Repulsion motor

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1. 1 /20 3/20/2018 QUEST NAWABSHAH

2. 2 /20 Presented by: Muhsin Ali Soomro ( 15 EL 32 ) Assigned by : R/sir. Engnr Suhail Ahmed Almani 3/20/2018 QUEST NAWABSHAH REPULSION MOTOR

3. 3 /20 Introduction Construction of repulsion motor Working principle Types of repulsion motor Advantages of repulsion motor Disadvantage of repulsion motor Application of repulsion motor 3/20/2018 QUEST NAWABSHAH CONTENTS

4. 4 /20 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. 3/20/2018 QUEST NAWABSHAH INTRODUCTION

5. 5 /20 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. 3/20/2018 QUEST NAWABSHAH CONSTRUCTION OF REPULSION MOTOR

6. 3/20/2018 6 /20 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. QUEST NAWABSHAH WORKING PRINCIPLE

7. 7 /20 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. 3/20/2018 QUEST NAWABSHAH WORKING PRINCIPLE (CONTINUE . . .)

8. 8 /20 The direction of induced emf is given by Lenz's law, according to which the direction of induced emf opposes the cause producing it. 3/20/2018 QUEST NAWABSHAH LENZ’S LAW

9. 9 /20 3/20/2018 QUEST NAWABSHAH CIRCIUT DIAGRAM OF REPULSION MOTOR

10. 10 /20 The various types of motors which works under the repulsion principle are : 3/20/2018 QUEST NAWABSHAH COMPENSATED REPULSION MOTOR REPULSION-START INDUNTION MOTOR REPULSION INDUCTION MOTOR TYPES OF REPULSION MOTOR

11. 11 /20 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. 3/20/2018 QUEST NAWABSHAH COMPENSATED REPULSION MOTOR

12. 12 /20 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. 3/20/2018 QUEST NAWABSHAH REPULSION-START INDUNTION MOTOR

13. 13 /20 3/20/2018 QUEST NAWABSHAH REPULSION-START INDUNTION MOTOR (CONTINUE . . .)

14. 14 /20 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 3/20/2018 QUEST NAWABSHAH REPULSION INDUCTION MOTOR

15. 15 /20 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 3/20/2018 QUEST NAWABSHAH ADVANTAGES OF REPULSION MOTOR

16. 16 /20 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. 3/20/2018 QUEST NAWABSHAH DISADVANTAGES OF REPULSION MOTOR

17. 17 /20 Agitators 3/20/2018 QUEST NAWABSHAH APPLICATIONS

18. 18 /20 3/20/2018 QUEST NAWABSHAH APPLICATIONS (CONTINUE . . .)

19. 19 /20 3/20/2018 QUEST NAWABSHAH By Muhsin ALI Soomro V I C T O R Y V ery I ntense C are T racing o pportunity R ewarded To Y ou

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