Why the rotor conductors of the squirrel cage rotor are short-circuited and in the case of slip-ring induction motors, the rotor circuit is closed through resistors? Q2. A -3-phase, 8-pole induction motor is required to be operated at about 700 rpm. If supply frequency is 60 Hz, determine its actual speed if slip is 5%. *

Q2] Fill in the blank (9 Marks) 1-The current drwan by the armature of D.C. motor is directly proportional to 2- The speed of a D.C. shunt-wound motor will shunt field regulator is increased. 3- The synchronous speed of a three-phase induction motor is number of pairs of poles. Rotor copper losses Rotor input power in induction motor = 5- A 4-pole three-phase induction motor has a synchronous speed of 25 r.p.s. The frequency of the supply to the stator is_ Hz. 6- The power input to a mains transformer is 200VA. If the primary current is 2.5A, the secondary voltage is 2V and assuming no losses in the transformer, the turns ratio step down. is 7- A 200kVA transformer has an iron loss of 1 kW and full load cu loss of 2 kW. Its load kVA corresponding to maximum efficiency is kVA. 8- If cu loss of a transformer at 7/8th full load is 4900 W, then its full-load cu loss would be watt. 4- if the value of resistance of the proportional to the 9- The slight curvature at the lower end of the open…

P-1).. Which of the following determine the amount of torque produced by a single-phase split-phase motor? a) The strength of the magnetic field of the stator b) The strength of the magnetic field of the rotor c) The phase angle difference between the current in the start winding and the current in the run winding d) all of the above P-2). The phase angle difference between the currents in the start winding and run winding of a single-phase split-phase motor is typically 90 degrees. a) true b) false P-3). A centrifugal switch is used to disconnect the________ winding of a non-hermetically sealed single-phase split-phase motor at approximately 75% of rated speed. a) run b) start c) either "a" or "b" d) neither "a" nor "b" P-4). Where an internal centrifugal switch cannot be used, an external______ relay can be used to perform the same function in a single-phase split-phase motor. a) hot-wire b) current c) solid-state starting d) all of the above

7. A 4-pole, 500V shunt motor has 720 wave connected conductors on its armature. The full-los armature current is 60A and flux per pole is 0.03 Wb. The armature resistance is 0.020 and th contact drop per brush is 1V. then the full-load speed of the motor is -- a) 675 r.p.m. b) 690 r.p.m. c) 705 r.p.m. d) none of the previous,