Product Descriptions
In modern permanent magnet motor design, the geometry of the rotor magnet directly impacts torque ripple, cogging, and overall efficiency. Our Permanent Motor Segment Magnet – available in arc (segmented) or bread‑loaf profiles – is engineered to deliver optimal magnetic flux distribution across the air gap, enabling smoother operation and higher power density in BLDC (Brushless DC), PMSM (Permanent Magnet Synchronous Motor), and servo motor applications. These sintered neodymium‑iron‑boron (NdFeB) segments are manufactured from 100% virgin rare‑earth materials (purity ≥95%) in our vertically integrated, IATF 16949‑certified facility. Key parameters – including arc inner/outer radius, chord height, and thickness – are precision ground to tolerances as tight as ±0.03 mm, ensuring consistent gap spacing when assembled into rotor cores. We offer grades from N35 to N52, as well as high‑temperature series N38UH, N40UH, and N42SH (operating up to 180°C or 200°C). Standard Ni‑Cu‑Ni triple plating provides corrosion resistance, while epoxy or Parylene coatings are available for electrical insulation in high‑voltage systems. For each production batch, we supply full magnetic test reports, dimensional certificates, and material traceability.
Why Precision Segments Matter for Motor Performance
Optimized Flux Distribution
The arc or bread‑loaf shape concentrates magnetic flux where it is needed most – across the air gap. This reduces leakage and improves torque production, allowing smaller motors to achieve higher power output.
Tight Dimensional Control
Our CNC grinding and wire EDM processes hold arc radius, chord height, and thickness to ±0.02‑0.03 mm. Consistent segment geometry ensures uniform air gap and low cogging torque across all poles.
High‑Temperature Capability
For EV traction motors and industrial servos, we offer UH (180°C) and EH (200°C) grades with dysprosium addition. These maintain coercivity and resist demagnetization under high thermal stress.
Technical Specifications – Motor Segment Magnets
Below are typical magnetic properties and common segment geometries for permanent motor segment magnets. Custom arc angles, radii, and lengths are available based on your rotor design.
| Grade | Br (T) | Hcj (kA/m) | BHmax (kJ/m³) | Max Temp (°C) | Typical Application |
|---|---|---|---|---|---|
| N42SH | 1.30-1.32 | ≥1590 | 318-334 | 150 | Industrial servo motors |
| N40UH | 1.25-1.29 | ≥1990 | 302-326 | 180 | EV traction motors |
| N38EH | 1.22-1.26 | ≥2388 | 287-310 | 200 | High‑performance automotive |
| N48 | 1.38-1.42 | ≥955 | 366-382 | 80 | Appliance motors, fans |
| N52 | 1.43-1.48 | ≥876 | 398-414 | 70 | Compact high‑torque motors |
*Standard segment dimensions: arc angle 60°, 72°, 90°, 120°; inner radius 15‑150 mm; thickness 3‑20 mm; length 10‑150 mm. Custom designs welcome.
Magnetic direction
Coating / Plating
Neodymium permanent arc magnets primarily consist of neodymium, iron, and boron. The iron content makes them susceptible to oxidation when exposed to atmospheric conditions. To ensure long-term durability, all our high-strength magnets receive micron-thin protective coatings that preserve both magnetic properties and adhesive performance. Multiple surface treatment options are available, with triple-layer nickel plating (Ni-Cu-Ni) being the most prevalent. Additional coatings include zinc, copper, epoxy, gold, silver, passivation treatments, and PVC encapsulation for specialized applications.
High-Precision Manufacturing
With precision grinding and cutting, tolerances of +/-0.05mm can be achieved during the manufacturing process.
Magnetic Grade Parameters
Manufacturing Excellence – Full Process Control for Motor Magnets
Producing consistent arc segments requires specialized processes. Our factory begins with vacuum induction melting of virgin rare earths (dysprosium or terbium added for high‑temp grades). After jet milling, the powder is pressed in a segmented die under a magnetic field to achieve radial or parallel orientation as specified. Sintering and multi‑stage heat treatment optimize the microstructure for high coercivity. Segments are then ground on all critical surfaces: inner radius, outer radius, and end faces using dedicated rotary grinding machines. Standard Ni‑Cu‑Ni plating (13‑18 μm) is applied in automated barrels. Every batch of permanent motor segment magnets is tested for magnetic flux (Helmholtz coil or Gauss meter), dimensional accuracy (CMM or optical comparator), and coating thickness (XRF). We also perform high‑temperature demagnetization tests on samples. All shipments include full test certificates with material traceability. Our IATF 16949 and ISO 9001 systems ensure compliance with automotive and industrial OEM requirements.
FAQ
Q: Why is ferrite often used instead of NdFeB for motor segment magnets despite NdFeB's higher energy product?
A: Ferrite offers better thermal stability and demagnetization resistance at high temperatures (e.g., in compressors). Its high resistivity reduces eddy losses in high‑frequency motors. NdFeB is only preferred when extremely high power density is required (e.g., EV traction motors).
Q: How does a segmented pole structure affect cogging torque harmonics?
A: Splitting one arc magnet into multiple segments with small angular offsets creates a phase‑shift effect. For example, three segments offset by 0.5 slot pitch cancel the 3rd, 6th, 9th… cogging torque harmonics, significantly reducing total torque ripple without requiring rotor skewing.
Q: How is radial orientation achieved in sintered NdFeB segment magnets?
A: Radial orientation requires radial‑field pressing: a die with arc‑shaped pole heads generates magnetic flux radiating from the center. The easy axis becomes perpendicular to the arc surface. This enables energy products above 35 MGOe but yield is low (60‑70%) and cost is 2‑3 times higher than parallel orientation.
Q: Are samples available?
A: Complimentary samples are available from inventory. Customers are responsible only for shipping costs.
Q: What are the failure risks of carbon‑fiber vs. metallic sleeves for high‑speed (>30,000 rpm) segment magnets?
A: Carbon‑fiber: low eddy loss but radial clamping force drops at high temperature, causing fretting wear and loosening. Metallic (Ti/Inconel): stable preload but eddy currents raise magnet temperature by 15‑30°C, risking demagnetization. Hybrid sleeve (carbon‑fiber + glass pins) is preferred.
Q: What applications are suitable?
A: Electric motors, magnetic couplings, robotics, renewable energy systems, medical devices, and industrial machinery.
Q: How do you ensure quality?
A: Our products undergo strict quality control, and we provide test documentation. We hold certifications like ISO9001, IATF16949, RoHS, and REACH.