WO2010012982A2

WO2010012982A2 - Electromagnetic induction machines

Info

Publication number: WO2010012982A2
Application number: PCT/GB2009/001815
Authority: WO
Inventors: Philip Raymond Michael Denne
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-07-29
Filing date: 2009-07-23
Publication date: 2010-02-04
Anticipated expiration: 2011-01-29
Also published as: WO2010012982A3; GB0813808D0

Abstract

An electrical machine is described which has a first part comprising at least one assembly of insulated laminar conductors in which a pattern of current paths is defined and by which a plurality of alternating phase-related electric currents can be applied to produce a travelling magnetic field of regular alternating polarity. The electrical machine also has a second part comprising at least one electrical conductor closely adjacent to the first part and intersecting the travelling magnetic field. The second part is physically separated from the adjacent surface of the conductors of the first part by an air gap and is arranged to move with respect to the first part along the locus of the travelling magnetic field when the plurality of alternating phase-related electric currents are applied to the insulated laminar conductors of the first part. This structure permits new motor topologies to be provided which have advantages relating to robustness, low-cost, lightweight simplicity, reliability and efficiency.

Description

ELECTROMAGNETIC INDUCTION MACHINES

Field of Invention

The present invention relates to electromagnetic induction machines. More particularly, embodiments of the present invention relate to electromagnetic induction machines in which insulated laminar conductors are provided in which a pattern of current paths are defined and by which a plurality of alternating phase-related electric currents can be applied to produce a travelling magnetic field of regular alternating polarity. Background of the Invention

Wireless electrical machines are physically distinguishable from those of conventional construction because the electrical conductors of wireless machines are planar in form, so that they are not placed in slots in the backing iron that are orthogonal to the air gap (as they are in conventional machines) but lie instead in the plane of the air gap and occupy the whole surface area of that gap. The electric currents of wireless motors flow in conducting paths that are transverse to the locus of motion of the armature and whose boundaries are incised into layers of insulated laminations made from conducting material which is not supported on a substrate. The absence of a supporting substrate differentiates the electrical conductors of our invention from those of the printed or plated circuit type, for example. Any number of the self-supporting conducting laminations of these electrical machines may be laid one upon the other and alternately face-reversed so as to form phases and the phases are nested and bonded one adjacent the other in a characteristic manner and in the same plane, orthogonal to the magnetic field region. It will be understood that the planar form and nested construction of the electrical components reduces the necessary width of the magnetic air gap and so improves the design of the magnetic circuit.

The edge conductors of each phase (which are equivalent to the "end windings" of conventional machines using wire coils) are arranged to overlap one another outside the air gap region, also being bonded together as part of the self- supporting electrical structure. It is known to construct linear electric motors in cylindrical form in which the output is a rod or tube. In such machines the magnetic part generally consists in an array of permanent magnets and tapered pole pieces of disc form that produces a spatially axially-periodic radial magnetic field; whilst the electrical part of such a linear motor generally consists in a stack of coils or electrical conductors that surround the armature along the axis of the machine and intersect the spatially-periodic radial magnetic field. The whole is generally contained within and bonded to a cylinder of mild steel that also acts as the backing iron by which the magnetic flux may complete its path in an axial direction. Machines of this kind are described in PCT/GB92/01277, PCT/GB98/00495, PCT/GB98/03092, PCT/GB98/03088, PCT/GBOO/02563, GB 0204197.8, GB 0204194.5, GB 0204198.6, PCT/GB 2004/000660 and GB 0503496.2, for example.

It is also known to construct rotary motors in which one part (typically the armature) consists in an array of permanent magnets and pole pieces which produce a spatially-periodic radial magnetic field. The electrical part of such a machine generally consists in a circumferential array of wire coils in a ferromagnetic material or an array of electrical conductors. The whole is generally contained within and bonded to a cylinder of mild steel that also acts as the backing iron by which the magnetic flux may complete its circumferential path. Machines of this kind are described in GB 0206897.1, GB 0309527.0, GB 0421593.5, GB 0424605.4, GB 0515313.5, GB 0521577.7 GB 0617989.9, PCT/GB2007/003482, GB 0723349.7 and GB0802154.5, for example.

It will be understood that, if the magnetic part of an electromagnetic machine is comprised of permanent magnets, there is always a significant magnetostatic force between the magnetic part and the ferromagnetic material (generally iron or steel) backing the electrical part. In the design of such machines, whether linear or rotary, the assembly process must be such as to ensure that the powerful (even dangerous) magnetic forces are carefully managed and that the armature remains always precisely centred on the axis of the machine to ensure that the radial forces are exactly balanced to prevent undue stress on the bearings.

As the required thrust or torque of such machines is increased, proportionately more magnetic material must be employed, increasing the difficulty of handling the machine components during the process of building the motor. There is also a physical limitation to the size of the permanent magnets that can be made in one piece, so that it is necessary to construct large machines by the skilled assembly of many individual magnets. Summary of Invention

According to one aspect of the present invention, there is provided an electrical machine having: a first part comprising at least one assembly of insulated laminar conductors in which a pattern of current paths is defined and by which a plurality of alternating phase-related electric currents can be applied to produce a travelling magnetic field of regular alternating polarity; and a second part comprising at least one electrical conductor closely adjacent to the first part and intersecting the travelling magnetic field, the second part being physically separated from the adjacent surface of the conductors of the first part by an air gap and being arranged to move with respect to the first part along the locus of the travelling magnetic field when the plurality of alternating phase-related electric currents are applied to the insulated laminar conductors of the first part.

This structure permits new motor topologies to be provided which have advantages relating to robustness, low-cost, lightweight simplicity, reliability and efficiency.

The first part may comprise two independently-powered sets of wireless laminations for generating respective independent travelling magnetic fields, the independent sets of wireless laminations being arranged so that their conducting paths are orthogonal and the resulting force on the conductor of the second part is the vector sum of that generated by the two independent travelling magnetic fields. This enables multi-dimensional motion of an armature to be achieved by the independent application of electric currents to the two sets of orthogonal wireless laminations.

The conductors of the first and second parts may be of cylindrical or part cylindrical form. In this case, one of the two independently-powered sets of wireless laminations may be arranged to produce an axial travelling magnetic field in a direction parallel to the central axis of the cylindrical form to cause relative linear motion between the first and second parts, and the other of the two independently- powered sets of wireless laminations may be arranged to produce a circumferential travelling magnetic field to cause relative rotary motion between the first and second parts. This enables both linear and rotary motion of an armature to be achieved by the independent application of electric currents to the two sets of orthogonal wireless laminations.

Alternatively, the conductors of the first and second parts may be of spherical or part spherical form. In this case, one of the two independently-powered sets of wireless laminations may be arranged to produce a latitudinal travelling magnetic field to cause relative latitudinal motion between the first and second parts, and the other of the two independently-powered sets of wireless laminations may be arranged to produce a longitudinal travelling magnetic field to cause relative longitudinal motion between the first and second parts. This enables motion of an armature to be controlled to follow a spherical or part spherical surface by the independent application of electric currents to the two sets of orthogonal wireless laminations.

The assembly of insulated laminar conductors may comprises a set of transverse current paths transverse the axis of relative motion, the spatial period of the transverse current paths varying along the axis of relative motion. As a result, the velocity of the travelling magnetic field may vary along the axis of relative motion even when the driving current frequency is kept the same.

