1. Technological advancements drive the development of permanent magnet brushless motors.
Looking towards the 21st century, micromotors, designed to coexist with the Earth's environment, integrate with networks, and meet the requirements of robotics, will experience rapid development, ushering in a "new era for micromotors." Coexistence with the Earth's environment demands motors that are highly efficient and energy-saving, high-output and material-saving, quiet and comfortable, and harmless and pollution-free. Integration with networks requires miniaturization, flatness, high speed, lightweight, high precision, and high performance. Meeting the requirements for robotic motors demands high output, low inertia, low-speed high torque, and intelligence. To meet these requirements, foreign micromotor manufacturers are placing great emphasis on the research and development of permanent magnet brushless motors and drive control technologies. Optimized motor design, rational parameter selection, reduced torque ripple and noise, and expanded speed range; multi-pole concentrated windings to reduce winding end length; modular or hinged armature laminations to improve fill factor; research into high-efficiency, high-performance drive control technologies; and the adoption of high-performance permanent magnet materials give permanent magnet brushless motors advantages such as high efficiency and energy saving, high output and material saving, high reliability and high performance, small size, and light weight.
2. Market demand accelerates the development of permanent magnet brushless motors.
(1) Micromotors used in the network field account for about 38% of all micromotors. HDD spindle motors, printer spindle motors, copier spindle motors, computer fans, and high-end DVD spindle motors all use permanent magnet brushless motors. Moreover, they are precision permanent magnet brushless motors. Due to the high precision requirements, they all use bonded neodymium iron boron. 83% of bonded neodymium iron boron is used in this type of permanent magnet brushless motor in Japan. They have a solid armature lamination, multi-pole concentrated winding, and an external rotor structure. Vibration motors used in mobile phones, whether cylindrical or button-type, mostly use brushed DC motors, but there are also brushless vibration motors, which are not widely used at present.
(2) Motors used in the home appliance sector account for approximately 15% of all micro-motors. Air conditioners, washing machines, refrigerators, and other major home appliances initially used single-phase asynchronous motors. Due to their low efficiency and utilization rate, variable frequency speed-regulating asynchronous motors were adopted in the early 1990s for energy conservation. Currently, over 90% of air conditioners in Japan use permanent magnet brushless DC motors to replace variable frequency speed-regulating asynchronous motors. Air conditioner manufacturers in my country have also begun to adopt permanent magnet brushless DC motors to achieve better energy-saving effects and material savings. Under the same rated power and rated speed, assuming the volume and weight of a single-phase asynchronous motor are 100%, the volume of a permanent magnet brushless DC motor is 38%, the weight is 34.8%, the copper content is 20.9%, the iron content is 36.5%, and the efficiency is increased by more than 10%. To maximize efficiency, the permanent magnets of the motor use sintered neodymium iron boron, the armature laminations use a modular or hinged design, and multi-pole concentrated windings. Depending on user requirements, the motor can be made with an external rotor or internal rotor structure. The trend is towards the increasing adoption of permanent magnet brushless motors in home appliances such as air conditioners, washing machines, and refrigerators.
