Neodymium Magnets for Drones & UAV Motors

It depends on how hot the bell gets, not on Br alone. For most consumer and FPV outrunners running to about 120°C, N45H or N48H is the standard choice — both give Hcj ≥ 1353 kA/m with useful remanence. N48H buys a little more thrust density than N45H at the same temperature rating. For heavy-lift or agricultural drones whose bell reaches 150°C under load, step up to N50SH (Hcj ≥ 1592 kA/m). Plain N52 is a high-Br, low-coercivity grade rated to only 80°C — it demagnetizes in a hot drone motor, so it is rarely the right call for propulsion. Send us your measured or estimated bell temperature and we will confirm the grade.

A standard N-grade magnet has a maximum operating temperature of about 80°C. A drone outrunner traps heat inside a small, closed bell, and during a sustained hover or a loaded climb that bell routinely climbs past 80°C. Once a magnet exceeds its knee-point temperature, it partially and permanently demagnetizes — you lose thrust, the ESC draws more current to hold RPM, and the motor runs even hotter. H grade (120°C) and SH grade (150°C) raise the knee point above the temperature the motor actually reaches, so the magnet stays stable across the full flight envelope.

GBD diffuses heavy rare earths (dysprosium and terbium) along the grain boundaries of the magnet rather than mixing them throughout the whole volume. Because coercivity is set at the grain boundaries, you get the same knee-point temperature using up to 70% less Dy/Tb than conventional sintering. For a UAV that matters two ways: less dense heavy rare earth means a marginally lighter rotor, and far less Dy/Tb means lower cost and lower exposure to rare-earth export-control shocks. Mainrich applies GBD as a standard process on every H and SH grade — not a premium upgrade. See our GBD process page.

Roughly 95% of drone propulsion motors are outrunners, where curved arc (tile) magnets are bonded around the inner wall of a rotating bell. These need thin, wide arcs ground to the bell's inner radius, in high pole counts, magnetized radially. Inrunners — used in electric ducted fans and some fixed-wing propulsion — put a ring or bonded segment magnet on a central spinning rotor at much higher RPM, often inside a retaining sleeve. For an outrunner, send us bell inner diameter, magnet thickness, arc length or pole count, and magnetization direction. For an inrunner, send rotor OD, sleeve ID, and length.

It follows the pole count. Most drone outrunners use a 12N14P configuration — 12 stator teeth and 14 rotor poles — so the bell holds 14 arc magnets, or 28 when each pole is split into two segments to cut eddy-current loss. Compact FPV motors may run 12 poles; large low-KV motors for heavy-lift and delivery drones can run 20 or more. Because the magnets are supplied as a matched set for one motor, we quote and inspect per set — send us your pole count or a sample motor and we will confirm the arc dimensions and quantity.

For dry consumer and FPV motors, standard Ni-Cu-Ni triple-layer plating is enough — it resists handling and normal humidity. For agricultural spray drones, which operate in a constant mist of water and agrochemicals, and for marine or coastal UAVs exposed to salt, we recommend an epoxy coating (often over Ni-Cu-Ni) for its chemical and moisture resistance. Because the magnets are bonded inside a bell, adhesive compatibility matters too — tell us your bonding system and environment and we will match the coating.

Yes. In high-KV outrunners and high-pole PMSM drone motors, changing flux induces eddy currents in solid magnets, which show up as rotor heating and lost efficiency — and added heat pushes the magnet toward its knee point. Segmenting the magnet breaks up those current loops. Mainrich supplies segmented arcs with epoxy inter-layer insulation ≤ 30 μm, typically 2–8 segments per pole depending on your KV and pole geometry. Send your operating RPM and pole configuration and we will propose a segmentation scheme.

Since the 2025 dual-use control framework, magnets containing dysprosium or terbium fall under China's rare-earth export licensing. For a compliant import you will generally need an end-use / end-user statement, a country-of-origin certificate, and the export license itself. Mainrich sources Dy/Tb only through MIIT-licensed channels and prepares this paperwork on a case-by-case basis — typically 2–4 weeks once your documentation is complete. Our GBD process also reduces the Dy/Tb intensity of each magnet, which helps. See our guide to China's 2025 export controls for the full document list.