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?

Karl

On Tue, 16 Sep 2008 10:36:51 -0500, "Karl Townsend"
wrote:

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.

--
Ned Simmons

Karl Townsend wrote:
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?

Karl


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.

Jon

On Tue, 16 Sep 2008 10:36:51 -0500, Karl Townsend wrote:

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?

Karl

So, aside from the noise did it work better? In other words, are you
half way there?

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

So, aside from the noise did it work better? In other words, are you
half way there?

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.

Karl

On Tue, 16 Sep 2008 12:12:19 -0500, "Karl Townsend"
wrote:


So, aside from the noise did it work better? In other words, are you
half way there?

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.

-- Bruce --

On Tue, 16 Sep 2008 10:36:51 -0500, "Karl Townsend"
wrote:

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?

Karl



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.


Mark Rand
RTFM

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.

I guess I'm lucky. I know a machinist that can make ANYTHING adapt. I
cruised eBay today, not a single offer. I may have to look for this motor as
a repair part.

karl

On Sep 16, 3:54*pm, "Karl Townsend"
wrote:
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.

I guess I'm lucky. I know a machinist that can make ANYTHING adapt. I
cruised eBay today, not a single offer. I may have to look for this motor as
a repair part.

karl

Exactly what rpm range are you looking for in the prop? Are you
serious about the submersible motor? Will your situation allow a "V"
belt drive?

Paul

On 2008-09-16, Ned Simmons wrote:
On Tue, 16 Sep 2008 10:36:51 -0500, "Karl Townsend"
wrote:

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.

And the noise itself is no sign of danger to the motor, so you
did not need to pull it off immediately.

Good Luck,
DoN.

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