The difference between starting capacitor and running capacitor

As we all know, the single-phase ac motor is not like the three-phase motor. It can rotate when it is powered. It needs a starting torque to rotate, and the forward and reverse timing of this torque determines the direction of the motor. There are many ways to start. Among them, capacitor starting is one kind, which is customarily called starting capacitor, and single-phase motors need it to turn smoothly.

However, some single-phase motors not only have one capacitor, but some motors have two capacitors. Why is this? Because some motors are equipped with a starting capacitor and a running capacitor, what's the matter?

Running capacitor: It is to connect the alternating current to the auxiliary winding after shifting the phase to form an alternating magnetic field, and form an approximately circular elliptical rotating magnetic field with the alternating magnetic field of the main winding. So it can be the same capacitor, but its role is different.

No matter what kind of capacitor it is, it has a starting effect at the beginning of the 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 the 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 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 a 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 450V.

The starting capacitor is to energize the starting coil of the single motor 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 used.

The running capacitor is the starting capacitor used when the compressor is working normally, and it is used together with the running capacitor to start the compressor when the compressor is started. After the compressor turns up, the starting capacitor is disconnected.The running and starting capacitors are combined together, but one of the starting capacitors has been turned on, and the starting capacitor is useless when the motor turns. What is the difference between starting capacitor and running capacitor? That is, the starting capacitor has a large capacity, which is generally 2-5 times that of the running capacitor, while the running capacitor has a small capacity. The capacity difference between the two is very large, and it is easy to distinguish.