(3) The use of drive motors in the electric vehicle sector: In 2004, my country produced 6.7571 million electric bicycles, a year-on-year increase of 69.05%. Most of these electric bicycles used brushed DC motors. However, due to the inherent disadvantages of brushed DC motors, such as short lifespan and difficult maintenance, the use of permanent magnet brushless DC motors has increased as the price of permanent magnet brushless DC motors has decreased and the reliability of controllers has improved. With energy shortages and increasing environmental pollution, electric vehicles have shown strong vitality and are favored by car manufacturers and consumers. Data shows that by 2010, electric vehicles will account for a quarter of global car demand, with a total of 20 million vehicles. Major car companies such as General Motors in the United States, Toyota in Japan, and Citroën in France have all made electric vehicles their development direction. my country also attaches great importance to this, listing it as a major national research project during the "15th Five-Year Plan" period by the Ministry of Science and Technology, and it is also one of the important contents of the "11th Five-Year Plan" for developing green transportation. Electric vehicle drive motors include brushed DC motors, variable frequency asynchronous motors, and permanent magnet brushless motors, but the trend is towards permanent magnet brushless motors, especially Japanese car manufacturers. The drive motors in automotive electric power steering systems include brushed DC motors and permanent magnet brushless motors, but the trend is towards permanent magnet brushless motors. It will be a trend for permanent magnet brushless motors to replace brushed DC motors in motors used in important safety systems of electric vehicles. The permanent magnets in these motors use sintered neodymium iron boron, and the winding forms include concentrated windings and distributed windings. The motor structures include external rotors and internal rotors. As for general motors used in automobiles, brushed DC motors are still the dominant type, with micro-motors used in automatic vehicles accounting for approximately 17% of all micro-motors.
(4) After the elevator adopts the permanent magnet brushless synchronous motor servo control system, it not only has small size, energy saving, and good control performance, but also easily realizes direct drive to eliminate gear reduction device. The low noise, leveling accuracy and comfort are all better than the previous brushed DC motor speed regulation and asynchronous motor frequency conversion speed regulation. It is suitable for use in machine room-less elevators. Therefore, permanent magnet brushless synchronous motor drive has been favored by major elevator companies.
(5) The feed drive of high-speed and high-precision machining tools is currently mainly based on the traditional rotary servo motor plus precision high-speed ball screw structure. Since the early 1990s, linear motor direct drive has been used. Compared with the traditional structure, it has a series of advantages, such as a 30-fold increase in speed, a 10-fold increase in acceleration (up to 10g), and a 7-fold increase in stiffness. Of course, linear motor direct drive also has some disadvantages and problems, such as high control difficulty, magnetic interference, and high cost. However, the general trend is that the proportion of linear motor drive will become larger and larger, and it is very likely to become the main body of machine tool feed drive in the future. Due to the advantages of high efficiency, high thrust density, and good controllability of permanent magnet brushless synchronous linear servo motor, although it has high requirements for magnetic shielding and dust prevention and is difficult to assemble, it has now become the mainstream of linear motors for machine tools.
(6) Other fields include micro motors for armed equipment, robots, and aerospace. These fields use various types of motors with a wide variety of specifications. For example, the US military has more than 5,000 types of micro motors, with an annual production of only 3 million units. With the development of robotics and aerospace, the demand for micro motors will increase, and the requirements will also become more stringent. Servo drive motors in these fields are also developing towards permanent magnet brushless motors. For example, Kollmorgen, a key company in the United States that researches and produces micromotors for military and aerospace use, has two series of permanent magnet AC servo motors. The M series has 5 frame sizes and 47 models, with power ranging from 0.54 to 15.7 kW, speed from 900 to 1200 r/min, continuous torque from 0.89 to 115 N·m, and peak torque from 2.41 to 326.8 N·m. The MT series has 4 frame sizes and 24 models, with power ranging from 0.231 to 6.7 kW, speed from 1500 to 6000 r/min, continuous torque from 0.44 to 46.8 N·m, and peak torque from 1.25 to 115.4 N·m. The MT series products are smaller, more efficient, and have lower moment of inertia than the M series products. Their rotatable connectors further enhance the speed, miniaturization, reliability, and maintainability of weaponry, meeting the requirements of servo control systems for weaponry. They are widely used in radar, aerospace, and other fields. The United States has already used permanent magnet brushless motors as drive sources in armored vehicles, replacing brushed DC motors and improving vehicle performance. Motors with a rated power of 3820kW, a rated voltage of 2800V, and a rated speed of 135r/min, produced by Siemens (Germany) and ABB (Finland), are used in podded propulsion systems of luxury cruise ships, icebreakers, and engineering vessels. They are now being promoted for submarines, replacing brushed DC motors and improving submarine performance.
