Skip to main content

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.


Thanks for reading.
Labels:

Comments

Post a Comment

Comment Policy
We’re eager to see your comment. However, Please Keep in mind that all comments are moderated manually by our human reviewers according to our comment policy, and all the links are nofollow. Using Keywords in the name field area is forbidden. Let’s enjoy a personal and evocative conversation.

Popular posts from this blog

Practical Commutation

The e.m.f. induced in each coil of armature is alternating in nature. If load is connected, the current flowing will also be alternating. But the flow of current in a d.c. generator must be undirectional. This can be achieved by the use of commutator. When the armature conductors are under the influence of one pole they carry current in one direction whereas the current is reversed when the conductors are under the influence of other pole. This reversal of current takes place along the magnetic neutral axis. Fig. 1 Note : The reversal of current is likely to take place in short interval when a coil is short circuited by a brush so that transfer of current from one direction to other is carried out without any sparking. This process is called commutation.        Thus a process by which current in the short circuited coil is reversed while it crosses the MNA is called commutation. The time during which the coil remains short circuited is known as...
1 comment
Read more

Demagnetising and Cross Magnetizing Conductors

The conductors which are responsible for producing demagnetizing and distortion effects are shown in the Fig.1. Fig. 1        The brushes are lying along the new position of MNA which is at angle θ  from GNA. The conductors in the region AOC = BOD = 2θ  at the top and bottom of the armature are carrying current in such a direction as to send the flux in armature from right to left. Thus these conductors are in direct opposition to main field and called demagnetizing armature conductors.         The remaining armature conductors which are lying in the region AOD and BOC carry current in such a direction as to send the flux pointing vertically downwards i.e. at right angles to the main field flux. Hence these conductors are called cross magnetizing armature conductors which will cause distortion in main field flux.        These conductors are shown in the Fig. 2 Fig. 2  ...
Post a Comment
Read more

Armature Voltage Control Method or Rheostatic Control of dc motor

Speed Control of D.C. Shunt Motor (Part2)  2. Armature Voltage Control Method or Rheostatic Control        The speed is directly proportional to the voltage applied across the armature. As the supply voltage is normally constant, the voltage across the armature can be controlled by adding a variable resistance in series with the armature as shown in the Fig. 1. Fig. 1 Rheostat control of shunt motor        The field winding is excited by the normal voltage hence I sh is rated and constant in this method. Initially the reheostat position is minimum and rated voltage gets applied across the armature. So speed is also rated. For a given load, armature current is fixed. So when extra resistance is added in the armature circuit, I a remains same and there is voltage drop across the resistance added ( I a R). Hence voltage across the armature decreases, decreasing the speed below normal value. By varyi...
Post a Comment
Read more