Ferrite Magnets
NdFeB Arc Magnets
What Are NdFeB Arc Magnets?
NdFeB arc magnets feature a curved design. They can closely match motor rotors, stators, and other cylindrical magnetic structures. Compared with standard block magnets, the curved shape follows circular surfaces more closely. It helps provide continuous magnetic field coverage and makes better use of available space. For these reasons, NdFeB arc magnets are widely used in motor applications.
Looking for a Specific Size of NdFeB Arc Magnet? TOPMAG offers NdFeB arc magnets in various sizes, grades, and magnetization directions. We also support custom arc magnets based on customer drawings, samples, or specific application requirements. If you cannot find the right specification, contact us for a customized solution.
Neodymium Arc Magnet Specifications
NdFeB arc magnets require good consistency in arc angle, radius, and thickness. Dimensional variations may affect air-gap uniformity and, in turn, motor performance. The following specifications can be used as a reference for custom selection.
Size Range:
Outer Diameter (R): Ø5 mm – Ø500 mm
Inner Diameter (r): Ø3 mm – Ø480 mm
Arc Angle (θ): 10° – 180°
Axial Length (L): 5 mm – 300 mm
Wall Thickness (R–r): 1 mm – 30 mm
Magnetization Direction：
NdFeB arc magnets can use different magnetization methods based on the magnetic circuit and application requirements.
Radial Magnetization:
The magnetic poles are distributed on the inner and outer arc surfaces. The magnetic field follows the radial direction. This is one of the most common magnetization methods for motor rotors.
Parallel Magnetization:
The entire magnet is magnetized in one fixed direction. It is commonly used in surface-mounted permanent magnet motors.
Circumferential Magnetization:
The magnetic poles are distributed along the circumferential direction. It can be used for specific rotating magnetic circuit designs.
For customers with other special magnetization requirements, TOPMAG can also provide customized development based on the specific application.
Dimensional Tolerance：
Custom NdFeB arc magnets are normally manufactured according to the dimensional tolerances specified by the customer. If no specific tolerance is provided, our engineering team will evaluate the application and recommend a suitable tolerance level.
The following table provides reference tolerances for different precision levels:
| Tolerance Level | Manufacturing Process | R / r / L Tolerance | Arc Angle Tolerance | Typical Applications |
|---|---|---|---|---|
| Standard Tolerance | Conventional Machining | ±0.05 mm – ±0.10 mm | ±0.2° – ±0.3° | General assembly applications |
| Precision Tolerance | Precision Grinding | ±0.01 mm – ±0.03 mm | ±0.05° – ±0.1° | High-precision motors requiring consistent air gaps |
Applications of Neodymium Arc Magnets
Permanent Magnet Motors: Widely used in BLDC motors, PMSM motors, servo motors, traction motors, and other permanent magnet motors. The curved shape fits well with the circular structure of motor rotors.
Generators: Used in permanent magnet generators and wind turbines to provide a stable magnetic field for the rotor.
Magnetic Couplings: Used in non-contact transmission systems. The curved design helps create a compact magnetic pole arrangement and match circular structures.
Magnetic Bearings: Used in high-speed rotating and precision equipment. The curved shape can be designed to match the component structure and provide stable magnetic support.
Automation and Robotics: Used in servo systems, actuators, robots, and other automation equipment. They are suitable for applications that require high magnetic performance and compact installation space.
Other Types of Arc Magnets
In addition to NdFeB arc magnets, TOPMAG also supplies arc magnets made from other magnetic materials. These options meet different performance and cost requirements.
• Ferrite Arc Magnets——Ferrite arc magnets are an economical option with good corrosion resistance. They are widely used in traditional DC motors and general applications that do not require extremely high magnetic performance.
• SmCo Arc Magnets——SmCo arc magnets offer excellent high-temperature resistance and strong resistance to demagnetization. They are suitable for motor applications in demanding high-temperature environments, including aerospace applications.
• Alnico Arc Magnets——Alnico arc magnets offer excellent temperature stability. Their magnetic performance is lower than that of NdFeB magnets. However, they are suitable for applications such as instrumentation that require stable magnetic performance across a wide temperature range.
Frequently Asked Questions (FAQ)
Is a larger arc magnet always stronger?
Not necessarily. Magnetic strength also depends on the magnet grade, magnetization direction, air gap, magnetic circuit, and pole arrangement.
Can NdFeB arc magnets use different magnetic pole arrangements?
Yes. Different N/S pole arrangements and multi-pole magnetization can be designed for specific magnetic circuit requirements.
Can TOPMAG provide samples before mass production?
Yes. Samples can be produced for testing based on confirmed technical requirements before mass production.
How many arc magnets are needed to form a complete rotor magnetic ring?
It depends on the motor poles, rotor size, arc angle, and segmentation design. The exact number should be determined by the motor and magnetic circuit design.
What are the advantages of arc magnets compared with ring magnets?
Arc magnets are well suited to circular magnetic circuits such as motor rotors. Segmentation also allows flexible pole and magnetization designs and can help reduce eddy current losses in AC magnetic fields.
