Current densities in dry type VPI transformers 1

[edison123]

I want to spec a 500 KVA, 6.6 KV/415 V, 50 Hz indoor dry type VPI (not cast resin) transformer. For a temperature rise of 60 deg C over an ambient of 40 deg C, what arr the current densities I should specify for the HV & LV windings ? Conductors for both windings will be enameled, fibre glass covered rectangular conductors. No foil windings.

Muthu

http://www.edison.co.in

 

[alehman]

Sounds like a special order? I would not specify current density on a small transformer such as this. Just maximum temperature rise.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[edison123]

Thanks Alan. I want to spec the current densities to bring the bidders on the same platform.

Muthu

http://www.edison.co.in

 

[prc]

Muthu,As per today's capitalisation rates, the following specific loadings are followed by manufacturers.
Conventional dry type- B=1.60-1.65T Current Density-HV 2.5 A/mm2 LV =2A/mm2. In case of cast resin it is limited to 1.6 -1.7 A/mm2. Your idea of asking for maximum benchmark specific loadings so that you can compare competitive bids esp with regard to actual net active part( Cu &CRGO) weights is a clever idea which I had been propogating to customers,but in vain.

 

[edison123]

Thanks prc. Since I am buying the trafo for own use, I am willing to pay the bucks for quality. My proposed specs are 1.5 T max, 2 A/mm2 for both HV & LV.

Since you're into manufacturing, what would be your rough estimate for a dry type, VPI treated trafo of 500 KVA, 6.6 KV/415 V, 50 Hz with the above specs ?

Muthu

http://www.edison.co.in

 

[prc]

Why do you go for 1.5 T.You will unnecessarily incur cost with out value.Ask for prime CRGO from reputed origin( with stage inspection clause) and go for 1.6 /1.65 T .Specify that you will physically check the specific loadings during manufacturing stage.Rough estimate 0.7 MINR

 

[edison123]

This trafo will be fed by VFD and hence such low B and current density. Could you possibly send a quote to me ? I am looking for 500 KVA, dual voltage wye connected secondary 6.6-3.3 KV and 415 V delta primary, indoor, dry type VPI windings.

Muthu

http://www.edison.co.in

 

[jghrist]

Why not evaluate losses if you want to get all bidders on the same basis? Why do you care if one manufacturer has higher current density if the transformer meets temperature rise specs, except for higher losses which can be evaluated economically?