High torque density electric motor

Abstract

The present disclosure describes a magnetic geared device configured as either an electric motor or a generator. The device includes at least a stator structure and a rotor structure arranged to improve torque generation. The stator structure includes N≧1 stator cores and a shared toroidal electrical winding, and the rotor structure includes an equal number of corresponding rotor cores. The device may be a vernier machine. The device may include one or more thermal channels configured to transport heat from the stator structure. Methods and systems for manufacturing the device are also described. TIFF2025515137000007.tif77128

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 364,110, filed May 3, 2022, the entire contents of which are incorporated herein by reference.

[0002] Field The technology relates generally to electric motors and generators. [Background technology]

[0003] background Electric motors are used in a wide range of applications, from powering fans and compressor pumps in heating, ventilation, and air conditioning (HVAC) systems, to driving the wheels of electric vehicles (EVs), to powering the propellers of boats, electric aircraft, or unmanned aerial vehicles (UAVs). Currently, there is an explosion of electrification, from electric vehicles to small and medium sized electric UAVs for the urban air mobility (UAM) market, to new electric manned aircraft. This explosion continues in the space of robotics and automated machines that require precise positioning. These new applications require lightweight and compact motors, especially to power mobile platforms where weight and size are critical.

[0004] Electric motors produce two things: they produce torque (torsional force) and power. Power is defined as the product of torque and shaft speed. Power can be increased by increasing torque and / or speed. Traditionally, lightweight, high power density motors have been made by running them at very high speeds (>10,000 RPM) where it is easier to make them lighter, and then using a reduction gearbox to produce the shaft speed and torque required for the load. In this regard, many modern electric vehicle motors rotate at 12,000-16,000 RPM and then use a reduction gearbox of about 8:1 to deliver torque to the wheels. Other recent motor types, such as direct drive ironless motors, achieve a light weight for the required torque and power, but must use very large diameters at low rotational speeds. Loads such as propellers typically rotate at slower speeds to maximize aerodynamic efficiency, ranging from 150 RPM for helicopters, up to about 1,000 RPM for manned electric vertical take-off and landing (eVTOL) aircraft, and up to about 3,000 RPM for fixed-wing aircraft. In robotics applications, driven joints rarely rotate continuously, but rather move from controlled position to position, so peak joint speeds are typically well below 1,000 RPM, and robots typically require very compact motors with very high torque and low speed. Summary of the Invention

[0005] [Brief description of the drawings]

[0006] [Figure 1A] FIG. 1A illustrates a stator for an electric motor topology (concentrated windings, outrunner type) that provides high power density but low torque density. [Figure 1B] FIG. 1B illustrates a stator for a heavy motor topology (vernier, inrunner) that provides high torque density. [Figure 1C]1C illustrates a stator for a motor topology (vernier, toroidal wound, double air gap) according to an exemplary embodiment of the present disclosure. The motor of FIG. 1C provides both high power and high torque density. [Diagram 2] FIG. 2 illustrates a schematic of a motor architecture including an end-turn sandwich construction, oil bath liquid lubricated bearings, and a dual air gap vernier electromagnetic system with integrated power electronics, in accordance with some embodiments of the present disclosure. [Figure 3A] FIG. 3A illustrates a dual gap radial flux machine structure according to some embodiments of the present disclosure. [Figure 3B] FIG. 3B illustrates a dual air gap axial flux machine structure according to some embodiments of the present disclosure. [Figure 4] FIG. 4 illustrates a three-gap (two radial, one axial) flux machine structure according to some embodiments of the present disclosure. [Figure 5A] 5A and 5B are schematic illustrations of motor designs using a Vernier electromagnetic system with a dual air-gap radial flux configuration and Halbach array rotor magnetization according to some embodiments of the present disclosure, with Fig. 5A illustrating a machine with a pole ratio = 5:1 and Fig. 5B illustrating a pole ratio = 11:1. [Figure 5B] See legend to Figure 5A. [Figure 6] FIG. 6 illustrates an open slot toroidal winding detailing the use of a wide flat ribbon made from multiple parallel strands of magnet wire in accordance with some embodiments of the present disclosure. [Figure 7] FIG. 7 illustrates a schematic diagram of a double air gap Vernier machine having a Halbach rotor magnet arrangement constructed as a radial flux machine, in accordance with some embodiments of the present invention. [Figure 8] FIG. 8 illustrates a schematic diagram of a double air gap Vernier machine having a Halbach rotor magnet arrangement constructed as an axial flux machine, in accordance with some embodiments of the present invention. [Figure 9]9 illustrates a schematic of a three-gap machine, two axial flux gaps and one outer radial flux gap, according to some embodiments of the invention. This embodiment uses heat pipes in the cooling channels for both mechanical attachment of the stator core to the stator structure and for thermal transport. [Figure 10] FIG. 10 illustrates a schematic of a three-gap variation having two radial flux gaps and one axial flux gap, according to some exemplary embodiments of the present disclosure. [Figure 11] FIG. 11 illustrates a schematic of an axial flux double gap machine with integrated power electronics and cooling according to some embodiments of the present disclosure. [Figure 12] 12A and 12B illustrate schematics of a fully assembled dual air gap axial flux machine with axial cooling airflow driven by rotor housing integral fan blades according to some embodiments of the disclosure. [Figure 13A] 13A-D generally illustrate an assembly procedure for a stator end-turn cooling sandwich structure according to some embodiments of the present disclosure. [Figure 13B] See legend to Figure 13A. [Figure 13C] See legend to Figure 13A. [Figure 13D] See legend to Figure 13A. [Figure 14] FIG. 14 illustrates a liquid cooling architecture for an axial flux design according to some embodiments of the present disclosure. [Figure 15] FIG. 15 illustrates an example thermal FEA simulation of a radial flux vernier machine using heat pipes according to some embodiments of the present disclosure. [Figure 16] 16A and 16B illustrate 3D electromagnetic (EM) FEA simulations of eddy currents induced in different aluminum end-turn sandwich construction approaches according to some embodiments of the present disclosure. [Figure 17]17A and 17B illustrate an example of a wound aluminum coil having electrically insulated surfaces to block eddy currents, according to some embodiments of the present disclosure. [Figure 18] 18A, 18B, and 18C illustrate examples of axial flux dual gap end turn sandwich designs utilizing rectangular heat pipes according to some embodiments of the present disclosure. [Figure 19] 19A and 19B illustrate a larger motor made by axially stacking motors, according to some embodiments of the present disclosure. [Figure 20] 20A-20E show aspects of a dual gap radial flux embodiment according to some embodiments of the present disclosure. [Figure 21] 21A and 21B illustrate a rotor implemented with a Halbach array of magnets, according to some embodiments of the present disclosure. [Figure 22] FIG. 22 illustrates a split-tooth vernier stator in the form of a radial flux outrunner, according to some embodiments of the present disclosure. [Diagram 23] 23A and 23B show diagrams of a five-gap axial flux motor according to some embodiments of the present disclosure. [Figure 24] 24A and 24B show diagrams of a three-gap axial flux motor according to some embodiments of the disclosure. [Diagram 25] 25A and 25B show diagrams of a two-gap axial flux motor according to some embodiments of the present disclosure. [Figure 26] 26A-26F show an embodiment in which the core and magnets extend continuously over the rotor. [Figure 27] 27A and 27B illustrate a vernier machine stator that can be manufactured with angle segments according to some embodiments of the present disclosure. [Figure 28] 28A and 28B illustrate a compact winding method using a coil formed from a wide ribbon with specific notches in the end turn sandwich, according to some embodiments of the present disclosure. [Figure 29] FIG. 29 illustrates an automated toroidal winding machine according to some embodiments of the present disclosure. [Diagram 30] 30A, 30B, and 30C illustrate axial flux machines that may use windings formed in a printed circuit board (PCB) process, according to some embodiments of the disclosure. [Diagram 31] 31A and 31B illustrate an additive manufacturing method for an axial flux motor, according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] DETAILED DESCRIPTION OF EXEMPLARY NON-LIMITING EMBODIMENTS The present disclosure is directed to a motor technology that has substantially higher torque and power density compared to the state of the art known to the inventors. This technology can be used to replace current high performance motors with motors that utilize approximately half the expensive permanent magnet material and high performance magnetic steel. Thus, this technology can enable cost reduction. Furthermore, by using the disclosed technology with low cost magnetic steel and permanent magnets, motors that are still relatively high performance can be produced, but with a significant reduction in material costs. For example, replacing high performance neodymium iron boron (NdFeB) permanent magnets with much lower cost (and lower strength) ferrite magnets is a way to make a low cost yet still high performance motor.

