Question: Stepless speed control of induction motor is possible by which of the following methods ?

• 1. e.m.f. injection in rotor eueuit
• 2. Changing the number of poles
• 3. Cascade operation
• 4. None of the above

Question: It is advisable to avoid line-starting of induction motor and use starter because__________?

• 1. motor takes five to seven times its full load current
• 2. it will pick-up very high speed and may go out of step
• 3. it will run in reverse direction
• 4. starting torque is very high

Question: When the equivalent circuit diagram of doouble squirrel-cage induction motor is constructed the two cages can be considered__________?

• 1. in series
• 2. in parallel
• 3. in series-parallel
• 4. in parallel with stator

Question: The torque developed in the cage induction motor with autostarter is___________?

• 1. k/torque with direct switching
• 2. K x torque with direct switching
• 3. K2 x torque with direct switching
• 4. k2/torque with direct switching

Question: The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type__________?

• 1. star connected only
• 2. delta connected only
• 3. A and B both
• 4. none of the above

Question: The crawling in the induction motor is caused by____________?

• 1. low voltage supply
• 2. high loads
• 3. harmonics develped in the motor
• 4. improper design of the machine

Question: Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor _____________?

• 1. By changing the number of stator poles
• 2. Rotor rheostat control
• 3. By operating two motors in cascade
• 4. By injecting e.m.f. in the rotor circuit

Question: An induction motor is identical to_________?

• 1. DC compound motor
• 2. DC series motor
• 3. synchronous motor
• 4. asynchronous motor

Question: The injected e.m.f. in the rotor of induction motor must have__________?

• 1. zero frequency
• 2. the same frequency as the slip frequency
• 3. the same phase as the rotor e.m.f.
• 4. high value for the satisfactory speed control

Question: In case of the induction motors the torque is___________?

• 1. inversely proportional to (Vslip)
• 2. directly proportional to (slip)2
• 3. inversely proportional to slip
• 4. directly proportional to slip