Current situation and development trend of the hot

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The current situation and development trend of China's industrial electrical appliances. With the rapid development of national economy and national defense modernization, more and more requirements are put forward for electrical appliances. At present, the structure and working principle of electrical appliances are constantly improved and innovated, and the increasing variety and specification is one of its characteristics. So what is an electrical appliance? All electrified appliances can be collectively referred to as electrical appliances

in terms of voltage level, the maximum working voltage has developed to above 765kV level, and the prototype of 1500kV EHV electrical equipment has also been developed, with the minimum voltage below several volts

in terms of current level, electrical equipment or components with a maximum operating current of more than tens of thousands of amps and a minimum operating current of milliampere or less

in terms of power frequency, the well-known DC and 50Hz or 60Hz power frequency AC power supplies are still widely used. In addition, electrical components and devices powered by low frequency, ultra-low frequency, medium frequency, high frequency, ultra-high frequency and pulse power supply are also widely developed and applied

at present, the structural size of electrical equipment or components has grown from half a match to a giant equipment several floors high. It is of practical significance to reasonably organize the production and use of electrical appliances, scientifically and reasonably divide the voltage and current levels, and minimize the specifications and models of series products. It is very important to develop "combined", "building block" and "standard unit" as far as possible, as well as electrical appliances or components with universal parts and high interchangeability. Especially in the current process of economic reform, it is very important to strengthen macro leadership and actively carry out scientific and technological academic exchanges. In this way, various disciplines can be mobilized to cooperate with each other and learn from each other

2. The development of high voltage apparatus is closely related to the development of transmission and distribution circuits. At present, 2 ~ 3million kW power stations have appeared, and 10 ~ 12million kW large capacity power stations are the inevitable trend of development, such as the Three Gorges water conservancy project on the Yangtze River and the southwest water conservancy project. However, small and medium-sized power stations in small rivers are also being built everywhere. In order to transmit electric energy economically, it is one of the important methods to increase the working voltage of the transmission circuit. Therefore, there will be a series of technical problems waiting for electrical science workers to study and solve. For example: 1) the limit operating voltage and current of various electrical appliances, that is, to study the limit economy and possible output capacity; 2) It is very meaningful to study the cause and harm of overvoltage, so as to adopt corresponding measures to limit, reduce or eliminate overvoltage. For example, the copper consumption and insulation weight of 500kV transformer are almost the same. Therefore, it is of practical significance to study the measures to reduce the overvoltage to reduce the insulation withstand voltage level. At present, the existing methods can limit the switching over-voltage within the range of 1.5 ~ 2.0 times, 3) research on internal insulation free discharge, anti-aging and dirt, and Research on the discharge characteristics of long gap air external insulation; 4) Research on new principle and new medium of arc extinction. For example, vacuum switch, sulfur hexafluoride, and the traditional method of increasing the compressed air pressure to 150 atmospheres; 5) Research on new principle and new structure. For example, capacitive voltage transformer, photoelectric current transformer (magneto-optical effect type, optical pulse repetition frequency modulation type, etc.)

in addition, the successful development of high voltage and high current thyristors has provided conditions for the development of DC transmission circuits. Therefore, the requirements of switch and electrical equipment for switching DC transmission circuit are put forward. At present, China has adopted 22kv or above DC power supply system on electrified railway lines, and there are 500kV experimental lines in Shanghai, Xi'an and other places. Generally speaking, it has changed from experimental type to operational type in China. At present, many scientists have made new progress in theory and technology. There are about 1000kV ultra-high DC transmission circuits in operation abroad. This system has great economic value for over distance transmission

the research on the flexibility and reliability of the operating mechanism of high and low voltage switchgear is also a very interesting topic. The automatic reclosing device which automatically disconnects the short-circuit fault and then automatically closes is also a subject of great practical value and economic benefits. The leakage prevention and maintenance of sulfur hexafluoride, compressed air and vacuum switch are also important issues to be solved urgently. The oil circuit breaker is still in use

