The BEMF/Speed from this data set is attached.
> Gerhard


To answer this question, yes all of the coasting sets are on level ground. There were only a couple over passes on my commute (if they were at speeds over 45 mph) and I only did coasts on the level parts. meaning on the downhill I would gently accelerate to get the speed up and then coast tot the next small hill. Spots with no pot input are most likely on level ground. Otherwise the surface streets below 45 mph were pretty much level.

Mike


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## electrabishi (Mar 11, 2008)

If you really want to get technical you can look up terrain data between 10121 Marmot Ct, Anchorage 99515 and 2550 Denali St, Anchorage 99503. The highway route with speeds over 45 mph were along Minnesota Drive. Any full commutes 45 and under were along C St (which is the way I predominately travelled).

Mike


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## Pedro_Rebollar (Jul 7, 2010)

Hi,

where do we can get the following DC Motor used for a hidraulic pump that is mounted in a fork lift Elwell Parker:

 
Mod. 32-71
Clase f
Serie. 82021
Voltaje 48/72
Winding compount
Continuo 1 hr
18hp 
110 am 220 

Thanks in advance for you time and help


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## GerhardRP (Nov 17, 2009)

The Toecutter said:


> Gerhard, thanks for posting that data! What unit is omega supposed to be expressed in within that pdf? Normally, it is 2pi/T, but I'm not sure if that is what you mean with that symbol..


I prefer to use SI units: that means rotational speed, omega is in radians/second.


> At 5500 rpm, you get 576.66 for omega when expressed in radians per second. At ~0.32 BMEF per omega at 600A, then the torque generated at 600A should be produced at 5500 rpm at 184V. But, 184V and 600A into the motor is 110.4 Kw electrical,


None of the data that was used to derive the saturation curve was at higher than 4K RPM, so your 5500 calculation is an extrapolation ...in an earlier post I noted that This system has a resistance of 16.1 milli ohms and brush loss of 1.18 volts. At 600 amps that is 10.8 volts and 6.5 kW loss, We would be asking for 117 KW at 195 volts which is beyond the battery pack capability: it sags to 130 volts at that kind of power demand.


> and given that at 600A the motor will produce about 120 lb-ft, at 5500 rpm, this is ~94 kW mechanical, giving an efficiency of 85%.


I don't have any dyno data for these motors other than that from net-gain which don't match these curves as noted in an earlier post in this thread. Without dyno data, I can't model The iron losses in the motor. Calculateing raw torque from my saturation curve gives 600x0.32 =192 Nxm or 142 ft-lbs, correspounding to 110 kW.


> Provided this is correct, that's not too bad! But it seems quite optimistic for power to be made that high in the RPM range, given the dyno results for cars like Otmar's 914 and his 8" motors, and it would also seem optimistic for efficiency to be that high with that amount of current given the amount of losses from heat alone at that current, let alone losses from the high rotational speed of the motor, brush losses, ect.


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## GerhardRP (Nov 17, 2009)

Hi All..
I applied the model to a Warp11Hv in another thread. http://www.diyelectriccar.com/forums/showthread.php?p=199110#post199110
Gerhard


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## GerhardRP (Nov 17, 2009)

I applied the model to some Kostov 11 data found here http://kostov-motors.com/files/productattachments/04a1d5e7278db48475f2aa409b5df5ce_S192F01.1.pdf Which includes data for the same motor with the fields connected in parallel. In the first plot I show the saturation curves derived plotted vs. motor current. I also show the parallel results vs. one half the armature current. The results do not overlap as expected.
I made a guess that the fields were miswired. Instead of:

/--->1/2 current-->coil1-->coil2-->\
\-->1/2 current-->coil3-->coil4--->/

We have
/-->1/4 current-->coil1-->coil2---->coil3-->\
\-->3/4 current-->coil4---------------------->/

In the lower configuration, the sum of the number of poles times current is 1.5 compared to 2.0 for the actual parallel hookup and 4.0 for the series setup. The second graph shows the "parallel" data vs. 3/8 times the armature current which makes the curves coincide. Actually, the lower configuration gives a much better field weakening.
I also display my recently posted Warp11-HV curve.The Kostov total series resistance is 68 mOhms. Compared to 27 for the Warp.
Notice that if you divide the Warp current by two you get close to the Kostov curve.


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> Anyway, looks like there is excellent agreement between electrabishi and me; not so much with Warfield... That's just shocking, I tell you!


