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Electrical Engineering Interview Question On Electric Driver

Q. What is an Electric Drive?

A. The entire unit consisting of an electric motor, the energy transmitting shaft and the control equipment is called an electric drive.

Q. What are the advantages of electric drives?

A. 1. These drives are available in wide range torque, speed and power.
2. Flexible control characteristics.
3. They are adaptable to any type of working conditions
4. They can operate in all the four quadrants of speed torque plane, which is not applicable for other prime movers.
5. The operation is pollution free.
6. Lower noise, less maintenance.
7. Their efficiency is high as no load losses are less

Q. What are the different classes of duty?

A. continuous duty: Operation at a constant load for long duration of time.
Continuous duty, variable load: Sequence of identical duty cycles consisting of periods of operation under load and no load.
Short time duty: Operation at a constant load for small period of time followed by rest.
Intermittent periodic duty: Sequence of identical duty cycles each consisting of a period of operation at a constant load and then a period of rest.

Q. What are the four quadrants of operation?

A. Forward motoring, Reverse motoring, Forward regeneration and Reverse regeneration.

Q. What are the different types of electric braking?

A.    1. Dynamic or Rheostatic braking
    2. Plugging
    3. Regenerative breaking

Q. Explain Plugging?

A. In plugging the polarity of the supply voltage to the armature is reversed while the motor is running

Q. Explain Regenerative braking?

A. When the field current is increased and the motor speed does not decrease instantly, i.e if the speed exceeds the no load speed for the new value of field current or flux, the back emf exceeds supply voltage and thus the machine acts as a generator. This is called regeneration and the form of braking is called regenerative braking.


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