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AssuredElectrical, Master Electrician
Category: Electrical
Satisfied Customers: 4241
Experience:  Contractor-42+ Years in the ElectricalTrade
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I have a 480V 3Ph resistive load rated at 58A. I have a 208V

Customer Question

I have a 480V 3Ph resistive load rated at 58A. I have a 208V 3Ph supply existing. Can I boost this with a transformer? What KVA would be required? What would my 208V 3Ph amp draw be? Thanks
Submitted: 2 years ago.
Category: Electrical
Expert:  AssuredElectrical replied 2 years ago.
Welcome. My name is ***** ***** would be glad to assist.Needing 58 amps on the transformer low voltage side, you would require a 22.5 KVA transformer which would require 27 amps on the primary 480 volt side.If the load being resistive is for a heating application, you would need to base the load on 125% of the rating since heating is considered as a continuous supply.So, if the rating is 58 amps on heating, you need a 30 KVA transformer which is the closest to the 125% as you can get at 83 amps. This would require 36 amps on the 480 volt primary side. (next closest is only 65 amps on a 25 KVA) Let me know if anything further is needed, oir any clarification.Thanks
Customer: replied 2 years ago.
I have existing 208V 3Ph Wye now. My heating load I want to install is 480V 3Ph rated for 58A at 480V 3Ph. I am trying to size a boost type transformer and size it accordingly and need 58A (resistive) at 480V 3Ph. I may be wrong, but since this is a boost type application, I thought my KVA would be higher.... Also what would the amp draw be on my existing 208V 3Ph service to accomplish this boost to 480V 3Ph with a 58A resistive load... Thank you
Expert:  AssuredElectrical replied 2 years ago.
Ok, My apologies for some reason in thinking it was the other direction. Sorry for that.Since your load is on the 480 volts at 58 amps, and the load is heating, you are required as previously posted to supply with 125% of the rated load.So, your 58 amps becomes 72.5 amps.At 72.5 amps on the secondary side at 480 volts, you will need a 75 KV.A transformer.The 208 primary input will be 208 amps Thanks for the reply and correction.