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Presented by:
Muhsin Ali Soomro (15 EL 32)
Assigned by :
R/sir. Engnr Suhail Ahmed Almani
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REPULSION MOTOR

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 Introduction
 Construction of repulsion motor
 Working principle
 Types of repulsion motor
 Advantages of repulsion motor
 Disadvantage of repulsion motor
 Application of repulsion motor
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CONTENTS

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 Repulsion motors are classified
under single phase motors.
 In magnetic repulsion motors
the stator windings are connected
directly to the ac power supply and
rotor is connected to commutator
and brush assembly , very similar to
that of DC armature.
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INTRODUCTION

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 The repulsion motor has operating characteristics
similar to those of the series DC motor.
 It has a stator with a winding similar to that of a
split-phase motor without the starting winding.
 The rotor is similar to the armature of a DC
motor, but it has no electrical connection to the
supply line. The brushes are short-circuit.
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CONSTRUCTION OF REPULSION MOTOR

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 Repulsion motors are based on the principle of
repulsion between two magnetic fields.
 Consider a 2-pole motor with a vertical
magnetic axis.
 The armature is connected to a commutator
and brushes.
 The brushes are short circuited using a low-
resistance jumper.
 When alternating current is supplied to the
field (stator) winding, it induces an
electromotive force (emf) in the armature.
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WORKING PRINCIPLE

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 The direction of alternating current
is such that it creates a north pole at
the top and a south pole at the bottom.
 The direction of induced emf is given by
Lenz's law
 The induced e.m.f induces current in the
armature conductors and the direction
of the induced current depends on the
position of the brushes.
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WORKING PRINCIPLE (CONTINUE . . .)

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 The direction of induced emf is given by Lenz's
law, according to which the
direction of induced emf opposes the
cause producing it.
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LENZ’S LAW

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CIRCIUT DIAGRAM OF REPULSION MOTOR

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The various types of motors which works under
the repulsion principle are :
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COMPENSATED REPULSION MOTOR
REPULSION-START INDUNTION MOTOR
REPULSION INDUCTION MOTOR
TYPES OF REPULSION MOTOR

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 It carries an additional winding, called compensating
winding.
 There is another set of two brushes which are placed
midway between the usual short circuit brush set.
 The compensating winding and this added set are
connect in series. In order to neutralize the cross
magnetizing effect of armature reaction The series-
connected compensating windings produce a
magnetic field, which varies directly with armature
current.
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COMPENSATED REPULSION MOTOR

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 This motor starts as a repulsion motor, but
normally run as an induction motor, with
constant speed characteristics.
 It consist,
• One stator
• One rotor which is similar to the wire-wound
d.c armature
• A commutator and
• A centrifugal mechanism which short-circuits
the commutator bars.
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REPULSION-START INDUNTION MOTOR

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REPULSION-START INDUNTION MOTOR (CONTINUE . . .)

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 It works on the combined principle of repulsion
and induction. It consist,
• Stator winding
• Two rotor winding : one squirrel cage and other
usual d.c winding connected to the commutator and
• A short-circuit set of two brushes
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REPULSION INDUCTION MOTOR

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 Most commutator motors are limited to
about 1,500 volts because higher voltages give
rise to a risk of arcing across the commutator.
 Repulsion motors can be used at higher voltages
because the rotor circuit is not electrically
connected to the supply
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ADVANTAGES OF REPULSION MOTOR

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 Occurrence of sparks at brushes.
 Commutator and brushes wear out quickly.
This is primarily due to arcing and heat
generated at brush assembly.
 The power factor is poor at low speeds.
 No load speed is very high and dangerous.
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DISADVANTAGES OF REPULSION MOTOR

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 Agitators
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APPLICATIONS

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APPLICATIONS (CONTINUE . . .)

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