Permanent magnet rotor for alternating current generators and motors

Claim 2

An alternating current electrical machine comprising a stator having an inner periphery with slots containing conductors of a distributed winding, and a rotor mounted to rotate with its outer periphery adjacent to the inner periphery of the stator, the rotor comprising a plurality of permanent magnets, spaced apart along the axis of rotation of the rotor with their magnetic axes coincident with the said axis and, with their directions of magnetization parallel to the said axis, a plurality of pole shoes spaced apart around the rotor periphery and extending substantially continuously for at least three quarters of the whole axial length of the rotor periphery, and a plurality of flux guides arranged to couple the poles of the permanent magnets to the pole shoes magnetically to give the pole shoes polarities which alternate around the rotor periphery but which are the same in the axial direction of the rotor over more than half the length of the outer periphery of the rotor, the flux guides and the pole shoes being arranged to ensure that the flux density at the pole shoes is high compared with that at the permanent magnet means.

Claim 3

A machine according to claim 1 wherein the conductors of the stator winding extend substantially the whole axial length of the outer rotor periphery.

Claim 4

A machine according to claim 2 wherein at least half the pole shoes extend for substantially the whole axial length of the outer rotor periphery.

Claim 5

A machine according to claim 3 wherein the stator winding is wound to provide a number of poles equal to the number of pole shoes of the rotor.

Claim 6

A machine according to claim 4 wherein the permanent magnets have like poles adjacent but separated by radial elements of the flux guides, the elements extending in a radial direction with respect to the said axis, radial elements of the guides also being positioned at the outer ends of the outer magnetic means in the rotor, and the pole shoes being elongated, with their axes generally parallel to the said axis and with each pole shoe magnetically coupled to at least one element.

Claim 7

A machine according to claim 5 wherein alternate pole shoes extend only part of the way along the rotor periphery in the axial direction and auxiliary pole shoes occupy positions in the rotor periphery which are generally axially aligned with the said alternate pole shoes, the auxiliary pole shoes being supported by one of the elements which also support the adjacent full length pole shoes and the auxiliary pole shoes and the elements supporting those shoes being of a material which would allow the rotor to start rotation by induction motor action if the stator winding were coupled to an appropriate alternating current source.

Claim 8

A machine according to claim 5 wherein the pole shoes connect substantially axially aligned pole parts.

Claim 9

A machine according to claim 5 wherein the magnets include at least one material of the group consisting of barium ferrite, strontium ferrite, ticonal, alnico or one of the samarium cobalt materials.

Claim 10

A machine according to claim 5 wherein each permanent magnet is a generally disc shaped magnet and each flux guide includes a generally disc shaped element, made of magnetic material, with radially projecting portions supporting the pole shoes.

Claim 11

A machine according to claim 9 wherein the magnets include at least one of the following materials: barium ferrite, strontium ferrite, ticonal, alnico or one of the samarium cobalt materials.

Claim 12

A machine according to claim 10 wherein the elements and pole shoes are of steel.

Claim 13

A machine according to claim 9 with one more flux guide than disc magnet, and each disc magnet being positioned between flux guides.

Claim 14

A machine according to claim 9 wherein in each pair of adjacent pole shoes, one pole shoe is supported by alternate disc shaped elements in the axial direction and the other pole shoe is supported by the remaining disc shaped elements.

Claim 15

A machine according to claim 13 wherein the rotor has an axial shaft at least the periphery of which is made of non-magnetic material, and the magnets and the elements have central apertures through which the shaft passes.

Claim 16

A machine according to claim 1, wherein the pole shoes are elongated in the said axial direction and are skewed relative to the rotor axis.

Claim 17

A machine according to claim 1, wherein the rotor includes a portion so constructed that with an appropriate alternating current source coupled to the stator winding, the rotor will begin to rotate from rest by induction motor action.

Claim 18

A machine according to claim 1 wherein the pole shoes project in both directions parallel to the rotor axis away from at least some of the positions at which the pole shoes are coupled to flux guides situated between two permanent magnet means, and the pole shoes are integral at the said positions.

Claim 19

A permanent magnet rotor for an alternating current generator or motor, including at least two generally disc shaped axially magnetised permanent magnets each having an aperture at its centre, on each side of which magnets are generally disc shaped elements of magnetic material with central apertures and a number of radially projecting pole parts on their outer peripheries, pole shoes arranged radially on the pole parts extending substantially continuously for at least three quarters of the whole axial length of the rotor periphery over the said elements in the axial direction, and a metal hub, having at least a periphery of non-magnetic material, which passes through the apertures in the magnets and the elements, the elements being so arranged that the pole parts of elements adjacent to permanent magnet poles of the same polarity are substantially axially aligned with one another and with gaps between the pole parts of elements adjacent to permanent magnet poles of the opposite polarity and the disc shaped elements, the pole parts and the pole shoes being arranged to ensure that the flux density at the pole shoes is high compared with that at the permanent magnets.

Claim 20

A permanent magnet rotor for an alternating current generator or motor, including at least two generally disc shaped axially magnetised permanent magnets each having an aperture at its centre, on each side of which magnets are generally disc shaped elements of magnetic material with central apertures and a number of radially projecting pole parts on their outer peripheries, pole shoes arranged radially on the pole parts extending substantially continuously for at least three quarters of the whole axial length of the rotor periphery over the said elements in the axial direction, and a metal hub, having at least a periphery of non-magnetic material, which passes through the apertures in the magnets and the elements, the elements being so arranged that the pole parts of elements adjacent to permanent magnet poles of the same polarity are substantially axially aligned with one another and with gaps between the pole parts of elements adjacent to permanent magnet poles of the opposite polarity and the disc shaped elements, the pole parts and the pole shoes being arranged to ensure that the flux density at the pole shoes is high compared with that at the permanent magnets.

Claim 21

A rotor according to claim 18 wherein the pole shoes connect substantially axially aligned pole parts.