ROTATING ELECTRIC MACHINE WITH REDUCED COGGING

• US 3,860,843 A
• Filed: 03/22/1973
• Issued: 01/14/1975
• Est. Priority Date: 06/26/1970
• Status: Expired due to Term

• Current Assignee: Itaru Kawasaki, Kazutsugu Kobayashi, Yoshiaki Igarashi
• Original Assignee: Itaru Kawasaki, Kazutsugu Kobayashi, Yoshiaki Igarashi
• Inventors: Kawasaki, Itaru, Kobayashi, Kazutsugu, Igarashi, Yoshiaki
• Primary Examiner(s): Duggan, Donovan F.
• Application Number:
  US05/343,673
• Time in Patent Office: 663 Days
• Field of Search: 320/67,156,254-259,269,192,193,190
• US Class Current: 310/67.00R
• CPC Class Codes: H02K 21/22 with magnets rotating around the armatures, e.g. flywheel magnetos

Abstract

A rotating electric machine of the multipole type which has a permanent magnet rotor magnetized in such a way that the number of stator salient poles is less than the number of permanent magnet poles. The machine has a smaller cogging force and is easily manufactured. The cogging force is made smaller by shaping both sides of the periphery of each stator salient pole. The ratio of the number of the stator salient poles to the rotor permanent magnet poles is such as to make the rotation of the rotor smooth in spite of variations in the magnetization of the permanent magnet rotor poles.

Claims

1. A rotating electric machine comprising a rotor having a permanent magnet with a plurality of poles therearound, a stator core having a plurality of salient poles therearound, and a plurality of stator coils, each of which is wound on each of said salient poles and connected to each other so as to form a stator winding having a plurality of phases, wherein said stator winding has (2n+1) phases, and said permanent magnet having a number of poles in a ratio of (2n +2)/(2n+ 1) to the number of said salient poles, and each of said stator salient poles belonging to one phase being magnetically positioned at the same position as that of the corresponding pole of said rotor.

2. A rotating electric machine as defined in claim 1, wherein said stator winding has 3 phases, and said permanent magnet has a number of poles in a ratio of 4/3 to the number of said salient poles.

3. A rotating electric machine as defined in claim 2, wherein each of said salient poles faces said permanent magnet and has the pole face shaped such that the gap between each salient pole and said permanent magnet is larger at the sides of said salient pole than at the center thereof so that the cogging force decreases for harmonic components higher than a number of cycles per revolution of the rotor equal to the number of salient poles.

4. A rotating electric machine as defined in claim 1, wherein each of said salient poles faces said permanent magnet and has the pole face shaped such that the gap between each salient pole and said permanent magnet is larger at the sides of said salient pole than at the center thereof so that the cogging force decreases for harmonic components higher than a number of cycles per revolution of the rotor Equal to the number of salient poles.

5. A rotating electric machine comprising a rotor having a permanent magnet with a plurality of poles therearound, a stator core having a plurality of salient poles therearound, and a plurality of stator coils, each of which is wound on each of said salient poles and which are connected to each other so as to form a stator winding having a plurality of phases, wherein said stator winding has 2n phases, and said permanent magnet has a number of poles in a ratio of (n+1)/n to the number of said salient poles, and each of said stator salient poles belonging to one phase being magnetically positioned at the same position as that of the corresponding pole of said rotor.

6. A rotating electric machine comprising a rotor having a permanent magnet with a plurality of poles therearound, a stator core having a plurality of salient poles therearound, and a plurality of stator coils, each of which is wound on each of said salient poles and which are connected to each other so as to form a stator winding having a plurality of phases, the number of said salient poles being a multiple of the number of phases and less than the number of said permanent magnet poles, wherein each of said salient poles faces said permanent magnet and has the pole face shaped such that the gap between each salient pole and said permanent magnet is larger at the sides of said pole than at the center thereof, so that the cogging force decreases for harmonic components higher than a number of cycles per revolution of the rotor equal to the number of salient poles.

7. A rotating electric machine as defined in claim 5, wherein each of said salient poles faces said permanent magnet and has the pole face shaped such that the gap between each salient pole and said permanent magnet is larger at the sides of said salient pole than at the center thereof so that the cogging force decreases for harmonic components higher than a number of cycles per revolution of the rotor equal to the number of salient poles.