WO2005031947A1

WO2005031947A1 - Electrical machines

Info

Publication number: WO2005031947A1
Application number: PCT/AU2004/001344
Authority: WO
Inventors: Paul Lipa
Original assignee: Rydberg Pty Ltd
Priority date: 2003-10-01
Filing date: 2004-10-01
Publication date: 2005-04-07

Abstract

The invention includes a winding (1) for an electrical machine comprising turns of current conducting material, having within it at least one fold that has substantially rectilinear portions (4) joined by a middle portion. The invention further includes a rotor having an array of at least two sources of magnetic fields, the magnetic flux of a magnetic field projecting from each side of the rotor, the polarity (3) of the magnetic flux of adjacent magnetic fields at a side of the rotor alternating within the said array. The invention also includes electrical machines operable as motors or generators depending on the folds of the windings.

Description

Title

Electrical Machines

Field of the Invention This invention relates to electrical machines, in particular, electrical motors and generators.

Background

An electrical machine, particularly an electrical rotating machine, may have elements arranged to allow it to operate either as a motor or as a generator for converting energy between mechanical and electrical forms. The energy input to a generator and the energy output of a motor are both mechanical in nature, while the output of a generator and the input of a motor are electrical energy.

The conversion of energy in electrical machines between mechanical and electrical forms is achieved by interaction of magnetic fields, the function of which is to produce magnetic attraction and repulsion. This results in mechanical torque in a machine or the induction of voltages in coils of wire in a generator.

Rotating electrical machines include a rotatable rotor mounted on a shaft and a separate stationary stator. Each of the rotor and the stator is a source of a magnetic field. Each usually includes a core to conduct the magnetic flux generated in a winding. Current supplied to the winding produces the magnetic field.

There are limited materials suitable for the core that can conduct magnetic flux, the preferred material being iron. The use of iron is advantageous because it focuses the magnetic flux but iron has the disadvantage of being dense and adding considerable weight to a machine. Notwithstanding the effect of iron on magnetic fields, conventional designs of magnetic circuits result in considerable leakage of magnetic flux, which limits the energy conversion efficiency of a machine.

A winding for conducting electric current contains turns of metal wire around a core, the current in the turns causing the generation of a magnetic field about the winding. The wire must be insulated to result in suitable form and strength of the magnetic field. The insulation characteristically is not stable over long periods of time at the elevated temperatures that develop in an electrical machine during operation. There is generally an inverse relationship between the temperature of operation and useful life of a machine because of the effect of temperature on the insulating material.

Current electrical machines suffer from energy losses decreasing the efficiency of the devices. The efficiency of an electrical machine is calculated as the ratio of the output power relative to the input power, or as the ratio of the output energy relative to the input energy. Characteristically, the maximum efficiency of electrical machines is around 90 per cent. The electric motor and generator industries are continuously searching for ways to provide motors and generators with increased efficiency of energy conversion.

Losses of energy occur from electrical, magnetic, and mechanical causes. The lost energy is dissipated by conversion to heat and lost to the ambient environment and also causes the temperature and degradation of the insulation on the winding, which in turn, decreases the life of the machine.

Brief Description of the Drawings

In the drawings which illustrate preferred embodiments of the invention:

Figure 1 shows the location of magnetic fields in relation to current carrying conductors and magnets.

Figure 2 shows the interaction between magnetic fields and current carrying conductors.

Figure 3 shows plan views of the location of magnetic fields in relation to current carrying conductors with two configurations.

Figure 4 shows views of embodiments of windings of current carrying conductors.

Figure 5 shows in plan view the location of magnetic fields on adjacent rotors and stators of a motor.

Figure 6 shows the elements for an electrical machine that operates as a motor.

Figure 7 shows the arrangement of the elements in of a motor according to the invention. A portion of the motor is exploded to show the arrangement of the magnetic fields in the rotors and stators.

Figure 8 shows the energy output of an embodiment of the invention in operation as an electrical generator .

Summary of the Invention

The object of the invention is to provide a relatively lightweight device to efficiently convert energy between mechanical and electrical forms. The invention incorporates the surprising feature that including folds in the turns of a winding of an electrical machine constructed according to the invention does not require a core of heavy ferromagnetic elements to enhance the strength of a magnetic field associated with a winding.

