# How to Extrapolate Motor Data?



## major (Apr 4, 2008)

Hi Adam,

I have addressed these questions numerous times on the forum. Did you search? Anyway, I'll give you some short answers.



adamj12b said:


> My questions are:
> 
> 1. Is torque a product of wattage, or just amperage? My logic tells me that torque is equal to the wattage going through the coils. For example: the Warp 11 shows 10 ft.-lbs. of torque at 96.8A and 72V, which is 6.97KW. To achieve the same wattage at 149V, the amperage would be 46.8A. If this is correct, that would mean that at 218.8A and 149V, you would have the 135 ft.-lbs. of torque, And 452.8A would yield 279.4 ft.-lbs. of torque.


This applies to series motors.

Torque is proportional to current. Often called a torque per amp. At a given current, torque does not vary with voltage or RPM.



> 2. They show on the graph that the H.P.e (electrical horse power) is 9.3 at 72V and 96.8A. Next to that, They show H.P.m (mechanical horse power?) being 7.5. How do I calculate this?


HPe is input power to the motor. Volts times Amps.

HPm is output power from the motor shaft. Torque times speed.

Motor efficiency is output power divided by input power. Eff = HPm/HPe * 100%.



> 3. On the graph, it shows at 10 ft.-lbs. and 72V, the RPM of the motor is 3919. I understand that increasing the voltage will also increase the RPM, but how do i compute the higher RPM? If I double it, due to twice the voltage, the RPM is over the motors rated 5500 RPM....Im confused on what to do here.


At a given load (torque or current) on the graph, the change in RPM will be reasonably close to the change in voltage applied to the motor.

Like I said up top, I have expanded on this several times and given examples. The search function works pretty well here. Look for things like motor performance, motor characteristic, speed torque curves, voltage ratio, etc.

Here's one I found http://www.diyelectriccar.com/forums/showthread.php/electric-motor-output-wrt-voltage-32492.html

Regards,

major


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