Generator Alternator Reactance

[binwork91]

Because you tell it when you enter the Bus base kV!

So reactance number has nothing to do with short circuit calculation.
Case 1: 250KVA 208V generator, 250KVA alternator, 480V base, X0=A, X'=B, X"=C.
Case 2: 250KVA 208V generator, 250KVA alternator, 208V base, X0=D, X'=E, X"=F.

So when I input these two case, I will get same result, because my bus base KV is 208.
It does not make sense to me, because these two case has different X0, X', X"

 

[xptpcrewx]

So reactance number has nothing to do with short circuit calculation.
Case 1: 250KVA 208V generator, 250KVA alternator, 480V base, X0=A, X'=B, X"=C.
Case 2: 250KVA 208V generator, 250KVA alternator, 208V base, X0=D, X'=E, X"=F.

So when I input these two case, I will get same result, because my bus base KV is 208.
It does not make sense to me, because these two case has different X0, X', X"

I don’t know what you are getting at. If you have an example please provide the details.

In general, if the bus Base kV is different than the Generator Rated kV, then different voltages are at play and a conversion is automatically made using the formulae in post 1. If the voltages are the same, no conversion is necessary.

 

[binwork91]

I don’t know what you are getting at. If you have an example please provide the details.

In general, if the bus Base kV is different than the Generator Rated kV, then different voltages are at play and a conversion is automatically made using the formulae in post 1. If the voltages are the same, no conversion is necessary.

Case 1: 250KVA 208V generator, 250KVA alternator, 480V base, X0=0.08, X'=0.19, X"=0.17.
Case 2: 250KVA 208V generator, 250KVA alternator, 208V base, X0=0.426, X'=1.0118, X"=0.9053.

Case 1 is the 480V alternator show in the OP, Case 2 is our calculation for 208V.
Let's assume the software allow us to input number large than 1.

I think case 1 and case 2 will have different result. because these two case has different X0, X', X".

In general, if the bus Base kV is different than the Generator Rated kV, then different voltages are at play and a conversion is automatically made using the formulae in post 1. If the voltages are the same, no conversion is necessary.

For OP, my generator is 208V, so generator rate KV is 208V, and I will connect to bus base kV 208V. And when I need to input the Impedance, there is not input for the alternator KV. So my confusion is the software does not know the impedance is from 208V alternator data sheet or 480V alternator data sheet, how can it know if it need to convert it or not?