Single-phase motor starting method

1. How to start

The starting methods of 220 V AC single-phase motors are roughly divided into the following types:

The first type, split-phase starting type, as shown in Figure 1, is assisted by the auxiliary starting winding. The starting torque is not large. The operating speed remains roughly constant. Mainly used in electric fans, air conditioner fan motors, washing machines and other motors.

The second is that the centrifugal switch is turned on when the motor is stationary. After the power is supplied, the starting capacitor participates in the starting work. When the rotor speed reaches 70%~80% of the rated value, the centrifugal switch will automatically trip, and the starting capacitor will complete the task, and is disconnected. The starting winding does not participate in the running work, and the motor continues to operate with the running winding coil, as shown in Figure 2.

The third type is that the centrifugal switch is turned on when the motor is stationary. After the power is supplied, the starting capacitor participates in the starting work. When the rotor speed reaches 70%~80% of the rated value, the centrifugal switch will automatically trip, and the starting capacitor will complete the task, and is disconnected. The running capacitor is connected in series with the starting winding to participate in the running work. This connection method is generally used in places where the load is large and unstable, such as air compressors, cutting machines, and woodworking machine tools. As shown in Figure 3.

For motors with centrifugal switches, if the electricity cannot be started successfully in a short time, the winding coils will burn out quickly.

Capacitance value: The dual-value capacitor motor has a large starting capacitance and a small running capacitance, and the withstand voltage is generally greater than 400 V.

2. Forward and reverse control:

Wiring diagram with forward and reverse switch, usually the starting winding and running winding of this kind of motor have the same resistance value, that is to say, the starting winding and running winding of the motor have the same wire diameter and number of coils. This type of motor is generally used in washing machines. This forward and reverse control method is simple and does not require a complicated switch.

For forward and reverse control, you only need to swap 1~2 lines or 3~4 lines to complete the reversal.

For the judgment of starting and running windings, the DC resistance of the starting winding is usually much larger than that of the running winding, which can be measured with a multimeter. Generally, the DC resistance of the running winding is several ohms, while the DC resistance of the starting winding is ten ohms to several tens of ohms.