GB2546256A

GB2546256A - Electrical machine

Info

Publication number: GB2546256A
Application number: GB1600297.4A
Authority: GB
Inventors: George Fraser Alexander; Richard Glover Anthony
Original assignee: McLaren Automotive Ltd; McLaren Applied Technologies Ltd
Current assignee: McLaren Automotive Ltd; McLaren Applied Ltd
Priority date: 2016-01-07
Filing date: 2016-01-07
Publication date: 2017-07-19
Also published as: GB201600297D0; WO2017118855A1

Abstract

The arrangement comprises a first and second components each comprising a plurality of magnetically independent elements 30 and a third component 42 comprising a plurality of pieces 42 polarised by electromagnetic coils 48. The elements 30 and the pieces 42 move relative to each other. In use at least one magnetic circuit is formed, causing the element and the pieces to be drawn towards a condition in which a magnetic circuit is formed in a respective element of the first and second components and two pieces of the third component, the magnetic circuit flowing serially from one of an element and piece to the other of an element and a piece. The arrangement may be an axial flux dual rotor machine, the wound stator poles either being separate or having links 58 in a magnetically neutral region. The rotor elements may be permanent magnets or U shaped reluctance elements with pole portions 62. The magnet flux may pass though adjacent poles or poles either side of a central pole. Fig 9 (not shown) has an arrangement having two stators 40,80 and three rotors 26,82,84, the central rotor 82 interacting with the stators 40,80 and their respective outer rotors 26,84. Radial air gap and linear arrangements are covered.

Description

ELECTRICAL MACHINE

This invention relates to an electrical machine. In particular it relates to electrical machines such as motors and generators. In the case of a motor mechanical energy may be extracted from the machine as a result of electrical energy being input in to the machine. In the case of a generator electrical energy may be extracted from the machine as a result of mechanical energy being input in to the machine.

Electrical machines are used in a wide variety of circumstances. One area of increasing interest and use for electrical machines is in the field of fully electrically driven vehicles, where drive is provided by one or more electric motors, and in hybrid electrically driven vehicles, where drive is provided by a combination of at least one electric motor and other drive source(s). In most circumstances, including this field, there is a desire to improve the effectiveness and especially the efficiency and power-to-weight ratio of electrical machines.

Many kinds of electrical machine make use of reluctance torques to cause components of the electrical machine to move relative to other components of the electrical machine (when the electrical machine is being used as a motor). Example kinds of electrical machine that may make use of reluctance toques in this way are switched reluctance electrical machines and wound field flux switching electrical machines. In an example case of a motor that produces drive along a rotational axis, the rotor of the motor is arranged to rotate by means of reluctance torques. This may be achieved using a rotor that is made from a soft ferromagnetic material, such as iron or a composite containing iron. It may also be achieved by using a rotor that comprises both soft ferromagnetic material (i.e. non-permanently magnetic material) and hard ferromagnetic material (i.e. permanently magnetic material). It will be appreciated that reference to permanent and non-permanent are relative terms and a material that exhibits a permanent magnetic effect may be capable of being transitioned in to a material with a non-permanent magnetic effect and vice versa. A ferromagnetic material is a material that is capable of becoming magnetised in the presence of a magnetic field. It is usual in, for example, a switched reluctance electrical machine to use ferromagnetic material that is capable of exhibiting both a magnetised state (in which the material is magnetically polarised) and an unmagnetised state (in which the material is not magnetically polarised) during the operation of the machine. The ferromagnetic material of the rotor can magnetically interact with magnetically polarised regions on a stator. Those regions on the stator can be selectively energised and de-energised using electromagnetic coils. The selective energising and de-energising of selected regions of the stator causes the rotor to rotate about its axis. This rotation is caused by magnetic flux circuits following paths of least reluctance through the rotor(s), stator(s) and gaps between the rotor(s) and stator(s) and causing the rotor(s) to move towards a condition with the stator(s) that has a lower reluctance.

To generate the paths through which the magnetic flux can flow to form the magnetic flux circuits through the rotor(s) and stator(s), many switched reluctance electrical machines comprise a large volume of static ferromagnetic material or back iron in the form of the stator. This is so that the magnetic flux can flow through the rotor(s) in the required place to generate a torque (in the case of a motor). As discussed above, in most circumstances, including this field, there is a desire to improve the effectiveness and especially the efficiency and power-to-weight ratio of electrical machines. Such a large quantity of ferromagnetic material in the form of the stator(s) can therefore be undesirable.

There is therefore a need for an improved electrical machine.

