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Joined: Oct 2003
Posts: 172
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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?
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Joined: Jul 2004
Posts: 9,931 Likes: 34
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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
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Joined: Mar 2004
Posts: 947
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That isn't logical.
However, blaming the competition for everything from bearings to bad weather is quite normal.
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Joined: Aug 2006
Posts: 81
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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.
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Joined: Aug 2006
Posts: 81
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Joined: Apr 2002
Posts: 7,382 Likes: 7
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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
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Joined: Jul 2004
Posts: 9,931 Likes: 34
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interesting stuff. Surprised me.
Greg Fretwell
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Joined: Aug 2007
Posts: 853
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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.
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Joined: Jul 2004
Posts: 9,931 Likes: 34
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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
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Joined: Jan 2005
Posts: 5,445 Likes: 3
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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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Posts: 57
Joined: August 2003
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