HK1128833B - Generator and magnetic flux conducting unit - Google Patents

Abstract

The invention relates to a generator, to a magnetic flux conducting unit for a generator, and to a power generation machine comprising such a generator. In an embodiment of the invention, a generator (412) is disclosed which comprises at least one coil assembly (428) and at least one magnetic flux conducting unit (410). The magnetic flux conducting unit (410) comprises at least one magnet (314, 316), a pair of opposed magnetic flux conducting elements (318, 320) defining a space (326) therebetween for receiving the coil assembly (428), and at least one connecting portion (322) extending between the opposed magnetic flux conducting elements (318, 320). The at least one magnet (314, 316) is arranged relative to the opposed magnetic flux conducting elements (318, 320) such that magnetic attraction forces between the elements (318, 320) are reacted through and balanced within the connecting portion (322).

Description

Generator and magnetic flux conducting unit

Technical Field

The present invention relates to a generator, a magnetic flux conducting unit for a generator, and a power generating apparatus comprising such a generator. The invention relates particularly, but not exclusively, to a direct drive generator and a magnetic flux conducting unit for a direct drive generator.

Background

In the field of power generation, it is well known to provide generators coupled to fluid driven turbines, such as those distributed in oil, gas, coal fired power plants and nuclear power plants. A conventional generator comprises a core-type stator having a core with a plurality of current carrying coils wound around the core, and a rotor having a core with windings. A magnetic field is generated by passing a current along the rotor coils such that as the rotor rotates, a current is induced in the coils of the stator windings. The rotor of a generator distributed in a power station is coupled to the turbine by a drive shaft which rotates at a high rotational speed of about several thousand rpm and with a relatively low drive torque. Conventional electrical power generators made in view of the above factors have therefore been designed for high speed, low torque operation.

In recent years, considerable research has been conducted worldwide into sustainable methods of power generation, including wind power generation, wave power generation, and tidal power generation.

Existing wind turbines include a prime mover in the form of a large diameter rotor. The rotor has a number of rotor blades mounted on a rotor shaft that is coupled to an electrical generator. The turbine rotor typically rotates at a relatively low rotational speed and high output torque, for example, 20rpm for a 2MW plant, with an output torque of approximately 955 kNm. It will therefore be appreciated that this type of turbine operates at a relatively low rotational speed, but with a relatively high output torque. In order to successfully generate electricity with such low speed, high torque devices, a conventional electrical generator (designed for high speed, low torque operation) requires connection to the turbine rotor through a gearbox. The gearbox increases the speed and reduces the torque for the output from the turbine rotor, which in turn is input to the generator.

The use of this type of gearbox is generally undesirable because of several significant disadvantages. In particular, the gearbox is relatively large and heavy, which adds significantly to the weight of the unit arranged in the nacelle at the top of the wind turbine tower. Furthermore, the provision of a gearbox between the output shaft of the turbine rotor and the input shaft of the generator reduces the efficiency of the apparatus. Moreover, these gearboxes have been found to be very unreliable under typical wind turbine operating conditions. The main reason for this problem is that the operating speed and torque transmitted through the gearbox constantly changes due to fluctuations in wind speed.

Similar problems have been found in power generation systems that use wave and tidal forces, where the prime movers of these systems operate at lower rotational or cyclic speeds and therefore at higher torques or thrusts.

To address these problems, different types of electrical power generators have been developed that are designed for low speed, high torque operation for direct connection to, for example, the rotor of a wind turbine.

Examples of these types of generators include conventional permanent magnet generators and high force density devices such as the Transverse Flux generator (TFM) and the Vernier Hybrid generator (VHM) of NewageAVK SEG, which are proposed for use in direct drive systems. A particular application of these generators has been identified in wave power plants. A linear VHM machine comprises opposed flux conducting cores of generally C-shaped cross-section with a number of successive pairs of oppositely polarised magnets arranged on the core limbs on either side of an air gap between the two opposed cores. A mover having upper and lower castellated surfaces is disposed in the air gap and is coupled to a prime mover of the power generation equipment. In use, the translator reciprocates back and forth within the air gap and the flow of magnetic flux between the two cores commutates as the castellations of the translator are successively aligned with oppositely polarised pairs of magnets, the frequency of the commutation being dependent on the speed at which the translator reciprocates. The coil is arranged on the core arm, thus generating electrical energy when the magnetic field is switched.

Devices of this type with iron cores on the stationary and moving members have considerable drawbacks, in particular because of the very high magnetic attraction between the two cores. To maintain the air gap, this requires a very large and heavy support structure for the core, necessarily affecting the size and weight of the generator. Furthermore, due to these large magnetic attraction forces, the manufacture and assembly of the generator is very difficult.

In order to solve these problems, for example, in connection with the aforementioned iron core type devices, low force density generators have been proposed, which are disclosed in international patent application No. PCT/GB 02/02288. The generator disclosed in PCT/GB02/02288 is designed for a wind turbine and is therefore a rotary generator. In the disclosed generator, iron on the generator stator has been removed and the coils on the stator are supported by a non-magnetic material. In such devices, the magnetic flux coming out of the moving iron surface of the iron core on the rotor of the device has no iron surface into which it can flow, so that the magnetic flux encounters practically an infinite magnetic air gap. The flux density is relatively low and the efficiency and effectiveness of such devices is greatly reduced when compared to other generators. Therefore, much more magnetic material is required on the rotor to achieve any goal like proper operating efficiency, etc. As a result, the physical diameter of the device is required to be greatly increased. For example, for a 5MW hollow core type device, it is estimated that the diameter of the device will be 26 meters, approximately two to three times the diameter of an equivalent core type generator.

