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# N Phase Linear Stepper Motor Concept

IP.com Disclosure Number: IPCOM000078031D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 37K

IBM

## Related People

Chai, HD: AUTHOR [+2]

## Abstract

By properly positioning the armature poles with respect to each other one-tooth-pitch motion can be obtained in a linear stepper motor in N steps or pulses, where N>2.

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N Phase Linear Stepper Motor Concept

By properly positioning the armature poles with respect to each other one- tooth-pitch motion can be obtained in a linear stepper motor in N steps or pulses, where N>2.

In Fig. 1 the pole pieces 1, 1' are magnetically connected to form a single piece. So are pole pieces 2, 2' and 3, 3', respectively. Drive coils phi A, phi B and phi C are wound on each pole piece to provide in this example a 3-phase drive. The stator 4 is a rod with teeth T1-T4. Since the general relations for a N- phase drive are Pa = (m+1 over N)Ps where m is some positive integer for packaging considerations for the 3-phase example: Pa = (1+1 over 3)Ps = 4/3Ps where Ps is the pitch of the stator teeth and Pa the pitch of the armature pole pieces.

Motion of the armature (part with coils) to the right is accomplished by energizing the coils A, B and C with the sequence C-B-A-C, with the poles of stator 4 aligning with armature pole pieces in that order. Similarly, motion to the left is accomplished by using the sequence B-C-A-B. If the armature is fixed, and the stator 4 is to move, the sequence C-B-A-C will give motion of the stator 4 to the left.

Fig. 2 shows an arrangement for moving 1 pitch (Ps) in 5 steps with a sequence B-C-D-A-B.

One immediate application of this concept is in linear stepper motors. Currently, four phases are used, requiring a multiple of four drive coils and poles. By using N=3 only a multiple of 3 drive coils and poles is required, r...