Methods to start a
single phase induction motor or types of single phase induction motor.
In the last article we
have discussed about a single phase induction motor. In this article we will
see the operating procedure to start an Induction motor.
Single phase induction
motor isn’t a self starting motor. It needs to be made self starting by
following three methods.
Split phase induction
motor:
In this method of
starting single phase induction motor, it consists of two windings one is
called the main winding and the other is known as auxiliary winding. Both
windings are split at 90 degree to each other that is making an angle of 90
degree. In a split phase induction motor winding are connected parallel to each
other they are made from resistor and capacitor. The main winding of this motor
consists of low resistance and high inductive reactance but in second winding
the resistance is high and the inductive reactance is low, due to which when
the current goes through the windings. A phase difference occurs and a rotatory
magnetic field is produced making the motor to rotate.
Capacitor starts
induction motor:
Two windings of this
motor is common in all types of single phase induction motor. The primary
winding is called main winding and the secondary winding is called auxiliary.
Starting or main winding is mainly used to start the motor, the main propose of
starting winding is to create starting torque to rotate the rotor. The
construction of the motor is same as split phase but it has a capacitor in it,
connected in series with the starting winding and a centrifugal switch is
connected with the starting winding the main aim of this is which is to isolate
the starting winding from the circuit. In a capacitor from start induction
motor case type rotor issued. When we apply A.C supply to both windings the
motor, the current after passing winding comes to the capacitor. The capacitor
current leads the voltage and the current legs by 90 degree from the voltage in
the running winding. This causes a large Phase difference in the current so as
motor starts to rotate.
Capacitor start
Capacitor run induction motor:
The construction of
this motor is same as previous motors, but it includes two capacitors. It is
also known as dual run capacitor motor. One capacitor is used to give starting torque
to the motor and is called the starting capacitor. The starting capacitor is
connected in series with the starting winding the starting capacitor has a low
capacity reactance allowing more current to pass. The other capacitor is called
running capacitor. Running capacitor has high capacitive reactance due to which
low current is passed through it. When the motor gains 70 to 80% speed the starting
capacitor is isolated by the centrifugal switch from the circuit. This causes
phase difference and motor starts.
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