Capacitor start and capacitor run motors are both types of single-phase induction motors that are designed to provide improved starting performance and efficiency compared to standard single-phase motors. They achieve this through the use of capacitors in their circuits, which help to create a phase shift in the motor's winding currents.
Capacitor Start Motor:
A capacitor start motor has a main winding and an auxiliary winding, along with a start capacitor. The main winding is designed for high torque production, but it's not ideal for starting due to its relatively high impedance. The auxiliary winding is wound with more turns and has lower impedance, making it better suited for starting.
During starting, the start capacitor is connected in series with the auxiliary winding. This creates a phase shift between the currents in the main and auxiliary windings. The phase shift helps create a rotating magnetic field that initiates rotation of the motor. Once the motor gains sufficient speed, a centrifugal switch disconnects the start capacitor, and the motor continues to run on the main winding alone.
The advantages of a capacitor start motor include:
High starting torque: The phase shift provided by the capacitor helps generate higher starting torque, making it suitable for applications where a high starting load needs to be overcome.
Improved efficiency: By using the higher impedance main winding only during running, the motor can operate more efficiently.
Capacitor Run Motor:
A capacitor run motor also has a main winding and an auxiliary winding, but in this case, both windings remain active during operation. The motor has a run capacitor connected in series with the auxiliary winding.
The run capacitor provides a continuous phase shift between the currents in the main and auxiliary windings. This phase shift improves the power factor and efficiency of the motor by reducing the reactive power consumption. It also helps to balance the magnetic field, resulting in smoother motor operation and reduced vibration.
The advantages of a capacitor run motor include:
Improved power factor: The continuous phase shift provided by the capacitor helps to correct the power factor, reducing the reactive power and improving the overall efficiency of the motor.
Balanced operation: The balanced magnetic field created by the run capacitor reduces motor vibration and noise, leading to smoother operation.
In summary, both capacitor start and capacitor run motors use capacitors to create phase shifts that enhance the starting performance and efficiency of single-phase induction motors. The specific advantages and applications of each type depend on the requirements of the motor's intended use.