# Horsepower



## mattW (Sep 14, 2007)

Well because they deliver their power so differently it sort of depends what you want it for, are we talking power for low speed acceleration, 0-60 times, hill climbs or top speed? The peak power of the motor (as in for short term bursts like acceleration) is usually about 4 times greater than the continuous power, which is what motors are generally rated at. A 5hp ICE could be replaced by a 1 1/4 hp electric motor giving the same peak power, but they would behave pretty differently. The electric motor would give you better acceleration at low speeds and perhaps a better 0-60 time (not that you could go that fast on a 5hp motor) but would probably have less hill climb ability (on long hills) and a lower top speed since the electric motor doesn't like giving out full power for very long whereas an ICE sit at peak power rpms for much longer. Check out the wiki table and this motor selection guide to help choose a motor for your requirements.


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## Brendonbosy (Dec 13, 2007)

I have a 2400 lbs 99' Celica and I'm looking to put some muscle into it. Right now it has a 2.2L I4 engine that makes 135 HP @ 5400 RPM and 145 ft-lbs @ 4400 RPM. It does 0-60 in a pitiful 8.5 seconds and th 1/4 mile is an equally pitiful 16.4 seconds.

I'm looking to drop my 0-60 time to less than 7 seconds and my 1/4 mile to less than 15. I don't care so much about top speed, but I would like to have some good passing abilities on the highways. I want some good power from 70-100 mph. So how powerful do I need my motor to run at for this? I was assuming 100 kW (134 HP) would be more than enough. True?


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## mattW (Sep 14, 2007)

Yeah it would probably be overkill. To get 100kW without even considering losses and inefficiencies would take 700A from the batteries at 144V. So you are going to need some serious batteries to tackle that much power. If you take a look at the FB1-4001 Motor you would be running with 75kW (100hp) peak power. 



> The top of the range. This motor gives stunning acceleration in a car 1200 to 1500kg. Drives a 2000kg vehicle very well. High torque means you get superb pulling power from a standstill or accelerating from low speed.
> Ideal for sports or racing cars. Has been successfully used in heavy electric vehicles.


Keep in mind your car is 1090kgs Just imagine the torque curve for an ICE compared to an EV, the flatness of an EV curve means you get power right through the range not just at the high rpms (power=torque x rpm but an ICE's peak torque is at high rpm anyway so you get a high peak and sharp curve compared to an EV which has less peak power but more total) so more power actually gets to the wheels as you accelerate. You should check out the guys at NEDRA for a comparison of hp to 0-60 times.


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## John (Sep 11, 2007)

For a high performance set up I like the idea of using two ADC X91-4001's with one of these driving each end of the car through specially constructed single ratio reduction differential boxes. I'd use a Zilla 2K 300volt controller and carry 25 light deep cycle batteries for a total system voltage of 300 volts. For my platform I'd choose a 93 Mitsubishi Mirage coupe as it has a payload of almost 600 kg and is built on the same floor pan as a similar year EVO Lancer. I'd find a wrecked EVO Lancer to donate its Awd bits for the rear drive part of the project. I'd sacrifice the rear seat and mount most of the batteries amidships close to the road. This would keep the polar moment of inertia of the vehicle as small as practical and the centre of gravity low.


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## Hi Torque Electric (Dec 23, 2007)

Hey all

To the gokart question:
With a 6.7" palletjack motor (like the raffle motors on my site) at 48 volts, 400 amp controller 4.5 to 1 ratio gave me 35 MPH top speed which was "like now" and what felt like an ICE equivlent of 7HP.