In order to implement this, the assembly of insulated laminar conductors may comprise at least first and second sectors, the transverse current paths of the first sector having a different spatial period along the axis of relative motion than the second sector. Alternatively, the transverse current paths of the assembly of insulated laminar conductors may have a smoothly varying spatial period along the axis of relative motion.

The dimensions of the space between defined conducting paths transverse the axis of motion of each phase of the first part may be such that the transverse conductors of the remaining phases may be laid in the space alongside one another and alongside the conductors of the first phase in the same plane. Axially-directed sections of grouped conducting laminae of each phase of the first part may be arranged to overlap the grouped conducting laminae of the other phases in an inactive region away from the air gap.

The laminar conducting phases of the first part may be flat or smoothly curved upon first assembly and then pressed, rolled or otherwise deformed to a required profile by appropriate metalworking techniques.

The spatial period of the transverse current paths in the laminar conductors of the first part may be selected in combination with the maximum alternating frequency of the currents to define a maximum linear velocity for the travelling magnetic field. The surface areas of both the powered laminar conductors of the first part and the passive conducting plate of the second part may be increased by the use of matched corrugations transverse the axis of motion.

The passive conducting plate of the second part may be arranged to be levitated by repulsion of the travelling magnetic field to provide a frictionless bearing or to release a brake.

A ferromagnetic plate may be arranged to conform to the topology of the laminated surface of the powered assembly of patterned conducting laminations of the first part and may be affixed thereto, upon the surface distant from the air gap.

A ferromagnetic plate may be arranged to conform to the topology of the laminated surface of the passive conductor of the second part and may be affixed thereto, upon the surface distant from the air gap.

Either or both ferromagnetic plates may be arranged by choice of material or by the segmentation or lamination of the same, to have a high electrical loop resistance in a direction parallel to the transverse conductors of the first part. The powered laminations of the first part may be constructed from ferromagnetic material.

The powered laminations of the first part and/or the passive conductor of the second part may be fabricated from a material other than aluminium or copper, the material being chosen for its mechanical strength, for its magnetic properties or for its corrosion resistance, for example.

The powered laminations of the first part and/or the passive conductor of the second part may be fabricated from a flexible material. The powered laminations of the first part may form part of the stator and the passive conducting plate of the second part may form part of the armature. Alternatively, the powered laminations of the first part may form part of the armature and the passive conducting plate of the second part may form part of the stator. The planes of the conductors of the first and second parts may conform to any smooth three-dimensional shape. Furthermore, the locus of motion may follow a smooth curve in three dimensions.

The powered laminations of the first part may be included in the stator and the distance through which the armature travels may be more than three times its length, so that the stator may usefully be divided into a plurality of independently-powered and controlled sections. A plurality of armatures may be provided, the number of which is not greater than the number of independently-powered and controlled sections of the stator.

The locus of motion of the armature(s) may be circuitous. hi some embodiments, the powered sections of the stator may not be continuous, but the length of the armature may be sufficient to ensure that at least one powered section of the stator is always positioned to act upon the armature.

The armature may rotate around its own locus of motion in a pre-determined way according to its absolute position. The conducting planes of the first and second parts may conform in whole or in part to the shape of a cylinder. The armature may travel within the stator, or may alternatively travel along the outer surface of the stator.

The powered wireless laminations of the first part may be rolled to fit within a ferromagnetic cylinder, in such a way that the transverse conductors thereof are circumferential within the cylinder and around the central axis, producing a multi-pole magnetic field travelling parallel to the central axis.

The armature may include a passive conducting cylinder that is close-fitting to the cylindrically-formed powered laminations of the first part and is free to move along the axis of the cylinder. The powered wireless laminations of the first part may be rolled to fit within a ferromagnetic cylinder. The transverse conductors thereof may lie parallel to the central axis, producing a multi-pole magnetic field that rotates around the central axis. The armature may include a passive conducting cylinder that is close-fitting to the cylindrically-formed powered laminations of the first part and is free to rotate around the axis of the cylinder. The cylinder, which is hollow, may have a diameter which is substantially greater than its axial length, so as to produce a large gearless torque from a machine of minimum weight and thickness. The circumferential spatial period of the conductors of the first part may be small, so as to produce a high torque at a low rotational velocity.

The first part may comprise two independently-powered sets of wireless laminations, each rolled to fit within the ferromagnetic outer casing, one producing axial travelling magnetic fields to perform linear actuation and the other producing circumferential travelling magnetic fields to perform rotary actuation.

The armature may carry an array of permanent magnets so that one of the axes operates as a permanent-magnet brushless servomotor whilst the other operates as an induction machine. The planes of the conductors of the first and second parts may conform in whole or in part to the surface of a sphere. The armature may be moveable latitudinally or longitudinally by independent stators.

A high-thrust linear wireless motor may be in the form of a cylindrical ram which is constructed of a plurality of individual linear machines according to the above, the linear machines being packed around a central thrust tube and driven in synchronism.

A wireless cylindrical linear motor may be in the form of a ram having an emerging thrust tube and having a sliding gas seal at the end through which the tube emerges, so that the armature of the second part may act independently and simultaneously as part of a gas spring and as an electromagnetic actuator according to the above.

A wireless cylindrical linear motor may be in the form of a ram having an emerging thrust tube and having at least one sliding gas seal surrounding the armature or piston, so that the armature of the second part may act independently and simultaneously as part of two independent and counter-acting gas springs and also as an electromagnetic actuator according to the above. Such a configuration would be necessary for a flying-shear mechanism, for example. δ

The powered laminations of the first part may form elements of the stator and the passive conducting plates of the second part may form elements of the armature.

Alternatively, the powered laminations of the first part may form elements of the armature and the passive conducting plates of the second part may form elements of the stator.

The armature of the second part may have no external connection and may be slideably sealed to the lining of the stator of the first part so that the armature may act as a reciprocating pump.

The armature of the second part may have no external connection and may be driven as an inertial object so as to impart vibration to an external load through the reaction of the body of the cylinder.

The insulated patterned laminar conductors of the first part may have no substrate and may together cover the complete surface of the air gap.

Embodiments of the present invention relate to the design of a class of linear and rotary electric motors and generators that are of planar construction and in which there are neither wire coils nor permanent magnets. Wireless electrical machines of a related but different type have been described in our co-pending Applications GB

0424605.4, GB 0421593.5, GB 0503496.2, GB 0503480.6, GB 0515313.5, GB

0521577.7, GB 0617989.9, GB 0713408.3, PCT/GB2007/003482, GB 0723349.7, GB0713531.2, GB 0801256.9, GB0802154.5 and GB0802964.7.

Embodiments of the present invention seek to provide an economical means of constructing either a rotary or a linear electrical machine in which there are no permanent magnets and which do not, therefore, suffer from the effects of internal magnetostatic forces that result from their use. Further embodiments of the present invention seek to minimise the size, cost and weight of such a machine.

