FIELD OF DISCLOSURE

This disclosure relates to electric power machines (e.g., generators and motors) and specifically to a rotor or rotors that are used in electric power machines. It relates more specifically to a material composition of the rotor which may augment or enhance a magnetic field in the electric power machine.

BACKGROUND OF DISCLOSURE

In prior art electric power generators, and electric power machines in general, a magnetic field is produced by electromagnets and/or permanent magnets. The electromagnets are made by using current carrying conductors wound around a steel core to generate a controllable magnetic field and the permanent magnets are made to have fixed magnetic poles with fixed unchangeable magnetic field. Both these types of magnetic field source magnets are well known in the industry and widely used in the industry for use in generator applications and motors.

These magnetic field source magnets may have weaknesses such as needing a steel core and conductors and electric current to generate magnetic field to function properly. The steel core is usually an electric steel material which is expensive and heavy. This electric steel must be machined with special machinery and this raises its costs. The conductors are mostly made of material comprising copper metal as a conductor of the current to generate the magnetic field. Copper itself is an expensive metal and has a very high density, and it is therefore heavy as well. The fact that the electric steel and the copper make up the electromagnet causes it to be heavy which may stress on bearings and a steel structure that carry them, especially during rotation as a result of the centrifugal forces.

The current in the conductors generates heat in the electromagnets which then need cooling. The electromagnets can be in the rotor and in some cases in a return path of the magnetic field. In both cases, current is supplied to the electromagnets and cooling may be important. In case of the rotor comprising the electromagnets, as the rotor spins, the current to the field coils may be supplied via a brush and slip ring system. The field coils are subject to large centrifugal forces due to the rotation of the rotor. In order to secure the field coils, they are often coated in a resin and lodged into coil slots on the rotor body and sometimes wedges are used to secure them in place. In summary, using the electromagnets, especially in the rotor, as the primary sources of magnetic flux in the machine may have limitations, namely the need for a brush and slip ring system and the need to secure the field coils in order to withstand the centrifugal forces.

Magnetite is ferrous and thus has ferromagnetic properties. The Applicant’s own prior PCT Application No. IB/2017/056569 discloses use of magnetite in an electromagnet in an electric power generator. This electromagnet is made with a steel core and magnetite together with conductors through which current flows and generate magnetic field to be used in the power generator. This electromagnet as described still has the characteristic of electromagnets in that it uses the electric steel which has got a disadvantage that it is heavy and expensive, etc. and has copper windings.

US5628900 discloses magnetite for use in water purification. This particular application is far removed from power generation application which has its own challenges like cooling and rotation of the rotor and losses too.

The present disclosure aims to solve or reduce the abovementioned weaknesses of electromagnets and permanent magnets and still generate enough magnetic field for electric power generation. SUMMARY OF DISCLOSURE

Accordingly, the disclosure provides an electric power machine which includes: a first rotor member including a magnetic field source configured to produce a magnetic field with at least one pair of magnetic poles; and

a stator provided around, or radially outward of, the first rotor member, the stator including a plurality of windings, characterised in that the electric power machine includes:

a second rotor member provided around, or radially outward of, the stator, the second rotor member comprising a magnetite material, the second rotor member being arranged to have induced therein a magnetic polarity by the magnetic field generated by the first rotor member, the polarised second rotor member then serving to direct or enhance the magnetic field generated by the first rotor member.

The electric power machine may be an electric power generator or an electric power motor.

In the case of a generator, the windings may be configured to generate a current induced by the magnetic field.

The magnetite material may comprise at least magnetite (e.g., magnetite powder) and a binder. The binder may be a resin. The magnetite material may be sintered magnetite granules or powder.

The second rotor member may comprise a plurality of magnetite elements. Each magnetite element may be in the form of an arcuate section. Each magnetite element may be radially aligned with one of the poles operatively generated by the first rotor member.

The stator may be a first stator member and there may be plural stator members including at least a second stator member. The second stator member may be provided inside the first rotor member. In such case, a structure of the electric power generator may be (moving from a central axis radially outwardly): the second stator member; the first rotor member; the first stator member; and the second rotor member.

The second stator member maybe hollow, e.g., being cylindrical.

The electric generator may be radially scalable meaning that more rotor and/or stator members may be added. This may have the advantage of a higher power density at a cost of complexity.

The first and second rotor members may be relatively fixed, meaning that they maintain their relative circumferential orientation during rotation.

