Types Of Single Phase Induction Motors

There are five types of single phase induction motor they are

a, Split phase induction motors,
b, Capacitor start induction motors,
c, Capacitor start and run induction motor,
d, Shaded pole induction motor,
e, Repulsion start induction motor.
Of these ,the first three are most commonand so we shall discuss them only in here.

a, Split phase induction motor

We know that normally in all single phase induction motors ,there are two windings namely starting winding(auxillary winding) and running winding(main winding), these two coils are connected in parallel in the split phase induction motor.the centrifugal switch is normally closed and when the motor is started and reaches 80% of its full speed ,the switch opens to disconnect the starting winding which is connected in parallel to the running winding by means of a centrifugal switch. Starting coil has high resistance and low inductive reactance,whereas running coil has low resistance and high inductive reactance.The current on both the starting and running coils are lagging in nature.The phase angles between the starting and running coils is 40-50 degrees.The torque in this motor is low.Its effeciency is around50%.

Applications

Fans,pumps,blowers,etc

b,Capacitor start induction motor

Here the capacitor is aditionally added in between the centrifugal switch and starting winding,because of the addition of capacitor the output power is increased phase angledifference between starting and running coils is approximately 90 degrees power factor is increased due to the addition of capacitor,starting torque is increased and effeciency is also increased.starting current leads the running currrent effeciency is around 55%,starting torque is 350 times of full load torque.

Applications

Compressors,conveyors,air conditioners,etc

c,Capacitor start and run induction motor

Incase of capacitor start motor the capacitance is at the time of starting only and ant the time ofrunning at full speed(rated) it is cut off,but here the capacitor runs till the supply is turned off and so there is an improved effeciency,(i.e) its effeciency is around 65-70%,starting torque is equal to200% full load torque.power factor too increases.

Applications

Washing machines,refrigrators,cooling fans,etc,besides this these motor can be used in all applications of split phase and capacitor start motors.