Generator with multiple stators

Abstract

A generator includes a rotor and a plurality of stators coaxially and concentrically arranged about a central axis. A first stator is disposed concentrically about and adjacent to the rotor, the rotor and the first stator separated by a rotor-stator air gap, a second stator is disposed concentrically about and adjacent to the first stator, the first stator and the second stator separated by a stator-stator air gap. The rotor includes a plurality of pole structures configured to provide or produce a plurality of magnetic poles, and a radially outer surface of each pole structure is curved with an average radius of curvature that is less than an average distance between the outer surface and the central axis. The rotor-stator air gap varies in distance along a circumferential direction, with a shortest distance at a circumferential center of each pole structure and a longest distance at a circumferential end of each pole structure. The stator-stator air gap is of uniform thickness.

Description

Technical Field

[0001] This invention generally relates to generators, and more specifically to generators having a rotor and a plurality of stators. Background Technology

[0002] The applicant noted that the basic design of the generator has not changed over the years. Most generators have a rotor and a stator (the stator enclosing the rotor) or some other rotating combination of these two parts to generate electricity.

[0003] In most cases, the stator accompanies the rotor, and the stator has a return path (sometimes called the back-iron) to guide the magnetic field to complete the magnetic circuit and to make full use of the magnetic field as it moves from one pole to another. The teaching in this field is to have a return path on the axially outer side of the stator (in radial air-gap machines). There has been research and numerous innovations and inventions attempting to optimize and improve the efficiency of generators. Most of these attempts are guided by the mainstream teaching in this field, which instructs the rotor to generate a magnetic field that radiates from the rotor to the stator and through the stator, returning via the return path to form a closed circuit of the magnetic field, thus completing the magnetic field loop.

[0004] This teaching method has proven effective and has been utilized efficiently for many years. US2007 / 0138896 discloses an electric motor, specifically a reluctance motor, having two rotors and two stators; it has an air gap that functions to isolate the two stators from each other so that there is no or only minimal magnetic flux linkage between them. The motor also has a bias magnet device that excites a unidirectional magnetic flux toward the rotor so that the motor rotor can have higher torque. The air gap and permanent magnets work together to provide a direction for the magnetic field and also ensure that the magnetic fields of the stators do not link together.

[0005] Another prior art document is CA2541286. This document discloses two stators spaced apart axially.

[0006] The applicant notes that, as effectively illustrated by the aforementioned patents and prior art, several attempts have been made, and the need to improve the configuration of generators and enhance their performance has long been recognized. A major weakness of these prior art attempts is that they have not adequately realized or utilized the large electric potential in a magnetic field.

[0007] The applicant desires a generator with multiple stators that uses the radial characteristics of the magnetic field to produce improved power output at an affordable cost, which brings commercial benefits. Summary of the Invention

[0008] Therefore, the present invention provides a generator comprising a rotor and a plurality of stators, wherein:

[0009] The rotor and the plurality of stators are arranged coaxially and concentrically around a central axis;

[0010] The rotor is disposed radially inside the plurality of stators;

[0011] The first stator of the plurality of stators is arranged concentrically around and adjacent to the rotor, and the rotor and the first stator are separated by a rotor-stator air gap;

[0012] The second stator of the plurality of stators is arranged concentrically around and adjacent to the first stator, and the first stator and the second stator are separated only by stator-stator air gaps;

[0013] The rotor includes a plurality of magnetic pole structures configured to provide or generate a plurality of magnetic poles;

[0014] The radially outer surface of each of the magnetic pole structures is curved with an average radius of curvature smaller than the average distance between the outer surface and the central axis, thus the rotor-stator air gap varies circumferentially in distance, with the shortest distance located at the circumferential center of each magnetic pole structure and the longest distance located at the circumferential end of each magnetic pole structure; and

[0015] The stator-stator air gap has a uniform thickness.

