Re: Three phase power

Ronald,

I am not trying to be condescending but,

Amps is Amps - three phase is no different than single phase

Line to Line volts is Line to Line volts - three phase is no different than single phase

Line to Neutral Volts is Line to Neutral Volts - three phase is no different than single phase (well almost, 1phase L->N = L->L/2 and 3phase L->N = L->L/1.73)

Power is not as easy (commonly called watts these normal formulas really are for VA).

Line to Neutral Power is Line to Neutral power - three phase is no different than single phase Watts = L->N Volts x Amps.

Line to Line Power is different -

3phase 3wire Watts = L->L Volts x Amps x 1.73

3phase 2wire Watts = L->L Volts x Amps

1phase 2wire Watts = L->L Volts x Amps

From the above you can see that the only time we use the 1.73 factor for three phase is when we determine power using all three phase conductors or when we convert from L->N volts to L->L volts.

So six seperate 6A 120V 2 wire loads can be fed: 1 circuit 2wire 120V 36A, 2 circuits 2wire 120V 18A each, or 3 circuits 2wire 120V 12A each. Notice it makes no difference if the system is 1phase 2wire (120V), 1phase 3wire (120/240), or 3phase 4wire (208Y/120V).

And, the power supply requirements for these 6 loads is: 4.32KVA at 120V(1 circuit-36A), 4.32KVA at 120/240V (2 circuits-18A), and 4.32KVA at 208Y/120 (3 circuits-12A)