KVA rating for 3 phase transformer.

[Greg Wrenn]

I am hooking up machines in a factory that was bought from another company. We have 480 volt wye system and I am needing to buy step-down transformers to reduce down to 240 volts. If I bring up a KVA to Amp calculator to calculate what I need for a 50 amp machine I get that the KVA is approx 41.6 KVA. The person that I am buying the transformer from says that a 30 KVA transformer will be able to handle up to a 60 amp machine. If I calculate out 30 KVA I only get 36.084 amps. What am I missing? Does this calculator not include something about a transformer?

 

[infinity]

Can show your calculation?

30000/240/1.73= 72.25 amps

 

[jim dungar]

I am hooking up machines in a factory that was bought from another company. We have 480 volt wye system and I am needing to buy step-down transformers to reduce down to 240 volts. If I bring up a KVA to Amp calculator to calculate what I need for a 50 amp machine I get that the KVA is approx 41.6 KVA. The person that I am buying the transformer from says that a 30 KVA transformer will be able to handle up to a 60 amp machine. If I calculate out 30 KVA I only get 36.084 amps. What am I missing? Does this calculator not include something about a transformer?

Are you using a calculator for single phase?

 

[curt swartz]

OP is calculating 50 amps on the primary (480) volt side and not the secondary side.

 

[Greg Wrenn]

Are you using a calculator for single phase?

No I do have three phase selected.

 

[infinity]

OP is calculating 50 amps on the primary (480) volt side and not the secondary side.

Yes, he should be asking if a 30 Kva is large enough for a 50 amp, 240 volt machine.