ECET EEE 2010-3

1. The following method is best suited for finding the voltage regulation of an alternator

A) Synchronous impedance method
B) Potier traingle method
C) MMF Method
D) Two reaction method

Answer : Potier traingle method
Explanation:-

2. Power factor of an alternator driven by constant prime mover input can be changed by changing its

A) speed
B) load
C) field excitaion
D) phase sequence

Answer : Load
Explanation:-

3. A four pole 3 - phase winding is placed in a stator that has 48 slots. The number of slots per pole per phase is

A) 4
B) 8
C) 16
D) 32

Answer :
Explanation:-

4. In an alternator, if XS is the synchronous reactance. XC is the leakage reactance, then the reactance Xa due to armature flux is given by

A) Xa=Xs+Xc
B) Xa=Xs-Xc
C) Xa=Xc-Xs
D) Xa=Xs^2+Xc^2

Answer : Xa=Xs-Xc
Explanation:-

5. A 3- phase, 4 - pole, 24 slot alternator has its armature coils short pitched by one slot. The pitch factor becomes

A) 0.94
B) 0.9659
C) 0.98
D) 1.00

Answer : 0.9659
Explanation:-

6. If the field of synchronous motor is under excited, there power factor will be

A) Leading
B) Lagging
C) Won't be effected
D) Unity

Answer : Lagging
Explanation:-

7. The starting torque of an induction motor is maximum when

A) Rotor resistance equals rotor reactance
B) Rotor resistance is twice the rotor reactance
C) Rotor resistance is half the rotor reactance
D) Rotor resistance is 2 times the rotor reactance

Answer : Rotor resistance equals rotor reactance
Explanation:-

8. At zero slip of an induction motor

A) The trans at synchronous speed
B) Motor nuns as a generator
C) Motor does not run
D) Slip produced is zero

Answer : Motor does not run
Explanation:-

9. The term crawling implies that the machine is

A) Running stably at speed greater than it synchronous speed
B) Running stably at speed as low as low as one seventh of its synchronous speed
C) Running at lower speed with a low supply voltage
D) Showing a transient behavior while running at higher loads.

Answer : Running stably at speed as low as low as one seventh of its synchronous speed
Explanation:-

10. Running stably at speed as low as low as one seventh of its synchronous speed

A) Adding a series c combination of a capacitor and auxiliary winding in parallel with the main winding
B) Adding an auxiliary winding in parallel with the main winding
C) Adding an auxiliary winding is series with a capacitor and the main winding
D) Adding an auxiliary winding in parallel with resistor and the main winding

Answer : Adding an auxiliary winding in parallel with the main winding
Explanation:-