Differently stated, the disclosure may disclose a concept whereby secondary magnetic fields are generated by linking a primary magnetic field (i.e. , the magnetic field generated by the first rotor member) with the materials that are magnetisable and polarisable and then produce their own magnetic fields, e.g., when an iron material or fine grounded magnetite block or steel is brought close to a magnetic field either an electromagnet or a permanent magnet, this sintered magnetite material assumes an opposite polarity to that of the facing magnet that is when a North pole of Magnet faces a sintered fine ground magnetite mixed with resin block/suitable shape the block gets a polarity of South pole and also gets a magnetic field strength up to 100% of the magnet field facing it depending on distance between the two. By doing this the magnetite block adds magnetic field to the magnetic circuit and increases the magnetic field in the circuit by about 27% (based on measurements one a prototype built by the Inventor). This magnetite material by itself generates very little to no magnetic field, but when a magnet field is close enough such that the magnetic field of the electromagnet or permanent magnet links with the block, it may generate about up to 100% of the closer magnet magnetic field strength. This idea may be used in an electric power generator, and there must be a primary source of Magnetic field, either an electromagnet, a permanent magnet or windings with current flowing in them close enough for its field to link with the iron material or magnetite block and with large enough magnetic field.

The present disclosure proposes the concept of augmenting magnetic field from secondary sources of magnetic field by linking the magnetic field from a primary magnetic field source to a secondary magnetic field source, the primary magnetic field source are electromagnets and permanent magnets even the magnetic field from the stator/armature may serve as the primary source of the magnetic field to excite the secondary source of the magnetic field as long as it happens such that the magnetic field from the primary source links with the material comprising magnetite material, the stator winding has induced therein an electric current. This embodiment may be suitable for stationary/rotating parts such as the return path, a stationary secondary magnetic field source and the central shaft and rotors as well because there is no current fed into these windings and therefore no need for slip ring arrangement.

The stator may have windings in the teeth to enhance the primary magnetic field. This embodiment may be in the form of two rotors sandwiching a stationary secondary source of magnetic field. The primary magnetic field source is original magnetic field that links with the magnetite material and excite the magnetic material like magnetite to generate its own magnetic field. The magnetite for use in this application may be ground very fine and to lose its permanent magnet properties of fixed magnetic field strength and its fixed magnetic poles. When a magnetic material like ground magnetite mixed with resin or a sintered magnetite is brought close to a primary source of magnetic field which is an electromagnet or a Permanent magnet, the magnetite material assumes an opposite polarity, that is when the primary source of the magnetic field is north pole (N) the magnetite material becomes a south pole (S), and also may assume about +100% of the primary magnetic fields strength when the magnetic linking is from one surface, when the magnetic linking is from both the surfaces such that the magnetite material is sandwiched between to primary sources of magnetic field that have attracting polarities, north-south pole relationship, the magnetic field of the secondary sources of the magnetic field is raised higher by about +25% depending on the airgap between the primary source of the magnetic field and secondary source of the magnetic field, the magnetic field strength of the primary source of the magnetic also may increase by +10% compared to when it is alone, so the secondary source of magnetic field, once activated with the magnetic field from the primary magnetic add to the overall magnetic field of the magnetic circuit such the magnetic field of the secondary source may increase and approach the strength of the primary magnetic strength.

To reduce the effect of distance between the primary source of magnetic field and secondary source of magnetic field, a relatively small permanent magnet may be embedded in the sintered magnetite mixed with resin. In such case, the sintered magnetite mixed with resin may act as a primary source of magnetic field and will also enhance the magnetic field of the magnetite material.

Magnetite as a material is very soft and therefore when the sintered magnetite mixed with material is used on the surface of a secondary or primary source of magnetic field, the airgap between this sintered magnetite and any other surface may be less than 1 mm. Because of the distance that will be created by presence of the stator between the primary source and the secondary source of magnetic field, the magnetic flux strength may be 1 .5 Tesla or more in the airgap. The optimum distance between the stator and the secondary source of the magnetic field may be twice the thickness of the secondary source of the magnetic field.

For this disclosure to operate better, when there is primary source of magnetic field, the adjacent source of magnetic field may be a secondary source of magnetic field. Every primary source of magnetic field may be bordered by a secondary source of magnetic field on both surfaces of the primary source of the magnetic field in a rotor structure. The magnetite rotor may rotate while the primary source of the magnetic field may be stationery where the airgap between the two layers will be very small to almost non-existence and the surfaces are touching to enhance the secondary magnetic field source generation. The embodiment of this disclosure may be arranged such that there are two rotors one with primary sources of magnetic field and the other rotor with magnetite as the secondary source of magnetic field. The other embodiment of this disclosure is where the primary source of magnetic field is on the return path and the secondary source of the magnetic field is the rotor. Therefore, the rotor is the magnetite material, in this case the rotor made of magnetite will be very light and reduce the rotational mass of the rotating member.

