Detailed explanation of the working principle of circuit breaker

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Introduction: In modern society, no matter which industry is inseparable from electricity. The use of electricity is inevitable and will cause some security risks. In order to ensure the safety of electricity in our daily life, we have the existence of a circuit breaker , and how does the circuit breaker play its protective role? This article will introduce you to the working principle of the circuit breaker ~~~

First, the working principle of the circuit breaker - - Introduction

A circuit breaker is actually a switch, but the state of the switch is not artificially controlled, but is controlled by a circuit. Under normal working conditions, the switch is in a closed state, and when a serious overload or short circuit or under voltage failure occurs in the circuit, the switch is automatically disconnected to protect the device and the line. Its function is equivalent to the combination of fuse switch and overheat thermal relay, and has been widely used.

After the circuit breaker judges the fault, it will perform the action as shown in the figure below to protect the power line and motor.

Second, the working principle of the circuit breaker - - classification

The circuit breaker is generally composed of a contact system, an arc extinguishing system, an operating mechanism, a trip unit, a casing, etc., and can be divided into two types: a universal circuit breaker and a plastic case circuit breaker. At present, the universal circuit breaker in China mainly produces DWI5. , DWI6, DWI7 (ME), DW45 and other series, plastic shell circuit breakers mainly produce DZ20, CMI, TM30 and other series.

Circuit breakers can be divided into high-voltage circuit breakers and low-voltage circuit breakers according to their range of use, but the high-low voltage boundary is relatively fuzzy. Generally, the voltage exceeding 3kV is called a high-voltage circuit breaker. The low voltage circuit breakers are widely used in our daily life.

Third, the working principle of the circuit breaker - low voltage circuit breaker

Low-voltage circuit breakers, also known as automatic air switches, can be used to control motors that are infrequently activated and are an important protection device in low-voltage distribution networks. The main contacts of the low voltage circuit breaker are either manually operated or electrically closed. After the main contact is closed, the free trip mechanism locks the main contact in the closed position. The coil of the overcurrent release and the thermal element of the thermal trip are connected in series with the main circuit, while the coil of the undervoltage release is connected in parallel with the power supply. When the circuit is short-circuited or severely overloaded, the armature of the overcurrent release pulls in, causing the free trip mechanism to act and the main contact to open the main circuit. When the circuit is overloaded, the heat element of the thermal tripper generates heat to deform the bimetal, and when it is deformed to a certain extent, the free trip mechanism is pushed to open and the switch is opened. When the circuit is under voltage, the armature release of the undervoltage release will also cause the free trip mechanism to act and open the switch.

Fourth, the working principle of the circuit breaker - - high voltage circuit breaker

Compared with the low-voltage circuit breaker, the arc-breaking arc is the core work to be completed because the arc to be disconnected can still burn without being extinguished after being elongated. The arc extinguishing is mainly to weaken the free arc while cooling the arc, strengthen the recombination and diffusion movement of the charged particles, and blow off the charged particles in the arc gap, so that the dielectric strength of the medium can be quickly restored. Protective effects.

Extended reading:

Circuit breaker working principle - basic type

The simplest circuit protection device is a fuse, that is, a very thin wire is attached to the circuit after being attached to the protective cover. This fuse can be blown after the temperature reaches a certain level, causing an open circuit. The circuit breaker is also a circuit protection device, but it can be used repeatedly, unlike a fuse, it can only be used once. The basic circuit breaker works as follows:

The current can magnetize the electromagnet, and the magnetic force generated by the electromagnet increases with the increase of the current. When the current increases to a dangerous level, the magnetic force generated by the electromagnet also increases accordingly, pulling the metal rod connected to the switch linkage to break the switch. Turn on, thereby interrupting the current and protecting the circuit. The bimetal strip also uses a similar principle to achieve protection of the circuit. At high currents, the metal strip is deformed, and when it is deformed to a certain extent, the linkage device is activated to open the switch. Some circuit breakers also rely on filling explosives to achieve control of the switch. When the current exceeds a certain point, the explosive material is ignited and the switch is opened.

Circuit breaker working principle - - Enhanced

Enhanced circuit breakers eliminate simple electrical equipment and use semiconductor equipment to monitor current levels. For example, the Ground Fault Circuit Interrupter (GFCI) not only protects the wiring of the house from damage, but also protects people from clicks. GFCI constantly monitors the current on the neutral and live lines in the circuit. When the two are the same, they are in normal working condition, and if the currents are different (if someone accidentally touches the live line, the current on the live line increases sharply, and If the current on the neutral line does not change, the circuit will be cut off immediately to prevent an accident. Since GFCI can take action without waiting for the current to rise to dangerous levels, its response speed is much faster than conventional circuit breakers.

After understanding the working principle of the circuit breaker, let us pay attention to other knowledge of the circuit breaker.

1. Basic knowledge of circuit breaker control loop

2, how to correctly choose small and medium circuit breakers

3. Uncover the secret of frequent tripping of circuit breakers

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