WO2016207700A1

WO2016207700A1 - An electric rotary machine having axially-spaced groups of magnet structures

Info

Publication number: WO2016207700A1
Application number: PCT/IB2015/054833
Authority: WO
Inventors: Geoffrey Kwananga MKANDAWIRE
Original assignee: Kotze, Gavin, Salomon
Priority date: 2015-06-26
Filing date: 2015-06-26
Publication date: 2016-12-29

Abstract

An electric rotary machine (100) has a stator (130) and a rotor (110) which is operable to rotate relative to the stator (130) about an axis of rotation (112a). The machine (100) has at least two groups of magnet structures (114a, 114b) which are provided on one of the rotor (110) or the stator (130) and are spaced apart relative to each other axially along the axis of rotation (112a), while conductive windings (150a) are provided on the other of the stator (130) or the rotor (110). Each group of magnet structures provides (114a, 114b), or is configured to provide, at least one eccentric magnetic pole (N or S) of one polarity only and no magnetic poles of the other polarity.

Description

An electric rotary machine having axially-spaced groups of magnet structures

FIELD OF INVENTION

[0001] This invention relates to electric rotary machines such as motors or generators. More specifically, this invention relates to electric rotary machines having axially-spaced groups of magnet structures, with each magnet structure providing a pole or poles of one polarity only.

BACKGROUND OF INVENTION

[0002] A conventional electric rotary machine of which the Applicant is aware includes a stator and a rotor which, as its name suggests, rotates about an axis of rotation relative to the stator. Such principles are well established in both motors

(happen ik-pedia.orq/vvikl/Eieciilc motor, accessed 20 April 2015) and generators (http://en.wikipedia.org/wiki/Electric generator, accessed 20 April 2015).

[0003] One of the rotor or the stator carries conductive windings while the other of the stator or the rotor carries a series of magnet (or magnet structures) with which the windings interact, either to induce motion (in the case of a motor) or to induce an electrical current (in the case of a generator). There are many and varied configurations of the windings and magnets. However, one paradigm of which the Applicant is aware is that the magnets, or at least the poles presented by the magnets, are always arranged and spaced in an alternating manner circumferentially about the axis of rotation. [0004] The Applicant accordingly desires an electric rotary machine which does not have magnetic poles spaced circumferentially around the axis of rotation.

SUMMARY OF INVENTION

[0005] Accordingly, the invention provides an electric rotary machine which has a stator and a rotor which is operable to rotate relative to the stator about an axis of rotation, characterised in that: the electric rotary machine includes at least two groups of magnet structures; the groups of magnet structures are provided on one of the rotor or the stator and are spaced apart relative to each other axially along the axis of rotation, while conductive windings are provided on the other of the stator or the rotor; and each group of magnet structures provides, or is configured to provide, at least one eccentric magnetic pole of one polarity only and no magnetic poles of the other polarity.

[0006] Each group of magnet structures may provide, or may be configured to provide, at least two circumferentially spaced magnetic poles of the same polarity only (and no magnetic poles of the other polarity). Stated differently, the magnet structures do not provide circumferentially alternating poles, (N-S-N-S... ) as is the conventional paradigm, but rather provide a plurality of the same poles (e.g., N-N... only or S-S... only) spaced circumferentially. Poles and polarities may be used interchangeably, as the context may dictate.

[0007] The phrase "each group of magnet structures... is configured to provide" includes an electromagnet. It will be appreciated that an electromagnet does not always provides magnetic poles - it only does so when it is activated. [0008] Each group of magnet structures may be disc-shaped or annular. The magnet structure may define a radially inwardly extending slot or groove between adjacent magnetic poles. The magnet structure may be constituted by a plurality of sectors, with each sector providing one magnetic pole. The sectors may be interspaced by the slots. The slots may serve to isolate adjacent magnetic poles from each other. Instead of slots, other isolating means may be provided between sectors thereby to separate or isolate adjacent poles.

[0009] In one embodiment, there may be two magnetic poles provided by the magnet structure. In such case, the magnet structure may include two semi-circular sectors of 180° each, or unequal sectors respectively of less than or more than 180°. The magnetic poles may be diametrically opposed. There may be two slots defined the magnet structure, the slots interspacing the poles.

[0010] In other embodiment, there may be more than two magnetic poles provided by the magnet structure. The poles may be equi-angularly spaced around the axis of rotation.

[0011] There may be two groups of magnet structures. In such case, one group may provide magnetic poles of north (N) polarity only, while the other may provide magnetic poles of south (S) polarity only. Adjacent magnet structures may be linked or associated with each other. Assuming a dipole magnet, the north (N) polarity may be provided by one magnet structure, while the south (S) may be provided by an adjacent magnet structure, the N and S poles being axially (or longitudinally) spaced from each other, not circumferentially spaced.

