Circuit breaker is used in the specified time to close, load and open the abnormal circuit current switch device, by manual operation or electric closing, single, two poles, three poles, four poles. There are main contact, auxiliary contact, alarm contact, shunt release, undervoltage release and other main structures, the following small series for you to introduce the relevant content in detail.
First, the working principle of circuit breaker
1, the main contact of the low-voltage circuit breaker is manually operated or electrically closed. After the main contact is closed, the free tripping mechanism locks the main contact on the closing position.
2. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply. When the circuit is short-circuited or seriously overloaded, the armature of overcurrent tripping device is closed to make the free tripping mechanism move and the main contact disconnects the main circuit. When the circuit is overloaded, the thermal element of the thermal release device heats up and bends the bimetallic sheet, which pushes the free release mechanism to act.
3. When the circuit is under voltage, the armature of the undervoltage trip mechanism is released, which also makes the free trip mechanism move. Shunt trip is used for remote control. In normal operation, the coil is powered off. When distance control is required, press the start button to make the coil energized.
Two, the main structure of the circuit breaker
1. Main contact
Through the load current for a long time, switch on after closing, switch off first. The master contact is common to all switches.
2. Auxiliary contact
The contact connected with the main circuit of the breaker is mainly used for the display of the breaker's opening and closing state. It is connected to the control circuit of the breaker through the opening and closing of the breaker to control or interlock the relevant 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 trip
Shunt trip is a trip excited by a voltage source, its voltage is independent of the main circuit voltage. Shunt tripper is an accessory for remotely operating brake. When the supply voltage is equal to any voltage between 70% and 110% of the rated control supply voltage, the circuit breaker can be reliably disconnected. Shunt trip is a short-time operation, the coil power time generally should not exceed 1S, otherwise the line will be burned.
5. Undervoltage release device
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 release shall prevent circuit breaker from closing; When the power supply voltage is equal to or greater than 85% of the rated operating voltage of the undervoltage tripper, the circuit breaker shall be closed reliably under hot conditions.