Source: http://www.patentsencyclopedia.com/app/20140028147
Timestamp: 2018-10-20 17:34:02
Document Index: 476082958

Matched Legal Cases: ['§371', '§119', 'Application No. 61', '§371', '§119', 'Application No. 61']

Multi-Pole Electrodynamic Machine with a Constant Air Gap And An Elliptical Swash-Plate Rotor To Reduce Back Torque - Patent application
Patent application title: Multi-Pole Electrodynamic Machine with a Constant Air Gap And An Elliptical Swash-Plate Rotor To Reduce Back Torque
USPC Class: 310216074
Class name: Windings and core structure core pole structure
Patent application number: 20140028147
1. An electrodynamic generator machine comprising: a stator assembly comprising: at least two salient poles arranged to minimize eddy currents, hysteresis loops, or iron losses by protecting from flux movement in at least two directions; at least one field winding that when energized creates a magnetic flux; and at least one power winding that, upon experiencing a change in magnetic flux, generates an induced voltage; a rotor assembly comprising; a shaft; a flux path element mounted on the shaft and configured to direct magnetic flux through a flux zone, and wherein the flux path element is further configured to magnetically couple pairs of the at least two salient poles by providing a low-reluctance path between the pairs, and wherein the rotation of the shaft enables the flux path element to vary the location of the flux zone in a periodic fashion; and the stator assembly and the rotor assembly positioned so as to form a substantially constant air gap there between.
2. The generator machine of claim 1 wherein the number of the at least two salient poles is 2N, where N is an integer greater than or equal to two.
3. The generator machine of claim 1 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated from a different metal.
4. The generator machine of claim 1 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using a predetermined grain orientation.
5. The generator machine of claim 1 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using ferrite materials.
6. The generator machine of claim 1 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using distributed air gap material.
7. The generator machine of claim 1 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using sintered steel material
8. The generator machine of claim 1 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated from laminations disposed at right angles with respect to one another.
9. The generator machine of claim 1 wherein the flux path element is substantially elliptical in shape and is mounted on the shaft at an oblique angle with respect to the longitudinal axis of the shaft.
10. The flux path element of claim 9 wherein the substantially elliptical shape can be described with reference to a circle with a radius r at an angle θ measured from the center of the circle and in the plane of the circle; wherein a radius R, may be drawn at an angle of inclination a from the plane of the circle and at a length given by R=(r2+(r sin α)2)1/2; and wherein the perimeter of the substantially elliptical shape is described by rotating R about the full 360 degrees of angle θ about the reference circle.
11. The generator machine of claim 1 wherein the flux path element comprises a stack of laminated, magnetically conductive disks.
12. The generator machine of claim 1 wherein the flux path element comprises silicone steel lamination.
13. The generator machine of claim 1 wherein the flux path element comprises sintered steel alloys.
14. The generator machine of claim 1 wherein the flux path element comprises a distributed air gap material.
15. The generator machine of claim 1 wherein the induced voltage created in the power windings by a change in magnetic flux further comprises an output frequency related to the angular velocity of the shaft.
16. The generator machine of claim 15, wherein, for a given output frequency, the angular velocity of the shaft is a multiplier of a conventional shaft angular velocity.
17. The generator machine of claim 16, wherein the multiplier of the conventional shaft angular velocity is 1/N, and where N is the number of salient poles in the stator assembly.
18. The generator machine of claim 1 further comprising at least two field windings and wherein each field winding is configured to produce a magnetic flux of substantially the same magnitude, but substantially opposite polarity.
19. The generator machine of claim 1 wherein the rotor assembly is configured to act as a swash plate when it is impinged upon by Lenz forces which are parallel to the axis of rotation.
20. The rotor assembly of claim 19 wherein the action of the swash plate enables a lower average torque requirement to rotate the rotor assembly shaft.
21. The generator machine of claim 1 wherein the magnetic flux created by the at least one field winding mechanically changes its direction under the operation of the rotor assembly.