According to a first aspect of the present invention there is provided an electrical machine comprising: a first component and a second component each comprising a plurality of magnetically independent elements; a third component comprising a plurality of pieces; and electromagnetic coils for magnetically polarising the pieces; wherein either (i) the first and second components or (ii) the third component are arranged to move relative to the other of (i) the first and second components and (ii) the third component, and the elements are arranged to magnetically interact with the pieces so that, when pieces are polarised by the coils, at least one magnetic circuit is formed, causing either (i) the first and second components or (ii) the third component to be drawn towards a condition in which the or each magnetic circuit is formed in magnetic material comprising material of a respective element of the first and second components and material of two pieces of the third component, the magnetic circuit flowing serially from one of an element and piece to the other of an element and a piece.

The first and second components may be each spaced apart from the third component to form a gap between the surface of each element facing the pieces and the surface of each piece facing the elements. The magnetic circuit may flow serially from one of an element and piece to the other of an element and piece across a gap between that element and piece. The condition may be when the or each magnetic circuit is formed in magnetic material comprising material of a respective element of the first and second components and material of two pieces of the third component and four gaps. The gaps may be air-gaps. A plurality of magnetic circuits may be formed, and the condition may be when each magnetic circuit is formed in magnetic material comprising material of different respective elements of the first and second components and material of a different two of the polarised pieces. The condition may be when the magnetic material of each magnetic circuit is substantially wholly material of the first and second components and the two respective pieces. The or each magnetic circuit may be the predominant flux path flowing between the two polarised pieces of the respective magnetic circuit.

The electrical machine may comprise at least one electromagnetic coil per piece. Each piece may have at least one coil wrapped around the piece. The electrical machine may comprise one electromagnetic coil per piece. Each piece may have a respective coil wound around it.

The electromagnetic coils of pairs of adjacent pieces may be configured to polarise the pieces in the same magnetic orientation and polarise adjacent pairs of pieces in opposite magnetic orientations. The electromagnetic coils may be configured to polarise pieces either side of a central piece. Electromagnetic coils may be associated with the pieces either side of a central piece to polarise those pieces either side of a central piece and no electromagnetic coils may be associated with the central piece.

Each piece may be composed of a ferromagnetic material and the electrical machine may be arranged to magnetically energise and magnetically de-energise the ferromagnetic material using the electromagnetic coils during operation of the machine. At least two pieces may be joined together. The at least two pieces may be joined together where the two pieces have neutral magnetic potential between them when the pieces are polarised by the coils. The electrical machine may comprise non-magnetically susceptible material joining at least two pieces together. The electrical machine may comprise ferromagnetic material joining the at least two pieces together.

The first and second components may be arranged to move relative to the third component. The first and second components may be constrained so that their elements are capable of movement along a respective path and the third component may be positioned between the paths. The first and second components may be rotors and may be each arranged to revolve about respective axes. The first and second components may be each arranged to revolve about the same axis. The first and second components may be angularly locked to a common shaft running along the axis. The first and second components may be mechanically coupled to rotate in opposite directions. The pieces may be spaced radially around the axis of rotation.

The first and second components may be each arranged to move along a respective line. The paths of the first and second components may be parallel. The first and second components may be mechanically linked together to move in unison.

The third component may be arranged to move relative to the first and second component. The third component may be constrained so that its pieces are capable of movement along a path and the first and second components may be positioned opposite each other on either side of the path. The third component may be arranged to revolve about an axis. The third component may be arranged to move along a line.

The first and second components or the third component may be constrained so that their elements or pieces can move in a respective path, and the pieces may be spaced along the path. Each element may be sized to form a magnetic circuit with neighbouring pieces. Each element may be sized to form a magnetic circuit with pieces either side of a central piece.

The elements of each component may be spaced from each other by non-magnetically susceptible material. Each element may comprise a pair of protrusions, the protrusions may extend towards the pieces, and the condition may be when each magnetic circuit is formed in magnetic material comprising material of the protrusions.

The electrical machine may comprise: a fourth component comprising a plurality of magnetically independent elements; and a fifth component comprising a plurality of pieces; wherein either (i) the first, second and fourth components or (ii) the third and fifth components may be arranged to move relative to the other of (i) the first, second and fourth components and (ii) third and fifth components; and the elements of the fourth and second components may be arranged to magnetically interact with the pieces of the fifth component so that, when the pieces of the fifth component are polarised by the coils, at least one other magnetic circuit is formed, causing either (i) the second and fifth components or (ii) the fourth component to be drawn towards a condition in which the or each other magnetic circuit is formed in magnetic material comprising material of a respective element of the fourth and second components and material of two polarised pieces of the fifth component, the other magnetic circuit flowing serially from one of an element and piece to the other of an element and piece.

