Assignment – 1
1. A 200 kVA, 1-phase transformer with voltage ratio of 6350/660 V has the following
winding resistances and reactances:
R1 = 1.56 Ω,
R2 = 0.016 Ω,
X1 = 4.67 Ω,
X2 = 0.048 Ω
Calculate the resistances and reactances referred to High Voltage side.
2. Find the active and reactive components of no-load current, and the no-load current of a
440/220 V single phase transformer if the power input to the HV winding is 80 W. The
low-voltage winding is kept open. The power factor of the no-load current is 0.3 lagging.
3. A 230/110 V single phase transformer takes an input of 350 VA at no load and at rated
voltage. The core loss is 110 W. Find the following:
(i) The iron-loss component of no-load current
(ii) The magnetizing component of no-load current
(iii) No-load power factor.
4. A 125 kVA transformer having primary voltage of 2000 V at 50 Hz has 182 primary and
40 secondary turns. Neglecting losses, calculate:
(a) Full load primary and secondary currents
(b) The no-load secondary induced EMF
(c) The maximum flux in the core.
5. A single phase, 250/500 V transformer gave the following results:
Open-circuit Test:
250 V, 1 A, 80 W on LV side
Short-circuit Test:
20 V, 12 A, 100 W on HV side
Calculate the circuit constants and show them on an equivalent circuit.