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Is the starting capacitance of a single-phase motor the same as the running capacitance?

author:xiaoE date:2020-01-01 13: 07
Is the starting capacitance of a single-phase motor the same as the running capacitance?
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 allow the motor to perform capacitance compensation during operation, so the starting capacitor cannot be less, and the running capacitor can be omitted.
No matter what kind of capacitor, it has a starting function at the beginning of the 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, and the running capacitor continues to work with the motor.
 The process of starting a single-phase motor is actually the process of "phase out".Because single-phase motors are different from three-phase motors, there is no phase difference and no rotating magnetic field can be generated.The function of the capacitor is to make the starting winding current of the motor lead the running winding 90 electrical angles 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 must be above 250V, while the running capacitor must work for a long time, and the withstand voltage must be above 400V.
For general-purpose motors, its capacitor is speed-regulated, generally only a few UF.For asynchronous motors, the capacitor is running, mostly below 20UF.Of course, there are also large 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 the short circuit burns out. Most of them are not the problem of capacitors.The short-circuit breakdown of the capacitor seldom sees smoke, but sometimes a special odor can be smelled.
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