In an alternative type of rotary generator, two iron discs are placed in an opposed manner with an air gap between them, and the air core winding is sandwiched between the two moving discs. The magnets are arranged on an iron disc with successive pairs of magnets in opposite polarization (in the circumferential direction). As the disc rotates, the stationary winding successively undergoes commutated flux flows, thereby generating electricity.

However, this type of device has a very large magnetic attraction between the two discs, with the problem that a large and heavy support structure of the type described above is required. This presents a particularly difficult problem in the manufacture of these larger devices, as it is very difficult to maintain the required small air gap (to maximise flux density) whilst keeping the iron discs apart.

Disclosure of Invention

It is therefore an object of embodiments of the present invention to obviate or mitigate at least one of the aforementioned disadvantages.

According to a first aspect of the present invention there is provided a generator comprising at least one coil assembly and at least one magnetic flux conducting unit, the at least one magnetic flux conducting unit comprising:

at least one magnet;

a pair of opposed magnetic flux conducting elements defining a space therebetween for receiving a coil assembly; and

at least one connecting portion extending between the opposed flux conducting elements;

wherein the at least one magnet is arranged relative to the opposed magnetic flux conducting elements such that magnetic attraction between the elements is reacted through and balanced within the connecting portion.

According to a second aspect of the present invention there is provided a magnetic flux conducting unit for a generator, the magnetic flux conducting unit comprising:

at least one magnet;

a pair of opposed magnetic flux conducting elements defining a space therebetween for receiving a coil assembly; and

at least one connecting portion extending between the opposed flux conducting elements;

wherein the at least one magnet is arranged relative to the opposed magnetic flux conducting elements such that magnetic attraction between the elements is reacted through and balanced within the connecting portion.

By reacting the magnetic attractive forces existing between the magnetic flux conducting elements through the connecting portion and balancing the forces within the connecting portion, it is not necessary to provide a large and heavy support structure in order to maintain the air gap between the magnetic flux conducting elements. It will be appreciated that reference herein to magnetic attraction between the magnetic flux conducting elements being reacted through the connecting portions and balanced therein refers to the following: the mechanical load on the magnetic flux conducting units caused by these attractive forces is transmitted from the magnetic flux conducting element to the connection portion, and the magnetic flux conducting units are arranged such that the mechanical forces in the magnetic flux conducting elements interact with each other to be balanced or cancelled. This considerably reduces the weight of the generator when compared to known generators; the generator is easy to manufacture; the manufacturing time is reduced; and thus reduce costs.

It will be appreciated that the connection portion extending between the opposed flux conducting elements thereby defines the maximum extent of the space or air gap between the elements.

In a preferred embodiment, the generator is a direct drive generator and is adapted to be directly coupled to a prime mover of a power plant. The generator may thus be adapted to be coupled to a drive member (e.g. an output shaft or a rotor) of: a wind power plant, a tidal power plant, or a wave power plant, or a free piston Stirling (Stirling) engine in, for example, an integrated thermal power plant. It is to be understood that a direct drive generator refers to a generator that is directly driven from or through a drive member of the power plant.

Alternatively, the generator may be an indirect or indirect generator for indirect or indirect drive applications; some wind turbine applications include a single stage gearbox to increase the speed from say 10rpm to 100 rpm. The generator can therefore be used in those situations which are still considered low speed applications. Further, the generator may be used at any speed in both motoring and generating applications.

Preferably, the at least one magnet is arranged relative to the opposed magnetic flux conducting unit such that a magnetic flux flow path within the magnetic flux conducting unit extends through the connecting portion. The connection portion may thus be flux conducting and may be positioned within, or may define part of, the flux flow path of the unit.

The magnetic flux conducting unit may be generally C-shaped in cross-section, the connecting portion forming a base or central member, and the elements being coupled in a cantilevered arrangement relative to the base. A space or air gap is defined between the two opposing elements, in which the coil assembly is seated. Alternatively, the magnetic flux conducting unit may be generally I-shaped in cross-section, the connecting portion forming a base or central member and the elements being coupled to the central member so as to form two cantilever portions on either side of the central member, two spaces or air gaps being located between the magnetic flux conducting elements on either side of the connecting portion. There may be two coil assemblies, one disposed in each air gap. In each of the above cases, the at least one magnet may be arranged such that magnetic attraction between the magnetic flux conducting elements generates mechanical loads within the elements which are transmitted to the connecting portions and react with each other. The mechanical load is maintained within the cell. Wherein the element is cantilevered with respect to the connection portion or comprises a cantilevered portion whereby a torque can be generated with respect to the connection portion. However, the at least one magnet may be arranged such that the torque of each element is equal and opposite and centered about the neutral axis of the connection portion to balance the load.

