There are several starting methods for 220V AC single-phase motors: The first type is a split phase starting type, as shown in Figure 1, which is assisted by an auxiliary starting winding and has a small starting torque. The operating speed remains roughly constant. Mainly used in electric fans, air conditioning fan motors, washing machines and other motors.
Second, the centrifugal switch is switched on when the motor is stationary, and the starting capacitor participates in the starting work after the power is given. When the rotor speed reaches 70% to 80% of the rated value, the centrifugal switch will automatically jump off, and the starting capacitor will complete the task and be disconnected. The starting winding does not participate in the operation, and the motor continues to operate with the running winding coil, as shown in Figure 2.
Third, the centrifugal switch is switched on when the motor is stationary, and the starting capacitor participates in the starting work after the power is given. When the rotor speed reaches 70% to 80% of the rated value, the centrifugal switch will automatically jump off, and the starting capacitor will complete the task and be disconnected. The running capacitor is connected to the starting winding in series to participate in the running work. This connection is generally used in air compressors, cutting machines, woodworking machine tools and other large load and unstable machines, as shown in Figure 3.
For a motor with a centrifugal switch, if the motor cannot be started successfully in a very short time, the winding coil will burn out quickly. Capacitance value: double-value capacitor motor, starting capacitance capacity is large, running capacitance capacity is small, the voltage is generally greater than 400V.
Forward and reverse control:
Figure 4 is the wiring diagram with a positive and negative switch. Usually, the resistance values of the starting winding and the running winding of the motor are the same, which means that the wire diameter and the number of coils of the starting winding and the running winding of the motor are completely consistent. This kind of motor is commonly used in washing machines. This positive and negative control method is simple and does not require complex transfer switches.
Figure 1, Figure 2, Figure 3, forward and reverse control, just swap 1-2 lines or 3-4 lines to complete the reversal.
For the judgment of starting and running windings in Figures 1, 2, and 3, the DC resistance of the starting winding is usually much higher than that of the running winding, which can be measured with a multimeter.The DC resistance of the general running winding is several ohms, and the DC resistance of the starting winding is ten ohms to dozens of ohms.
Single-phase capacitor motor connection
A single-phase motor has three terminals. First, use a multimeter to measure the resistance between the three terminals. The two terminals with the highest resistance are connected in parallel with a capacitor, and the other terminal (common end) is connected to one end of the power supply. Then use a multimeter to measure the resistance between the common end and the wire heads at both ends of the capacitor, the end with a slightly larger resistance value is connected to the other end of the power supply, and the absolute one-time connection is positive. If you want to change the direction, change the power cord connected to the capacitor end to the other end.
Why do single-phase motors have three wires? How to connect the starting capacitor and motor?
If the motor itself does not have a wiring diagram, the user can only use a multimeter to measure three sets of resistance numbers.
The two terminals with the maximum set of resistance values are the series connection of the starting and working windings, the middle value is the two terminals of the working winding, and the minimum set of resistance values is the two terminals of the starting winding. The working winding is connected in parallel with 220VAC, and the starting winding and capacitor are connected in series and then connected in parallel with the power supply.