A Capacitor Start Induction Run (CSIR) motor is a type of single-phase induction motor that is designed to provide high starting torque while running with relatively lower current requirements. It is commonly used in applications where high starting torque is needed, such as in certain types of pumps, compressors, and air conditioners.
The CSIR motor consists of two main windings:
Main (Running) Winding: This winding is designed for continuous operation and is responsible for running the motor under normal operating conditions.
Auxiliary (Starting) Winding: This winding is used only during the motor's starting phase. It is connected in series with a capacitor to create a phase shift between the two windings. This phase shift generates a rotating magnetic field, which provides the motor with the necessary starting torque.
The working principle of a CSIR motor is as follows:
Starting Phase: When the motor is initially switched on, both the main and auxiliary windings receive electrical power. The capacitor helps to create the necessary phase shift between the two windings, resulting in a rotating magnetic field. This rotation provides the high starting torque required to overcome the inertia of the motor and the connected load.
Running Phase: Once the motor reaches a certain speed (typically around 75-80% of its rated speed), a centrifugal switch disconnects the auxiliary winding and capacitor from the circuit. The motor continues to run using only the main winding, which is designed for continuous operation.
The advantage of using a CSIR motor is its ability to provide high starting torque while being relatively simple and cost-effective compared to other types of starting mechanisms. However, one drawback is that the motor's efficiency may not be as high as other starting methods, such as the Capacitor Start Capacitor Run (CSCR) motor or the Permanent Split Capacitor (PSC) motor. Additionally, CSIR motors may not be suitable for applications requiring frequent starts and stops, as the starting phase introduces more stress on the motor's components.