In the invention there is provided a winding for an electrical machine, the winding including turns of current conducting material, the winding having within it at least one fold, a fold having substantially rectilinear portions joined by a middle portion. The winding may form a shape wherein folds are spaced substantially in a circumference of a disc. Alternatively, the winding may form substantially a cylinder in shape. Alternatively the winding may form substantially a rectilinear shape. In the winding of the invention the side portions of a fold angularly extend from the middle portion of the fold, the side portions defining an angle. The side portions of a fold may be substantially parallel. In the winding provided by the invention, the winding may include a plurality of folds, the sides of the folds being substantially parallel, a first fold having space side portions joined by a middle portion, and an adjacent second fold having substantially contiguous rectilinear side portions joined by a middle portion of minimal length. In the winding provided by the invention, the folds may be arranged in a pattern wherein a fold with space side portions alternative with a fold having contiguous side portions.

In an embodiment of the invention, suitable for operation as a motor, the machine includes at least one stator, at least on moveable rotor, and a shaft, the rotor having a two-dimensional array of magnetic fields of alternating polarities on each side, the winding including a plurality of folds, the sides of the folds being substantially parallel, a first fold having spaced side portions joined by a middle portion, and an adjacent second fold having substantially contiguous rectilinear side portions joined by a middle portion of minimal length.

In a further embodiment of the invention, suitable for operation as a generator, the electrical machine including at least one stator, at least one moveable rotor, and a shaft, a rotor having a two-dimensional array of magnetic fields of alternating polarities, the stator having a winding in form as herein described, a rotor and a stator arranged in close proximity, movement of the rotor inducing pulses of current in the winding of the stator.

The versatility of the invention is such that it is not restricted for use in rotating electrical machines. It may also be embodied in other electrical machines such as linear electrical machines.

The invention includes windings with folds of many configurations, the only limitation being that the winding includes rectilinear portions oriented to interact with passing magnetic fields.

The invention provides a method for converting electrical energy to mechanical energy, the method including the steps of establishing a two-dimensional array of at least two magnetic fields, adjacent fields being of opposite polarity; establishing a further magnetic field not in the array with one of its dipoles facing the array in the first step; establishing a second two- dimensional array of at least two adjacent magnetic fields, adjacent magnetic fields being of opposite polarity; matching the magnetic fields of the first and second arrays of magnetic fields so that facing magnetic fields of the first and second arrays are of opposite polarities, the second dipole of the further magnetic field facing the array in the third step; positioning the arrays of magnetic fields in proximity to each other so that the magnetic fields interact with the further magnetic field not in the array, a magnetic field in the first array established in the first step being attracted or repulsed by the magnetic field established in second step; causing the arrays of magnetic fields to move in relation to each other; and capturing the transformed electrical energy in mechanical movement.

The invention further provides a method for converting mechanical energy into electrical energy, the method including the steps of: establishing at first two-dimensional array of at least two magnetic fields, adjacent magnetic fields on a side of the array having opposite polarity; and passing the series of magnetic fields in close proximity to a side of a winding as described herein; and capturing the transformed mechanical energy in an electrical circuit.

The invention provides for an electrical machine including arrays of magnetic fields established in a three-dimensional stacked arrangement.

Detailed Description of the Drawings and Preferred Embodiment of the Invention

The invention is most easily understood with the reference to the accompanying figures. In Figure 1 it is shown the location of magnetic fields around current carrying conductors. The conductor is preferably an insulated wire of copper metal. Other conducting materials such as silver or aluminium may be used to carry current.

In Figure 1a, a rectilinear wire 1 is shown. When the wire carries current a magnetic field 2 forms around the wire. In Figures 1 b and 1c the wire 1 is folded into two different configurations of folds 3. It will be understood by those skilled in the art that the drawings showing a single wire is a representation of a winding including a plurality of wires.

