How does a capacitor-start motor achieve higher starting torque?
1 Answer
A capacitor-start motor is a type of single-phase induction motor that is designed to provide higher starting torque compared to a standard single-phase motor. It achieves this higher starting torque by using an auxiliary winding and a capacitor during the starting phase of the motor's operation.
Here's how it works:
Main Winding: The motor has two windings - the main winding and the auxiliary winding. The main winding is connected directly to the power supply and is responsible for producing the main magnetic field that drives the motor's rotation.
Auxiliary Winding and Capacitor: The auxiliary winding is also connected to the power supply, but it is designed with more turns of thinner wire, which results in a higher inductive reactance. This winding is also displaced from the main winding by a certain electrical angle.
Additionally, a capacitor is connected in series with the auxiliary winding. The capacitor creates a phase shift between the current flowing through the main winding and the current flowing through the auxiliary winding. This phase shift creates a rotating magnetic field that interacts with the main magnetic field, resulting in an initial torque boost.
Starting Phase: When the motor is first turned on, both the main winding and the auxiliary winding receive voltage from the power supply. However, due to the phase shift caused by the capacitor, the currents in the main and auxiliary windings are not perfectly aligned. This phase difference creates a rotating magnetic field that enhances the starting torque of the motor.
Running Phase: Once the motor reaches a certain speed, a centrifugal switch is triggered. This switch disconnects the auxiliary winding and the capacitor from the circuit. The motor continues to operate using only the main winding, which is more efficient for running conditions. The auxiliary winding and capacitor are not needed at this point, and they are essentially switched out of the circuit.
In summary, the combination of the auxiliary winding and the capacitor creates a higher starting torque by generating a rotating magnetic field that interacts with the main magnetic field. This increased torque helps the motor overcome the initial inertia and start rotating more easily, making it suitable for applications where higher starting torque is required, such as in certain types of pumps, compressors, and fans.
Here's how it works:
Main Winding: The motor has two windings - the main winding and the auxiliary winding. The main winding is connected directly to the power supply and is responsible for producing the main magnetic field that drives the motor's rotation.
Auxiliary Winding and Capacitor: The auxiliary winding is also connected to the power supply, but it is designed with more turns of thinner wire, which results in a higher inductive reactance. This winding is also displaced from the main winding by a certain electrical angle.
Additionally, a capacitor is connected in series with the auxiliary winding. The capacitor creates a phase shift between the current flowing through the main winding and the current flowing through the auxiliary winding. This phase shift creates a rotating magnetic field that interacts with the main magnetic field, resulting in an initial torque boost.
Starting Phase: When the motor is first turned on, both the main winding and the auxiliary winding receive voltage from the power supply. However, due to the phase shift caused by the capacitor, the currents in the main and auxiliary windings are not perfectly aligned. This phase difference creates a rotating magnetic field that enhances the starting torque of the motor.
Running Phase: Once the motor reaches a certain speed, a centrifugal switch is triggered. This switch disconnects the auxiliary winding and the capacitor from the circuit. The motor continues to operate using only the main winding, which is more efficient for running conditions. The auxiliary winding and capacitor are not needed at this point, and they are essentially switched out of the circuit.
In summary, the combination of the auxiliary winding and the capacitor creates a higher starting torque by generating a rotating magnetic field that interacts with the main magnetic field. This increased torque helps the motor overcome the initial inertia and start rotating more easily, making it suitable for applications where higher starting torque is required, such as in certain types of pumps, compressors, and fans.