[0008] Modern lightweight electric motors use concentrated windings, as shown in FIG. 1A. Concentrated windings have a coil span of 1, which results in an absolute minimum of wasted weight in the end turns. However, this approach does not have high torque density. FIG. 1B shows an example conventional vernier motor that uses magnetic gears to greatly increase torque density. The drawback is that a high magnetic gear ratio (called the pole ratio) requires a high coil span and therefore excess winding weight that is wasted in the end turns. The example in FIG. 1B shows an excess of 90 mm of end turn copper in the winding compared to the 70 mm active stack length where torque is produced.

[0009] Thus, the state of the art provides either motors that are light weight but have insufficient torque density (e.g., FIG. 1A), or motors that have high torque density but are too heavy (e.g., FIG. 1B). The state of the art, to the inventor's knowledge, does not provide an electric motor that is both sufficiently light weight and has high torque density.

[0010] FIG. 1C illustrates a stator for a lightweight, high torque density electric motor 100 using concentrated toroidal windings according to one embodiment of the disclosure. Electric motors including 100 use magnetic gears and include minimal end turns. In an exemplary embodiment of the disclosure, two vernier motors are placed back-to-back so that magnetic gears of any ratio, such as the motor of FIG. 1B, can be used with windings that have the same minimal waste as the concentrated winding end turn copper of the motor of FIG. 1A. This combination allows for the construction of electric motors that are both high in torque density and power density at the same time.

[0011] Faced with the need for a lightweight, torque-dense electric motor, the inventor first investigated magnetic gears (replacing mechanical gears) as a zero-wear means of reduction. However, magnetic gears themselves can fail, and also result in the need for additional bearing sets that increase the system weight. In the context of using magnetic gears in an electric motor, the inventor noted that the full output torque of the magnetic gears is produced by the magnetic field, the permanent magnets, and the electromagnetic steel components. The magnets and iron in the magnetic gears have weight, but do not produce power (i.e., they are passive). Thus, the inventor began to explore why the full output torque cannot be produced directly by the motor, and came up with an exemplary embodiment of a technique for achieving this (i.e., the full output torque is produced directly by the motor)! An example of the technique is shown in FIG. 2.

[0012] While researching the literature on magnetic gears, the inventor came across a class of machines called magnetic geared machines (MGM), including vernier machines that use magnetic gears in conjunction with rotor magnets, pole / slot combinations, and open slot configurations. Vernier motors were developed primarily for very high torque, very low speed applications such as wind turbine generators. Since efficient propellers generally rotate much slower than lightweight electric motors, vernier machines represented a good candidate for applications such as the direct drive aircraft propulsion applications the inventor is exploring. The challenge was to make it lightweight.

[0013] In proceeding to build a lightweight, high torque density motor according to the present disclosure, one of the first steps to achieve low weight at low mechanical speeds was to use a high pole count (i.e., many magnetic poles, e.g., greater than four) to increase the electrical speed of the machine. Next, Halbach magnetization was employed in the rotor to minimize the weight of the iron in the rotor core. Since high electrical speeds generally result in higher core losses, a very low loss magnetic steel was used in the core of the exemplary embodiment. Additionally, the magnets were split to minimize eddy currents in the magnets.

[0014] FIG. 1B shows a typical vernier motor, with large coil spans due to magnetic gears, resulting in excess copper in the end turns. One of the key insights that enabled the technology of the embodiments of the present disclosure was the realization that a Halbach "in-runner" vernier motor and an "out-runner" vernier motor could be placed back-to-back to form a dual-air-gap machine with a clocked stator, thus allowing the use of short toroidal windings. This approach virtually eliminates excess windings in the end turns, producing a very compact machine. It was found that cooling channels could be threaded through the center of the stator and rotor yoke without degrading the magnetic performance of the machine. All of this combined with a thermal conduction cooling sandwich around the end turns of the windings (usually the hottest part of the motor) produced very effective cooling. This mechanical / thermal design approach of the embodiments is referred to in this disclosure as a "cold sandwich" structure.