The main advantage of the magnetite compared to copper and electric steel is cost. Magnetite sells for about ZAR1 ,000/ton and copper sells for about USD6, 000/ton (~ZAR85,000), electric steel sells for about USD3500/ton and based on cost alone the magnetite rotor is much more affordable. In addition to cost, the fine magnetite mixed with resin is more than two times lighter than the electromagnet and therefore embodiments with rotors made of this magnetite may operationally be cost effective.

The electromagnets made of electric steel, copper windings and electric current maybe located in strategic position where they are not rotating, easy to cool, easy to access for maintenance and easy to monitor. There are other embodiments of the disclosure where there are one or two primary sources of magnetic field and one secondary source of magnetic field is more suitable for use in a multi-layer electric power generator. In the multi-layer generator, the embodiments of the disclosure may be such that there is N+1 secondary source of magnetic field and N primary source of magnetic field, where N stands for number of primary sources of magnetic field. Another embodiment is where there is N+1 primary source of magnetic field and N+1 secondary source of magnetic field, where N stands for number of rotors. Another embodiment is where there is one primary source of magnetic field sandwiched between two secondary sources of magnetic field, where the embodiment can have N primary sources of magnetic and N+1 sources of secondary magnetic field, all the above permutations are possible if and only if the N number of primary sources of magnetic field is one or more. Because of the presence of the secondary source of the magnetic field, the stator may have windings on both the two surfaces facing the sources of the magnetic field.

A four pole machine may generate more magnetic field in the secondary magnetic field sources than a two pole machine, an eight pole machine will do better compared to a six pole or four pole machine. For this reason, one of the embodiments of this disclosure is to have a better pole coverage or have as many poles as possible on the primary source of the magnetic field. The other embodiment of this disclosure is whereby the central shaft has one active polarity electromagnet and the rotor is made of sintered magnetite mixed with resin all around and electronic switching is used to change polarities in order to generate a sinusoidal waveform. The other embodiment is that the same central shaft as explained above has another polarity which may link with the return path to activate the sintered magnetite on the return path. The return path may be made entirely of the sintered magnetite. The stator where windings are located may be made wholly of sintered magnetite mixed with resin. The magnetite material may also be put on the inside /outside surface of the return path facing the rotating pole of the rotor. In this case the embodiment is such that the when the North pole of primary source magnetic field faces a portion of the magnetite material on the inside surface of the return path, that specific portion of the return path complies and becomes a South pole. On the same return path with magnetite material, when another portion of the magnetite faces a South pole, that specific portion becomes a North pole, doing away with a need to do electronic switching of the poles. In terms of the rotation of the magnetic sources, the primary source may rotate while the secondary source maybe stationary and also the primary source may be stationary and the secondary source may rotate.

When steel is brought closer to the magnet, the magnetic field reading on the surface of the steel is higher compared to when the same activity is done with Magnetite, but surprisingly, the magnetic field reading at an airgap of say 10mm, the magnetic field density for magnetite is better than that of steel. Therefore, the magnetite mixed with resin can be used instead of a steel on the return path. When measuring the magnetic flux on the steel outside the facing surface with magnet, the magnetic flux on the steel is so much higher and when the same activity is done with magnetite the magnetite performs poorly. Magnetite comparatively performs better on radial dispersion of magnetic field and the steel does better on lateral dispersion of magnetic field. Therefore, magnetite may be used instead of steel where radial dispersion of magnetic flux is needed as in return path, magnet shoe.

Magnetite generate a smoother waveform compared to steel with a smaller airgap of magnitude of +0.25mm. For a steel material to get a smoother waveform, a standard procedure during design is to increases the airgap and at the same time this action decrease the performance of the generator, therefore the magnetite gives a better waveform and better performance. It was also evident that during the test work , the thinner the magnetite element the better it performs with radial dispersion of the magnetic field which saves material and weight , The magnetite at the same time gives a suitable thermal property for this application of releasing the heat very slow and gives a better opportunity to effect cooling with a smaller airgap. The combination of these three properties of smoother waveform, the thinner magnetite element and slow release of heat means that at a smaller airgap, the Generator may perform thermally better and the output will also be better. For Generator application the magnetite may replace the steel material for these critical properties.

