introduction

　　In recent years, with the development of power electronics technology, computer technology and control theory, the global industrial motor market has grown greatly. With the emergence of rare earth permanent magnet materials and magnetic composite materials, various new, high-efficiency and special motors have appeared one after another. Due to the increasing importance of the international community on energy conservation, environmental protection and sustainable development, the production of high-efficiency motors has become the development direction of global industrial motors. In the context of global reduction in energy consumption, high-efficiency energy-saving policies have been introduced to further promote the accelerated development of the global industrial motor manufacturing industry.

　　1. The motor industry is transforming towards intelligence and energy saving

　　At present, the technology of ordinary low-voltage motors is relatively mature, but there are still many technical barriers in the fields of high-power high-voltage motors, motors for special environment applications, and ultra-high-efficiency motors. Looking at the development trend of the global motor market, it is mainly reflected in the following points: the industry is developing towards intelligence and integration. Traditional motor manufacturing has realized the cross-integration of advanced electronic technology and intelligent control technology. In the future, it is the development trend of the motor industry to continuously develop and optimize intelligent control technology for small and medium-sized motor systems used in the industrial field, and realize the integrated design and manufacture of motor system control, sensing, driving and other functions.

　　2. Motor manufacturing is developing towards differentiation, specialization, high efficiency and energy saving

　　Motor products are widely used in energy, transportation, petroleum, chemical, metallurgy, mining, construction and other fields. With the continuous deepening of the global economy and the continuous improvement of the level of science and technology, the situation that the same type of motor was used in different natures and occasions in the past is being broken, and the motor products are gradually developing in the direction of specialization, differentiation and specialization.

　　In recent years, relevant global environmental protection policies have pointed out clear policy directions for improving the efficiency of motors and their control systems. Therefore, the motor industry needs to speed up the energy-saving transformation of existing production equipment, promote efficient and green production processes, develop a new generation of energy-saving motors, motor systems and control products, and test equipment, improve the technical standard system for motors and systems, and focus on improving the quality of motors and system products. core competitiveness.

　　3. Optimized design and material selection of high-efficiency and energy-saving motors

　　High-efficiency and energy-saving motors use high-quality materials and optimized designs for higher efficiency. For example, the higher the aluminum content in the rotor, the higher the slot filling factor in the stator and the lower the resistive losses. Optimized rotor structure and rotor-stator air gap reduce stray load losses. The cooling fan design is improved to minimize the windage loss of motor cooling, and the rotor and stator cores are made of higher quality and thinner steel laminations, which greatly reduces the magnetization loss.

　　3.1 Optimizing the size of stator and rotor laminations and the quality of the steel used

　　Hysteresis loss and eddy current loss together are called core loss, and about 20% of the total loss is caused by eddy current and core saturation. Eddy currents created in the laminations move relative to the changing magnetic field, causing significant power losses. Laminated stator cores reduce eddy current losses, and based on iron mass, resistivity, density, thickness, frequency and flux density, eddy current losses can be minimized with more laminations.

　　Hysteresis losses are created by the magnetic circuit when the magnetic flux is constantly changing. Most load-bearing materials used in electric machines are steel for the stator and rotor cores. By reducing the thickness of the laminations, the flux density and core losses are minimized. Hysteresis losses can be reduced by annealing a better grade of lamination steel to change the grain structure for magnetization. Eddy current losses are reduced by increasing the resistivity of the silicon-containing steel, but the silicon content increases die wear during stamping because it increases the hardness of the steel. Damaged steel crystals during stamping severely degrade the magnetic quality of the affected volume. Annealing flattens the lamination and recrystallizes crystals damaged during the stamping process, extending one sheet thickness into the lamination.

　　3.2 Stator Lamination Using the Immersion Bath Process

　　Impregnated stators provide enhanced electrical insulation of stator windings, protection from chemicals or harsh environments, and enhanced heat dissipation. Thermosets including epoxy, phenolic and polyester are used to impregnate the stator, which is where the stator is dipped in resin for an extended period of time to ensure optimum penetration and protection. Another impregnation method, called vacuum pressure, uses a tank that is evacuated and then pressurized to achieve penetration of the stator. It realizes the extraction of air pockets from the electrical winding, and improves the thermal conductivity of the winding.

