Why is a dual capacitor often utilized in some single-phase motors?

A dual capacitor is effectively employed in some single-phase motors primarily to manage both the starting and running phases optimally. In these motors, one capacitor is designated for starting—providing the necessary phase shift to create a rotating magnetic field that allows the motor to start. Once the motor reaches a certain speed, the starting capacitor is typically disconnected.

The second capacitor, used for running, remains connected to improve the operating efficiency of the motor once it is running. It enhances the power factor and improves the overall performance during operation. By utilizing two capacitors in this way, the system is able to achieve better torque and efficiency throughout the various phases of operation, which is vital for applications requiring reliable performance.

The other options do not capture the primary purpose of dual capacitors as effectively. For example, while reducing power consumption and enhancing speed under load are beneficial aspects, they are more of a result of the optimal management of starting and running phases rather than the direct purpose of incorporating a dual capacitor system. Similarly, providing emergency power is not a function of the dual capacitor configuration in single-phase motors.