In Figure 1b a fold in the wire 1 forms a substantially "U"-shaped curve, comprising three portions. A middle portion of each fold has a relatively broad semi-circular shape 3 and two substantially rectilinear side portions 4, the side portions 4 being substantially equally spaced. Adjacent folds share a side portion. The shape of the middle portion 3 of the wire connecting two side portions 4 can vary without affecting the function of the invention. For example, the middle portion 3 may be substantially flat and form right angles with the two side portions 4. It may form a very tight semi-circle as shown for one fold in Figure 1c (3a). Alternatively, the fold may form a substantially "V"-shaped curve where the middle portion forms an angle with the two rectilinear side portions. In the preferred embodiment of the invention the shape of the middle portion of all folds is substantially flat or the shape alternates between a very tight semi-circle and flat for adjacent folds, depending on the function of the machine, as will become evident in this description.

When the wire carries current a magnetic field forms, having opposite poles spaced perpendicular to the long axis of the conducting wire (Figure 1 ). A magnetic field of a first polarity N (shaded area) forms in a first volume including the space in the plane defined by a fold and a second magnetic field of a second polarity S (unsha ed area) forms in a second volume including the plane defined by an adjacent fold. It will be understood that the magnetic fields form in a volume and the areas illustrated in the figures represent the polarities of the portions of a magnetic fields in the plane of the wire.

Two magnetic fields only are shown in each of Figures 1a-1c for convenience. As will be seen in other figures the polarity of the magnetic fields in the volume including the plane in which the winding is found alternates between N and S in adjacent volumes between the rectilinear portions of the folds 3.

The configuration of folds wherein the middle portion of adjacent folds is substantially the same shape as shown in Figure 1b is most useful in an electric machine that operates as a generator. When magnetic fields from a separate source of magnetism pass in close proximity to the folds in the winding current is generated in the wire. The current can be drawn from the winding in an electrical circuit to do useful work..

In Figure 1c the wire is folded into a different pattern of curves. Some curves are similar to those shown in Figure 1b, having the middle portion form a broad semi-circle. In alternate folds the middle portion forms a very tight semi-circle, the result being that the rectilinear portions of the fold abut one another substantially along their full length.

The surprising effect of the configuration of the wire in Figure 1 c is to reduce the presence of magnetic fields of one polarity, causing magnetic fields in the volumes including the plane of alternate spaces defined by the wire to be of the same polarity. In Figure 1c the polarity all the magnetic fields is shown to be N. Reversing the polarity of the current causes a reversal in all adjacent magnetic fields.

The substantially eliminated magnetic field of one polarity resulting from the configuration of the winding is very advantageous when external magnetic fields pass in close proximity to the wire. Essentially no current is generated in the wire to counteract the effect of the magnetic fields in the spaces defined by the folds of the wire. This configuration of the folds is very advantageous for an electrical machine that operates as a motor. It will be understood that the polarity of the magnetic fields shown in Figures 1b and 1c is that opposite ends of each field that forms perpendicular to the direction of the current in the wire are opposite polarities. In Figure 1 d it is shown that interaction occurs between magnetic fields in three dimensions. A magnetic field with a first polarity N located in the space defined by a fold 3 can interact with magnetic fields located on either side of that space. A magnetic field with an opposite polarity S at one side will be attracted to said magnetic field while a magnetic field on the other side of said magnetic field will be repelled by said magnetic field. The possibility of interaction of a magnetic field in the fold of the wire simultaneously with two other magnetic fields in the invention advantageously exploits the energy contained in the magnetic field found in the space defined by the fold.

