Causes of the failure of the moulded case circuit breaker

First, high temperature causes circuit breaker trip
When the low-pressure plastic-case circuit breaker is installed in the outdoor distribution box, the summer temperature is higher, and the temperature in the box will rise after the load, exceeding the applicable working environment of the circuit breaker. The overload protection of the circuit breaker thermal bimetal element is made of two kinds of metal with different thermal expansion coefficients, when the bimetal feels the heat generated by the overload current, the active layer will bend to the passive layer, if the environment around the circuit breaker, the temperature, exceeds the reference temperature, even if the current is not loaded, the normal rated current is less than the rated current, The operation time of the circuit breaker will be advanced, and the overload protection function will be lost. Therefore, it is necessary to increase the rating of the circuit breaker, reduce the operating current and carry out on-site heat dissipation treatment.
Second, start the motor circuit breaker trip
1. Start the motor with load. When the motor starts with load, the current increases and the circuit breaker trips. Before starting the motor, check whether the motor load is cut off, and then start the motor when the motor is not loaded.
2, is low voltage, start the motor when the current surges, resulting in increased starting current resulting in circuit breaker trip. The range of voltage variation of the customer's electric terminal should not exceed, and the low-voltage power supply of the three-phase power supply customer is +7%- -7x of the rated voltage; When the measured voltage exceeds the specified value, measures such as adjusting the transformer tap and adjusting the load should be taken.
3. The instantaneous protection setting multiple of the circuit breaker is small. Reasonable adjustment of the instantaneous protection setting multiple of the circuit breaker is in line with the operation requirements of the field equipment. Fourth, the selected plastic-case circuit breaker is not a power type, causing the circuit breaker to trip. Select the correct MCCB according to the use of the equipment.
Third, the operation of the circuit breaker tripping phenomenon causes and measures.
1, is the selection of the connection cable or copper bar section is too small easy to heat, so that the circuit breaker trip.
2, is the load side of the tightening bolt to tighten resulting in poor contact and a lot of heat, so that the circuit breaker trip.
3, load overload tripping.
Four, low pressure plastic-case circuit breaker parts damage treatment.
1, is the main and secondary contacts. Serious surface burns should be replaced to avoid excessive grinding and reduce the pressure on the contact surface.
2. It is an auxiliary contact. Use fine sandpaper (cloth) for polishing; Contact surface should not be greasy.
3. It is an arc extinguishing cover. Charring phenomenon should be scraped; Damp phenomenon should be baked dry; Damaged should be re-matched; The installation Angle should be correct, so as not to interfere with the action of the contact.
4, is a short circuit ring and coil. The damaged ones should be replaced in time.
5. It is a soft connection piece. Damaged components should be replaced in time.