Function of main and auxiliary contacts of plastic case circuit breaker:

1. Auxiliary contacts play a role in transmitting the working state signals of circuit breakers. Provide interlocking contacts for control circuit, switch position of circuit breaker for signal circuit, and improve tripping contacts for protection circuit.

2. The auxiliary contact and the main contact act at the same time, which is the mechanical structure relationship. While the main contact is triggered, the internal mechanism drives the auxiliary contact to act synchronously. Auxiliary contact is usually an open and closed structure: when the main contact is closed, the auxiliary contact is always open and closed, and the normal closed contact is broken; when the main contact is broken, the open contact is always open and the normal closed contact is closed.

So, how to judge the contact quality of plastic case circuit breaker?

1. When choosing a circuit breaker, it is necessary to select the circuit breaker according to the current level. In general, the situation shown in the picture will not appear after the selection.

Molded case circuit breaker contact ignited, igniting the control groove above.

2. Check whether the contact is good or bad, or open to check more stable. Previously, a method was used to detect the temperature of each phase with a non-contact thermometer when the equipment was in normal operation. The position of each phase near the contact point was detected and the temperature values were compared.

3. Check if the product is not in good contact with the place where the temperature will rise and cause spontaneous combustion.

Note: The above inspection is based on the experience of many accidents, which may cause this phenomenon. But the actual situation is that the contact resistance varies greatly by the environmental impact, such as temperature, humidity and dust, which can affect the contact resistance. Therefore, it is impossible to measure whether the contact has been damaged by a standard resistance value.