Electrical Machines Mock Test 9

10%

Question 1 of 10

1. If a 3-phase induction motor is fed from the rotor short circuiting the stator terminals, frequency of the current flowing in the short-circuited stator is?

slip frequency

zero

frequency corresponding to the rotor speed

supply frequency

Question 1 of 10

Question 2 of 10

2. The leakage flux is the flux in side the transformer which?

windows of the core

links either of the windings

links both of the windings

yoke of the core

Question 2 of 10

Question 3 of 10

3. Which of the following statements are incorrect for an ideal transformer?

I. Voltages - inverse ratio
II. Current - direct ratio
III. Impedance - direct ratio squared
Iv. Power - remains same

III,IV

I,II,III,IV

I,II

I,IV

Question 3 of 10

Question 4 of 10

4. Which of the following statements support the ideal transformer features?

I. Zero winding resistance
II. Zero leakage flux
III. Constant core losses

I, II

I, III

III

I, II, III

Question 4 of 10

Question 5 of 10

5. I. Voltage of an externally excited induction generator can not be controlled.
II. Frequency of an externally excited induction generator can be controlled.

I is true, II is false

I is true, II is true

I is false, II is true

I is false, II is false

Question 5 of 10

Question 6 of 10

6. Reducing the poles of a 3-phase induction motor, it _________

will make no change in power factor

can not be depicted

will increase maximum power factor

will decrease maximum power factor

Question 6 of 10

Question 7 of 10

7. A 6-pole lap wound DC generator has a developed power of P watts and brush voltage of E volts. Three adjacent brushes of the machine had been found worn out and got open circuited. If the machine is operated with the remaining brushes, voltage and power that could be obtained from the machine are _________

E, P

E, P/3

E/P, 2P/3

E, 2P/3

Question 7 of 10

Question 8 of 10

8. Energising the transformer primary from a triangular wave flux makes the output voltage as __________

a sine wave

a triangular wave

square wave shifted by 90°

a square wave

Question 8 of 10

Question 9 of 10

9. A 3-phase induction motor has full load efficiency of 0.7 and a maximum efficiency of 0.85. It is operated at a slip of 0.6 by reduced voltage method. The efficiency of the motor at this operating point is?

none of the mentioned

in the range of 0.8 to 0.2

less than 0.35

greater than 0.35

Question 9 of 10

Question 10 of 10

10. Which is the most acceptable application field where an induction generator can be used?

hydro power system

wind power system

nuclear power station

steam power system

Question 10 of 10