A 2200 / 250 V transformer takes 0.5 A at a p.f. of 0.3 on open-circui...
Given data:
Transformer rating (S) = 2200 VA
Primary voltage (V1) = 250 V
Primary current at no-load with a power factor of 0.3 (I0) = 0.5 A
To find: Magnetizing component of no-load current
Calculations:
Apparent power (S) = V1 × I0
= 250 × 0.5
= 125 VA
The real power (P) consumed by the transformer is zero as it is on open-circuit. Hence, the reactive power (Q) consumed by the transformer is equal to the apparent power (S).
Q = S = 125 VAR
The power factor (cosφ) of the transformer is given as 0.3. Therefore, the reactive power (Q) and the active power (P) can be related using the power factor as:
cosφ = P/S
0.3 = P/125
P = 37.5 W
The magnetizing component of the no-load current, Im can be calculated as:
Im = √(I0² - Ic²)
where Ic = I0 × cosφ
Ic = 0.5 × 0.3
= 0.15 A
Im = √(0.5² - 0.15²)
= 0.477 A
Therefore, the magnetizing component of no-load primary current is 0.477 A, which is closest to option (B).