[0016] In the rotor-stator air gap, the ratio of the longest distance to the shortest distance can range from 30:1 to 2:1, more specifically from 20:1 to 5:1, more specifically from 15:1 to 10:1, and more specifically from 14:1 to 13:1. Although the actual dimensions may be determined by the overall dimensions of the generator, the longest distance can be approximately 135 mm, and the shortest distance can be at least 5 mm.

[0017] The shortest distance at the center of the circumference of each magnetic pole structure can be 5mm–50mm. The longest distance at the end of the circumference of each magnetic pole structure can be 30mm–150mm.

[0018] The stator-stator air gap can be shorter than the shortest distance of the rotor-stator air gap. The stator-stator air gap can be at least 0.25 mm, and more specifically, at least 2 mm.

[0019] A generator may include a back iron. The back iron provides a return path and helps close the magnetic circuit from the rotor's poles. The back iron may be arranged around the plurality of stators, in other words, around the outermost stator. The stator located between the rotor and the outermost stator is the intermediate stator; in a two-stator generator, there will be only one intermediate stator (the first stator), in a three-stator generator, there will be two intermediate stators, and so on.

[0020] Multiple stators can provide one or more of the following purposes:

[0021] It makes more efficient use of the magnetic field generated by the rotor than a single stator generator.

[0022] Windings from multiple stators produce better waveforms compared to windings in a single stator. In the context of this specification, "better waveforms" may mean waveforms that are more sinusoidal, have lower harmonics, and / or are smoother than those produced by a single stator.

[0023] The windings in multiple stators can be connected in parallel with each other.

[0024] A generator may consist of only two stators. A generator may also consist of three or more stators.

[0025] Due to the presence and configuration of multiple stators, the generator can produce a sinusoidal output waveform with a total harmonic distortion of less than 0.8% without the use of waveform correction circuitry, which is a superior and surprising technical result.

[0026] This invention provides a novel method for fully utilizing the magnetic field effectively radiated from the rotor. In prior art designs, the magnetic field from the rotor radiates outward into the stator and then enters a return path. The return path guides the magnetic field back to the next pole of the rotor. This prior art configuration may seem perfectly acceptable and appear to require no additional stator due to at least a century of cultural and technical instruction in the field. According to the proposed invention, which includes two or more stators, it may seem strange at first glance to add a second (or third, etc.) stator near the first without adding more rotors. These prior art patent designs may fail to fully capture the potential in the magnetic field characteristics.

[0027] Another very useful and valuable property of magnetic fields is that when two magnets with opposite polarities are placed, for example, when the stator is in a small air gap with the north pole facing the south pole, the magnetic field strength on both sides increases, and in some cases even doubles. This effect results in a greater rate of change, thus producing a high level of voltage.

[0028] This invention can more fully capture the potential in a magnetic field by including more adjacent stators; these stators can overlap each other concentrically, and they are all concentric with the rotor. The rotor can rotate inside the stators and radiate the magnetic field through the adjacent stators, and then the magnetic field enters the next stator. Attached Figure Description

[0029] The invention will now be further described by way of example with reference to the accompanying drawings.

[0030] In the attached diagram:

[0031] Figure 1A schematic cross-sectional view of a first embodiment of a generator according to the present invention is shown;

[0032] Figure 2 A schematic cross-sectional view of a second embodiment of a generator according to the present invention is shown;

[0033] Figure 3 It shows Figure 1 The waveform of the voltage output of the first stator of the generator; and

[0034] Figure 4 It shows Figure 1 The waveform of the voltage output of the second stator of the generator. Detailed Implementation

[0035] The following description of exemplary embodiments of the invention serves as a practical teaching of the invention. Those skilled in the art will recognize that changes can be made to the described exemplary embodiments while still obtaining the beneficial results of the invention. It will also be apparent that some of the desired benefits of the invention can be obtained by selecting some features of the exemplary embodiments without using others. Therefore, those skilled in the art will recognize that modifications and adaptations to the exemplary embodiments are possible and, in some cases, even desirable and part of the invention. Thus, the following description of exemplary embodiments is provided as an illustration of the principles of the invention and not as a limitation thereof.