In Figure 2 is it further illustrated how magnetic fields and wires interact to achieve the invention. A basic interaction shown in Figure 2a is that the movement of a magnet 5 with a dipole magnetic field (shaded part a first polarity, unshaded part of a second polarity. In the figures any shaded magnetic fields would attract any unshaded magnetic field, and a shaded magnetic field would repel any other shaded magnetic field.) in the direction of the arrow past a straight portion of wire 1 produces a pulse of current in the wire, denoted by a positive + end and a negative - end of the wire. The amount of pulsed current produced in the wire can be increased by concurrent movement in the direction of the arrow of two facing magnetic fields matched to have opposite polarities passing on opposite sides of the wire 1 as illustrated in Figure 2b. The amount of pulsed current produced in the wire could be further increased if it were possible to move arrays (5a on a first side of the wire and 5b on a second side of the wire) of magnetic fields of alternating polarities past the wire concurrently as shown in Figure 2c, each dipole magnetic field moving in the direction of its arrow. In Figure 2c there are two, 2-dimensional arrays of magnetic fields, one on each side of the straight wire. The arrangement of the magnetic fields is such that alternating magnetic fields in an array on a side of the wire are of opposite polarity and the array on one side of the wire is paired or matched with the array on the other side of the wire so that facing magnetic fields are of opposite polarity. Such a configuration of moving matched arrays of magnetic fields in opposite directions past a rectilinear wire to produce current would be difficult to implement in practice. An embodiment of the invention provides a surprisingly simple and convenient means to overcome this problem and to produce current in the wire by including a fold formed by rectilinear side portions 4 on either side of a middle end portion 3 as shown in Figure 2d and moving the matched arrays of magnetic fields of opposite polarities 5a, 5b concurrently in the same direction as shown by the arrows in Figure 2e. A plurality of similarly shaped folds in the turns of a wire forms a winding and passage of the matched arrays of magnetic fields in a direction contemplated by the arrows adjacent the folds in the winding produces pulses of current in the winding. The pulses of current can be drawn off in an electrical circuit to do useful work. The speed of the movement of the matched arrays past the folds of the winding and the spacing of the folds placing of the matched arrays relative to one another determines the frequency of the pulses of current. It will be understood that the amount of current produced in a circuit will be proportional to the strength of the magnetic fields and the number of turns in, material of, and diameter of the wire in a winding.

In Figure 3 it is shown in plan view the configuration of a winding in a stator of a rotating electrical machine that operates as a generator (Figure 3a) and an electrical machine that operates as a motor (Figure 3b). It will be understood that, for convenience, the drawing shows just one wire in the windings 1 but in practice the wire would be wound through the folds in a plurality of turns from a starting portion 6 to an ending portion 7 of the wire.

Figure 3 illustrates the configuration of the folds of windings shown in Figures 1 and 2 would be embodied in rotating electrical machines. It will be understood that the invention is not limited to rotating electrical machines but includes configurations for linear machines, wherein the configuration of folds shown in Figures 1 and 2 when embodied in a stator would be linear wherein the rectilinear end portions 4 of the folds would be substantially perpendicular to a long axis of the stator in an axial configuration.

In Figure 3a it is shown that magnetic fields with a first polarity N alternate with magnetic fields of a second polarity S are induced in the spaces between the wire in the folds of the winding of the generator.

In Figure 3b it is shown the surprising distribution of magnetic fields of a stator for a motor when the wire of the winding is folded as initially shown in Figure 1c. Figure 3b shows that all of the apparent magnetic fields on a side of the stator will be of one polarity when the stator is energised. In operation, reversal of the current input and output at the starting portion 6 and ending portion 7 of the winding causes the polarity of all the magnetic fields to change to the opposite polarity. An advantage of the invention is that when the winding of a stator of a motor is in the configuration shown in Figure 3b, during operation of the motor there are minimised any excess magnetic fields induced by the interaction of the magnetic fields of the rotor with those of the stator which result in energy losses and consequent temperature increases and efficiency decreases of the motor. The invention includes configurations of the adjoined coaxial alignment of rectilinear or straight side portions of a fold 4 with some variation in that the side portions 4 will be arranged to be in as close proximity as possible, preferably being in contiguous and touching arrangement. The configuration will be limited by the ability to manufacture the winding to minimise the spacing of the side portions of a fold.

In Figure 4 it is shown configurations of the winding for stators for generators or for motors. In Figure 4a(i) it is shown that the winding of a motor, comprised of a plurality of turns of the wire, may be configured with the rectilinear end portions of the folds extending along spaced radii of a stator to provide radial magnetic flux 8 in an axial field. Figure 4a(ii) it is shown that the winding, comprised of a plurality of winds of the wire, may be configured with the rectilinear end portions of the folds spaced around a circumference of the stator to provide axial magnetic flux 9 in a radial field.

In Figure 4b(i) it is shown that the winding of a generator, comprised of a plurality of turns of the winding, may be configured with the rectilinear end portions of the folds extending along spaced radii of a stator to provide radial magnetic flux in an axial field 8. Figure 4b(ii) it is shown that the winding, comprised of a plurality of winds of the wire, may be configured with the rectilinear end portions of the folds spaced around a circumference of the stator to provide axial magnetic flux in a radial field 9.