The wireless linear and rotary machines of these embodiments differ fundamentally from those described in our previous patent applications, including those listed in foregoing paragraphs. In our previous applications the electrical parts of the wireless motors are constructed from layers of patterned laminar conductors in which electric currents are constrained to follow pre-defined paths in a periodic magnetic field that is arranged orthogonal thereto, so as to produce directly electromagnetic forces that tend to cause motion along the chosen axis of the machine, hi the machines described in this document, however, the currents flowing in the patterned laminar conductors are instead designed to produce travelling magnetic fields that induce current flows in passive conducting materials adjacent thereto. The interaction of the travelling magnetic fields and the induced (or "eddy") currents produces a force tending to cause motion of the passive conducting material in the same direction as that of the travelling magnetic field. The genus of electrical machines described herein might therefore be termed "wireless induction motors". The part of the machine to which power is supplied consists in at least one planar assembly of patterned laminations of a conducting material (such as aluminium) that is arranged adjacent and parallel to at least one passive conductor having the same planar conformation. The assembly of patterned planar laminations is moveable in relation to the passive conductor of matching conformation. When alternating electric currents are supplied to the planar assembly of laminations, there is produced a travelling magnetic field pattern that induces eddy currents in the adjacent passive conductor, creating an electromagnetic force tending to cause or to modify its relative motion.

The flux density of the travelling magnetic field may be increased by the use of a sheet of backing iron placed behind and adjacent the array of wireless planar conductors or integral therewith. The flux density of the travelling magnetic field that intersects the passive conducting component of the induction motor may be further enhanced by the use of a ferromagnetic material, such as an iron or mild steel sheet, placed behind the passive component or integral therewith. It will also be understood that the backing iron or mild steel sheet may be generally segmented (i.e. constructed from an array of insulated bars, strips, rods or laminations) in such a way that current flow in the iron is obstructed in a direction parallel to the conducting paths of the laminations. Such measures reduce the magnitude of unwanted eddy currents in that iron, which would otherwise cause additional heat loss and inefficiency. However, the segmentation of the backing iron may not be necessary in low-cost machines that are used infrequently and/or in which maximised efficiency is not required. Where backing iron or a backing iron plate is referred-to in this document it is to be understood that measures such as segmentation may be applied, so as to reduce the eddy current losses.

The principles described herein may be extended to include the use of any conducting material for the construction of the powered laminations. Such materials may be chosen primarily for their mechanical properties or for their chemical resistance. In certain applications, it may be convenient for the laminations to be made from flexible material such as a woven fabric. The same considerations also apply to the choice of material for the passive conductor in which eddy currents are induced.

In particular it should be noted that the powered laminations may be made of a low-reluctance (ferromagnetic) material such as iron or steel. In this case the heat lost in the conducting laminations will be greater than that for a machine with aluminium conductors (for example), because iron has a higher resistivity. Nevertheless, there may be a significant benefit in some applications because the magnetic reluctance of the air gap is reduced by the ferromagnetic material and the powered conducting laminations effectively act as their own backing iron. The wireless machine using mild steel powered conductors is therefore simple to manufacture and assemble.

These benefits allow very low cost machines to be made for light-duty consumer applications, for example.

The currents flowing in the array of conducting laminations may be varied in phase at the appropriate frequency and amplitude so as to optimise the efficiency at which the wireless induction motor operates.

Generally the wireless array of conducting laminations forms the stator of the machine and the component in which the eddy currents are induced forms or is attached to the armature. However, it will be understood that in an equivalent alternative the electrically-powered array of conducting laminations may form the armature and the part in which the eddy currents are deliberately induced may form the stator.

If the wireless planar conductors (and the adjacent passive planar conductor) are substantially flat, it will be understood that the whole electrical machine will be both flat and planar. The surface area of the electrical sub system may be substantial, so that the induction force may be significant, whilst the motor will be unusually thin in the plane of its action. In an example machine, a flat planar machine can be used as a linear actuator in which the passive conductor moves back and forth relative to the surface of the planar array of laminations to which power is supplied.

It is also possible to produce a slim, flat dual-axis ("XY") actuator by the use of two superimposed thin planar arrays of laminations having orthogonal current paths, which use the same air gap and have a common passive conducting armature. It is not practical to construct an equivalent electrical machine using conventional techniques.

The conductive patterns in the powered laminae of the flat planar machine may be arranged to form a closed circle, so that when alternating currents are caused to flow in the laminae the magnetic field pattern rotates about the centre of the said closed circle. The rotating magnetic field pattern then causes the passive conducting element to rotate in the same direction. The active area of the machine may be significant and the resulting torque may be large, whilst this form of construction produces a very thin planar rotary motor. Such a motor may be distinguished from printed circuit machines of the prior art, in that 1) the powered conductors may have more than two phases, in that 2) there is no dielectric substrate, in that 3) the powered conductors cover the whole area of the air gap, in that 4) the electrically-powered laminations are generally stationary as the stator and in that 5) the motor is an induction motor. It will be understood that the topology of the machine is not inherently limited to a flat, uniform plane. The fixed and moving parts of the machine may, for example, be made to conform to all or part of the surface of a cylinder, the stator being within or without the armature, according to the application.

The pre-defined pattern of current paths in the powered laminations may be circumferential (orthogonal to the axis of the cylinder) so that the alternating magnetic field pattern travels parallel to the axis of the cylinder and the machine is a cylindrical linear actuator.

In the alternative, both parts of the machine can again be made to conform to all or part of the surface of a cylinder, the armature being designed to move within or without the external surface of the cylinder, according to the application. However, in this case the current paths of the wireless laminations are arranged to be parallel to the central axis of the cylinder, so as to cause the magnetic field to travel around or parallel to the periphery of the cylinder. The machine is a rotary induction motor or actuator.

In an alternative topology, both parts of the machine may be made to conform to all or part of the surface of a sphere or of any oblate spheroid and the orientation of the conducting patterns in the laminae can be chosen to provide longitudinal or latitudinal motion as required.

It has been previously noted that the wireless electrical machines described in previous paragraphs are exceptionally thin in relation to their other dimensions and that one set of planar laminae can be laid upon another, orthogonal set and energised independently. In the case of the cylindrical machines described above, it is therefore possible to lay two sets of powered conducting laminae one upon another, having their conducting patterns arranged to be orthogonal one to the other. One set of powered laminae might then produce a magnetic field travelling around the central axis of the cylinder, tending to produce rotary motion, whilst the second independent set of laminae might produce a magnetic field travelling parallel to the central axis, tending to cause linear motion unrelated to the rotary motion.

In the same way, it is possible to place two orthogonal sets of laminae adjacent and conforming to at least part of the surface of a passive conducting sphere, so that the action of one travelling magnetic field produces longitudinal rotation of the sphere, whilst the other travelling magnetic field produces latitudinal rotation, for example. It will be understood that both motions may be controlled independently and simultaneously.

Because each conductor lamination has a large area and replaces many individual coils and their interconnections by a single component, the use of the wireless technology greatly increases the reliability of the motor.

It will be understood that the thrust or torque developed by an induction electrical machine is a function both of the strength of the magnetic flux wave that intersects the passive conductor and of the relative velocity of that flux wave relative to the conductor. That is to say, there are optimum values of both the field strength and frequency (i.e. of differential field velocity) to produce the force required to move the load. In that to produce the required electromagnetic force in the machine, the velocity of the magnetic wave must always be significantly greater than that of the moving load, the limiting speed of the armature is always less than that of the travelling magnetic wave.

