Re: induction machine inductance calculations

I suppose that you want to calculate rotor current, stator current for any speed is a data for me. To calculate phase rotor current for any speed you have to simulate with frequency, you have to take into acount slip for frequency in your problem, your frequency will be f=slip*frequencystator and you will obtain rotor current and torque for this speed. But there is a problem with harmonic problems, these are lineal, if you have non-lineal material femm take permeability lineal althoug you define non-lineal permeability.

Hello Alberto,

Sorry for answering late but I was not at my office for a couple of days. Actually I'm trying to learn to analyze induction machine so I didn't do anything about harmonics yet. But I think an old book about induction machines may help you for the theoritical approach.

1) "Theory and Design of small induction motors" CYRILL G. VEINOTT, 1959.

Also Mr. Lipo has a book about machine design.

2) "Introduction to AC machine design" T.A. Lipo, 1996. I hope these books will help you.

And I would like to know how to analyze the harmonics by FEMM. Also I have another question. If I want to obtain torque speed curve how can I do this with FEMM? Because if the speed changes, then the current (and the current densities) changes also. For any speed how can we calculate the phase current? Thanks.

Best Regards,

Erdal Bizkevelci

---- Original Message -----

From: Alberto Perez

To: Erdal Bizkevelci

Sent: Monday, November 19, 2001 12:05 PM

Subject: Re: induction machine inductance calculations

Erdal Bizkevelci <erdal.bizkevelci@xxxxxxxxxxxxxxxxxx> escribió:

Hello Alberto,

I'm trying to analyze indution motors, as you do, but have some hesitations about calculating leakage and magnetizing reactance. I think that if we define frequency as 50 Hz, then we calculate locked rotor parameters, of course this means leakage inductance. If we define f = 0 Hz, then integrating all problem area's magnetic energy, we can use this value to calculate no load parameters, so the magnetizing inductance. Is this approach is true or not? Thanks in advance.

Erdal Bizkevelci

Hello Erdal,

I have calculated magnetizing reactance with f=0Hz as you and the values of the motor that I have obtained are very similar to the values of an analytical program that use for design of motors. I don't calculate leakage inductance, but I think method's leakage isn't equal to magnetizing with f=50Hz, I tnink in this case you calculate magnetizing reactance for 50Hz. I think to calculate leakage reactance you have to calculate the flux that does not concatenate between slots stator and rotor but I don`t know if possible with femm.

Do you know about harmonics of flux in the airgap? I'm trying calculate harmonics with Matlab from the results obtained from femm results of femm, but the results aren't correct.

Thanks in advance

Alberto

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