[0015] Dual air gaps have been used in ironless motors and conventional slotted motors (e.g., U.S. Pat. No. 6,924,574) and have been proposed in Niu et al., "Quantitative Comparison of Novel Vernier Permanent Magnet Machines," IEEE Transactions on Magnetics, Vol. 46, No. 6, pp. 2032-2035, 2010. However, these known techniques do not consider Vernier machines as provided in the embodiments of the present disclosure. Additionally, some embodiments utilize a combination of Halbach magnetization with a specific cooling method. Additionally, the techniques of the embodiments are equally applicable to radial and axial flux machines and combinations thereof. Additionally, the techniques are equally well suited to generator, linear motor, and actuator embodiments.

[0016] Potential applications of the motors of the exemplary embodiments include, but are not limited to, applications where weight and volume are important concerns. High on this list are electric aircraft propulsion motors for either horizontal and vertical flight of fixed wing aircraft such as helicopters and multicopters. Another type of application is one seeking to reduce or eliminate reduction gearboxes. The general motivation is to eliminate wear and maintenance items and reduce the volume and weight of the system. Mobile power generation, from truck-towed generators to stationary backup generators, can be significantly reduced in size and weight with the technology of the embodiments, allowing for easier transportation and installation of these devices. Similarly, generators on aircraft need to generate more and more power as the demand for larger electrical loads is seen across all applications. Airborne power generation greatly values ​​light, compact and efficient generators. Another reason for eliminating gearboxes with evolving technologies such as robotics is to enable back-driveable actuators, which can be more robust and enable new kinds of control algorithms and robotic performance. Electric motors driving fans and pumps that can benefit from more compact and lightweight motors are other potential applications.

[0017] Because the motor technology of the exemplary embodiment of the present disclosure has significantly higher torque and power densities compared to the state of the art, the technology can also replace current high-performance motors with motors that utilize significantly less expensive permanent magnets and high-performance magnetic steel. Thus, the technology can enable cost reduction. Similarly, by using the technology with low-cost magnetic steel and permanent magnets, motors that are still relatively high performance can be produced, but with significantly reduced material costs. For example, replacing high-performance neodymium iron boron (NdFcB) permanent magnets with low-cost (and low strength) ferrite magnets is an option for making low-cost but still high-capacity motors.

[0018] Aspects provide a new electric motor technology that produces very high torque at lower desired speeds while still being highly efficient and very compact. In aspects, this is accomplished by combining multiple technologies in a unique manner. In some aspects, the multiple technologies include a vernier electromagnetic system, high pole count, Halbach array rotor magnets, two or more back-to-back motor stators with proper clocking, cooling channels sandwiched between two or more stator yokes, cooling fins integrated into the rotor structure, high thermal conductivity stator winding end caps, windings made from ribbons composed of many smaller wire strands, integrated heat sink fins on the motor housing, drive electronics integrated into the same motor housing, and cooling channels integrated into the rotor core. In some aspects, one or more of the integrated heat sink fins on the motor housing, drive electronics integrated into the same motor housing, and cooling channels integrated into the rotor core may be optional to be included in the motor.

[0019] A vernier electromagnetic system is a type of magnetic geared machine (MGM). Vernier MGMs produce very high torque but typically have very large end turn sizes and masses (e.g., FIG. 1B). In an exemplary embodiment, the vernier MGM works for both radial and axial flux machines and linear motors, and can also be used for induction, interior permanent magnet (IPM), synchronous reluctance machines (SRM), and synchronous machines (SM).

[0020] The high pole count technology incorporated in the motors of the present disclosure may have four or more permanent magnet poles. High pole count increases the electrical speed of the machine while keeping the mechanical speed low.

[0021] Halbach array rotor magnets can be used in some embodiments to maximize the magnetic flux density toward the stator, allowing a thinner rotor yoke to carry the magnetic flux. Some embodiments may use magnet arrangements that are not Halbach arrays.

[0022] Two back-to-back motor stators with clocking as arranged in the exemplary embodiment allow for very compact windings with minimal (e.g., an absolute minimum) copper wasted on the end turns and places the rotor on the outside of the machine, which allows for very effective cooling of the rotor keeping magnet temperatures lower.

[0023] The cooling channels sandwiched between the two stator yokes allow a very short path for heat to flow out of the stator through the cooling channels. The cooling channels can be filled with thermally conducting solids (called cooling bars), heat pipes or liquid coolant. The cooling channels can be cavities in the stator and rotor laminations. The cooling channels can also be formed, for example, in an aluminum plate where the two stator cores are attached / bonded to the cooling plate. Effective cooling keeps the winding temperature lower, which improves efficiency and extends the useful life of the windings.

[0024] The cooling fins integrated into the rotor structure in the exemplary embodiment allow for direct cooling of the rotor core and magnets since the rotor structure is exposed to air, which improves performance since motor performance is limited by magnet temperature. The cooling fins integrated into the rotor structure also allow for the use of higher strength magnets which require lower operating temperatures.

[0025] Highly thermally conductive stator winding end caps in embodiments are positioned in contact with the winding end turns and can be specially constructed to provide a low resistance path for the winding end turn heat to flow to the cooling channels and housing, eliminating or minimizing eddy currents that can reduce efficiency.

[0026] Windings made from ribbons composed of many smaller wire strands also contribute some attributes in some aspects. The fine twisting reduces the winding AC resistance and reduces eddy currents induced in the strands themselves in the open slots. Square / rectangular cross-section wire can be used to form the ribbons, which allows for very high space factors and improves efficiency.

[0027] Integral heat sink fins on the motor housing provide, in some embodiments, a very compact cooling solution.

[0028] The drive electronics integrated into the same motor housing, in some aspects, uses the same cooling fins for a very compact system, which can also make motor installation and system design simpler, since it eliminates the need to find a place to mount the motor drive electronics.

[0029] Cooling channels may be integrated into the rotor core in some aspects. Such channels serve to cool the rotor magnets and can form an integral centrifugal coolant pump. They can also provide a mounting mechanism.

[0030] The above components, in various combinations, describe features that enable high torque density electric motors as provided in the embodiments of the present disclosure. Some of these features that are unique to this motor technology may further require new manufacturing processes and systems to produce the motors. These manufacturing processes and systems include, for example, toroidal winding machines with precise control of wire entry into the slots, integrated cutting and winding methods to fabricate axial flux machines with internal and external notches, laminated aluminum end cap rings with winding notches, compact routing of wire ribbons by joining and ribboning square / rectangular magnet wires and closely folding them, split stator assemblies, and modular stackability of axial flux motors to form larger motors.

