Excessive Heat Primary Delt-Wye, WHY?
Excessive Heat Primary Delt-Wye, WHY?
(OP)
We have burned up two 330kva Isolation Delt-Wye 480v transformers. Both transformers had the same primary winding burn up and all other windings were fine. We notice that the xformers would get really hot and then at time run normal temps, the heat was only on the phase a transformer and only on the primary side. The transform only supplies one DC drive and one 250HP motor. We see no problems with voltages and amps. we megged out primary and secondary sides. we did find one phase of line side wiring to be 47mohms compared to the other phases being 2000plus mohms. we have corrected this but the heat issue is still there. what could cause such a problem?






RE: Excessive Heat Primary Delt-Wye, WHY?
TTR?
RE: Excessive Heat Primary Delt-Wye, WHY?
motor windings megged out the same as should be around 40mohms across the armatures to ground.
We believe possible fault maybe comming from the Drive, we have an older relience MAXPac DCVS. seems that all Triac are firing, could loosing a triac or or a phase cause the overheating on the primary side of the Delta WYE transformer?
RE: Excessive Heat Primary Delt-Wye, WHY?
It seems that there is some kind of drive (eg. VFD) between the transformer and the motors.
The only way I can think is that the DELTA winding may get heated up due to third harmonic current circulation inside the DELTA winding which may be injected from the secondary side.
1)Could you please post a copy of the SLD depicting the power distribution?
2)Is the WYE side secondary is grounded?
3)Have you ever conducted a harmonic measurement on the secondary side?
Thanks
RE: Excessive Heat Primary Delt-Wye, WHY?
1) I will try to figure out how. Delta to Wye no ground.
2) The wye side secondary is NOT grounded
3) we have looked at the output of the Drive and the wave does not seem to have harmonics. As a matter of fact what we did see however was that the DC ouput was not as ripple as we would have thought it should have been.
Further investigation is leading us toward two of the six triac's are not switching on and off. they seem to be stuck on and passing the whole wave. one is bad on phase A and the other on Phase B.
RE: Excessive Heat Primary Delt-Wye, WHY?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Excessive Heat Primary Delt-Wye, WHY?
RE: Excessive Heat Primary Delt-Wye, WHY?
Or it sould be a PQ problem form the VFD.