[0036] Figure 1 A first embodiment of a generator 100 according to the present invention is shown. Only closely related components of the generator 100 are shown, while more common components (such as bearings, shafts, frames, input drivers, output wiring, etc.) are not shown, but those skilled in the art will understand that they may form part of the present invention.

[0037] The generator 100 has a central rotor 110 mounted to rotate about a central axis 111. The rotor 110 has multiple pole structures 112 configured to provide or generate multiple magnetic poles (e.g., NSNS). Each pole structure 112 has a magnetic element 113, which can be a permanent magnet or an electromagnet. In this example, there are four pole structures 112, making the generator 100 a four-pole machine. Each pole structure 112 can be in the form of a rotor shoe.

[0038] Each magnetic pole structure 112 has an arcuate radial outer surface 114. The radius of curvature of the outer surface 114 is smaller than the distance from the outer surface 114 to the central axis 111. This means that, in use, the outer surface 114 has a stronger curvature than the displacement arc described by the outer surface 114.

[0039] The generator 100 has multiple stators 120 and 130. In this exemplary embodiment, the generator 100 has two stators 120 and 130, namely an inner stator 120 and an outer stator 130. The inner stator 120 is located radially outside and adjacent to the rotor 110, and is separated from the rotor 110 by rotor-stator air gaps 116 and 118. The outer stator 130 is located radially outside and adjacent to the inner stator 120, and the stators 120 and 130 are separated only by a stator-stator air gap 122. The stators 120 and 130 are arranged coaxially and concentrically with the rotor 110 around a central shaft 111; the rotor 110 is arranged radially inside or inside the stators 120 and 130.

[0040] Given the arcuate nature of the outer surface 114 of the magnetic pole structure 112, the rotor-stator air gaps 116 and 118 are non-uniform along the entire length of the outer surface 114. More specifically, the distance between the rotor-stator air gaps 116 and 118 and the inner stator 120 varies circumferentially, with the shortest distance 118 located at the circumferential center of the magnetic pole structure 112 and the longest distance 116 located at the circumferential ends of the magnetic pole structure 112.

[0041] Conversely, the stator-stator air gap 122 has a uniform thickness. Furthermore, the stator-stator air gap 122 is even shorter than the shortest distance 118 of the rotor-stator air gaps 116, 118, and much shorter than the longest distance 116 of the rotor-stator air gaps 116, 118.

[0042] The generator 100 has a back iron 132 surrounding the second stator 130 to provide a magnetic return path for the magnetic field generated by each magnetic pole structure 112.

[0043] Figure 2 A second embodiment of a generator 200 is shown, which includes three stators 120, 130, and 210. The main difference between this generator 200 and the first generator 100 is the inclusion of a third stator 210 radially outside and adjacent to the second stator 130. The second and third stators 130 and 210 are separated by a second stator-stator air gap 212, which may be shorter than or the same as the (first) stator-stator air gap 122 between the first and second stators 120 and 130.

[0044] The generator 200 still has a back iron 132, but the back iron 132 surrounds the third stator 210.

[0045] In testing and simulations, the applicant has found two main advantages to adding a second stator 130 (and optionally more stators):

[0046] Stator 120, 130, and 210 generate more power from the same rotor 110; and

[0047] The generated power waveform has lower harmonics, meaning it is closer to a pure sine wave than the waveform generated by a single stator. In other words, each individual stator (120, 130, 210) can produce a low-harmonic voltage output.

[0048] Regarding the first advantage, the applicant speculates that more of the stators 120, 130, and 210 "consume" or utilize the available magnetic field generated by the rotor 110. In the simulation, the second stator 130 generated approximately 80% more power than the first stator 120, which is significant. However, this comes at the cost of increased machine complexity.

