How to calculate the dimensions of an interior permanent magnet motor given it's torque speed profile?

Question

Hi I'm a mechanical engineering graduate student working in the area of hybrid electric vehicles. My knowledge in electric machines isn't very good, as I've only recently started taking courses on them. We are trying to design a hybrid car in our university and we have been able to calculate the optimum torque-speed profile for the vehicle but would like to know how big and heavy it would be to see if it would fit properly in our car. Even if you provide correlations that give approximate answers, it would be fine, although we would like higher accuracy. The torque speed profile looks like this - the highest torque T1 is obtained from 0 rpm to N1 rpm where the torque is constant and power increases. Form N1 rpm to the max. rpm the torque decreases in inverse relation to speed providing constant power. My question - are there correlation available to calculate motor dimensions and weight from T1, N1 and max rpm?

Answer 1

You're seeking a "formula" to calculate the size given a couple of rating numbers. I'm afraid there is not one person who can answer your question.

Your best bet is to contact some manufacturers or at least check out websites and online catalogs to figure out the best motor for your application. You will find that there are a number of motors which may meet your requirements. You can select the one with most favorable dimensions.

Answer 2

Not the magic bullet answer you're looking for, but you may want to try talking with the engineers here and at other motor manufacturers, found by Googling "motor sizing": http://www.orientalmotor.com/support/mtr...

Answer 3

I don't think you will get a satisfactory answer to this.

Answer 4

For estimating purposes, I think that you can start with the dimensions of a standard 3-phase induction motor with a horsepower rating equal to your constant power rating and a speed equal to your N1. The increase in RPM above N1 should not affect the dimensions very much. I have looked at a technical paper that suggests that the maximum RPM for constant power operation of an IPM motor can be as much as 7.5 times N1.

You can find standard motor dimensions in the NEMA motor standard MG1.  A condensed version is available as a free download:

http://www.nema.org/stds/mg1condensed.cf...