1. Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
[1] A 1φ, 50 Hz, 500 V transformer has 400 primary and 1000 secondary
turns. If the net cross sectional area of the core is 60 cm2
determine (a)
peak value of flux and flux density (b) emf induced in the secondary (c)
number of secondary turns to induce an emf of 2500 V
Ans: (a) 5.63 mWb, 0.938 Wb / m2 (b) 1250 V (c) 2000 turns

2. Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
[2] A 2200/220V, 50Hz single phase transformer has exciting current of
0.6A and a core loss of 361W with respect to HV side. If the transformer
supplies a load current of 60A at 0.8 p.f. lag at 220V, then calculate the
primary current and its p.f.
Ans: 6.487A, 0.766lag

3. Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
[3] An approximate equivalent circuit as referred to the low tension side of a
2500 / 250 V, 50 Hz, 1φ transformer has equivalent resistance & reactance
values of 0.2 Ω & 0.7 Ω respectively. The shunt branch resistance &
reactance values are 500 Ω & 250 Ω respectively. The load impedance is
3.8 + j 2.3 Ω. For maintaining the secondary voltage of 250 V, determine (a)
primary voltage to be applied (b) primary current (c) primary side power
factor (d) core loss (e) power output
Ans: (a) 2814.14∠5.68o
(b) 5.74∠-31.74o
(c) 0.85 lag (d) 158.4 W (e) 12 kW

4. Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
[4] The equivalent circuit shown of a 4 kVA, 50 Hz, 200 / 400 V, 1φ
transformer is with respect to the LV side. For a HV side current of 10 A at
0.8 pf lag at rated voltage, determine (a) LV side supply current (b)
efficiency (c) voltage to be applied on LV side
600 Ω 300 Ω
0.15 Ω 0.37 Ω
Ans: (a) 20.7 A (b) 96.05 % (c) 206.9 V

5. Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
[5] A 230 / 460 V, 50 Hz, 1φ transformer has a primary side impedance of (0.2
+ j 0.5) Ω and secondary side impedance of (0.75 + j 1.8) Ω. Determine the
secondary side terminal voltage and voltage regulation when supplying (a)
10 A at 0.8 pf lag (b) 10 A at 0.8 pf lead if the primary voltage is held
constant at 230V.
Ans: (a) 425.320 V, 7.54 % (b) 472 V, -2.608 %

6. Exercise
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
[5] A 230 / 460 V, 50 Hz, 1φ transformer has a primary side impedance of (0.2
+ j 0.5) Ω and secondary side impedance of (0.75 + j 1.8) Ω. Determine the
secondary side terminal voltage and voltage regulation when supplying (a)
10 A at 0.8 pf lag (b) 10 A at 0.8 pf lead if the primary voltage is held
constant at 230V.
Ans: (a) 425.320 V, 7.54 % (b) 472 V, -2.608 %