Induction Motor Slip Energy Recovery MCQ [Free PDF] – Objective Question Answer for Induction Motor Slip Energy Recovery Quiz

21. Calculate the line voltage in the delta connection when phase voltage=45 V.

A. 46 V
B. 47 V
C. 45 V
D. 78 V

Answer: C

The line voltage in the case of delta connection is phase voltage. Line current leads the phase current by an angle of 30°.

VL-L=Vph = 45 V. 

 

22. The slope of the V-I curve is 35.48°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

A. 0.452 Ω
B. 0.462 Ω
C. 0.752 Ω
D. 0.712 Ω

Answer: D

The slope of the V-I curve is resistance.

The slope given is 35.48° so R=tan(35.48°)=.712 Ω.

The slope of the I-V curve is reciprocal to resistance. 

 

23. If induction motor rotor power is 157.5 KW and gross developed power is 79.9 KW, then rotor ohmic loss will be _________ KW.

A. 77.5
B. 77.6
C. 76.9
D. 77.1

Answer: B

Rotor ohmic losses are due to the resistance of armature windings. Net input power to the rotor is equal to the sum of rotor ohmic losses and mechanically developed power.

Rotor ohmic losses=Air gap power-Mechanical developed power

=157.5-79.9=77.6 KW. 

 

24. Calculate the line current in the delta connection when phase current=17 A.

A. 29.44 A
B. 24.64 A
C. 23.48 A
D. 26.56 A

Answer: A

The line voltage in the case of delta connection is phase voltage. Line current leads the phase current by an angle of 30°.

IL-L = 1.73×Iph = 29.44 A. 

 

25. Calculate the active power in a 168.12 H inductor.

A. 65 W
B. 0 W
C. 68 W
D. 64 W

Answer: B

The inductor is a linear element. It only absorbs reactive power and stores it in the form of oscillating energy. The voltage and current are 90° in phase in the case of the inductor so the angle between V & I is 90°.

P = VIcos90° = 0 W. 

 

26. Calculate the maximum value of slip when rotor resistance is 2 Ω and rotor reactance is 3 Ω.

A. 0.66
B. 0.33
C. 0.44
D. 0.99

Answer: A

The maximum torque occurs when the slip value is equal to R2÷X2. Maximum torque is also known as breakdown torque, stalling torque, and pull-out torque. The maximum value of slip is

R2÷X2=2/3=.66. 

 

27. Calculate the total heat dissipated in a rotor resistor of 21 Ω when.81 A current flows through it.

A. 13.77 W
B. 12.56
C. 16.78 W
D. 13.98 W

Answer: A

The rotor resistor is a linear element. It only absorbs real power and dissipates it in the form of heat. The voltage and current are in the same phase in the case of the resistor so the angle between V & I is 90°.

P=I2R=.81×.81×21=13.77 W. 

 

28. Calculate the active power in an 8.12 F capacitor.

A. 89 W
B. 41 W
C. 0 W
D. 48 W

Answer: C

The capacitor is a linear element. It only absorbs reactive power and stores it in the form of oscillating energy. The voltage and current are 90° in phase in the case of the capacitor so the angle between V & I is 90°.

P=VIcos90° = 0 W. 

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