Hi Tess and Mike,
I have occasionally pondered on the WarP 9 discrepancies [see post #38]. I was looking at Jim Husted's gallery and notice that the field coils in the motor he was rebuilding are wired in a 2 series x 2 parallel configuration. http://hitorqueelectric.com/gallery/v/custom_motors/warp9_101/Dscn0336.jpg.html
This would be a low-voltage flavor of the motor. My guess is that the other motors are a high-voltage build with the coils actually 4 series connected. Can you confirm that?
Gerhard


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## electrabishi (Mar 11, 2008)

I don't have an -HV so I can't comment. I do know that the fields in all 4 of my Warp 9's (two of which are TransWarp's) are just like in Jim's pic. 2S2P on the fields.

Mike


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## 7circle (May 29, 2010)

GerhardRP said:


> I applied the model to some Kostov 11 data found here http://kostov-motors.com/files/productattachments/04a1d5e7278db48475f2aa409b5df5ce_S192F01.1.pdf Which includes data for the same motor with the fields connected in parallel. In the first plot I show the saturation curves derived plotted vs. motor current. I also show the parallel results vs. one half the armature current. The results do not overlap as expected.
> I made a guess that the fields were miswired. Instead of:
> 
> /--->1/2 current-->coil1-->coil2-->\
> ...



Have you/anyone found the Piece wise resistances for each field and the Rotor?

I'd like to work out the modelling of a DC motor like the Kostov 11" with interpole/commutating-poles.

I've been try to come up with the details using the Kostov Spec too.
I'm not sure if it's the saturation or the armature reaction or the size of the interpoles that makes it so difficult to analyse.

I just want to know what voltage to apply to the field and armature to make a direct drive setup go in reverse at a low 200RPM.


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## gor (Nov 25, 2009)

hi, Gerhard
can you post warp9 test data you used (96,144,156v; 300,400,500a..> etc) just table(spreadsheet)?
thank you


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## GerhardRP (Nov 17, 2009)

gor said:


> hi, Gerhard
> can you post warp9 test data you used (96,144,156v; 300,400,500a..> etc) just table(spreadsheet)?
> thank you


I got the data from some Zilla logs that Electrabishi shared. My present Excel spreadsheets are too messy  to share. I'll try to clean them up and share what I think I learned from the data.
Gerhard


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## GerhardRP (Nov 17, 2009)

See next post for updated file. I deleted the older one.


GerhardRP said:


> I got the data from some Zilla logs that Electrabishi shared. My present Excel spreadsheets are too messy  to share. I'll try to clean them up and share what I think I learned from the data.
> Gerhard


Well, I spent a little time and set up a spreadsheet to calculate various curves for a Warp9 motor based on data provided by Mike Wilmon derived from several Zilla data dumps.
The first page gives the creative commons permissions.
The second page contains all the parameters describing the model: some are for the motor and others are for the battery pack. For starters, I strongly suggest that you change only battery entries.
The third page has all the calculations. You enter the desired current in the first colum and the RPM in the second [yes, I convert to SI units for the work]. To transfer the "current" data into the program, check new data [it will say "true" click again and it will report "false"] and then calculate. If you ask for a current greater than the battery will support, the program reduces the request in 1 volt steps.
The program is an excel file with extension .xls I have changed the file extension to .doc for posting. To use it, change it back.


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## GerhardRP (Nov 17, 2009)

GerhardRP said:


> Well, I spent a little time and set up a spreadsheet to calculate various curves for a Warp9 motor based on data provided by Mike Wilmon derived from several Zilla data dumps.
> The first page gives the creative commons permissions.
> The second page contains all the parameters describing the model: some are for the motor and others are for the battery pack. For starters, I strongly suggest that you change only battery entries.
> The third page has all the calculations. You enter the desired current in the first colum and the RPM in the second [yes, I convert to SI units for the work]. To transfer the "current" data into the program, check new data [it will say "true" click again and it will report "false"] and then calculate. If you ask for a current greater than the battery will support, the program reduces the request in 1 amp steps.
> The program is an excel file with extension .xls I have changed the file extension to .doc for posting. To use it, change it back.


I have added various controller set limits.


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## GerhardRP (Nov 17, 2009)

GerhardRP said:


> I have added various controller set limits.


Here is a graph showing Warp9 capability with various limits.

1. The linear rise from zero is from the 1000 Amp limit.
2. The near linear fall is from the motor voltage reaching the sagged battery voltage.
3. The flat comes from limiting the battery sag to 150 volts. [The slight rise in power reflects improving motor efficiency.]
4. The steeply falling curve above 4300 RPM resulrs from a motor limit of 150 Volts.

Gerhard


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## gor (Nov 25, 2009)

Gerhard, can you use your model to estimate warp 11hv values 0- 2000a at v=72;144;288? (regular torque-amps-rpm chart, only extended) 
attachment - data from netgain site in text file 
http://www.go-ev.com/motors-warp.html#WarP_11HV​thank you
and big thanks on behalf of diy community and all people for sharing your knowledge


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