Circuit breaker is used in the specified time to close, load and break the abnormal circuit current switching device, by manual operation or electric closing, divided single, two pole, three pole, four pole. Main contact, auxiliary contact, alarm contact, shunt trip, undervoltage trip and other main structure, the following small series for you to introduce the relevant content in detail.
First, the circuit breaker working principle
1, the main contact of the low-voltage circuit breaker is manually operated or electric closing. After the main contact is closed, the free trip mechanism locks the main contact in the closing position.
2. The coil of the over-current trip and the thermal component of the thermal trip are in series with the main circuit, and the coil of the under-voltage trip is in parallel with the power supply. When the circuit is short circuit or serious overload, the armature of the overcurrent trip is pulled to make the free trip mechanism action, and the main contact is disconnected from the main circuit. When the circuit is overloaded, the thermal element of the thermal trip will heat up and bend the bimetal plate, pushing the free trip mechanism into action.
3. When the circuit is undervoltage, the armature of the undervoltage trip is released, which also makes the free trip mechanism act. Shunt tripping device is used as remote control, in normal work, the coil is power off, in need of distance control, press the start button, make the coil energized.
Two, the main structure of the circuit breaker
1, the main contact
Through the load current for a long time, it is connected after closing, and disconnected first when opening. The main contact is present on all switches.
2, auxiliary contact
The contact connected mechanically with the splitting and closing mechanism of the main circuit breaker is mainly used for the display of the splitting and closing state of the circuit breaker. It is connected in the control circuit of the circuit breaker through the splitting and closing of the circuit breaker to control or interlock the related electrical appliances.
3. Alarm contact
Used for circuit breaker accident alarm contacts, 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, etc., in the display or remind the fault tripping circuit breaker status.
4. Shunt tripping device
Shunt trip is a trip excited by a voltage source whose voltage is independent of the main circuit voltage. Shunt tripping device is an accessory for remote operation. Breaker can be reliably broken when the supply voltage is equal to any voltage between 70% and 110% of the rated control supply voltage. Shunt trip is a short-time working system, the coil power time generally cannot exceed 1S, otherwise the wire will be burned.
5. Undervoltage trip
Under voltage trip 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 trip shall prevent circuit breaker closure; When the power supply voltage is equal to or greater than 85% of the rated operating voltage of the undervoltage trip, the circuit breaker must be closed reliably in the hot state.