One could get some dope or varnish and drip into the area
and re-coat the fins into a firm position. Might be an insulation
sheet that is hard with varnish - shaking and making noise.

Martin

On 8/21/2013 1:39 AM, PrecisionmachinisT wrote:
"DoN. Nichols" wrote in message
...
On 2013-08-20, Pete Keillor wrote:
On Mon, 19 Aug 2013 18:02:08 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

Karl Townsend fired this volley in
:

Anyway, should i pop for a reactor? I've bought from automation direct
before with good results.

If the squeal is coming from the motor itself, the reactor(s) will help
smooth the 'simulated sine wave' coming out of the inverter drive.

I think that the squeal is likely from loose laminations in the
stator of the motor -- and likely just right to be resonant at the
default frequency of the VFD -- so a change in frequency would likely
make a big difference. (An alternative is to force a varnish into the
laminations -- but be sure to pick one which will not attack the
varnish/enamel on the wires wound on there.) Maybe a very thin epoxy
would work.

A reactor might reduce the high frequency part getting to the
motor windings -- but is otherwise unlikely to be necessary.

A replacement motor will likely not show the same problem --
even if the same brand. But it might be the most expensive approach.


My impression has always been that the PWM frequency was simply too low on
first-generation inverters; and that while anything built within the past
couple decades might well still create some annoyong electrical noise,
acoustic emmissions will be at a frequency substantionally above the human
hearing threshold