Engineering Services (IES) Questions and Answers:Machines 1

Indian Engineering Services (IES) Questions and Answers:  

1) Synchronous Condenser means (IES-2001)

a) a Synchronous motor with capacitor connected across stator terminals to improve the power factor

b) a Synchronous motor operating at full load with leading power factor

c) Over excited synchronous motor partially supplying mechanical load, and also improving the power factor of system which is connected to it

d) Over excited synchronous motor operating at no load with leading power factor for improving power factor

2) DC series motor is accidentally connected to the single phase ac supply. The torque of the motor will be (IES-2002)

a) Zero average value

b) Oscillating

c) Steady and Uni  directional

d) Pulsating and Uni directional

3) The power factor of the synchronous motor (IES-2002)

a) Improves with increase in the excitation and may become leading at high excitation

b) Decrease with increase in excitation

c) Is independent of excitation

d) Increase with loading for a given excitation

4) In the case of auto transformers which of the following statements are correct (IES-2001)

a) An auto transformer requires less copper as compared to the conventional 2 winding transformer of the same capacity

b) Auto transformer provides isolation between the primary and secondary windings

c) An auto transformer has less leakage reactance compared to the conventional two winding transformer of same capacity

Select the correct answer:

a) 1,2 and 3

b) 1 and 2

c) 1 and 3

d) 2 and 3

5) When the excitation of the normally operating unloaded salient pole synchronous motor suddenly gets disconnected, it continues to run as (IES-2002)

a) Induction motor

b) Stepper motor

c) Switched reluctance motor

d) variable reluctance motor

6) The rotor power output of 3 phase induction motor is 15kW. The copper losses at a slip of 4% will be: (IES-2001)

a) 600 W

b) 625 W

c) 650 W

d) 700 W

7) An induction motor when started on load does not accelerate up to full speed but runs at 1/7 th of the rated speed. Then the motor is said to be under (IES-2001)

a) Locking

b) Plugging

c) Crawling

d) Cogging

8) The advantage of double squirrel cage induction motor over single case rotor is that (IES-2001)

a) Efficiency is higher

b) Power factor is higher

c) Slip is larger

d) Starting current is lower

Answers:

(1) d (2) d (3) a (4) c

(5) d (6) b (7) c (8) d