[0012] There may be more than two groups of magnet structures. In such case, the magnet structures may be arranged to provide magnetic poles of alternating polarity; that is to say, one magnet structure may provide a plurality of N poles, while the next may provide a plurality of S poles, with the next providing a plurality of N poles, and so forth. Intermediate (that is, non-end) magnet structures may be double a width or strength of the end magnet structures. For example, a magnet structure arrangement may be N-2xS-N, or S-2xN-S. There may be a plurality of N-S or S-N magnet structures spaced apart on one shaft and stator teeth being axially aligned and arranged accordingly with windings of each unit connected in series or parallel arrangement.

[0013] The rotary electric machine may be operated either as a motor or as a generator (or even as a hybrid). The rotary electric machine may be operated as a DC (Direct Current) machine, or as an AC (Alternating Current) machine, or a combination thereof. The rotary electric machine may be operated as a synchronous machine, induction machine, reluctance machine, etc.

[0014] The magnet structures may be provided by fixed magnets, e.g., permanent magnets. The magnet structures may be provided by variable magnets, e.g., electromagnets. If the magnet structures are electro-magnets, then the magnet structures may include at least two axially-spaced disc-like structures interspaced by circumferentially-extending windings which are co-axial relative to the disc-like structures.

[0015] The electric rotary machine may include a switching arrangement to switch a polarity and/or current direction of the windings. The switching arrangement may include a switching circuitry and/or a sensing arrangement. The sensing arrangement may include one or more sensors. The sensor may include a conventional sensor, such as a Hall Effect sensor.

[0016] Instead, or in addition, the sensing arrangement may include a plurality of optical receivers operable to sense presence or absence of optical markings or emissions. The sensing arrangement may include an optical mask to occlude at least some of the optical markings or emissions which will then not be sensed by the optical receivers. The optical mask may be rotary, e.g., fast with the rotor, while the optical receivers and optical markings/emissions may be stationary, e.g., fast with the stator.

BRIEF DESCRIPTION OF DRAWINGS

[0017] The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

[0018] In the drawings:

FIG. 1 shows a part-exploded three-dimensional schematic view of a first embodiment of an electric rotary machine in accordance with the invention;

FIG. 2 shows an exploded three-dimensional schematic view of the electric rotary machine of FIG. 1 ;

FIG. 3 shows a part-exploded three-dimensional schematic view of a second embodiment of an electric rotary machine in accordance with the invention;

FIG. 4 shows an exploded three-dimensional schematic view of the electric rotary machine of FIG. 1 ;

FIG. 5 shows an axial sectional schematic view of the electric rotary machine of FIG. 1 in a first plane;

FIG. 6 shows an axial sectional schematic view of the electric rotary machine of FIG. 1 in a second plane;

FIG. 7 shows an axial sectional schematic view of the electric rotary machine of FIG. 1 in a first plane;

FIG. 8 shows an axial sectional schematic view of the electric rotary machine of FIG. 1 in a second plane;

FIG. 9 shows a schematic three-dimensional view of a stator with windings of the electric rotary machine of FIG. 1 ; FIGS 10-13 show schematic views of various embodiments of different rotor/stator configurations which may be used in electric rotary machine of FIG. 1 ;

FIG. 14 shows a schematic view of a first part of a sensing arrangement for use with the electric rotary machine of FIG. 1 ;

FIG. 15 shows a schematic view of a second part of a sensing arrangement for use with the electric rotary machine of FIG. 1 ;

FIG. 16 shows a three-dimensional schematic view of part of a third embodiment of an electric rotary machine in accordance with the invention;

FIG. 17 shows a three-dimensional schematic view of part of the electric rotary machine of FIG. 16;

FIG. 18 shows a three-dimensional schematic view of part of another embodiment of an electric rotary machine in accordance with the invention;

FIGS 19-27 shows schematic circuit diagram of various switching arrangements for use with the electric rotary machine of FIG. 1 (or other FIGS);

FIG. 28 shows a schematic view of laminations used to form an electric rotary machine in accordance with the invention; FIG. 29 shows a schematic view of the laminations of FIG. 28 and other components used to create the electric rotary machine;

FIG. 30 shows a three-dimensional view of a rotor with eccentric magnet structures of the electric rotary machine of FIGS 28-29;

FIG. 31 shows a schematic view of further parts of the electric rotary machine of FIGS 28-30;

FIG. 32 shows a three-dimensional view of a rotor with eccentric magnet structures like those of FIG. 30; and

FIG. 33 shows a top view of the rotor of FIG 32. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

[0019] The following description of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that many changes can be made to the embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances, and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not a limitation thereof.

[0020] FIG. 1 shows a first embodiment of an electric rotary machine 100 in accordance with the invention. In this embodiment, a rotor 1 10 carries two magnet structures 1 14a, 1 14b (both or each referred to by numeral 1 14) while a stator 130 carries windings (not illustrated in FIG. 1 ). This embodiment of the electric rotary machine 100 is relatively simple in that the rotor has only two magnet structures 1 14 (in contrast with different embodiments which will be described below).

