Коментарі читачів

The main working principle of circuit breaker

як Nick Lee Swift (2023-06-27)

In electrical and electronic systems and equipment, circuit breaker is also a common and important device, which can not only turn on or break the normal load current, but also cut off many kinds of faults such as overcurrent, undervoltage, overheating and leakage current of load and line, so it has many protection functions. In addition, the circuit breaker has the advantages of adjustable action value, strong breaking ability, convenient operation, reuse, safety and so on, so it is widely used.

Since the birth of the circuit breaker in 1885, its structure and forms are varied due to different applications, such as manual operation, manual operation, selective protection, selective protection, high voltage application, low voltage application and so on, and the circuit breaker is making continuous progress with the development of the times. At the end of the 20th century, electronic and intelligent circuit breakers have come out one after another, and have been widely used in high voltage, low voltage power generation, transmission, distribution, power consumption and other fields. In the field of low-voltage applications, circuit breakers are often called automatic switches.

The specific structure of circuit breaker is various, but its basic structure and working principle are similar. Taking a simple low-voltage single-phase circuit breaker as an example, the main structure and working principle of the circuit breaker are introduced. The circuit breaker is mainly composed of contact system, operating mechanism, various tripping devices, arc extinguishing device, shell and so on. Among them, the contact system is mainly used to turn on and break the circuit, which is usually composed of moving contacts, static contacts and connecting wires, and the operating mechanism is an actuator used to realize the closing and disconnection of circuit breaker contacts, which generally adopts the four-link principle and can be driven manually, electrically or hydro-pneumatic. The tripping device is the sensing and signal transmission part of the circuit breaker, which detects information such as current, voltage, temperature or external instructions. when the above signal reaches a certain amplitude, the contact of the circuit breaker can be broken and tripped by the transmission element. When the contact disconnects the current, the arc phenomenon will appear between the static and dynamic contacts because of the strong electric field. In order to extinguish the arc as soon as possible, an arc extinguishing device is set up near the circuit breaker contact, which is similar to a high-power fuse.

The main working principle of the circuit breaker is as follows: the two groups of contacts of the circuit breaker are connected in series in the line, the overcurrent tripping link and overheating tripping link are connected in series with the line, and the undervoltage tripping link and sub-excitation tripping link are connected in parallel with the line. When the contact of the circuit breaker is closed through the operating mechanism, the two groups of contacts hook the right hook by the lock key, which overcomes the pulling force of the left spring and keeps the contact closed. When the current detection link detects that the current is too large or the temperature detection link detects overheating, it will trigger the release lever and make the lock key open, so that the spring pull contact can be separated and the disconnection action can be realized. Similarly, if the undervoltage link detects that the grid voltage is too low or the sub-excitation link is triggered by external control signals, it will also trigger the tripping lever and form a circuit breaker to cut off the line.

When the load is working normally, the current and voltage flowing through the circuit breaker are also normal. At this time, the amplitude of the current and the thermal effect produced by the current are small, and the undervoltage detection link does not act, that is, it will not make the respective release move, so the release lever does not act, and the contact is always in a closed position to turn on the circuit.