In Figure 5 it is shown in planar view the locations and polarities of magnetic fields on rotating rotors and a stator during operation of a rotating electrical motor. The stator is energised with current to create magnetic fields as shown in Figure 3b. Figures 5(1) to 5(3) illustrate a first side of the stator and Figures 5(4) to 5(6) illustrate the opposite side of the stator. A rotor containing magnetic fields 10 is located above and below the stator 11 containing the winding 1. An advantage of the invention is the ease with which the strength of the motor can be increased by adding further stators and rotors in a stacked arrangement. Each stator is stacked with a rotor on either side of it.

The magnetic fields on the rotors 10, 10' are located so that they pass close by those of the stator 11 during movement of the rotors to optimise the conversion of the energy provided by the magnetic fields in the stator. The figure illustrates the movement of the magnetic fields of the rotors in a counter-clockwise rotation.

The arrangement of magnetic fields on rotors 10, 10' stacked with a stator is such that polarity of a magnetic field at a location on a rotor is opposite to the polarity of a magnetic field located on the stacked rotor on the opposite side of the stator. This is observed by comparing the polarities of the alternating magnetic fields of the rotors and stators illustrated in Figures 5(1) and Figure 5(4). In Figure 5(1) a first side of the stator 11 is shown to have magnetic fields between the folds 11 A being of a first polarity (shaded). In Figure 5(4) the opposite side of the stator 11 is shown to have magnetic fields between the folds 11 B being a second polarity (not shaded). In Figure 5(1) the polarity of a first magnetic field 10A (shaded) on a first rotor 10 facing the stator 11 is shown to be the same as the polarity 11 A of the facing side of the stator but opposite polarity to the opposite side of stator 11 B (not shaded) in Figure 5(4). In Figure 5(4) it is shown that the polarity of the corresponding magnetic field 10A' on the second rotor in close association with the opposite side of the stator 11 is the same as that of the side of the stator 11 B (not shaded) but opposite to that of the first magnetic field 11 A (shaded). The polarities of alternate magnetic fields 10A, 10B on the first rotor 10 is likewise opposite to the corresponding magnetic fields 10A', 10B' on the second rotor 10'. The magnetic fields of the rotors, being co-located in fixed relation on the shaft move in registration relative to the stator.

The result of the arrangement of magnetic fields on the rotors and stators is that all magnetic fields are repelled and attracted simultaneously by other magnetic fields in operation of the motor.

Magnetic fields 10 on the rotor are preferably provided by permanent magnets embedded in the rotor. The magnetic fields may be provided by other means. A permanent magnet that provides a single magnetic field may also be comprised of constituent smaller permanent magnets placed in close association so that the polarity of one side of each of the smaller permanent magnets providing a magnetic field 10 on a side of the rotor is the same. It is preferred that the long axis of each magnetic field on a rotor is approximately equal to the long axis of the side portions of a fold on the stator. The polarities of alternating magnetic fields 10 on a side of a rotor are opposite, designated for convenience as "N" and "S".

In Figures 5(1) to 5(3) it is shown the movement of a first magnetic field 10A on a rotor 10 and second magnetic field 10B on the rotor during counter-clockwise rotation of the rotor 10. The first magnetic field 10A is repelled by the magnetic fields 11 A on the stator during rotation.

The magnetic field at 10B is simultaneously attracted by the magnetic fields on the stator 11 A.

Attraction and repulsion occur for alternate magnetic fields. In Figure 5(4) to 5(6) it is shown that the corresponding magnetic fields 10A', 0B' on the rotor 10' are likewise repelled and attracted by the magnetic fields 11B at the opposite side of the stator.

The magnetic field of the stator 11 is produced when current provided by supply brushes 12 energises the stator 11.

In Figure 6a it is shown in cross section of the embodiment of the invention the mechanical elements in a motor structure at a radius of the housing 13 for the elements. In operation of the motor, the rotation of the rotor 14, which is attached to the long axis of a shaft 15, is the means of transfer of energy to do useful work by causing rotation of the shaft. The bearings 16 on the housing 13 allow rotation of the rotor 14 and shaft 15 with minimal energy loss through friction.