[0031] Electromagnetic aspects of high torque density electric motors. Below are some electromagnetic aspects of the present technology that, in selected combinations used in the exemplary embodiments, result in high performance, high torque density and high power density motor / generators.

[0032] Figure 2 shows a cross section of a dual gap radial flux machine such as the embodiment of Figure 1C, illustrating an example arrangement of stator core 204, windings 206, rotor core 210, magnets 218, and cooling channels 214. Figure 2 also shows shaft seal 224 and oil bath bearing 226, integrated electronics 228, and heat sinks 220-222. These aspects are further described with respect to various embodiments below.

[0033] 3A and 3B show two main configurations in which motor technology according to embodiments can be constructed for either a radial flux machine (FIG. 3A) or an axial flux machine (FIG. 3B). FIGS. 3A-3B each show a cross-sectional view of only the top half of a motor according to some embodiments, similar to that shown in FIG. 2. The radial flux machine 300 of FIG. 3A includes a stator core 304 connected to a stator structure 302, a permanent magnet 318, and a rotor core 310 connected to a rotor structure 308, so that magnetic flux 320 is generated in a radial direction. The axial flux machine 330 of FIG. 3B includes a stator core 334 connected to a stator structure 332, a permanent magnet 348, and a rotor core 340 connected to a rotor structure 338, so that magnetic flux 350 is generated in an axial direction. The radial and axial machines of the embodiments each include two air gaps. The air gap is, in an exemplary embodiment, a mechanical gap between the rotor permanent magnets and the stator core. Each of Figures 3A and 3B shows the key components that make up the technology. The key features include multiple air gaps (316 in Figure 3A and 346 in Figure 3B), the windings (306 in Figure 3A and 336 in Figure 3B, which are toroidal wound), cooling channels embedded in the stator core (314 in Figure 3A and 344 in Figure 3B), and end-turn cooling features (312 in Figure 3A and 343 in Figure 3B). In addition, the stator (304 in Figure 3A and 344 in Figure 3B) and its cooling features are connected to the stator structure (302 in Figure 3A and 332 in Figure 3B). A feature of the technology is the very short thermal path from the cooling features (end-turn areas and channels) that transports heat generated in the windings and stator core to the stator structure and out to the heat sink. While there are multiple ways to mechanically arrange the rotor and stator structures for each of the radial and axial flux variations, two examples are shown in Figures 3A-3B.

[0034] FIG. 4 illustrates how axial flux rotor cores and magnets can be added to a radial flux structure to construct a three-gap machine 400, according to some embodiments. As illustrated, the stator structure 402, stator core 404, windings 406, rotor structure 408, rotor core, permanent magnets, cooling channels 414, and end-turn cooling features 412 are constructed similarly to those of the radial flux machine 300. For the three-gap machine 400, additional stator core material may be added (in the radial lamination direction). With the added axial rotor core(s) and permanent magnet(s), the machine 400 includes three air gaps 416, three rotor cores 410, and three permanent magnets 418. The machine provides radial flux 420 and axial flux 422.

[0035] Similar to machine 400, in another embodiment, a radial flux section can be added to an axial flux motor (either at the inner or outer diameter) to form a different type of three-gap machine.

[0036] In another embodiment, another axial flux rotor can be added (e.g., to the right of the arrangement shown in FIG. 4) to form a four or five air gap machine. However, this additional axial flux rotor must be split in half to allow the stator to connect to the stator structure. An exemplary five air gap configuration is shown in FIGS. 23A-B. Progressively more air gap configurations can be similarly constructed. If the number of air gaps is N, then N=3 is a three air gap machine, and N=4 and N=5 are four and five air gap machines, respectively. In the limit, N can be considered to go to infinity, and the different air gap components merge into one continuum.

[0037] FIG. 5A illustrates, in a schematic manner, certain electromagnetic aspects of a motor according to one embodiment, e.g., a 60 pole, 36 slot motor with a magnetic gear pole ratio of 5:1. An important aspect of this motor is that the system is effectively composed of two motors 502, 504 arranged back-to-back. A circular boundary 506 represents the boundary between the two motors. Outside the circle 506 is the "outrunner" type motor 502 (outrunner because the rotor 510 is outside the stator 508). And inside the circle 506 is the "inrunner" motor 504, with an inner rotor 514 inside the inner stator 512. The placement of the Halbach magnets 526 in each motor is shown. The illustrated example is a Vernier machine, defined as a motor with magnetic gears, and thus a pole ratio >1.

[0038] The slot filling pattern represents the phase of each winding, with shading 516 being phase A, shading 518 being phase B, and shading 520 being phase C. For each phase, there is a more densely patterned slot (e.g., slots 531, 534) marked with a "x" representing the winding entering the page that must be connected to another slot (e.g., slots 532, 533) of a more sparsely patterned slot marked with a "o" representing where the winding must exit the page. The outer connecting semicircle (e.g., 530 shown in dashed line) shows what the conventional windings would look like if this motor were conventionally wound. For the example shown, the pole ratio is 5 and the coil span is 3 slots. However, in the illustrated embodiment, the two stators 508, 512 are oriented such that the in and out directions of the same phase of each winding are clocked such that the option of winding it with a toroidal winding (and thus minimal extra end turn windings) is available. As an example, two examples of toroidal windings 528 are shown. One of the example toroidal windings 528 goes from the inner stator slot 532 of phase B 518 to the outer stator slot 531 of the same phase, and the other of the example toroidal windings 528 goes from the outer stator slot 533 of phase C 520 to the inner stator slot 534 of the same phase. It is this radial clocking of the two stators 508, 512 that primarily allows for very short end turn windings, regardless of the size of the coil span. This thus allows for the use of higher pole ratios (for higher magnetic gears) without a corresponding increase in winding end turn weight that would occur with conventional windings. An example of what it would look like if conventional windings were used is shown in the dashed lines 530 between each pair of slots of each of the three phases. It should be appreciated that the exemplary embodiment does not have physical windings such as winding 530, but instead has a toroidal winding 528 between each pair of corresponding clocked slots of motor 500.

