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Permanent Magnet Step Motor Having Reduced Eddy Currents

IP.com Disclosure Number: IPCOM000039520D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Krimm, DL: AUTHOR

Abstract

Can halves of a permanent magnetic step motor are modified to interrupt the loop current paths, which are the primary eddy current flow paths, to substantially decrease the primary eddy currents. This enables an increased output torque at high speed without affecting low speed performance. A permanent magnet step motor 1 (Fig. 1), which is a conventional four-phase claw-type permanent magnet step motor, includes a mounting plate 2, a permanent magnet 3, and a rear bearing plate 4. The step motor 1 has can halves 5 and 6 cooperating with each other with annular-shaped copper windings 7 therebetween. The step motor 1 has can halves 8 and 9 with annular-shaped copper windings 10 therebetween. (Image Omitted) The current flow through each of the windings 7 and 10 is circular.

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Permanent Magnet Step Motor Having Reduced Eddy Currents

Can halves of a permanent magnetic step motor are modified to interrupt the loop current paths, which are the primary eddy current flow paths, to substantially decrease the primary eddy currents. This enables an increased output torque at high speed without affecting low speed performance. A permanent magnet step motor 1 (Fig. 1), which is a conventional four-phase claw-type permanent magnet step motor, includes a mounting plate 2, a permanent magnet 3, and a rear bearing plate 4. The step motor 1 has can halves 5 and 6 cooperating with each other with annular-shaped copper windings 7 therebetween. The step motor 1 has can halves 8 and 9 with annular-shaped copper windings 10 therebetween.

(Image Omitted)

The current flow through each of the windings 7 and 10 is circular. The primary eddy currents flow parallel to the current in each of the windings 7 and 10, as shown by arrows 11 in Fig. 2. By interrupting each of the can halves 5 (Fig. 1), 6, 8 and 9 as shown in Fig. 2 of the can half 8 at 12, the primary eddy current flow path, which is indicated by the arrows 11, is interrupted. To prevent alternate flow paths for the primary eddy currents, electrical isolation, such as a plastic film, is provided between the front mounting plate 2 and the can half 5, the can half 9 and the rear bearing plate 4, and the can halves 6 and 8. Alternatively, the front mounting plate 2 and the rear bearing plate 4 could be f...