Electric motor NVH
Electric motor NVH
(OP)
In gathering data to characterize noise and vibration in electric motors, I'm having trouble understanding some spectrogram features. The sharp vertical lines seem to behave very similar to pwm harmonics (see pic). They are flanked by sloped lines at multiples of twice the fundamental mechanical speed (f+-n*2*fm). This particular motor is an 18 slot / 12 pole PMSM, being driven up to 55Hz. The plot was made from acoustic pressure; the lines are apparent in accelerometer data as well.
The PWM switching frequency is 16kHz.
These lines are quite sharp and occur across the full operating range of the motor at multiples of ~4kHz.
Could these be pwm related?
Any other ideas as to what would produce these vibrations? An artifact of the DAS?
The PWM switching frequency is 16kHz.
These lines are quite sharp and occur across the full operating range of the motor at multiples of ~4kHz.
Could these be pwm related?
Any other ideas as to what would produce these vibrations? An artifact of the DAS?

RE: Electric motor NVH
Cheers
Greg Locock
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RE: Electric motor NVH
https://www.bing.com/search?q=PWM+switching+freque...
Does your DAS have antialiasing filter?
Walt
RE: Electric motor NVH
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(2B)+(2B)' ?
RE: Electric motor NVH
You couldn't wind that for three phase in the way I'm used to seeing for traditional induction / synchronous motors.
Are there three phases supplied to the motor, or some other number of phases?
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(2B)+(2B)' ?
RE: Electric motor NVH
I believe there's an antialiasing filter built in to the DAS. Data were sampled at 25600, so I think it's unlikely aliasing would produce n*4k lines anyways.
E/m isn't exactly my specialty, so I'm not sure what you mean by the motor configuration. It's three phase AC, 18/12, concentrated windings. They are designed and built here.
RE: Electric motor NVH
Perhaps try creating a fake PWM signal and do an FFT on it?