Alternator impedance
Alternator impedance
(OP)
I am struggling with a fault calculation for a generator installation.
I have a 1500kVA 400V 3ph generator with instantaneous If 16655A, short term If 12028A for 0.135s and sustained If 5,400A. But what do I imput for the external impedance; is it simply 230/5400=0.04?
I have a 1500kVA 400V 3ph generator with instantaneous If 16655A, short term If 12028A for 0.135s and sustained If 5,400A. But what do I imput for the external impedance; is it simply 230/5400=0.04?






RE: Alternator impedance
Mike
RE: Alternator impedance
Xd 2.96
X'd 0.18
X''d 0.13
All at 1550kVA base 400/230V.
RE: Alternator impedance
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RE: Alternator impedance
Mike
RE: Alternator impedance
z_base = Un^2/An = 0.106 ;
The xd , or sincronous reactance (steady state) , in per units
is equal to 2.96 .
xd [ohm] = 2.96*0.106 = 0.316
that is close to 0.4 .
It is correct ?
RE: Alternator impedance
The initial fault current can be determined from the sub-transient reactance, but after a few cycles, all of the other factors mentioned above come in to play.