Replying to the FB1 posts:
I've had the pleasure to have personally driven Waylands Blue Meanie (156 volt, FB1, Zilla'd Datson) and it'll burn rubber in third, and smoke screens 4 lanes of traffic in second gear  I mean I think it would  being I'm not one to break the law you know  With the right batts and a Zilla2K you could push that same FB1 to over 300HP peak for short bursts that is if you really wanted to impress your friends. Be aware that this would probably rip your tranny and drive line from your car though 

I also had a look at that motor usage link and they are a tad on the conservitive side of what the top end voltage limits are actually being run at.
Cya
Jim


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## ronis108 (Dec 14, 2007)

To give an idea about how the 4001 motor will do between 70 and 100MPH you can look at the dyno chart for that motor at 144 volts. YOu can see that between 3000 and 4000 rpm, (my guess ast to aproximate motor speed at 70-100 MPH) torque is dropping off big time. at 3000 rpm you will have about 150 ft/lbs which is pretty good, but by the time you are at 4K you are about 1.2 that which is pretty weak. 

I know this is an old thread, but I am working with the same performance questions.  I woukld really like to see some motors, (other than AC propulsion in the Tesla) that maintains torque up to around 6K To me that is am ideal perfromance motor. It matches the average tranny and gives good HP without having to subject your dive train to several hundred ft/lbs of torque.

ron


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## Dennis (Feb 25, 2008)

DC motors had the constant torque speed range characteristic from the controller before AC flux vector drives became competitive against DC drives.

In industry a few years ago a shunt wound motor was used in constant torque applications. It works off the principle that DC motor's torque is proportional to the current. Thus if you had a set point of 50 ft*lbs from 0 to 3000 RPM (obviously a load needs to be applied to the motor...) and the current is 90 amps that was required for the motor to produce 50 ft*lbs then each time the current drops below 90 amps, the controller would increase armature voltage until 90 amps where reached or employ field weakening until 90 amps was reached. Likewise, if in excess of 90 amps then the controller would either decrease the armature voltage until set point was reached.


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## ronis108 (Dec 14, 2007)

Dennis said:


> DC motors had the constant torque speed range characteristic from the controller before AC flux vector drives became competitive against DC drives.
> 
> In industry a few years ago a shunt wound motor was used in constant torque applications. It works off the principle that DC motor's torque is proportional to the current. Thus if you had a set point of 50 ft*lbs from 0 to 3000 RPM (obviously a load needs to be applied to the motor...) and the current is 90 amps that was required for the motor to produce 50 ft*lbs then each time the current drops below 90 amps, the controller would increase armature voltage until 90 amps where reached or employ field weakening until 90 amps was reached. Likewise, if in excess of 90 amps then the controller would either decrease the armature voltage until set point was reached.


So how does the above apply to constant amparage under full accellaration? I am thinking that If the controller is giving it all it can, say 1000amps, the motor will then create torque. If the torque is greater than the interia of the car (load) the rpms will increase. If voltage is constant, amps are constant, rpm increases, but the motors torque at some point must drop off because the motor is only caplable of so much. What controls the torque a motor is CAPABLE of producing. Can the motor continue to DRAW that 1000 amps no matter how fast it is turning. DRAW is an AC phenomena if I understand correctly but a DC motor just does what you tell it to do? In other words, you give it 144 V and 1000 amps it will pretty much turn faster and faster until it self destructs or the load overcomes it. 

I am still trying to understand how the motor respond to say 1000 amps out of the controller at a set voltage. It seems the charts are showing amps declining as the rpm increases, but in our cars the controller is keeping the amps at the controllers maximum as long as the electron pedal is to the floor right?

thanks
ron


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## WesL (Feb 26, 2008)

FB1: RPMs increase as amps decrease?

Assuming we are both looking at the same thing, no. Amps & RPM are both on the vertical axis.

I had to stare at this for awhile. I think some confusion stems from being used to seeing charts of hp or torque (vertical axis) vs. RPM (horizontal axis). Here, everything (amps, RPM, hp, & efficiency) is plotted vs. torque.

I'm guessing, but we might be able to get a better understanding of the motor characteristics if we were to "conventionally" re-plot everything vs. amps and/or RPM (horizontal axis). Advanced DC may have plotted its data this way for brevity.