In Figures 6b and 6c it is shown in plan view the electrical elements of a motor. Figure 6b shows one side of a rotor 14 whereon magnetic fields are located generally around a circumference contained within the rotor 14. Magnetic fields of a first polarity (areas not shaded) 10B alternate with magnetic fields of a second polarity 10A (areas shaded). The magnetic fields are shown in the figures with boundaries for convenience only. The strength of the magnetic fields decreases with distance.

The source of magnetism in the magnetic fields is preferably provided by permanent magnets embedded in the material along radii of the rotor. Magnets with opposite polarities exposed at a surface of the rotor are embedded along substantially equally spaced radii to achieve the desired pattern of alternating magnetic polarities. In a preferred embodiment of the invention, a magnetic field located along a radius is comprised of a series of smaller permanent magnets lined up in contact with each other with all the same magnetic poles located at the same surface of the rotor.

The material of the rotor in which the magnetic fields are located may be metallic or other material. The preferred material is a resin that is strong but non-conducting and lightweight.

Figure 6c shows one side of a stator 1 1 wherein a winding of wire 1 is embedded. The winding follows a wider path along a circumference of the stator. Generally equally spaced sections of generally equal length of the winding follow a narrower circumference. Alternating with the sections of winding along a circumference 1 are folds 3 in the winding following along generally equally spaced radii of the stator. The winding has a start section 6 that is connected to one pole of a source of electricity and an end section 7 that is connected to the opposite pole of the source in operation of the invention. Connection of the winding to the source of electricity causes the winding to become energised and magnetised with one polarity at each surface of the stator. Reversing the polarity of the electricity at the start section 6 and end section 7 of the winding causes the reversal of the polarity of the magnetic field created along the winding. Optimal performance is achieved if the length of the folds 3 in the stator is substantially the same as the length of the magnetic fields in the rotor 10A, 10B.

The winding material may be any conducting material. The material is preferably copper, silver or aluminium. The arrangement of the folds in the winding provides a strong magnetic field with opposite poles on the opposite sides of the stator to interact with the magnetic fields of rotors adjacent the stator. There is surprisingly no need for a ferrous material in the core of the winding of the stator to enhance the strength of the magnetic field.

In Figure 7 it is shown the location of magnetic fields in the invention when the mechanical and electrical elements are combined in the housing. One stator 11 is situated between two rotors 14a, 14b so that opposites poles of magnetic fields on the rotors are adjacent those on the stator. This is clearly shown in Figure 7a wherein the N pole of a magnetic field on the rotor 14a is adjacent the S pole of a magnetic field on the stator 11. The corresponding N pole of the stator 11 is adjacent the S pole of a magnetic field of the second rotor 14b. The size of the magnetic fields on the rotors is substantially the same as the folds of the winding on the stator. The arrangement of rotors relative to the stator brings the magnetic fields into close association. The air gap between a rotor and the stator is preferably as small as is practicable. It can be seen in configuration of the magnetic fields on the rotors and stator in Figure 7a that magnetic fields along a diameter of the rotors 14a, 14b and stator 11 are arranged so that there is interaction (attraction in this case) between the fields on both sides of the stator and fields on the rotors. The substantially equal size and polarities of adjacent magnetic fields advantageously increases the amount of energy held in magnetic fields that can be converted to useful work. In particular, the energy in the magnetic fields on both sides of the stator may be converted for useful work. Frequently energy from magnetic fields in electrical devices in the prior art is converted to heat and is lost to useful work. The energy that is used to energize the stator and cause the formation of magnetic fields in the winding can be converted with high efficiency in the embodiment of the invention.

In Figure 7b an exploded view of the motor shows the arrangement of magnetic fields along radii of the rotors and stator, each attached at the centre to the shaft. It can be seen that the energized stator 11 has a magnetic field around the winding of a single polarity on one side of the rotor (shaded 16). The other side of the rotor, which is not shown in this view, has a magnetic field of the opposite polarity around the winding. Magnetic fields along alternating radii in the rotors 10A, 10B are of opposite polarities. In operation of the electrical machine the alternating magnetic fields of the sides of the rotors facing the stator either repel or attract the magnetic field of the stator, depending on whether polarity of a field of the rotor is the same as that of the stator (shaded 10A) or different from the stator (not shaded 10B). This interaction among magnetic fields occurs simultaneously between the magnetic fields of each rotor and the magnetic fields on either sides of the stator. The simultaneous attraction and repulsion of the magnetic fields causes the rotors to rotate the shaft and create torque, which can be converted to useful work.