The velocity of the magnetic wave is the product of the physical length of the magnetic period (that of six inter-conductor separations for a three-phase machine) and of the energising frequency. As the energising frequency is increased, however, the finite inductance of the conductors and the backing iron opposes current flow and requires a higher drive voltage. Further, the inter-phase capacitive impedance of the end windings falls at the same time, allowing more of the supply current to be wasted as out-of-phase power. It is only necessary to increase the size and the spacing of the transverse conductors in the laminations - smoothly or in steps - to cause the magnetic wave to travel more quickly at the same energising frequency. The wireless laminar construction of the conductors is therefore especially useful for long-stroke linear electrical machines in which it is often required that the armature (usually the passive conductor) be accelerated to a very high velocity in one direction from a standing start.

It should also be noted that the overlapping phases in the end conductors of a high-speed induction machine may with advantage be fitted with inter-phase screening strips, taken to earth potential at a common point, as an effective means of reducing inter— phase capacitive losses. These may take the form of thin, insulated ribbon conductors or tapes which are interspersed with the overlapping phases of the laminar conductors, the ribbon conductors or tapes being connected to ground to reduce the inter-phase capacitance.

A laminated wireless stator can be manufactured at a much lower cost than its equivalent using conventional slotted iron and copper wire construction, so that a long- travel wireless linear machine is entirely practical. Conveniently, such a machine may have the stator divided into a number of sections and it may have a circuitous path to move objects around a machining facility, for example. It will be understood that if the stator is divided into sections that are individually controlled, a plurality of armatures may be moved and positioned by the same stator simultaneously. Our co-pending patent applications GB 0723349.7, PCT/GB2007/00348 and

GB0802964.7 describe means by which a number of wireless linear machines having the form of planar brushless three-phase servomotors may be grouped around a central shaft within a cylinder and energised synchronously so as to produce an exceptionally large thrust. It will be understood that it is also possible to group a number of wireless linear induction motors around a central shaft within a cylinder and thus to construct a compact high-thrust linear induction motor or ram. The machine may be designed so that the passive conductors are affixed the thrust tube and the powered conductors are affixed the outer cylinder or vice versa. It is to be noted that an equivalent induction machine using stators with wire coils embedded in an iron structure is impractical of construction.

Any form of cylindrical linear wireless induction machine may have the thrust tube slideably sealed against fluid flow at one end of the cylinder or the cylindrical armature slideably sealed against the stator lining tube, so that it may function simultaneously as an electromagnetic actuator and as a fluid actuator, such as the output element of at least one gas spring or as part of a compressor or pump.

As will be appreciated, the electrical assembly of embodiments of the invention consist of a set of laminae that are laid together to form phases and which are so shaped that they can be nested in the same plane in the magnetic field region. It will be appreciated that this arrangement is preferable to one in which the laminae are laid one upon another over the whole area of the conducting part of the motor, resulting in an electrical subsystem that requires a larger air gap and does not make efficient use of the copper window. The laminations may be self-supporting and need not be separated by an insulating and supporting dielectric substrate, which would increase the thickness of the electrical subsystem and further decrease the efficiency of the machine.

In embodiments of the invention, the dimensions of the transverse laminations are such as to allow several sets of such transverse laminations to nest one within the other in the magnetic field region and to overlap elsewhere. More particularly, the alternating transverse paths of the conducting laminations may be so dimensioned that separate phases may be nested one within another in the same plane in the magnetic air gap and overlapped elsewhere. There may be at least one conducting pattern within the at least one powered laminar array of the first part that takes the form of a spoked wheel having broad spokes abutting one another and filling the whole area of the wheel. The laminar array may be energised by a plurality of phased electric currents so as to produce a multi- pole rotating magnetic field. In this case, there may be at least one conducting disc of the second part, which may be caused to rotate around an axis orthogonal to the conducting elements and passing through the centre of the spoked wheel. This arrangement would thereby form a rotary wireless induction motor.

Various other aspects and features of the present invention are defined in the claims. Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure IA schematically illustrates a generic planar construction of a wireless machine, and Figure IB schematically illustrates the use of backing iron to improve efficiency;

Figure 2 schematically illustrates a form of wireless linear induction motor; Figure 3 schematically illustrates an alternative arrangement of wireless induction motor;

Figure 4 schematically illustrates a number of planar machines of Figure 2 close-packed together;

Figures 5 schematically illustrates a linear actuator; Figure 6A schematically illustrates an alternative geometry of stator positioning;

Figure 6B schematically illustrates a wireless conductor assembly; Figure 7 schematically illustrates a circuitous track carrying a number of independent passive armatures; Figure 8 schematically illustrates the orthogonal superposition of electrically conductive sheets having conductor paths orthogonal to each other; Figure 9 schematically illustrates a low cost linear machine; Figure 10 schematically illustrates another low cost wireless linear machine; Figure 11 schematically illustrates a wireless induction rotary disc motor; Figure 12 schematically illustrates a robust disc induction motor; Figure 13 schematically illustrates a lightweight, low cost, large diameter wireless motor;

Figure 14 schematically illustrates an alternative wireless induction machine having a more conventional shape; Figure 15 schematically illustrates an example structure of wireless electrical system for a rotary induction machine;

Figure 16 schematically illustrates a multi-phase cylindrical linear induction motor;

Figure 17 schematically illustrates part of the stator of the linear motor of Figure 16;

Figure 18 schematically illustrates a wireless machine capable of acting simultaneously and independently as both a linear and a rotary actuator;

Figure 19 schematically illustrates a double-action machine working on both permanent magnet and induction principles; and Figure 20 schematically illustrates the magnetic part of the armature of the machine of Figure 19. Description of Example Embodiments

Figure IA is a schematic diagram showing a generic planar construction of all the wireless machines subsequently described. Metal laminae 1 are incised with conducting paths that alternate in direction with a regular spatial period and are covered with an insulating layer such as a varnish. An electrical phase "winding" is constructed from a number of such laminations, being laid one upon another with faces alternating and being electrically joined at alternate ends, so as to form a continuous electrical path for each phase. In this illustration, by way of example only, each phase consists of four layers. It will be understood, however, that the number of layers in each phase may be chosen to suit the particular machine specification and is not otherwise limited or defined.

The width of the gap incised between each conducting path of the laminae 1 is determined by the number of electrical phases in the machine to be energised. In this example there are three phases and so the gap between the conducting paths is twice the width of the conducting paths themselves. If there were four phases, the incised gap would be three times the width of the conducting layer, and if two phases the gap would be equal to the width and so on. By this arrangement it is possible to nest and bond the phases together to form a continuous planar conductor 3 in which the phases overlap each other only at the ends of the nested conductors, away from the active region of the motor.

A passive conducting plate 4 is arranged to lie in a plane adjacent and parallel to the plane of the nested laminations of the wireless stator. When the phases of the planar laminated conductors 3 are correctly energised with alternating current, the effect is to produce a travelling magnetic field pattern in the plane of the conductors, which extends orthogonal to that plane to intersect the conducting plate 4. This has several effects upon the plate 4 in accordance with Lenz's Law. The first is to induce electric currents to flow in the plate 4, the currents being of the appropriate amplitude and direction as to tend to cancel the travelling magnetic fields by which they were caused. The second effect is to create a force on the plate 4 tending to move it along with the magnetic field pattern that causes the induced currents (so that there would be no relative motion between them and therefore no induced currents). That is to say, the plate 4 is effectively dragged along by the travelling magnetic fields produced in the wireless conducting laminations 3. However, it will be appreciated that the plate 4 cannot achieve the same velocity as that of the travelling magnetic field, since if it did there would be no relative velocity between them and no eddy currents would be induced.

