Low voltage electrical appliances are used for AC voltage to 1200V, DC voltage to 1500V circuit to play the role of on-off control or protection of electrical appliances, is an important part of the electrical industry. As thermoplastic engineering plastics, modified engineering plastics are widely used in low-voltage electrical components in China. This paper analyzes the application of modified engineering plastics in the products of plastic shell circuit breaker, AC contactor, terminal and connector in low voltage electrical apparatus.
1, domestic low-voltage electrical industry development status and trend
Our country low voltage electrical appliance industry since 1949, on the basis of some repair, assembly simple electrical appliance factory gradually developed into independent design, production industry. After MANY YEARS of development, INDUSTRY OF LOW VOLTAGE ELECTRICAL APPLIANCE OF OUR COUNTRY HAS formed a relatively complete system, FORMED THE situation of state-owned, private and foreign capital enterprise "three legs". Come a few years, industry of our country low voltage electrical appliance increased technology research and development intensity, transfer to industry high-end gradually. However, domestic low-voltage electrical enterprises have the following problems in terms of economic scale: first, the scale of enterprise organizations is small and the number is too large and scattered. Lack of competitive strength and advantage. Secondly, the regional structure is convergent, which cannot reflect comparative advantages and collaborative benefits. Moreover, the technical structure is not reasonable, the main industrial technical equipment level.
With the globalization of the market, the mutual penetration of foreign enterprises and domestic enterprises is another inevitable trend in the development of low-voltage electrical appliance industry. Such penetration includes the penetration of high-end products of domestic enterprises into foreign markets; The products of foreign enterprises will penetrate the domestic medium and low market.
At the same time, the future development of low-voltage electrical products will present the following development trends:
1. Intelligent low-voltage electrical products.
In modern power stations and industrial and mining enterprises, the computer monitoring system has been widely used, and the requirements of high performance and intelligence for the low-voltage circuit breaker matching with it are put forward, and the products are required to have the functions of protection, monitoring, testing, self-diagnosis, display and so on.
2. Electronic products.
In modern enterprises, the use of PC control system instead of the system composed of electrical and mechanical components has become the mainstream of mechanical and electrical control system. The system requires electrical products with high reliability, high anti-interference, but also requires that the contacts can be reliably connected with voltage, weak current, contact disconnection arc can not interfere with the normal operation of the electronic circuit.
3. Product combination and modularization.
It is the development direction of current voltage appliance industry to combine modules of different functions into modular combination appliances according to different needs. The contacter body is equipped with auxiliary contact components, delay components, self-locking components, interface components, mechanical interlocking components and surge voltage components, etc., which can adapt to the requirements of different occasions, so as to expand the scope of product application, simplify the production process, and facilitate user installation, use and maintenance. At the same time, it will further improve product reliability and product quality.
2. Application of modified engineering plastic materials in domestic low-voltage electrical appliance industry
2.1 Application of modified engineering plastic materials in circuit breaker products
The circuit breaker is one of the products with the largest output in low-voltage electrical appliances, in which the plastic shell circuit breaker can automatically cut off the current after the current exceeds the jump setting, and play a protective role in the circuit. The enclosure of the circuit breaker is molded by injection molding of modified engineering plastics into the enclosure of the insulator device, and the enclosure is also used to isolate the conductors and the grounding metal part. In the selection of high and medium grade plastic shell circuit breaker shell modified engineering plastic insulation materials, foreign DSM company halogen free phosphorus flame retardant or flame retardant reinforced PA6 engineering plastics series products have long been in a monopoly position. According to the range of rated operating current (Ics) and rated operating current (In) of circuit breakers in different applications, the corresponding grades of materials are recommended as shown in Table 1 below:
DSM company for the low-voltage electrical circuit breaker material selection provided by the mature recommended program can be seen: The introduction of modified PA6 engineering plastics or modified high temperature resistant 龙(PA46), have different characteristics, such as small proportion, high fluidity, high leakage resistance index (CTI=600V), flame retardant UL-94V0, halogen and red phosphorus free, stable flame retardant performance and heat resistance characteristics. Among them, the latest halogen-free PA46StanylCR310(NC181) products used for circuit breaker housing with breaking current above 25KA are 30% glass fiber reinforced, flame retardant V0, halogen free and red phosphorus free completely halogen-free (non-low halogen) stable flame retardant performance, mechanical and flow performance is very significant.