[0039] FIG. 5B shows another example of a similar motor design 540, also with 36 slots, but the arrangement shown in FIG. 5B has 66 poles, resulting in a Vernier machine with a pole ratio of 11:1. This higher pole ratio requires a higher coil span of 6 slots, resulting in a much larger end turn mass if conventional windings were used. The larger coil span 542 is shown in dashed lines in the exemplary conventional winding. However, in the exemplary embodiment shown in FIG. 5B, the two stators (similar to motor 500) are clocked to allow them to be wound with short toroidal windings, greatly reducing the weight associated with the windings. As can be observed by comparing FIG. 5A and FIG. 5B, the length of the toroidal winding between the back-to-back stators in the two embodiments is the same, whereas it would have been significantly different if conventional windings were used. With respect to motor 540, it should be understood that, similar to motor 500, the exemplary embodiment does not have physical windings such as winding 542, but instead has a toroidal winding (similar to 528) between each pair of corresponding clocked slots of motor 540. The clocking angles shown in Figures 5A and 5B indicate the clocking angle that results in the lowest winding mass. It should be understood that the clocking angle between the two motors may be adjusted from this angle to address other design issues such as ripple torque and power factor, but at the expense of increased winding mass.

[0040] The open slot geometry used in the Vernier machine allows for toroidal windings as used in the exemplary embodiment with very high fill factors (fill factor is defined as the percentage of the cross-sectional area of ​​the slot that is copper). High fill factors are desired when building highly efficient motors and building lightweight motors. Toroidal windings reduce assembly costs and allow for the use of solid (i.e., unsplit) stator cores, which have better magnetic performance than split cores.

[0041] FIG. 6 details how a toroidal winding in an open slot (e.g., 602, 603) can utilize a flat ribbon of conductor (e.g., ribbons 604, 606) to achieve a very high fill factor. This example shows how the ribbon is formed from six square cross-section magnet wires (e.g., 608). Each 608 copper wire may be surrounded by insulation 610. The wire strands can be joined together to form a flat ribbon, e.g., one conductor width high and six conductor widths wide. This ribbon can be wound in a toroidal direction showing how the winding starts at the bottom of the slot and then wraps around itself to form a three-turn coil in this case. For example, ribbons 604, 606 are shown wrapping three turns in a toroidal direction between slot 602 of outer stator 614 and slot 603 of inner stator 612 (shown as being formed between two teeth 618 of stator yoke 616 of inner stator 612). The two ribbons 604, 606 are shown to illustrate that the slot 602 can be filled by winding multiple ribbons and then connecting them in series or parallel. Alternatively, a single ribbon can fill the slot width. Thus, the embodiments are not limited to any particular number of ribbons. Although a square cross-section magnet wire is shown, the embodiments are not limited to such square cross-section wires and rectangular and circular cross-section wires may be used. The example of FIG. 6 shows that the outer stator 614 and the inner stator 612 are separated by a cooling channel / plate 620, which may be made of aluminum, for example, and may support cooling channels therein. In some embodiments, the two stators 612, 614 may also be made of a single piece of magnetic steel with cooling / mounting channels formed therein. The arrow 622 indicates the direction of the windings.

[0042] The open slot geometry used in many vernier machines allows for flat ribbon based toroidal windings as described in connection with Figure 6, which produce very high fill factors. Conductors in the open slots are exposed to fringing flux from the permanent magnets. If the conductor is too large it can induce significant eddy currents which create braking torques that impair the efficiency of the machine. For this reason it is advantageous to fabricate the ribbon from many small strands to limit the eddy currents that are generated.

[0043] FIG. 7 shows a 3D model representation of a radial flux motor corresponding to the embodiment shown in FIG. 5B and FIG. 6. This figure also shows circular cooling channels in both the rotor yoke and the stator yoke. For example, the stator 708 is provided with cooling channels such as cooling channel 746, and the outer rotor 710 and the inner rotor 714 may be formed with cooling channels such as cooling channel 744. These cooling channels can serve both thermal and mechanical functions. For example, they can transport heat from the core and can also be used as a mechanical mounting mechanism. FIG. 7 also shows toroidal windings 728 between correspondingly located open slots on the stator 708 (or inner and outer stators arranged back-to-back) of the radial flux motor.

[0044] Figure 8 illustrates an axial flux variation of the motor embodiment shown in Figure 7. In Figure 8, the inner rotor 810 and outer rotor 814 may not have cooling channels therein, and the stator 808 may be configured with multiple cooling channels 846. It can be seen that the cooling channels 846 and the toroidal windings 828 are oriented differently than the motor embodiment shown in Figure 7.

[0045] 9-11 illustrate several different ways in which the vernier electromagnetic system can be mechanically arranged with different cooling solutions, according to several embodiments.

[0046] FIG. 9 shows how a dual gap axial flux machine can be combined with an outer radial flux machine to form a triple gap machine. The illustrated example uses heat pipes 904 embedded in a stator core 906 (windings are illustrated on the stator core), with cooling bars (also called heat pipes) serving a dual purpose: to transport heat from the core to the stator structure 902 (shown to include cooling fins) and as structural elements to mechanically attach the stator core 906 to the stator structure 902. A rotor housing 910 made of a lightweight, thermally conductive material such as, but not limited to, aluminum has integral cooling fins 912. In the illustrated embodiment, these fins are shaped to force cooling air over the rotor structure to form a centrifugal fan that cools the magnets as well as the rotor core. Additional fan blades, which double as rotor spokes, are also integrated into the rotor core. These blades form an axial fan that blows air across the stator structure to cool the stator. Shown are integrated rotor structure and cooling fins (aluminum) 910, three sided magnets and rotor core 908, stator core and windings 906, cooling bars 904, and stator structure and cooling fins (aluminum) 902.

[0047] FIG. 10 illustrates a similar approach in which a dual air gap radial flux machine is augmented with a single axial flux component to form a three air gap machine. The three air gap machine includes three rotor cores 1016, 1018, 1020 and three rotor magnet arrays 1017, 1019, 1021 as shown. The lamination directions of the radial and axial flux machines are different to prevent eddy currents in each region of the stator core. For example, rotor cores 1016, 1018 and magnet arrays 1017, 1019 that are part of the radial flux machine have an axial lamination direction, and rotor core 1020 and magnet array 1021 that are part of the axial flux machine have a radial lamination direction. Stator core 1024 is part of the radial flux machine and additional stator core 1025 is part of the axial flux machine. The exemplary stator core structure 1010 includes stator cores 1024, 1025, 1027 and toroidal windings 1026 between axial slots in the stator core. Stator cooling bars 1012 can be either solid material, hollow coolant tubes, or heat pipes and are integrated into the stator core. The rotor also has cooling fan blades 1028 integrated into the rotor housing 1004, but in this case they are all axial fan blades. The stator housing / structure 1014 serves as a mechanical mounting for the stator core 1010 (stator cores 1024, 1025) as well as the windings 1026, and has multiple cooling fins 1030 integrated into the stator housing / structure to facilitate dissipation of stator heat conducted to the stator housing / structure through the cooling bars 1012 and to direct conductive paths from the mounting mechanism. A shaft bearing assembly 1002 for the rotor housing 1004 and a magnet retaining band 1006 are also shown. As illustrated, the winding 1026 is toroidal.

