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Name the motor which carries a single-phase exciting winding which is similar to the main winding of a single-phase induction motor that carries a distributed DC type winding.

Name the motor which carries a single-phase exciting winding which is similar to the main winding of a single-phase induction motor that carries a distributed DC type winding. Correct Answer Repulsion motor

Repulsion motor carries a single-phase exciting winding which is similar to the main winding of a single-phase induction motor that carries a distributed DC type winding.

Concept:

  • Repulsion Motor is a special kind of single-phase AC motor which works due to the repulsion of similar poles.
  •  The stator of this motor is supplied with a single-phase AC supply and the rotor circuit is shorted through a carbon brush.

Construction:

  • The main components of the repulsion motor are stator, rotor and commutator brush assembly.
  •  The stator carries a single-phase exciting winding similar to the main winding of a single-phase induction motor.
  • The rotor has distributed DC winding connected to the commutator at one end just like in the DC motor. The carbon brushes are short-circuited on themselves.

Figure shows the construction of a repulsion motor:

[ alt="F1 Jai Prakash Anil 22.01.21 D4" src="//storage.googleapis.com/tb-img/production/21/01/F1_Jai%20Prakash_Anil_22.01.21_D4.png" style="width: 275px; height: 208px;">

Working principle of Repulsion motor:

  • When the stator winding of the repulsion motor is supplied with single-phase AC, it produces a magnetic flux along the direct axis as shown in the figure above by arrow mark.
  • This magnetic flux when the link with the rotor winding, creates an emf. Due to this emf, a rotor current is produced.
  • This rotor current in turn produces a magnetic flux that is directed along the brush axis due to commutator assembly.
  • Due to the interaction of stator and rotor-produced fluxes, an electromagnetic torque is produced.


[ alt="F1 Jai Prakash Anil 22.01.21 D3" src="//storage.googleapis.com/tb-img/production/21/01/F1_Jai%20Prakash_Anil_22.01.21_D3.png" style="width: 356px; height: 225px;">

  • In the above figure, the angle α between the stator-produced field and brush axis is 90°.
  • This means the brush axis is in quadrature with the direct. Under this condition, there will not be any mutual induction between the stator and rotor windings.
  • Therefore, no emf and hence no rotor current is produced. Thus no electromagnetic torque is developed.


[ alt="F1 Jai Prakash Anil 22.01.21 D5" src="//storage.googleapis.com/tb-img/production/21/01/F1_Jai%20Prakash_Anil_22.01.21_D5.png" style="width: 313px; height: 158px;">

  • In this condition, a maximum emf is induced across the brushes. This is because the rotor and stator magnetic flux coincide and hence there is a perfect mutual coupling between them.

 

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