But in case of single phase motors, the field produced by the stator is not rotating (but alternating only) and hence single phase motors are not self starting.But, if the rotor is rotated by any other means (by hand or any tool), the induced currents in the rotor will assist with stator currents to produce revolving field.Single phase induction motors are extensively used in low power applications such as domestic appliances as mentioned above.
This winding is excited with a single phase AC supply.The auxiliary or starting winding is made highly resistive whereas the main or running winding is made highly inductive.Due to the large phase difference between these two, the torque produced by the rotor is high enough to start it.These rotor bars are permanently shorted at both ends with the help of end rings as shown in figure.There is no physical connection between the stator and rotor, but there is a small and uniform gap between them.
Shaded pole single phase induction motor ppt
Based on the starting method, single phase induction motors are basically classified into the following types.The rotating magnetic field is produced when there are minimum two alternating fluxes, having a phase difference between them.This field causes the motor to run in the direction it is started even with a single winding. However, it is not possible to give initial rotation every time externally if the motors are attached to loads.As mentioned above that, due to the rotating magnetic field of the stator, the induction motor becomes self starting.
There are many methods of making a single phase induction motor as self starting one.The construction of these motors is more or less similar to a three-phase squirrel-cage induction motor.The stator is a stationary part and it has laminated construction, which is made up of stampings.Once the motor reaches 75 percent of its speed, the auxiliary winding may be disconnected by a centrifugal switch and the motor able to run on a single main winding.Single phase induction motors are used primarily for domestic and light-industrial applications where three-phase supply is generally not available.