[0048] FIG. 11 is an exploded view of a dual air gap axial flux machine according to some embodiments. The exemplary axial flux dual air gap machine includes integrated power electronics and cooling features. It shows a stator "cold sandwich" part 1108 that is an integrated part featuring cooling bars / channels and features in the end turn areas to efficiently transfer heat from the end turns and stator core to a stator heat sink 1110. This example shows a corrugated stator fin heat sink highly integrated into the outer stator structure to cool the motor. This example also features a portion 1102 that includes integrated drive electronics 1114 (e.g., power semiconductors, processor, and sensors) and its own corrugated heat sink (shown at the periphery of the structure) to dissipate heat generated within the drive electronics. This example of the technology shows a rotor housing 1112 that encases the stator and has integrated axial fan blades 1116, similar to the compressor blades of a turbine engine. These fan blades 1016 blow air onto a heat sink (e.g., stator heat sink 1110) as the motor rotates. The stator core is made up of the stator electromagnetics (including the toroidal windings) 1106, the stator cold sandwich 1108, and the stator heat sink 1110. The stator frame (including the bearing seats) 1104 is also shown. A cross-sectional detail of this design is shown in Figure 2, and a more complete portion of the motor is shown in Figure 12A.

[0049] Figures 12A and 12B show unexploded views of the motor shown in Figure 11. Figure 12A shows rotor housings 1204, 1206 (rotor housing 1112 in Figure 11) with axial fan blades 1116 built in. The end view in Figure 12B more clearly shows how the technology can integrate axial fan blades into the rotor housing to force air over corrugated heat sink fins 1208 (shown as component 1110 in Figure 11). Figure 12A also shows electronics heat sink 1202 (shown as component 1102 in Figure 11).

[0050] The high torque density electric motor technology of the disclosed embodiments utilizes an end turn sandwich construction, the assembly of which is shown in detail in Figures 13A-13D for an axial flux machine. In this case, the stator is formed by two stator core halves 1302, 1303 (see Figure 13A), each made of high performance magnetic steel, joined into a high thermal conductivity sandwich piece consisting of 1304, 1306, 1308, and 1310. The sandwich piece includes cooling channels 1304 and is made of a high thermal conductivity material (e.g., aluminum) for winding end turns in the respective slots 1306, 1310. The stator ready for winding is shown in Figure 13B. The two stator core halves 1302, 1303, sandwich piece 1308 after joining of the two stator core halves are shown in Figure 13B. The stator is then wound with a toroidal coil 1312 in these slots 1306 between the sandwich end turns (e.g., end turn 1310). FIG. 13C shows the wound stator. Finally, an outer coolant manifold 1316 and a heat sink 1314 are installed. FIG. 13D shows the wound stator with the heat sink 1314 and coolant manifolds 1316, 1318 installed. The windings generate the largest percentage of the motor's waste heat and this structure provides a very short thermal path for the winding heat to reach the heat sink. It should be understood that FIG. 13 is one example of a liquid cooled machine and other embodiments using cooling bars or heat pipes or plates are also contemplated.

[0051] FIG. 14 is a cross-sectional view of an axial flux stator (e.g., in an axial flux machine corresponding to FIGS. 13A-D) split in half and showing a cross-section of a variation with liquid coolant channels. This diagram 1400 shows in dashed lines the coolant flow 1412 as it snakes through the coolant channel 1410 of one stator tooth 1420 and across the open slot 1406 to the next tooth 1421. The open slots of the stator (e.g., 1406, 1408) contain toroidal windings. Thin arrows 1414 show how heat generated as core losses flow into the coolant 1412, and heat generated in the windings (shown as thick arrows 1416, 1418). FIG. 14 shows how short the path is from the heat source (e.g., the core 1402 and the windings in the slots 1406, 1408) to the heat sink 1404. There are multiple ways to arrange the electromagnetics (radial flux, axial flux) as well as multiple ways to arrange the coolant channels and heat sinks for each type of machine. FIG. 14 shows a coolant channel 1410 that flows through the end turn sandwich area 1420, then through the stator core 1402 to the other end turn sandwich 1421, then out to the outer housing 1422. Alternatively, the coolant channel can snake just inside the stator core and not cross the end turn sandwich area, as shown in FIG. 25B. FIG. 14 shows integral heat sink fins 1404, but if liquid cooling is used, the coolant can go to a separate heat sink / radiator. The channel can also include only cooling bars without liquid cooling.

[0052] FIG. 15 shows a thermal finite element analysis (FEA) simulation of a simplified model of a radial flux dual gap machine according to one embodiment, where a heat pipe 1508 is considered to transport heat from the left end portion of the end turn sandwich area 1504, through the stator core 1510, and then through the other side of the end turn sandwich area 1505 to the heat sink 1506. With an efficient heat sink, the sandwich structure was observed to significantly reduce the winding temperature. The dark to light grey scale shows the temperature distribution from hot to cold. The heat sink 1506 is shown with a lighter shading representing that it is cooler, and the FEA shows that there is little temperature rise from the heat sink to the windings, so the windings remain cool.

[0053] One key challenge is to select the best material for the end turn sandwich pieces. The sandwich material needs to be highly thermally conductive, but is immediately adjacent to the windings that carry large time-varying currents. Thus, any conductive material that is in close proximity or passes through the coil will have eddy currents induced in it. Figures 16A-16B show electromagnetic FEA simulation-based analysis of two different approaches to forming the sandwich structure. The sandwich structure shown in Figure 16A used a solid aluminum piece with a segment that passes through the coil. The area close to the coil and the area under the coil will have large eddy currents induced in it that are so large that they do more harm than good. The sandwich structure shown in Figure 16B shows the eddy currents induced in a split sandwich structure, where an insulating material is used under the coil and the solid aluminum conducts the heat to the cooling channels.

