Lm versus magnetizing current! 1

[zolka]

Helo everybody!
I made a generalized AC motor model in matlab (simulink), I’ve run the simulation on different 3 phase motors (1kw 2.2kw ,7.5 kw, 22 kw) and the difference between the calculated and simulation results are 5-10% (Tpullup,Tpullout,Istart,Irated,Speed)!I figured out that the error is due to Lm,Llr,Lls change during runup!Inductance drops 20-30% at saturation!
I’ve tried to estimate the inductance change, but the results are even worse compared to that when the Lm is constant!Now I’m looking for a motor which has an Lm versus Magnetizing current curve!Without that I’m not able to finish off my model!
I’m asking if anyone of you have such a motor with the necessary parameters please help me!?Or if You know how to determine the Lm drop please let me know!
Thanx in advance!

 

[sreid]

Google "Iron Permiability Curve" The permiability curve is very non linear and a drop off in inductance of 20-30% at high current levels would not be unusual. Also, the motor "Teeth" carry higher flux density and will tend to saturation first which makes the nonlinearity worse.