Low-voltage circuit breakers are also called automatic air switches or automatic air circuit breakers, referred to as circuit breakers. It is an electrical appliance that has both manual switching and automatic voltage loss, undervoltage, overload, and short circuit protection. It can be used to distribute electric energy, start asynchronous motors infrequently, protect power lines and motors, and automatically cut off circuits when they are severely overloaded or short-circuited or under-voltage faults. Their functions are equivalent to fuse switches and A combination of under-heat relays. Moreover, it is generally not necessary to change parts after breaking the fault current, and has been widely used. The low-voltage circuit breaker is composed of a contact, an arc extinguishing device, an operating mechanism and a protection device. 2.1 Contact System The contacts (static and moving contacts) are used in the circuit breaker to achieve circuit switching or breaking. The basic requirements for the contacts are: (1) It can safely and reliably turn on and off the limit short-circuit current and the following circuit current; (2) Working current of long-term working system; (3) Within the specified number of electrical life times, there will be no serious wear after switching on and off. The contact types of commonly used circuit breakers are butt-type contacts, bridge contacts and plug-in contacts. The butt-type and bridge contacts are mostly in surface contact or line contact, and silver-based alloy inserts are welded on the contacts. In addition to the main contacts, each large circuit breaker has sub-contacts and arc contacts. The action sequence of the circuit breaker contacts is that when the circuit breaker is closed, the arc contact is closed first, then the auxiliary contact is closed, and finally the main contact is closed; when the circuit breaker is broken, the main contact carries the load current, vice The function of the contact is to protect the main contact. The arc contact is used to bear the arc burning when the current is cut off. The arc is only formed on the arc contact, thereby ensuring that the main contact is not ablated by the arc and stable operation for a long time. 2.2 Arc extinguishing system The arc extinguishing system is used to extinguish the arc generated between the contacts when the circuit is broken. The arc extinguishing system consists of two parts: a strong spring mechanism to quickly separate the circuit breaker contacts; and an arc extinguishing chamber above the contacts. 2.3 Operating mechanism The circuit breaker operating mechanism includes two parts: a transmission mechanism and a trip mechanism. (1) Transmission mechanism: According to the different operation modes of the circuit breaker, it can be divided into: manual transmission, lever transmission, electromagnet transmission and motor transmission; according to the closed mode, it can be divided into: energy storage closure and non-storage closure. (2) Free tripping mechanism: The function of the free trip mechanism is to achieve a link between the transmission and the contact system. 2.4 Protection device The protection of the circuit breaker is realized by various trip units. The release type of the circuit breaker includes: undervoltage release, overcurrent release, shunt release, and the like. The overcurrent release can also be divided into an overload release and a short release. The undervoltage release is used to monitor the fluctuation of the working voltage. When the grid voltage is reduced to 70%~35% of the rated voltage or the grid is faulty, the circuit breaker can be immediately disconnected. When the power supply voltage is lower than 35% of the rated voltage, the circuit breaker can be prevented. The device is closed. The undervoltage release with time-delay action prevents voltage fluctuations caused by sudden load rise, which causes the circuit breaker to be improperly disconnected. The delay time can be 1s, 3s and 5s. The shunt release is used for remote remote control or thermal relay action breakers. An overcurrent release is used to prevent overload and load side short circuits. The general circuit breaker also has a short-circuit lock function, which is used to prevent the circuit breaker from being disconnected due to a short-circuit fault and before the fault is not eliminated. Under the short-circuit condition, the circuit breaker is disconnected, the locking mechanism is actuated, and the circuit breaker mechanism is maintained in the breaking position. Before the locking mechanism is reset, the circuit breaker closing mechanism cannot operate and the circuit cannot be connected. Low-voltage circuit breakers (formerly known as automatic switches, air switches) are switching devices that can not only switch on and off normal load currents and overload currents, but also turn on and off short-circuit currents. In addition to the control function, the low-voltage circuit breaker has certain protection functions, such as overload, short circuit, under voltage and leakage protection. Such as: 1) for infrequent on/off control of low voltage distribution circuits; 2) Automatically break the circuit when there is a fault such as short circuit, overload or under voltage in the circuit. Coaxial Car Speakers,15 Coaxial Speaker,15 Inch Coaxial Speaker,Coaxial Speakers Home Audio Guangzhou Yuehang Audio Technology Co., Ltd , https://www.yhspeakers.com
What are the functions of low-voltage circuit breakers? Classification and working principle of low-voltage circuit breakers
1. The concept of low voltage circuit breaker