AP ECET EEE 2017-4

1. Which of the following connection of transformer will give the highest secondary voltage

A. Delta primary, delta secondary
B. Delta primary, star secondary
C. Star primary, star secondary
D. Star primary, delta secondary

Answer : Delta primary, star secondary
Explain:-

2. Two mechanically coupled alternators deliver power at 50hz and 60hz respectively. The highest speed of alternator is

A. 3600 rpm
B. 3000 rpm
C. 600 rpm
D. 500 rpm

Answer : 600 rpm
Explain:-

3. Which one of the following methods would give a higher than actual value of regulation of an alternator

A. ZPF method
B. MMF method
C. EMF method
D. ASA method

Answer : EMF method
Explain:-

4. In synchronous alternator, which of the following coils will have emf closer to sine wave form

A. concentrated winding in full pitch coils
B. concentrated winding in short pitch coils
C. distributed winding in full pitch coils
D. distributed winding in short pitch coils

Answer : distributed winding in short pitch coils
Explain:-

5. V-curve of synchronous motor shows the variation of

A. armature current and DC excitation at constant of load
B. supply voltage and field current at constant excitation
C. power factor and supply voltage during hunting
D. supply voltage and excitation current at constant load

Answer : armature current and DC excitation at constant of load
Explain:-

6. An ideal synchronous motor has no starting torque because the

A. rotor is made up of salient poles
B.relative velocity between the stator and rotor mmf's is zero
C. relative velocity between stator and rotor mmf's is not zero
D. rotor winding is highly reactive

Answer : relative velocity between stator and rotor mmf's is not zero
Explain:-

7. A synchronous motor is operating on no load at unity power factor. If the field current is increased, the power factor will become

A. leading and the current will decrease
B. lagging and the current will increase
C. lagging and the current will decrease
D. leading and the current will increase

Answer : leading and the current will increase
Explain:-

8. When the supply voltage for induction motor is reduced by 10% the maximum running torque will nearly

A. Decrease by 10%
B. Decrease by 20%
C. Increase by 10%
D. Increase by 20%

Answer : Decrease by 20%
Explain:-

9. As compared to DOL starting, a cage induction motor with star delta starting shall have

A. More starting torque
B. More starting current
C. Reduced starting current
D. smoother acceleration

Answer : Reduced starting current
Explain:-

10. A 6Pole 50Hz single phase induction motor runs at a speed 900rpm. The frequency/frequencies of current in the cage rotor will be

A. 5Hz
B. 5Hz,55Hz
C. 5Hz,95Hz
D. 55Hz,95Hz

Answer : 5Hz,95Hz
Explain:-