Suppose a Transformer has some rating on its nameplate such as:
THE RESULT IS SHOWN BELOW:
KVA= 100KVA,
R = 500ohm
L= 1.5henry
Frequency = 50Hz
XL = 2πfL = 2 x 3.1415 x 50 x 1.5 = 471.2ohm
Impedance Z = √ (R2+XL2) = √ (5002+ 471.22) = 687 Ω
Power factor, Cos θ = R/Z, = (500/687), = 0.73 lagging,
Transformer output in active power, KW = KVA*cosθ
= 73KW
now again, taking the frequency as
f= 60Hz,
XL = 2πfL = 2 x 3.1415 x 60 x 1.5 = 565.5Ω.
Impedance Z = √ (R2+XL2) = √ (5002+ 565.52) = 754.8 Ω
Power factor, Cos θ = R/Z, = (500/754.8), = 0.66 lagging,
Transformer output in active power, KW = KVA*cosθ
= 66KW
Difference in kW= 73-66 = 7KW=
So the lower the frequency the higher the output..
Reason is the inductive reactance.
