In single-phase induction motor, the main and auxiliary winding is in a circuit at the time of starting and to disconnect the auxiliary winding a centrifugal switch is provided when that specific motor attains a synchronous speed of 70 to 80%. Important Points Capacitor Start Motor: The single-phase induction motor is not self-starting. Hence, it requires an auxiliary means or equipment to start the motor. To start a single-phase induction motor, a capacitor is connected in series with auxiliary winding used to generate a phase difference between the torques which are generated by fluxes equal in magnitude but opposite in direction. The Starting capacitor is short time rated. It is of electrolytic type. A large amount of current is required to obtain the starting torque. Hence the value of the capacitive reactance should be low in the starting winding. The figure below shows the connection diagram of a capacitor start motor. [ alt="F2 U.B Madhu 31.12.19 D 1" src="//storage.googleapis.com/tb-img/production/19/12/F2_U.B_Madhu_31.12.19_D%201.png" style="width: 283px; height: 224px;"> The capacitor start motor has a cage rotor and has two windings on the stator. They are known as the main winding and the auxiliary or the starting winding. The two windings are placed 90 degrees apart. A capacitor CS is connected in series with the starting winding. A centrifugal switch SC is also connected to the circuit. The phasor diagram of the capacitor start motor is shown below: [ alt="F2 U.B Madhu 31.12.19 D 2" src="//storage.googleapis.com/tb-img/production/19/12/F2_U.B_Madhu_31.12.19_D%202.png" style="width: 181px; height: 186px;"> IM is the current in the main winding which is lagging the auxiliary current IA by 90 degrees as shown in the phasor diagram above. The auxiliary current IA leads the voltage. As the motor approaches its rated speed, the auxiliary winding and the starting capacitor are disconnected automatically by the centrifugal switch provided on the shaft of the motor. Since the torque developed by a single-phase motor is proportional to the sine of the angle between IA and IH, it is obvious that the increase in the angle (from 30º to 80º) alone increases the starting torque to nearly twice the value developed by a standard split-phase induction motor. Hence, this motor has high starting torque (3.5 to 4.5 times) among other single-phase Induction motors. The main and auxiliary winding is in a circuit at the time of starting and to disconnect the auxiliary winding a centrifugal switch is provided when that specific motor attains a synchronous speed of 70 to 80%.