Reluctance electric machine having a decreased cross section of rotor ferromagnetic material

• US 4,888,513 A
• Filed: 04/19/1988
• Issued: 12/19/1989
• Est. Priority Date: 04/30/1987
• Status: Expired due to Term

• Current Assignee: Antonino Fratta
• Original Assignee: Antonino Fratta
• Inventors: Fratta, Antonino
• Primary Examiner(s): Salce, Patrick R.
• Assistant Examiner(s): Rebsch, D. L.
• Application Number:
  US07/186,091
• Time in Patent Office: 609 Days
• Field of Search: 310/216, 310/261, 310/269, 310/166, 310/168, 310/217, 310/256, 310/269, 310/42
• US Class Current: 310/216.017
• CPC Class Codes: H02K 1/246 Variable reluctance rotors
• CPC Class Codes: H02K 29/06 with position sensing devices H02K29/03 takes precedence
• CPC Class Codes: H02P 25/08 Reluctance motors

Abstract

A reluctance electric machine which comprises a stator with electric windings, a rotor including ferromagnetic material members, inserted into the stator and separted therefrom by an air gap, and members of non-ferromagnetic material inserted in the rotor in such a way that the cross section of the ferromagnetic material members of the rotor, at least near the air gap, is decreased by the insertion of the members of non-ferromagnetic material in such a way that the ratio between the ferromagnetic material cross section and the whole cross section available does not exceed 0.6, and the ratio between at least one linear dimension of the non-ferromagnetic material members, lying in a plane tangent to the air gap, and the thickness of the machine air gap, does not exceed 5. The electric machine is fed by an electronic circuit for vectorial control (in amplitude and phase) of the current feeding the electric windings of the stator. The rotor may be massive with salient poles, and then the members of non-ferromagnetic material are little cavities hollowed in the surfaces of the rotor which face the air gap. Alternatively, the rotor may have axial laminations, and then the laminations comprise ferromagnetic sheets and alternate non-ferromagnetic intercalary layers, where the thickness of each intercalary layer is at least 2/3 of thickness of each ferromagnetic sheet, and the thickness of each intercalary layer does not exceed 5 times the thickness of the machine air gap.

Claims

1. A reluctance electric machine comprising

(a) a stator having electric windings;

and

(b) a rotor having spaced poles and being inserted into said stator and spaced therefrom by an air gap, said rotor including axial laminations comprising

(1) ferromagnetic sheets; and

(2) non-ferromagnetic intercalary layers alternating with said ferromagnetic sheets in such a way that the cross section of said ferromagnetic sheets of said rotor at least in the vicinity of said air gap is decreased by said non-ferromagnetic intercalary layers, the ratio between the cross section of said ferromagnetic sheets and the cross section available for magnetic flux lines not exceeding 0.6, the thickness of each of said intercalary layers being at least 2/3 of the thickness of each of said ferromagnetic sheets, and the thickness of each of said intercalary layers not exceeding 5 times the thickness of said air gap.

2. A reluctance electric machine comprising

(a) a stator having electric windings;

and

(b) a rotor having spaced poles and being inserted into said stator and spaced therefrom by an air gap, said rotor including

(1) axial laminations comprising

(i) ferromagnetic sheets; and

(ii) non-ferromagnetic intercalary layers alternating with said ferromagnetic sheets in such a way that the cross section of said ferromagnetic sheets of said rotor at least in the vicinity of said air gap is decreased by said non-ferromagnetic intercalary layers, the ratio between the cross section of said ferromagnetic sheets and the cross section available for magnetic flux lines not exceeding 0.6, the thickness of each of said intercalary layers being at least 2/3 of the thickness of each of said ferromagnetic sheets, and the thickness of each of said intercalary layers not exceeding 5 times the thickness of said air gap;

(c) a shaft of ferromagnetic material, said shaft having a plurality of radial projections in the shape of arms supporting said laminations; and

(d) members of non-ferromagnetic material arranged in the spaces between said poles.

3. An electric machine as set forth in claim 2, wherein said rotor has 2n poles, said shaft has 2n projections in the shape of supporting arms, and said projections and the laminations each have, in section, a central portion curved substantially through 1/n of an angle of 180°

, and lateral portions projecting from said central portion, said lateral portions being substantially straight and being nearly parallel to the direct axes of the rotor.

4. An electric machine as set forth in claim 2, wherein said rotor has 2n poles, said shaft has 2n projections in the shape of supporting arms, and said projections and the laminations each have, in section, a central portion of substantially polygonal shape and lateral portions projecting from said central portion, said lateral portions being substantially straight and being nearly parallel to the direct axes of the rotor.

5. An electric machine as set forth in claim 2, wherein said rotor has 2n poles, said shaft has 2n projections forming a star-shaped figure having 2n supporting arms, and each lamination has the shape of a dihedron whose vertex, in section, is located on a quadrature axis and whose sides are oriented towards the direct axes of the rotor.

6. An electric machine as set forth in claim 2, wherein each rotor pole has a length, expressed in terms of electric angle, of at least 2 radians.