High-performance rare earth permanent magnet materials can meet the requirements of micro permanent magnet motors. The use of high-performance rare earth permanent magnet materials, especially neodymium iron boron permanent magnet materials in micro-permanent magnet motors is the development direction in recent years and a later period, and there have been many successful applications at home and abroad. This article comprehensively introduces these application examples.
5. Rare earth permanent magnet micromotors used in information equipment
In order to meet the needs of high-precision and miniaturization of information equipment such as cameras, camcorders, and printers, Canon of Japan introduced the CAM series of rare-earth permanent magnet micro stepping motors. It overcomes the sharp drop in power and deteriorating efficiency of electromagnetic motors after their size is small The shortcomings of it have the characteristics of large power-to-volume ratio, simple structure and easy mass production. The structure design is very ingenious. Two coils clamp the two ends of the rare earth permanent magnet as the rotor. The left and right stators are made into another shape and form the magnetic poles of the stepping motor, which are fixed by a non-magnetic material shell. The magnetization phases of the stators at both ends are different by half a step, and the direction of current supplied to the stator coils at both ends is alternately switched to form a rotating stepping magnetic field, which makes the rotor rotate. The coaxial structure is conducive to the effective use of the magnetic flux of the coil, and the space is compact and easy to assemble. At the same time, the diameter of the magnet is as large as possible and the output torque is improved. Japan's Fuji Electric Research Institute has developed an axial gap type rare earth permanent magnet electromagnetic micromotor. The magnetic film thickness of the rotor is 2.5m. It adopts thin 4-pole magnetization and is made by sputtering technology. The paired with this is a 6-pole thin film stator. The use of planar laminated film winding coils well overcomes the difficulty of processing micro-coils with high requirements and difficulty in mass processing.
6. Application of rare earth permanent magnet linear motors on machine tools
With the rapid development of electronic technology, the emergence of high-speed, multi-functional or dedicated microprocessors, signal processors and high-performance rare earth permanent magnet materials, linear motors, especially rare earth permanent magnet linear motors, have developed rapidly. Its applications are constantly expanding. High-speed and ultra-high-speed precision machining developed in order to improve production efficiency and improve the processing quality of parts has now become a major trend in the development of machine tools. The use of linear motors has changed the "rotating motor + mechanical conversion link (such as roller screw, rack and pinion, etc.)" mode of the transmission, which has increased the processing speed, reduced the processing noise, simple maintenance, good reliability, and has High transmission accuracy and positioning accuracy; the use of DC motor as the transmission device can simplify the structure of the machine tool, establish a new machine tool layout, and may enable the machine tool to realize a new principled process, thereby realizing high-precision, high-speed processing of special-shaped sections. There is a rare earth permanent magnet DC AC servo motor system used on CNC machine tools. The motor is a single-sided flat plate, and the stator (bed) is alternately installed with NdFeB permanent magnets along the stroke direction.
The mover is the workbench, and the armature windings and Hall sensor elements are correspondingly installed below it. The mover is supported by the guide rails on both sides to ensure the air gap size. A linear grating is fixed on one side of the guide rail. Among them, the Hall sensor element is used for armature current commutation, and the DC grating is used for measuring the displacement of power. The resolution of the DC grating directly determines the position control accuracy of the system, and its measurement speed determines the maximum speed of the power. After the three-phase symmetrical sinusoidal current is passed through the three-phase winding of the motor mover, the air gap magnetic field is generated. When the end effect is not considered, it can be regarded as a sinusoidal distribution along the unfolding direction. When the three-phase current changes with time, the air gap magnetic field will translate along a straight line in a certain phase sequence, which is called a traveling wave magnetic field. The excitation magnetic field of the permanent magnet interacts with the traveling wave magnetic field to generate electromagnetic thrust, so that the mover moves in a straight line in the direction opposite to the traveling wave magnetic field.