While the description above has focused on an electric machine in the form of a generator, the teachings of this disclosure may also be applied to an electric machine in the form of a motor. Magnetite as a secondary source of magnetic field can also be utilised for the different parts and operations of an electric motor. Magnetite material when it is finely ground and mixed with resin has some very desirable properties for electric motor operation.

The desirable properties of magnetite for this application are • Very light compared to Steel

• Effect better cooling on its surface

• May improve the electric field intensity

• May self-machine

For electric motor applications, it may be necessary to have a very small airgap of about 1 mm down to about 0.2 mm, with material comprising magnetite mixed with resin as the base material on the surface of the stator and the rotor, where the two surfaces are facing the airgap, the airgap may be made smaller than 0.2 mm and in case of the operation when the material expand the two surface will self -machine for an appropriate operating airgap. The self-machining may also improve the eccentricity of the electric motor. When the airgap is smaller the effect of the magnetic field and the effect of the electric field may be more effective than when the airgap is bigger, so for the electric motor with smaller airgap the application of fine magnetite mixed with resin is more suitable than for an electric generator with an airgap of 100 mm. Magnetite may effect better cooling than electric steel and therefore can help to cool the electric motor.

In an electric motor it may also be needed to generate a soother torque and therefore a stable rotation of the rotor. Magnetite material produces a smoother magnetic wave form, and, in this case, it is a solution by operationally producing a smoother torque and stable electric motor. Fine magnetite has electric charges and when the magnetite material mixed with resin is linking with a magnetic field, the magnetite charges get excited by the magnetic field and this generate an electric field and this electric field when it is on the surface facing the airgap improves the performance of the electric motor. The magnetite mixed with resin is suitable for this application to make the stator and the rotors to achieve the overall better performance of the electric motor. The electric field from the stator and the rotors made with magnetite mixed with resin will interact with each other and improve the performance of the electric motor as the two surfaces are active in generating the torque for the rotor. The technical improvement brought by the fine magnetite mixed with resin and its electric field may bring with it a huge commercial success, the commercial success will come because of the following factors.

• Improved level of electric field from two interacting surfaces

• Very high energy density

• Less weight on the rotor

• The idea of using magnetite to improve the electric field is simple and very effective.

• Less current may be used for the electric motor

• Comparatively very low cost of magnetite

The electric motor may be made with one stator located between two rotors to make a three-layer electric motor; another embodiment is when the electric motor is made with one stator overlaid by a plurality of concentric rotors. Another embodiment is to have an electric motor with a stator located between two rotors and put a stator adjacent to the other rotor to generate electric power, whereby this electric machine can serve as an electric motor and as a generator at the same time.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings:

FIG. 1 shows a cross-sectional view of a first embodiment of an electric power generator, in accordance with the disclosure; FIG. 2 shows a cross-sectional view of a second embodiment of an electric power generator, in accordance with the disclosure;

FIG. 3 shows a three-dimensional cross-sectional view of the electric power generator of FIG. 2;

FIG. 4 shows a three-dimensional view of a magnetite element of the electric power generator of FIG. 2;

FIG. 5 shows a cross-sectional view of the magnetite element of FIG. 4;

FIG. 6 shows a top view of the magnetite element of FIG. 4; and

FIG. 7 shows a cross-sectional view of the electric power generator of FIG. 2 with magnetic poles and field lines.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

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

FIG. 1 illustrates a cross-sectional view of a first embodiment of an electric power generator 90, in accordance with the disclosure. It will be understood that the generator 90 may include many additional components common to generators such as bearings, a support frame, controlling electrics, etc. which are not illustrated but are understood to be included if necessary/desirable. FIGS 2-3 illustrate cross-sectional views of a second embodiment of an electric power generator 100, in accordance with the disclosure. Again, it will be understood that the generator 100 may include many additional components common to generators.

The main difference between the first and second embodiments 90, 100 is that the first embodiment 90 has only one stator member 106 while the second embodiment 100 has two stator members 106, 1 14. Otherwise, the embodiments 90, 100 may be similar or identical. The second embodiment is described in more detail below, but the description (other than features relating to the second stator member 1 14) applies equally to the first embodiment.

The generator 100 has a first rotor member 102 which includes a magnetic field source 104. The magnetic field source 104 may be permanent magnets or magnetic windings configured as an electromagnet. Either way, the magnetic field source 104 is configured to produce a magnetic field with at least one pair of magnetic poles. In this example, the magnetic field source 104 produces two poles which are opposite in polarity and diametrically opposed to each other. This first rotor member 102, in itself, may be fairly conventional.

