Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
  • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
  • H02K7/11—Structural association with clutches, brakes, gears, pulleys or mechanical starters with dynamo-electric clutches
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K16/00—Machines with more than one rotor or stator
  • H02K16/02—Machines with one stator and two or more rotors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
  • H02K7/06—Means for converting reciprocating motion into rotary motion or vice versa
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
  • H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
  • H02K7/1869—Linear generators; sectional generators
  • H02K7/1876—Linear generators; sectional generators with reciprocating, linearly oscillating or vibrating parts
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K49/00—Dynamo-electric clutches; Dynamo-electric brakes
  • H02K49/10—Dynamo-electric clutches; Dynamo-electric brakes of the permanent-magnet type
  • H02K49/102—Magnetic gearings, i.e. assembly of gears, linear or rotary, by which motion is magnetically transferred without physical contact
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/70—Wind energy
  • Y02E10/72—Wind turbines with rotation axis in wind direction

Definitions

• This invention relates to an electrical machine, and in particular to a machine that can be used to generate electrical current efficiently from a slow moving body.
• a recent patent application (EP-A- 2335344) describes machines which have an integrated magnetic gearing system which converts the slow rotation of a prime mover into faster rotation of a rotor in a generator. Double-sided arrays of magnets are employed to produce a very torque dense magnetic gearing system which results in a smaller machine. However, in some cases a high torque density is not necessary.
• the present invention uses one array of magnets co-operating with an array of salient ferromagnetic poles to produce a gearing effect. In some applications, this could be less expensive and more robust than the previous double-sided magnet system.
• an electrical machine comprising:
• a first rotor rotatable about, or movable along, a first axis, and having a first arrangement of ferromagnetic salient poles on a first surface thereof;
• a second rotor held with a first surface thereof adjacent the first surface of the first rotor and such that it is rotatable about a second axis, and having a second
• Figure 1 is a schematic diagram, illustrating a part of a machine in accordance with the present invention.
• Figure 2 shows a part of the machine of Figure 1 , to a larger scale.
• Figure 3 is a cross-sectional view through the part shown in Figure 2.
• Figure 4 shows a first arrangement of ferromagnetic salient poles and magnets on the surfaces of the first and second rotors in the machine of Figure 1.
• Figure 5 shows a second alternative arrangement of ferromagnetic salient poles and magnets on the surfaces of the first and second rotors in the machine of Figure 1.
• Figure 6 shows a third alternative arrangement of ferromagnetic salient poles and magnets on the surfaces of the first and second rotors in the machine of Figure 1.
• Figure 7 shows another aspect of the arrangement of ferromagnetic salient poles on the surfaces of the first or second rotors in the machine of Figure 1.
• Figure 8 shows another aspect of the arrangement of magnets on the surfaces of the first or second rotors in the machine of Figure 1.
• Figure 9 shows an alternative concave section cylinder form of the second rotor.
• Figure 10 shows a second alternative arrangement of the first and second rotors.
• Figure 1 1 shows an alternative convex section cylinder barrel form of the second rotor.
• Figure 12 shows a third alternative arrangement of the first and second rotors.
• Figure 13 shows a fourth alternative arrangement of the first and second rotors.
• Figure 14 illustrates a further machine in accordance with the invention, having a wheeled support for the second rotors.
• Figure 15 shows a first arrangement of a linear generator in accordance with the present invention.
• Figure 16 shows a second arrangement of a linear generator.
• Figure 17 shows a cross section of a linear generator.
• Figure 18 shows a cross section of an alternative linear generator.
• FIG. 1 shows the general structure of an electrical machine 8 in accordance with the present invention.
• the electrical machine is described herein in the form of a generator, in which a rotation of a body is used to generate electrical power.
• the machine 8 of Figure 1 has a first rotor 10, which is connected to an axle 12 by a support structure in the form of spokes 14. Rotation of the axle 12 then causes the rotor 10 to rotate about the axis defined by the axle.
