Motor on VFD whines in cold weather

Bill D · Jan 21, 2017

I have my 3hp lathe motor running from a VFD. It was fine in summer. As the shop got colder it got a high frequency whine in the motor. The shop was down to 45 degrees last week and the whine is ear piercing.
It does get a little quieter after a few minutes but I should be using ear protection.
I tried changing the carrier frequency and no change. Next I will add a load reactor near the output of the vfd.
Bill D.

adama · Jan 21, 2017

Normally that means there’s something lose in the motor vibrating with the frequency, does it change note with VFD speed change? If so you need to sort it, not add some reactor, bits moving in the motor have a nasty habit of damaging the coils insulation

Does the motor have a shaft mounted fan? If so its not uncommon for them to come lose - move and rub on the fans shroud, yeah that truly can be deafening and will also come and go too

JST · Jan 21, 2017

It also can happen that a piece of swarf gets in and rubs on the fan, or the rotor, making a similar whine. And, the chip or whatever can move around, changing the tone and loudness.

A magnetic cip can really jump around and be different from hour to hour even.

I have never run into ear-piercing VFD whine. Not even on the local light rail, which seems to have a carrier of around 3 kHz for their traction motor drives.

Mark Rand · Jan 21, 2017

It might also be the oil seals on the shaft (if there are any). If so, a drop of oil on the shaft next to the seal may help.

ripperj · Jan 22, 2017

My vfd makes a whine when cold, but it is the bearings in the cooling fan. Your noise is definitely coming from the lathe?

Bill D · Jan 22, 2017

Definatley noise from the motor not lathe bearings.
Bill D.

true temper · Jan 22, 2017

Bill D, how come you never give out any "likes"?

fatoldman7 · Jan 24, 2017

My rotatory phase converter does the same thing, I posted the same question a while back in the electrical/VFD forum,

http://www.practicalmachinist.com/v...tart-up-squeal-rotory-phase-converter-299721/

Mine still works fine, despite the squeal on start up, and spin down.

30wt · Jan 24, 2017

Well, I kinda whine in cold weather too...more every year.

Bill D · Jan 24, 2017

I suppose it could be the bearings. Just the noise is so high pitched it does not seem mechanical. The motor is probably on the original bearing from 1978 or so. Shop goes 80-90 degrees in summer when all is quiet.
As to my not adding likes I do not know how to do that and I do not understand the point. I never bothered to read how to do it since I never knew why I might want to . Do you earn brownie points for having more likes? why should I care if I have nay likes or not?
Bill D.

Mark Rand · Jan 25, 2017

When I had the problem with a motor, the pitch was quite high, 4-6kHz at a guess. As I said. a drop of oil on the shaft shields/oil seals fixed it, once it had wicked in. If the motor hasn't got a shaft seal and it's got plain bearings, then they could probably do with a drink.

Bill D · Jan 25, 2017

From your description it may be bearings then. It does not have the low frequency rumble I associate with bearings going out. It is a Brooke Compton motor which is supposed to be a good make. New enough to be cast aluminum not cast iron so probably ball bearings not sleeve. I will try to get some oil on it this weekend.
Bill D.

feets · Jan 26, 2017

I have noticed that my American Rotary phase converter howls a bit when shop temps are in the 50s. Once it has 4 or 5 minutes run time the motor quiets down and runs like it should.

The converter is 6 months old and gets used maybe a few hours every couple weeks.

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Motor on VFD whines in cold weather

Bill D

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adama

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JST

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Mark Rand

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ripperj

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Bill D

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true temper

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fatoldman7

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30wt

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Bill D

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Mark Rand

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Bill D

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feets

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