The second and fourth components may be each spaced apart from the fifth component to form a gap between the surface of each element facing the pieces and the surface of each piece facing the elements. The other magnetic circuit may flow serially from one of an element and piece to the other of an element and piece across a gap between that element and piece. A plurality of other magnetic circuits may be formed, and the condition may be when each other magnetic circuit is formed in magnetic material comprising material of the respective element of the second and fourth components and material of a different two of the polarised pieces of the fifth component. The magnetic material of each other magnetic circuit may be substantially wholly material of the second and fourth components and the two respective pieces.

The first, second and fourth components may be arranged to move relative to the third and fifth components. The first, second and fourth components are constrained so that their elements are capable of movement along a respective path, the third component may be positioned between the paths of the first and second component, and the fifth component may be positioned between the paths of the second and fourth component. The first, second and fourth components may be rotors and each arranged to revolve about the same axis. The first, second and fourth components may be angularly locked to a common shaft running along the axis. The first, second and fourth components may be mechanically coupled to permit the first and second components to rotate in opposite directions and to permit the first and fourth components to rotate in the same direction.

The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

Figure 1 shows an isometric view of a first design of electrical machine.

Figure 2A shows an isometric section of the first design of electrical machine.

Figure 2B shows a cross-section of the first design of electrical machine.

Figure 3A shows an exploded view of a rotor of the first design of electrical machine.

Figure 3B shows an exploded view of a stator of the first design of electrical machine.

Figure 4 shows a schematic view of the first design of electrical machine.

Figure 5 shows a schematic view of the first, second and third components of the first design of electrical machine.

Figure 6 shows a schematic view of the first, second and third components of a second design of electrical machine.

Figure 7 shows a schematic, isometric view of a third design of electrical machine. Figure 8 shows a schematic, isometric view of a fourth design of electrical machine.

Figure 9A shows a schematic, isometric view of a fifth design of electrical machine.

Figure 9B shows a schematic, isometric view of a sixth design of electrical machine.

The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

The present invention relates to an electrical machine that comprises a first component and second component that each comprise a plurality of magnetically independent elements, a third component that comprises a plurality of pieces and electromagnetic coils for magnetically polarising the pieces. In one configuration, the first and second components are arranged to move relative to the third component. In another configuration, the third component is arranged to move relative to the first and second components. The elements of the first and second components are arranged to magnetically interact with the pieces so that, when the pieces are polarised by the coils, at least one magnetic circuit is formed, causing either (i) the first and second components or (ii) the third component to be drawn towards a condition in which the or each magnetic circuit is formed in magnetic material of two polarised pieces of the third component, the magnetic circuit flowing serially from one of an element and piece to the other of an element and a piece.

Figures 1 to 4 show a first embodiment of an electrical machine in accordance with the present invention. Figure 1 shows an isometric view of the first design of electrical machine. Figure 2A shows an isometric section through the electrical machine 10 along plane shown in figure 1 as A-A’. Plane A-A’ passes through the rotational axis of electrical machine 10. Figure 2A shown a cross-section through the electrical machine 10, again along plane shown in figure 1 as A-A\

Electrical machine 10 comprises a casing 12 having a generally annular side-wall 14, a front cover 16, a rear cover 18 and a drive shaft 20. Drive shaft 20 runs along the rotational axis 22 of electrical machine 10. Drive shaft 20 is mounted such that it can rotate relative to the casing 12. Drive shaft 20 can be mounted inside bearing 24 so that the drive shaft 20 can rotate relative to the bearing 24. The drive shaft 20 may be mounted to bearing 24 so that drive shaft 20 is positionally fixed but rotationally free about rotational axis 22. As shown most clearly in Figure 3B, bearing 24 is located through the centre of the electrical machine along rotational axis 22. Mechanical drive can be taken from that drive shaft 20 when the electrical machine is operating as a motor. Mechanical drive can be provided to that drive shaft 20 when the electrical machine is operating as a generator.

Front cover 16 and rear cover 18 are generally perpendicular to rotational axis 22. As shown most clearly in figure 3A, front and rear covers 16, 18 both house a rotor 26, 28. Figure 3A shows an exploded view of a rotor of the first design of the electrical machine 10. In the embodiment illustrated in figure 3A, rotor 16 is formed of a plurality of magnetically independent elements 30. These elements 30 are spaced around the rotational axis 22 in a plane generally perpendicular to the rotational axis 22. In this way the elements 30 are spaced around the path generally followed by the elements 30 during rotation of rotor 26. The elements 30 may be composed of a ferromagnetic material such that they are capable of passing a magnetic flux through them. Rotor 26 may also comprise a plurality of non-magnetically susceptible material spacers 32. The elements of each rotor may be spaced from each other by a spacer 32 of non-magnetically susceptible material. Rotor 26 may also comprise a holder 34 configured to secure the elements 30 and, if present, spacers 32 together in the plane generally perpendicular to the rotation axis 22. Rotor 26 may further comprise a retaining band 36 configured to attach rotor housing 34 to cover 16. Retaining band 36 may secure rotor housing 34, and thus rotor 26 to front cover 16.

