BRUSHLESS DC MOTOR

摘要

A brushless DC motor (58) providing higher power density and efficiency with increased tool run time. The motor (58) includes a rotor assembly (72) having a permanent magnet (74) affixed to a shaft (76). A plurality of coils (94) for producing a magnetic field are wound about the rotor (72). The coils (94) include end turns that enclose the rotor (72) such that the rotor assembly (72) is not removable. Since the windings (94) are wound with the rotor assembly (72) already enclosed, the windings (94) do not require large end coils to allow subsequent insertion of the rotor (72). The permanent magnet (74) is unmagnetized when the coils (94) are wound around the rotor assembly (72) thus the winding process is simplified by not coupling energy into the wire, which would influence the winder operation. The wound assembly is inserted into a stator stack (96) comprised of magnetic material that provides a magnetic flux return path for the magnetic flux generated by the permanent magnet (74).