Another effect of the travelling magnetic field is to create a repulsive force between the plate 4 and the energised conductors 3. This is because the magnetic field intensity falls with the degree of separation between the passive and the energised conductors, and the energy of the system is therefore reduced as the passive plate 4 moves away from the wireless conductors 3. The levitation effect might be used with advantage, for example, when a very low friction electrical actuator must operate in a vacuum and a gas levitation system cannot be employed. The effect might also be used to raise the armature clear of high-friction material on the surface of either or both parts of the machine, the high-friction material causing the armature to be braked when the machine is de-energised. Figure IB shows how the efficiency of the coupling of the travelling magnetic field with the passive conducting plate may be improved by the use of backing iron, hi this diagram the basic parts are numbered with the same convention as for Figure IA, but a "backing iron" plate 46 is placed in contact with wireless conductors 3 and a second plate of backing iron 45 is affixed the rear of the passive conductor 4. The principal effect of the plate 46 is to increase greatly the flux density of the travelling magnetic wave caused by phased alternating currents in the wireless conductors 3 and thus to increase the strength of the eddy currents induced in the passive conductor 4. The addition of the backing iron plate 45 reduces the reluctance of the magnetic flux path around the wireless conductors 3 and further increases the flux linking with the passive conductor 4. It also establishes a direct magnetic coupling between the travelling magnetic field pattern in 3 and the passive plates 4 and 45. Provided that the limiting force is not exceeded, there is no longer any need for a continuous phase slippage between the travelling magnetic field pattern and the passive plates, so that the machine may act synchronously without eddy current losses in 4 or 45.

It should be noted, however, that unless preventative measures are employed to obstruct eddy currents, these will be induced in the iron 46. It should also be noted that there is now a strong magnetic attraction between the wireless conductor assembly

3, 46 and the passive part 4, 45 when the machine is energised, which overcomes the repulsion of the passive conductor plate 4 by the travelling magnetic field of 3.

It should also be noted that it is possible to replace the passive conducting plate

4 with a layer of permanent magnets having a spatially-alternating polarity matched to that of the conducting phases 3. The resulting machine is a synchronous or brushless servomotor that has been described in our earlier patent application GB 0515313.5 and others subsequent thereto.

Figure 2 shows a diagrammatic cross section of a form of wireless linear induction motor in which the passive conducting plate assembly is the armature and travels along a fixed powered stator. hi this illustration the wireless conductors 3 are mounted in spines 8 along each edge, the spines 8 also carrying bearings 6 that support a framework 7 that moves parallel to the travelling magnetic field. The framework carries the passive conductors 4 and their backing iron plates 45. Figure 3 shows a diagrammatic cross section of an alternative arrangement in which the frame 7 is enclosed and forms the powered stator of a linear induction machine. Two sets of wireless conductors 3 are affixed opposite sides of the machine and may carry iron or mild steel backing plates 46. The passive armature 4, 45 travels in longitudinal bearings 6, parallel to the axis of the travelling magnetic field in the wireless conductors 3.

Figure 4 is a diagrammatic cross-section showing how a number of planar elemental machines of the type shown in Figure 2 may be packed closely together and driven in synchronism so as the produce a high-thrust linear induction motor. Each assembly of powered laminated conductors 3 is affixed a stator plate 49 and each passive conducting fin (or a convenient part thereof 45) is affixed the armature plate 48. The plate 48 moves relative to the plate 49 parallel to that plate and to the axis of the travelling magnetic fields produced by the powered assembly of laminations 3. It will be understood that the upper side of each of the powered conductors 3 runs in a guide bearing affixed the armature plate 48 and that the lower side of each of the passive elements 45 runs in a guide bearing affixed the stator plate 49. The guide bearings are here omitted for clarity.

It will be understood that the powered stators 3 of the multi-element machine need not be continuous and that the length of the passive conducting elements 4 of the armature may be designed so that in any position at least one stator section may act upon them. It will be further understood that in certain applications the assembly of powered parts 3 may be configured as the armature and the assembly of passive parts 4 may be configured as the stator.

Figure 5 is a diagrammatic cross section of a linear actuator, which shows how the principles described in relation to Figure 4 may be extended to produce a compact high-thrust wireless cylindrical induction motor. In this illustration the powered elements 3 are affixed the , inner surface of cylinder 49 via spines 8 and the passive conductor assemblies 4, 45 are affixed the central thrust tube 48. The powered elements 3 are driven in synchronism (e.g. by series connection) so as to induce forces in each of the passive elements 4, 45 the sum of which acts on the central thrust tube

48. It will be understood that guide bearings for the powered laminations 3 may be affixed the outside of the thrust tube 48 and that guide bearings for the passive conductors 4, 45 may be affixed the inside of the outer casing 49. It should also be noted that neither the thrust tube nor the outer casing needs to be made from ferromagnetic material and that, should either of the cylinders 48 or 49 be made of plastic, the guide bearings for the elements 3 or 45 may simply consist of grooves in that plastic.

It will be further understood that in certain applications the thrust tube 48 may with advantage be configured to carry the powered elements 3 and the passive conducting elements 4 may be affixed the outer casing 49.

Figure 6A shows how the velocity of the travelling wave may be increased by changing the geometry of the stator patterning. This has several design advantages for applications of linear actuators in the unidirectional acceleration of industrial objects or in the launching of aircraft, UAVs, UUVs or other military devices. In this illustration, sector 13 of the wireless stator has a longer spatial separation between the transverse conductors than that of sector 12, which in turn has a spatial separation longer than that of sector 11. Thus an alternating current in sector 13 produces a travelling magnetic field of the same frequency with a velocity greater than that of sector 12, which velocity is in turn greater than that of sector 13. For clarity, only one of the laminations of each sector is shown, but it will be understood that each sector actually consists in a plurality of identical laminar phase conductors which are nested to form a continuous metal sheet having an insulating pattern incised therein.

Although the illustration shows a wireless stator having a number of separate sectors with differing spatial periods, it will be understood that in the alternative the stator can be so constructed that the spatial period of the conductors (and therefore of the travelling magnetic field) is changed smoothly and progressively along the machine axis within each one-piece lamination.

Figure 6B shows a typical wireless conductor assembly 3, of the form that might be employed in several of the inventions described herein. It is to be noted especially that the completed and bonded assembly has the general characteristics of a continuous metal sheet having a thin cross section, so that: -

The completed conductor assembly may be smoothly twisted along its axis if required, so as to change the orientation of a load with respect to its linear position, for example. In this case, the armature rotates around its own locus of motion in a predetermined way according to its absolute position.

Using the appropriate metalworking tools, the completed and functional conductor assembly may be pressed, rolled or otherwise deformed to any chosen profile, such as a long U-section or a large-diameter circle. It may also be rolled or pressed so as to conform to the inner or outer surface of a cylinder or sphere.

Though here shown uniformly flat for simplicity of illustration, the planar conducting assembly of laminations that is characteristic of our invention is not so restricted. The power output of an induction machine using a planar wireless electrical system is a function (inter alia) of the effective area of the two conducting surfaces. With some significant advantage in several applications, therefore, the surfaces of both the laminations 3 and of the passive conducting plate 4 may be deeply corrugated (with matching profiles) transverse to the motion axis of the machine.