22. The generator machine of claim 1 wherein the at least one field winding has a conductor size and number of turns at a predetermined amount to establish a magnetic flux of a predetermined value and keep copper losses to a minimum.
23. The generator machine of claim 1 wherein rotational speed of the shaft increases when the impedance of an output electric load approaches a short circuit condition.
24. An electric generator with reduced Back Torque comprising: a stator assembly further comprising: at least four salient poles each having a face, and arranged in pairs located on opposite sides of a longitudinal axis of the stator assembly; each salient pole further comprising a field winding and a power winding, wherein the field windings on opposite salient poles of each pair are wound to create a magnetic flux of equivalent magnitude, but opposite polarity; a rotor assembly further comprising: a shaft; a flux path element located on the shaft and wherein rotation of the shaft causes a flux coupling zone related to the flux path element to oscillate along the face of a salient pole; the stator assembly and rotor assembly being located in a manner that creates a substantially constant air gap between the stator assembly and the rotor assembly.
25. The electric generator of claim 24 wherein an induced voltage created in the power windings by a change in magnetic flux has an output frequency related to the angular velocity of the shaft.
26. The electric generator of claim 25, wherein, for a given output frequency, the angular velocity of the shaft is a multiplier of a conventional shaft angular velocity.
27. The electric generator of claim 26, wherein the multiplier of the angular velocity is 1/N, and where N is the number of salient poles in the stator assembly.
28. The electric generator of claim 25 wherein the power windings of each pair of the at least four salient poles generates a single phase output for a combined two phase output.
29. The electric generator of claim 28 wherein the number of electric output phases of the generator is N/2 phases, and where N is the number of salient poles in the stator assembly.
30. The electric generator of claim 24 where the oscillation of the flux coupling zone along the face a salient pole causes a force that is directed parallel to the axis of rotation of the shaft.
31. The electric generator of claim 30 wherein the force directed parallel to the axis of rotation of the shaft enables a lower average torque requirement to rotate the shaft.
32. The electric generator of claim 24 wherein the at least four salient poles are arranged to minimize eddy currents, hysteresis loops, or iron losses by protecting from flux movement in at least two directions.
33. The generator machine of claim 32 wherein the at least four salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated from a different metal.
34. The generator machine of claim 32 wherein the at least four salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using a predetermined grain orientation.
35. The generator machine of claim 32 wherein the at least four salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using ferrite materials.
36. The generator machine of claim 32 wherein the at least four salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using distributed air gap material.
37. The generator machine of claim 32 wherein the at least four salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using sintered steel material
38. The generator machine of claim 32 wherein the at least four salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated from laminations disposed at right angles with respect to one another.
39. The generator machine of claim 24 wherein rotational speed of the shaft increases when the impedance of an output electric load approaches a short circuit condition.
40. An electrodynamic machine comprising: a stator assembly comprising: at least two salient poles arranged to protect from flux movement in at least two directions; at least one field winding that when energized creates a magnetic flux; and a rotor assembly comprising; a shaft; a flux path element mounted on the shaft and configured to direct magnetic flux through a flux zone, and wherein the flux path element is further configured to magnetically couple pairs of the at least two salient poles by providing a low-reluctance path between the pairs, and wherein the rotation of the shaft enables the flux path element to vary the location of the flux zone in a periodic fashion; and wherein the position of maximum flux concentration alternates from a relative minimum position to a maximum displacement during the periodic varying of location without undergoing a reversal of flux polarity.
41. The electrodynamic machine of claim 40 wherein rotational speed of the shaft increases when the impedance of an output electric load approaches a short circuit condition.
42. The electrodynamic machine of claim 40 wherein the number of the at least two salient poles is 2N, where N is an integer greater than or equal to two.
43. The electrodynamic machine of claim 40 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated from a different metal.
44. The electrodynamic machine of claim 40 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using a predetermined grain orientation.