The arrangement of rotors and stator shows that two rotors are combined with one stator. It is possible to increase the energy output of the motor by increasing the number of rotors and stators in a stacked arrangement. It is possible to double the energy output of the motor by adding a second stator and a third rotor on the shaft. Further additions of rotors and stators may be made to make further increases in the output of the motor.

EXAMPLE One embodiment of the invention is as follows. An electrical machine operable as a generator was constructed according to the invention herein described. The generator included a stator mounted and fixed on a steel shaft between two rotors within an aluminium housing similar to the machine illustrated in Figure 7. The stator included an aluminium frame on which was mounted a resin disc within which was embedded a winding comprised of turns of insulated copper wire following a route with a configuration substantially as illustrated in Figure 4b(i). The rotors were constructed likewise of resin discs mounted in frames rotatable on bearings around the shaft. The rotors included series of magnetic fields of alternating polarities extending along spaced radii, the magnetic fields located on each side of a rotor substantially as illustrated in Figure 7. The magnetic fields on the rotors were provide by series of permanent rare earth magnets embedded in the resin body so that the magnetic fields projected from the two faces of each the rotors, the poles of the magnetic fields were oriented so that the polarity of adjacent series of magnets projecting from radius along a side of the rotor alternated as shown in Figure 7(b). No metal core was provided in the stator, resulting in the whole apparatus weighing about 9 kg.

Mechanical energy to the generator was provided by a variable speed motor coupled with the shaft of the generator. An electrical circuit was completed by connecting input and output wires of the generator with input and output connections of an electric heating coil suitable for heating small amounts of water to boiling temperature. The input energy and output energy of the generator were measured firstly, by measuring the input current to the motor and the output energy as the change in heat content of a small, 680 ml, water bath. A series of trials was undertaken wherein the starting temperature of the water bath was measured, the rotor was rotated by the coupled motor at 15 to 50 cycles per second for time periods of 100 s to 937 s, which was the time for the temperature of the water bath to rise from a base temperature near room temperature of approximately 18°C to a temperature between 50°C to 100°C in a particular trial. The results of 10 trials are illustrated in Figure 8, which shows that the power output for this particular configuration ranged from approximately 150 watts at 15 Hz to approximately 1500 watts at 50 Hz.

Input and output currents to the generator when with and without the heating coil in the circuit were also measured in four trials. The average efficiency was calculated as the mean of the efficiency of each trial, calculated as: the power output as measured by the observed temperature rise of the water bath, divided by the power used in heating the water (the difference in power with and without the heating coil in the circuit). The average efficiency derived from this calculation was 94%.

Claims

1. A winding for an electrical machine, the winding including turns of current carrying conducting material, the winding having within it at least one fold, a fold having substantially rectilinear side portions joined by a middle portion.

2. A winding as claimed in claim 1 wherein the folds are spaced substantially in a circumference of a disc.

3. A winding as claimed in claim 1 wherein the winding forms substantially a rectilinear shape.

4. A winding as claimed in claim 3 wherein the folds are spaced substantially in the circumference of a cylinder.

5. A winding as claimed in any one of claims 1 to 4 wherein the middle portions of adjacent folds are substantially the same length.

6. A winding as claimed in any one of claims 1 to 5, the side portions of a fold angularly extending from the middle portion, the side portions defining an angle.

7. A winding as claimed in any of claims 1 to 6 wherein the side portions of a fold are substantially parallel.

8. A winding as claimed in any of claims 1 to 4, the winding including a plurality of folds, the sides of the folds being substantially parallel, a first fold having spaced side portions joined by a middle portion, and an adjacent second fold having substantially contiguous rectilinear side portions joined by a middle portion of minimal length.

9. A winding as claimed in claim 8, including a plurality of folds, the folds arranged in a pattern wherein a fold with spaced side portions alternates with a fold having contiguous side portions.