As discussed above rotor 28 may be configured in the same, or similar fashion, to rotor 26.

It will be appreciated that rotors 26 and 28 may more generally be described as first component 26 and second component 28 of the electrical machine and the first and second components 26, 28 may each comprise a plurality of magnetically independent elements. In this way, the first and second components may be configured to move or may be static elements that are used in induce movement in other components in the electrical machine as will be described below. Such movement may be rotational, as shown and described in relation to figures 1 to 4, or may be translational, rather than simply rotation about an axis, in which case the first and second components 26, 28 may be configured to move along a path or configured to induce movement in other components along such a path. The first and second components may be configured to move in opposite directions, for example, by being connected together by a gearing that permits the first and second components to counter-rotate relative to each other.

As shown most clearly in figure 3B, casing 12 houses stator 40 located between rotors 26 and 28. Figure 3B shows an exploded view of a stator of the first design of the electrical machine 10. In the embodiment illustrated in figure 3B, stator 40 is formed of a plurality of stator pieces 42. Thus electrical machine 10 comprises a stator 40 formed of a plurality of pieces 42. These pieces 42 are spaced around the rotational axis 22 in a plane generally perpendicular to the rotational axis 22. In this way the pieces 42 are spaced around the path generally followed by the elements 30 during rotation of rotor 26. Stator 40, and thus stator pieces 42 may be held in casing 12 by front stator plate 44 and rear stator plate 46. Stator plates 44, 46 may comprise a plurality of apertures. A respective stator piece 42 may fit in to each of the apertures. The front and rear stator plates 44, 46 can therefore be used to space the stator pieces 42 apart from each other with the required spacing. The front and rear stator plates 44, 46 may fit over the stator pieces 42 so that the exterior surface of the front and rear stator plates 44,46 present a planar surface with respective the exterior surface of the stator pieces 42. The front and rear stator plates 44, 46 may be generally parallel to the plane perpendicular to the rotational axis 22 of the electrical machine 10. The front and rear stator plates 44, 46 may be sized to fit inside the casing 12 and may be sized to provide an interference fit with the interior surface of the casing 12. Front and rear stator plates 44,46 may also secure bearing 24 within electrical machine 10.

It will be appreciated that stator 40 may more generally be described as a third component 40 of the electrical machine and the third component may comprise a plurality of pieces 42. In this way, the third component may be configured to move or may be static pieces that are used induce movement in other components in the electrical machine. Such movement may be rotational, as shown and described in figures 1 to 4, or may be translational, rather than simply rotation about an axis, in which case the third component 40 may be configured to move along a path or configured to induce movement in other components along such a path.

The electrical machine 10 also comprises electromagnetic coils 48 for polarising the pieces 42. The electromagnetic coil 48 may be a coil of electrically conductive material. The relationship between the electromagnetic coil 48 and the pieces 42 is best shown in figure 3B but is also shown in the other figures 1 to 4. A respective electromagnetic coil 48 may be wound around each of the pieces 42 as illustrated in figures 1 to 4. Other configurations of electromagnetic coil 48 are envisaged by the present invention. For example, the electromagnetic coil 48 may be wrapped around only part of the piece, more than one electromagnetic coil 48 may be used to polarise a particular piece, not all of the pieces may be polarised by electromagnetic coils 48: for instance, whether the pieces have an electromagnetic coil 48 to polarise that piece may alternate around the third component 40.

The electromagnetic coils 48 are positioned so that they can induce a magnetic polarisation of a respective piece 42 when the electromagnetic coil(s) are energised by passing an electric current through the respective coil(s) 48. Each piece 42 may be composed of a ferromagnetic material and thus the electromagnetic coils can be used to magnetically energise and magnetically de-energise the ferromagnetic material. A control unit 50 can be provided in order to energise the coils of the pieces when the electrical machine 10 is acting as a motor or activate the coils of the pieces when the electrical machine 10 is acting as a motor to extract electrical energy from the electrical machine 10 in a controlled manner. The control unit 50 may comprise logic circuitry 52 which receives input from a sensor 54 configured to detect the rotational position of the components 26, 28 that comprise a plurality of magnetically independent elements. In dependence on that input the logic circuitry outputs current to the appropriate one(s) of the coils. Alternatively, the control of the coils could be performed by brushes and appropriately configured slip rings moving with the moveable components of the electrical machine 10.

