The world's first circuit breaker was invented in 1885, a combination of a knife switch and an overcurrent trip unit. In 1905, the air circuit breaker with a free-trip mechanism was invented. Since 1930, with technological advancements, the discovery of the electric arc principle, and the invention of various arc-extinguishing devices, mechanical circuit breakers gradually took shape. In the late 1950s, the rise of electronic components led to the development of electronic trip units. Today, the widespread use of microcontrollers has given rise to intelligent circuit breakers.
Common types include low-voltage circuit breakers and vacuum circuit breakers: Low-voltage circuit breakers are electrical appliances used in circuits with AC voltages of 1200V and DC voltages of 1500V for functions such as switching, control, or protection. Low-voltage circuit breakers are an important component of the electrical industry and a basic component in the machinery industry. In power distribution systems, low-voltage switchgear is mainly composed of various low-voltage circuit breaker components. The function and performance of low-voltage circuit breakers play a crucial role in low-voltage switchgear. Over 80% of the electrical energy generated by power generation equipment is distributed through low-voltage circuit breakers. For every additional 10,000 kW of power generation equipment, approximately 20,000 low-voltage circuit breakers of various types are required. Industrial automation systems also require various control panels, consoles, and controllers made of low-voltage circuit breakers. Since 1949, China's low-voltage circuit breaker industry has gradually developed from simple electrical repair and assembly factories into an industry capable of independent design and production. By 1979, there were over 600 manufacturing enterprises. After two development peaks in 1985-1986 and 1990-1991, the industry had grown to approximately 1,500 manufacturing enterprises by 1995.
China's low-voltage circuit breaker manufacturing enterprises are mainly concentrated in Beijing, Tianjin, Liaoning, Shanghai, Jiangsu, Zhejiang, and Guangdong. While promoting national economic development, this has also exposed many problems. The main problems are as follows:
1. The enterprises are too small in scale and too numerous. Among China's low-voltage circuit breaker manufacturers, only 2-4 are large enterprises with annual sales revenue and total assets exceeding 500 million yuan. The vast majority are small and medium-sized enterprises (SMEs), resulting in a lack of economies of scale and competitiveness. Furthermore, the number of low-voltage circuit breaker manufacturers in China has grown from the early days of the People's Republic to over 1,500 today. This excessive number of enterprises leads to fragmented economic resources, a lack of overall innovation momentum, and consequently, low production efficiency, economic benefits, and market competitiveness.
2. Regional structural convergence and severe duplication of construction. Due to the blind expansion and over-investment in projects, China's low-voltage electrical appliance industry suffers from severe regional industrial convergence, low-level duplication of construction, resulting in overproduction, low energy and raw material utilization, low economic efficiency, and consequences such as regional protectionism and vicious competition.
Advances in vacuum circuit breaker technology are manifested in increased capacity, lower overvoltage, intelligent operation, and miniaturization. This progress is a result of the development of vacuum technology, arc-extinguishing chamber technology, and the adoption of new processes, materials, and operating techniques. According to the inventors, this technology, in addition to serving as a replacement for traditional motor technology, will also expand the development and application space for DC motors. Developing large-capacity DC motors to replace AC synchronous generators and converter station equipment powered by high-voltage DC transmission networks can not only save a lot of construction costs for converter stations, but also significantly reduce substation losses.