Figure 7 shows how the powered wireless stator 3 may be formed into a circuitous track that carries a number of independent passive armatures 7. The track is divided into a number of independently-energised segments that are here shown as A, B, C, D, E and F. If the wireless track 3 is horizontal it is possible, for example, to move each of the armatures 7 to a different manufacturing or assembly work station and to cause them to halt at precisely-defined positions. As a second example, using the same principles, it would be possible to affix the armatures 7 to elevator cages and to control several cages independently in the same vertical shaft.

Figure 8 shows how the planar construction of this invention allows machines to be constructed that can act simultaneously and independently in two orthogonal axes.

Consider two wireless electrical conducting sheets 14 and 15 that have the conducting paths orthogonal one to the other. For clarity of orientation, we show only one lamination of each sheet but each of the conducting sheets actually has the general form shown here as 3. The two parts of the stator 14(3) and 15(3) are laid one upon the other and upon a plate of backing iron 46 and energised separately and independently so as to produce travelling magnetic fields of independent strength and velocity. The passive conductor plate 4 and its backing iron 45 will therefore experience a net force that may be vectored instant by instant as required by the application. These principles may be applied to other forms of actuator/motor, as later described herein.

Figure 9 is a diagrammatic cross section of a low cost linear machine that may be constructed according to this invention. The wireless conducting assembly 3 is first pressed into a U section and then snapped into a mild steel U channel 46, which acts as the backing iron. The overlap region of the phases 10 (which is equivalent to the "end windings" of a conventional machine) fits into prepared channel near to the open end of the mild steel unit 46. The conducting plates of the armature 4 are mounted to a central thrust plate 45, which also acts to reduce the reluctance of the magnetic circuit and which runs in the axial bearings 6.

Figure 10 is a diagrammatic cross section of a typical wireless linear machine of minimal cost, suitable for use in applications where the duty cycle is very low and electrical efficiency is not paramount. Such uses might, for example, be for the movement of curtains or sliding doors in domestic premises. In this case the conducting laminations used for the stator assembly 3 are made of mild steel, so that they also exhibit a low magnetic reluctance. The completed conductor assembly is then pressed or otherwise deformed into a U channel and snapped into a plastic extrusion 17, which also has a recessed channel for the "end windings" 10. The plastic extrusion carries a bearing channel 6 at its base and a further snap-in top bearing of similar form. The passive inductor plate 4 may also be constructed of mild steel to minimise the reluctance of the magnetic circuit between the sides of the stator assembly 3.

Figure 11 shows in a diagrammatic cross section how the invention may be applied to the construction of very low cost wireless induction rotary disc motors. In most existing rotary disc motors the armature consists in a printed circuit that acts as its own commutator as part of a DC machine using permanent magnets on either side. In contrast, we show by way of example a very low cost brushless multi-phase machine in which the armature is a simple passive disc 4 driving an output shaft 19 that runs in bearings 6. The laminations of the wireless stator 3 and their end windings 10 are in this case cut or punched from mild steel sheet and assembled as two disc-shaped halves of a multi-phase electrical system. The halves of the wireless stator are then laid and bonded into the corresponding halves of the plastic casing 17. The electrical power connections to each half of the stator (not shown) are appropriately welded to the end windings 10 and brought out of the casing to a suitable termination or socket.

Figure 12 shows a diagrammatic cross section of a similar but more robust disc induction motor, in which the casing is of mild steel and also acts as the backing iron 45 to the conducting laminations 3 of the wireless motor. The method of assembly is closely similar to that described for Figure 11 above. Figure 13 shows a diagrammatic cross section of a lightweight, low cost large diameter wireless motor having a high torque for use in gearless applications. In this machine the assembly of wireless conductors is rolled into a circle and bonded to the inside of a mild steel backing cylinder 46. The passive conducting element 4 is also hi the form of a cylinder that is fitted to the outside of the mild steel backing element 45, which is held in the rotating structure 31, coupled to the output shaft 19. The top and bottom plates 17 carry bearings 6 m which the shaft 19 rotates, being separated from the stator conductors 3 by the real air gap 30. It is to be noted that the body of the armature (passive conducting cylinder) is hollow and itself contains no electromagnetic parts. It should be noted that it is possible for the period of the magnetic wave rotating in the conductors 3 to be made small by the design of the laminations, so that the motor may still produce a useful torque by induction whilst rotating at low speed.

Figure 14 shows a diagrammatic cross section of an alternative wireless induction machine having a more conventional shape. In this machine the conducting laminations 3 are rolled into a cylinder and affixed the inner surface of a ferromagnetic cylindrical casing 46. The passive conductor 4 is of cylindrical form and is affixed the outside surface of a ferromagnetic cylinder 45. It is coupled by the structure 31 to the output shaft 19, which rotates in bearings 6 that form part of the motor end pieces 17, there being a real separation 30 between the armature 4 and the stator 3. It is to be noted that a lightweight and compact machine of this form cannot be built using conventional wire coil techniques.

It should also be noted that the minimal-cost design techniques of Figure 10 can also be applied to this form of rotary motor. That is to say, the outer ferromagnetic cylinder 46 and the inner ferromagnetic cylinder 45 may be eliminated if the wireless powered stator conductors 3 and the passive conducting armature 4 are constructed from iron or mild steel.

Figure 15 is a more detailed diagram showing the structure of the wireless electrical system 3 for a rotary induction machine. It is to be noted that the electrical conducting paths in the active region are always parallel to the axis of rotation and that the phases overlap at each end of the motor. Figure 16 is a diagrammatic cross section of a typical multi-phase cylindrical linear induction motor using the principles of this invention. As for a rotary motor, the electrical system 3 is rolled into a cylinder and bonded to the inside surface of a ferromagnetic (e.g. mild steel) casing 46 that acts as the backing iron. The passive conducting element 4 is also cylindrical and forms part of the armature or piston structure 31 that carries the inner iron or mild steel backing iron 45.

The thrust tube output element 19 is usually arranged to pass through a sliding gas pressure seal and bearing unit 6 in the end piece of the casing 17 and to carry another bearing ring 6 affixed the armature or piston by which it is guided in its reciprocating motion by contact with the carbon fibre lining tube (not shown) within the cylindrical electrical system 3. The chief advantage of the gas pressure seal in the main bearing unit is that the thrust rod may thereby act as the moving element of a gas spring that is designed to support the deadload whose mass is to be positioned or vibrated by the linear motor or ram. The lower guide bearing need not be sealed against gas flow. It will be understood that there may be no thrust tube element provided, but instead the passive armature may be provided with a sliding fluid seal to the liner of the array of powered conductors, so as to act as a pump or compressor, for example.

It will be further understood that for vibration applications the armature may be free to move as an inertial object within the stator, the reaction forces then being transferred to the load via the stator casing.

Figure 17 shows part of the stator of a linear motor of the type described in relation to Figure 16 above. It is to be noted especially that, in contrast to the rotary motor, in a linear motor the electrical current paths are circumferential and orthogonal to the central axis of motion and that the phases overlap in a region parallel to the central axis. It will be understood that the overlaps or "end windings" produce a magnetic discontinuity that must be matched by an identical discontinuity diagonally opposite, so as to maintain magnetic symmetry around the central axis.

Figure 18 is a diagrammatic cross section that shows how the relative orthogonality of the wireless conductors for rotary and linear motion of a cylindrical machine can be employed in the design of a machine that can act simultaneously and independently as both a linear and a rotary actuator.

