Electric Drives Practice Test 2

1. The slope of the V-I curve is 45°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line.

4 Ω

3 Ω

2 Ω

1 Ω

2. 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 __________

3. Calculate the phase angle of the sinusoidal waveform z(t)=78sin(456πt+2π÷78).

2π÷4

π÷39

2π÷5

π÷74

4. The generated e.m.f from 16-pole armature having 57 turns driven at 78 rev/sec having flux per pole as 5 mWb, with lap winding is ___________

44.49 V

44.16 V

44.15 V

44.46 V

5. Calculate the value of the torque when 1 N force is applied perpendicular to a 1 m length of chain fixed at the center.

3 N-m

2 N-m

1 N-m

4 N-m

6. The leakage flux paths are ________ on the angular position of the rotor.

Proportional

Dependent and independent

Independent

Dependent

7. A 3-phase induction motor runs at almost 1000 rpm at no load and 950 rpm at full load when supplied with power from a 50 Hz, 3-phase supply. What is the corresponding speed of the rotor field with respect to the rotor?

40 revolution per minute

50 revolution per minute

60 revolution per minute

30 revolution per minute

8. Which of the following are used in preventing the hunting phenomenon in synchronous generators?

Damper bars

Short pitch chords

Distributed winding

Damper bars and short pitch chords

9. Calculate the active power in a 241 H inductor.

11 W

.51 W

21 W

0 W

10. The frame of a synchronous motor is made of _________

Silicon steel

Cast iron

Stainless steel

Aluminum