For a long time, due to the barriers of supply chain control and product certification in this application field, the modified engineering plastics used in the circuit breaker shell products of domestic halogen-free foreign and joint ventures or large private enterprises with a certain scale have been exclusively monopolized by DSM's series products. Until the second half of 2011, foreign enterprises such as BASF and Landic gradually launched corresponding brand products to participate in the competition in the domestic market, such as BASF brand B3UG4 similar to K222-KGV4 and B3UM4 similar to K222-KMV5. Entering 2012, with the rise of domestic labor costs, as well as the impact of domestic property market regulation on the building technology market, high-end voltage electrical products gradually saturated, foreign capital, joint ventures and large private enterprises in order to reduce enterprise costs, only gradually opened the domestic work of circuit breaker housing materials, in this context, Gradually, domestic modified plastics enterprises such as Bensong (Zhejiang) Engineering Plastics Co., LTD., Zhejiang Juner and Beijing Chemical Industry Research Institute and other enterprises, under the strong support of downstream customers, increase product research and development efforts, and gradually introduce corresponding brand products to break the long-term monopoly of foreign products.
2.2 Application of modified engineering plastic materials in AC contactor products
In electrical engineering, contacters are often used in motor control because they can quickly cut off the main circuit of AC and DC and can be frequently connected to the device of the large current control circuit, and can also be used to control the power load of factory equipment, electric heaters, working mother machines and various power units. Because it can not only turn on and off the circuit, but also has low voltage release protection, and is widely used in the market. In industrial electricity, there are many types of AC contactors, and the current ranges from 5A-1000A, and the modified engineering plastics used in its products are relatively more. The specific use parts are shown in Table 2 below:
The modified plastic materials used in the AC contacter products are mainly PA66 engineering plastics, which are required to meet the requirements of UL-941.6mmV-0, environmental protection to meet the EU RoHS and REACH standards, GWT of the glow wire ignition temperature (GWT) of 960℃, good electrical insulation performance and meet the ink printing and other functions. There are also a small number of plastic parts using modified PBT and PA6 engineering plastics, and the requirements are basically the same. Due to the wide range of currents controlled by AC contactors (5A-630A), the internal materials used for AC contactors, especially those close to metal contacts, Usually the material must meet the requirements of high temperature resistance, flame retardantul-941.6MMV-0, good electrical insulation, arc resistance and high electrical resistance, that is, the leakage resistance trace index CTI=550-600V, most of the main use of DSM high temperature resistance long PA46 and PA4T, the brand is PA46CR310 and PA4TF11. Both are 30% glass fiber reinforced, halogen free flame retardant and high temperature resistant dragon materials.
The first domestic foreign investment, joint venture and large private enterprises are mainly based on BASF modified PA66 engineering plastics used in the medium and low voltage current controlled AC contactor products. After 2005, it was also forced by the competition in the market price of products in this field that low-voltage electrical enterprises must reduce costs and start the localization of imported modified plastic materials. Therefore, the materials in this field were gradually replaced by domestic modified engineering plastics enterprises with certain research and development strength. Domestic materials are mainly modified dragon materials provided by Jinfa, Knight, Juner and Beijing Chemical Industry Research Institute.
2.3 Application of modified engineering plastic materials in terminal and connector products
In low-voltage electrical control systems such as distribution cabinets, plastic parts that need to connect various power supply, signal and signal processing circuit systems are usually called connectors and connectors. The use of these plastic parts can be more simple, convenient and quick to connect different types of power supply, signal and other lines. Such terminals and connectors are also one of the important applications of modified engineering plastics. The specific engineering plastics used are mainly modified PA and PBT engineering plastics, and the specific requirements are shown in Table 3 below:
For a long time, Weidmuller and Phoenix, the leaders in the field of terminals and connectors, are still mainly imported materials. In recent years, with the increasingly fierce competition in the domestic market and the rise of internal costs, it has also opened the localization of imported materials. At present, some domestic enterprises have successfully developed halogen-free, red phosphorus-free flame retarding PA6 or PA66 engineering plastics that can meet the application requirements in this field.
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