Do Permanent Magnet Motors Need To Be Magnetized? What Are The Types Of Magnetizing Devices?

With the continuous development of industry and the promotion of rare earth permanent magnet materials, the demand for magnetization equipment in the application industry of permanent magnet motors and other permanent magnet materials is gradually increasing; At the same time, new requirements have been put forward for the energy consumption, volume, magnetization effect and other performance aspects of magnetization equipment. Due to the fact that the magnetization process is completed in a very short period of time, the magnetic field variation is a spatial function. When using simple magnetic circuit empirical calculations, many parameters are difficult to accurately determine and require three-dimensional electromagnetic field numerical calculations. With the rapid development of computer hardware and software technology, finite element method has become a key technology for accurately calculating and analyzing the electromagnetic field of magnetization systems.
From the perspective of magnetizing current
1) DC magnetizer: This type of magnetizer has been basically eliminated due to its high energy consumption, slow start-up, difficult cooling, and limited formation of strong magnetic fields. Only the Southwest Institute of Applied Magnetics still retains one;
2) Pulse magnetizer: Due to its easy formation of high-strength magnetic fields, short magnetization cycle, suitable for continuous magnetization, low energy loss, low cost, and easy solution to cooling problems. The device has a small size. So currently, almost all use this type of magnetizer.
2. From the perspective of magnetizing voltage
1) High voltage magnetizer: Currently, there are voltages of 4000V, 2000V, and 1000V, and the energy storage of capacitors is proportional to the square of the voltage. Therefore, increasing the charging voltage of capacitors can significantly increase the capacity of the device. When saturating high coercivity rare earth cobalt permanent magnetic materials, high-voltage pulse magnetization is used, which has significant practical value;
2) Low voltage magnetizer: Low voltage includes 600V, 450V, and 400V. This magnetizer uses electrolytic capacitors, which are relatively small in size but have high leakage. The quality of these capacitors in China is not very good, and they consume a lot of energy. However, from the perspective of reducing volume, they are still feasible. And the introduced magnetizers mostly use this type.
3. From the perspective of the magnetizer switch
1) Li flow tube switch magnetizer: It is quite old-fashioned and only one company in China uses it;
2) Ball gap switch magnetizing machine: used in the early days, with noise, not suitable for long-term frequent operation, only one company in China adopts it;
3) Air switch magnetizer: This type of magnetizer generates electric arcs during operation, pollutes the environment, and produces significant noise. It has poor reliability over long periods of time, low cost, and can be used for scientific research purposes. Only one company in China uses it;
4) Vacuum switch magnetizer: This magnetizer is better than an air switch magnetizer, but it still belongs to a switch with contacts, which has poor reliability in production and may cause radio interference;
5) Ignition tube switch magnetizer: This type of magnetizer is mostly used on large capacity magnetizers and is not suitable for long-term frequent operation. However, it has been retained on magnetizers manufactured in the past (including three of the largest capacity magnetizers in China from the University of Science and Technology of China);
6) Quality control switch magnetizer: Most of the high-voltage or low-voltage magnetizers produced in China recently use controllable switches for discharge. This type of switch is commonly used in imported products from abroad. Its characteristics include contactless switching, no noise, low energy loss, easy control, and small size, making it the current development direction. However, the high voltage withstand voltage of domestically produced high-voltage thyristors is not high enough, only reaching 5500V, and the surge current is not large enough, which limits the development of magnetizers towards high voltage and large capacity.
4. From the perspective of the charging head of the magnetizer
1) Ironless yoke charging head: The number of turns of the coil of this charging head is flexible and easy to make. The size and number of turns of the coil can be determined based on the required size of the permanent magnet, the calculated magnetic field strength of the permanent magnet material, and the parameters of the charging circuit. This type of magnetic head is commonly used for single piece magnetization of permanent magnets;
2) Iron yoke magnetic head: This type of magnetic head can concentrate the magnetic field, increase the magnetic field strength, and ensure a certain magnetic field waveform. It can be directly used for magnetizing permanent magnet motors with low magnetic energy product. For pulse magnetizing with high magnetic energy product, it is difficult to saturate due to the eddy current effect of the iron yoke, and the magnetic field waveform is also difficult to guarantee;
3) Integrated magnetic head: According to literature records, there are such integrated magnetic heads in China, which are only used in micro motors made of aluminum nickel cobalt and ferrite, and the magnetization waveform is not very satisfactory. There are currently few integrated magnetic heads suitable for high intrinsic coercivity in China.