Single Phase Induction Motors Single Phase Induction Motors Inductor Capacitor
Single Phase Induction Motors Single Phase Induction Motors Inductor Capacitor
Single Phase Induction Motors Single Phase Induction Motors Inductor Capacitor
The single phase induction motors are not self starting, therefore are made self starting by
providing an additional flux by some additional means. Now depending upon these additional
means the single phase induction motors are classified as:
1.
Split phase induction motor.
2.
Capacitor start inductor motor.
3.
Capacitor start capacitor run induction motor ( two value capacitor method).
4.
5.
We know that for highly resistive winding the current is almost in phase with the voltage and for
highly inductive winding the current lag behind the voltage by large angle. The starting winding is
highly resistive so, the current flowing in the starting winding lags behind the applied voltage by very
small angle and the running winding is highly inductive in nature so, the current flowing in running
winding lags behind applied voltage by large angle. The resultant of these two current is IT. The
resultant of these two current produce rotating magnetic field which rotates in one direction. In split
phase induction motor the starting and main current get splitted from each other by some angle so
this motor got its name as split phase induction motor.
Applications of Split Phase Induction Motor
Split phase induction motors have low starting current and moderate starting torque. So these motors
are used in fans, blowers, centrifugal pumps, washing machine, grinder, lathes, air conditioning fans,
etc. These motors are available in the size ranging from 1 / 20 to 1 / 2 KW.
2) Capacitor Start IM
The working principle and construction of Capacitor start inductor motors and capacitor start
capacitor run induction motors are almost the same. We already know that single phase induction
motor is not self starting because the magnetic field produced is not rotating type. In order to produce
rotating magnetic field there must be some phase difference. In case of split phase induction motor we
use resistance for creating phase difference but here we use capacitor for this purpose. We are familiar
with this fact that the current flowing through the capacitor leads the voltage. So, in capacitor start
inductor motor and capacitor start capacitor run induction motor we are using two winding, the
main winding and the starting winding. With starting winding we connect a capacitor so the current
flowing in the capacitor i.e Ist leads the applied voltage by some angle, st.
The running winding is inductive in nature so, the current flowing in running winding lags behind
applied voltage by an angle, m. Now there occur large phase angle differences between these two
currents which produce an resultant current, I and this will produce a rotating magnetic field. Since
the torque produced by these motors depends upon the phase angle difference, which is almost 90.
So, these motors produce very high starting torque. In case of capacitor start induction motor, the
centrifugal switch is provided so as to disconnect the starting winding when the motor attains a speed
up to 75 to 80% of the synchronous speed but in case of capacitor start capacitors run induction
motor there is no centrifugal switch so, the capacitor remains in the circuit and helps to improve the
power factor and the running conditions of single phase induction motor.
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P
ower Circuit
Power Circuit