Megging a motor

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devonhilburn21

Joined Jan 14, 2021
1
I need help. I have a dura pulse gs3 VFD on a 3 phase 480v 3 phase 9 wire motor. VFD trips on ground fault every now and then. It may trio every other time the motor kicks on or every tenth time, it just varies. I’ve isolated my line and load cables to the motor and ran insulation test, all good. Now to the motor. Disconnected all 3 line wires, ran test and got .1 megohm on each phase to ground. Then isolated every wire (disconnected 4-7, 5-8, 6-9 and of course line wires). I get 550 megohms on each phase to ground. Is this motor bad? Is the VFD bugging out? Any help is appreciated.
 

Deleted member 440916

Joined Dec 31, 1969
0
Anybody got a Xtal ball to know what disconnected 4-7, 5-8, 6-9 means ?
In fact come to think of it I don't know how any of it is connected, some clarity would help.
 

MaxHeadRoom

Joined Jul 18, 2013
23,084
I need help. I have a dura pulse gs3 VFD on a 3 phase 480v 3 phase 9 wire motor. VFD trips on ground fault every now and then. It may trio every other time the motor kicks on or every tenth time, it just varies. I’ve isolated my line and load cables to the motor and ran insulation test, all good. Now to the motor. Disconnected all 3 line wires, ran test and got .1 megohm on each phase to ground. Then isolated every wire (disconnected 4-7, 5-8, 6-9 and of course line wires). I get 550 megohms on each phase to ground. Is this motor bad? Is the VFD bugging out? Any help is appreciated.
Try lifting any ground referenced wire off of the motor frame just to prove it, although if connected mechanically to a grounded machine mechanism, it may be difficult to achieve?
Max.
 

GetDeviceInfo

Joined Jun 7, 2009
1,845
your phases look good, so megger each point of reconnection, back to the VFD. Your problem will lie between your .1M reading and your 550M phase readings. Burnt / cracked terminal block?
 

Hymie

Joined Mar 30, 2018
976
I have seen VFD motors that normally have a high earth/ground current – you could give consideration to changing the GFI to one of a higher trip current.
 
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