Which single-phase motor is most commonly used to drive a refrigerator compressor?

The choice of a capacitor-start, capacitor-run motor for driving a refrigerator compressor is primarily due to its efficiency and performance characteristics. This type of motor is designed with two capacitors: one for starting and another for running, which provides a high starting torque. This is particularly important for a refrigerator compressor, as it requires considerable torque to start under load, especially when the compressor is cycling on and off due to temperature regulation.

Additionally, the capacitor-run aspect allows the motor to maintain a smooth operation while running, which is essential for efficient performance and energy consumption. The capacitor ensures that the current is phase-shifted properly to maximize torque and minimize vibrations, which contributes to a quieter operation—a desirable feature in household appliances.

In contrast, options like the shaded-pole motor typically have lower starting torque and are more commonly found in low-torque applications, while the permanent split capacitor motor, although efficient, does not have the same level of starting torque necessary for compressors. The split-phase motor also lacks the efficiency and torque characteristics needed for a refrigerator compressor, making the capacitor-start, capacitor-run motor the optimal choice for this application.