• the rotation of the axle 12 can be driven by a power source such as a wind turbine, a tidal current machine, or a wave energy converter, and although it can of course be driven by any power source, the machine of the present invention is particularly suitable for situations where the driving rotation is at a relatively low speed, for example at about 20rpm for the case of a typical 1.5MW wind turbine.
• a power source such as a wind turbine, a tidal current machine, or a wave energy converter
• the machine of the present invention is particularly suitable for situations where the driving rotation is at a relatively low speed, for example at about 20rpm for the case of a typical 1.5MW wind turbine.
• Figure 1 shows the rotor 10 being driven through the axle 12, it can be driven directly by a body that is being caused to rotate by the external power source. For example, it may be mounted directly onto the hub of a wind turbine.
• the rotor 10 is generally toroidal.
• annular shape which can be generated by rotating a circle about an axis that lies in the plane of the circle but outside the circle. This axis is then the axis about which the rotor is caused to rotate.
• the surface of the rotor is not a complete torus. Specifically, the part of the circular cross-section that lies furthest away from the axis of rotation is omitted, leaving an annular gap 16.
• a cylindrical second rotor 18 Visible through the gap 16 in Figure 1 is a cylindrical second rotor 18, which has an outer circular cross-section that is slightly smaller than the inner circular cross-section of the rotor 10.
• Figure 1 shows only one cylindrical second rotor 18, many such second rotors are in fact located within the first rotor.
• Figure 2 shows in more detail the part of the machine 8 in the region of the second rotor 18.
• the second rotor 18 (and each of the other second rotors, not shown in Figure 1 or 2) is mounted on a support structure 20, which makes it unable to move in the direction of rotation of the first rotor 10, but allows it to rotate about an axis 22 of its own circular cross-section.
• stator 24 Located within the second rotor 18 is a stator 24.
• the second rotor 18 and the stator 24 can be designed such that rotation of the second rotor 18 about its axis 22 causes an electrical current to be generated in the stator 24, which can be supplied through output electrical circuitry (not shown) to electrical power supply lines, electrical power storage devices, etc.
• Figure 3 is a cross-sectional view through the first rotor 10, second rotor 18, and stator 24.
• the first rotor 10 is rotatable about an axis that lies in the plane of this cross-section.
• the second rotor 18 is prevented from rotating about the axis of rotation of the first rotor, but is able to rotate about the axis 22.
• a first, inner, surface 26 of the first rotor 10 and on a first, outer, surface 28 of the second rotor 18 are arrangements of ferromagnetic salient poles and magnets that have the effect that, as the first rotor 10 is caused to rotate about its axis of rotation, the second rotor 18 is forced to rotate about the axis 22. This will be described in more detail below.
• a second, inner, surface 30 of the second rotor 18 and on a first, outer, surface 32 of the stator 24 are the arrangements that are required such that rotation of the second rotor 18 about its axis 22 causes an electrical current to be generated in coils of wire mounted on the stator 24. Suitable forms of these arrangements will be well known to the person skilled in the art, and will not be described further herein.
• Figure 4 shows a first possible arrangement of ferromagnetic salient poles and magnets on the surfaces 26, 28 of the first and second rotors. It will be apparent that the arrangements are shown here schematically as if the two surfaces are planar, rather than circular.
• the illustrated section of the surface 26 has ferromagnetic salient poles 36, 40 as shown. Between the poles are non ferromagnetic slots 34, 38, 42.
• the illustrated section of the surface 28 has a first magnet 44, made from permanent magnet material magnetized in the second direction, then a piece of iron 46, then a second magnet 48, made from permanent magnet material magnetized in the first direction, then a second piece of iron 50, then a third magnet 52, made from
• the arrangement of ferromagnetic salient poles and magnets on the surfaces 26, 28 has a pitch p equal to the width of two of the magnets plus two of the pieces of iron, as shown in Figure 4.