[0049] The applicant hypothesizes that 2-3 stators are likely the optimal choice, meaning that 2-3 stators offer the best return on investment between power generation and machine complexity / cost. While more stators (4 or more) would still generate some additional power, the law of diminishing returns may not make so many stators feasible. More specifically, the first stator 120 generates power (at least at lower voltages below 700V), the second stator 130 generates more power than the first stator 120, and the third stator 210 (in the case of generator 200) generates more power than the second stator 130. However, the rate of increase in power generation from the second stator 130 to the third stator 210 is small (e.g., less than the increase from the first stator to the second stator), but this may still be meaningful and improves generator performance and its economics. Furthermore, the applicant has noted that the power factor of generators 100, 200 (or generators with more stators) does indeed decrease with increasing stator count, but this can be corrected to an improved or acceptable level.

[0050] Another advantage of generator 100 is that the rotational losses and magnetic field generation losses associated with rotor 110 are experienced only once, because there is only one rotor 110, whereas multi-rotor, multi-stator machines may experience additional rotor-related losses. Another advantage is that multiple stators 12, 130, 210 with one rotor 110 generate several times more power than a single stator.

[0051] In some embodiments, the rotor-stator air gaps 116, 118 may be at least 5 mm at the midpoint of the magnetic pole structure 112 (in other words, at the shortest distance 118), and uniformly increase to 35 mm at both ends of the magnetic pole structure 112 (at the longest distance 116).

[0052] Stator 120, 130, and 210 are cylindrical, with uniform circumferential shapes on both their inner and outer surfaces. Since stator 120, 130, and 210 overlap concentrically and are separated by their respective stator-stator air gaps 122 and 212, these air gaps are uniform across the entire circumference, ranging from 0 mm to 150 mm. Shaping the magnetic flux in the stator-stator air gaps 122 and 212 to manipulate the output waveform to a sinusoidal curve may not be necessary, as the sinusoidal (or near-sinusoidal) waveform is automatically generated by the shapes of rotor 110 and rotor-stator air gaps 116 and 118 and propagates through stator 120, 130, and 210. In some embodiments, the stator-stator air gaps 122 and 212 may be at least 0.25 mm or approximately 2 mm.

[0053] It will be apparent to those skilled in the art that stators 120, 130, and 210 include many features common to stators: teeth and slots, with windings housed in the slots. The magnetic field generated by rotor 110 induces a current in the windings. The magnetic field from rotor 110 may decrease and weaken as it passes through the multiple air gaps 116, 118, 122, and 212 and stators 120, 130, and 210.

[0054] Each stator 120, 130, 210 may include a stator body to provide rigidity, the stator body defining teeth and slots. The stator body may be made of a magnetite material, which may include magnetite and a binder. The magnetite material may be in the form of finely ground magnetite, bonded with resin and hardened. This allows a certain degree of magnetic field generated by the rotor 110 to pass through the inner stator 120 and interact with the other stators 130, 210. The increased magnetic field means that as the rotor 110 rotates, the rate of change of the magnetic field on the stators 120, 130, 210 increases, even affecting the stators located at the outermost stators 130, 220 of the generators 100, 200. When the stator-stator air gaps 122, 212 are small, i.e., within the range of less than about 10 mm, the effect may be amplified. This effect occurs on adjacent stators 120, 130, 210.

[0055] Figures 3-4 The voltage waveforms 300 and 400, induced or generated in the windings of the first and second stators 120 and 130, respectively, are shown. In this configuration, the stator-stator air gap 122 is 5 mm. The generator 100 is fed with a current of 800 A and a field current of 60 A.