Figure 4 shows a schematic, isometric view of the first design an electrical machine in accordance with the present invention. In figure 4, only the main parts of the electrical machine are shown that are concerned with the control of the motion of the electrical machine. Shown in figure 4 are one configuration of first and second components 26, 28 (rotors 26, 28 in the case of figure 4), third component 40 (stator in the case of figure 4) and electromagnetic coils 48. In this configuration each first component 26 and second component 28 comprises a number of elements 30 equal to half the number of pieces of the third component 40. The elements 30 are sized so that, when they are in an aligned position relative to the pieces 42, the element 30 is capable of completing a magnetic circuit between neighbouring pieces. It is envisaged that other configurations of the elements 30 are part of the present invention.

The motion of one of (i) the first and second components and (ii) the third component relative to the other will now be described with reference to figure 5. Figure 5 shows a schematic view of the first, second and third components described above. As can be appreciated from figure 5, the first, second and third components could be arranged such that they are capable of motion about a rotational axis as shown in figures 1 to 4 above, or alternatively they could be capable of motion along a path with a translational motion that is not only rotational about an axis as also described above.

In figure 5, the elements 30 are slightly displaced from the aligned position with respect to pieces 42. The pieces 42 have been magnetically polarised by the electromagnetic coils 48 to cause opposite ends of each of the pieces 42 to be magnetically polarised relative to each other. The polarisation causes magnetic flux paths to form between the pieces 42 which in turn causes elements 30 of the first and second components 26, 28 to be drawn towards an aligned position relative to the pieces 42. In the aligned position, the elements 30 of the first and second components 26, 28 are positioned so that the predominant magnetic flux path flows serially from a component to an element and then from an element to the other component. In this way, at least one magnetic circuit may be formed, when the pieces are polarised by the coils. The pieces are polarised by causing electrical current to flow in the appropriate directions in the respective coils. The magnetic circuits are indicated schematically as the dotted lines 60 in figure 5. The magnetic circuit may be the predominant flux path flowing between the two polarised pieces of the respective magnetic circuit. It can be seen that as the elements 30 are drawn into an aligned position, each magnetic circuit 60 is formed in magnetic material comprising magnetic material of a respective element 30 of each of the first and second components and magnetic material of two pieces 42 of the third component 40.

As can be seen best in figure 5, the electrical machine 10 is configured so that there is a gap between the first component 26 and the third component 40 and between the third component 40 and the second component 28. This means that the first component 26 is spaced away from the third component 40 and the second component 28 is spaced away from the third component 40. Therefore, in the aligned case, the magnetic circuit 60 flows not only through an element 30 of each of the first component 26 and second component 28 and two pieces 42 of third component 40, but also through four gaps. In the case that the casing of the electrical machine is filled with air those gaps may be described as air gaps. The magnetic circuit 60 flows serially between an element 30 to a piece 42 via a gap in the magnetic material and between a piece 42 to an element 30 via a gap in the magnetic material. Whilst the electrical machine may be filled with air it may also be filled with another material that permits the components of the electrical machine to move but that has a magnetic permeability similar to that of air.

In figure 5, the elements 30 are in a non-aligned position with respect to the pieces 42. This causes elements 30 to be magnetically attracted towards a position where the elements 30 are aligned with the polarised piece(s). This attraction is shown by the arrows labelled F in figure 5.

In the configuration shown in figure 5, pairs of pieces may be polarised oppositely with adjacent pairs being polarised in reverse order. This leads to a configuration where, for example, one end of the pieces is polarised as: N S S N N S S N. Such a scheme means that the elements are attracted to the pieces in one direction.

As discussed above in relation to figures 1 to 4, the electrical machine 10 may comprise front and rear plates 44, 46 that hold the pieces 42 of third component 40 apart. An alternative arrangement is shown in part of figure 5 where neighbouring pieces 42 are joined together in a region 58 where the two pieces 42 have neutral magnetic potential between them when the pair of pieces are magnetically polarised by the coils. In this configuration, the electromagnetic coil may be wrapped around either side of the join 58 between neighbouring pieces or alternatively two or more electromagnetic coils could be provided with at least one to each side of the join 58. The material that constitutes the join between neighbouring pieces may be non-magnetically susceptible material.

Figure 6 shows an alternative configuration for the elements of the components that comprise elements. In this alternative configuration the elements each comprise a pair of protrusions 62. The protrusions extend towards the pieces 42 and thus the magnetic circuits shown schematically at 60 are formed in magnetic material of the pieces that comprises the material of the protrusions 62.

Also shown in the configuration of figure 6 is a design of the electrical machine where the elements are sized to form a magnetic circuit 60 with pieces either side of a central piece. Such pieces that are sized in this way may or may not include the protrusions illustrated in figure 6. The elements 30 may be shaped as in figure 3 but extend further in a lateral direction so as to, when in an aligned position with respect to the pieces 40 either side of a central piece, cover three pieces 40. In such a configuration the central piece may be non-magnetically polarised whilst the pieces either side are magnetically polarised. There may be a gap between the elements 30 of the width of one piece as shown in figure 6 or alternatively the elements 30 may be positioned so that the ends of elements 30 line up with adjacent pieces 42 when in an aligned position relative to the pieces 42.

