On Wed, 21 Aug 2013 13:44:08 -0400, Spehro Pefhany
wrote:

On Wed, 21 Aug 2013 09:27:40 -0700, "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
news:j465191dquf4r4bm749ff44husbamrap90@4ax. com:

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.


Female voices are predominately high frequency.

Men, as we age, tend to lose our hearing at high frequencies first.

Coincidence?

Survival.


"There are no leftists in mainstream American politics.

Just two right wing parties, one hard right and one softer."
Christopher A. Lee, 8/18/2013