After several years of development, mine-use explosion-proof electrical products have made many progresses. Coal mine electrical automation technology, coal mine safety production monitoring system and other automation products have reached a certain level. Mechatronics technology and power electronic speed control technology have been used in coal mines. Underground transportation machinery, hoisting machinery and coal mining machinery have begun to be widely used. It should be said that after years of development, a relatively complete manufacturing system for explosion-proof electrical products has been formed, which basically meets the current development needs of underground coal mines for power supply and distribution, underground mechanization, and control and protection.
In recent years, explosion-proof electrical products for mines have been expanded in styles and specifications, such as explosion-proof high and low voltage soft starters for mines, explosion-proof frequency conversion speed control devices for mines, explosion-proof high and low voltage combination switches for mines and other new technology products. It has also been widely used underground in coal mines. Due to continuous and stable demand, my country's mining electrical products production has formed a larger manufacturing industry, and peer competition has become increasingly fierce. How to avoid price competition, avoid low-level repetitive production, and develop enterprises through technological innovation has become a question for every manufacturer and operator of mining electrical appliances. Where is the route for the successful development of an enterprise? Only technological innovation is the only way to win the market by developing high-tech, high-value-added mining electrical products. At the same time, in terms of social benefits, only through technological innovation and development of coal mining mechanization, electrification and automation can we promote the establishment of a truly intrinsically safe modern mine.
Technological innovation is an important indicator basis for measuring whether an enterprise is advanced, whether it has market competitiveness, and whether it can continue to be ahead of competitors. With the rapid development of my country's mining electrical appliances market, the application and research and development of core production technology related to it will surely become the focus of attention of enterprises in the industry. Understanding the research and development trends, process equipment, technology applications and trends of the core technology of domestic and foreign mining electrical appliances production is crucial for companies to improve product technical specifications and improve market competitiveness. Although new products such as high and low voltage soft starters, high and low voltage combination switches, and frequency conversion speed regulation devices are constantly being developed, the development of these products is still subject to many restrictions. Many core components of explosion-proof electrical products still rely on foreign technology. There is still a big gap between the production level of these core components and similar foreign products. Technological innovation generally goes through three stages from initial research and development to maturity: introduction period, growth period and maturity period. During the introduction period, technological development is very slow, and it often takes a long time to break through; for example, about 50% of our current stage of frequency conversion speed control device, about 50% of mining explosion-proof enterprises directly purchase foreign movement assembly production; 40 % Of enterprises adopt domestic technology to absorb and utilize, and only about 10% of enterprises can develop and produce independently. At the same time, the research on the EMC performance of the inverter is still in the preliminary stage, but this stage gives us challenges. How to overcome the impact of the inverter output harmonics on the power supply and monitoring equipment of the power grid has become the target of many companies. It will also become the next stage of development goals. When the technological innovation is in the growth stage, the technology develops rapidly, and the technical performance is rapidly improved; for example, the current frequency conversion traction shearer, using the characteristics of frequency conversion constant power speed regulation and PLC centralized control, is increasingly used in the application of the shearer Mature, improving the working efficiency and reliability of the shearer, and basically replacing the hydraulic traction technology; another example is the hydraulic winch, which integrates electricity, oil, and gas. The operation is complicated, backward, noisy, and the maintenance workload is also large. , After adopting explosion-proof frequency converter technology, the production process has been completely changed, and it has been recognized by users of coal enterprises. When technological innovation enters a mature period, the technology is relatively stable, no major changes will be made, and technological progress is reflected in partial improvements. For example, the current high and low voltage combination switch is close to the existing foreign level. The application of electronic technology such as PLC, DSP, and fieldbus provides technical support for the stable operation of the combination switch, and the relevant cable entry devices have basically reached domestic production. The unit structure of the combination switch has also made considerable progress. Only by recognizing the three development processes of technological innovation can we accurately position the development ideas of our products.
Many companies also recognize the necessity of technological innovation, but are struggling to find a breakthrough. In view of the current product status, where is our technological innovation goal? In fact, the previous starters, feed switches, and electric control boxes are mainly protected by discrete component circuits, which have the disadvantages of unstable components and large drift. The application of monolithic technology on the protector brings convenient operation and performance. The advantages of stability; the coordinated application of the man-machine interface makes the operation clearer, and the fault memory function provides a basis for coal mine enterprises to analyze problems. Technological innovation is also focused on the continuous improvement of its own product performance. For example, a company’s GM series coal shearer isolation switch has a market share of more than 90%, and its stable performance has been recognized by the same industry; a company’s miniaturized flameproof and intrinsically safe water level control starter has also won the industry And the recognition of coal enterprise users. Many successful cases of enterprises are worthy of our study and reference. Enterprises should change their blindly following the trend and seek completeness in products, only considering the coverage, and neglecting the improvement of the performance of their own specialties. Technological innovation and independent intellectual property rights are also the guarantee for the development of our mining explosion-proof enterprises.