In yet another alternative embodiment, the cross-section of the flux conducting unit may be generally rectangular or square, the two connecting portions extending between the opposed flux conducting elements, and a space or air gap being defined between the two connecting portions, and the coil assembly being positioned within the air gap. Mechanical loads in the element may be transmitted to both connection portions and the at least one magnet may be arranged such that torques around the central axis of the connection portions are balanced as described above.

In an embodiment of the invention, the magnets are arranged within the space or air gap defined between the elements. The unit may comprise a magnet connected to each element, the magnets being arranged with opposite poles facing each other, and the coil assembly being disposed between opposing magnet surfaces. The unit may comprise a C-core, a connecting portion forming a base or side of the C-core, and magnetic flux conducting elements forming opposing arms of the C-core. The unit may comprise two such C cores as described above arranged back to back, which may share the same connecting portion. It will therefore be appreciated that such a unit may be generally I-shaped and may therefore form an I-core. The generator may thus comprise two coil assemblies and two pairs of magnets, the coil assemblies being disposed on both sides of the connection portion and the two pairs of magnets being coupled to elements on both sides of the connection portion.

In an alternative embodiment of the invention, the at least one magnet may define or form a connecting portion of the magnetic flux conducting unit. The at least one magnet may thus be used to define an air gap between the magnetic flux conducting elements. The unit may be generally C-shaped, the magnet forming a base or central member and the flux conducting elements forming opposed arms. The unit may comprise two of the above-described components arranged back-to-back, which therefore share the same magnet, and it will be appreciated that such a unit may be generally I-shaped. The generator may comprise two coil assemblies, one disposed in each space or air gap defined on either side of the magnet.

In yet another alternative embodiment of the invention, the unit may comprise two magnets extending between the magnetic flux conducting elements, each magnet defining a connecting portion, and a space or air gap being defined between the magnets to seat the coil assembly. Alternatively, the unit may comprise a unitary body defining the magnetic flux conducting element, and thus the magnetic flux conducting unit may form one continuous portion, with the rectangular portion optionally being removed from its centre. The magnets may be positioned on opposing surfaces and the windings may be sandwiched between the two magnets in the remaining space. The cross-section of the cell may be substantially rectangular or square.

Preferably, the generator comprises a plurality of flux conducting units, and the direction of flux flow within each unit and through the respective at least one space or air gap may be opposite to the direction of flux flow in the or each adjacent flux conducting unit. In the above manner, the relative movement of the magnetic flux conducting units continuously switches the direction of the magnetic flux flowing through the coil assembly, thereby generating an electric current within the coil assembly.

The generator may be a rotary generator and may comprise a rotor and a stator, the rotor being adapted to be coupled to a drive member of a prime mover of the power generation apparatus and thus adapted for rotation relative to the stator. The at least one coil assembly may be disposed on one of the rotor and the stator, and the at least one magnetic flux conducting unit may be disposed on the other of the rotor and the stator. Wherein the generator comprises a plurality of units which may be arranged circumferentially around the rotor or the stator and may be arranged such that the main axis or plane of the flux conducting elements of the units is parallel to the axis of the shaft of the rotor or perpendicular to the rotor axis.

Alternatively, the generator may be a linear generator and may comprise a mover and a stator, the mover being adapted to be coupled to a drive member of a prime mover of the power generation apparatus. The coil assembly may be disposed on one of the mover and the stator, and the at least one magnetic flux conducting unit is disposed on the other of the mover and the stator. The generator may comprise a plurality of magnetic flux conducting units, said units extending along a plane parallel to the plane of the mover. The generator may include a plurality of movers and corresponding stators, each mover being coupled to a drive member of a common prime mover.

In the case of a generator comprising a plurality of cells, adjacent cells may be separated by an air gap or by a spacer block that is non-magnetically permeable/magnetically insulating, or whose magnetic permeability is negligible compared to the magnetic flux conducting cells. Alternatively, adjacent cells may abut against each other so that they are not separated by air gaps/spacers.

The at least one magnet may be a permanent magnet that may be magnetized after being placed within the cell. This may facilitate assembly of the unit by ensuring that the magnet is placed in the desired position before magnetization and hence before any magnetic attraction is generated. To facilitate manufacture of the unit, a clip or fixture may be provided for placing the at least one magnet in the unit prior to magnetization. Optionally, the at least one magnet may be magnetized prior to placement into the cell.

The at least one coil assembly may include a plurality of current conducting coils and may be constructed of copper or other suitable material. The magnetic flux conducting element may be made of iron, an iron alloy such as steel or similar material. The at least one connection portion may similarly be composed of iron or an iron alloy.

According to a third aspect of the present invention there is provided a generator comprising at least one coil assembly and at least one magnetic flux conducting unit, the at least one magnetic flux conducting unit comprising:

a pair of opposed magnetic flux conducting elements defining a space therebetween for receiving a coil assembly; and

at least one magnet extending between the opposed magnetic flux conducting elements, the at least one magnet being arranged relative to the opposed magnetic flux conducting elements such that magnetic attraction between the elements is reacted by the at least one magnet and balanced within the at least one magnet.

