Exercise

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

[1] A 3, 50 Hz, 6 pole induction motor has a no load slip of 1 % and a full load slip of 3 %. Determine (a) synchronous speed (b) no load speed (c) full load speed (d) frequency of rotor current at standstill (d) frequency of rotor current at full load

Exercise

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

[2] A 3, 50 Hz, 4 pole induction motor has a star connected rotor. The per phase rotor resistance is 0.1 and per phase standstill reactance is 2 . If the induced emf between the slip rings is 100 V, full load speed is 1460 rpm, determine (a) slip (b) rotor induced emf (c) per phase rotor reactance (d) rotor current. Assume the slip rings are short circuited.

Exercise

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

[3] A 3, induction motor has a star connected rotor. The rotor emf between the slip rings at standstill is 50 V. The rotor resistance and standstill rotor reactance are 0.5 and 3 respectively. Determine (a) per phase rotor current at starting if a star connected rheostat of 6 per phase is connected across the slip rings (b) full load rotor current and rotor power factor for a full load slip of 4 % (c) per phase rotor emf under full load condition

Exercise

ELE 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal 3

[4] A A 3, 50 Hz, 4 pole star connected induction motor on full load develops a useful torque of 300 Nm. If the rotor emf is 120 cycles per minute and torque lost in friction is 50 Nm, determine (a) slip (b) operating speed (c) net power output (d) gross torque (e) power lost due to friction & windage (f) gross power output (g) total power input if total losses are 10 kW (h) efficiency

Exercise

ELE 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal 3

[5] A 3, 50 Hz, 36 kW, 4 pole induction motor has a full load efficiency of 84 %. The friction & windage losses are one-third of no load losses and rotor copper losses equal the iron loss at full load. Determine (a) Total Losses (b) Stator Core Loss (c) Rotor Copper Loss (d) Friction & Windage Loss (e) Gross Power Output (f) Rotor Input