Low-voltage circuit breaker, formerly known as air circuit breaker. It is mainly used to automatically break the circuit and cut off the power supply when the circuit is overloaded, short-circuited, and under-voltage.
The common fault of low-voltage circuit breakers is that they cannot be closed. The reasons for this kind of failure are that the undervoltage release has no voltage or the coil is damaged, the reaction force spring is too large, or the mechanism cannot be reset and then buckled. The repair method is to insist on changing the power supply voltage, replacing the coil or re-adjusting the spring. In the case that the mechanism cannot be reset and then buckled, it is also a common fault that the temperature rise of the circuit breaker is too high due to the adjustment of the buckle contact surface to the specified value. The reason is that the contact pressure is excessively reduced. At this time, the contact pressure can be adjusted or the spring can be replaced. This fault may sometimes be caused by severe abrasion of the contact surface or severe poor contact. At this time, a new circuit breaker should be replaced. If the temperature rise is too high, it is because the connecting screws of the two conductive parts are loose, so they should be tightened again.
When the current occurs to reach the set value and the circuit breaker cannot be normally broken, check whether the bimetallic strip of the thermal trip unit is damaged, and if it is damaged, it should be replaced. Then check whether the distance between the armature and the iron core of the electromagnetic release is too large or whether the coil is damaged, and then adjust the distance between the armature and the iron core or replace the circuit breaker. Sometimes the circuit breaker is opened immediately when the motor is started. This may be because the instantaneous setting value of the overcurrent release is too small, or due to vibration in operation, etc., the instantaneous setting value of the overcurrent release is adjusted to The specified value. If some parts are damaged, the trip unit can be replaced.
When the loss-of-voltage release of the low-voltage circuit breaker makes noise, observe whether there are rust spots or oil stains on the surface of the iron core. If there is, wipe it off. Or observe whether the short-circuit ring is broken. If it is broken, replace the armature and iron core. Now you can see if the reaction force is too big, if it is too big, you should readjust it.
