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Induction Motor Time Constants


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#1 kada

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Posted 21 November 2008 - 10:01 AM

Hello!
I guess there is a lot of challenges in motor control area for EV platforms. Vector control of Induction motor (IM) supplied by Voltage Source Inverter (VSI) is quite mature and well described strategy. The performance of all the AC drive depends strongly on IM parameters. The designers and manufacturers of IM for EV tend to have motor as small as possible with very low inductances. It implies in very small time constants. IM acts as a weak Low Pass Filter (LPF) for the stator currents when supplied by pulse PWM voltages.
In short - current is very dirty, noisy, hairy when comparing to standard IM (even for 20kHz PWM).
Has anybody come across similar phenomenon?
We can increase PWM, ask IM designer to consider higher inductance. Or are there any tricks?

#2 marke

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Posted 21 November 2008 - 06:20 PM

Hello Kada

The real question to ask, is "is it a problem?"
If the current is not a perfect sinewave and has some noise on it, does it affect the performance or is it just a cosmetic issue.
At worst, it may increase the losses in the IM a little, but tweaking the design of the IM will also increase the losses so are you any better off?

Best regards,
Mark.

#3 Nanda

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Posted 27 September 2011 - 11:08 AM

Hello, i read your post about Electric Vehicle...i want to ask you about the controller. for VFD Control Method, which one the best method for control induction motor 3 phase because i'm working on EV know for my project. thank you....




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