[0021] The rotor 1 10 has a central axle or shaft 1 12 which is mounted via a mounting arrangement (not illustrated - the mounting arrangement may be similar or identical to those in conventional electric rotary machines) to rotate about an axis of rotation 1 12a. The magnet structures 1 14 are mounted to the axle 1 12 to rotate about the axis of rotation 1 12a. The magnet structures 1 14 are interspaced by a rotor linkage piece 1 16 which is configured to space the magnet structures 1 14 a short axial distance apart. Although not illustrated, the magnet structures 1 14 comprise a plurality of layers of laminations to improve magnetic flux characteristics and minimise eddy currents in the magnet structures 1 14 (as in conventional electric rotary machines). [0022] The rotor linkage piece 1 16 may be of a similar or identical ferromagnetic material (e.g., iron) to that of the magnet structures 1 14 and serves to link the magnetic paths between the magnet structures 1 14. The rotor linkage piece 1 16 has a smaller outer diameter relative to, and therefore appears recessed relative to, the surrounding magnet structures 1 14. The rotor linkage piece 1 16 may also be constructed of laminations.

[0023] Each magnet structure 1 14 defines a pair of diametrically opposed slots 1 18 which effectively serve to separate the magnet structure 1 14 into two halves or sectors. Each half of the magnet structure 1 14 provides a pole of the same polarity as the other half of the same magnet structure 1 14. Thus, in the two magnet structures 1 14, the first magnet structure 1 14a will provide two identical poles (e.g., N) spaced circumferentially the respective slot 1 18 at each half, while the second magnet structure 1 14b will provide two poles identical to each other but opposite (e.g., S) to those of the first magnet structure 1 14a.

[0024] A dipole magnet may thus be formed between adjacent, axially aligned halves of the respective magnet structures 1 14, with one being N and the other being S. This is in stark contrast with conventional electric rotary machines (i.e., those machines not in accordance with the invention) having a plurality of circumferentially alternating magnetic poles (i.e., N-S-N-S... ). Also, conventional electric rotary machines usually only have a single ring of alternating magnetic poles, while the electric rotary machine 100 or the present invention has at least two rings (each provided by the magnet structures 1 14) with each having plural instances of only one polarity.

[0025] The rotor 1 10 in this example is composed of permanent magnets. Accordingly, the magnets structures 1 14 are fixed or permanent magnet structures. However, in an alternate embodiment (not illustrated), windings may be wound circumferentially around the rotor linkage piece 1 16, or axially wound and energised, thereby to induce opposite magnetic fields in the magnet structures 1 14 on either side. In other words, magnetic poles of only one polarity will be on one side of the windings, and magnetic poles of only the opposite polarity will be on the other side.

[0026] The stator 130 defines a central cylindrical cavity 132 to accommodate the rotor 1 10. The cavity 132 is marginally larger than the magnet structures 1 14 of the rotor to accommodate it with a small but contactless clearance. The stator is typically fixedly mounted to a non-ferrous support structure (not illustrated).

[0027] The stator 130 has a similar three-disc configuration to that of the rotor 1 10. The stator 130 comprises a pair of winding structures 134a, 134b (collectively or each referred to by numeral 134) which sandwich therebetween, and are axially spaced apart by, a stator linkage piece 136. The winding structures 134 and stator linkage piece 136 have the same outer diameter and thus present a cylindrical outer surface of constant diameter.

[0028] Each winding structure 134 includes a plurality of inwardly directed alternating grooves 138 and teeth 140 spaced circumferentially on an inner surface of the winding structure 134. Inner surfaces of the teeth 140 have common diameter smaller than the inner diameter of the stator linkage piece 136 and thus project radially inwardly relative thereto.

[0029] Each winding structure 134 is identical and aligned, and thus the grooves 138 and teeth 140 of the first winding structure 134a are axially aligned with those of the second winding structure 134b. Two aligned teeth 140 (that is, one from the first winding structure 134a and one from the second winding structure 134b) form a pair and are configured to receive a winding of conductive material (e.g., copper wire). The windings (not illustrated in FIG. 1 ) are thus wound around the pair of teeth 140 from both winding structures 134.

[0030] FIG. 2 illustrates a more fully exploded view of the electric rotary machine 100. The locations of the poles have also been illustrated in the magnet structures - l o l l 4. The first magnet structure 1 14a comprises two N poles 120a, 120b (collectively or individually referred to by numeral 120). The poles 120 are diametrically opposed.

The slots 1 18 serve to separate the respective poles 120 thereby defining two distinct poles 120 spaced radially from the axis of rotation 1 12a, and not one central pole.