According to a fourth aspect of the present invention there is provided a magnetic flux conducting unit for a generator, the magnetic flux conducting unit comprising:

a pair of opposed magnetic flux conducting elements defining a space therebetween for housing a coil assembly of the generator; and

at least one magnet extending between the opposed magnetic flux conducting elements, the at least one magnet being arranged relative to the opposed magnetic flux conducting elements such that magnetic attraction between the elements is reacted by and balanced within the at least one magnet.

According to a fifth aspect of the present invention there is provided a power generation plant comprising a generator of the first or third aspects of the present invention.

Drawings

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

FIG. 1 is a schematic view of a magnetic flux conducting unit for a generator according to an embodiment of the invention;

FIG. 2 is a schematic side view of a portion of a generator including the magnetic flux conducting unit of FIG. 1, according to an embodiment of the invention;

FIG. 2A is a schematic side view of a power plant incorporating the generator shown in FIG. 2;

FIG. 3 is a schematic side view of a portion of a generator including the magnetic flux conducting unit of FIG. 1, according to an alternative embodiment of the present invention;

FIG. 4 is a schematic front view of a portion of a generator including the magnetic flux conducting unit of FIG. 1, according to another alternative embodiment of the present invention;

FIG. 5 is an end view of the generator of FIG. 4;

FIG. 6 is a schematic view of a magnetic flux conducting unit for a generator according to another embodiment of the invention;

FIG. 7 is a view of the unit shown in FIG. 6 showing a bearing assembly by which the coil assembly is mounted to the unit;

FIG. 8 is a perspective view of a generator according to a preferred embodiment of the present invention incorporating a magnetic flux conducting unit similar to that shown in FIGS. 6 and 7;

FIG. 9 is a view of a portion of the generator shown in FIG. 8;

FIGS. 10 and 11 are views of a magnetic flux conducting unit and a coil assembly, respectively, forming part of the generator shown in FIG. 9;

FIG. 12 is a schematic end view of a generator according to yet another embodiment of the present invention;

FIG. 13 is an end view of a portion of a generator including a magnetic flux conducting unit according to yet another alternative embodiment of the invention;

FIG. 14 is a perspective view of the magnetic flux conducting unit shown in FIG. 13;

FIG. 15 is a perspective partial cut-away view of a generator including a magnetic flux conducting unit according to yet another alternative embodiment of the invention;

FIG. 16 is a longitudinal cross-sectional view of the generator shown in FIG. 15;

FIG. 17 is a view of the magnetic flux conducting unit of FIG. 15, taken along the line of FIG. 15;

FIG. 18 is a view of a power plant incorporating the generator of FIG. 15; and

fig. 19 is a schematic diagram of a power plant incorporating the generator of fig. 13.

Detailed Description

Referring initially to fig. 1, a schematic diagram of a magnetic flux conducting unit for a generator, generally indicated by reference numeral 10, is shown, in accordance with an embodiment of the present invention. A portion of a generator 12 comprising the magnetic flux conducting unit 10 shown in fig. 1 is shown in the schematic side view of fig. 2. As shown in fig. 1 and 2, the magnetic flux conducting unit 10 includes: a pair of magnets 14, 16; a pair of opposed magnetic flux conducting elements in the form of arms 18 and 20; and a connecting portion 22 extending between arms 18 and 20. The magnets 14 and 16 are arranged such that the magnetic flux flow path 24 (indicated by the broken outline) extends in a counterclockwise direction when viewing fig. 1. It is to be understood that, in order to achieve the above object, the directions of the magnetic poles of the magnets 14 and 16 may be set to S-N/S-N when viewing fig. 1 from above to below. The arms 18 and 20 and the connecting portion 22 together form a generally C-shaped core and are constructed of a magnetic flux conducting material, such as iron, or an iron alloy, e.g., steel.

A space or air gap 26 is defined between the opposed arms 18, 20 and the magnets 14 and 16 are placed within the air gap, with the magnet 14 magnetically coupled to the arm 18 and the magnet 16 magnetically coupled to the arm 20. If desired, the magnets 14 and 16 may be magnetized in situ and held in place by a clamp, jig, or support prior to magnetization. The coil assembly 28 of the generator 12 is placed within the air gap 26 between the opposed magnets 14, 16, as will be appreciated by those skilled in the art, the coil assembly 28 comprising a plurality of coils of an electrically conductive material (e.g., copper).

The generator 12 shown in fig. 2 is of the rotary type and comprises a plurality of units 10, which units 10 are arranged around the circumference of a rotor disc, wheel or the like 30, which rotor disc, wheel or the like 30 is mounted on a rotor shaft 32. The rotor shaft 32 is coupled to a prime mover of the power plant. FIG. 2A shows a power generation facility in the form of a wind turbine 33 having a prime mover in the form of a rotor 35 coupled in a direct drive manner to generator 12 by a shaft 37. The generator 12 is therefore a direct drive generator, driven directly by the output shaft 37 through the rotor 35.

The generator 12 also includes a stator 34 having a stator disc, frame or the like 36 to which the coil assembly 28 is mounted. The stator 34 is mounted on the shaft 32 by means of bearings 39. As shown in fig. 2, the cells 10 are arranged around the periphery of the rotor disc 30, with the respective planes of the cell arms 18 and 20 being arranged perpendicular to the rotor shaft axis 40.

