The leakage circuit breaker plays a vital protective role in the operation of CNC busbar processing machines. It shall be operated strictly in accordance with working principles and specifications. However, refusal to trip and false tripping may occur during service. The main causes are summarized as follows.

Causes of False Tripping

Reversed connection of PE wire and neutral wire leads to false tripping. In three-phase four-wire circuits shared by lighting and power loads, improper adoption of three-pole leakage circuit breakers with load neutral wire connected to the power supply side of the protector triggers misoperation.

Electromagnetic interference generated by nearby high-power electrical equipment during startup and shutdown also causes false tripping. Three-phase power cables failing to pass through the zero-sequence current transformer in a uniform direction will incur tripping faults. Excessively high sensitivity setting of the circuit breaker is another inducement.

Low insulation resistance between live wire and neutral wire results in partial current leakage to the ground. The vector sum of currents passing through the transformer cannot return to zero under normal working state and leads to false action. Connection between the equipment shell PE wire and working neutral wire will also cause tripping errors.

Daily Motor Maintenance

Keep the motor clean all the time. Dust, water stains and foreign matters entering the motor interior may damage wire insulation, cause inter-turn short circuit, raise current and temperature, and eventually burn out the motor. Prevent impurities from infiltrating inside. Regularly clean the motor exterior and heat dissipation fins to guarantee favorable heat dissipation performance.

Dust inside the electric cabinet shall be removed regularly by air blowing or wiping. Tighten fixing bolts and wiring terminals constantly to avoid poor contact, misoperation and equipment breakdown. Arrange cables with proper bending radian to prevent wire fracture.