[0031] Similarly, the second magnet structure 1 14b defines two S poles 122a, 122b (both or each referred to by numeral 1 22). An S pole 122a is axially aligned with a corresponding N pole 120a forming a dipole pair. Thus, it will be appreciated that each magnet structure 1 14 provides a plurality of circumferentially spaced poles of the same type. In FIG. 2, the magnet structures 1 14 may include permanent magnets to provide the poles 120, 122. In other examples, the poles may be provided by electromagnets.

[0032] As a generator, the rotor 1 10 is mechanically rotated and a current is induced in the windings of the stator 130. The current is gathered directly from the windings of the stator 130 (with the necessary switching) so no brushes are required.

[0033] As a DC motor, the windings in the stator 130 are activated and switched so that a magnetic field of opposite polarity (i.e., S) is generated and leads the N pole 120a of the magnet structure 1 14a. As the N pole 120a passes the winding, the winding is either deactivated or preferably reversed so that it is the same polarity (i.e., N) and lags the N pole 120a and thus repels it, thereby providing a near- continuous torque in the same direction. The polarity of the other magnet structure 1 14b is opposite, and thus the polarity generated by the windings will also be opposite.

[0034] FIG. 3 shows a second embodiment of an electric rotary machine 200 in accordance with the invention. In this embodiment, the electric rotary machine 200 has essentially been achieved by doubling the components of the electric rotary machine 100 of FIGS 1 -2. Numerals in FIG. 3 corresponding to those of FIGS 1 -2 refer to corresponding parts. This principle of corresponding numerals/parts applies to all the FIGS.

[0035] The electric rotary machine 200 has the same magnet structures 1 14 and rotor linkage piece 1 16 of the electric rotary machine 100 of FIG. 1 , but then also has an additional set of magnet structures 214 separated by another rotor linkage piece 1 16. Accordingly, in the rotor 210, the order is: magnet structure 1 14a, rotor linkage piece 1 16, magnet structure 1 14b, and then magnet structure 214b, rotor linkage piece 1 16, and magnet structure 214a. The two abutting magnet structures 1 14b, 224b may be considered as one magnet structure with twice the length and strength of those 1 14a, 214a at the ends of the rotor 210.

[0036] Similarly, a stator 230 of the electric rotary machine 200 has also been doubled. The order of parts is: winding structure 134a, stator linkage piece 136, winding structure 134b, and then winding structure 234b, stator linkage piece 136, winding structure 234a.

[0037] FIG. 4 illustrates another aspect of the electric rotary machine 200. In the rotor 210, the same poles (S poles 122, 222, in this case) are provided by central abutting magnet structures 1 14b, 224b. The N poles 120, 220 are provided by the end magnet structures 1 14a, 214a. The combined central magnet structures 1 14b, 214b may have a joined magnetic field, and the rotor 230 may thus (in effect) have half as many S poles 122, 222 but they may be twice as strong as the N poles 120, 220.

[0038] FIG. 5 shows a sectional view of the electric rotary machine 100, in assembled condition, in a first plane which does not intersect either the slots 1 18 in the magnet structures 1 14 or the grooves 138 in the winding structures 134. A slight air gap is provided between the rotor 1 10 and the stator 130. [0039] FIG. 6 shows a sectional view of the electric rotary machine 100, in assembled condition, in a second plane which does intersect the slots 1 18 in the magnet structures 1 14 and the grooves 138 in the winding structures 134.

[0040] FIG. 7 shows a sectional view of the electric rotary machine 200, in assembled condition, in a first plane which does not intersect either the slots 1 18 in the magnet structures 1 14, 214 or the grooves 138 in the winding structures 134, 234. A slight air gap is provided between the rotor 210 and the stator 230.

[0041] FIG. 8 shows a sectional view of the electric rotary machine 200, in assembled condition, in a second plane which does intersect the slots 1 18 in the magnet structures 1 14, 214 and the grooves 138 in the winding structures 134, 234.

[0042] FIG. 9 shows the stator 130 of the electric rotary machine 100, with windings 150, 152. Although various winding configurations may be practicable, in this example, a conductor (e.g. copper wire) 150a is wound many times around an individual tooth 140 of the first winding structure 134a. When a sufficient number of windings or turns around that tooth 140 is achieved, the same conductor 150b is wound around the aligned tooth 140 of the second winding structure 134b. This is repeated for each tooth 140, although only two windings 150, 152 are illustrated.

[0043] The windings 150, 152 are individually controllable, to activate some but not others, or to change the polarity of some relative to others. Various examples of control circuitry are mentioned below.

[0044] There are various structural and mechanical variations which may be applied to the electric rotary machines 100, 200. The following FIGS illustrate some of these variations. [0045] FIG. 10 shows an embodiment of a rotor/stator configuration 300 in which a rotor 302 (or the magnet structures provided on the rotor 302) is not circular but rather is flattened. Opposite sides 303 of the rotor 302 are flat and form chords of a circular outline of the rotor 302. This configuration may result in less material used in the rotor 302 and hence a lighter and/or cheaper rotor 302 with increased diameter. Windings 304 are provided circumferentially around an entire circumference of the stator, or the windings may be axially arranged.