During use of the generator 12, there is magnetic attraction between the pairs of opposed arms 18 and 20 of the respective flux conducting units 10. These magnetic attractive forces attempt to close the air gap 26 and exert a mechanical load on the arms 18, 20. Due to the connection with the portion 22, and the fact that: the magnets 14, 16 are arranged such that the magnetic flux flow path 24 extends from the magnet 16, through the arm 20, through the connecting portion 22, through the arm 18 and to the magnet 14, these mechanical loads being transmitted to the connecting portion 22. In practice, the arms 18 and 20 are suspended relative to the connecting portion 22. The attractive force between the arms 18 and 20 exerts a mechanical load on the arm 18. This produces a torque about the central or neutralizing axis 42 of the C-core in a counterclockwise direction when viewing fig. 1. Conversely, mechanical loads on the arm 20 produce a torque about the neutral axis 42 in a clockwise direction. These torques effectively balance and cancel so that the magnetic attraction between the arms 18 and 20 is reacted through and balanced within the connecting portion 22. With this arrangement, it is not necessary to provide a large, heavy support structure in order to maintain the air gap between the arms 18 and 20, and thus the overall size and weight of the generator 12 is greatly reduced when compared to existing direct drive generators. The above description is achieved while maintaining a high magnetic flux density and a small air gap between the arms 18 and 20, thereby ensuring efficient operation of the generator 12.

The generator 12 operates to generate electricity as follows. As mentioned above, the individual cells 10 are arranged around the periphery 38 of the rotor disc 30. The flux flow paths in the cells adjacent to cell 10 are in opposite directions. The flux flow path in the cell adjacent to the cell 10 shown in fig. 2 therefore flows in a clockwise direction. This is achieved by reversing the polarity of the magnets 14, 16 on the cells adjacent to cell 10.

Thus, in use and as the rotor disc 30 is driven by the wind turbine rotor shaft 37, the coil assembly 28 is subjected to a flow of successively changing magnetic flux, thereby generating an electrical current within the coils of the coil assembly. It will be appreciated that the unit 10 may be disposed on the stator 34 and the coil assembly 28 disposed on the rotor 29, if desired.

Referring now to fig. 3, there is shown a schematic side view of a portion of a generator, generally indicated by reference numeral 112, incorporating the unit 10 shown in fig. 1, in accordance with an alternative embodiment of the present invention. Components of the generator 112 that are identical to the generator 12 of fig. 2 have been given the same reference numerals, increased by 100.

The generator 112 comprises two rotor discs 130a and 130b, each with a set of flux conducting units 10 adjacent respective edges 138a, 138b spaced around the circumference of the respective disc 130a, 130 b. The respective arms 18, 20 of the unit 10 on each rotor 130a, 130b are arranged such that the plane of the arms is parallel to the rotor shaft axis 140. The stator 134 of the generator 112 carries two sets of coil assemblies 128a, 128b for each unit 10 on the rotors 130a, 130 b. The generator 112 thus allows both rotors 130a, 130b to be driven by a common rotor shaft 132, providing improved efficiency without significant increase in size.

Turning now to fig. 4 and 5, there are shown schematic side and end views of a portion of a generator according to yet another alternative embodiment of the present invention, the generator being generally designated by reference numeral 212, incorporating the magnetic flux conducting unit 10 of fig. 1. Components of the generator 212 that are identical to the generator 12 of fig. 2 are given the same reference numerals, plus 200.

The generator 212 is of the linear type and is suitable for use in a linear power plant, such as a free piston stirling engine in a wave power plant or a domestic CHP unit (not shown). In the illustrated embodiment, a plurality of magnetic flux conducting units 10c, 10d, 10e and 10f are shown and mounted on a mover (translator)44, the translator 44 being directly coupled to the prime mover of the apparatus. The coil assembly 228 is disposed in the air gaps 26c to 26f of the respective units 10. As shown in the drawing, the magnetic flux flow directions in the adjacent cells 10c to 10f are opposite directions, and in the respective flow paths 24c to 24f, the arrow tails indicate inflow into the paper and the arrow heads indicate outflow from the paper. Thus, during the movement of the units 10c to 10f back and forth in the direction of the arrow X-X', the coil assembly 228 experiences a continuously varying flux flow, thereby generating a current in the coil. As shown in fig. 5, the bearing assembly 46 is disposed between the supports 48 and the coil assembly 228 is mounted on the supports 48 to facilitate relative movement between the unit 10 and the coil assembly 228.

Turning now to fig. 6, there is shown a schematic view of a magnetic flux conducting unit for a generator, generally indicated by reference numeral 310, according to an alternative embodiment of the invention. Components of unit 310 that are similar to unit 10 of figure 1 have been given the same reference numerals, plus 300.

As shown, the unit 310 comprises a pair of opposed magnetic flux conducting elements in the form of arms 318, 320, the arms 318, 320 being coupled together by two magnets 314, 316, each of which defines a connecting portion of the unit 310. A space or air gap 326 is defined between the surfaces 50 and 52 of each arm 318, 320, the air gap 326 housing a coil assembly 328 of the generator. The cells 310 are generally rectangular in cross-section, with the coil assembly 328 centrally positioned in the structure. As shown in fig. 7, bearing assembly 346 mounts coil assembly 328 within air gap 326 and facilitates relative movement between unit 310 and coil assembly 328.

