There is no obvious scratch and damage in appearance. It's easy to move without blocking. When the power supply is connected, the closing is smooth. The contact has no air oxidation. When the resistance of the electromagnetic coil exceeds 5 megohm, there is no penetration and flicker in the detection of high voltage DC1000V.

1. Look at the level: to see if it is working, start up such as AC contactor, when the centrifugal fan is working, the press is not working (set capacitor is good), can basically judge the AC contactor is bad. Since the compressor and the external centrifugal fan are all operated according to the normally open contact of the AC contactor, the contacts work in the same step. If one of them is working, the other one is not working, it can be roughly judged as touch damage.

2. Listening level: listen to whether there is a very loud creaking sound. If there is, it may be low power supply voltage, dirty on the contact point or dirty on the surface of transformer core. If you hear the cackle noise that the AC contactor can't absorb, it is common that the power supply voltage is low or the contact force is insufficient.

3. Smell level: smell of wood and paste, if so, please check the winding resistance and contact.

4. Accurate measurement level: turn off the power supply, take out the wire at the control end of the contact, use the digital multimeter to measure, press and hold the three main contacts and another group of normally open contacts at the edge of the experiment, they should be on and off, and the normally closed contacts should not be on and off. Learn to put down the edge of the experiment, the main contact and normally open contact should not conduct, the general closed contact should conduct. The winding resistance of the electromagnetic coil is about 200 Ω. Before accurate measurement, the wire at one end should be removed before accurate measurement.

5.Short circuit level: when the machine is started and the AC contactor is closed, if the press does not turn, the AC contactor can be twisted open with pointed nose pliers, and the left and right contacts of the same group can be short circuited with two pointed mouths respectively. In this way, when the press is working, it is confirmed that the contact is broken. It must be noted that this method has certain risk factors, and the actual operation should ensure safety.