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This set of Electrical and Electronics Engineering Multiple Choice Questions & Answers (MCQs) focuses on Electrical And Electronics Engineering Set 10
Q1 | A 3-phase ,400 V, 4-pole induction motor is fed from a 3-phase, 400V, 50 Hz supply and runs at 1440 rpm. The frequency of rotor emf is
- 2hz
- 50hz
- 4hz
- 0hz
Q2 | In a 3-phase induction motor, the mechanical power developed, in terms of air rotor input P2 is
- (s - 1) p2
- p2 / (1-s)
- 1/(s p2)
- (1 - s) p2
Q3 | An induction motor employs a starting device to restrict………….. at start
- line voltage
- line current
- torque
- power
Q4 | High starting torque can be produced by induction motor if
- a squirrel cage motor is started with auto-transformer starter
- a slip-ring induction motor is started with star-delta starter
- a squirrel cage motor is started by direct-on-line starter.
- a slip-ring induction motor is started with rotor resistance starter
Q5 | A squirrel cage induction motor is favoured when ……………….. is the main consideration.
- initial cost
- rotor core and rotor teeth
- stator core and stator teeth
- stator winding
Q6 | The torque developed by a 3-phase induction motor during starting
- depends on rotor induced emf during starting
- rotor induced emf during running condition
- does not depend on rotor induced emf
- none of these
Q7 | Condition for maximum torque developed during starting by a three phase induction motor is
- r2 = x2
- r2 =s x2
- r2 /s x2
- x2/r2
Q8 | Condition for maximum torque developed during running by a three phase induction motor is
- r2 = x2
- r2 =s x2
- r2 /s x2
- x2/r2
Q9 | Starting torque depends on
- rotor resistance and rotor reactance during starting
- supply voltage
- both 1 and 2
- none of these
Q10 | Torque developed by three phase induction motor
- depends on power factor of rotor
- depends on power factor of stator
- does not depend on on power factor of rotor or stator
- both 1 and 2
Q11 | The power factor of induction motor is during running condition
- depend on slip
- is independent of slip
- rotor reactance
- both b and c
Q12 | The torque developed by three phase induction motor depends on following three factors
- speed, frequency, number of poles
- voltage, current and stator impedance
- synchronous speed, rotor speed and frequency
- rotor emf, rotor current and rotor p.f
Q13 | When load is placed in three phase induction motor, its speed
- decreases
- increases
- remains unchanged
- becomes zero
Q14 | When load is connected to three phase induction motor is increased, then its slip
- decreases
- increases
- remains unchanged
- becomes zero
Q15 | When load is connected to three phase induction motor is increased, then its rotor induced emf
- decreases
- increases
- remains unchanged
- becomes zero
Q16 | When load is placed in three phase induction motor its current
- decreases
- increases
- remains unchanged
- becomes zero
Q17 | When load is placed in three phase induction motor, its torque
- decreases
- increases
- remains unchanged
- becomes zero
Q18 | Maximum torque during running condition developed by three phase induction motor can be obtained by changing rotor resistance
- in squirrel cage type motor
- in slip ring type motor
- in both 1 and 2
- none of these
Q19 | There is no electrical connection between stator and rotor, still power is transffered from stator to rotor through
- magnetic flux
- air
- water
- conductor
Q20 | At start , the slip of induction motor is
- zero
- 0.5
- one
- infinite
Q21 | Under running condition, the rotor reactance is proportional to
- induced emf
- rotor current
- slip
- supply voltage
Q22 | Under running condition , the rotor resistance is proportional to
- induced emf
- rotor current
- slip
- none of these
Q23 | At start the rotor power factor is
- very high
- very low
- unity
- zero
Q24 | Power factor of rotor of three phase induction motor depends on
- rotor resistance
- speed of rotor
- rotor reactance
- all of these
Q25 | The function of starter is
- to start the motor
- to start and stop the motor
- to limit the starting current
- to limit the applied the voltage