A brushless DC motor has no commutator or brushes. Its stator carries copper windings and its rotor carries permanent magnets, and an electronic controller switches current between the phases. Making one reliably comes down to a handful of process steps.
1. Stator preparation
The stator core arrives as a stack of steel laminations. Its slots are insulated, either with slot liner paper or with an epoxy powder coating, so the copper wire never touches bare steel.
2. Winding
Enamelled copper wire is wound around each tooth. Outer-rotor stators such as ceiling fan motors are usually needle wound; segmented stators and bobbins suit flyer winding. Turn count, wire tension and coil position decide resistance balance between phases.
3. Lead termination and insulation
Phase leads are stripped, tinned, soldered or crimped. Wedges, lacing and varnish or resin impregnation hold the winding in place.
4. Winding test
Before the stator goes further, it is checked for resistance, insulation, hipot and turn-to-turn faults with a surge test.
5. Rotor production
Magnets are inserted or bonded, the shaft and bearings are pressed, the rotor is balanced and then magnetized.
6. Final assembly, electronics and testing
Stator and rotor are brought together, covers are fitted, the controller board is connected and the finished motor is tested for current, speed, noise and sensor signals.
See the machines for each step.