09/03/2020

Single Phase Induction Motor Interview Question Answer - 2


21
Which type of capacitor is used in the two value capacitor motor?


Electrolyte capacitor : Short duty
Oil capacitor : Continuous duty


22
How the optimum starting and running characteristics is obtained in the two value capacitor motor?


Optimum starting and running characteristic
  • The two capacitors are in parallel during starting in the two value capacitor motor. 
  • When the motor speed reaches 75% of the full load speed, the centrifugal switch open and only one capacitor of continuous duty remains in the circuit.


23
What should be rating of starting capacitor as compared to running capacitor in the two value capacitor motor?


The rating of starting capacitor ( Short duty rating ) is approximately 10 to 15 times that of running capacitor ( Continuous duty rating ).

24
State the salient features of the two value capacitor motor.


Salient features of two value capacitor motor
  • Noiseless operation
  • High efficiency
  • High power factor
  • Overload capacity up to 125%
  • Ability to start against heavy load


25
How the phase splitting is done in the shaded pole induction motor?


The phase splitting in the shaded pole induction motor is done by induction.

26
Which type of stator and rotor the shaded pole induction motor consists of?


Shaded pole induction motor
  • Stator : Salient pole
  • Rotor : Squirrel cage


27
Where the shading ring is placed in the shaded pole induction motor?


Shading ring
  • The stator of the shaded pole consists of salient poles.
  • The salient pole has small cut across the lamination approximately one third distance from one end and shading ring is placed on this cut.


28
State the direction of flux rotation in the shaded pole motor?


Unshaded pole to shaded pole

29
State the salient features of the shaded pole motor.


Salient features
  • Low efficiency ( 5% up to 35% )
  • Low overload capacity
  • Low starting capacity


30
State the applications of the salient pole motor.


Application
  • Small toys
  • Hair dryers
  • Ventilators
  • Electrical clocks
  • Small fan
  • Advertising display boards
  • Phonograph turntables


31
Whether the direction of shaded pole motor can be reversed? Why?


The direction of the shaded pole motor cannot be reversed due to fixed position of shaded ring.

32
Describe the different types of repulsion motor.


Types of repulsion motor
  • Repulsion motor
  • Compensated repulsion motor
  • Repulsion start induction run motor
  • Repulsion induction motor


33
Which type of construction does the repulsion motor consist of?


Repulsion motor
  • Stator : Salient pole, non – distributed winding
  • Rotor  : Similar to DC armature
  • Commutator and carbon brushes


34
On which parameter the armature induced emf depends in the repulsion motor?


The armature induced emf in the repulsion motor depends upon the position of the short circuited brushes.

35
What is reason behind the name of motor called as ‘repulsion motor’?


Repulsion motor
  • The rotor of the repulsion motor rotates due to repulsion force between stator N pole and rotor N pole ( or stator S pole and rotor S pole ) therefore it is called as repulsion motor.


36
On which parameter the starting torque of the repulsion motor depends?


The starting torque of the repulsion motor depends upon the amount of brush shift.

37
Which method is used to control speed of the repulsion motor?


The speed control of the repulsion motor depends upon brush shift.

38
Describe the function of compensating winding in the compensated repulsion motor.


Function of compensating winding
  • Provides better speed regulation
  • Improve power factor


39
Where the compensating winding is provided in the compensated repulsion motor?


The compensating winding is provided in the inner slot of the main pole and it is connected in series with armature winding.

40
How many brushes the compensated repulsion motor consists of?


The compensated repulsion motor consists of two pair of brushes.


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