45. The electrodynamic machine of claim 40 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using ferrite materials.
46. The electrodynamic machine of claim 40 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using distributed air gap material.
47. The electrodynamic machine of claim 40 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated using sintered steel material
48. The electrodynamic machine of claim 40 wherein the at least two salient poles protect from flux movement in at least two directions by comprising poles where at least a portion of the pole is fabricated from laminations disposed at right angles with respect to one another.
49. The electrodynamic machine of claim 40 wherein the flux path element is substantially elliptical in shape and is mounted on the shaft at an oblique angle with respect to the longitudinal axis of the shaft.
50. The flux path element of claim 49 wherein the substantially elliptical shape can be described with reference to a circle with a radius r at an angle θ measured from the center of the circle and in the plane of the circle; wherein a radius R, may be drawn at an angle of inclination a from the plane of the circle and at a length given by R=(r2+(r sin α)2)1/2; and wherein the perimeter of the substantially elliptical shape is described by rotating R about the full 360 degrees of angle θ about the reference circle.
51. The electrodynamic machine of claim 40 wherein the flux path element comprises a stack of laminated, magnetically conductive disks.
52. The electrodynamic machine of claim 40 wherein the flux path element comprises silicone steel lamination.
53. The electrodynamic machine of claim 40 wherein the flux path element comprises sintered steel alloys.
54. The electrodynamic machine of claim 40 wherein the flux path element comprises a distributed air gap material.
55. The electrodynamic machine of claim 40 wherein the induced voltage created in the power windings by a change in magnetic flux further comprises an output frequency related to the angular velocity of the shaft.
56. The electrodynamic machine of claim 55, wherein, for a given output frequency, the angular velocity of the shaft is a multiplier of a conventional shaft angular velocity.
57. The electrodynamic machine of claim 56, wherein the multiplier of the angular velocity is 1/N, and where N is the number of salient poles in the stator assembly.
58. The electrodynamic machine of claim 40 further comprising at least two field windings and wherein each field winding is configured to produce a magnetic flux of substantially the same magnitude, but substantially opposite polarity.
59. The electrodynamic machine of claim 40 wherein the rotor assembly is configured to act as a swash plate when it is impinged upon by Lenz forces which are parallel to the axis of rotation.
60. The rotor assembly of claim 59 wherein the action of the swash plate enables a lower average torque requirement to rotate the rotor assembly shaft.
61. The electrodynamic machine of claim 40 wherein the magnetic flux created by the at least one field winding mechanically changes its direction under the operation of the rotor assembly.
62. The electrodynamic machine of claim 40 wherein the at least one field winding has a conductor size and number of turns at a predetermined amount to establish a magnetic flux of a predetermined value and keep copper losses to a minimum.
[0001] The present application claims priority from U.S. Provisional Patent Application Ser. No. 61/677,412, filed on Jul. 30, 2012 and entitled "Multi-Pole Electric Electrodynamic Machine with a Constant Air Gap To Reduce Back Torque", the disclosure of which is incorporated herein by reference in its entirety.
[0002] This application is also related to the following concurrently-pending applications: application Ser. No. 13/562,214, titled "Controller for Back EMF Reducing Motor;" application Ser. No. 13/562,199, titled "Three Phase Synchronous Reluctance Motor With Constant Air Gap And Recovery Of Inductive Field Energy;" and application Ser. No. 13/562,233, titled "Multi-Pole Switched Reluctance D.C. Motor with a Constant Air Gap and Recovery of Inductive Field Energy;" each of which are hereby incorporated by reference.
[0005] Patents in this area include: U.S. Pat. Nos. 2,917,699; 3,132,269; 3,321,652; 3,956,649; 3,571,639; 3,398,386; 3,760,205; 4, 639,626 and 4,659,953. Also in this area are EPO patent no. 0174290 (3/1986); German patent no. 1538242 (10/1969); French patent no. 2386181 (10/1978) and UK patent no. 1263176 (211972).