[0046] FIG. 1 1 shows an embodiment of a rotor/stator configuration 310 in which the rotor 302 is the same as that of FIG. 10. However, the stator has two groups of diametrically opposed windings 314 at each side, interspaced by regions 316 where windings are absent. This partial winding configuration may save material and thus reduce the cost or size of the machine. In addition, this enables dimensions of the machine to increase with less material and with less power applied to the machine, as only segments exposed to rotor segments need to be activated.

[0047] FIG. 12 illustrates an embodiment of a rotor/stator configuration 320 in which the stator windings 304 are the same as those of FIG. 10. However, a rotor 322 (or at least a portion of the rotor and magnet elements carried by the rotor 322) is eccentric. For balance, there may well be another eccentric but opposite portion (not illustrated) to the rotor 322. In this example, an eccentric magnet structure may provide only a single pole of one polarity, with a similar axially-spaced eccentric magnet structure (not illustrated) providing only a single pole of the opposite polarity.

[0048] FIG. 13 an embodiment of a rotor/stator configuration 330 in which the stator windings 304 are the same as those of FIG. 10. However, the rotor 332 provides an uneven number of balanced poles 334 - three equi-angularly spaced poles 334 of the same polarity, in this case. Similarly, although not illustrated, there could be four quarter poles, or so forth. [0049] Although most of the FIGS illustrate a machine with two poles on each magnet structure, there may be any practicable number of poles. Importantly, all of the poles provided by any magnet structure in a plane transverse to the axis of rotation should be the same - there should not be mixed or alternating poles unless they are axially spaced apart. For example, there may be: one pole (eccentric); two poles (the same polarity, either balanced and diametrically opposed, or unbalanced and not diametrically opposed); three poles (of the same polarity and usually equi-angularly spaced); four poles (of the same polarity and usually equi-angularly spaced); and so forth.

[0050] The electric rotary machines 100, 200 use a sensing arrangement and a switching arrangement. Conventional sensing and switching arrangements may be practicable. However, the Applicant has also developed a customised sensing arrangement for use with the electric rotary machines 100, 200. FIGS 14-15 illustrate parts of this sensing arrangement.

[0051] FIG. 14 shows part of a machine 400, in accordance with the invention, having a stator 402 which has 12 windings, designated windings 1 -6 and A-F. Opposite windings (e.g., 1 and A) are formed by a common conductor (i.e., in parallel, but a series configuration may also be possible) and are thus switched simultaneously. Non-opposite windings (e.g., 4 and F) are formed by separate conductors and can thus be switched independently.

[0052] The sensing arrangement comprises two arcuate rows of optical emitters 410, 412, namely an outer row 410 and an inner row 412. As the windings 1 -6, A-F are symmetrical, the rows of optical emitters 410, 412, need to span only half an arc and not a full arc. Each radial pair of optical emitters can thus be associated with a pair of diametrically opposed windings. In this example, the optical emitters 410, 412 are provided by active elements like light-emitting diodes. The optical emitters 410, 412 are always on, that is, always emitting light, and are stationary because they are part of the stator 402.

[0053] A series of optical sensors (e.g., photosensitive diodes) is also provided. The optical sensors are arranged identically to the optical emitters 410, 412 but axially spaced some distance away. FIG. 14 thus illustrates the layout of the optical sensors. There is a clear path between the optical emitters 410, 412 and optical sensors, which can be blocked or occluded only by an optical mask. In principle, the inner row of emitters and sensors 412 enables attractive forces (that is, opposite polarities) and the outer row of emitters and sensors 410 enables repulsive forces (that is, the same polarities).

[0054] A disc-shaped optical mask 430 is mounted to a rotor of the machine 400. Instead, the emitters and sensors 410, 412 could be fixed to the stator and the optical mask to the rotor. The optical mask 430 is generally optically opaque, with the notable exception of four arcuate slits (acting as windows) 432, 434 arranged towards a periphery of the optical mask 430. There are two diametrically opposed outer arcuate slits 434 and two diametrically opposed inner arcuate slits 432. The outer slits 434 have a radius or curvature which corresponds to that of the outer row 410 of optical emitters and sensors, while the inner slits 432 have a radius or curvature which corresponds to that of the inner row 412 of optical emitters and sensors.

[0055] It will be appreciated that the configuration of slits 432, 434 is such that, for a given radially-aligned pair of optical emitters (that is, one from the outer row 410 and one from the inner row 412), one will always be blocked and the other will always be unblocked by the optical mask 430. For every quarter turn of the rotor, the radially-aligned pair of optical emitters will swap. [0056] When an optical receiver in the outer row 410 senses an optical emission from the corresponding optical emitter in the outer row 410, the corresponding emitter/sensor combination in the inner row 412 will be blocked. This signals that the winding pair (e.g., A-1 ) should be repulsive. That is, if the magnet structure in the rotor of the machine 400 provides N polarities, then the winding pair A-1 should be matched to provide an N polarity too. When the optical mask 430 rotates a quarter turn (i.e., 90°), then the inner row 412 of the given optical emitter/receiver pair will be linked, while the outer row 410 of radially-aligned optical emitter/receiver pair will not be linked. This signals that the windings A-1 should provide an attractive force, i.e., S polarity.