The general form of a typical combined linear and rotary machine might be similar to that of Figure 17 above, in which the numbered items have the same identities as before. However, the laminations of the wireless electrical system now consist of two layers directly superimposed (as in Figure 8). To produce linear action, layer 3 is energised, whilst to produce rotation layer 3A is energised. The layers may be driven independently by different electronic drives, so that each can act simultaneously without mutual interference. Figure 19 is a diagrammatic cross section of a similar double-action machine, which shows how one of the machine axes can be driven as a brushless permanent- magnet synchronous or servomotor, whilst the orthogonal axis can be driven as an induction motor. The structure is broadly similar to that of Figure 18 above and the reference numerals apply to the same components. In this case, however, the armature consists in an array of permanent magnetic fields 35, to the outer surface of which a passive conducting sleeve 4 is affixed. For this illustration we have chosen to use the permanent magnet array in combination with the wireless conductors 3 to form part of a brushless servomotor producing linear motion. It will be understood that the choice is arbitrary prior to actual construction and we might have shown the equivalent alternative design in which the permanent magnet assembly acts with the wireless stator 3 A to produce rotary motion.

Figure 20 is a more detailed illustration of the magnetic part of the armature 35. It is to be noted that the magnet rings are designed to produce an axially-alternating radial magnetic field having the same axial dimensions as the corresponding electrical conductors of the wireless stator (see Figure 17).

The principal advantages provided by embodiments of the present invention include the following:

1) The replacement of heavy copper wire coils in slots orthogonal to the air gap by laminar aluminium conductors within and parallel to the air gap reduces the weight, material cost and overall dimensions of the machine.

2) The use of induction techniques removes the need for permanent magnets, greatly reducing the cost and eliminating dangerous inter-magnetic forces during assembly. 3) The replacement of many wound coils by a small number of patterned conducting laminae increases reliability and reduces the costs of assembly and testing.

4) It has been common practice hitherto to construct a long-stroke linear electric actuator by making the armature that part of the machine to which power is supplied - and using a magnetic array as the passive stator. It will be understood that a continuously-flexing power cable must be used to bring current to the moving armature. In the case of an induction machine the stator carries the conducting element in which eddy currents are induced by the travelling magnetic fields of the armature. The use of wireless motor technology completely changes the economics of the machine and allows a much better and more reliable design, in which power is supplied to a low-cost, fixed stator and the moving element is lightweight and passive.

5) The wireless induction motor is planar and produces its force/torque over an area that is much larger than its thickness transverse the air gap. This unusual property allows the machine to be configured in topologies that are especially helpful in certain applications, but which would be impossible for any machine of conventional construction.

6) In that the plane of the wireless electrical system is not restricted to being flat, but may be smoothly curved in several axes at the same time, the locus of motion of the armature can be arranged to follow any chosen path suited to the application.

7) The planar construction of a wireless electrical machine allows the conductors to be driven very hard when necessary, because the thermal conduction between overlapping laminae is greater than that between adjacent insulated copper wires of conventional design and so excess heat can escape more easily, without producing "hot spots". Further, the "copper loss" (the total heat produced in the electrical conductors by reason of their ohmic resistance) is spread over a large area, reducing the working temperature of the machine surfaces for any given drive current. 8) The wireless induction motor is of very simple design and construction, which allows the manufacturing quality and the operational reliability of the machine to be increased by the corresponding reduction in complexity.

9) The technology is fully scaleable and may be applied to electrical induction machines having a wide range of sizes and power outputs. 10) Exceptionally low-cost linear wireless motors can be built for domestic applications, such as moving curtains, shutters or sliding doors.

11) Exceptionally high thrust linear motors can be built by the close grouping of many individual elemental machines. It is especially possible to group such machines within a cylindrical casing so as to form an actuator that is similar to a fluid ram. 12) The thrust tube of an electromagnetic ram can be sealed at one end of the cylinder (or the cylindrical armature may be slideably sealed to the lining sleeve of the stator) so as to combine the electromagnetic action of the piston with that of a gas spring, for example. A variety of methods are described above by which a wireless electrical machine using planar powered laminar conductors can be used to construct a range of induction motors, having linear, rotary and combined, independent actions. The planar laminated construction allows several new motor topologies and includes the advantages of robustness, low-cost, lightweight simplicity, reliability and efficiency. Various further aspects and features of the present invention are defined in the appended claims. Various modifications can be made to the embodiments herein before described without departing from the scope of the present invention.

Claims

1. An electrical machine having: a first part comprising at least one assembly of insulated laminar conductors in which a pattern of current paths is defined and by which a plurality of alternating phase-related electric currents can be applied to produce a travelling magnetic field of regular alternating polarity; and a second part comprising at least one electrical conductor closely adjacent to the first part and intersecting the travelling magnetic field, the second part being physically separated from the adjacent surface of the conductors of the first part by an air gap and being arranged to move with respect to the first part along the locus of the travelling magnetic field when the plurality of alternating phase-related electric currents are applied to the insulated laminar conductors of the first part.

2. An electrical machine according to claim 1, wherein the first part comprises two independently-powered sets of wireless laminations for generating respective independent travelling magnetic fields, the independent sets of wireless laminations being arranged so that their conducting paths are orthogonal and the resulting force on the conductor of the second part is the vector sum of that generated by the two independent travelling magnetic fields.

3. An electrical machine according to claim 2, wherein the conductors of the first and second parts are of cylindrical or part cylindrical form, and wherein one of the two independently-powered sets of wireless laminations is arranged to produce an axial travelling magnetic field in a direction parallel to the central axis of the cylindrical form to cause relative linear motion between the first and second parts, and the other of the two independently-powered sets of wireless laminations is arranged to produce a circumferential travelling magnetic field to cause relative rotary motion between the first and second parts.

4. An electrical machine according to claim 2, wherein the conductors of the first and second parts are of spherical or part spherical form, and wherein one of the two independently-powered sets of wireless laminations is arranged to produce a latitudinal travelling magnetic field to cause relative latitudinal motion between the first and second parts, and the other of the two independently-powered sets of wireless laminations is arranged to produce a longitudinal travelling magnetic field to cause relative longitudinal motion between the first and second parts.

5. An electrical machine according to claim 1, wherein the assembly of insulated laminar conductors comprises a set of transverse current paths transverse the axis of relative motion, the spatial period of the transverse current paths varying along the axis of relative motion.

6. An electric machine according to claim 5, wherein the assembly of insulated laminar conductors comprises at least first and second sectors, the transverse current paths of the first sector having a different spatial period along the axis of relative motion than the second sector.

7. An electrical machine according to claim 5, wherein the transverse current paths of the assembly of insulated laminar conductors has a smoothly varying spatial period along the axis of relative motion.

8. An electrical machine according to any preceding claim, in which each of the electrical phases of the first part comprises at one or more electrically conducting laminae that are overlaid, end-connected and bonded to form an integral, self-supporting mechanical structure.

9. An electrical machine according to claim 8, in which the dimensions of the space between defined conducting paths transverse the axis of motion of each phase of the first part is such that the transverse conductors of the remaining phases may be laid in the space alongside one another and alongside the conductors of the first phase in the same plane.

10. AB electrical machine according to claim 9, in which axially-directed sections of grouped conducting laminae of each phase of the first part are arranged to overlap the grouped conducting laminae of the other phases in an inactive region away

11. An electrical machine constructed according to claim 10, in which thin, insulated ribbon conductors or tapes are interspersed with the overlapping phases of the first part, the ribbon conductors or tapes being connected to ground to reduce the inter-phase capacitance.

