Some household appliances used in our daily life, such as air conditioners, refrigerators, washing machines, electric fans,etc., are widely used in single-phase asynchronous motors, which use start-up capacitors.
Single phase means that there is only one 220V live wire and one neutral wire. Ordinary household appliances are single-phase power supply.
For single-phase motors, there is one running winding (main winding) and one starting winding (secondary winding). Sometimes, the fan in the house has not been opened or opened for a long time. Just turn the blade with chopsticks and the fan will turn. When the hand is released, the fan can still turn automatically. Here, by hand, it is equivalent to the role of the starter group, which is connected in series with a starting capacitor. The motor rotates automatically because there is also a running winding in the motor.
For the start of a single-phase motor, this capacitor is also called the starting capacitor. From the circuit principle, it plays a role in phase shifting. Because a single-phase motor has only one set of running windings, single-phase power cannot produce a rotating magnetic field and requires another set of starting windings to match. A capacitor is connected in series with the start winding. The characteristic of the capacitor is that the voltage cannot be abrupt, so the current of the starting coil is advanced by 90° from the running coil. This creates a rotating magnetic field in the stator space, and the rotor cuts the magnetic lines of force to generate an induced current to form an induced magnetic field. The two magnetic fields of the stator and the rotor interact, and the magnetic field induced by the rotor acts on the magnetic field of the stator, causing the magnetic field of the rotor to follow the stator. The direction of the rotor of the motor coincides with the direction of the rotating magnetic field. In this way, the rotor can be rotated continuously, allowing the motor to start normally.
Some single-phase motors are one capacitor, and some are two capacitors. Only one capacitor is called the starting capacitor.There are two capacitors, one is the starting capacitor and the other is the running capacitor. Generally, the capacity of the starting capacitor is greater than the capacity of the running capacitor.
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