• Figure 5 shows a second possible arrangement of ferromagnetic salient poles and magnets on the surfaces 26, 28 of the first and second rotors. Again, it will be apparent that the arrangements are shown here schematically as if the two surfaces are planar, rather than circular.
• the illustrated section of the surface 26 has ferromagnetic salient poles as shown at 54 and 58. Between the poles are non ferromagnetic slots 56 and 60.
• the illustrated section of the surface 28 has a first magnet 64, made from permanent magnet material magnetized in the second direction, then a second magnet 66, made from permanent magnet material magnetized in the first direction, then a third magnet 68, made from permanent magnet material magnetized in the second direction, then a fourth magnet 70, made from permanent magnet material magnetized in the first direction, and so on.
• a piece of ferromagnetic material, for example iron, 72 is connected to one end of each of these magnets 64, 66, 68, 70.
• the arrangement of ferromagnetic salient poles and magnets on the surfaces 26, 28 has a pitch p equal to the width of two of the magnets as shown in Figure 5.
• Figure 6 shows a third possible arrangement of ferromagnetic salient poles and magnets on the surfaces 26, 28 of the first and second rotors. Again, it will be noted that the arrangements are shown here schematically as if the two surfaces are planar, rather than circular.
• the illustrated section of the surface 26 has ferromagnetic salient poles as shown at 82 and 84. Between the poles are non ferromagnetic slots 83 and 85.
• the illustrated section of surface 28 has permanent magnet material 92 magnetized in such a way as to produce a succession of magnetic North and South poles at the surface 28 as shown and very little magnetic field on the surface 93, forming a structure known to a person skilled in the art as a Halbach array.
• the arrangement of ferromagnetic salient poles and magnets on the surfaces 26, 28 has a pitch p equal to the distance between two successive North poles, or between two successive South poles, as shown in Figure 6.
• ferromagnetic salient poles and magnets are as shown in Figure 4, or as shown in Figure 5, or as shown in Figure 6, they produce a degree of coupling between the first rotor 10 and the second rotor 18.
• magnétique field at surfaces 26 or 28 it is also possible to produce the magnetic field at surfaces 26 or 28 by using conventional electrical machine windings instead of magnets.
• the coupling with the ferromagnetic salient poles may be enhanced by using a conventional electrical machine winding round each ferromagnetic salient pole.
• Figures 7 and 8 show in more detail the arrangements of the ferromagnetic salient poles and magnets on the surfaces 26 or 28.
• the ferromagnetic salient poles and magnets are arranged in helical patterns. These helical patterns have the effect that rotation of the first rotor 10 about its axis of rotation causes rotation of the second rotor 18 about its axis of rotation.
• both the first and second rotors are cylinders
• identical helices on both surfaces 26 and 28 would be advantageous. It is impossible to provide identical helices on surfaces 26 and 28 for the case where one of the rotors is a torus, but this is not necessary.
• the second rotor rotates a full 360 degrees.
• a gear ratio of around 150: 1 that is, the second rotor rotates 150 times for each rotation of the first rotor
• the gear ratio can be altered by changing the diameter of the first rotor and/or of the second rotor, by changing the pitch p of the magnets, or by using more starts on the helical thread patterns.
• Figure 9 shows an alternative form of the first and second rotors.
• the first rotor 10 is in the form of a torus, from which the part of the circular cross section that lies furthest from the axis of rotation is omitted, leaving an annular gap 16.
• the second rotor 18a is not in the form of a right circular cylinder, but rather is a cylindrical object formed by rotating a curved line about the axis 22.
• Figure 10 shows a further alternative form of the first and second rotors, in which the first rotor 110 forms an incomplete torus in which the part of the circular cross section that lies nearest to the axis of rotation is omitted, leaving an annular gap 116, with the second rotor 118 being visible through this gap.