[0054] The preferred material for the end turn sandwich is aluminum nitride (AlN), a non-conductive ceramic with thermal conductivity close to that of aluminum. Another alternative is to use laminated thin aluminum strips / sheets that are bonded together (see Figures 17A-17B) and machined to form the sandwich. This is the same reason that electric motor cores are made from laminations of thin magnetic steel that are electrically insulated from one another. Anodized aluminum is one way to create an electrically insulating surface that can then be bonded to other anodized aluminum sheets or wrapped on a mandrel to form a cylinder or ring. The radial layers of the laminations shown in Figure 17B (e.g., 1706, 1708, 1710 with electrical insulation between each layer) exemplify the configuration of the wound anodized aluminum coil 1702 shown in Figure 17A. The surface of the coil metal can be electrically insulated (e.g., thin insulating strips 1704) to block eddy currents.

[0055] 18A-18C show one example of how an end-turn sandwich structure for an axial flux dual gap machine can be formed utilizing bent rectangular heat pipes to carry heat from the core, windings, and end-turns to the stator housing and its integral heat sink fins. FIG. 18A shows a low temperature sandwich stator 1802 and heat pipes (e.g., 1804). FIG. 18B shows the stator 1802 mounted in a stator housing 1806 that contains a heat sink 1808. FIG. 18C shows a rotor housing 1810 with integral centrifugal fan blades 1812 that expel cooling air radially to cool the rotor. Ducts can be used to rotate and expel the air axially over the stator cooling fins 1808.

[0056] Figures 19A and 19B show how axial flux machines can be stacked axially to form a larger motor. Figure 19A shows three motors 1904, 1906, 1908 stacked to form a larger motor (stacked motor / machine) 1902. This example shows in the cross section of the machine 1902 shown in Figure 19B how rotor cooling blades (e.g., 1912) can pull air from the center of the machine onto the inner segments of the motor to maintain uniform cooling of the stacked machine 1902.

[0057] 20A-20E illustrate aspects of a dual air gap radial flux embodiment, such as the embodiment shown in FIG. 3A. FIG. 20A illustrates an example of an assembled motor. FIG. 20B illustrates the stator with one of the coils that make up the winding 2006 hidden to more clearly show the slots 2002. In the illustrated embodiment, the coolant channel 2004 may include a metal tube to mechanically connect the stator core 2008 to the outer frame / housing 2010. FIG. 20C illustrates a side view of the stator of FIG. 20B, and FIG. 20D illustrates a front view of it, including the rotor core and magnets. FIG. 20E illustrates the rotor with magnet arrays 2012, 2014 attached.

[0058] FIG. 21A illustrates a rotor with a Halbach array of magnets implemented. The Halbach array is shown more clearly in FIG. 21B. Note that the example Halbach array is constructed from a four-piece magnet segment with each magnet being a 90 degree change in flux direction, but is not limited thereto. For example, an eight-piece magnet Halbach array (e.g., 45 degree change in direction between magnets), among other approaches, can be used. In some aspects, instead of the standard magnet array of the rotor shown in FIG. 20E (i.e., non-Halbach), the Halbach array implementation of the magnets of the rotor can be configured as shown in FIG. 21A.

[0059] FIG. 22 illustrates a split tooth vernier stator in the form of a radial flux outrunner, according to one embodiment. One of the coils 2206 is hidden to more clearly illustrate the semi-closed slot 2204 formed between a pair of "shoe teeth" 2202. While the embodiment of the split tooth vernier machine has a semi-closed slot, many of the embodiments shown in the other figures feature an open slot vernier machine. Semi-closed slots can be wound with conventional manufacturing methods, but are more difficult to wind with toroidal windings compared to open slots. The open slot configuration of the stator teeth and split tooth nodes act as the flux modulators required for the magnetic gear effect in the vernier machine.

[0060] 23A and 23B show diagrams of a five air gap axial flux motor according to some embodiments. Rotor core / magnet assemblies 2302, 2304 represent two axial flux directions, rotor core / magnet assembly 2306 represents a radial flux direction, and smaller rotor / magnet assemblies 2308, 2310 represent an additional two radial flux directions to provide a five air gap motor.

[0061] 24A and 24B show diagrams of a three-gap axial flux motor according to some embodiments. Rotor core / magnet assemblies 2402, 2404 represent two axial flux directions and rotor core / magnet assembly 2406 represents a radial flux direction to provide a three-gap motor.

[0062] 25A and 25B show diagrams of a two-gap axial flux motor, according to some embodiments. The rotor core / magnet assemblies 2502, 2504 present two axial flux directions to provide a two-gap motor.

[0063] 26A-26F show an embodiment where the core and magnets extend continuously on the rotor instead of segments (e.g., instead of segments such as 2402-2406). Mathematically, this can be expressed as a representation of the motor when the number of air gaps, N, goes to infinity, the space of the air gaps goes to zero, and it becomes a continuum of air gaps. In FIG. 26A, the rotor magnets 2602 are visible and the representation of the stator is omitted. FIG. 26D hides the rotor magnets so that the coils 2608 and stator core 2606 are visible. FIG. 26B, FIG. 26C, FIG. 26E, and FIG. 26F show a cross section of the motor. Note that if the representation of FIG. 26C were stretched to form a cylinder similar to a hydraulic cylinder, for example, it would represent a linear actuator / motor.

[0064] Manufacturing high torque density electric motors 27A through 31B illustrate aspects of a unique manufacturing technique for making multiple gap magnetic geared machines.

[0065] 27A and 27B show magnetic flux lines from FEA simulations of two vernier motors with the same number of stator slots (e.g., as in FIG. 15) but different magnetic gear ratios (pole ratios). The superimposed triangles 2702, 2704 show the smallest atomic segment. The motor is an integer multiple of this unique segment (i.e., the magnetic flux pattern repeats). FIG. 27A shows a motor with a 5:1 pole ratio formed from 12 repeating segments. FIG. 27B shows a motor with an 11:1 gear ratio formed from 6 repeating segments. When manufacturing a stator, segments that can be any integer multiple of the atomic segments can be manufactured and then assembled into the final stator. While manufacturing 12 segments would likely be uneconomical, both of these machines could be split in other ways, e.g., in halves or thirds. Having open segments changes the topology of the toroidal winding to a simpler topology, making it easier to wind the stator segments and reducing winding costs. However, the segments must then be assembled, which adds some assembly cost and reduces magnetic performance.