Figures 7 and 8 show schematic isometric views of a third and fourth design of the electrical machine 10. In these designs each first component 26 and second component 28 comprises a number of elements 30 not equal to half the number of pieces of the third component 40. Such configurations mean that when some of the elements are in an aligned position with respect to the pieces, other elements are in an unaligned position with respect to the pieces. These configurations may be advantageous because they mean that the electrical machine, when acting as a motor, can be started from a non-moving configuration. This is because there cannot be a situation where all of the elements are in an aligned position with respect to the pieces and so a force can be generated by some of the elements irrespective of the first and second component 26, 28 positions relative to the third component 40.

In the case of figure 7, each of the first and second components 26, 28 have fourteen elements and the third component 40 has twelve pieces. In the case of figure 8, each of the first and second components 26, 28 have 24 elements and the third component 40 has 20 pieces.

In figures 7 and 8, the electrical machine comprises pieces 42 that have at least one electromagnetic coil for polarising the piece associated with them and also pieces 66 that do not have at least one electromagnetic coil for polarising the piece associated with them. In this way, the electrical machine comprises polarisable pieces 42 and non-polarisable pieces 66 by virtue of whether or not they have electromagnetic coils associated with them.

In the configurations shown in figures 7 and 8, every other piece is a polarisable piece 42. In other words, the electrical machine is configured so that a polarisable piece 42 is located adjacent a non-polarisable piece 66, or a piece that has at least one electromagnetic coil associated with it is adjacent a piece that does not have at least one electromagnetic coil associated with it. In such a configuration, the magnetic circuit generated when at least one electromagnetic coil is energised, polarising at least one piece, passes through a piece 42 polarised by at least one electromagnetic coil, a respective element of each of the first and second components and a piece 66 not polarised by electromagnetic coils 48.

It will be appreciated that multiple of the electrical machines described above may be coupled together to move in unison. For example, in the case of a rotating electrical machine multiple of the electrical machines may be joined to a common axle so that they can rotate together.

In an alternative configuration, shown in figures 9A and 9B, an electrical machine that comprises multiple components that comprise pieces may share intermediate components that comprise elements between those components that comprise pieces rather than having a separate element to interact with the magnetic circuit for each component that comprises pieces.

As shown in figures 9A and 9B, the electrical machine may comprise a fifth component 80 comprising a plurality of pieces 42 in addition to the third component 40 comprising a plurality of pieces 42 as described above. The general configuration of the fifth component 80 may be the same as for the third component 40. For example, it may be a stator having a plurality of stator pieces as described above. Both the fifth component 80 and the third component 40 have associated electromagnetic coils for polarising the pieces. The configuration of the electromagnetic coils relative to the pieces may be as described in relation to any of the designs and configurations given above.

The electrical machine may also comprise a fourth component 84 comprising a plurality of elements 30 in addition to the first component 26 and second component 82 comprising a plurality of elements 30, 86 as described above. In this case the elements 86 of the second component may be shaped so as to present a suitable surface for transmission of magnetic flux to both the third component 40 and fifth component 80. The general configuration of the first, second and fourth components may be the same as for the first and second components as described above. For example, they may be rotors having a plurality of rotor elements as described above. As described in more detail above, either the first 26, second 82 and fourth 84 components may be arranged to move relative to the third 40 and fifth 80 components or the third 40 and fifth 80 components may be arranged to move relative to the first 26, second 82 and fourth 84 components.

In both of the configurations shown in figures 9A and 9B, the component comprising elements 86 that has components comprising pieces to either side 40, 80. In this way, the elements of the fourth and second components 84, 86 are arranged to magnetically interact with the pieces of the fifth component 80. The elements of the second component 86 are also arranged to magnetically interact with the pieces of the third component 40. The elements of the second component 86 are therefore configured to interact with the magnetic circuit of polarised pieces of both the third component 40 and the fifth component 80. Therefore, first magnetic circuit(s) may be formed that cause either the (i) the first 26 and second 86 components or (ii) the third component 40 to be drawn towards a condition in which the or each first magnetic circuit is formed in magnetic material comprising material of a respective element of the first 26 and second 86 components and material of two pieces of the third component 40, the first magnetic circuit flowing serially from one of an element and piece to the other of an element and a piece of the first 26, second 86 and third 40 components. Also, second magnetic circuit(s) may be formed that cause either (i) the second 86 and fifth 80 components or (ii) the fourth 84 component to be drawn towards a condition in which the or each second magnetic circuit is formed in magnetic material comprising material of a respective element of the fourth 84 and second 86 components and material of two polarised pieces of the fifth component 80, the second magnetic circuit flowing serially from one of an element and piece to the other of an element and piece of the second 86, fourth 84 and fifth 80 components.

