The development of permanent magnet motors is closely related to the development of permanent magnet materials. my country is the first country in the world to discover the magnetic properties of permanent magnet materials and apply them to practice. More than two thousand years ago, our country used the magnetic properties of permanent magnet materials to make a compass, which has played a huge role in navigation, military and other fields. It has become one of the four great inventions in ancient my country.

Precautions for permanent magnet motors

1. Magnetic circuit structure and design calculation

In order to give full play to the magnetic properties of various permanent magnet materials, especially the excellent magnetic properties of rare-earth permanent magnets, and to manufacture cost-effective permanent magnet motors, the structure and design calculation methods of traditional permanent magnet motors or electric excitation motors cannot be simply applied. , a new design concept must be established, and the magnetic circuit structure must be re-analyzed and improved. With the rapid development of computer hardware and software technology, as well as the continuous improvement of modern design methods such as electromagnetic field numerical calculation, optimization design and simulation technology, through the joint efforts of the motor academia and engineering community, it has been widely used in the design theory, Breakthrough progress has been made in calculation methods, structural technology and control technology, etc., and a set of analysis and research methods and computer-aided analysis and design software combining electromagnetic field numerical calculation and equivalent magnetic circuit analytical solution have been formed, and are constantly improving. .

2. Control issues

The permanent magnet motor can maintain its magnetic field without external energy, but it also makes it extremely difficult to adjust and control its magnetic field from the outside. It is difficult for the permanent magnet generator to adjust its output voltage and power factor from the outside, and the permanent magnet DC motor can no longer adjust its speed by changing the excitation method. These limit the application range of permanent magnet motors. However, with the rapid development of power electronic devices and control technologies such as MOSFETs and IGBTs, most permanent magnet motors can be used without magnetic field control and only with armature control. When designing, it is necessary to combine three new technologies of rare earth permanent magnet materials, power electronic devices and microcomputer control, so that the permanent magnet motor can run under new working conditions.

3. The problem of irreversible demagnetization

If the design or use is improper, the permanent magnet motor will be under the action of the armature reaction caused by the inrush current when the temperature is too high (NdFeB permanent magnet) or too low (ferrite permanent magnet), or when there is severe mechanical vibration It is possible to cause irreversible demagnetization, or loss of magnetization, which will reduce the performance of the motor and even make it unusable. Therefore, it is necessary to research and develop methods and devices for checking the thermal stability of permanent magnet materials suitable for motor manufacturers, and to analyze the anti-demagnetization capabilities of various structural forms, so as to take corresponding measures to ensure that during design and manufacture. Permanent magnet motors do not lose their magnetism.

4. Cost issues

Ferrite permanent magnet motors, especially miniature permanent magnet DC motors, have been widely used due to their simple structure and process, reduced weight, and generally lower total cost than electric excitation motors. Since rare earth permanent magnets are still relatively expensive at present, the cost of rare earth permanent magnet motors is generally higher than that of electric excitation motors, which needs to be compensated by its high performance and operating cost savings. In some occasions, such as voice coil motors of computer disk drives, the performance of NdFeB permanent magnets is improved, the volume and mass are significantly reduced, and the total cost is reduced. In the design, it is necessary to compare the performance and price according to the specific use occasions and requirements to decide the choice, but also to innovate the structural process and design optimization to reduce the cost.

Jessica