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An inner rotor refers to the rotating part of the motor being located inside the stator. So, what kind of magnet is used on the inner rotor?
The primary function of the magnets on an internal rotor is to generate a magnetic field that causes the motor to rotate. As for the type of magnet used, this varies depending on the specific motor. Common magnets used in internal rotors include neodymium-iron-boron magnets, ferrite magnets and samarium-cobalt magnets, with radial external magnetisation.
Neodymium-iron-boron magnets are currently the most widely used. Their advantages include strong magnetic force, compact size and high motor efficiency; consequently, they are the preferred choice for many high-speed and miniaturised motors. For example, the inner rotors of drones, power tools and electric vehicle drive motors often utilise neodymium-iron-boron magnets.
Radial magnetisation is typically used for magnetising the inner rotor.
For products with lower cost requirements, ferrite magnets are typically used. Although their magnetic strength is not as high as that of neodymium-iron-boron magnets, they are inexpensive and offer good corrosion resistance. Applications such as toy motors and car windscreen wiper motors often utilise ferrite magnet tiles or multi-pole magnetic ring structures.
Another type is samarium-cobalt magnets. These magnets offer excellent high-temperature resistance and are suitable for high-temperature environments or equipment requiring high reliability, such as certain motors used in aviation, power tools and the defence sector. However, due to their high cost, they are not used as widely as neodymium-iron-boron magnets.
The method of mounting magnets in internal-rotor motors also varies. In some cases, they are attached directly to the surface of the rotor, known as surface-mounted. In others, they are embedded within the rotor core, known as an internal-embedded configuration. Many drive motors in modern new energy vehicles now utilise this internal-embedded magnet structure, which offers higher rotational speeds and improved efficiency.
Magnets for motor rotors;
This is a very small rectangular ferrite block magnet, measuring 2.45 mm in length and 1 mm in both width and height. It is magnetised along its length and is barely noticeable when held in the hand....
7.4x6x5mm Ferrite Small Block Magnet Introduction，Material: Hard Ferrite (Ceramic)，Shape: Block / Rectangle / Bar，Coating: No Coating，Grade (Chinese Stardard): Y30，Operating temperature: -40°C to 250°C，Delivery time: 7-15 days，Magnetization direction: thickness....
U-shaped neodymium magnets are a type of high-performance permanent magnet material with a structure resembling the letter ‘U’. Manufactured from sintered neodymium-iron-boron, they are characterised by high magnetic energy product....
This is a radial 4-pole ring (Hollow cylinder) magnet, the material is bonded NdFeB, with high magnetic performance, the size is 16mm outer diameter, inner hole 5mm, height 20mm, surface gray epoxy treatment, suitable for water pump motor...
This product is a 4-pole ring magnet, injection-molded ferrite material, the sample size is 22mm outer diameter, 7mm inner diameter, 4mm thickness, 2 N poles and 2 S poles, mainly used for push rod motors, magnetic induction devices, encoders, etc.,...
This is a radial 2 pole circular magnet designed specifically for magnetic encoder chips. It is made of sintered neodymium-iron-boron with N35 grade performance and is suitable for standard environments....
This product is a multi pole magnetic ring with an inner diameter of 1.5mm. The material is injection molded ferrite. It adopts axial multi pole magnetization and is mainly used for DC motors. If you have a sample of similar injection molded magnetic products, please contact us for quotation....
This is a very small size rectangular block magnet with galvanized surface, 3mm length, 1.5mm width and height, with very fine tolerance, magnetized by lengthwise direction, mainly used in precision electronics, instrumentation, please contact us if you need to buy....