Total KVA current in a transformer

[Jpflex]

If a 300 KVA delta delta 3 phase transformer 4800 volts primary to 480 volts secondary and the math (KVA / secondary voltage x 1.732) yields about 361 amperes then is this the current between phase legs such as A to B, B to C, A to C?

If so it would seem Phase B TO C and A to C would also put out 361 amperes? And therefore total amperes exceeds 360? (Secondary only seeing 360 wouldn’t make sense if true)

I just want to make sure I told my boss correctly that output is 360 amperes total before he upsizes to a larger 600KVA transformer.

Thanks

 

[jim dungar]

There is no such thing as Total kVA in the way I think you are trying to calculate.

A 300kVA three-phase transformer is effectively (3) 100kVA single phase units interconnected.

In your case you would have the ability to pull 208A (100kVA @ 480V) between any two line conductors, A-B, B-C, and C-A. These single phase currents add vectorially to give you the three-phase line currents of 361A.

 

[Jpflex]

There is no such thing as Total kVA in the way I think you are trying to calculate.

A 300kVA three-phase transformer is effectively (3) 100kVA single phase units interconnected.

In your case you would have the ability to pull 208A (100kVA @ 480V) between any two line conductors, A-B, B-C, and C-A. These single phase currents add vectorially to give you the three-phase line currents of 361A.

Awesome thanks

 

[Jpflex]

There is no such thing as Total kVA in the way I think you are trying to calculate.

A 300kVA three-phase transformer is effectively (3) 100kVA single phase units interconnected.

In your case you would have the ability to pull 208A (100kVA @ 480V) between any two line conductors, A-B, B-C, and C-A. These single phase currents add vectorially to give you the three-phase line currents of 361A.

Wait so you can power 3 separate loads at 208 amperes betWeen AB BC AC phase Legs? This means we don’t need upsizing?

 

[ggunn]

Wait so you can power 3 separate loads at 208 amperes betWeen AB BC AC phase Legs? This means we don’t need upsizing?

This comes up a lot. Current in phases does not add; power does. If you have a balanced three phase circuit with 100A per phase the total line current is 100A, not 300A.

 

[don_resqcapt19]

Wait so you can power 3 separate loads at 208 amperes betWeen AB BC AC phase Legs? This means we don’t need upsizing?

Each of the single phase loads at 208 amps and 480 volts is ~100kVA, so you can supply 3 such loads from a 300kVA transformer.