Name : Divyesh (140050111016)
Chandni (140050111018)
Priyal (140050111021)
Anjali (140050111015)
Div. : EC-01
Sub. : Electrical Machines
Sub.Code : 2131005
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The single phase induction machine is the most
frequently used motor for refrigerators,washing
machines,clocks,drills,compressors,pumps,and
so forth.
The single phase motor stator has a laminated
iron core with teo windings arranged
perpendicularly.
1. One is main and
2. The other is the auxiliary winding or
starting winding
Single phase induction motor
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This single phase motor
are truly two-phase
machines.
The motor uses a
squirrel cage
rotor,which has a
laminated iron core with
slots.
Aluminium bars are
molded on the slots and
short circuited at both
ends with a ring.
Squirrel cage rotor
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The single phase induction motor opration can be
described by two methods:
1. Double revolving field theory and
2.Cross-field theory
1.Double revolving field theory
A single phase ac current supplies the main
winding that produces a pulshing magnetic field.
Mathematically,the pulsating field could be
divided into two fields,which are rotating in
opposite direction.
The interaction between the fields and the current
induced in the rotor bars generates opposing
torque.
2.Cross field theory
The stator winding is excited by the single phase
a.c. Supply .
This supply produces an alternating flux s which
acts along the axis of the stator winding.
Due to this flux,e.m.f.,gets induced in the rotor
conductors due to tranformer action.
As rotor is closed one,this e.m.f. Circulates current
through the rotor conductors.the direction of the
rotor current is as shown in the fig. .
The direction of rotor current is so as to oppose the
cause producing it, which is stator flux s.
Working principle
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Assume no current is
flowing through the
auxiliary winding .
AC current passing
through the main
winding will produce
a fluctuating magnetic
field.
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The working of single phase induction motor is
simple.
Just put one rotor which is already rotating
,inside such a magnetic field.
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The single phase motor starting torque is zero
because of the pulsating single phase magnetic
field.
The starting of the motor requires the
generation of a rotating magnetic flux similar
to the rotating flux in a three-phase motor.
Two perpendicular cois that have current 90º
out of phase can generate the necessary
rotating magnetic field which start the motor .
Therefore,single phase motors are built with
two perpendicular windings.
Thank you ..........