[0006] The basic concept employed in earlier electrodynamic machine art, concerning generators, is the interaction between a moving conductor(s) and a magnetic field of some kind However, existing machines typically experience performance limitations due to the manner in which Back EMF (in motors), Back Torque (in alternators and generators), and inductive field energy (in general) are treated. One drawback of Back EMF is its parasitic nature that serves to degrade the potential supplied to the motor from an outside source (i.e., the source voltage). Likewise, Back Torque in electrical generating machines necessitates the application of additional prime-mover motive force (i.e., additional torque) in order to overcome degradation of the source torque and function on a continual basis.
[0008] The above-described basic geometry of a conventional system results in the production of parasitic Back EMF in a motor as follows. In many traditional electric motor systems, the magnetic flux must interact with an electrical current-carrying conductor (e.g., rotor windings), thereby producing a mechanical force that generates a torque to turn the motor shaft (i.e., a motor action). The subsequent motion of the conductors through the magnetic flux produces a relatively high Back EMF (i.e., acts in opposition to the torque producing current) due to the motion of the conductors with respect to the magnetic flux (i.e., a generator action). In order to continue normal operation, and establish electrical equilibrium, any motor that produces a Back EMF having a constant average value, must draw down on the line-potential in order to overcome the effects of this parasitic reverse voltage. Thus, this process of source potential degradation due to Back EMF requires the input of considerable potential energy from the source in the form of a higher voltage in order to maintain normal operation.
[0009] In a conventional generator the production of parasitic Back Torque arises from the same principles. Mechanical torque is required to rotate the electrical conductors of the rotor (e.g., rotor windings) in the presence of a magnetic field (e.g., as produced by the stator field windings). This, in turn, produces an electrical current (e.g., in the rotor windings) that also interacts with the field and produces a relatively high Back Torque (i.e., acts in opposition to the torque driving the rotor). In order to continue normal operation and establish electrical equilibrium, any generator that produces a Back Torque requires a continuous supply of mechanical torque on the rotor from the prime mover in order to overcome the effects of the parasitic Back Torque and generate electricity. Thus, this process of source torque degradation due to Back Torque requires the input of considerable power from the prime mover source in order to maintain normal operation.
[0010] A different approach from the above and other existing devices is disclosed in the related U.S. Pat. No. 4,789,632, titled "Alternator Having Improved Efficiency," to the same inventor of the present application, in U.S. patent application Ser. No. 12/993,941, which in turn is a 35 U.S.C. §371 filing of Application No. PCT/US09/46246, which in turn claims the benefit under 35 U.S.C. §119 to provisional Application No. 61/085,824, in U.S. patent application Ser. No. 13/390,437, which in turn is a 35 U.S.C. §371 filing of Application No. PCT/US10/45298, which in turn claims the benefit under 35 U.S.C. §119 to provisional Application No. 61/234,011, and in the above-noted related applications, each of which is hereby incorporated in its entirety by reference. The approach outlined therein generally involves, among other things, a canted flux path element as part of the rotor assembly and a constant dimension air gap between rotor and stator elements that reduces or realigns the Back EMF or Back Torque in motor and generator machines respectively.
[0011] As discussed above, conventional electrodynamic machines (e.g., motors and generators) are typically interchangeable in function (i.e., from motor to generator, or vice versa), by simply reversing shaft torque (i.e., using the applied field to produce shaft torque, or applying torque to the shaft to produce an output voltage). However, in the constant-dimension air gap, Back EMF and Back Torque reducing motor designs described in the above patents and applications of the present inventor, applying torque to a motor shaft will produce only a small output voltage, due to the unique rotor geometry which enables a constant air gap during operation. Typically, a Back EMF reducing motor of the disclosed designs when driven as a generator will produce a voltage substantially equivalent in magnitude to the Back EMF that would be produced by running the device as a motor. Likewise, a Back Torque reducing generator when driven as a motor will produce an output torque substantially equivalent in magnitude to the Back Torque that would be produced by running the device as a generator.