[0057] As there are 12 windings 1 -6, A-F and four slits 432, 434, the windings 1 - 6, A-F will be grouped into four groups of three windings each. Accordingly, three windings (e.g., 1 -3) will provide N polarity, three windings, (e.g., 4-6) will provide S polarity, three windings (e.g., A-C) will provide N polarity again, and the remaining three windings, (e.g., D-F) will provide S polarity again. One of the poles (e.g., 120a) of the magnet structure 1 14a should always be arranged between two groups of windings, one S and the other N, for maximum torque.

[0058] The optical mask 430 could be configured differently for a different configuration of magnet structures and/or windings. For example, if there were three pole sets (instead of two) provided by the magnet structure, then the optical mask may have six slits and each of the inner and outer rows may only have four emitters/receivers.

[0059] FIGS 16-18 illustrate a part of a 3-phase wound rotor induction machine 500. Only a rotor 502 is illustrated - the stator may be as illustrated in any of FIGS 1 -12.

[0060] FIG. 16 shows the rotor 502 without windings. The rotor 502 has two magnets structures 514a, 514b which (in contrast to those of FIGS 1 -8) comprise circumferentially spaced grooves 538 and teeth 540. One of the magnet structures (e.g., the first magnet structure 514a) will provide a plurality of circumferentially spaced N poles, while the other (e.g., the second magnet structure 514b) will provide matched circumferentially spaced S poles. If desired, the grooves 538 could be slightly inclined.

[0061] FIG. 17 shows the rotor 502 with windings 550. A continuous conductor is used for both aligned teeth 540 of the magnet structures 514. Coils 550a are wound around the tooth 540a of the first magnet structure 514a and then around the tooth 540b of the second magnet structure 514b. The wire ends of the windings 550 are connected to shorting brushes as in conventional machines. (The number of rotor teeth 540 and stator teeth 140 should not be equal.)

[0062] In use, the windings 150 in the stator 130 will induce a voltage in the rotor windings 550. This results in current flow in the rotor windings 550 which consequently will cause the rotor 502 to rotate (Lenz's Law).

[0063] FIG. 18 shows an extended rotor 570 which includes two extra magnet structures (having the same numerals 514b, 514a as the first two) and corresponds in layout to the rotor 210 of FIG. 3. Windings 570 are now simply extended to the additional two magnet structures 514 with a first group of windings 572a being wound around a tooth 540a of the first magnet structure 514a, a second group of windings 572b being wound around both the teeth 540b of the middle magnet structures 540b and a third group of windings 572c being wound around a tooth 540c of the last magnet structure 514a.

[0064] A stator of the induction machine 500 could include windings around an entire periphery (as in FIG. 10) or only around parts of the periphery (as in FIG. 1 1 ). Instead, the stator could be a squirrel cage arrangement. In such case, instead of windings in the slots of the stator, there may be copper or aluminium rods or bars inserted therein. Three shorting rings may then be provided, one ahead of the first magnet structure 514a, another between the magnet structures 514a, 514b, and a third of the second magnet structure 514b.

[0065] FIGS 19-27 illustrate various alternative switching circuits which could forms part of the switching arrangement.

[0066] FIG. 19 illustrates a switching circuit 600 which is an IGBT (Isolated Gate Bipolar Transistor) H-bridge.

[0067] FIG. 20 illustrates a switching circuit 610 having contacts 612, 61 4 to which one or more photosensitive diodes or transistors forming part of the sensing arrangement are connectable.

[0068] FIG. 21 illustrates a switching circuit 620 which is IGBT-based and provides galvanic isolation.

[0069] FIG. 22 illustrates a switching circuit 630 which is a MOSFET (metal- oxide-semiconductor field-effect transistor) H-bridge and could also be a BJT H- bridge (not illustrated).

[0070] FIG. 23 illustrates a switching circuit 640 which is a thyristor-based H- bridge.

[0071] FIG. 24 illustrates a switching circuit 650 which is a thyristor commutation arrangement.

[0072] FIG. 25 illustrates a switching circuit 660 which is a thyristor turn-on arrangement. [0073] FIG. 26 illustrates a three op-amp based switching circuit 670.

[0074] FIG. 27 illustrates a switching circuit 680 which is another example of a thyristor commutation arrangement.