3. Low voltage apparatus

low voltage apparatus is the main electrical equipment for low-voltage power supply and consumption. In most cases, it is installed in the control panel (or cabinet) and used as a complete set of electrical appliances. In some cases, electrical appliances (or components) are also used alone. Low voltage switch is one of the main products in the field of low voltage electrical appliances. At present, the key technical problem is to improve the service life and reliability. This point has been paid attention to at home and abroad, including dryness and wetness. It involves electromagnetic structure and theory, mechanism theory, technology and material process, as well as impact vibration resistance and abrasion resistance at 23 ± 2 ℃ of moving parts (such as springs, short-circuit rings, contacts, etc.). For example, it is one of the effective methods to improve the service life of AC electromagnetic switch by making the short circuit ring embedded

at present, new automatic switches have been adopted in civil buildings to replace the traditional knife switch fuse combination scheme, especially in buildings where overload or short-circuit faults often occur. Although the one-time investment is slightly higher, it can not only improve the power supply quality, but also save a lot of fuses. At the same time, the recovery after failure can be *. Therefore, the development and application of low-voltage apparatus is very important

The emergence of new components such as semiconductors and thyristors makes them combined with electromagnetic devices to make automatic equipment with various functions. They will be widely used in the fields of national economy, national defense and life. For example, the static devices of intermediate frequency power supply for various purposes instead of rotating motors (devices with hundreds of watts to tens of thousands of kilowatts have been made), magnetic semiconductor appliances, semiconductor switches, magnetic semiconductor regulation and stabilization devices, wet air in the atmosphere will penetrate into the box, etc. In order to comprehensively solve the above technical problems, it is often necessary to develop "composite", "building block" or standardized electrical equipment such as unitization and parts generalization. This is a new trend that needs or has been vigorously researched and developed at present

household appliances are another new technical field in low-voltage electrical appliances. In order to have strong competitiveness in the market and enter the foreign market, it is necessary to meet the technical indicators in terms of aesthetics, applicability, no noise, safety, power saving, excellent function, convenient maintenance and use of the profit strain curve of the materials or packages, so as to be welcomed by thousands of households

due to the successful development of large and medium scale integrated circuits, microcomputers and electronic appliances have been widely used in many aspects. This has a great impact on the miniaturization of electrical appliances, instruments and meters. Therefore, many samples of weak current electrical appliances, micro electrical appliances, instruments and meters have been developed

however, at present, there are more articles on basic theories of electrical appliances and electromagnets in domestic and foreign magazines. The application of magnetic amplifier has been improved, especially in the requirements of primary and secondary electrical isolation and high-precision measurement and control. Air gap permeance of electromagnet G δ= f( δ) And the exact calculation method of derivative dg8/ds, arc extinguishing theory and calculation method have not been completely solved. At present, the approximate calculation is still based on * empirical data or formula. Finally, it is still solved according to the * test

4. Electrical materials

electrical materials mainly include insulating materials, conductive materials, magnetic materials and semiconductor materials

insulation materials have been developed in the synthesis of new materials such as high temperature resistance, voltage resistance, infrared radiation and ultra-low temperature. Therefore, enameled wire with high temperature resistance up to 200 ℃ has been widely used, and enameled wire with high temperature resistance of 250 ℃ has also been developed. The research work of substituting aluminum for copper has been applied in some electrical equipment

at present, there are many new varieties of magnetic materials. High quality low coercivity alloy steel sheets can be rolled into 0.1mm thick permanent magnetic materials with high coercivity, such as br=12000gs, HC = 3000oe, and Br = 6000gs, HC = 6000oe magnetic ceramics have also been developed. In addition, thermal magnetic core, magnetic bubble, filter element made of magnetic single crystal, etc. High magnetic conductivity, high resistance and high strength magnetic materials are also under development and research

with the continuous improvement of the manufacturing process of semiconductor materials, special semiconductor devices such as transistors, thyristors, turn-off thyristors, bidirectional thyristors, thermal sensors, magnetic sensors, gas sensors, force sensors and photosensitive devices have been developed. Medium and large scale integrated circuits can skillfully realize various control logic functions, making it easier to realize the automation of production process

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