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Internal accessories for circuit breakers

Jan 17, 2019

Auxiliary contact: the contact that is mechanically connected with the breaker's main circuit breaker, which is mainly used for the display of the breaker's on-off and on-off status. It is connected to the circuit breaker's control circuit to control or interlock its related electrical appliances through the on-off and on-off of the circuit breaker. For example, output signal to signal lamp, relay, etc. The rated current of the shell frame of the molded case circuit breaker is 100A, which is the single-breakpoint conversion contact; the bridge type contact structure is 225A and above, and the heating current is 3A. The rated current of shell frame grade 400A and above can hold two normally open and two normally closed, and the heating current is agreed to be 6A. The number of times of operation shall be the same as the total number of times of operation of the circuit breaker.

Alarm contacts, alarm contacts for circuit breaker accident, and the contact only when the circuit breaker points break off, is mainly used for load circuit breaker overload short circuit or under voltage and failures, and sometimes free trip, alarm contacts from the original into a normally open position close position, through to auxiliary line indicator or bell, buzzer, etc., in the display or remind the fault tripping circuit breaker status. Because the probability of circuit breaker free trip due to load failure is not too much, so the life of the alarm contact is 1/10 of the life of the circuit breaker. The operating current of the alarm contact generally does not exceed 1A.

Shunt trip: shunt trip is a trip excited by a voltage source and its voltage is independent of the main circuit voltage. Shunt tripping device is a kind of accessory for remote operation of shunt. When the supply voltage is equal to any voltage between 70% and 110% of the rated control supply voltage, the breaker can be reliably broken. Shunt trip is short-time working system, the coil power time is generally not more than 1S, otherwise the wire will be burned. Molded case circuit breaker to prevent coil burned, the shunt trip coils in series a micro switch, when the shunt tripping device through the armature and, micro switch from into a normally open normally closed state, as a result of the shunt tripping device power supply control circuit is cut off, even if people hold down the button, the shunt coil is never again electrify coil of this avoids damage situation. When the circuit breaker is closed again, the microswitch is in the normally closed position again.

Undervoltage tripping device, undervoltage tripping device is at its terminal voltage drop to a prescribed scope, make the circuit breaker with delay or without delay disconnect a trip, when the power supply voltage drop (or even slow down) to 70% and 35% of the rated voltage range, undervoltage tripping device should operate, undervoltage tripping device in power supply voltage is equal to 35% of the rated working voltage trip, undervoltage tripping device should be able to prevent the breaker closing; When the power supply voltage is equal to or greater than 85% of the rated operating voltage of the under-voltage tripping device, it should be able to ensure the reliable closure of the circuit breaker under the thermal condition. Therefore, when a certain voltage drop occurs in the power supply voltage of the protected circuit, the circuit breaker can be automatically disconnected to cut off the power supply, so as to protect the load appliances or electrical equipment below the circuit breaker from the damage of under-voltage. When in use, the under-voltage tripping device coil is connected to the power supply side of the circuit breaker. After the under-voltage tripping device is energized, the circuit breaker can be closed.