Tranformer output

[Toros]

Suppose I need 190 A @ 240v, 1phase from 12o/208v, 3ph service. I use 45 kva xfrmer with primary opcd , @ 100A-3p What if i use 45 kva xfrmer with opcd , @ 60A quest.: Would I get the same output as if I used 100A-3p opcd at primary side . I am minimizing current input to the tranformer ??? I will tell you the rest, the confusion behind it after you replied .... Thank you

 

[Sahib]

If you neglect losses, the transformer output power is equal to input power. Assuming no losses and transformer supplies resistive load, the transfomer output power is 190*240=45.6 kW. So even with no internal loss, 45 kva transformer will be overloaded. Again assuming a special 3 phase to single phase transformer, the current on the primary side in each phase would be 45600/1.732*208=126A. So 60A OCPD would not be sufficient.

 

[Toros]

If you neglect losses, the transformer output power is equal to input power. Assuming no losses and transformer supplies resistive load, the transfomer output power is 190*240=45.6 kW. So even with no internal loss, 45 kva transformer will be overloaded. Again assuming a special 3 phase to single phase transformer, the current on the primary side in each phase would be 45600/1.732*208=126A. So 60A OCPD would not be sufficient.

So, input power is equal to output power , if my primary is existing 60A C.B @ 208V, 3ph. , or, the input is : 60A x 208*1.73=21,600 VA I will get 21,600/240=90A I won't get 45 KvA/240V=190A 60A prim. limits us to 21,600VA or 90A I will need 22 KVA

 

[Smart $]

You do know you can power 240V 1? loads from any phase of a 240/120V 3? 4W secondary???

 

[Jraef]

Suppose I need 190 A @ 240v, 1phase from 12o/208v, 3ph service. I use 45 kva xfrmer with primary opcd , @ 100A-3p What if i use 45 kva xfrmer with opcd , @ 60A quest.: Would I get the same output as if I used 100A-3p opcd at primary side . I am minimizing current input to the tranformer ??? I will tell you the rest, the confusion behind it after you replied .... Thank you

You do not appear to understand how electrical equipment works. You cannot "minimize" the current input to a transformer by using a smaller breaker, unless by minimize you mean to turn it off by tripping a breaker.