12. An electrical machine according to claim 9 or claim 10, in which the laminar conducting phases of the first part are flat or smoothly curved upon first assembly are then pressed, rolled or otherwise deformed to a required profile by appropriate metalworking techniques.

13. An electrical machine according to claim 9 or claim 10, in which the spatial period of the transverse current paths in the laminar conductors of the first part is selected in combination with the maximum alternating frequency of the currents to define a maximum linear velocity for the travelling magnetic field.

14. An electrical machine according to any preceding claim, in which the surface areas of both the powered laminar conductors of the first part and the passive conducting plate of the second part are increased by the use of matched corrugations transverse the axis of motion.

15. An electrical machine according to any preceding claim, in which the passive conducting plate of the second part is arranged to be levitated by repulsion of the travelling magnetic field to provide a frictionless bearing or to release a brake.

16. An electrical machine according to any preceding claim, in which a ferromagnetic plate is arranged to conform to the topology of the laminated surface of the powered assembly of patterned conducting laminations of the first part and is affixed thereto, upon the surface distant from the air gap.

17. An electrical machine according to any preceding claim, in which a ferromagnetic plate is arranged to conform to the topology of the laminated surface of the passive conductor of the second part in the magnetic field region and is affixed thereto, upon the surface distant from the air gap.

18. An electrical machine according to claim 16 or 17, in which either or both ferromagnetic plates are arranged by choice of material or by the segmentation or lamination of the same, to have a high electrical loop resistance in a direction parallel to the transverse conductors of the first part.

19. An electrical machine according to any preceding claim, in which the powered laminations of the first part are constructed from ferromagnetic material.

20. An electrical machine according to any preceding claim, in which the powered laminations of the first part and/or the passive conductor of the second part are fabricated from a material other than aluminium or copper, the material being chosen for its mechanical strength, for its magnetic properties or for its corrosion resistance.

21. An electrical machine according to any preceding claim, in which the powered laminations of the first part and/or the passive conductor of the second part are fabricated from a flexible material.

22. An electrical machine according to any preceding claim, in which the powered laminations of the first part form part of the stator and the passive conducting plate of the second part forms part of the armature.

23. An electrical machine according to any preceding claim, in which the powered laminations of the first part form part of the armature and the passive conducting plate of the second part form part of the stator.

24. An electrical machine according to any preceding claim, in which there is at least one conducting pattern within the at least one powered laminar array of the first part that takes the form of a spoked wheel having broad spokes abutting one another and filling the whole area of the wheel, the laminar array being energised by a plurality of phased electric currents so as to produce a multi-pole rotating magnetic field.

25. An electrical machine according to claim 24, in which there is at least one conducting disc of the second part, which may be caused to rotate around an axis orthogonal to the conducting elements and passing through the centre of the spoked wheel to form a rotary wireless induction motor.

26. An electrical machine according to any preceding claim, in which the planes of the conductors of the first and second parts conform to any smooth three- dimensional shape.

27. An electrical machine according to any preceding claim, in which the locus of motion follows a smooth curve in three dimensions.

28. An electrical machine according to any preceding claim, in which the powered laminations of the first part are included in the stator and the distance through which the armature travels is more than three times its length, so that the stator may be divided into a plurality of independently-powered and controlled sections.

29. An electrical machine according to claim 28, in which a plurality of armatures are provided, the number of which is not greater than the number of independently-powered and controlled sections of the stator.

30. An electrical machine according to any preceding claim, in which the locus of motion of the aπnature(s) is circuitous.

31. An electrical machine according to any preceding claim, in which the powered sections of the stator are not continuous, but in which the length of the armature is sufficient to ensure that at least one powered section of the stator is always positioned to act upon the armature.

32. An electrical machine according to any preceding claim, in which the armature rotates around its own locus of motion in a pre-determined way according to its absolute position.

33. An electrical machine according to any of claims 1 to 26, in which the conducting planes of the first and second parts conform in whole or in part to the shape of a cylinder.

34. An electrical machine according to claim 33, in which the armature travels within the stator.

35. An electrical machine according to claim 33, in which the armature travels along the outer surface of the stator.

36. An electrical machine according to claim 33, in which the powered wireless laminations of the first part are rolled to fit within a ferromagnetic cylinder, in such a way that the transverse conductors thereof are circumferential within the cylinder and around the central axis, producing a multi-pole magnetic field travelling parallel to the central axis.

37. An electrical machine according to claim 35, in which the armature includes a passive conducting cylinder that is close-fitting to the cylindrically-formed powered laminations of the first part and is free to move along the axis of the cylinder.

38. An electrical machine according to claim 33, in which the powered wireless laminations of the first part are rolled to fit within a ferromagnetic cylinder and in which the transverse conductors thereof lie parallel to the central axis, producing a multi-pole magnetic field that rotates around the central axis.

39. An electrical machine according to claim 38, in which the armature includes a passive conducting cylinder that is close-fitting to the cylindrically-formed powered laminations of the first part and is free to rotate around the axis of the cylinder.

40. An electrical machine according to claim 39, in which the cylinder is hollow and has a diameter which is substantially greater than its axial length, so as to produce a large gearless torque.

41. An electrical machine according to claim 40, in which the circumferential spatial period of the conductors of the first part is small, so as to produce a high torque at a low rotational velocity.

42. An electrical machine according to claim 37 and claim 39, in which the first part comprises two independently-powered sets of wireless laminations, each rolled to fit within the ferromagnetic outer casing, one producing axial travelling magnetic fields to perform linear actuation and the other producing circumferential travelling magnetic fields to perform rotary actuation.

43. An electrical machine according to claim 34, in which the armature carries an array of permanent magnets so that one of the axes operates as a permanent- magnet brushless servomotor whilst the other operates as an induction machine.

44. An electrical machine according to claim 42, in which the planes of the conductors of the first and second parts conform in whole or in part to the surface of a sphere and in which the armature is moveable latitudinally or longitudinally by independent stators.

45. A high-thrust linear wireless motor in the form of a cylindrical ram which is constructed of a plurality of individual linear machines according to claim 10, the linear machines being packed around a central thrust tube and driven in synchronism.

46. A wireless cylindrical linear motor in the form of a ram having an emerging thrust tube having a sliding gas seal at a top plate, so that the armature of the second part may act independently and simultaneously as part of a gas spring and as an electromagnetic actuator according to claim 10.

47. A wireless cylindrical linear motor according to claims 45 or 46, in which the powered laminations of the first part form elements of the stator and the passive conducting plates of the second part form elements of the armature.

48. A wireless cylindrical linear motor according to claims 45 or 46, in which the powered laminations of the first part form elements of the armature and the passive conducting plates of the second part form elements of the stator.

49. An electrical machine according to claim 37, the armature of the second part having no external connection and being slideably sealed to the lining of the stator of the first part so that the armature may act as a reciprocating pump or as the force- producing part of at least one gas spring.

50. An electrical machine according to claim 37, the armature of the second part having no external connection and being driven as an inertial object so as to impart vibration to an external load through the reaction of the body of the cylinder.

51. An electrical machine according to any preceding claims, wherein the insulated patterned laminar conductors of the first part have no substrate and together cover the complete surface of the air gap. _N