Best And Free Electrical Interview Questions Bank On DC Motor!!

Best And Free Electrical Interview Questions Bank On DC Motor!!

Interview Questions On Working Principle Of DC Motor

1) define function of DC Motor???
Ans: An electric motor is a machine which converts electric energy into mechanical energy.

2) In d.c. motor conductor is experienced force by whose principle??

Ans: Fleming's Left-hand Rule

3)what is the function of commutator in d.c. motor??
Ans: the function of a commutator in the motor is the same as in the generator. By reversing current in each conductor as it passed from one pole to another, it help to develop a continuous and unidirectional torque.

4) In lathes machine which type of motor are uses???
Ans:shunt type d.c. motor

5)where the  series type d.c motor are used??
Ans:
* For traction work i.e. Electric locomotives
*Rapid transut system
*Trolley, cars etc.
*Cranes and hoists
*Conveyors

6)For intermittent high torque loads which motor are used??
Ans: Comulative compound type d.c. motor

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Interview  Questions On Losses in DC Machine

1)list The losses occurring in dc machines ???
Ans: listed as below:
(1) copper losses
(2) Magnetic or iron losses
(3) Mechanical losses

2) give The various copper losses occurring in the windings ??????
Ans:
(A)  Armature copper loss
(B) Shunt field copper loss
(C) Series field copper loss
(D) Copper loss in interpole winding
(E) Brush contact loss

Ans:30-40 and  20-30

4)Magnetic losses is also known as????
Ans:These losses are also called iron loss or core loss.

5)magnetic loss consist which losses???
Ans:Iron losse consists of (1) Hysterisis losses and (2) Eddy current losse.

Ans: 20% to 30%

7)explain hysteresis losses in dc machine???
Ans:Hysterisis losses

This loss is due to reversal of magnetism of the armature core.
These losses pccur in armature core teeth of the dc machine.
Hysteresis losses can be reduced by using core material of silicon steel which has low hysterisis coefficient.

8)define eddy current???
Ans:When armature core rotates in magnetic field of poles it also cuts the magnetic flux. Hence an emf is induce in the body of the core according to the low of electromagnetic induction. This emf set up current in the body of the armature core and its know as eddy current

9)mechanical losses consists which losses???
Ans:(a)  Bearing and brush friction losses
(b)  Winding loss or air friction of rotating armature.

10)stray losses occurring because of???
Ans:(1)Distortion of flux because of armature reaction
(2)due to eddy current in conductore
(3)short circuit current in the armature coil undergoing commutation.

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Interview Questions Related To Armature  Reaction

1)The armature magnetic field has how manny effects and which???
Ans: Two
(1) It demagnetises or weakens the main flux and
(2) It cross-magnetises or distorts.

2) what is the full form of G. N. A???
Ans: geometrical neutralaxis or plane(G.N.A.)

3)define Magnetic neutral axis???
Ans: as the axis along which no e.m.f. is produced in the armature conductors because they then move parallel to the lines of flux.

Ans:It is the end of the pole which first comes in contact with armature in the direction of rotation by the armature conductors.

5) give the fullform of TPT and define TPT???
Ans:Trailing Poles Tip(TPT)
It is the end of the pole which comes in contact later with the armature in the direction of rotation.

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Interview Questions On Different Types Of Magnetic Exciting System

1)how many type for Exciting to Magnetic System??
Ans: two type (1) single excited and (2) doubly excited

2)Give the formula of  The incremental electrical energy (dWe)  due to the flow of current in the Single Excited System??
Ans: dW=E.i dt

3)Give the formula For angular movements of armature  the electromagnetic torque for a linear system ???

T=(1/2)*(i^2)*(dL/d§)
Where §=angle

4)What is Doubly Excited Magnetic System??
Ans:A magnetic system which is excited by two independent source is called doubly excited magnetic circuit.

5) Give the example of Doubly Excited Magnetic System??
Ans:The synchronous machines and d.c. machines .

6)Give formula for satisfied the energy conversion principle in Doubly Excited Magnetic System??
Ans: dWe = dWm + dWf

7)Give the formula of Magnetic torque developed in Doubly Excited Magnetic System??
Ans:Tm d§ =(1/2)(i^2) dLs + (1/2)(ir^2) dLr +(is) (ir) dM
Where §=anglr
Ir= rotor current
Is= stator current

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