How does frequency affect KVA rating of a transformer?
If a 500 kva, 400 v, 60 hz t/f is to be operated on 50 hz
frequency then how will its KVA rating change?
a-increase
b-decrease
c-remains same
Also explain why do u think like that.
Answer Posted / k r vishnu narayanan
E/f = 4.44*N*phi(max)
E: induced emf
f: frequency
N: number of turns
phi: max flux in the core
When frequency is reduced keeping E constant(at E(max)), flux(phi(max)) has to increase (from eq:)to saturation and harmonics will come into effect. So, there has to be a maximum allowable voltage at a particular frequency and the current too is limited by the saturation effects implying that both V and I has to be limited at a particular frequency (maximum current is always limited by number of turns). Thus their product(kVA) has to be directly proportional to frequency and the answer to this question is b(decrease).
God bless...
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