Top Electrical Interview Questions And Answers On Electrical Special Machines

Q11. Draw the constant torque drive characteristics for induction motor.

Q12. Draw constant power characteristics for induction motor.

Q13. Draw torque slip characteristics of double cage Induction motor (IM).

Q14. What are the different ways of controlling slip?

Sol: the slip of an induction motor can be controlled by the following ways –

1.      Constant torque drive can be used for controlling the slip.

2.      Constant power drive can also be used for controlling slip.

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Q16. What do you understand by an isolated induction generator?

Sol: An isolated induction generator is an induction machine which works as a generator even without external supply system is provided to it. A three phase delta connected capacitor bank is connected across the terminals of the machine which provides a necessary excitation to the machine.

Q17. Write any two advantages of the induction generator.

Sol: following are the advantages of an induction generator –

1.  1.  An induction generator has a robust construction therefore it requires less maintenance.

2. An induction generator can run in parallel without hunting and it needs little auxiliary equipment.

Q18. What is a doubly fed induction generator?

Sol:  A doubly fed induction machine is a wound rotor doubly fed electric machine. It is an induction generator with multiphase wound rotor and a multiphase slip ring assembly with brushes for access to the rotor windings.

Q19. Explain the principle of doubly fed induction generator (DFIG).

Sol: The principle of the Doubly fed induction generator (DFIG) is that stator windings are connected to the grid and rotor winding are connected to the converter via slip rings and back-to-back voltage source converter that controls both the rotor and the grid currents. Thus rotor frequency can freely differ from the grid frequency (50 or 60 Hz).

Q20. What are the applications of the induction generator?

Sol: following are the applications of the induction generator –

1.                It is used in wind turbines.

2.                It is also used in small remote hydro plants.

3.                Regenerative hoist.

Q21. What do you mean by two phase AC servo motor?

Sol: A servo motor is a linear or rotary actuator that provides fast precision position control for closed loop position control applications. Servo motors works on servo mechanism that uses position feedback to control the speed and final position of the motor.

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