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Arc & Wedge Magnets
Electromechanical Motor & Rotor Segments
Neodymium Arc & Wedge Magnets (Motor & Rotor Segments)
Engineered specifically for high-efficiency rotating electromechanical machinery, our sintered neodymium arc and wedge magnets (NdFeB) provide precision magnetic geometries for electric motors, alternators, and frictionless drives. This collection includes both concentric curved arc segments (available in paired Inner Diameter North [ID-N] and Inner Diameter South [ID-S] configurations for radial-flux cylindrical rotors) and planar trapezoidal wedge magnets (engineered for axial-flux pancake motors, flat circular arrays, and magnetic couplings).
Building a non-contact rotational system or need alternative geometries? For complete non-contact levitation, view our turnkey Magnetic Bearings. For seamless 360° annular rings with a center bore, browse Neodymium Ring Magnets. For flat rectangular plates and tiles, see our Neodymium Block Magnets.
Explore Related Motor Components, Geometries & High-Temp Alloys:
Curved Arc Segments
Ground to matching inner and outer radii for minimal stator air gaps in cylindrical BLDC motors.
Trapezoidal Wedges
Tapered keystone profiles for flat side-by-side tiling on axial-flux pancake rotor plates.
High-Temp SH & UH Formulations
Coercivity grades (N42SH, N38UH) rated for continuous motor operation up to 150°C–180°C.
Precision Grinding (±0.05 mm)
Strict tolerances across draft angles, radii, and thickness with triple Ni-Cu-Ni plating.
Filter Motor & Rotational Categories: Arc & Wedge Magnets Magnetic Bearings SmCo Magnets Ring Magnets Block & Bar Magnets
Engineering Guide: Selecting Arc vs. Wedge Magnets for Motor Design
Selecting between arc segments and wedge magnets depends directly on the electromagnetic architecture of your rotating machinery. Both geometries eliminate the inefficient air gaps created by square blocks when assembling circular arrays, but each serves a distinct motor topology:
Comparison: Arc Segments vs. Trapezoidal Wedge Magnets
| Feature | Neodymium Arc Segments | Neodymium Wedge Magnets |
|---|---|---|
| Face Geometry | Concentric curved inner and outer radii (IR / OR) | Flat planar top and bottom faces |
| Side Profile | Radial edges aligned to rotor center axis | Tapered non-parallel sides (keystone / trapezoid) |
| Primary Magnetic Flux Path | Radial flux (emanating outward/inward through curve) | Axial flux (emanating perpendicular to flat thickness) |
| Primary Motor Topology | Radial-flux BLDC motors, servomotors, cylindrical rotors/stators | Axial-flux pancake motors, wind disc generators, Halbach arrays |
| Polarity Options | Inner Diameter North (ID-N) & Inner Diameter South (ID-S) | Through thickness (North on top face, South on bottom face) |
Thermal Grades & Demagnetization Resistance
Electric motor windings generate high localized heat during continuous duty cycles and acceleration bursts. Standard N35–N52 grades can suffer irreversible demagnetization if temperatures exceed 80°C (176°F). For enclosed motor housings and drive spindles, CMS Magnetics provides specialized high-coercivity formulations:
- SH Series (e.g., N42SH): Rated for continuous operation up to 150°C (302°F) with intrinsic coercivity (Hci ≥ 20 kOe). The baseline standard for industrial servo motors, EV drivetrains, and automation equipment.
- UH Series (e.g., N38UH): Rated up to 180°C (356°F) with intrinsic coercivity (Hci ≥ 25 kOe). Engineered for compact, high-RPM motors subject to severe thermal loading.
- Extreme Temperatures (>200°C): For downhole oilfield exploration tools, aerospace actuators, and high-heat pumps exceeding 200°C, explore our high-stability Samarium Cobalt (SmCo) Magnets, rated up to 350°C.
Assembly & Mechanical Retention Best Practices
- Rotor Adhesive Bonding: Surface-mounted permanent magnet (SPM) rotors experience severe centrifugal shear stress. High-temperature structural acrylic adhesives (such as Loctite AA 324 paired with SF 7387 or SF 7075 activator) or toughened two-part epoxies provide optimal holding strength. Mixing 75-micron glass spacer beads ensures a consistent 3-to-4 mil bondline.
- Mechanical Sleeving on High-RPM Rotors: For rotational speeds exceeding 10,000 RPM, adhesive bonding should be supplemented with non-magnetic retaining sleeves—such as carbon-fiber wraps, titanium rings, or 316 stainless steel cans—to counter extreme centrifugal hoop stress.
- Turnkey Non-Contact Bearings: If your project requires pre-engineered passive levitation or journal bearing stacks, review our complete Magnetic Bearing Assemblies.
Frequently Asked Questions
How do I order a complete 360-degree motor rotor ring using arc segments?
Divide 360° by the arc angle of the segment (e.g., four 90° segments form a full 360° circle). To configure alternating magnetic poles (N-S-N-S) around the rotor circumference, order equal quantities of Inner Diameter North (ID-N) and Inner Diameter South (ID-S) segments (e.g., 2 ID-N and 2 ID-S for a 4-pole rotor).
When should I use a wedge magnet instead of an arc segment?
Use wedge magnets when designing axial-flux motors, pancake alternators, or flat disc couplings where magnetic flux travels parallel to the shaft through flat rotor plates. Use arc segments when mounting magnets to cylindrical rotors or stators where magnetic flux travels radially across a curved air gap.
Why is N42SH commonly preferred over N52 for motor applications?
Standard N52 begins to permanently demagnetize above 80°C (176°F). The N42SH grade incorporates heavy rare-earth stabilizers that raise the temperature threshold to 150°C (302°F), preserving rated motor torque and back-EMF stability under continuous operational heat.
Can CMS Magnetics manufacture custom arc radii, draft angles, or skewed edges?
Yes. We manufacture custom OEM arc and wedge runs with tailored inner/outer radii, custom draft angles, skewed edge profiles to eliminate cogging torque, and high-coercivity UH/EH alloys for custom automotive and aerospace projects.