[0056] The applicant speculates that there may be methods and techniques for increasing the magnetic field strength or coupling in stators 130 and 210 after the inner stator 120. For example, another method to increase the magnetic field from rotor 110 as rotor 110 passes through air gaps 116, 118, 122, 212 and stators 120, 130, 210 is to place the secondary windings on stators 120, 130, 210 in a closed circuit; these secondary windings could be located above stators 120, 130, 210, where they are isolated from the primary generating windings in stators 120, 130, 210. These secondary stator windings may not have any current input to them. The structural features of these secondary windings are that they can be completely embedded in the stator body. As the rate of change of the magnetic field changes, the magnetic field is connected to them, and they will generate current in them. This will generate a magnetic field, which will be amplified by the electric steel. This magnetic field will radiate outward to the generating windings in the slots of the same stator, and will also radiate outward to the adjacent stators 130 and 210 through the stator air gaps 122 and 212.

[0057] When one or more stators 120, 130, 210 are made entirely of magnetite mixed with resin, the magnetite can also amplify the magnetic field. For the same thickness, magnetite material has better radial magnetic dispersion than electrical steel. These windings can be wound around the circumference of stators 120, 130, 210.

[0058] Another embodiment of increasing the magnetic field challenge is to completely embed the primary power generation windings into the body of stators 120, 130, and 210; this structure can be based on electrical steel as the basic material for manufacturing stators 120, 130, and 210. The material for manufacturing stators 120, 130, and 210 can also be a magnetite material mixed with resin.

[0059] In embodiments where the stator body is made of electrical steel, the power generation winding is embedded in a magnetite surface layer on the winding surface to increase the electric field. Finely ground magnetite has high electric field characteristics, and its use can increase the working electric field on the stator winding. In this embodiment, stators 120, 130, and 210 may not have slots to position the windings because the windings will be located inside stators 120, 130, and 210. Secondary windings may be located in all stators; these secondary windings may be located in stator 130 to generate a magnetic field radially inward to the inner adjacent stator 120, an outward to the adjacent outer stator 210, and enter the return path 132 of the outermost stator 210.

[0060] The primary generating windings embedded in the electrical steel structure of stators 120, 130, and 210 can also radiate the magnetic field radially inward to adjacent inner stators 120 and 130, and outward to adjacent outer stators 130 and 210, towards the return path 132. The return path 132 can be made larger to have sufficient permeability to accommodate the increased magnetic field. A potential challenge in this embodiment is the cooling of the stator windings. In this embodiment, cooling can be effectively handled by water cooling of stators 120, 130, and 210. The primary windings embedded in the stators and the secondary windings embedded in stators 120, 130, and 210 can be located in the same stators 120, 130, and 210, and / or both the primary and secondary windings can be surface-adhered to or embedded with magnetite.

[0061] As described above, in some embodiments, the use of magnetite material may be suitable, particularly for the structural / body portions of stators 120, 130, and 210. The stator-stator air gaps 122 and 212 can be very small: ranging from approximately 0 mm to approximately 10 mm, for example, 5 mm. Due to the small size of the stator-stator air gaps 122 and 212, the airflow for cooling stators 120, 130, and 210 may be reduced, and therefore cooling may be less effective.

[0062] Fine magnetite possesses excellent thermal properties as a material. Experimental work has shown that magnetite materials mixed with resin release heat to the surrounding environment much faster than many electrical materials. Magnetite also heats up slowly. Magnetite materials for electrical applications have many advantageous properties; one application of magnetite is in generators.

[0063] The return path 132 can be larger and have a greater thickness. The dimension of the return path 132 in terms of its thickness can be one of the characterizing features of the invention. Compared to conventional designs and prior art, the return path 132 of the present invention can always be thicker than the return path of the prior art, even with a smaller magnetic field and a larger stator. When the return path 132 becomes thicker, the generator 100 is able to generate more power.

[0064] In basic, existing-technology generators (i.e., those with a single central rotor and a single stator around the rotor, and without any waveform correction circuitry), the voltage harmonics of the output waveform can be high. In this disclosure, generator 100 provides an unexpected and somewhat surprising technical result: a smoother voltage waveform, resulting in smoother torque on rotor 110, a smoother air gap flux density between rotor 110 and inner stator 120, and also providing a smoother air gap flux density between stators 120 and 130. These smoothing technical results are applicable to all subsequent stators 210 of generator 200.

