Remember that there are sub harmonics being generated as well.
Martin

On 8/21/2013 11:27 AM, Bob La Londe wrote:
"PrecisionmachinisT" wrote in
message ...

"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

I don' know what the total range of human hearing is, but when I was
younger I could hear or be aware of frequencies upto about 20kz.
Depending on the sound generator somewhere between 19.5 and 20.5 I would
notice it go substantially silent. Now as I have gotten older I have
noticed that I can't hear much above about 17.5.

Anyway, the range of human varies with age, and does so noticeably with
men in the high frequency range. Also, its possible that some people
have a wider range of hearing atleast at the peak level of their
physical development. All of that being said, who knows what odd
frequencies can be generated by a VFD.

Hmmmm... I'm not sure any of that makes a point, but its some nice
anecdotal information to consider. LOL.