My biggest fan is a right pain in the ear... High frequency noise from HVLS fan

[Jackster]

Just installed a HVLS fan in my workshop and while the performance of the fan is great, there is an annoying high pitch noise coming from either the motor or the controller.



As you can see, around 14kHz there is a nice line. I have isolated it in audio software and it is the same pitch as the noise when walking around my factory.
The noise comes and goes as you walk around and just tilting your head down can make it go away.
You can only hear the noise when the fan is moving or starting. When idle, there is no noise.

Here is the motor controller board.


Any thoughts on what could be causing this and how to fix?

[uer166]

14 kHz sounds like the motor controller frequency: the noise is coming from the fan windings/laminations. Not much you can do other than get a different motor controller that works at a higher F.

[Jackster]

Would some ferrite beads on the controller to Motor wires and a EMI filter on the AC input be of any use?
Ideally I don't want to go messing with another controller. Did not work out well last time I tried to program one...

[moffy]

Well I guess the motor controller converts single phase into 3 phase out, but I can't see any power switches such as IGBTs etc. If 14kHz is the PWM frequency, sounds reasonable(no pun intended), then you could well get lamination noise. Ferrites won't be effective at such relatively low frequencies unless wound into largish inductors. The solution would be to filter the 3 phase output with a suitable LC filter to remove the PWM component.

[Jackster]

Well I guess the motor controller converts single phase into 3 phase out, but I can't see any power switches such as IGBTs etc. If 14kHz is the PWM frequency, sounds reasonable(no pun intended), then you could well get lamination noise. Ferrites won't be effective at such relatively low frequencies unless wound into largish inductors. The solution would be to filter the 3 phase output with a suitable LC filter to remove the PWM component.

There is a large heatsink in the rear of this board. Would guess they are on the rear of the PCB.

[amyk]

Has the stator been dipped in varnish?