ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
600 KW 120/208 3 Phase Y protection
by Yooperup. 07/24/17 12:20 PM
1913 American Electrician's Handbook
by gfretwell. 07/20/17 01:08 PM
Green House wiring
by ghost307. 07/20/17 09:10 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,318 Are you busy
174,785 Re: Forum
167,155 Need opinion
Who's Online Now
0 registered members (), 70 guests, and 11 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#218450 - 05/03/17 12:44 AM Danfoss VFD shuts down motor showing Ground Fault  
Potseal  Offline
Member
Joined: Feb 2013
Posts: 236
Saskatchewan
Now that the local temp is getting consistently warm the guys at work are trying to start-up the cooling towers for a hospital. One of the motors for a pump runs for about 10 mins. and then shuts down on ground fault as seen in the display on the Danfoss VFD that is controlling it. Since it takes roughly ten minutes after the pump motor starts for this ground fault to occur I suspect it must be the motor insulation. So far we've tested the conductors between the motor and the VFD with a Fluke 1507 megohmmeter and they appeared to be fine. Tomorrow we will test the motor. Anyone have other suggests or experience troubleshooting Danfoss VFD's? Thank-you.

Last edited by Potseal; 05/03/17 12:45 AM.

A malfunction at the junction

Work Gear for Electricians and the Trades

#218453 - 05/03/17 08:02 PM Re: Danfoss VFD shuts down motor showing Ground Fault [Re: Potseal]  
Potseal  Offline
Member
Joined: Feb 2013
Posts: 236
Saskatchewan
It appears the problem has been resolved. After meggering the conductors between the motor and the drive and then the motor leads themselves we did not discover any potential issues. Since there is an identical drive and motor right next to the the ones we were having problems with we decided to try running the motor with the second VFD. Using a temporary feeder of 3C #6 Teck cable we ran it from the second drive to the motor. The motor ran without shutting down for 30 mins. Since this temp. cable was in place, and despite meggering the existing conductors, we thought we'd use the temp. cable to feed the motor in case our megger test didn't find an issue the existing. While connecting the temp. Teck cable we discovered the ground terminal on the VFD was loose - maybe the real problem? Ran the motor without issue with the temp. cable for 30 mins. and then reconnected the old cable and ran the motor again for 30 mins. without any shutdowns. A loose ground terminal at the drive appears to have been the original problem.


A malfunction at the junction

#218491 - 05/15/17 04:51 PM Re: Danfoss VFD shuts down motor showing Ground Fault [Re: Potseal]  
jraef  Offline
Member
Joined: Jul 2004
Posts: 101
San francisco, CA, USA
A ground terminal that was loose could create a situation where common mode noise in the motor leads has nowhere to go until it suddenly does, which to the residual ground detection system within the drive briefly appears to be a current flow mismatch. Good find.


JRaef


Member Spotlight
electure
electure
Fullerton, CA USA
Posts: 4,260
Joined: December 2000
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.011s Queries: 15 (0.002s) Memory: 0.7539 MB (Peak: 0.8796 MB) Zlib enabled. Server Time: 2017-07-25 06:49:43 UTC