[0065] The generator 100 has the advantage of low harmonic distortion. The generator can have a total harmonic distortion (THD) of less than 1%, and can have a THD of approximately or less than 0.8%. In a particular embodiment, the shortest distance 118 of the rotor-stator air gaps 116, 188 is at least 35 mm, the longest distance 116 is 75 mm, and the stator-stator air gap is 10 mm and circumferentially uniform. In this embodiment, the generator 100 produces an output waveform with a THD of less than 0.8%. For power generation, the standard requirement for harmonics is below 8%, and the generator 100 therefore performs well below this threshold without any additional waveform correction or shaping circuitry.

[0066] This low THD provides an opportunity to more aggressively configure the generator to produce more current—a practice typically associated with increasing THD, but which can be done close to the 8% limit and extract more power while keeping harmonic distortion below an acceptable THD threshold. In this embodiment, both stators generate low voltage harmonics. Low voltage harmonics can provide significant economic benefits, as the increased current will generate more power and increase economic efficiency, leading to economic success. This low harmonic benefit addresses the high harmonic limitations of conventional prior art generators.

[0067] Another point to note is that the outer stator 130 has a larger radius than the inner stator 120, and therefore a larger area for providing the teeth and windings within them. This can contribute to power generation. The greater the increase in stator size, the greater the increase in voltage generated due to the increase in integral surface area. Therefore, the more stator size and the larger the radius, the more voltage is generated, even with the same number of turns per phase. This also results in better economic efficiency and leads to economic success.

[0068] The generator 100 can be operated in different modes to adapt to different customer or grid conditions. Both stators 120 and 130 can operate under load. Alternatively, the generator 100 can operate with the inner stator 120 unloaded and the outer stator 130 under load (i.e., under less demand). The inner stator 120 can mitigate the magnetic field, where the power output may still have low voltage harmonics in the outer stator 130. The reason for choosing to operate the stator 120 unloaded is that, at higher voltages above 700V, it produces the smallest amount of power compared to all other stators due to its radius size. The fact that one stator is unloaded does not affect the power quality in terms of voltage harmonics. In other words, even when one stator 120 is operating unloaded, the other stator 130 under load still has favorable or low THD characteristics. Therefore, even if one stator 120 is unloaded, its mere presence or proximity to the other stator 130 still provides technical benefits. Compared to a traditional design with one rotor and one stator, even if a single stator is the same size as a combination of three or two stators, the multi-stator design performs relatively better due to the technical effects of low voltage harmonics.

[0069] The result of operating the inner stator 120 under no-load conditions is likely a reduction in the opposing mechanical effects on the rotation of the rotor 110 and the cogging torque from the other stators 130, thus resulting in smoother and improved operation of the generator 100. Any other stators 130, 210 can operate under no-load conditions to adjust for power demand. Also considering power demand, the outer stators 130, 210 may not be the preferred stators for no-load operation. This embodiment provides some operational flexibility for the generators 100, 200. This characteristic of low harmonics overcomes the limitations caused by relatively high levels of harmonics in conventional technologies. The generators 100, 200 can operate flexibly, whereby at least one stator operates under load while the others operate under no-load conditions, or at least one stator operates under no-load conditions while the others operate under load conditions, and still generate low harmonic voltages. This operating mode can improve the smooth operation of the generators 100, 200.

[0070] Generators 100 and 200 may have a support structure (not shown). The support structure may include a single back iron 132 for all stators 120, 130, and 210. All stators 120 and 130 except the outermost stators 130 and 210 may be supported by tie rods to reinforce and hold them together to prevent any movement. The tie rods that can be used for these stators 120, 130, and 210 may include a 10.9 structural steel grade to achieve the required strength.

