Step Motors With High Cogging Torque
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
A polyphase rotary step motor has a permanent magnet rotor and stator poles having single or bifilar windings. Fig. 1 shows a three-phase step motor 10 with permanent magnet rotor 11. Stator 12 has poles I, II, and III wound with single windings A, B, and C. For clockwise rotation, the pulsing sequence is B-A-C-B where the current direction produces south polarity. An initial motion can be enhanced by pulsing both A and B windings to start the motion where winding B is pulsed to produce a south polarity in pole II and winding A is pulsed to produce a north polarity in pole I. Fig. 2 shows a three-phase step motor 13 having a rotor 14 with a square core 15 made of soft iron coupled between permanent magnet poles 16 and 17.