US Patent 10141803 System and apparatus for axial field rotary energy device

An axial field rotary energy device can include a rotor having an axis of rotation and a magnet; a stator coaxial with the rotor, the stator can have a printed circuit board (PCB) having a plurality of PCB layers that are spaced apart in an axial direction, each PCB layer can include a coil having only two terminals for electrical connections, each coil is continuous and uninterrupted between its only two terminals, each coil consists of a single electrical phase, and one of the two terminals of each coil is electrically coupled to another coil with a via to define a coil pair; and each coil pair is electrically coupled to another coil pair with another via.