[0075] With reference again to FIGS 14-15, the optical sensors in the inner and outer rows may be connected to contacts 612, 614 of the circuit 610. When the optical sensor senses light, its resistance changes which influences a balanced bridge of the circuit 610 and the resulting difference is picked up by an op-amp in the circuit 610 which can drive power switches directly or via a galvanic isolation arrangement.

[0076] A direct current motor may be driven by the H-bridges of one or more of the circuits 640, 600, 630. For starting a synchronous motor in accordance with the invention, circuit 620 could be used. Instead, a squirrel cage arrangement could be used.

[0077] Referring now to FIGS 28-33, reference numerals 700-789 generally refer to components for a DC machine run from a dedicated source via an AC source or a pulsating DC source. This is useful in situations where the size of these machines is large and many switching components are needed. This embodiment of the machine can be considered as a dual motor that operates on pulsating power and DC; the pulsating power can be of different phases. [0078] FIG. 31 illustrates a minor motor rotor 760 which is fed pulsating power through slip ring with brushes connected externally. A rectifying device can also be directly connected to wires from respective segments of the rotor 760. Magnetic loading and wire lengths and dimensions of the rotor 760 are different from those of major rotor 770. Also, stator dimensions and teeth sizes for the rotors 760, 770 are different but equal in number. [0079] The speed of the major motor (having major rotor 770) is the same as that of the minor motor (having the minor rotor 760) and is locked on the same shaft or axle 1 12 and with slots 762, 772 in line. This is necessary where high currents may be needed but brushes have limited current carrying capacity taking advantage of the fact that pulsating voltage can be stepped up or down through transformer or inductive action. This design also takes into consideration the fact that as poles increase the speed falls.

[0080] Discs of the rotor 760 are fed pulsating power through slip rings. The windings are arranged axially so as to give different AC pole arrangements such as indicated by "S" and "N" in the FIGS. In the illustrated arrangement, the "N" poles lead (attract) the "S" poles of the rotor 770 while the "S" poles of rotor 760 are lagging poles. Where power is from a multiphase source, the "S" poles can be of different phases and the same may apply to the "N" poles. The connections of diametrically opposite segments are connected before being connected to corresponding segments in rotor 770 which receive redistributed smoothed power.

[0081] The slots 762 in rotor 760 effect commutative action in rotor 770. Attraction motion is enabled when a tooth is approached by "N" segments until the slot approaches the middle of the tooth. In view of the half tooth with of the slot on the rotor power transmission stops until the lagging segment starts effecting repulsion. The commutation is effected through slots in the rotor 760. The difference in sizes of rotor 760 and rotor 770 are important in that higher torque is realisable in rotor 770 through making dimensions of rotor 770 different from rotor 760, different magnetic loading and wire lengths in rotors 760, 770.

[0082] The dual motor obviates the need for electronic or brush commutation. Furthermore, axial lengths of teeth in rotor 770 can be shorter while the diameter is greater. As rotor 770 is two pole and rotor 760 is four pole, the need to equalise the speeds on the same shaft will dictate that rotor 770 has higher magnetic loading and the corresponding stator takes more wire length than stator corresponding to rotor 760. This arrangement is possible for all DC motors in accordance with the invention. The rotor 770 is supplied with steady DC. [0083] FIGS 28-29 relate to cut pieces of laminations presented for assembling the machine. It should be noted that there is much effort dedicated towards increasing the magnetic flux with a view to building smaller motors for comparable power loading. As higher flux densities in conventional motors entail increased flux leakages and higher number of ampere turns per metre to achieve these flux densities, attention is being directed to superconducting material.

[0084] FIG. 28 illustrates a pair of laminations, namely a main piece 710 and a shorter piece 720, made of ferromagnetic electric steel. The main piece 710 has a shoulder for bolting to a non-magnetic frame (not illustrated) and an abutting surface 714 for abutting the frame. The shorter piece 720 also has a shoulder 722 (illustrated in FIG. 29) for bolting to the non-magnetic frame, as well as an abutting surface 724 for abutting the frame. [0085] FIG. 29 illustrates a strip 730 having bolting holes 732 to facilitate bolting the pieces 710, 720 to the frame. This enables shorter magnetic paths, reducing magnetic flux leakages as the magnetic flux will take the path of least resistance, and hence most of it should be confined to the laminations as the non-magnetic material supporting the laminations provide a high resistance path. Component 740 is an assembly of electric steel laminations having an edge 742 which abuts the frame.

[0086] FIGS 30, 32-33 illustrate embodiments of rotor 750, 780 having eccentric magnet structures. In FIG. 30, the rotor 750 comprises two axially-spaced magnet structures, 752, 754, one having an N pole and the other having a corresponding S pole.