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## Dennis (Feb 25, 2008)

> So how does the above apply to constant amparage under full accellaration? I am thinking that If the controller is giving it all it can, say 1000amps, the motor will then create torque. If the torque is greater than the interia of the car (load) the rpms will increase. If voltage is constant, amps are constant, rpm increases, but the motors torque at some point must drop off because the motor is only caplable of so much. What controls the torque a motor is CAPABLE of producing. Can the motor continue to DRAW that 1000 amps no matter how fast it is turning. DRAW is an AC phenomena if I understand correctly but a DC motor just does what you tell it to do? In other words, you give it 144 V and 1000 amps it will pretty much turn faster and faster until it self destructs or the load overcomes it.


Torque is controlled by current, the controller keeps the current at constant state until the BACK EMF of the motor is to great that the controller can no longer maintain the current draw since it runs out of voltage to force into the armature for the same current level. Thus the current will start to decline as the motor spins faster and faster.
It should be no surprise since a motor generates counter voltage that opposes the supply voltage (BACK EMF). 



> I am still trying to understand how the motor respond to say 1000 amps out of the controller at a set voltage. It seems the charts are showing amps declining as the rpm increases, but in our cars the controller is keeping the amps at the controllers maximum as long as the electron pedal is to the floor right?
> 
> thanks
> ron


When you set the current limit on a controller it does not mean that rated voltage is applied at rated current. What it does mean is that the current will not exceed that limit. To do this it must modulate the DC by chopping it many times a second such that the average voltage is reduced causing the current draw to decrease to the limit but never exceed it. What the voltage of the controller means is it will apply full voltage once the motor is STABILIZING, meaning it is starting to reach a point where the speed increase is getting less and less and (the current will start to decline sharply) increase in voltage does not result in a large increase of current. All motors exhibit this due to the BACK EMF phenomenon. You can take a motor and run it as a generator for example..


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## ronis108 (Dec 14, 2007)

I am still trying to understand just how controllers work. Torque is controlled by current, and increased voltage will increase the rpm that the motor can maintain that torque. Right? So, am i correct in thinking that the controller does not feed variable amparage to the motor, but rather is set to a specific limit to the amount of amps it feeds the motor? For example the Zilla 2K is capable of a max of 2k amps but can be set for a lower amount. Whatever it is set for will be the operating amparage of the motor? The motor will then keep a flat torque (as on a dyno graph) up to the rpm where it starts dropping off due to insufficient voltage to hold the torque at higher rpms? 

I know theTesla is AC, but I am assuming its flat torque curve to 8000rpm is due to its high voltage. If you cut the voltage in 1/2 it would have a flat torue curve and the same amount of torque but only till 4000rpm? (in theory, ignoring any other side effects that enter in)

thanks
ron


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## 3dplane (Feb 27, 2008)

Ron! I'm no expert but from your questions I feel you seem to think that the controller HAS to feed the amps to the motor in a constant fashion.The amps come from the load on the motor.You can have a 2k amp zilla in a gocart that draws 50 amps at top speed regardless of how big motor is on it(within reason) if thats what it draws thats what it gets(does that make sense?)Now hook a car behind the gocart and tow it at top speed and the load on the whole system will be much greater (say 200 amps at 40 mph)so as long as the system limits are not exceeded(motor and controller amps not greater then what they can handle) your controller will "feed" 200 amps.I hope this silly example helps a little and sorry if i misunderstood the part you are tying to gain better understanding of.Barna


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## Dennis (Feb 25, 2008)

> I am still trying to understand just how controllers work. Torque is controlled by current, and increased voltage will increase the rpm that the motor can maintain that torque. Right? So, am i correct in thinking that the controller does not feed variable amparage to the motor, but rather is set to a specific limit to the amount of amps it feeds the motor? For example the Zilla 2K is capable of a max of 2k amps but can be set for a lower amount. Whatever it is set for will be the operating amparage of the motor? The motor will then keep a flat torque (as on a dyno graph) up to the rpm where it starts dropping off due to insufficient voltage to hold the torque at higher rpms?
> 
> I know theTesla is AC, but I am assuming its flat torque curve to 8000rpm is due to its high voltage. If you cut the voltage in 1/2 it would have a flat torue curve and the same amount of torque but only till 4000rpm? (in theory, ignoring any other side effects that enter in)
> 
> ...


