How to measure whether the single-phase motor capacitor is good or bad

In the three-phase motor, the three-phase windings of the stator are distributed according to certain rules, and the three-phase power frequency current is passed through, and the rotating magnetic field is generated by the alternating current.

However, the power supply of a single-phase motor is single-phase. If no measures are taken, only a pulsating magnetic field can be generated in its stator, and electromagnetic torque cannot be generated, nor can it work.

Smart people came up with a way: first, divide the motor stator winding into two groups and distribute them according to certain rules; second, use the current hysteresis effect of the capacitor to divide the single-phase power supply into two circuits, one of which lags the other by 90 degrees electrical angle. Therefore, the internal operation of the single-phase motor is a two-phase current, but it is connected to one phase externally, and it is still called single-phase. The principle is as follows:

In this way, the use of single-phase can also make the motor run, because only single-phase electricity is needed, soymilk machines, washing machines, electric fans, refrigerator compressors, etc. all use single-phase motors, and small agricultural machinery also widely uses single-phase motors .

Alright, back to the main topic. The capacitor of a single-phase motor is generally attached to the motor, and its capacity should match the power of the motor.

There is a mark on the capacitor shell, mainly including model CBB60, nominal capacity 10uF, rated voltage 400v, rated frequency 50Hz, etc.

If the single-phase motor cannot run, we have to suspect that the capacitor is broken. At this time, it is necessary to test the capacitance, which is the "test" mentioned by the subject.

Capacitors are generally short-circuited or open-circuited. We can look with our eyes first. If the appearance of the capacitor is bulging and deformed, it can generally be concluded that the capacitor has been damaged.

If there is no abnormality in the appearance, we must use electrical instruments to detect it at this time, and a multimeter is enough. It is recommended to use an pointer watch.

We use the X1K accompanying electric barrier to detect whether the capacitor is good or bad: the test lead is connected to the two leads of the capacitor. After the good capacitor is connected, the watch needle will quickly deflect to 0 and then gradually increase, and stabilize at a larger resistance value. Swapping the test pen and the lead wire is another deflection process of returning to 0 and then increasing. At this time, it can be judged that the capacitor is good.You can further use the capacitance file to measure the deviation of capacity. If the pointer points to 0, the capacitor is short-circuited; if the pointer points to ∞, the capacitor is open-circuited.

The CD60 model is a starting capacitor. Take the capacitor down. There are two red and black wires. The ends of the two wires must be exposed. With two hands, one hand clamps the red wire and the other hand clamps the black wire.Insert the two ends of the two wires into the 220v AC socket with both hands at the same time, then pull them out quickly, touch the end of the black wire with the end of the red wire,if there is a small spark when you touch it, it means that the capacitor is good. On the contrary, if there is no response, it means that the capacitor is broken.