My washing machine's motor controller does an interesting thing between 15kHz and 16kHz as it changes the spin speed. #UltrasoundInAirpic.twitter.com/kmlAcjPHA1
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Just the switching frequency? It will be louder when changing speeds due to higher torque.
Look at those sidebands spreading out as the speed changes though. It's both amplitude *and* frequency modulated. I'm guessing an inverter with 3-phase AC output, internally switching at a fixed frequency and changing the AC output frequency.
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Yeah, that's actually the most common way to implement a brushless motor drive. I've designed such a drive before, but I never actually looked at a fft of the output under changing load.
Thanks. Twitter will use this to make your timeline better. UndoUndo
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