The magnets 314, 316 are arranged relative to the arms 318, 320 to create two flux flow paths 324a and 324b in two circuits that extend from the magnet 314/316 into the arm 318, through the air gap 326 into the arm 320 and back to the respective magnet 314/316. These flux flow paths 324a, 324b extend in clockwise and counterclockwise directions, respectively, when viewing fig. 6.

By virtue of this arrangement of the magnets 314, 316, the magnetic attraction between the arms 318, 320 is balanced on both sides of the unit 310, within the magnets 314 and 316, about respective neutral axes 342a and 342 b. Thus, in a manner similar to the unit 10 of FIG. 1, the magnetic attraction between the arms 318 and 320 is reacted through and balanced within the connecting portions (magnets 314 and 316). This avoids the need to provide a large and heavy support structure. Furthermore, due to the provision of the two magnets 314, 316, a greater magnetic flux density is provided in the air gap 326 than would occur in the air gap 26 of the unit 10 shown in fig. 1, thereby providing improved efficiency of the generator comprising the unit 310.

A magnetic flux conducting generator incorporating a similar design to that of unit 310 is shown in perspective view in fig. 8 and is generally designated by reference numeral 412. Components of the generator 412 that are identical to the generator 12 of fig. 2 have been given the same reference numerals, plus 400. The generator 412 includes three arrays 54, 54', and 54 "of magnetic flux conducting units and corresponding coil assemblies. One of the arrays 54 is shown in fig. 9, separated from the rest of the generator 412 for ease of reference. It should be appreciated that the generator 412 is of a linear type, similar to that described above with reference to fig. 4.

The array 54 includes a plurality of flux conducting units 310g to 310j and the flux flow paths in adjacent units flow in opposite directions as in the generator 212 of fig. 4. The units 310g to 310j are each separated by a non-magnetically conductive spacer 56 and are coupled to a reciprocating prime mover or a mover of a reciprocating mechanical load (not shown), such as a mover that may be installed in a wave power plant. The coil assembly 428 includes a plurality of coil sections (coil sections) 58, and the units 310g to 310j and the coil assembly 428 are independently shown in fig. 10 and 11, respectively.

Each coil assembly 428, 428 ', and 428 "(fig. 8) is mounted to the stationary frame 60, and each coil assembly 428, 428', and 428" is a three-phase winding comprising three layers of coil segments or windings 58. The uppermost coil assembly 428 is shown in fig. 9-11 and includes three layers of windings 58a, 58b and 58c, each layer representing a phase. It should be understood that the components 428' and 428 "are of similar construction. The cells 310 of each array 54, 54', 54 "are mounted on the moveable base 62 one on top of the other. In use, the cells 310 of the arrays 54, 54 'and 54 "reciprocate back and forth in the direction of arrows Y-Y', as shown in FIG. 8. This reciprocating motion and the flux flow variations in adjacent cells 310 of each array 54 ensure that each coil segment 58 of the respective coil assembly 428 experiences a continuously varying flux flow direction, thereby generating an electrical current.

By configuring the arrays 54, 54', and 54 "for the generator 412 in the manner described above, a common drive source may be used while optimizing the size and weight of the generator 412 and providing improved efficiency.

Turning now to fig. 12, there is shown a schematic end view of a portion of a generator, indicated generally by the reference numeral 512, in accordance with yet another alternative embodiment of the present invention.

The generator 512 is a linear generator similar to the generator 212 of fig. 4 and the generator 412 of fig. 8. However, the generator 512 includes a plurality of magnetic flux conducting units 510, components of the units 510 that are of the same kind as the units 10 of figure 1, and components of the generator 512 that are of the same kind as the generator 12 of figure 2, are given the same reference numerals, plus 500.

The unit 510 essentially comprises two units 10 of fig. 1 arranged back-to-back with a single magnet 514 extending between the flux conducting arms 518, 520 of the unit 510. Two flux flow paths 524a and 524b are created within the unit 510, extending from the magnet 514 into the arm 518, across the air gaps 526a/526b, into the arm 520 and back to the magnet 514. The magnets of adjacent cells are of opposite polarity so that the flow paths of adjacent cells extend in opposite directions.

The units 510 are each coupled to a mover of a power plant, such as a wave power plant (not shown), and reciprocate in the same manner as the generators 212, 412. The coil assemblies 528a, 528b are disposed in the air gaps 526a, 526b and are mounted to the stationary frame 560 by bearing assemblies 546a, 546 b. The generator 512 operates in a similar manner as the generator 412 to generate electricity.

Turning now to fig. 13, there is shown an end view of a generator incorporating magnetic flux conducting units, the generator being generally indicated by reference numeral 612 and the magnetic flux conducting units being indicated by reference numeral 610, in accordance with yet another alternative embodiment of the present invention. Components of the generator 612 that are identical to the generator 12 of fig. 2, and components of the unit 610 that are identical to the unit 10 of fig. 1, are given the same reference numerals, increased by 600. However, only the substantial differences will be described in detail herein.

