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This set of Electrical Drives and Controls EDC Multiple Choice Questions & Answers (MCQs) focuses on Electrical Drives And Controls Set 14
Q1 | 1 SPEED CONTROL OF THREE PHASE INDUCTION MOTOR
- slip frequency
- supply frequency
- the frequency corresponding to rotor speed
- zero
Q2 | An 8-pole, 3-phase, 50 Hz induction motor is operating at a speed of 720 rpm. The frequency of the rotor current of the motor in Hz is
- 2
- 4
- 3
- 1
Q3 | Calculate the phase angle of the sinusoidal waveform z(t)=78sin(456πt+2π÷78).
- π÷39
- 2π÷5
- π÷74
- 2π÷4
Q4 | Calculate the moment of inertia of the disc having a mass of 54 kg and diameter of 91 cm.
- 5.512 kgm2
- 5.589 kgm2
- 5.487 kgm2
- 5.018 kgm2
Q5 | Calculate the moment of inertia of the thin spherical shell having a mass of 73 kg and diameter of 36 cm.
- 1.56 kgm2
- 1.47 kgm2
- 1.38 kgm2
- 1.48 kgm2
Q6 | A 50 Hz, 4poles, a single phase induction motor is rotating in the clockwise direction at a speed of 1425 rpm. The slip of motor in the direction of rotation & opposite direction of the motor will be respectively.
- 0.05, 0.95
- 0.04, 1.96
- 0.05, 1.95
- 0.05, 0.02
Q7 | The frame of an induction motor is made of
- aluminum
- silicon steel
- cast iron
- stainless steel
Q8 | The slope of the V-I curve is 5°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.
- .3254 Ω
- .3608 Ω
- .3543 Ω
- .3443 Ω
Q9 | In an induction motor, when the number of stator slots is equal to an integral number of rotor slots
- there may be a discontinuity in torque slip characteristics
- a high starting torque will be available
- the maximum torque will be high
- the machine may fail to start
Q10 | Calculate the active power in a 487 H inductor.
- 2482 w
- 1545 w
- 4565 w
- 0 w
Q11 | Calculate the active power in a 788 ω resistor with 178 A current flowing through it.
- 24.96 mw
- 24.44 mw
- 24.12 mw
- 26.18 mw
Q12 | In the rotor voltage injection method, when an external voltage source is in phase with the main voltage then speed will
- increase
- decrease
- remain unchanged
- first increases then decrease
Q13 | A 2-pole, 3-phase, Hz induction motor is operating at a speed of 550 rpm. The frequency of the rotor current of the motor in Hz is 2.
- 9.98
- 9.71
- 9.12
- 9.37
Q14 | Calculate the average value of the sinusoidal waveform x(t)=848sin(1.65πt+2π÷0.68).
- 0
- 78 v
- 15 v
- 85 v
Q15 | R.M.S value of the periodic square waveform of amplitude 72 V.
- 72 v
- 56 v
- 12 v
- 33 v
Q16 | In the rotor voltage injection method, when an external voltage source is in opposite phase with the main voltage then speed will
- increase
- decrease
- remain unchanged
- first increases then decrease
Q17 | The rotor injection method is a part of the slip changing technique.
- true
- false
Q18 | The slip recovery scheme is a part of the synchronous speed changing technique.
- true
- false
Q19 | If induction motor air gap power is 1.8 KW and gross developed power is .1 KW, then rotor ohmic loss will be KW.
- 1.7
- 2.7
- 3.7
- 4.7
Q20 | Calculate the time period of the waveform v(t)=12sin(8πt+8π÷15)+144sin(2πt+π÷6)+ 445sin(πt+7π÷6).
- 8 sec
- 4 sec
- 7 sec
- 3 sec
Q21 | Calculate the total heat dissipated in a resistor of 44 Ω when 0 A current flows through it.
- 0 w
- 2 w
- 1.5 w
- .3 w
Q22 | The value of slip at which maximum torque occurs
- r2÷x2
- 4r2÷x2
- 2r2÷x2
- r2÷3x2
Q23 | AC voltage controllers convert
- fixed ac to fixed dc
- variable ac to variable dc
- fixed ac to variable ac
- variable ac to fixed ac
Q24 | In AC voltage controllers the
- variable ac with fixed frequency is obtained
- variable ac with variable frequency is obtained
- variable dc with fixed frequency is obtained
- variable dc with variable frequency is obtained
Q25 | In the principle of phase control
- the load is on for some cycles and off for some cycles
- control is achieved by adjusting the firing angle of the devices
- control is achieved by adjusting the number of on off cycles
- control cannot be achieved