01 — Overview
About Arc Segment Magnets
Arc segment magnets are the traditional architecture for permanent-magnet motor rotors, assembled by bonding individual arc-shaped magnets around a rotor or housing. Lower tooling cost and flexibility in pole count changes make this architecture well-suited to industrial BLDC motors, stepper motors, magnetic couplings, and wind turbine generators.
Where torque smoothness is not the dominant design requirement, segmented arcs offer a cost-effective and proven solution.
02 — Production Capability
What we can hold
- Arc chord length: 5–120mm
- Radial thickness: 2–15mm
- Axial length: 5–100mm
- Curvatures matched to rotor OD or stator ID
- Parallel or radial orientation available
- Full grade range including GBD-processed high-temp
- Coating options: NiCuNi, epoxy, zinc, parylene
03 — Typical Use Cases
Where Arc Segment magnets go to work
Industrial BLDC motor rotors
Stepper motor assemblies
Wind turbine permanent-magnet generators
Magnetic couplings
Large-diameter servo motors
Electric traction motors (commercial and light automotive)
04 — Dimensions & Tolerances
Typical Dimensions & Tolerances
| Parameter | Specification |
|---|---|
| Typical dimensions | Chord 5–120mm, thickness 2–15mm, axial length 5–100mm |
| Tolerances | Dimensional ±0.05mm, angular ±0.5° |
Tighter spec?
These are typical production ranges. Send your drawing with the critical surfaces called out and we will confirm what we can hold against your tolerance stack-up.
05 — Recommended Grades
Recommended Grades for Arc Segment
N42H
120°CWorkhorse high-temperature NdFeB grade for automotive motors, pumps, and industrial drives up to 120°C.
N45H
120°CHigher-flux H-series NdFeB grade for compact 120°C motor designs demanding both torque and thermal stability.
N42SH
150°CWorkhorse SH-grade NdFeB for 150°C traction motors, robotics actuators, and high-duty servo drives.
N45SH
150°CHigh-flux SH-grade NdFeB for compact, high-torque motors operating continuously up to 150°C.
N42UH
180°CHigh-performance UH-grade NdFeB for the most demanding traction and high-temperature industrial motor applications.
06 — Related Applications
Related Applications
Industrial Automation
NdFeB magnets for stepper motors, servo drives, linear actuators, magnetic couplings, and factory automation equipment across European and North American manufacturing.
Wind Turbines
High-performance NdFeB magnet blocks and tile assemblies for permanent-magnet synchronous generators used in direct-drive and medium-speed wind turbines.
EV Motors
High-performance NdFeB magnets for electric vehicle traction motors, auxiliary drives, and e-axle systems, with the temperature stability and flux density required for continuous high-torque service.
Frequently Asked Questions
When should I use arc segment magnets instead of radial multi-pole rings?
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Arc segments are the correct choice when: tooling cost is a significant constraint (lower investment than radial ring tooling), pole count or geometry may change during development, production volumes do not justify ring tooling amortization, or torque smoothness is less critical than cost (e.g., industrial BLDC, wind generators). Radial multi-pole rings win in applications demanding low cogging torque, low vibration, and high motor efficiency.
What grade is best for arc segment magnets in wind turbines?
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Direct-drive wind turbine generators typically use N42SH or N45SH for onshore applications and N42UH or N45UH for offshore and premium designs. The SH and UH coercivity is required for the 100–130°C generator operating temperature with the 20–30 year service life horizon. Epoxy-over-NiCuNi coating is standard for corrosion protection.
Can you produce custom arc curvatures?
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Yes — arc segments are typically manufactured to match a specific rotor outer diameter or stator inner diameter, which dictates the curvature. Send us your rotor OD or stator ID along with the pole count and we will produce arc segments with matched curvature. Standard tooling covers common diameters; custom tooling is available for volumes above approximately 5,000 pieces.
Next step
Request a Quote for Arc Segment Magnets
Share dimensions, quantity, grade, and target application. Our engineering team responds within 1 business day with a grade recommendation, followed by pricing and lead time within 2 business days.