The generator 612 is substantially similar in construction to the generator 412 of fig. 8, and is therefore a linear generator comprising a plurality of arrays of flux conducting units and coil assemblies, one of which is shown and designated by reference numeral 654. The array 654 includes a plurality of adjacently disposed magnetic flux conducting units 610, one of which is shown. The units 610 each include a pair of spaced opposed arms 618, 620 carrying respective magnets 614 and 616. The arms 618, 620 are generally C-shaped in cross-section and include edges or ends 64 and 66, respectively, which collectively define a connecting portion 622. The array 654 includes a coil assembly 628 that is placed within an air gap 626 defined between the magnets 614 and 616 and which includes a plurality of separate windings or coil segments 658a, 658b, and 658 c. Bearing 68 is mounted between shoulders 70 and 72 of arms 618 and 620 and may be a low friction material such as PTFE, hydrostatic bearings, magnetic bearings, or more conventional roller bearings. In this example a plain bearing is shown. As best shown in fig. 14, which is a perspective view of unit 610, bearing 68 includes a groove 74. The coil assembly 628 includes a mount 76, the mount 76 being sized to engage within the bearing groove 74, which allows sliding movement of the unit 610 relative to the coil assembly 628. Thus, in a manner similar to the generator 412 of FIG. 8, the cells 610 of the array 654 reciprocate back and forth relative to the coil assemblies 628, generating alternating current.

In use, two flux flow paths 624a and 624b are created within the unit 610, and the attractive force between the arms 618 and 620 is balanced within the connecting portion 622 by the abutment between the edges 64 and 66. However, it should be understood that bearing 68 also resists the attractive forces between arms 618 and 620 and therefore can be considered to be part of connecting portion 622. Further, it will be appreciated that the attractive force between edges 64 and 66 holds arms 618 and 620 together.

The cells 610 are arranged within the generator 612 in a manner similar to the cells 310 shown in fig. 8, except that the spacer blocks are omitted so that each cell 610 is disposed adjacent to an adjacent cell or cells. This is because the inventors have found that flux flow along the axial direction of the array of cells 610 is advantageous and improves the efficiency of the generator 612 in use. With the arrangement of the units 610 shown in fig. 13, the magnetic flux flow can also start from the arm 620 of one unit 610 in the direction Y' in fig. 14 (indicated by the arrowed tail into the paper in fig. 13) along with the magnetic flux flow direction indicated by the arrows in the flow paths 624a and 624 b; into an arm 620 on an adjacent cell 610 (not shown); magnets 616 and 614 passing up through adjacent cells; arm 618 into an adjacent cell; and then back to the arm 618 of the unit 610 shown in fig. 13 (indicated by the arrow coming out of the sheet).

Turning now to fig. 15, there is shown a perspective partial cut-away view of a generator incorporating a magnetic flux conducting unit according to yet another alternative embodiment of the present invention. The generator is generally designated by reference numeral 712 and is a rotary generator comprising a plurality of circumferentially arranged cells 710. Components of the unit 710 that are identical to the unit 10 of fig. 1, and components of the generator 712 that are identical to the generator 12 of fig. 2, are given the same reference numerals, plus 700. The generator 712 is generally similar in structure to the generator 112 shown in fig. 3, except that the generator 712 includes only a single circumferential array of magnetic flux conducting units 710 and coil assemblies 728.

The generator 712 is shown in more detail in the longitudinal cross-sectional view of fig. 16 and in fig. 17, fig. 16 being drawn on a smaller scale, and fig. 17 being a view of the magnetic flux conducting unit 710 cut as shown in fig. 15 and also drawn on a smaller scale.

The generator 712 includes a rotor 729 having a rotor shaft 732 with rotor disks 730. The circumferentially distributed flux conducting units 710 are each mounted to the rotor disc 730 around its circumferential edge and are of similar construction to the unit 10 shown in figure 3, except that the arms 718 and 720 are longer. Like the cells 620 of the generator 612 of fig. 13, the cells 710 are adjacent to each other and therefore do not provide spacer blocks, thereby improving efficiency. A coil assembly 728 containing a plurality of coil segments 758 is mounted on the stator plate 736 such that the coil segments 758 extend into the respective air gaps 726 of the unit 710. The coil segments 758 are mounted in the air gap 726 using suitable bearings 746. The generator 712 is provided as part of a wind turbine 733 shown in FIG. 18.

In use, the stator 734 carrying the coil assembly 728 is mounted in the nacelle 78 of a wind turbine 733, while the rotor shaft 732 is coupled to a prime mover in the form of a turbine blade assembly 80. In this manner, rotation of blade set 80 transmits drive to rotor shaft 732 and thus rotor disk 730. This causes the magnetic flux conducting unit 710 to rotate, generating an alternating current as described above.

Turning finally to fig. 19, there is shown a schematic view of a power generation apparatus in the form of a wave device 633 comprising the generator 612 of fig. 13. The generator 612 is schematically shown in the figure. The wave device 633 includes a buoy 82, which is shown floating on the sea surface 84, however, the inherent buoyancy of the buoy 82 may cause the buoy to be submerged below the sea surface 84, relative to the weight of the remaining components of the device 633.

The buoy 82 is connected to an array of flux conducting elements by a coupling assembly 86, however, only a single such element 654 is shown. The stator 634 of the wave apparatus 633 is positioned on the sea floor 88 and the coil assembly is mounted on the base 90 of the stator 634.