The Zilla controller works like this: you are at a standstill which means the motor is not moving therefore not creating any back EMF to limit current. The current must be limited to prevent damage to the motor and controller. So the controller will limit the current of lets say 500 motor AMPs set by the user. To do this it measures the current flow to the motor by some means of current sensing either with a shunt or some other means. If the value read on the current sense device exceeds the user value of 500 amps then the controller will shut off the MOSFETS completely and then after a delay will allow them to continue their switching. All of this happens very quickly.

Where the Zilla controller differs from other controllers though, is it will try to keep the current pegged at the max of 500 amps *if you floor it full throttle* by increasing the voltage average very quickly before the motor can speed up fast enough to produce the necessary BACK EMF to oppose the voltage applied to it. The result of this is the torque will be constant from zero to the clamp off point. The clamp off point is where the controller runs out of voltage needed to keep the 500 AMPs flowing to the motor so the current will start to decline as the back EMF of the motor starts to take effect. The result of the torque curve is it starts to fall off similar to 1/X limited to quadrant I on a Cartesian graph. Obviously free spinning the motor with no load will not have the torque effect (it will speed up super fast and fly apart if you hit full throttle instantly) . The motor has to be under load.....

Here is a dyno graph for the controller.

http://www.dragtimes.com/1990-Nissan-240SX-Dyno-Results-Graphs-7382.html







For an AC controller it does not work the same. Frequency AND voltage must be changed. Plus the controller for AC motors has to separate the torque producing current from the flux inducing currents. AC controllers for that reason are quite a bit more complex.


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## Wirecutter (Jul 26, 2007)

ronis108 said:


> I am still trying to understand just how controllers work. Torque is controlled by current, and increased voltage will increase the rpm that the motor can maintain that torque. Right?


Ron -
Right. There are other factors (and reasons behind them), but basically speaking, volts become RPM, and current becomes torque.

-Mark


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## Batterypoweredtoad (Feb 5, 2008)

What make things the clearest to me is thinking of it like this:
-The higher the voltage applied to a motor the faster the motor wants to turn.
-The difference between how fast a motor is going and how fast it wants to go makes the motor draw amps.


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## 3dplane (Feb 27, 2008)

Batterypoweredtoad! Thats about the best way to put it.If you refined that last sentence it should be in a book as a teaching "tool".maybe something like: the greater the difference between how fast a motor is going and how fast it wants to go,the greater the amp draw or something along those lines.(btw.I work in Gainesville)Barna.


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## Batterypoweredtoad (Feb 5, 2008)

3dplane said:


> Batterypoweredtoad! Thats about the best way to put it.If you refined that last sentence it should be in a book as a teaching "tool".maybe something like: the greater the difference between how fast a motor is going and how fast it wants to go,the greater the amp draw or something along those lines.(btw.I work in Gainesville)Barna.


3dPlane-sent you a pm!


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## ronis108 (Dec 14, 2007)

Thanks for all the expainings! That helps alot. And, I guess I kinda highjacked this thread, so I hope others have benefited as well.

From what I gather here, the controller does not dole out amps but rather limits the amparage available to the motor. The motor draws amps as needed to bring to or maintain the speed that the motor wants to turn which is a result of the voltage put to it. The more the load the more current it will draw to catch up or maintain. Dennis gave a full throttle example where the amps are at a maximum that the controller will allow by way of cutting out voltage manytimes per second to cause amps to drop below the set limit. 3dplane, implied that the controller does not feed a set amount of amps? So I am guessing that at partial throttle there is a way that the controller is regulating amps to a value less than the controllers maximum so that the motor is not so eager to come up to speed? or is this again just a case of adding a smaller voltage increase an therefore the motor draws less current?

thanks 
Ron


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## ronis108 (Dec 14, 2007)

Another Horsepower question:

If you look at this spread sheet...
http://www.go-ev.com/images/003_12_WarP_8_SpreadSheet.jpg
You will see that at higher rpms the torque and amps decrease. Are these maximum values? I believe much more can be gotten out of this motor. Can the motor actually draw say 2000 amps at around 5000rpm and increase torque proportionately? (minus heat loss) 

Is there a way to use this chart and extrapolate how much the torque would increase at each rpm with a 2k controller?

