A) load must be reduced B) friction at bearings must be reduced C) e.m.f. must be injected in the rotor in a phase opposite to the rotor e.m.f. D) e.m.f. must be injected in the rotor in phase with rotor e.m.f. Ans : (D)
A) a method of braking B) a method of synchronization C) a method of step by step loading D) energizing a motor once or repeatedly to obtain small movements for mechanisms. Ans : (D)
A) High frequency B) Low voltage C) Shorted stator coils D) Overload. Ans : (A)
A) the motor will start ‘crawling’ B) the maximum torque will remain unchanged C) slip will increase D) airgap flux will be reduced to half. Ans : (B)
A) Pole changing B) Change of frequency C) Cascade control D) Any of the above. Ans : (D)
A) Blown fuses B) Uneven airgap C) One or two phase open D) Overload. Ans : (B)
A) Stator inductance B) Supply current C) Rotor resistance D) Frequency. Ans : (D)
A) 20 HP, 750 rpm B) 20 HP, 1500 rpm C) 5 HP, 750 rpm D) 5 HP, 1500 rpm. Ans : (C)
A) 25 A B) 6 A to 10 A C) 11 A to 14 A D) 15 A to 18 A. Ans : (B)
A) 1 kV B) 10 kV C) 1 kV + 2 x rated voltage D) 10 kV + 2 x rated voltage. Ans : (C)