10. A rotor for an electrical machine, the rotor having an array of at least two sources of magnetic fields, the magnetic flux of a magnetic field projecting from each side of the rotor, the polarity of the magnetic flux of adjacent magnetic fields at a side of the rotor alternating from a first magnetic field to the next magnetic field within the array.

11. A rotor as claimed in claim 10 wherein a source of magnetic field is a permanent magnet.

12. The rotor as claimed in claim 11 wherein a magnetic field in the array is comprised of a plurality of magnetic fields with aligned poles.

13. An electrical machine for operation as a motor, the machine including at least one stator, at least one moveable rotor, and a shaft, a rotor as claimed in any of claims 10 or 11 , the stator having a winding as claimed in claim 9.

14. An electrical machine for operation as a motor as claimed in claim 13, the machine including at least one stator and at least two rotors as claimed in any of claim 10 to claim 12, the array of magnetic fields on a first side of a first rotor facing a first side of a stator, the array of a first side of a second rotor facing the second side of the stator, the arrays of the sides of the rotors facing the sides of the stator matched to have magnetic fields of opposite polarities.

15. An electrical machine for operation as a generator, the electrical machine including at least one stator, at least one moveable rotor as claimed in any of claim 10 to claim 12, and a shaft, the stator having a winding as claimed in any of claims 1 to 7, a rotor and a stator arranged in close proximity, movement of the rotor inducing pulses of current in the winding of the stator.

16. A winding as claimed in any on of claims 1 to 9 wherein the current carrying conducting material is any of insulated wire of copper metal, silver metal, or aluminium metal.

17. An electrical machine as claimed in any one of claims 13 to 15 wherein the winding and matched array of magnetic fields are in a radial configuration.

18. An electrical machine as claimed in any of claims 13 to 15 wherein the winding and matched array of magnetic fields are in an axial configuration.

19. An electrical machine as claimed in any one of claims 11 to 16, or claim 17 or claim 18 having a plurality of rotors and a plurality of stators, the arrays of magnetic fields on a side of a first rotor being matched with those on a facing side of a second rotor, . a stator being located between two rotors in an alternating stacked arrangement.

20. An electrical machine as claimed in any one of claims 13 to 19 wherein the long axis of each magnetic field on a rotor is approximately equal to the long axis of the side portions of a fold in the winding of a stator as claimed in any one of claims 1 to 9.

21. An electrical machine as claimed in any one of claims 13 to 20 wherein the rotor frame containing magnetic fields is formed from non-conducting resin material.

22. A method for converting electrical energy to mechanical energy, the method including the steps of:

(i) establishing a two-dimensional array of at least two magnetic fields, adjacent magnetic fields being of opposite polarity; . (ii) establishing a further magnetic field not in the array with one of its dipoles facing the array in (i); (iii) establishing a second two-dimensional array of at least two adjacent magnetic fields, adjacent magnetic fields being of opposite polarity; (iv) matching the magnetic fields of the first and second arrays of magnetic fields so that facing magnetic fields of the first and second arrays are of opposite polarities, the second dipole of the further magnetic field established in (ii) facing the array in (iii); (v) positioning the arrays of magnetic fields in proximity to each other so that the magnetic fields interact, a magnetic field in the first array established in step (i) being attracted or repulsed by the magnetic field established in step (ii), causing the arrays of magnetic fields to move in relation to each other; and (vi) capturing the transformed electrical energy in mechanical movement.

23. A method for converting mechanical energy into electrical energy, the method including the steps of:

(vii) establishing at first two-dimensional array of at least two magnetic fields, adjacent magnetic fields on a side of the array having opposite polarity; and (viii) passing the series of magnetic fields in close proximity to a side of a winding as claimed in any of claims 1 to 9; and (ix) capturing the transformed mechanical energy in an electrical circuit.

24. The method of any of claims 21 or 22 wherein a plurality of matched arrays of magnetic fields are established in a three-dimensional stacked arrangement.

25. A winding for an electrical machine substantially as herein described with reference to the figures.

26. A rotor for an electrical machine substantially as herein described with reference to the figures.

27. A electrical machine for operation as a generator substantially as herein described with reference to the figures.

28. An electrical machine for operation as a motor substantially as herein described with reference to the figures.