Electric motor with speed sensor

摘要

A motor has a cylindrical rotor 1 of permanent magnet material. The inner surface of the rotor presents a plurality of poles 1A which magnetically coact with stator windings on a radially inner core 4 to produce a motor driving force. The outer cylindrical surface of the rotor has a plurality of poles 1B greater in number than those on the inner surface. The poles 1B induce a speed signal in a sensor coil 5 mounted on a part 6A, 6B of the stator which encircles the rotor 1.