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Old 04-01-2014, 02:06 PM   #6375 (permalink)
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Originally Posted by MPaulHolmes View Post
By the way, I'm planning on running it at 8KHz PWM, which is audible. If it turns out to be a problem, I'll have to go with software PWM, and spread spectrum switching. It's just that the IGBTs are so big, that they really can't switch all that fast. But if you have software PWM, then you can have the pwm frequency spread over a range of values: 7.800 kHz, 7.801kHz, ... 8.200kHz, etc.. At this point I don't know how much the frequency has to vary for it to be effective.

Hmmm I'm a little worried, a continuous 8000Hz is one piercing tone:
Square Waveform | Online Audio Wave File Generator
I guess we will have to wait and see how it actually sounds.
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