PWM motor noise

Nov 17, 2005 2 Replies

Hi all, bought a PWM kit (

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), but put in an IRF840 & a 630V .1uF cap to run a 108VDC (nom) motor with rectified/filtered line voltage (~160VDC). The motor makes a rather loud (pwm) noise when running, is this normal? Any way of quieting it down? Yes, I know I shouldn't be rectifying mains, but this is a test & I'll use a stepdown/ isolation Xformer if & when it's working well. TIA! Bart


High pitched at low speeds,and it gradually gets higher pitched at faster speeds? Pretty normal.

What is the PWM frequency? An IRF840 should be able to switch well above audible frequencies. You might be able to turn the PWM frequency up by changing a resistor or capacitor.

Jon

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