[0017] As noted, existing designs also create Back Torque which necessitates the input of additional mechanical torque from the prime mover equal in magnitude to the generator's reverse torque in order to overcome the Back Torque and produce the desired power. Other drawbacks also exist.
[0029] Thus, for some embodiments, the electrodynamic machine's output frequency effectively involves a relativistic effect, which introduces harmonics under controlled conditions, and has an effect upon both voltage wave shape, and the system periodicity. For some embodiments, the net effect is that a two pole Back Torque reducing machine as disclosed herein can provide its load with a 60 cycle output while turning at an angular speed of 1800 RPM, as opposed to a conventional device which must turn at 3600 RPM to achieve the same effect with two poles. Subsequently, a four pole electrodynamic machine as disclosed herein may enable a shaft speed of only 900 RPM to produce a 60 cycle output. Therefore, in some embodiments, one advantage of the disclosed designs is to provide an electrodynamic machine capable of producing higher-frequency output, per shaft revolution, per pole set than is found in existing devices.
[0042] As shown in FIGS. 1-4, and 10A and 10B some embodiments of the disclosed electrodynamic machine 20 may comprise a stator assembly 22 and a rotor assembly 30 disposed within a housing 12. For some embodiments, the stator assembly 22 may generally form a hollow cylinder which may be formed of a highly permeable material, silicone steel laminations, sintered steel alloys, special solid steel forms, distributed air gap material, or the like, and is provided with pole pieces 23 which extend radially inwardly and terminate in concave faces 23a. While two pole pieces 23 are evident in the cross sectional views of FIGS. 1-3, the presently disclosed embodiments incorporate 2N poles in a multi-pole configuration, where N is an integer. For example, the cross sectional view of FIG. 4 illustrates a four pole (N=2) embodiment.
[0045] Of course, the slots should be of sufficient depth and width to insure that the power windings 26 disposed in them do not protrude into the air gap 42. Other configurations of power windings 26 are also possible.
[0048] In some embodiments, the form of the rotor 34 as shown in FIG. 1, is a section of a cylinder having a diameter D and an axis A, which is cut by two parallel planes "B" and "C." In one embodiment, angle "α," between planes C and shaft 32 may be 45 degrees. Other angles are also possible.
[0050] FIG. 3 shows an embodiment of the rotor assembly 30 after a movement of 180 degrees from the position shown in FIG. 1. The areas on the rotor edge 35 and a portion of the faces of the pole pieces 23 are referred to herein as coupling zones 37 and pole face flux zones 39, respectively. As described herein, for some embodiments pole face flux zones 39 oscillate along the length of each pole face 23a with periodic motion (e.g., simple harmonic motion) as the rotor assembly is revolved. Thus, the position of the upper pole flux zone 39 as shown in FIG. 1 is located at the right-hand end of the pole face, while the same zone 39 as shown in FIG. 2 is located near the center of symmetry of the power winding 26, and as shown in FIG. 3, this zone 39 has travelled to the left-hand end of the pole face 23a. Thus, as the rotor assembly 30 turns through the next 180 degrees, the flux zones 39 return to the position shown FIG. 1. Thus, for these embodiments, these zones 39 execute periodic motion (e.g., simple harmonic motion) back-and-forth along the pole faces 23a.
[0054] Likewise, in some embodiments, the arbor 36a may comprise any suitable arbor or mounting mechanism for securing the rotor stack 34 to the shaft 32. For example, in some embodiments, where rotor stack 34 comprises a laminate stack, it may be desirable to use a compression arbor 36 that facilitates the securing and positioning of the laminate. Furthermore, arbor 36 may be formed from any non-magnetic alloy, compound or element which may serve to enhance generator performance. Of course, other arbors 36 may be implemented depending upon factors such as the type of shaft 32, design of the rotor stack 34, as well as other factors.
