The power distribution cabinet is burned or ignited. I don’t know which one is. Is it the contactor that has been burned, or is it other components of the power distribution cabinet?

1. The selection of motor load cable or switch bridge line (parallel wiring of switch and switch) is too thin

When making the switchgear, the wire does not match the rated current of the actual load. For example, the rated current of a 22KW motor is about 44A, and your wire should be a 4mm² copper core cable. According to experience, the full load current of 4mm² copper wire is about 30A, which is much lower than the rated current of the motor. However, the probability of this situation is relatively low, and it is almost impossible for the original switchgear to appear.

2. The autotransformer or frequency sensitive resistor cabinet cannot be disconnected from the circuit for a long time

For these two kinds of step-down starting cabinets, after completing the starting task of the motor, the autotransformer or the frequency sensitive resistor must be removed from the circuit. Otherwise, the coil will be overheated and burned due to long-term electrified operation.

3. Overload operation, overload protection device fails and does not work

The setting current value of thermal relay or air switch with overload protection is adjusted too large, which makes the switch cabinet work under overload for a long time, resulting in excessive temperature and even fire.

4. Contactor contact singeing, poor contact

This is consistent with the description of the sub-topic. When the contactor contacts are singed, there will be uneven contact points on the surface, so that the contact area of the contacts is not enough, and the rated current carrying capacity of the contactor cannot be reached. When the motor starts, There will be a "fire" phenomenon, and over time, the contactor will be burned and cannot be used. In addition, the stroke of each contact of the contactor is inconsistent, and a serious "sparking" phenomenon will also occur.

Five, each terminal is loose and oxidized, resulting in poor contact

This situation is very likely, the main reason is that the terminal screws are loose or the wire lugs are not pressed tightly. Therefore, it is necessary to regularly check whether the screws are loose and whether the terminals are overheated.