VFD with 3 ph motor noise

KenH

Well-Known Member
Hello all - this is something I've read other posts on, just not found them with searching. Seems like TimGunn had some good ideas? Anyway, The existing Ironhorse 2 hp, 3 ph, 3500 rpm motor I've been using for several years started giving error codes on a Huanyang Model #HY03D023B VFD. The error code indicated acceleration over current, or something wrong with motor. There had been a light rattle sound for several months which made me think bearing going bad. The grinder would run for 10 minutes, and sometimes only a minute or so. I ordered a new Ironhorse 2hp 3 ph 3500 rpm motor as replacement. Now runs without error codes - so far anyway. The problem is the "knocking" sound at low rpm, 300 to 900 rpm it can be pretty loud, by 1500 rpm not so loud, and by 2000 rpm it's almost not heard at all.

This is the same VFD I've been using for several years and been so happy with how smooth the motor ran, from 300 rpm to 3890 rpm (over speed a bit). Do I have a bad motor? OR, is it a setting in VFD? Here's a 40 second video showing the sounds and motor. The display on VFD isn't very clear at all, and the image is reversed for some reason and I've not yet found how to flip it.

After doing much research it seems this is called "cogging" in a motor. seems like it can be caused by harmonics that cause currents thru bearings from stator winding, of which the VFD has plenty of harmonics. Seems like there was a suggestion to set a parameter that moves the freq around to help prevent those issues. Then I read "the current source inverter (CSI) and voltage source inverter (VSI) designs most often result in cogging, while the pulse-width modulated (PWM) type does not." The drives we use are PWM type.

I called AutomationDirect tech support (IronHorse supplier). The tech said he was not familiar with that type of problem, but since I've tried 2 different VFD drives on the new motor, and the old motor didn't have the issue, there must be something wrong with the motor. They are shipping a new replacement motor. I'm very happy with AutomationDirect's handling of the problem. Boy, I sure hope that fixes the problem.

A few minutes ago I got a tracking number from AutomationDirect where they have shipped motor - FedX says scheduled delivery is July 2nd! Amazing that fast.

OK, more info - while waiting I took old motor apart and it seems the rear bearing was a bit "loose" - it had a tiny rattle when spinning by hand. I replaced bearing and now the motor is running smooth with the old VFD. Right now it's running good - smooth at least. I won't know about tripping on error codes until I've used it some. I think I'll button it up now and do a bit of grinding - getting metal strips ready to put into a billet.

OK, that's been my chores for the last couple of days now.

Ken H>
 
An update - did a bit of lite grinding this morning with the old repaired motor and old VFD. Old motor runs smooth, but still have some issues with tripping with the VFD. I planned to swap new VFD to see how it worked with old repaired motor, but FedX delivered the replacement IronHorse motor. Installed new motor to old VFD drive - runs smooth, did some grinding with no trips. Not sure how long this will last, but at least the new motor is running smooth. I think the "cogging" problem was with the old motor.

I must give AutomationDirect a big "attaboy" for their service - they FedX'd the replacement motor with overnight service.

Later
 
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