Grasping the development trend of products also grasps the market. Aiming at the development trend of mining products, the following three points are put forward in terms of mining explosion-proof electrical appliances:
First, the basic performance research of electrical appliances
my country began to use vacuum tubes in the early 1980s. At present, mine explosion-proof vacuum switches have been widely used in underground mines. The use of vacuum tubes has played a great role in the safe power supply in coal mines. For example, the explosion-proof vacuum electromagnetic starter products for mines have strong ultimate breaking capacity, which is suitable for frequent starting of underground motors and low maintenance; mine explosion-proof products The full breaking time of the type vacuum feed switch is small, and in conjunction with the fast leakage protection, it improves the safety of anti-shock and anti-gas explosion. The demand for vacuum contactors and vacuum circuit breakers is very large, but the quality of vacuum tubes in the current market is uneven. Many production processes are still based on the early 1980s and are still relatively large compared with foreign processes. gap. In the application of vacuum tubes, there are also the influence of operating overvoltage and the guarantee of vacuum. The decrease of vacuum can easily cause leakage accidents in the well, affecting production and accidents. Some companies have also begun to devote themselves to the research of vacuum tube electrical appliances, and The research on air leakage protection has made progress in air leakage protection and vacuum tube adhesion protection methods. This is the future
Provide guarantee for the safe operation of underground electrical appliances. With the continuous development of electronic technology, the use of power electronic devices to replace vacuum tubes to realize the start and stop control of the motor will be the development direction. It has been used in the control of comprehensive protection of coal electric drills, such as the non-contact shutdown of thyristors. Control, increase the service life, safe and reliable. The application of high-power SCR in the starter has also changed the performance of the traditional starter. While the use of power electronic devices gives new vitality to the performance and reliability of explosion-proof electrical products, it also brings new issues to the explosion-proof and safety technical requirements of the products.
Second, the selective leakage research of low-voltage feed switch
Leakage protection is one of the three major protections for underground electrical appliances in coal mines, and the reliability of its protection affects coal mine safety production. The current selective leakage protection principle of low-voltage feeder switch is still based on the protection mode of zero-sequence voltage and zero-sequence current; in addition, an external DC is used to continuously monitor the insulation of the power supply network. Due to the lengthening of the power supply network and the application of shielded cables, as well as the application of power electronic devices such as frequency converters, the underground power supply network is complicated. There are many stray characteristics in selective leakage protection and the uncertainty of distributed capacitance. Requirements for leakage protection are put forward. Using advanced digital acquisition technology, how to analyze the condition of the distributed capacitance in the well, to achieve precise selective tripping and cutting off the faulty branch without affecting other working branches, and to ensure the reliable and safe power supply underground is also a new topic that urgently needs to be studied.
Third, the development of mining AC inverter products
Due to the continuous progress and development of science and technology, the application of high-power electronic appliances in underground mines has developed rapidly. Among them, the AC variable frequency speed regulation device has the advantages of high efficiency, low failure rate, and good control performance, which can significantly improve the production process. With the attention of the coal production industry, the mine frequency conversion speed control device used to be mainly used for speed control of about 100kW, such as coal mining electromechanical traction parts. Generally, the front stage has a special transformer to supply power, which has little impact on the power grid. However, as the frequency converter technology continues to mature, since the successful use of electric traction shearers in the 1980s, coal mine production equipment such as ventilators, winches, hoists, air compressors and other mechanical equipment have begun to use frequency conversion speed regulation technology. Not only changes the traditional production process, but also mainly embodied in high efficiency and energy saving. For example, the main fan of a mine is selected according to the maximum air volume requirements of the mine’s production service life. From the construction of the shaft to the production until the mine is scrapped, the air volume required in each period is different, and the difference is very large. The use of mechanical adjustment of the air volume causes a lot of waste of electricity. Fans save energy by using frequency converter technology. Another example is that the local fans in the mining face are installed in many places and run for a long time, which is a large energy consumer. Due to the continuous expansion of coal mining, the air volume required for a long time is much less than that of ventilation. The air supply capacity of the machine, in view of the current situation of this kind of big horse-drawn trolley, the energy-saving effect of using frequency conversion speed regulation technology is also very obvious. Due to the high efficiency of the frequency converter and good speed regulation performance, it can implement electric braking and stepless speed regulation to save energy. It is an inevitable trend to use frequency conversion technology more widely in coal mines. But at present, neither product development nor testing technology can keep up with the needs of production development.
According to the application experience of the ground frequency conversion speed control device, it is necessary to make good use of the frequency conversion speed control device, and the power supply, frequency converter motor, and production machinery must be combined with the production technology as a system to study, and appropriate suppression measures shall be taken to the harmonics of the power grid. In order to adapt to the development of coal mine frequency conversion electrical technology, research the performance of high-power frequency conversion equipment for mines, the research of frequency converter EMC and the effect of wave suppression measures and other technical issues, and provide an advanced technology for the field of scientific research, design and production of mine frequency converters. The test platform is imminent.
How to carry out EMC detection so that the mine frequency converter can be used in the coal mine "green" and reduce the harm to coal mine production has become an important topic for the detection department in the next stage.
my country is the world's largest coal producer, and coal is my country's largest energy source. Aiming at the development trend of the above three points, the development of coal mining mechanization and electrification through technological innovation is of great significance to the modernization of coal mines. In order to meet the requirements of enterprise technological innovation and development, our testing organization will continue to improve its capabilities and provide advanced testing methods and testing methods. In response to the needs of technological development, the National Safety Production Shanghai Mining Equipment Inspection Center has also continuously improved its inspection capabilities and levels. For example, a large-scale explosion-proof test tank of 3.4m has been included in the planned project to adapt to the inspection of large-scale mining electrical equipment. Need: The inspection capability of mine explosion-proof inverters will be raised to the level of 1000kW to meet the test needs of large-capacity high-voltage motors and high-voltage inverters. Our testing department will use advanced testing technology support as a means to strengthen exchanges and cooperation with enterprises, and provide technical support for the technical innovation and safety management of mining explosion-proof electrical products.