[0087] In FIGS 32-33, the rotor 780 has four axially-spaced magnet structures 782-788 in two pairs, with a first pair of magnet structures 782-784 defining an N-S pole pair and the second pair of magnet structures 786-788 also defining an N-S pole pair. The magnet structures of each pole pair are separated by a rotor linkage piece 789. [0088] The Applicant believes that the invention as exemplified has significant advantages when compared with conventional machines having (usually a single ring of) circumferentially-spaced alternating poles/polarities. The electric rotary machine of the present invention is longitudinally scalable. For example, the electric rotary machine 200 is twice as long as the electric rotary machine 100 and can be scaled further, as operating conditions dictate or permit, simply by adding magnet structures lengthwise.

[0089] Also, a radius of the electric rotary machine (usually an outer radius of the rotor or inner radius of the stator) is scalable without needing to increase the number of poles of the rotor or windings of the stator. This obviates the old problem of requiring more magnetic flux to drive the rotor/stator as size (specifically, radius) increases which, in conventional machines, necessitates more poles/windings.

[0090] The axial arrangement of magnetic poles provides shorter magnetic flux paths and more flux is available in the teeth when designed as in FIG. 29 and magnetic flux in the teeth is not affected by the adjacent pole sets as in the conventional machines.

Claims

1. An electric rotary machine which has a stator and a rotor which is operable to rotate relative to the stator about an axis of rotation, characterised in that: the electric rotary machine includes at least two groups of magnet structures; the groups of magnet structures are provided on one of the rotor or the stator and are spaced apart relative to each other axially along the axis of rotation, while conductive windings are provided on the other of the stator or the rotor; and each group of magnet structures provides, or is configured to provide, at least one eccentric magnetic pole of one polarity only and no magnetic poles of the other polarity.

2. The electric rotary machine as claimed in claim 1 , in which each group of magnet structures provides, or is configured to provide, at least two circumferentially spaced magnetic poles of the same polarity only and no magnetic poles of the opposite polarity.

3. The electric rotary machine as claimed in any one of claims 1 -2, in which each group of magnet structures is disc-shaped or annular.

4. The electric rotary machine as claimed in claim 3, in which each magnet structure defines a radially inwardly extending slot or groove between adjacent magnetic poles, the magnet structure thus being constituted by a plurality of sectors, with each sector providing one magnetic pole, sectors being interspaced by the slots.

5. The electric rotary machine as claimed in any one of claims 1 -4, in which each magnet structure provides two magnetic poles of the same polarity only.

6. The electric rotary machine as claimed in claim 5, in which the magnetic poles are diametrically opposed.

The electric rotary machine as claimed in any one of claims 1 -4, in which each magnet structure provides more than two magnetic poles provided by the magnet structure, the poles being equi-angularly spaced around the axis of rotation.

8. The electric rotary machine as claimed in any one of claims 1 -7, which has two groups of magnet structures.

The electric rotary machine as claimed in claim 8, in which one group provides magnetic poles of north (N) polarity only, while the other provides magnetic poles of south (S) polarity only.

The electric rotary machine as claimed in claim 9, in which adjacent magnet structures are linked or associated with each other and that the N and S poles forming a dipole magnet provided by adjacent magnet structures are axially spaced from each other.

11. The electric rotary machine as claimed in any one of claims 1 -7, which has more than two groups of magnet structures.

The electric rotary machine as claimed in claim 1 1 , in which the magnet structures are arranged to provide magnetic poles of alternating polarity; that is to say, one magnet structure provides a plurality of N poles, while the next provides a plurality of S poles, with the next providing a plurality of N poles.

3. The electric rotary machine as claimed in claim 12, in which intermediate (that is, non-end) magnet structures are double a width or strength of the end magnet structures.

4. The electric rotary machine as claimed in any one of claims 1 -13, which is operated either as a motor or as a generator.

5. The electric rotary machine as claimed in any one of claims 1 -14, which is operated as a DC (Direct Current) machine, or as an AC (Alternating Current) machine, or a combination thereof.

6. The electric rotary machine as claimed in any one of claims 1 -15, in which the magnet structures are provided by fixed magnets or variable magnets.

7. The electric rotary machine as claimed in any one of claims 1 -16, which includes a switching arrangement to switch a polarity and/or current direction of the windings.

8. The electric rotary machine as claimed in claim 17, in which the switching arrangement includes a sensing arrangement including one or more sensors.

9. The electric rotary machine as claimed in claim 18, in which the sensing arrangement includes a plurality of optical receivers operable to sense presence or absence of optical markings or emissions.

!0. The electric rotary machine as claimed in claim 1 9, in which the sensing arrangement includes an optical mask to occlude at least some of the optical markings or emissions which will then not be sensed by the optical receivers.

21. The electric rotary machine as claimed in claim 20, in which the optical mask is fast with the rotor, while the optical receivers and optical markings/emissions are fast with the stator.

22. The electric rotary machine as claimed in any one of claims 1 -21 , which is operable as a dual motor with AC or DC fed from a dedicated source or AC or pulsating DC such that one part runs on pulsating power or AC while the other part runs on DC, the two parts being fixed on the same shaft but having differing number of pole sets.