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mwadym
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Join Date: Jul 2010
Posts: 7

Current Leakage in Control Circuit

09/01/2010 12:26 PM

We have installed 1 no. MCC (Motor Control Center) Panel with 4 nos. VFD drive (200kW, 415V, 50Hz) and other control circuit for smaller pumps. When running this VFD drives, there is a current leakage in the control circuit which resulted to dim light occurred at the indication light. I mean this indication lights are for other control circuit which is not running and shouldn't light-up. When measured the voltage (line-earth), is about 6V. Just need experts advise on how to solve this problem. Thanks
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JRaef
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#1

Re: Current Leakage in Control Circuit

09/01/2010 1:45 PM

Could be any number of issues, but the most likely one is that you have run the output conductors of the VFDs with unshielded (unscreened) conductors and they are acting to induce voltages on other conductors in the same environment, mainly the wire ways of the MCC. If that is the case, rewire your VFD outputs with shielded cable or completely separate them from any other wiring.

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LAA_Lucke
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#3
In reply to #1

Re: Current Leakage in Control Circuit

09/02/2010 6:11 AM

GA from me.

The VFDs must be properly earthed and the output cables screened. High frequency broadcasting unto the adjacent wirings can be picked up ...
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mwadym
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Posts: 7
#4
In reply to #1

Re: Current Leakage in Control Circuit

09/02/2010 8:57 AM

Hi JRaef, what do you mean output conductor of the VFDs? Is it the power cables from VFD to Motor terminal?
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JRaef
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#5
In reply to #4

Re: Current Leakage in Control Circuit

09/02/2010 11:27 AM

Yes.

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mwadym
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Join Date: Jul 2010
Posts: 7
#6
In reply to #5

Re: Current Leakage in Control Circuit

09/02/2010 11:35 AM

From MCC (VFD Drive), we are using 3core armored cable where the armored is connected to the earth. At MCC side, armored connected to earth bar inside the MCC and connected to earth pit. At Motor side, armored connected to Motor body and also connected to earth pit. Is there any other ways of better earthing connection?
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MalcolmK
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Location: UK
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#7
In reply to #6

Re: Current Leakage in Control Circuit

09/02/2010 4:48 PM

It seems likely that the coupled pickup could be inside the MCC or from the supply side. Check proximity of the lamp cabling to either the motor or supply side unshielded cable within the MCC as a first check. Double check the armouring continuity to the motor earth in case of local isolator etc but I suppose the armour is your earth connection at this size?

Does the lamp cabling run with VFD cabling (input/output) for any distance anywhere allowing such pickup to happen?

Does the VFD have a supply side RF filter?

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ikhanuk
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Join Date: Aug 2009
Posts: 91
#2

Re: Current Leakage in Control Circuit

09/01/2010 3:31 PM

Hi There

1- Check for proper harmonics filtering

2- check the neutral sizing

3- Check the wiring there may be a isnulation faliure

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Joe Sparky
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Location: New Zealand
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#8

Re: Current Leakage in Control Circuit

09/03/2010 2:03 AM

I do not completly understand your problem, but if it is leakage to earth that is your concern then I would suggest that you disconnect the EMC Filters from the VS Drive earth.

We wire a lot of portable pumps controlled by VSD's and these are pluged into circuits protected by RCD Circuit Breakers, we used to get a lot of tripping of the RCD Breaker until we disconnected the EMC Filters from the earth.

Cheers

Joe
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Users who posted comments:

ikhanuk (1); Joe Sparky (1); JRaef (2); LAA_Lucke (1); MalcolmK (1); mwadym (2)

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