• the second rotor might advantageously be formed by rotating a curved line about the axis 22 so as to form a barrel shaped body with a convex surface as illustrated in more detail in Figure 11 , as in this case that shape conforms more closely to the surface of the inside of the first rotor 10.
• Figure 12 shows a further alternative arrangement, in which the first rotor 120 is formed in the shape of an incomplete torus having two parts 122, 124, by omitting the part of the circular cross section that lies nearest to the axis of rotation of the first rotor and also the part of the circular cross section that lies furthest from the axis of rotation.
• the second rotor 126 is held between these two parts 122, 124.
• Figure 13 shows a further alternative arrangement, in which the first rotor 130 is formed in the shape of an incomplete torus having two parts 132, 134, by retaining only the part 132 of the circular cross section that lies nearest to the axis of rotation and the part 134 of the circular cross section that lies furthest from the axis of rotation, while omitting two annular side pieces.
• the second rotor 136 is held between these two parts 132, 134.
• Figure 14 shows a machine of this type.
• the first and second rotors 1 10, 118 are of the type shown in Figure 11 , in which the first rotor 110 forms an incomplete torus in which the part of the circular cross section that lies nearest to the axis of rotation is omitted, and the second rotor 118 is barrel-shaped.
• the second rotor 118 is mounted on a support structure 120, which allows it to rotate about an axis 122.
• the required clearance between the first and second rotors 1 10, 118 is maintained by a structure in which rails 124, 126 are provided on the outer surface of the first rotor 1 10.
• the rails 124, 126 each have a rectangular profile.
• a mechanism 127 comprising a first rod 128, which is at 90° to the axle 122, and is connected to a second rod 130 at an angle of about 90°.
• Connected to this second rod 130 are three wheels 132, 134, 136.
• the first wheel 132 is located so that it can run along a surface 138 of the rail 126 that is perpendicular to the outer surface of the first rotor 1 10.
• the second wheel 134 is located so that it can run along a surface 140 of the rail 126 that is parallel to the outer surface of the first rotor 110.
• the third wheel 136 is located so that it can run along a surface (not visible in Figure 14) of the rail 126 that is perpendicular to the outer surface of the first rotor 110 and opposite the surface 138.
• a similar mechanism 142 is connected between the axle 122 above the second rotor 118 and the rail 124. Further similar mechanisms 144, 146 are connected between the axle 122 below the rotor 118 and the rails 126, 124 respectively. If the first rotor shown in Figure 1 above is replaced by a straight tube, which is driven by a prime mover which supplies reciprocating linear motion, then this movement can be converted into rotation, and hence used to generate electrical power.
• a machine, suitable for use as a generator in this situation, is shown in Figure 15.
• a first tube 184 is connected to a primary source of energy, such that it is driven along its axis in a reciprocating linear motion, as shown by the arrows A.
• a primary source of energy such that it is driven along its axis in a reciprocating linear motion, as shown by the arrows A.
• the tube 184 is mounted around a second smaller cylinder 180.
• a second smaller cylinder 180 Provided on the outer surface 192 of the tube 180 is a helical arrangement of ferromagnetic salient poles 194 and non ferromagnetic slots 196.
• the reciprocating linear motion of the tube 184 is converted into reciprocating rotation in the smaller cylinder 180 as shown by the arrows B.
• the helical arrangements of the ferromagnetic salient poles and magnets on the respective surfaces can be as shown in Figures 7 and 8. Identical helices on both surfaces would be advantageous. While there is described here an embodiment in which the ferromagnetic salient poles are on the surface 192, while the magnets are on the surface 186, the opposite arrangement would also be possible, with the ferromagnetic salient poles on the surface 186 and the magnets on the surface 192. However, because the magnets are a more expensive component than the
• one of the rotor and the linear component when in use as a wave energy converter, one of the rotor and the linear component will probably have a length at least equal to the stroke of the device, which might be in the region of 2-4m.