　　3.3 Optimizing the design of the stator slots to maximize the volume of copper that can be inserted

　　The slot full rate affects the quality of the stator winding to a certain extent. A low slot full rate will lead to 60% of the total loss. Therefore, in order to reduce the total loss, the quality of the stator winding must be larger, thereby reducing the resistance. High-efficiency motors contain more than 20 percent extra copper compared to standard-efficiency motors, and the insulated windings of the stator are placed in slots in the steel sheets. The cross-sectional area must be large enough to meet the power rating of the motor. In general, induction motors use open or semi-closed stator slots. In semi-closed grooves, the opening of the groove is much smaller than the width of the groove, making winding more difficult and more time-consuming to manufacture compared to open grooves. The number of stator slots must be chosen during the design phase, as this number affects weight, cost and operating characteristics. The advantages of multiple slots are reduced leakage reactance, reduced tooth pulsation losses, and improved overload capacity, the disadvantages of more stator slots are increased cost, increased weight, increased magnetizing current, increased iron losses, poor cooling, increased temperature rise, and decreased efficiency.

　　3.4 The rotor die-casting adopts high-quality pure aluminum

　　The custom-designed rotor maximizes starting torque, reduces conductor resistance, and increases efficiency. Most induction motor rotors are of a squirrel cage design. Rugged, simple in construction and less expensive, they have lower starting torque. Copper rotors improve efficiency but are difficult and expensive to manufacture.

　　3.5 Optimum air gap between rotor and stator

　　The air gap is the radial distance between the rotor and stator of the motor in a standard radial motor. In order to improve the design efficiency, it is necessary to maintain the optimal air gap. Air gap dimensions relate to the design of the stator, rotor, motor housing and bearings. All of these affect the precise alignment of the stator and rotor shafts.

　　3.6 Use electromagnetic enameled wire with excellent performance

　　Magnet or enameled wire is an electrolytically refined copper or aluminum wire that has been fully annealed and coated with one or more layers of insulation. For example, use a wire with a total of 12 layers of insulation. Typical insulating films, with increasing temperature range, are polyethylene, polyurethane, polyester and polyimide, up to 250°C. Thicker rectangular or square magnet wire wrapped with high temperature polyimide or fiberglass tape, using more copper, larger conductor bars and conductors increase the cross-sectional area of the stator and rotor windings, reducing winding resistance, reducing Losses due to current, high-efficiency motors typically have 20% more copper in the stator windings.

　　The motor is composed of many parts, each part provides different structural and functional properties, resulting in different functions in the motor system, and the pros and cons of the functions provided by each part will ultimately affect the input performance of the motor. By optimizing the performance of each component of the motor, the performance of the motor is finally optimized.

　　4 Conclusion

　　At present, in response to the globalized market competition, the motor manufacturing industry is gradually changing from "large and comprehensive" to "specialized and intensive". With the development and improvement of the motor intelligent control system, the specialization in the industrial motor industry is further promoted. The development of production models. In the future, driven by low-carbon environmental protection policies, industrial motors will develop towards green and energy-saving in an all-round way.

　　references:

　　[1] Chen Jingang, Huang Liming, Energy-saving system design of low-voltage high-efficiency variable frequency motors [J], Ship Power Technology, 2019(2):34-36.

　　[2] Chen Weihua, Development of Motor Industry and Policy Opportunities [J], Application of Motor and Control, 2017(7):1-6+25.

　　[3] Hongchao Sun, Wenhui Liu, Fuchun Wang, Research on Design Method of High Efficiency Motor [J], Explosion-proof Motor, 2014(2):1-4.

　　About the Author:

　　Chen Jingang, male, born in October 1974, graduated from Beijing University of Aeronautics and Astronautics with a major in mechanical and electrical engineering in 1996, and has been engaged in the design, selection, detection and failure analysis of low- voltage electrical equipment in Dezhou Hengli Motor Co., Ltd., 2020 Promoted to Senior Engineer.