Download Module- II, Lecture-1

Module- II, Lecture-1
D.C.Machines:
A machine which works on direct current is defined as a D.C.Machine.
D.C.Machines are of two types. (i) D.C.Generator and (ii) D.C.Motor.
Sl.No. D.C. Generator
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Definition:
Definition:
A generator is a rotating machine which
converts mechanical energy into electrical
energy
A motor is a machine which converts
electrical energy into mechanical
energy
Principle:
Principle:
Whenever a coil is rotated in a magnetic
field an e.m.f. will be induced in this coil
Whenever a current coil is placed
under a magnetic field the coil
experiences a mechanical force, and is
given by F= BIlSinθ Newtons/coil
side.
and is given by e=BlvSinθ volts/coil side
where, B=The flux density in Tesla, l=the
active length of the coil side in meters,
v=the velocity with which the coil is
moved in meters/sec and θ is the angle
between the direction of the flux and the
direction of rotation of the coil side.
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D.C.Motor
The direction of the emf induced is fixed
by applying the Fleming‟s right hand rule
Where, I is the current through the coil
in ampere.
The direction of the force acting is
fixed by applying the Fleming‟s left
hand rule.
Types and constructional features
Salient parts of a D.C.machine are:
 Field system (poles)
 Coil arrangement (armature)
 Commutator
 Brushes
 Yoke