• the rotor component 180 will probably have a length of 2-4m, while the linear component 184 might have a length of less than 1 m, and thus perhaps extends along 25-50% of the length of the rotor.
• there might also be an advantage in the surface carrying the magnets being longer than the surface carrying the salient poles.
• a rotor (not shown, but well understood by the person skilled in the art) can then be mounted inside or on the cylinder 180 so as to cooperate with a stationary stator to generate electrical power.
• Figure 16 shows an alternative arrangement, which is identical to that shown in Figure 15, except that the cylinder 180 is driven along its axis in a reciprocating linear motion by a primary source of energy, as shown by the arrows C, and this movement is converted into reciprocating rotation in the tube 184, as shown by the arrows D.
• a rotor (not shown in Figure 16) can be mounted on the tube 184 so as to cooperate with a stationary stator to generate electrical power.
• the type of generator shown in Figure 16 in use as a wave energy converter, again, one of the rotor and the linear component will probably have a length at least equal to the stroke of the device, which might be in the region of 2-4m.
• the 180 will probably have a length of 2-4m, while the rotor 184 might have a length of less than 1 m, and thus perhaps extends along 25-50% of the length of the linear component.
• the rotor 184 might have a length of less than 1 m, and thus perhaps extends along 25-50% of the length of the linear component.
• the surface carrying the magnets being longer than the surface carrying the salient poles.
• Figure 17 is a cross section through the machine of Figure 16, also showing the arrangement for generating electrical power.
• a rotor part 198 of a generator is mounted on the outside of the tube 184, and this is located within the stator part 200 of the generator.
• Figures 15 and 16 are intended for use in situations where the primary energy source is a reciprocating motion, and will usually produce a reciprocating motion on the output side. If continuous rotation in one direction of the rotor 198 is required, however, this is also possible.
• Figure 18 shows a modification of the arrangement shown in Figure 17, which is arranged to produce a more continuous output power.
• a first tube 184 is mounted around a second smaller cylinder 180.
• a second smaller cylinder 180 Provided on the inner surface 186 of the tube 184, and on the outer surface 192 of the tube 180, are helical arrangements of ferromagnetic salient poles and magnets (not shown in Figure 18).
• the tube 184 While the tube 184 is rotating in the first direction, it can drive the rotor 202 through the sprag clutch 204, which allows drive in the first direction and allows the rotor 202 to overrun in the second direction. While the tube 184 is rotating in the second direction, it can drive the rotor 302 through the sprag clutch 304, which allows drive in the second direction and allows the rotor 302 to overrun in the first direction. In this way, the rotors 202 and 302 can act as flywheels to store energy while the cylinder 180 is stationary, so being able to deliver more constant electrical power. Also, the stators 201 , 301 can be arranged so that the electrical output is in a convenient form.
• reciprocating energy source consists of a power stroke in a first direction and a weaker return stroke in a second direction opposite to the first direction. This situation could occur for instance where a buoy floating in the sea pulls a chain attached to the tube 180 providing the power stroke and a spring provides the return stroke.
• stator 301 , rotor 302 and sprag clutch 304 could be omitted.
• the sprag clutch 204 then drives the rotor 202 round on the power stroke and allows the rotor 202 to overrun on the return stroke.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Permanent Magnet Type Synchronous Machine (AREA)
• Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2011
  • 2011-12-16 GB GB1121714.8A patent/GB2497591A/en not_active Withdrawn
• 2012
  • 2012-12-14 CN CN201280066649.2A patent/CN104054255A/zh active Pending
  • 2012-12-14 WO PCT/GB2012/053143 patent/WO2013088166A2/en active Application Filing
  • 2012-12-14 IN IN1440MUN2014 patent/IN2014MN01440A/en unknown
  • 2012-12-14 KR KR1020147019725A patent/KR20140103169A/ko not_active Application Discontinuation
  • 2012-12-14 EP EP12806642.0A patent/EP2792058A2/de not_active Withdrawn

Patent Citations (1)

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