The generator 100 includes a stator comprising at least one stator member and, in this embodiment, it comprises two stator members 106, 1 14, namely a first (radially outer) stator member 106 and a second (radially inner) stator member 1 14. Most conventional generators have only a single stator member or layer, but multi-layer stators are not new in themselves. The configuration of the stator members 106, 1 14 may be fairly conventional.

For example, the first stator member 106 has a plurality of circumferentially spaced teeth 108 and each pair of adjacent teeth 108 defines therebetween a slot 1 10 for accommodating windings (not illustrated) configured to have a current induced therein by the magnetic field. The second stator member 1 14 may be optional but may be useful to increase a power generating capability of the generator 100.

Importantly, the electric power generator 100 comprises a second rotor member 1 12. This second rotor member 1 12 is provided around, or radially outward of, the first stator member 106. The second rotor member 1 12 comprises a magnetite material, like powdered magnetite mixed with a resin binder and formed into a desired shape. In this embodiment, the second rotor member 1 12 comprises two magnetite elements 1 12.1 , 1 12.2, each formed into an arcuate section.

There are the same number of magnetite elements 1 12.1 , 1 12.2 as there are poles provided by the magnetic field source 104; there are two poles and therefore there are two magnetite elements 1 12.1 , 1 12.2. Each magnetite element 1 12.1 , 1 12.2 is radially aligned with one of the poles operatively generated by the first rotor member 104. The magnetite elements 1 12.1 , 1 12.2 are not inherently magnetised nor do they, in isolation, generate any magnetic field.

One of the magnetite elements 1 12.1 is illustrated in more detail in FIGS 4-6. There may be many practicable shapes that the magnetite element 1 12.1 could be formed into, but in this embodiment, it is arcuate in cross-sectional profile (FIG. 5) and elongate in top view (FIG. 6). It is configured to extend roughly a whole length of the rotors 106, 1 14. It may have a lip or ridge on each side to facilitate mounting within the generator 100.

FIG. 7 illustrates the electric power generator 100 showing simplified example magnetic poles (S-N-S-N) and magnetic field or flux shown in broken lines. FIG. 7 is significant because it illustrates a key feature and advantage of the present embodiment. A 2-pole magnetic field is generated by the magnets 104 of the rotor 102. This magnetic field induces a corresponding but opposite polarity in the magnetite elements 1 12.1 , 1 12.2. The magnetite elements 1 12.1 , 1 12.2 thus serve to enhance and direct the magnetic field through the generator 100 and specifically through the stator member 106, 114 and their current-generating windings. The magnetite elements 112.1 , 112.2 may form part of a back-iron (if present) of the electric power generator 100.

The magnetite elements 112.1 , 112.2 are comparatively light, as magnetite is light (in powder form) and the resin binder is significantly lighter than steel. Accordingly, while the inclusion of the magnetite elements 112.1 , 112.2 does add some mass to the generator 100, it is relatively little, and the benefit of a more focussed and directed magnetic field outweighs the additional weight.

The electric power generator 100 is also scalable in that additional rotor members and stator members may be provided. In one version, two rotor members and one stator member (or simply, the stator) are a minimum, but this may be expanded upon. Also, additional magnetic field sources could be provided in the additional rotor members, if desired.

CLAUSES

1. An electric motor where either the stator body or the rotor body is made fine with magnetite mixed with resin.

2. An electric motor where the stator body and the rotor body are made fine magnetite mixed with resin.

3. A method of operation of an electric motor where the stator body and the rotor body are made with fine magnetite mixed with resin where the magnetite increases the Electric field on the surfaces of the stator and the rotor.

4. A method of operation of an electric motor where the stator and the rotors are made with fine magnetite mixed with resin and the air-gap between the stator and the rotor is less than 0.2mm and the stator surface and the rotor surface will self- machine when the material expand for an appropriate operating air-gap. 5. A method of operation of an electric motor where the stator body and the rotor body are made with fine magnetite mixed with resin where the magnetite generates a smoother torque on the rotor movement and improves the stability of the electric motor.

6. An electric motor according to clause 1 where the stator and rotor windings are pasted with magnetite mixed with material comprising magnetite.

7. An electric motor according to clause 1 with one stator and two rotors where the stator is located between the two rotors and the stator body and the rotors body is made with fine magnetite mixed with resin.

8. An electric motor according to clause 1 with one stator and many concentric rotors surrounding the inner stator.

9. An electric motor according to clause 1 with two stators and two rotors where one stator is located between the two rotors and another stator is located adjacent to the other rotor to generate electric power.