The configuration in figures 9A and 9B may be advantageous because one, instead of two, components comprising elements are required to interact with the magnetic circuit to either side of that central component. It will be appreciated that additional layers of electrical machine may be added in accordance with that shown and described in relation to figures 9A and 9B. For example, fourth component 84 could be configured to interact with magnetic circuits to either side of the component as per second component 86 shown in figures 9A and 9B.

The pieces of third component 40 and fifth component 80 may be aligned with each other or, alternatively, the pieces of third component 40 and fifth component 80 may be offset from each other. The aligned configuration is shown in figure 9A and the offset configuration is shown in figure 9B. The offset configuration in figure 9B allows for the energising of the respective coils of the pieces of the third component 40 and the pieces of the fifth component 80 at different times. The energising of the coils leading to the polarising of pieces of those components. This means that the electrical machine can be started from a non-moving configuration, when acting as a motor. This is because there cannot be a situation where all of the elements are in an aligned position with respect to the pieces and so a force can be generated by some of the elements.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. An electrical machine comprising: a first component and a second component each comprising a plurality of magnetically independent elements; a third component comprising a plurality of pieces; and electromagnetic coils for magnetically polarising the pieces; wherein either (i) the first and second components or (ii) the third component are arranged to move relative to the other of (i) the first and second components and (ii) the third component, and the elements are arranged to magnetically interact with the pieces so that, when pieces are polarised by the coils, at least one magnetic circuit is formed, causing either (i) the first and second components or (ii) the third component to be drawn towards a condition in which the or each magnetic circuit is formed in magnetic material comprising material of a respective element of the first and second components and material of two pieces of the third component, the magnetic circuit flowing serially from one of an element and piece to the other of an element and a piece.

2. An electrical machine according to claim 1, wherein the first and second components are each spaced apart from the third component to form a gap between the surface of each element facing the pieces and the surface of each piece facing the elements.

3. An electrical machine according to claim 1 or 2, wherein the magnetic circuit flows serially from one of an element and piece to the other of an element and piece across a gap between that element and piece.

4. An electrical machine according to any of claims 1 to 3, wherein the condition is when the or each magnetic circuit is formed in magnetic material comprising material of a respective element of the first and second components and material of two pieces of the third component and four gaps.

5. An electrical machine according to any of claims 2 to 4, wherein the gaps are air-gaps.

6. An electrical machine according to any preceding claim, wherein a plurality of magnetic circuits are formed, and the condition is when each magnetic circuit is formed in magnetic material comprising material of different respective elements of the first and second components and material of a different two of the polarised pieces.

7. An electrical machine according to any preceding claim, wherein the condition is when the magnetic material of each magnetic circuit is substantially wholly material of the first and second components and the two respective pieces.

8. An electrical machine according to any preceding claim, wherein the or each magnetic circuit is the predominant flux path flowing between the two polarised pieces of the respective magnetic circuit.

9. An electrical machine according to any preceding claim, comprising at least one electromagnetic coil per piece.

10. An electrical machine according to claim 9, wherein each piece has at least one coil wrapped around the piece.

11. An electrical machine according to claim 9 or 10, comprising one electromagnetic coil per piece.

12. An electrical machine according to claim 11, wherein each piece has a respective coil wound around it.

13. An electrical machine according to any preceding claim, wherein the electromagnetic coils of pairs of adjacent pieces are configured to polarise the pieces in the same magnetic orientation and polarise adjacent pairs of pieces in opposite magnetic orientations.

14. An electrical machine according to any of claims 1 to 8, wherein the electromagnetic coils are configured to polarise pieces either side of a central piece.

15. An electrical machine according to claim 14, wherein electromagnetic coils are associated with the pieces either side of a central piece to polarise those pieces either side of a central piece and no electromagnetic coils are associated with the central piece.

16. An electrical machine according to any preceding claim, wherein each piece is composed of a ferromagnetic material and the electrical machine is arranged to magnetically energise and magnetically de-energise the ferromagnetic material using the electromagnetic coils during operation of the machine.

17. An electrical machine according to any preceding claim, wherein at least two pieces are joined together.

18. An electrical machine according to claim 16, wherein the at least two pieces are joined together where the two pieces have neutral magnetic potential between them when the pieces are polarised by the coils.

19. An electrical machine according to claim 17 or 18, comprising non-magnetically susceptible material joining at least two pieces together.

20. An electrical machine according to claim 18, comprising ferromagnetic material joining the at least two pieces together.

