I'm trying to reduce noise on my water bin dump water pump...
I installed a VFD this morning. Had to remove it immediately because the
pump motor got a new high pitch squeal. Anybody know why a VFD would do
that? More importantly, how could you stop it?
The drive generates a pulse width modulated sine wave - you're hearing
the carrier frequency. Most drives allow you to adjust the frequency.
Lower is better for the motor, but doesn't always fix the noise. A
higher frequency setting will move the noise out of the audible range,
but the switching transients may be harder on the motor.
Are we talking about a squealing bearing sound, like really loud? Or is
it just a whistling sort of noise? Assuming you are running the motor
at the correct RPM (60 Hz) then the only logical thing it could be is
acoustic output from the PWM frequency of the VFD. Some models have a
choice of frequencies available, try changing it. If it really is a
bearing squeal, ie. really loud, then make sure you are running at 60
Hz. If that is right, then maybe the bearings are bad or the windings
have a short, and current is going through the bearings. If the motor
frame isn't grounded, check for a shrt to ground and then ground the frame.
No, the VFD was no help at all. I tried 30 45 and 60 HZ. Not enough flow at
the lower settings and no noise reduction at all. Plus I got this new squeal
from the carrier frequency. Back to the drawing board. main crop starts next
week, there's no more time for a month. I got something to think on.
I think I'll shop eBay for a submersible three phase pump motor. Bruce's
suggestion would have no noise at all.
You need the volute and prop to fit BEFORE you buy the motor, so you
know which motor you need - unless you want to mill it from scratch.
And it's probably still going to be 1/2 HP just a different (and
much quieter) form factor.
Does the VFD allow you to change the carrier frequency? Often the problem is
the motor windings mechanically resonating at some harmonic of the VFD
switching frequency. Sometimes, it's adjustable to a frequency that doesn't
cause the problem. Sometimes it's adjustable to the point where us old farts
can't here it any more :-)
I've had to do this on all three of the VFD drives I've set up so far.