What are the measurement methods of single-phase motor capacitance?

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

In a three-phase motor, the three-phase windings of the stator are distributed according to a certain law, 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 have come up with a way: first, divide the motor stator windings into two groups and distribute them according to a certain rule; second, use the current lag effect of the capacitor to divide the single-phase power supply into two paths, one of which lags the other. 90 degree electrical angle. Therefore, the single-phase motor runs two-phase current internally, but it is connected to one phase externally, which 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 required, 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 question.The capacitor of a single-phase motor is generally attached to the motor, and its capacity must be matched with the motor power.

There are signs on the capacitor shell, mainly the model CBB60, the nominal capacity is 10uF, the rated voltage is 400v, and the rated frequency is 50Hz.

If the single-phase motor can’t run, we have to suspect that the capacitor is broken. At this time, it is necessary to test the capacitance, which is the “test” that the subject said.

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

If there is no abnormality in appearance, then we must use electrical instruments to detect, a multimeter is enough.It is recommended to use a pointer table

We use the X1K power barrier to detect the quality of the capacitor: the test lead is connected to the two leads of the capacitor. After the good capacitor is connected, the gauge needle will quickly deflect to 0 and then gradually increase, stabilize at a large resistance value, and then connect the The test leads and leads are swapped, and it is a deflection process that returns to 0 and then increases. At this time, it can be judged that the capacitor is good. You can further measure the capacity deviation with the capacity value file. If the pointer points to 0, the capacitor is shorted; if the pointer points to ∞, the capacitor is open.

The CD60 model is a starting capacitor. Take off the capacitor. There are two red and black wires. The ends of the two wires must be exposed. Use both hands to clamp the red wire with one hand and the black wire with the other hand. 220v AC socket, then quickly pull it out, and touch the head of the black wire with the end of the red wire. If there is a small spark with a “pop” sound, it means that the capacitor is good, otherwise, if there is no response, the capacitor is broken.

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