21. An electrical machine according to any preceding claim, wherein the first and second components are arranged to move relative to the third component.

22. An electrical machine according to claim 21, wherein the first and second components are constrained so that their elements are capable of movement along a respective path and the third component is positioned between the paths.

23. An electrical machine according to claim 21 or 22, wherein the first and second components are rotors and are each arranged to revolve about respective axes.

24. An electrical machine according to claim 23, wherein the first and second components are each arranged to revolve about the same axis.

25. An electrical machine according to claim 24, wherein the first and second components are angularly locked to a common shaft running along the axis.

26. An electrical machine according to claim 23 or 24, wherein the first and second components are mechanically coupled to rotate in opposite directions.

27. An electrical machine according to any of claims 23 to 26, wherein the pieces are spaced radially around the axis of rotation.

28. An electrical machine according to claim 21 or 22, wherein the first and second components are each arranged to move along a respective line.

29. An electrical machine according to any of claims 21,22 or 28, wherein the paths of the first and second components are parallel.

30. An electrical machine according to any of claims 21 to 29, wherein the first and second components are mechanically linked together to move in unison.

31. An electrical machine according to any of claims 1 to 19, wherein the third component is arranged to move relative to the first and second component.

32. An electrical machine according to claim 31, wherein the third component is constrained so that its pieces are capable of movement along a path and the first and second components are positioned opposite each other on either side of the path.

33. An electrical machine according to claims 31 or 32, wherein the third component is arranged to revolve about an axis.

34. An electrical machine according to claims 31 or 32, wherein the third component is arranged to move along a line.

35. An electrical machine according to any preceding claim, wherein the first and second components or the third component are constrained so that their elements or pieces can move in a respective path, and the pieces are spaced along the path.

36. An electrical machine according to claim 35, wherein each element is sized to form a magnetic circuit with neighbouring pieces.

37. An electrical machine according to claim 35, wherein each element is sized to form a magnetic circuit with pieces either side of a central piece.

38. An electrical machine according to any preceding claim, wherein the elements of each component are spaced from each other by non-magnetically susceptible material.

39. An electrical machine according to any preceding claim, wherein each element comprises a pair of protrusions, the protrusions extend towards the pieces, and the condition is when each magnetic circuit is formed in magnetic material comprising material of the protrusions.

40. An electrical machine according to any preceding claim, the electrical machine comprising: a fourth component comprising a plurality of magnetically independent elements; and a fifth component comprising a plurality of pieces; wherein either (i) the first, second and fourth components or (ii) the third and fifth components are arranged to move relative to the other of (i) the first, second and fourth components and (ii) third and fifth components; and the elements of the fourth and second components are arranged to magnetically interact with the pieces of the fifth component so that, when the pieces of the fifth component are polarised by the coils, at least one other magnetic circuit is formed, causing either (i) the second and fifth components or (ii) the fourth component to be drawn towards a condition in which the or each other magnetic circuit is formed in magnetic material comprising material of a respective element of the fourth and second components and material of two polarised pieces of the fifth component, the other magnetic circuit flowing serially from one of an element and piece to the other of an element and piece.

41. An electrical machine according to claim 40, wherein the second and fourth components are each spaced apart from the fifth component to form a gap between the surface of each element facing the pieces and the surface of each piece facing the elements.

42. An electrical machine according to claims 40 or 41, wherein the other magnetic circuit flows serially from one of an element and piece to the other of an element and piece across a gap between that element and piece.

43. An electrical machine according to any of claims 40 to 42, wherein a plurality of other magnetic circuits are formed, and the condition is when each other magnetic circuit is formed in magnetic material comprising material of the respective element of the second and fourth components and material of a different two of the polarised pieces of the fifth component.

44. An electrical machine according to any of claims 40 to 43, wherein the magnetic material of each other magnetic circuit is substantially wholly material of the second and fourth components and the two respective pieces.

45. An electrical machine according to any of claims 40 to 43, wherein the first, second and fourth components are arranged to move relative to the third and fifth components.

46. An electrical machine according to claim 45, wherein the first, second and fourth components are constrained so that their elements are capable of movement along a respective path, the third component is positioned between the paths of the first and second component, and the fifth component is positioned between the paths of the second and fourth component.

47. An electrical machine according to any of claims 45 to 46, wherein the first, second and fourth components are rotors and each arranged to revolve about the same axis.

48. An electrical machine according to claim 47, wherein the first, second and fourth components are angularly locked to a common shaft running along the axis.

49. An electrical machine according to claim 47, wherein the first, second and fourth components are mechanically coupled to permit the first and second components to rotate in opposite directions and to permit the first and fourth components to rotate in the same direction.

50. An electrical machine substantially as herein described with reference to the accompanying figures.