Describes how the Pich Faactor functions......

1. -Debraj Das(130370111011)
-Deepak Singh(130370111012)

2.  In power stations, 3-Φ AC
generator is used to produced 3-
Φ voltage with low magnitude.
This low magnitude of voltage
is increased by using power
transformer.
 The machine which generates 3-
Φ electric power from the
mechanical power is called an
alternator or synchronous
generator. The shaft of the
generator is coupled with
mechanical turbine. The turbine
may be gas, steam or water.
 A synchronous machine with
no-load is called asynchronous
condenser or dynamic capacitor
(used to correct the power
factor).

3. Stator
 The stator is the stationary part
and is made of thin laminations
of highly permeable steel to
reduce losses.
 The stator has ample number of
slots in its inner periphery for
stator winding.
 The conductors are placed in the
slots in a suitable way.The ends
of theconductors are connected
either in Υ or Δ to form the
balanced 3 -Φwinding.
Rotor
 It is the inner part of the
alternator.It contains the field
windings which are energized
by direct current from the
separate dc source.

4.  Rotor winding is initially energized
by a separate dc source.
 A dc field current flows through the
rotor field winding that establishes a
flux in the air-gap which does not
vary with time.
 A rotating field of constant
magnitude is produced in the air-gap
when the rotor rotates due to a
primemover.
 The stator conductors are cut by this
rotating flux, so that a voltage is
induced in the armature conductors.
If the rotor rotates
continuously,then 3-Φ A C voltag e
will be induced in the armature
conductors.
 .

5. With reference to fig, the
two conductors AB
and CD alongwith
their end connections
constitute one coil of
the armature winding.
The coil may be single
turn or multi-turn
coil. A single turn coil
will have two
conductors.

6.  The pitch factor is defined as the ratio of voltages
generated by the short pitch winding to that which
is generated in the full pitch winding.
 Kp= (voltage induced in the short pitch
coil)/(voltage induced in the full pitch coil)
 Let the rms value of the coil side voltage is Ecsand
the resultant coil voltage is Ecr.
 For full pitch winding:Ecr=2Ecs
 For short pitch winding:Ecr=2Ecscos( )2/ ץ
 Finally the pitch factor becomes,kp=cos( )2/ ץ