Principle and function of centrifugal switch

Working principle

For single-phase motors, it is installed on the rotor of the motor, and the circuit is connected in series in the starting loop. The switch is switched on when the rotor is stationary and disconnected when it reaches a certain speed. When starting, the starting circuit starts through the conduction of the Centrifugal Switch. When reaching a certain speed, the centrifugal switch breaks off and automatically cuts off the starting circuit. After starting, the motor becomes running state.

The first is the non-centrifugal switch, single-capacitor phase shifter, such as electric fans, which are usually used in small motors.

The first is the non-centrifugal switch, single-capacitor phase shifter, such as electric fans, which are usually used in small motors

Second, there is a centrifugal switch, single capacitance phase shift start, such as some fans and other equipment, but for a variety of reasons, this kind of motor seems to be less and less. But in some special places, it does exist.

The third type, that is, there is a centrifugal switch, double capacitance double value phase shift type, in many places the most common, such as air compressor, cutting machine, table drill and other places.

The difference between several capacitive motors

The first kind, because of this design, the starting button moment is not large, so it is not suitable for high load equipment, especially the start of the air compressor, which needs a large button moment, this is not competent.

The second type is mainly designed in the past, with higher start-up performance than the former, but it is only suitable for stable operation after start-up, because its auxiliary winding is used as start-up, and after start-up, it completely depends on the rotating magnetic field of the main winding. There is no so-called phase commutation, because the capacitor and auxiliary winding are separated by centrifugal switch after the motor speed reaches a speed. They have not worked, the fatal shortcoming of this motor is, once with some high load equipment, such as air compressor, often turn around to slow down, and then start again through the auxiliary winding, so it is not suitable for many places, usually only used in the fan and other places to have some use, but has been the third kind of motor.

The principle of the third type is that it has both primary and secondary windings and centrifugal switches. The secondary windings and primary windings work together, which is similar to the one mentioned in the first type. However, how to deal with the deterioration of startup performance? They pass the centrifugal switch, which is a kind of double-throw switch, so that when starting, string a large capacity capacitor [commonly known as starting capacitor] (we also know that the larger the capacitance, the larger the phase shift current, the better the starting performance, but too large winding will heat up) So, this kind of motor, is at a low speed, the use of large capacitance, The current provided by this large capacitor usually exceeds the rated current of the winding. Under such high current drive, the rotating magnetic field is very strong, thus driving the output of the high button moment of the rotor to rotate.