The difference between starting capacitor and running capacitor of single-phase motor

The starting capacitor is to make the starting coil of the single-phase motor energized when starting, and cut off after starting. The running capacitor is to make the motor perform capacitance compensation during operation, so the starting capacitor cannot be less, and the running capacitor can be used.No matter what kind of capacitor it is, it has a starting effect at the beginning of single-phase motor starting. But when the motor reaches about 75% of the rated speed, the starting capacitor is automatically disconnected by the centrifugal switch, while the running capacitor continues to work with the motor.

The process of starting a single-phase motor is actually the process of "column phase". Because single-phase motors are different from three-phase motors, there is no phase difference and no rotating magnetic field can be generated.The role of the capacitor is to make the starting winding current of the motor 90 electrical angles ahead of the running winding in time and space, forming a phase difference.Among them, the running capacitor also plays a role in balancing the current between the primary and secondary windings. Since the starting capacitor works for an instant and short time, the withstand voltage is required to be above 250V, while the running capacitor needs to work for a long time, and the withstand voltage is required to be above 400V.For general-purpose motors, its capacitance is adjustable, generally only a few UF. For asynchronous motors, capacitors are running, mostly below 20UF. Of course, there are also big ones, which mainly depends on the size of the motor power.Some motors have "smoke" during operation. It is estimated that the current of the motor is too large, and the windings are overheated so that they are short-circuited and burned. Most of them are not the problem of capacitors. It is rare to see smoke from the short-circuit breakdown of the capacitor, but sometimes you can smell a special odor.