Thanks
Ron


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## 3dplane (Feb 27, 2008)

Hey Ron!
Note that the voltage is constant 72 v on that chart regardless of load.So the way that chart came about is they were supplying 72 volts to that motor and loaded the motor to "bog"down to that lowest rpm(bottom of chart).At that point the amp draw was (whatever the chart says) the highest,so VxA=max watts or HP.When they loaded it lighter the rpm was higher,amp draw lower etc.Your question can the motor draw 2k amps at 5k rpm? sure(if it survived)but how do you do it? increase the voltage waay higher then 72 volts.Try to forget about the controller for now .Imagine a 72 volt battery pack the size of a house (no voltage sag and unlimited amps available)and we hook this motor to it with different loads on the motor,for example different size propellers on the shaft.If our largest prop holds the motor down to the rpm on the bottom of that chart the amp draw will be the same as on that chart.Remember no controller just a huge battery.Smaller props will let it spin faster and amp draw and power will decrease UNLESS we increase voltage.Was that confusing enough? I"m just trying to put it down the way I see it Barna.


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## ronis108 (Dec 14, 2007)

OK, so ignoring other losses, if we yp the voltage to 144V, then what happens? I am guessing that the amp draw will be the same but the doubled voltage will make the motor want to spin faster...but, if we don't let the motor spin faster, it will draw twice as many amps instead. So, if we redo the chart for 144 volts, the amp and torque figures will double for each rpm. 

One caveat though, I think I have heard that the power output of the motor is not directly proprtional to voltage. I think I read somewhere that increasing from 144 to 156 can result in considerably more than a 12/144 power increase...?

thanks
ron


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## 3dplane (Feb 27, 2008)

Ron!Yes I think we are getting somewhere now! Say we doubled the voltage but we do NOT let the motor spin any faster how do we do that? with a larger load(prop whatever) so the amp went up therfore the motor is producing more power(VxA).And yes I think voltage increase to power in reality is not a linear thing and probably depends on many factors.That's why I rather make measurments at different conditions and plot it on a diagram then whip math out and relying on basic data.This is just my opinion though.Barna


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## ronis108 (Dec 14, 2007)

Barna, here is a post from another thread:

Most of our DC vehicles are using series wound motors, so below saturation the torque is proportional to the square of the current, and above saturation the torque increases only linearly with additional current.

What I cant figure is if it is saying double the current yeilds 4X the torque, or 4x the current and 2x the torque.

It was a good thread too!  

http://[EVDL] Who makes 3 phase AC induction motors, 20 KW and higher ? DC motor ratings ? ( 1 2)

Hmmm I inserted links before, but it isn't working for me now.


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## Dennis (Feb 25, 2008)

> What I cant figure is if it is saying double the current yeilds 4X the torque, or 4x the current and 2x the torque.



Motor torque increases as the square of the current. In other words if you double the the current, then the torque will increase by four. Keep in mind that is only an approximation...


I would like to also add that the torque curve you see for series-wound motors is true when a variable load from light to heavy is applied by the active dyno to the motor and the voltage is held constant. The torque curve will look nothing like that if the motor was hooked up to a constant torque controller. If you read my earlier post then you know how the controller is able to keep constant torque.


They same constant torque can be done with AC motors (although much more complicated to do). The Tesla Roadster for example uses a constant torque controller. Just look at the torque curve. If the motor was hooked up to 60 Hertz mains then its characteristics will be of either NEMA designs A,B,C, or D torque curves instead...


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## ronis108 (Dec 14, 2007)

Thanks Dennis. I'll look at your earlier posts. It takes time to understand some of this stuff, but I can go back to posts a week later after learning more and it all starts coming together. Or so I think! 


