Common Air Switches and Residual Current Circuit Breakers in Households

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1. **Air Switches (Circuit Breakers)**

- **Working Principle**: - Air switches are mainly used for overload and short-circuit protection. When the current in the circuit exceeds the rated current of the air switch, a relatively strong magnetic field will be generated, causing the release to operate and thus cut off the circuit. For example, for an air switch with a rated current of 16A, if the current in the circuit exceeds 16A for a long time (such as when multiple high-power electrical appliances are used simultaneously), the overload protection will be triggered. In the case of a short circuit, the instant extremely large current will make the release operate more quickly to cut off the circuit rapidly and protect the wiring and electrical equipment.

- **Types and Specifications**: - According to the number of poles, there are single-pole, double-pole, and three-pole ones, etc. Single-pole air switches are generally used to control the live wire in a single-phase circuit, such as household lighting circuits. Double-pole air switches can control both the live wire and the neutral wire simultaneously and are often used for the incoming power line of the household or for 220V electrical appliance circuits with relatively large power, like electric water heaters. Three-pole air switches are used for three-phase circuits.

- Common rated current specifications include 6A, 10A, 16A, 20A, 25A, 32A, etc. For household lighting circuits, 10A or 16A air switches are generally selected; for socket circuits, they can be selected according to the purpose of the socket and the power of the connected electrical appliances. For example, 16A can be selected for ordinary socket circuits, and 20A or 25A may be required for sockets of high-power electrical appliances such as air conditioners.

- **Brands and Quality**: - Well-known brands include Schneider, Siemens, Chint, and Delixi, etc. The air switches of these brands are guaranteed in quality, and the quality of components such as their internal contact materials and tripping mechanisms is relatively high. For example, Schneider's air switches adopt high-quality arc extinguishing devices, which can effectively reduce the generation of arcs when cutting off the current, extend the service life, and their tripping characteristics are relatively accurate, enabling them to operate in a timely manner under appropriate current overload and short-circuit conditions.

2. **Residual Current Circuit Breakers**

- **Working Principle**: - Residual current circuit breakers are mainly used to detect leakage current in the circuit. Under normal circumstances, the currents of the live wire and the neutral wire in the circuit are equal, and the vector sum of the incoming and outgoing currents is zero. When leakage occurs, for example, when electrical equipment leaks electricity or a person gets an electric shock, a part of the current will leak through the grounding path, resulting in the vector sum of the currents of the live wire and the neutral wire not being zero. The zero-sequence current transformer in the residual current circuit breaker will detect this unbalanced current. When this unbalanced current exceeds the operating current of the residual current circuit breaker (the general operating current is 30mA), it will make the release operate and quickly cut off the circuit, thus protecting personal safety.

- **Types and Specifications**:

- According to the operation mode, there are electromagnetic type and electronic type. The electromagnetic type residual current circuit breaker has stable performance, strong anti-interference ability, is not affected by voltage fluctuations, and has a fast operation speed, but its price is relatively high. The electronic type residual current circuit breaker has high sensitivity and a small size, but it is greatly affected by environmental factors and the performance of electronic components. - Specifications mainly include operating current and operating time. Common operating currents are 30mA (high sensitivity), 100mA (medium sensitivity), 300mA (low sensitivity), etc. In households, 30mA high-sensitivity residual current circuit breakers are generally used, and the operating time is generally within 0.1 seconds, which can quickly cut off the power supply and avoid serious injuries caused by electric shock accidents.

- **Brands and Quality**: - Similarly, international brands such as Schneider and Siemens and domestic brands such as Chint and Delixi have good quality. The residual current circuit breakers of these brands perform excellently in terms of the accuracy and reliability of leakage detection. For example, Chint's residual current circuit breaker adopts a high-precision zero-sequence current transformer, which can accurately detect tiny leakage currents, and the quality of its electronic components is reliable, enabling it to maintain stable performance during long-term use. In household circuits, residual current circuit breakers are usually installed in the distribution box in combination with air switches to form a complete protection system.