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Joined: Oct 2003
Posts: 172
G
Member
We have recently installed vfd's in exixting circuits and now one of the motors has burned out and they are blaming our VFD. The vfd s are not even programmed to do any control as of yet just off and on.
Can it be the VFD the controls company is saying that our VFD's are causing a voltage across the bearings?

Joined: Jul 2004
Posts: 9,688
Likes: 10
G
Member
What is the motor driving? Is there any chance voltage is getting transferred to the motor shaft?
I really don't see this being a VFD problem.


Greg Fretwell
Joined: Mar 2004
Posts: 947
T
twh Offline
Member
That isn't logical.

However, blaming the competition for everything from bearings to bad weather is quite normal.

Joined: Aug 2006
Posts: 81
A
Member
I vaguely remember reading something about this in a trade magazine (maybe EC&M). As I recall, it has to do with current spikes from the VFD's output inducing a voltage on the motor shaft via the windings, and the current arcing across the bearings and burning them.

Joined: Aug 2006
Posts: 81
A
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Joined: Apr 2002
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Thanks Albert

Another timely subject! Got a call this afternoon regarding a sewage lift station pump/VFD/panel meltdown, on a 'fairly new' install. That's Mondays problem child. This PDF may be interesting reading.



John
Joined: Jul 2004
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G
Member
interesting stuff. Surprised me.


Greg Fretwell
Joined: Aug 2007
Posts: 853
L
Member
I recall this conversation not too long ago.

Wait For RENO Or Frenchelectrician. I believe they have the skinny on it.

Yes it did have something to do with induction.

Joined: Jul 2004
Posts: 9,688
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G
Member
I think the real answer is the EMI filter mentioned in the article. I would be surprised that a decent VFD wouldn't have that, just for FCC compliance.


Greg Fretwell
Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
Thanks for the vote of confidence ... but the issue is beyond my experience.

I've only seen bearings damaged by current flow, either through a fault condition, or when someone did some welding on the machine.

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