The Most Popular Motor Magnets-Neo Arc Magnet

Arc segment motor magnet has advantages of easy manufacture and low cost compared with radial ring magnets. It’s still the most common motor magnet shape, especially for PM DC motor and magnet rotor.

As we all know, permanent Magnet is the core of PM motor.
In order to ensure the steadily electrical performance and long-term safe and reliable operation of electric vehicles, it requires the magnetic property of permanent magnet material remains stable. Considering magnetic performance influenced by the work environment, temperature and time, the reliability of permanent motor magnets can be divided into thermal stability, time stability, chemical stability, and magnetic stability.

rare earth magnet

1. Temperature stability can be shown by Curie temperature and the maximum operating temperature. As the temperature rises, the magnetic properties gradually reduce. When raises to a certain temperature, the magnetization disappears. This certain temperature is the Curie temperature of the permanent magnet materials, also known as the Curie point. The deficiency of NdFeB permanent magnet is relatively low Curie temperature, but higher temperature coefficient. Therefore neodymium magnets will be lost much magnetic force if work under high temperature. Due to the high-temperature coefficient of NdFeB permanent magnet, the magnetic properties are poor. To this end, it must pay more attention to Max. working temp.of sintered NeFeB magnet when you select a magnet grade. The test method of magnet temperature stability is the aging test

2. Chemical stability refers to the anti-oxidation and corrosion-resistant of permanent magnet material. Compared with the traditional ferrite or samarium cobalt (Smco) or alnico magnets, the chemical stability of sintered NdFeB magnet is the worst. Currently, the primarily solution is adding some alloy elements such as Co, Ni, Al and Cr, etc., while in the sintering process, increasing the density and reducing the porosity of magnetic material. Another approach is made certain magnet surface treatment such as electroplating. This can obtain a practical corrosion resistance for the magnet.

3. Time stability is putting the permanent magnet at a certain temperature for a long time, observing the change of its magnetic properties over time. These NdFeB permanent magnets added Co + Dy + Nb will obtain better time stability.

4. Magnetic stability is based on the magnetic material, and also affected by temperature, time, external magnetic field, chemical corrosion, radiation, mechanical vibration or shock and other factors.

Compared with electro-magnetic, we can list more advantages of segment arc motor magnet:
1. Simplify the structure of the motor
2. Easy maintenance
3. Light weight
4. Small volume
5. Operational reliability
6. low energy consumption

How to choose motor segment material?
For traditional AC motor, ferrite and AlNiCo segment magnets are most applied. With the higher request on motor power, more and more motor manufacturers use ndfeb and smco magnet which have super high magnetic energy product. However, they are more expensive because neodymium magnet and samarium cobalt magnet segments belong to rare earth magnet.

How to join neodymium arc magnets, which are diameter magnetized, to create a cylindrical ring that is radially magnetized?
The general approach is to make a sleeve or frame to put neo arc magnets in that will keep them in order and don’t jump around. The sleeve here has to be made of something sturdy and nonmagnetic, such as aluminum, copper or Q235 low carbon steel. Due to a strong repelling force, it’s better to operate by those experienced workers. If you are the first time to assemble segment magnets, just be careful. Halbach array magnets also utilize a frame or other tools to overcome the strong magnetic repulsive force between the same pole sides of two magnets and keep them fixing together.

What is Ferrite Used for

Ferrite is a ferromagnetic metal oxide. As far as electrical properties are concerned, the resistivity of ferrite is much larger than that of metal and alloy magnetic materials, and it also has a higher dielectric function. The magnetic function of ferrite also shows high permeability at high frequency. Therefore, ferrite has become an ordinary non-metallic magnetic material for high frequency and weak current limits. Because of the low magnetic energy reserved in the unit volume of ferrite and the low saturation magnetization, the application of ferrite in demanding high magnetic energy density at low frequency and high power band limits is limited.

Ferrite belongs to the category of semiconductor electronically, so it is also called magnetic semiconductor. Magnetite (the key component is Fe3O4) is a simple ferrite. Ferrite has been merged as early as the beginning of the 20th century. In the 30th century, France, Japan, Germany, and the Netherlands have carried out systematic discussions. The production of ferrite soft magnetic raw materials has been in the Netherlands since 1946. China started manufacturing ferrite industry around 1956. Ferrite has been widely used in communication, broadcasting, computing, automatic control, radar navigation, space navigation, satellite communications, instrument measurement, printing, pollution treatment, biomedicine, high-speed transportation, etc.

magnetic ferrites

1. Soft magnetic ferrites include manganese ferrite (MnO.Fe2O3), zinc ferrite (ZnO.Fe2O3), nickel-zinc ferrite (Ni-Zn.Fe2O4), manganese-magnesium-zinc ferrite (Mn-Mg-Zn.Fe2O4) and other single or multi-component ferrites. The resistivity is much larger than that of metal magnetic materials, and it has a higher dielectric function. Therefore, ferrites with both ferromagnetism and ferroelectricity and ferromagnetism and piezoelectricity appear. At high frequencies, it has much higher permeability than metal magnetic materials (including ferronickel alloy and aluminum-silicon-iron alloy). It can be applied to work at frequencies ranging from several kilohertz to several hundred megahertz. Processing ferrite belongs to the usual ceramic process, so the process is simple, and save a lot of precious metals, low cost.

The saturated flux density of ferrite is low, usually only 1/3-1/5 of iron. Ferrite has low magnetic energy reserve per unit volume, which limits its use in demanding high magnetic energy density at low frequency, high current, and high power band boundaries. It is more suitable for high frequency, low power, and the weak electric field surface. Nickel-zinc ferrite can be used as antenna rod and medium frequency transformer core in radio, and manganese-zinc ferrite can be used as line-conveying transformer core in the TV receiver. In addition, soft magnetic ferrites are also used to add sensors and filter cores in communication lines. High-frequency magnetic recording transducer has been used for many years.

2. Permanent magnetic ferrites include barium ferrite (BaO.6Fe2O3) and strontium ferrite (SrO.6Fe2O3). High resistivity, belongs to the semiconductor category, so eddy current consumption is small, the coercive force is large, can be used effectively in the air gap magnetic circuit, unique for small generators and ideas of permanent magnets. It does not contain precious metals such as nickel and cobalt. The raw materials are excellent, the process is not complicated and the cost is low. It can be used as a substitute for AlNiCo permanent magnet. Its contrast large magnetic energy product is lower, so it is larger than metal magnet in the condition of considerable magnetic energy. Its temperature stability is poor, its texture is brittle and fragile, and it can not withstand the impact and sensation. It is not suitable for measuring instruments and magnetic devices with careful requirements. The products of permanent magnet ferrite are mainly anisotropic series. They can be used to manufacture permanent magnet starter motor, permanent magnet motor, permanent magnet concentrator, permanent magnet suspender, magnetic thrust bearing, magnetic broadband separator, loudspeaker, microwave device, magnetic therapy sheet, hearing aid, etc.

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