7. Rare earth permanent magnet synchronous motor for elevator drive
Elevators are an indispensable means of transportation for high-rise buildings. With the expansion of the scale of buildings, higher requirements are put forward for the speed control accuracy and speed range of elevators. Safety and reliability, comfortable riding, low energy consumption, low noise, good electromagnetic compatibility, and remote monitoring are the standards for measuring the performance of modern elevators. Multi-variety, intelligent and green environmental protection will be the development direction of elevators. The core part of the elevator is its drive system. The elevator drive system controls the starting acceleration, steady-speed operation and braking deceleration of the elevator, and its performance directly affects the elevator's starting braking, acceleration and deceleration, leveling accuracy, and riding comfort. Due to the particularity of the use occasion, the elevator drive motor should have performance requirements such as low vibration, low noise, low starting current, sufficient starting torque and smooth operation.
Permanent magnet synchronous motors have the advantages of small torque ripple, stable speed, fast and accurate dynamic response, strong overload capacity, high efficiency and energy saving, and low noise. They have become the new favorite of today's elevator industry. In recent years, with the advancement of rare earth permanent magnet materials and permanent magnet motor technology, the development and production of rare earth permanent magnet synchronous motors for use in elevator drive mechanisms has attracted more and more attention from the elevator industry at home and abroad. The typical structure of a rare earth permanent magnet synchronous motor is that the eight large teeth of high-quality silicon steel are punched into the stator and rotor with evenly distributed small teeth. The stator core is laminated to form the stator core: the rotor core is manufactured by bonding technology, and the rotor It is composed of three pieces of misaligned iron cores and two high-performance annular NdFeB permanent magnets. After the rotor is processed, it is magnetized under a strong magnetic field to make the magnet reach a sufficient magnetic saturation state. Considering that the axial magnetic flux will not leak from the shaft after the rotor is magnetized, the motor shaft is generally made of non-magnetic stainless steel. Japan's Mitsubishi Corporation first used permanent magnet synchronous motors on high-speed elevator traction machines; KONE developed the EcoDiso permanent disk type gearless traction machine, which was applied to machine room elevators. The GENZ system launched by OTIS has developed an O100m permanent magnet gearless traction machine. The Wittur Group of Germany, Abit Corporation, and Montanari Giulio of Italy have all launched their own permanent magnet synchronous electric traction machines.
8. Small brushless motors and slotless motors
American AMETEK company has expanded its compact brushless motor series with a diameter of 4.318cm. This series of brushless motors have two types: 8-pole l2 slot and 4-pole 6-slot. The no-load speed can reach 15000r/min, the locked-rotor torque is ~0.056N·m, and the input voltage is customized according to l2, 24 and 36V. The standard design of this series of motors uses Hall-effect elements and rare earth permanent magnets to realize electronically controlled commutation and reduce pulsating torque, cogging torque, high current torque and demagnetization effects caused by high current: at the same time, it is equipped with a sealed speed Controller to achieve rapid speed increase and decrease.
The Mexon type high-speed brushless motor introduced by Interelectic AG of Switzerland has a size of 22×62.5mm, a speed of 50000r/min, and a power of 50W. It uses NdFeB permanent magnets and the windings are connected in a triangle or star shape. It can be equipped with a reducer, Gears, etc., the efficiency reaches 82%. Using low-cost slotted design technology and high-performance bonded NdFeB magnets, ElcomST has developed a brushless DC motor with a continuous torque output of 0.34N·m, a speed of 8000r/min, and a power output of 188W. The brush design helps to achieve high speed and fast acceleration, high continuous torque, low noise, anti-electromagnetic interference, and long life. This type of motor is mainly used in medical treatment, computer peripherals, tape drives, pump compressors, office automation, and any occasions that require precise control of the speed.
The slotless brushless DC motor developed by the American EAD company adopts slotless stator winding and rotor structure in structure, so there is no cogging torque and vibration. The stator uses high-density copper and is installed in a toothless stator ring: the rotor uses high-performance NdFeB permanent magnets, which reduces core loss, increases power, and maximizes torque/weight, and smaller windings The inductance reduces the voltage loss of the control electronics. The outer diameter of the motor is 035～147ram, the speed is 5000r/rain, and the torque constant is greater than 4.1N·m.
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