Single Phase Induction Motor MCQs Part 1

Single Phase Induction Motor MCQs Part 1

The rotor used in single phase induction motor is

The rotor used in single phase induction motor is:

1. Squirrel cage
2. Wound rotor
3. Any of above
4. None of these

Correct answer: 1. Squirrel cage

The resistance split-phase induction motors are most popular type of single-phase inductions motors because of their

The resistance split-phase induction motors are most popular type of single-phase inductions motors because of their:

1. Low cost
2. Long starting period
3. High starting torque
4. None of these

Correct answer: 1. Low cost

The full-load efficient of shaded pole motor is around

The full-load efficient of shaded pole motor is around:

1. 5 to 10%
2. 30 to 35%
3. 50 to 80%
4. 80 to 90%

Correct answer: 2. 30 to 35%

At starting, the winding of 220 V, 50 HZ, split phase induction motor have following parameters

At starting, the winding of 220 V, 50 HZ, split phase induction motor have following parameters:

Main winding: R = 5 Ω; XL = 8 Ω

Starting winding: R = 8 Ω; XL = 5 Ω

The line current is:

1. 26
2. 44.82
3. 54.82
4. 89.64

Correct answer: 2. 44.82

Solution:

Phase angle between V and Im (Φm) = tan^-1 8/5 = 57.99°

——————-

Phase angle between V and Is (Φs) = tan^-1 5/8 = 26°

——————-

Phase angle between Is and Im (α) = Φm – Φs = 57.99° – 32.01° = 26°

——————-

Line current (I) = √(Im² + Is² + 2Im*Is*cos α) = 44.82 A

A 4 pole, 250 W, 110 V, 60 Hz capacitor start induction motor takes a full-load line current of 4 A when running at 1760 RPM. The full-load efficiency of motor is 68%. The motor power factor is

A 4 pole, 250 W, 110 V, 60 Hz capacitor start induction motor takes a full-load line current of 4 A when running at 1760 RPM. The full-load efficiency of motor is 68%. The motor power factor is:

1. 0.84 lag
2. 0.87 lag
3. 0.9 lag
4. 0.94 lag

Correct answer: 1. 0.84 lag

Explanation:

Input power to motor (Pi) = 250/0.68 = 367.6

—————

Motor power factor = Pi/VI = 367.6/(110*4) = 0.84 lag