Thanks
ron


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## ronis108 (Dec 14, 2007)

3dplane said:


> Hey Ron!
> Your question can the motor draw 2k amps at 5k rpm? sure(if it survived)but how do you do it? increase the voltage waay higher then 72 volts.Try to forget about the controller for now .Imagine a 72 volt battery pack the size of a house (no voltage sag and unlimited amps available)and we hook this motor to it with different loads on the motor,for example different size propellers on the shaft.If our largest prop holds the motor down to the rpm on the bottom of that chart the amp draw will be the same as on that chart.Remember no controller just a huge battery.Smaller props will let it spin faster and amp draw and power will decrease UNLESS we increase voltage.Was that confusing enough? I"m just trying to put it down the way I see it Barna.


I'm still not getting what really does limit the power band of the motor. At some point the design of the motor is such that at a given voltage the motor starts decreasing draw and power drops off. What determines this speed (rpm) where at a given voltage it does not want to produce more power. I would like to run a nice cheap DC motor that will make 300 HP at 6000 rpm, and not burn up or fly apart. This would be much easier on the drivetrain than a motor that makes that power at 2500 rpm. It does not seem like DC motors are designed to do this.....Well, not at 144V anyway. 

thanks
ron


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## 3dplane (Feb 27, 2008)

Ron....Hi
What limits the power band of the motor?(as in why does power drop at high rpm?) Here is my (non professional)way of looking at it:In an ICE we have to advance ignition timing at higher rpm(if we want torque) because combustion takes time so it has to start sooner for it to reach peak pressure at an optimum crank angle.On that note i do believe that in an electric motor(brushed dc) it also takes time for the magnetic field to build up in the armature. At low rpm there is full strenght of magnetic field "shooting" out of the armature to interact with the pole shoe created magnetic field(FIELD).Hoewer at high rpm all those tiny segments of the commutator are flying passed the brushes "turning on and off" a new section of the armature rapidly,not allowing enough time to build up full flux strenght before it gets in front of the pole shoe (sort of) where it no longer produces torque.At this point it would be nice to advance the timing so we could move this armature created mag field further ahead of the stationary mag field(FIELD) for better torque.Jim Husted mentioned that he made an "on the fly" adjusting mechanism on one of his creations.So my point is I THINK besides the back emf thing that Dennis mentioned we are dealing with weaker magnetic attraction between armature and field.Since they are in series both loose strenght as the amps drop.Wich helps with rpms but hurts torque. Again this is just my way of understanding so take it with a grain of salt..Barna


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## Dennis (Feb 25, 2008)

> So my point is I THINK besides the back emf thing that Dennis mentioned we are dealing with weaker magnetic attraction between armature and field.Since they are in series both loose strenght as the amps drop.Wich helps with rpms but hurts torque. Again this is just my way of understanding so take it with a grain of salt..Barna


Yes the magnetic field of the field poles in a series-wound motor weakens, but it is not the magnetic field itself that is the reason, but it is the result of it being weaker that causes the armature to have to spin FASTER until the back emf is high enough that is brings the armature in balance with the friction of the bearings and friction of it passing through the air. However, since the armature is connected in series with the field pole coils then the result of the armature trying to create an equilibrium never occurs because each time it tries to keep the back EMF high enough for balance (same back EMF voltage), it causes the current flowing through the series field coils to be less resulting in a weaker magnetic field causing the armature to have to spin faster AGAIN to try to keep the balance. This feed back loop will continue until catastrophic failure from the armature windings flying apart into thousands of pieces occurs. 

If it is a small motor like a universal motor which is a series-wound motor in a vacuum cleaner or blender for example, then the friction is high enough to prevent such destruction.


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## ronis108 (Dec 14, 2007)

I remember reading a post by Jim on another thread where he explained how with coarser windings or something you can get mor high rpm torque, but then there are heat issues that are more likely to occure. 

I know there is blood in this turnip somewhere! Its just a matter of how and where you squeeze it

I really need to study the basics more for alot of this to make sence completely. Series, parallel, flux, etc. I don't know anything about that. I'll be back when I know more.

thanks
ron


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