[0071] Another method to support the intermediate stators 120 and 130 is to use a non-magnetic and non-conductive material as a support structure in the form of a tie rod. This will not affect the direction of magnetic field flow on its path to the windings and will not generate unwanted magnetic interference.

[0072] The proposed generator 100 has a rotor and multiple adjacent stators, and is a simple solution for generating more power with a single rotor. The defining characteristic of generator 100 is the multiple stators, possibly at least two. This invention opens a new avenue for generating more power with a single rotor, and by doing so, significantly improves upon the prior art with superior low-harmonic characteristics, thus giving the invention its technical significance. The synergistic effect of factors such as a larger outer stator, the integral of the stator surface area, and the doubling of the magnetic field when the two stators face each other works together to increase the voltage output of generator 100.

[0073] In some embodiments, the return path may be up to ten times thicker than in prior art inventions. For rotors of the same size, the optimized return path of the present invention can be at least 1.5 times thicker than an optimized conventional design. The thickness of this back iron (sometimes referred to as the return path) can be at least 2 mm. When the return path becomes thicker, the generator is able to produce more power even while maintaining the same field current and the same stator current, but by increasing the thickness of the return path, the generator produces more power by generating more voltage. This is a surprising and very advantageous technical achievement, and therefore a thicker return path may be a prominent feature of generator 100. For generator 100, the return path is always located at the outermost stator of the present invention. The return path can be thicker than the second stator or the outermost stator.

[0074] Another embodiment of the invention is that, since the invention has multiple stators and one rotor, there is an embodiment in the generator in which the rotor has multiple stators and a dummy stator. The difference is that, in addition to multiple stators, the generator may also include a dummy stator, arranged concentrically with the multiple stators, characterized in that it has no working windings.

[0075] Terms and Conditions

[0076] 1. A generator having a plurality of stators, wherein the generator has a rotor as the innermost part of the generator, having at least two concentric stators, wherein the air gap between the rotor and the innermost stator is at least 10 mm at the midpoint of the outermost surface of the rotor pole, the air gap increases uniformly to at least 50 mm at both pole ends, and the air gap between adjacent stators is at least (zero) 0 mm around the circumference of the two adjacent stators.

[0077] 2. The generator according to Clause 1, wherein each intermediate stator has a thin layer of electrical steel as a backing for stator support, the backing having a thickness of at least 2 mm.

[0078] 3. The generator according to Clause 1, wherein the teeth of adjacent outer stators are connected to the back surface of the preceding (adjacent) stator to support the intermediate stator between the rotor and the outermost stator.

[0079] 4. The generator as described in Clause 1, wherein tie rods comprising grade 10.9 structural steel are used for supporting the intermediate stator between the rotor and the outermost stator.

[0080] 5. The generator according to Clause 1, wherein a non-magnetic and non-conductive material is used as a support structure for an intermediate stator located between the rotor and the outermost stator.

[0081] 6. The generator according to Clause 1, wherein the air gap between the stators is 5 mm around the stator circumference.

[0082] 7. The power generation method according to Clause 1, wherein the air gap between the inner stator (S1) and the outer stator (S2) is 5 mm, which generates a smoother sinusoidal waveform with lower harmonics of less than 0.8%.

[0083] 8. The power generation method according to Clause 1, wherein at least one stator winding is embedded in finely ground magnetite or magnetite mixed with resin, wherein the magnetite increases the electric field.

[0084] 9. The method of generating electricity in a generator according to Clause 1, wherein at least one stator has one of the following windings:

[0085] The upper part of the stator has a secondary winding, which is isolated from the stator's generating winding. No current is input into the secondary winding, but it generates a magnetic field through rotor motion. This magnetic field is amplified by the rotor and added to the rotor's magnetic field; or

[0086] The generator winding is fully embedded in the electrical steel stator structure to generate a larger magnetic field, which is amplified by the steel structure and cooled by water.

[0087] 10. The generator according to Clause 1, wherein the return path is pasted with magnetite to increase the magnetic field on the stator.

