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Wormnhaque
Participant

Join Date: Jun 2008
Posts: 4

Transformer Defects

06/12/2008 2:45 PM

Hey all,

We have an VVVF Transformer in a new Production line which failed already three times.

One phase of the secondary wiring was burned in all the time. And the strange think is, that the transformer was at the last time energized but not loaded all the time.

Data: 11kV/690V; 500kVA; delta/ star (without neutral).

Who knows what reason that could be?

Thanks

Wormnhaque
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Nagarajan.Suresh
Associate

Join Date: Jun 2008
Location: Chennai
Posts: 31
#1

Re: Transformer Defects

06/13/2008 2:28 AM

Hi,

This little bit misleading since you Trafo. secondary is and without neutral. The neutral shall be solidly grounded.

A floating neutral may cause circulating current and it is so natural that the winding will burn.

N.Suresh

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 N.Suresh
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Wormnhaque
Participant

Join Date: Jun 2008
Posts: 4
#2
In reply to #1

Re: Transformer Defects

06/13/2008 7:20 AM

Hi,

Well the transformer is for frequency converter Panel and these transformers never (what I saw) have neutral outside.

BR

Wormnhaque
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Anonymous Poster
#3

Re: Transformer Defects

06/13/2008 11:15 AM

You need to attach some sort of voltage and harmonic on-line measurements .To burn a winding while on no load, whew!!!!!

Was the transfoemr from the sme manufacturer?

Did you get a test report after factory test?

can it be that you have a phase resonant condition?

Your application is unique: I assume that VVVF means variable voltage variable frequency.
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