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DC GENERATOR

Presented by,
KAVYASHREE. S

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INTRODUCTION TO DC GENERATOR


An dc generator is a machine which converts mechanical energy or power into electrical energy.

WORKING PRINCIPLE

It is based on the principle of production of dynamically induced e.m.f. (electro motive force). Whenever a conductor cuts magnetic flux, dynamically induced e.m.f is prodused in it according to Faraday’s Laws of Electro magnatic Induction. This emf causes a current to flow if the conductor circuit is closed.

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D.C GENERATOR
WHAT IS GENERATOR?
WHAT IS THE PRINCIPLE ?
 An generator is a machine which converts mechanical energy into electrical energy.
 Principle of generator is the production of dynamically induced e.m.f according to FARADAY’S LAWS OF ELECTROMAGNETIC INDUCTION.
MAIN PARTS OF D.C GENERATOR
 YOKE.
 POLE CORE AND POLE SHOE.
 FIELD COIL.
 ARMATURE CORE.
 ARMATURE WINDING.
 COMMUTATOR.
 BRUSHES AND BRUSH HOLDERS.
 BEARINGS.
 SHAFT.
YOKE:
 It provides mechanical support for the poles and as a protecting cover for the whole machine.
 It carries the magnetic flux produced by the poles.
POLE CORE AND POLE SHOE:
 The main function of pole core is to act as support for the field coils carries current which surrounds it and establish magnetic flux.
 The main function of pole shoe are it supports the field coil it spreads out the magnetic flux over a larger area.
FIELD COILS:
 Field coils are also called pole coils.
 When current is passed through these coils, they electromagnetise the poles which produce the necessary flux that is cut by revolving armature conductors.
ARMATURE CORE:
 Armature is the rotating part.
 It provides a path of very low reluctance to the flux through the armature from NORTH pole to SOUTH pole.
 It is cylindrical or drum shaped.
ARMATURE WINDING OR CONDUCTORS:
 Armature windings consists of conductors or copper wires which are placed in slots.
 It is of two types
 Open coil winding and
 Closed coil winding.
 Open coil winding is used in A.C machines.
 Closed coil winding is again divided into 2 types.
 Ring winding and Drum winding.
 Drum winding is again divided into two types.
 Lap winding and Wave winding.
 Lap winding is used for low voltages and high currents.
 Wave winding is used for high voltages and low currents.
 In lap and wave winding back pitch and front pitch are equal to the pole pitch.
 Number of commutator segments is equal to the number of slots or coils.
 Pole pitch is equal to the number of conductors per pole.
COMMUTATOR:
 The function of commutator is to facilitate collection of current from the armature conductor.
 It also converts the alternating current induced in the armature conductors into unidirectional current in the external load circuit.
BRUSHES AND BRUSH HOLDERS:
 The main function of brushes is to collect the current from commutator.
 Brushes are housed in the brush holders.
 These brush holders are used for the protection purpose to the brushes.
 Total number of brushes is equal to the number of poles.
BEARINGS AND SHAFT:
 Bearing and shaft are mainly used for smoothing operation because of their reliability.
 Ball bearings are frequently employed, through for heavy duties, roller bearing are preferable
ARMATURE REACTION:
 Armature reaction is meant the effect of magnetic field set up by armature current on the distribution of flux under main poles of a generator.
 This armature reaction has two effects.
 1.DEMAGNETISING EFFECT.
 2.CROSS MAGNETISING EFFECT