T8 1 ph-tr

Exercise

ELE 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal

[1] A 1, 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

Exercise


[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

Exercise


[3] An approximate equivalent circuit as referred to the low tension side of a 2500 / 250 V, 50 Hz, 1 transformer has equivalent resistance & reactance values of 0.2 & 0.7 respectively. The shunt branch resistance & reactance values are 500 & 250 respectively. The load impedance is 3.8 + j 2.3 . 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) 2814.145.68o (b) 5.74-31.74o (c) 0.85 lag (d) 158.4 W (e) 12 kW

Exercise


[4] The equivalent circuit shown of a 4 kVA, 50 Hz, 200 / 400 V, 1 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

600 300

0.15 0.37

Ans: (a) 20.7 A (b) 96.05 % (c) 206.9 V

Exercise


[5] A 230 / 460 V, 50 Hz, 1 transformer has a primary side impedance of (0.2 + j 0.5) and secondary side impedance of (0.75 + j 1.8) . 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 %

T8 1 ph-tr

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