[0056] Further, in some embodiments the stack 34 is fashioned to present a substantially cylindrical profile, such as one described with reference to FIG. 9, thereby ensuring an air gap with the stator of constant, or substantially constant, dimension at the cost of a relatively slight increase in magnetic circuit length. Such an arrangement facilitates a minimum change in magnetic potential energy across the air gap, thereby restricting the dΦ/dt voltage to a minimum, while allowing the speed voltage to have maximum effect upon the electric circuit as the flux interacts with the conductors imbedded in the wire slots of each pole face. This process highlights the exact opposite parameters found within embodiments of a Back EMF reducing motor, such as those disclosed in the related applications noted above, thereby maximizing the difference between embodiments of generator and motor geometries.
[0059] Some embodiments of the device include multipolar arrangements with salient poles placed at 90 degree intervals, or sub-divisions thereof, such as 45 degrees, 22.5 degrees, etc. However, a particular device's physical constraints (e.g., space limitations), as well as magnetic constraints (e.g., interference from adjacent poles) should be considered as necessary for a given application of the device.
[0060] As discussed, in some embodiments, each salient pole projection 23 supports an electrical winding or coil 24 that develops a magnetic field in response to the passage of a current through the field winding 24. This field provides a magnetic force which acts upon, and is correspondingly acted on by, the rotor assembly 30.
[0070] In some embodiments, the motion of the rotor 34 causes a simple harmonic motion of the magnetic flux across the pole faces, such that, despite the substantially constant flux density, the flux position becomes a direct function of shaft speed. Hence, actual flux velocity across each pole face becomes proportional to some maximum flux density value, B, times the simple harmonic velocity, v. Accordingly, the speed voltage, Vs=B(vmax sin cot); this equation represents the motional portion of the induced voltage. However, considering the "transformer voltage" component, Vt, which is equal to some expression involving dΦ/dt. Therefore, the total voltage will be the sum of the speed voltage Vs, and the transformer voltage Vt, with a mathematical result approximating VTotal=[B(vmax sin ωt)]+(dΦ/dt).
[0077] The basis of this concept can best be grasped by referring to FIG. 6A. This drawing shows an embodiment with an elliptical rotor 34 pictured within its cylindrical surface of revolution. At the instant depicted, the rotor 34 is so positioned that the flux is centered on each pole face, and is passing through the axis of symmetry of elliptical rotor 34. As rotation proceeds, from left to right, the flux in the left pole face is moved in a downward direction, and begins to induce a voltage in 23a, the flux in the right pole face is moved in an upward direction and begins to induce a voltage in 23b. Assume for simplicity and by way of example, that the power coils 26 are connected in additive series, and that their output is short circuited. This will ensure that the windings are the only active components in the circuit, and that the power produced in them will be substantially reactive. As current starts to build within the coils 26, an opposing force due to the Lenz reaction will attempt to thrust the flux in a direction opposite to that of its motion. This thrust will be parallel to the axis of rotation of shaft 32, and in an opposite sense for each pole 23. The action of these forces upon the rotor 34 will be analogous to that of followers in the groove of a cylindrical cam. Hence, these lateral thrusts will be converted into "diluted" torques that oppose the effort of the prime mover for one quarter cycle, and provide assistance over the next quarter cycle.
[0084] As explained herein, and with reference to FIGS. 7A and 7B, the disclosed machine will experience two distinct, internal flux movements, each of which may induce eddy currents of different directions within the machine steel. FIG. 7A is an illustration of a portion of some stator lamination plates 1010 in accordance with some embodiments of the disclosed machine. Each lamination plate 1010 may also comprise an insulating coating 1012 on the outer surfaces. As shown, a magnetic flux field 1014, indicated as coming out of the page by the dots as shown, experiences a first velocity (v1) indicated by arrows 1016 pointing to the right, and an electric field (E1), indicated by the arrows 1018 pointing to the top of the figure. This field (E1) produces a relatively insignificant eddy current because the insulating coating 1012 between each plate inhibits the current flow. However, as shown in FIG. 7B, when a second direction of motion (v2) is experienced as indicated by the arrows 1020, such motion will produce a second electric field (E2) as indicated by the arrows 1022. Because this field (E2) is established between the insulating coatings 1012, eddy currents (I) as indicated by arrows 1024 will flow within the metal lamination plates 1010.
