Alternator Excitation Voltage

Why would you want to calculate it? The voltage regulator should adjust the excitation voltage automatically to maintain the 11 kV output voltage.

But as power is proportional to magnetic field produced by the field coils, magnetisation is proportional to field current, and field current is proportional to field voltage (Ohm's law), I would expect field voltage to vary linearly with output power.

So in your case that's 100 volt.

Cheers..........Codey

Dear,

Assume pf = 0.8

Amps at 7.5 MW = 492 A, excitation is 150v, 4.4 A

Amp at 5 MW = 5000/1.732*11*0.8 = 328 Amp. with excitation of

Excitation voltage controls the reactive power. If your volts & PF are same,

KVA at 7.5 MW = 1.732 * 11kv * 492 = 9.373 KVA

KVA at 5 MW = 1.732 * 11* 328 = 6249 KVA.

excitation required at 5 MW = 6249*150/9373 = 100 V. @ 2.93 Amp.