GANDHINAGAR INSTITUTE OF TECHNOLOGY

Presentation on ::

COMMUTATOR MOTORPRESENTATION BY:

NAROLA KAUSHAL J.(140123109006)

PANCHAL SIDDHARTH A. (140123109013)

GUIDED BY :

Prof. SUPRAJA MAM

WE ARE INTRODUTION TWO MOTORS:

(1)THREE PHASE SCHRAGE MOTOR

(2)REPULSION MOTOR

INTRODUCTION

SCHRAGE Motors:

It is use commutator for taking current from supply & producing unidirectional torque. It is work on AC & DC Supply.

Two type of AC Commutator Motors,1. Single phase AC Commutator motors2. Three phase AC Commutator motors

THREE PHASE SCHRAGE MOTOR:

Detail study of the following:

(1)Introduction(2)Construction details(3)Working(4)Characteristics(5)Advantages (6)Disadvantages(7)uses

(1)INTRODUCTION:

This motor is three phase, A.C commutator motor.

It is basically an circuit for speed control.

It’s disadvantages is that speed cannot be varied easily.

It is an inverted induction motor with unibuilt frequency convertor.

(2) CONSTRUCTIONAL DETAILS:

ROTOR:

It is cylindrical part made of silicon steel.It is fitted on shaft and shaft is free to rotate.

STATOR:

It is a outer cylindrical part.Stator core is made up of silicon steel stampings and slots to accommodate stator.

COMMUTATOR:

It is made up of copper segments insulated by mica segments of commutator.It is fitted on the same shaft on which the rotor is fitted.

SLIP RINGS & BRUSHES:

The slip rings are made of phosporbronze.A unit of three slip rings is mounted on the shaft.Rotor winding is connected to the slip rings carbon brushes.The power is fed to the rotor via brushes and slip rings.The function of brushes is to collect the required e.m.f from the commutator and to inject it into stator secondary winding.

(3) WORKING:

The 3-phase,50 Hz, supply is connected to the rotor primary winding through slip rings.The working flux in the air gap is produced.Regulating winding is housed in the upper portion of the slots.The primary and secondary winding are just as of induction motor and thus e.m.f induced in the secondary winding by induction motor action.The line frequency voltage induced in the regulating winding is converted to the slip frequency by commutator and injected into secondary winding.

LOAD POWER FACTOR

SPEED (N)

EFFICIENCY

IT IS STARTED WITH BRUSHES IN LOWEST SPEED BY DIRECT ON CONTACTOR STARTER.

CHARACTERISTICS OF SCHRAGE MOTOR:

ADVANTAGES:

Wide variation of speed ranges are obtained.Speed control is simpler.P.F can be adjusted easily.

DISADVANTAGES:

Complicated structure.More losses.Efficiency is less.

USES OF SCHRAGE MOTOR:

Paper millsSpinning millsCranesHoistsBoiler drought fansTextile machinery

REPULSION MOTOR:

CONSTRUCTIONAL DETAILS:

1) STATOR2) ROTOR3) COMMUTATOR4) BRUSHES

(1) STATOR & STATOR WINDINGS:

Non salient type distributed. It is put in the stator slots. It is wound for 4,6,8 poles.

(2) ROTOR:

It is same as armature of D.C motor.It is having slots in which lap or wave winding is put.

(3) COMMUTATOR:

It is made of Cu and mica segments.It is connected to the commutator segments.

(4) CARBON BRUSHES:

They are placed in the holder & kept touching with commulator.The brushes are shorted by connecting directly with a cu wire.

VERTICAL BRUSH AXIS:

If brush axis is vertical the direction of current and e.m.f will be shown.

E.M.F induced in the armature conductor will be an such direction that magnetic effect produced by if will oppose the stator flux.The rotor will behave like electromagnet and N & S polarities are developed on it.N pole portion of rotor will exactly facing the stator pole.S pole formed on the rotor will be exactly facing the s pole of stator.

HOROZONTAL BRUSH AXIS:

This brush axis is perpendicular to stator magnetic axis.

In case voltage will be produced but the brush position being horizontal & the voltage will be neutralized.

Voltage will be zero between brushes.So current will be zero hence there will not be any torque produced.

Thus motor will not start in brush position if vertical or horizontal.

The speed of this motor can be changed by shifting the brushes.The direction of rotation can be change by shifting brushes in the reversed direction.

DROWBACKS OF REPULSION MOTOR:

Very low power factor.Very high speed at no load.Speed not constant but varies with load.Poor commutation and heavy sparking.

APPLICATIONS:

Mixing m/c refrigerator.Grinding devices.PumpsCompressorsLiftFloor polishing machine

THANK YOU