[0085] FIGS. 8A and 8B illustrate an end view and a side view of stator pole arrangements in accordance with some embodiments of the disclosed machine that enable the minimizing of the eddy currents in the salient poles due to flux movement in two directions as described above. As shown for this embodiment, a stator pole may comprise a top pole piece (called a shoe) comprising vertically disposed laminations 1028. A bottom portion of the pole may comprise standard, or radially disposed, laminations 1030. Other arrangements of laminations are also possible, the concept being that the layers of the various portions are arranged to minimize eddy currents by inhibiting current flow.
[0086] Also illustrated for this embodiment in FIGS. 8A and 8B are stator field windings 1026 for generating the magnetic flux fields, rotor 1032, rotating about an axis of rotation 1034, and constant air gap 1036 between the edge of rotor 1032 and stator shoe 1028. Not shown here, are the power windings 26 which are used in generator action. For some embodiments, power windings 26 may reside at or in slots within shoe 1028.
[0087] Additional embodiments of stator poles may also be implemented to minimize eddy currents. For example, another embodiment is to have the pole face, or shoe 1028, made of a material such as sintered steel, ferrite, or distributed air-gap material, and then bond, or otherwise fasten, the shoe 1028 to the bottom portion 1030 of the stator pole. Likewise, other embodiments may also implement stator pole pieces comprising grain-oriented steel, with the grain best oriented for lateral flux movement. Embodiments employing combinations of these techniques for eddy current minimization are also possible.
[0088] Likewise, for some embodiments, the salient poles are designed to be as short as is optimal in order to optimize the overall magnetic circuit length. This has the advantage of also lessening iron losses.
[0089] Finally, for some embodiments, the design of the pole field windings (e.g., windings 1026) is to be of adequate wire size, but with a number of turns that is optimal. This has the advantage of keeping I2R (i.e., copper) losses to a minimum. The wire size and number of turns are preferably optimized so that enough turns are used to establish a magnetic flux of sufficient magnitude, while also keeping the I2R losses to an optimal minimum. Typically, relative to a comparable conventional machine, the presently disclosed stator designs will accommodate a greater number of windings per pole because each pole contains both field coils and power coils.
[0092] FIG. 9 illustrates a conceptual diagram of the generation of an ellipse that, when rotated, has a circular cross-section. As shown, such an ellipse can be generated by drawing a reference circle c with a radius r. Projecting out of the plane of the circle c, a height h is generated from r sin α, where α is that angle of inclination of the hypotenuse R (of triangle a0b) from the plane of circle c, and where θ represents the angles generated about the point 0 in the plane of circle c. Thus, the triangle a0b is formed having a radius value of R=(r2+(r sin α)2)1/2. If the height (h) of the triangle a0b is varied sinusoidally in accordance with the angle θ, then for a given θ, the instantaneous angle of slope may be calculated by the following relation, S=A tan (cos α). Plotting an infinite number of similar triangles about 0 for the full 360 degrees of circle c produces an ellipse of perimeter ep as shown in FIG. 9. Ellipse ep will always have a circular cross-section when rotated about 0 in the plane of circle c. Additional rotor designs suitable for implementation of the concepts presently disclosed are also possible.
[0093] Another aspect of embodiments of the disclosed electrodynamic machine may be illustrated with reference to performance under the application of an electrical load to the device. The application of a load to most conventional generating devices produces a secondary magnetic field which opposes the generator's field flux, thereby causing a reduction in output voltage. This "voltage drop" is then countered by increasing the current delivered to the device's field windings, which in turn boosts the output voltage. However, the presently disclosed electrodynamic machine has the heretofore unexpected behavior of increasing its rotational speed as the output impedance approaches a short circuit.
[0095] While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. Accordingly, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the claims and their equivalents.
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