Shulou(Shulou.com)11/24 Report--

The safety of electricity can not be ignored. When selecting electrical appliances or equipment, safety is the primary consideration. When the power supply fluctuates or the overcurrent is too large, it will lead to overload or short circuit resulting in equipment damage. Therefore, it is necessary to install a device as a safety component to provide protection for electrical devices or circuits.

Fuse is one of the most commonly used circuit protection devices in the early days, the shape of the fuse is metal wire or metal strip, when the current is too large or short circuit, the fuse will be melted, playing the role of interrupting the current protection equipment.

Today, simple fuses have been replaced by a variety of smarter circuit breakers, and air switches are commonly used as circuit protection devices.

What is an air switch when the circuit in the home is short-circuited or the current is too high, if a suitable circuit breaker is not installed, these devices will be burned and cause a fire accident, and the air circuit breaker can protect washing machines, ovens, refrigerators and other appliances in the home.

Air switch, also known as air circuit breaker, belongs to a small tripping switch that provides overcurrent protection. it is a kind of circuit breaker, as long as the current in the circuit exceeds the rated number, it will be opened automatically. Air switch is a very important device in low voltage distribution system, which is mainly used to protect electrical appliances in residential, commercial and industrial electrical systems.

It has a variety of control and protection functions. It can not only contact and break the circuit, but also protect the circuit or electrical equipment from short circuit, serious overload and undervoltage. At the same time, it can also be used to start the circuit infrequently.

The characteristic of the air switch is that the air switch is an automatic switch, which is automatically disconnected when excessive current flows through the circuit, and can be reconnected after the circuit is normal, without the need to replace accessories, and once it is fused, it must be replaced or rewired, which is the main reason why the air switch is used as a fuse substitute in most circuits. in addition, whenever the circuit fails, the air switch will be turned off automatically. This can easily detect the failure of the equipment.

And the air switch is relatively safe, it is an electromagnetic switch made of insulating materials, which can quickly restore power supply without more maintenance costs, and the short-circuit response speed of the air switch is very fast. It will trip and cut off the power in less than three milliseconds.

The working principle of the air switch the whole air switch is mainly composed of contact device, arc extinguishing device, tripping mechanism, transmission device and protection device, in which the arc extinguishing device is composed of insulated grille, which is used to separate and extinguish the arc produced. The tripping mechanism is composed of two sets, one is a bimetal release, the other is an electromagnetic release.

When working normally, the current enters the air switch, passes through the solenoid, then passes through the bimetal sheet, and finally flows out of the whole air switch, because the heat generated is limited, it will not exceed the upper limit set by the tripping parts. so it doesn't trigger any internal devices.

When a serious overload current occurs on the line, a large amount of heat will be generated. When it exceeds the upper limit set by the metal sheet, it will deform and bend upward, push the lever and lock off, cut off the power supply, and play the role of overload protection.

When the circuit is short-circuited, the current in the air switch will instantly increase by dozens of times, and the magnetic field in the electromagnetic coil will also increase, and the electromagnetic release will produce enough suction to absorb the connecting rod and impact the lever to detach the hook from the lock and cut off the power supply.

And the moment of disconnection will produce an arc, so will this arc have an impact? how can it disappear? the reason why it is called an air switch is that it has something to do with this arc.

Why is it called an air switch that produces a dangerous arc when the circuit is connected and disconnected? it will not only damage the contact point, but also prolong the time of disconnecting the circuit, so people use various methods to eliminate the arc. Air switch uses air as arc extinguishing medium, so it is called air switch.

In the process of power off, these two kinds of tripping mechanisms will also produce an arc, which needs to be extinguished quickly. when the arc is generated, it will enter into the partition composed of many insulating materials, and first realize the segmentation of the arc. When the arc continues to advance along the partition, it will become weaker and weaker, and finally completely extinguished in the arc extinguishing device.

It means to lengthen the arc inside and let it cool naturally in the air until it goes out, so it has something to do with the air.

The difference between the air switch and the leakage switch in fact, many people will confuse the air switch with the leakage switch, the leakage protector is commonly known as the leakage switch, its function is to protect the dangerous person by electric shock when the leakage occurs in the circuit equipment. in addition to protecting personal safety, the leakage switch also has the function of short-circuit protection, which can protect the short-circuit problem of wires.

Generally speaking, the air switch can be used as the main switch, and then connected to each leakage switch from it, each leakage switch is divided as a circuit, the air switch has the function of over-current protection and short-circuit protection, and can realize automatic tripping, and the air switch also has leakage type, but the leakage switch can not replace the air switch.

The most intuitive understanding is that in function, although the two look similar, the air switch is mainly to protect electrical overload, which is equivalent to the function of a fuse, and the leakage switch is mainly to prevent electric shock. If a short circuit occurs, both of them have a protective function. Now there is also an air switch with leakage protection function, which is tantamount to merging into one.

In addition, it is also easy to distinguish from the appearance, there is an obvious button on the leakage switch, which says press once a month.

Why press it? the main purpose is to check whether the leakage protector is faulty and whether it can be used normally. In case there is a failure and an electric shock occurs, it is very dangerous.

I guess there are not many people who really press it, including me. From today on, it is necessary to press it once a month. We must remember it.

Reference: Wikipedia, Bing

Gif is intercepted from Youtube "MCBs, how do they work?--Lesics" and "How Does a Miniature Circuit Breaker (MCB) work?--Explorer".

This article is from the official account of Wechat: manufacturing principle (ID:zhizaoyuanli), author: Lao Zheng

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