Leakage protection switch plays a very important role in life. It is mainly used as a grounding protection device to prevent electric shock and leakage caused by personal injury. When the leakage current of circuit or electricity equipment is greater than the setting value of the device, or humans and animals occur. When it is in danger of electric shock, it can act quickly and cut off the power of the accident to prevent the accident from expanding and protect the safety of people and equipment. The following small series introduces the selection of leakage protection switch and leakage protection switch product characteristics.
First, the choice of leakage protection switch
1, according to the purpose of use to choose
(1) Direct contact protection is to prevent electric shock accidents caused by direct contact with the human body and live conductors of electrical equipment. When the human body and live conductors are in direct contact, before the action of the leakage protection device cuts off the power, the human body's electric shock current and leakage protection The selection of the operating current of the device is irrelevant. It is entirely determined by the voltage of the human body and the body resistance. The leakage protection device cannot limit the electric current through the human body. Therefore, the leakage protection device for direct contact protection must have a fast action of less than 0.1S. Performance, or inverse time characteristics as specified by the IEC leakage protection device standards.
(2) Indirect contact protection is to prevent dangerous electrical contact voltages on exposed metal parts such as metal enclosures when electrical insulation is damaged. The selection of the operating current IΔn of the leakage protection switch shall be considered in conjunction with the grounding resistance R of the electrical equipment and the permissible contact voltage U. The contact voltage U on the electrical equipment shall be less than the specified value. Leakage protector operating current IΔn selection: IΔn ≤ U / R where: U - allow contact voltage R - contact resistance of the device is generally for fixed voltage rated 220V or 380V fixed electrical equipment, such as pumps Other electric devices that are easily in contact with the human body, such as mills, can be used with a leakage protection device that can operate within 30s to 50 mA when the metal device housing has a grounding resistance of 500 Ω or less; When the grounding resistance is less than 100Ω, a 200-500mA leakage protection device can be selected. For the more important power-consuming equipment, in order to reduce the momentary power failure, a time-delay protection device with an operating current of 0.2s can also be used. Electrical equipment for household use often has plugs that are frequently plugged in and out, and at the same time, some residential houses do not consider grounding protection facilities. When electrical equipment is used to cause insulation faults such as leakage or shell leakage, the equipment enclosure may present a dangerous voltage that is the same as the operating voltage, and is prone to electrical shock and death. Therefore, the electrical equipment installation regulations stipulate that the electrical energy meter must be on the household entrance line. Later, install a high-sensitivity leakage protection switch with an operating current of 30mA and 0.1S.
2, according to the use of places to choose the general low-voltage circuit in the 380/220V, if the metal casing and other metal parts of the equipment is easily touched by people, at the same time these electrical equipment can not be in accordance with the requirements of China's electricity regulations to make it ground resistance When it is less than 4Ω or 10Ω, it is advisable to install the leakage protection device in the power supply circuit of the electrical equipment according to the requirement of indirect contact protection. At the same time, it is also necessary to reasonably select the leakage switch of different operating current according to different use places. For example, in a wet workplace, because the human body is more likely to sweat or wet, the skin's insulation performance is reduced and the human body resistance is significantly reduced. When an electric shock accident occurs, the current through the human body must be greater than that of a dry place. High, therefore, suitable to install 15 ~ 30mA, and can operate within the 0.1S leakage protection device.
Second, leakage protection switch product features
As a special way of existence, the biggest characteristic of the leakage protection switch is the judgment and detection function. The leakage protection switch may be the same as the circuit breaker, and the main circuit may be disconnected or connected. For the electric leakage in the circuit, there is a detection and judgment. If there is a leakage in the main circuit, the leakage protection switch will start its own detection function, and the switching elements in the circuit will be disconnected and connected. In addition, the leakage protection switch can be used together with the thermal relay and the fuse, and the structural functionality will be improved. At present, this type of device is widely used.
Third, the difference between leakage protection switch and air switch
Leakage protection switch
1, leakage protection switch is the role of the fire line, if people contact the fire line, then through the human body and the earth constitute a loop, there is no additional current through the zero line, the inside of the electromagnetic device will automatically trigger, it will trip, immediately power off protection of the human body;
2. When an air switch has a leakage protection function, it is called a leakage protection switch. The principle of determining whether or not there is leakage is based on the fact that the current flowing into and out of the switch must be equal, otherwise it is determined as leakage. When the leakage current reaches or exceeds a certain degree, a protective action - tripping occurs;
3. If it is used for personal safety protection purposes, the leakage current is less than 30mA, and it is regarded as safe. If it is greater than 30mA, it is regarded as unsafe and will produce protection actions. Leakage protection The rated current of 30mA leakage protector or protection switch belongs to the same-sensitivity leakage protector or protection switch. Its production protection action time should also be within 0.1 seconds.
air switch
1, the air switch is the neutral line and FireWire, when the current between the two lines is too large will automatically trip, the role and the same fuse;
2. The air switch is used to prevent the circuit from being short-circuited or overloaded. As long as the line is short-circuited or overloaded, it will trip, leakage will not trip;
3. The air switch is a switch that controls the electrical circuit. If air is used as an extinguishing medium, it is called an air switch. It is generally selected with the rated current (load) and used as the main switch of the electrical circuit.
Editor's summary: The selection of the leakage protection switch and the characteristics of the leakage protection switch product are introduced here, and we hope to help everyone. If you want to know more related information, you can pay attention to this website information.
Leakage protection switch
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