[0088] 11. The generator according to Clause 1, wherein a thin layer of steel on the back side of the intermediate stator is bonded with magnetite.

[0089] 12. The method of generating electricity in a generator according to Clause 1, wherein the stator closest to the rotor is operated under no-load conditions, and the opposing mechanical effects on rotor rotation and the cogging torque from the other stators are reduced.

[0090] 13. The method of generating electricity in a generator according to Clause 1, wherein at least one intermediate stator between the rotor and the outermost stator is operated under no-load conditions, while all other stators are operated under load.

[0091] 14. A generator having multiple stators, wherein the generator has a rotor as the innermost part of the generator, and has at least two concentric stators radially positioned with respect to the rotor, wherein there is a rotor-stator air gap between the rotor and the innermost stator, and a stator-stator air gap between adjacent stators.

Claims

1. A generator comprising a rotor and a plurality of stators, wherein: the rotor and the plurality of stators are coaxially and concentrically arranged about a central axis; the rotor is disposed radially inward of the plurality of stators; a first stator of the plurality of stators is disposed concentrically about and adjacent to the rotor, the rotor and the first stator separated by a rotor-stator air gap; a second stator of the plurality of stators is disposed concentrically about and adjacent to the first stator, the first stator and the second stator separated by a stator-stator air gap; the rotor comprises a plurality of pole structures configured to provide or produce a plurality of magnetic poles; a radially outer surface of each of the pole structures is curved with an average radius of curvature that is less than an average distance between the outer surface and the central axis, the rotor-stator air gap thus varying in distance along a circumference, a shortest distance being at a circumferential center of each of the pole structures and being 5 mm to 50 mm, a longest distance being at a circumferential end of each of the pole structures and being 30 mm to 150 mm; the stator-stator air gap is of uniform thickness and is at least 0.25 mm; the stator-stator air gap is shorter than the shortest distance of the rotor-stator air gap; the generator comprises a back iron configured to provide a return path and to help close a magnetic circuit from the poles of the rotor, wherein the back iron is disposed about the plurality of stators; the back iron is at least 2 mm thick; and the generator produces a sinusoidal output waveform with less than 1% total harmonic distortion without the use of a waveform correction circuit.

2. The electric generator of claim 1, wherein, a ratio of the longest distance to the shortest distance is in a range of 30: 1 to 2:

1.

3. The electric generator of claim 1, wherein, the longest distance is 135 mm.

4. The electric generator of claim 1, wherein, the back iron is disposed about an outermost stator.

5. The electric generator of claim 1, wherein, the plurality of stators work together to form a better output waveform with lower harmonics from windings in the plurality of stators than a single one of the plurality of stators.

6. The electric generator of claim 1, wherein, the sinusoidal output waveform has less than 0.8% total harmonic distortion without the use of a waveform correction circuit.

7. The generator of claim 1, comprising at least three stators, the first stator, the second stator as an intermediate stator, and a third stator as an outermost stator, the third stator disposed concentrically about and adjacent to the second stator, the second stator and the third stator separated by a second stator-stator air gap.

8. The electric generator of claim 1, wherein, teeth of the second stator are connected to a back face of the first stator for support.

9. The generator of claim 1, comprising tie rods comprising steel disposed between adjacent stators for support of the adjacent stators.

10. The generator of claim 1, comprising a non-magnetic and non-conductive material used as a support structure between adjacent stators.

11. The generator of claim 1, comprising a virtual stator in addition to the plurality of stators, the virtual stator being concentrically arranged with the plurality of stators, the virtual stator characterized in that the virtual stator is devoid of working windings.

12. A method of operating a generator according to claim 11, wherein: all of the plurality of stators are operated under load; or all but one of the plurality of stators are operated under load and one of the plurality of stators is operated under no load.

13. The method of operating a generator of claim 12, wherein, the virtual stator is operated under no load.

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