Common questions for interview???????????

1)what is the difference between electromagnetic torque and reluctance torque?

Ans:- electromagnetic torque- when a current carrying conductor(ie. rotor) is placed in a magnetic field.The rotor conductor experience a force in the upward direction and torque is developed in clockwise direction due to interaction of stator and rotor magnetic fields.

Reluctance torque-when ferromagnetic material is placed in the magnetic field due to excitation of stator coil.The rotor will immediately experience a counter clockwise torque because the magnetic flux has a tendency to follow a minimum reluctance path.The torque so produce is known as reluctance torque.

2) what is transformer?
Ans:- Transformer is a static machine which transfer ac power from one circuit to another circuit at same frequency but at different voltage level.

3)which one is suitable for transmit electricity in hilly area underground or overhead towerh
Ans:- overhead tower

4)why for 11 kV system,lightning arrester rating is 9 kV?
Ans:- L-G of 11 KV=11/√3=6.384
     And RMS voltage =6.384×√2=8.98~9kv
This is the maximums peak voltage across the lightning arrester.