In use, under the action of an applied wave load, the float 82 rises and falls and raises and lowers the array 654 and, thus, the magnetic flux conducting unit 610 moves relative to the coil assembly 628, thereby generating an alternating current. The end stops 92 and 94 define the maximum allowable range of motion of the array 654 relative to the coil assembly 628.

Various modifications may be made to the foregoing without departing from the spirit and scope of the invention.

For example, it will be appreciated that the generator of the present invention may be used or provided in a wide range of different types of equipment, arranged as a rotary or linear generator as required or desired, and in particular in wave power plants, wind power plants, tidal power plants, ocean current power plants.

Claims (13)

1. A rotary electrical generator comprising at least one air-core coil assembly having a plurality of current conducting coils and a plurality of magnetic flux conducting units, each of the plurality of magnetic flux conducting units comprising:

at least one magnet;

a pair of opposed iron or iron alloy flux conducting elements defining a space therebetween for receiving the at least one air core coil assembly; and

at least one connecting portion extending between the opposed magnetic flux conducting elements;

wherein the at least one magnet is arranged relative to the opposed magnetic flux conducting elements such that magnetic attraction between the magnetic flux conducting elements is reacted through the connecting portion and balanced within the connecting portion,

the generator is a rotary generator comprising a rotor and a stator, one of the rotor and the stator carrying the plurality of magnetic flux conducting units and the other of the rotor and the stator carrying the at least one hollow coil assembly, the rotor being adapted to be coupled to a drive member of a prime mover of a power generating apparatus and thereby adapted to rotate relative to the stator,

and wherein the plurality of flux conducting units are arranged around the circumference of the disc of the rotor or stator.

2. A generator as claimed in claim 1, wherein the generator is a direct drive generator adapted to be coupled directly to a prime mover of a power generation plant or an indirect drive generator adapted to be coupled to a prime mover of a power generation plant through a gearbox.

3. A generator as claimed in claim 1 or 2, wherein the at least one magnet of the magnetic flux conducting unit is arranged relative to the opposed magnetic flux conducting element such that a magnetic flux flow path within the magnetic flux conducting unit extends through the connection portion.

4. A generator as claimed in claim 1 or 2, wherein the magnetic flux conducting unit is generally C-shaped in cross-section, the connecting portion forms a central member of the magnetic flux conducting unit, and the magnetic flux conducting element is coupled in a cantilevered arrangement relative to the central member.

5. A generator as claimed in claim 1 or 2, wherein the magnetic flux conducting unit is generally I-shaped in cross-section, the connecting portion forms a central member of the magnetic flux conducting unit, and the magnetic flux conducting element is coupled to the central member so as to form a cantilevered portion on either side of the central member, and a space is located between the magnetic flux conducting elements on either side of the connecting portion, a hollow coil assembly being located in each space.

6. A generator as claimed in claim 1 or 2, wherein the magnetic flux conducting unit is generally rectangular in cross-section with two connecting portions extending between the opposed magnetic flux conducting elements, and wherein the space is defined between the magnetic flux conducting elements and the two connecting portions.

7. A generator as claimed in claim 1 or 2, wherein the at least one magnet is arranged within the space defined between the magnetic flux conducting elements.

8. A generator as claimed in claim 1 or 2, wherein the at least one magnet of the magnetic flux conducting unit defines the connection portion of the magnetic flux conducting unit.

9. A generator as claimed in claim 1 or 2, comprising two magnets extending between the magnetic flux conducting elements, each magnet defining a connecting portion, and a space between the magnets for receiving an air-cored coil assembly.

10. A generator as claimed in claim 1 or 2, wherein the magnetic flux conducting unit comprises a unitary body defining the magnetic flux conducting elements and the connecting portion, and an opening through the unitary body defines the space between the magnetic flux conducting elements.

11. A generator as claimed in claim 10, wherein the magnetic flux conducting unit comprises two magnets disposed on opposite faces of the magnetic flux conducting elements, the air-core coil assembly formed from windings being disposed between the two magnets in the space between the magnetic flux conducting elements.

12. A generator as claimed in claim 1 or 2, comprising a plurality of magnetic flux conducting units, and wherein the direction of magnetic flux flow within each unit and through the corresponding at least one space in each unit is opposite to the direction of magnetic flux flow in the or each adjacent unit.

13. A rotary electric motor comprising at least one air-cored coil assembly having a plurality of current conducting coils and a plurality of magnetic flux conducting units, each of the plurality of magnetic flux conducting units comprising:

at least one magnet;

a pair of opposed iron or iron alloy flux conducting elements defining a space therebetween for receiving the at least one air core coil assembly; and

at least one connecting portion extending between the opposed magnetic flux conducting elements;

wherein the at least one magnet is arranged relative to the opposed magnetic flux conducting elements such that magnetic attraction between the magnetic flux conducting elements is reacted through the connecting portion and balanced within the connecting portion,

the rotary electric motor includes a rotor and a stator, wherein one of the rotor and the stator houses the plurality of magnetic flux conducting units and the other of the rotor and the stator houses the at least one hollow coil assembly, the rotor being adapted to rotate relative to the stator,

and wherein the plurality of flux conducting units are arranged around the circumference of the disc of the rotor or stator.