[0066] Figures 28A-28B illustrate a method for deterministic and compact winding on a multi-gap vernier machine when using flat wide conductor ribbons (e.g., ribbons 2802, 2804) with careful cutouts (e.g., as shown at 2806, 2808) in the end turn sandwich (e.g., 2810, 2812). Figure 28A illustrates the folded ribbon winding exit (from the winding) and Figure 28B shows the folded ribbon winding entry (to the winding). Careful design of the folds and cavities allows maximum area contact of the winding to the sandwich while minimizing excess end turn volume.

[0067] FIG. 29 shows an example of a toroidal winding machine 2900 that can wind the multiple gap vernier machine of some embodiments. The challenge with this technique is that to form the toroidal winding, the winding wire / ribbon must be wound on sub-spools that are small enough to pass inside the core. For the most compact winding, all phases must be wound consecutively, winding all adjacent slots of one phase, then switching to the next phase, winding all adjacent slots of that phase, switching again until the first group of slots of all phases are wound, then the first phase passes over or around the slot that was just wound, and the process is repeated. FIG. 28A shows the winding exiting the slot and the end turns 2806 crossing two slots occupied by the other phase and then re-entering another slot. This matches the winding pattern of the 36 slot, 60 pole, 5:1 pole ratio motor shown on the left of FIG. 27A and detailed in FIG. 5A. Since the inter-slot wire must cross other slots, the winding process must proceed with alternating phases per slot to create the most compact and balanced winding, but other methods are possible. FIG. 29 shows a three-phase winding, so three sub-spools (sub-spool phase A 2902, sub-spool phase B 2904, and sub-spool phase C 2906) are used for the winding. This method involves an actuation ring 2908 that grips and rotates one sub-spool to form a toroidal wound coil in its slot. The actuation ring can open to unlock the interlock of the two toroids. The actuator 2908, or another robotic arm (e.g., positioner 2910), for example, can then move the sub-spool to a resting position and then grip the next sub-spool. The positioner 2910 can be a general robotic arm, or a more dedicated actuator made specifically for this winding operation. If the stator core is a segment rather than a complete toroidal core, the winding process may utilize only a positioner to manage the spool exchange and loading / unloading operations.

[0068] The inter-slot windings shown in Figures 28A and 28B show ribbons crossing the tops of the slots. It is possible to pass the inter-slot ribbons under the winding end turns. The end turn length would have to be increased to accommodate this, which may not be worthwhile for wide ribbons, but it is possible. If multiple ribbons are used, this extra length of end turns can be reduced somewhat. Additionally, it is possible to wind each phase separately if the inter-slot ribbon passes under the end turn of the next slot. Since each phase will have a different inter-slot pattern, there is some challenge in ensuring the windings have exactly the same length and are balanced. However, this eliminates the need for a lay-up sub-spool after each slot is completed.

[0069] An alternative to the toroidal winding approach shown in FIG. 30 is to form the coils and winding end turns in a printed circuit board (PCB) process. The PCB process limits the space factor that can be achieved compared to the wide ribbon process shown in FIG. 6, but may be well suited for smaller motors where it is more difficult to make sub-spools small enough to fit through the inner diameter of the stator core (such as would be required if machine 2900 were used). FIG. 30A shows how flat PCB stator windings 3002, 3003 can be integrated into a dual air gap axial flux vernier machine. Note that there are two winding PCBs per air gap. The PCB stator works equally well for single air gap axial flux machines, either vernier or standard. FIGS. 30B and 30C show the coolant ports 3004, 3006 and corresponding coolant channels 3008. The challenge with vernier motors is that the electromagnetic gears require open slots, and thus the windings require finely insulated strands of wire to form the windings in a way that minimizes eddy current losses in the conductors. Etching limitations of the PCB process limit how narrow the gaps between the conductors can be. Thus, the PCB winding process has a lower space factor and can be less efficient or heavier than ribbon winding methods. However, for slower speed applications, where eddy current losses are less significant, this is less of an issue.

[0070] Figures 31A and 31B show the winding of a tape of thin core material (e.g., magnetic steel) on a mandrel to form a toroidal core. The most basic version is a simple flat tape wound to form a cylindrical core (a toroid with a rectangular cross section). The concentric laminations of the core can be joined into a rigid core in a manner similar to conventional stacked laminations, where the layers can be adhesively bonded and interlocking snap features or welding can be used. If the core is solid enough, features can be machined into it. However, Figure 31A shows that features (e.g., 3102, 3104), both external and internal, can be cut into the tape (e.g., 3106) before or during winding and then wound onto the core with complete features. This is the winding equivalent of the common stacking method used for radial flux machines, where slot features and cooling cavities are laser cut, etched or punched into the individual laminations before assembly of the stack. The method shown can have features cut by laser cutter, stamp or etched by photolithography. The spacing between the slot and cavity features needs to be closely controlled and continuously varied throughout the process, since these features tend to move further apart as the radius of the winding increases.

[0071] FIG. 31B shows how a completely internal channel, such as channel 3008 shown in FIG. 30C, can be formed with this process that allows for something like a serpentine coolant path that passes through the entire core but has only two small ports (e.g., ports 3004, 3006 shown in FIG. 30B). Interlocking snaps can be driven in as precision clocking features to maintain correct feature alignment during the winding process. Snaps can also hold stacked layers in precision alignment, for example, until a later resin infusion step. This manufacturing method can be used with any thin strip or sheet material, such as aluminum or carbon fiber. This method can be used to form an aluminum end-turn sandwich for radial flux machines with notches for the end turns, as an example.

[0072] In an exemplary embodiment, the problem of efficient electric motors being too large and heavy is solved by a multiple gap magnetic geared machine with compact toroidal windings that utilizes a thermally conductive structural spine / sandwich component to mechanically hold the stator and extract waste heat.

[0073] In the motor, TIFF2025515137000002.tif4128, wherein TIFF2025515137000003.tif3128 is the number of rotor pole pairs, TIFF2025515137000004.tif3128 is the number of stator pole pairs, TIFF2025515137000005.tif3128 is the number of flux modulators. Define it as TIFF2025515137000006.tif7128. Non-magnetic geared motors (most standard motors) have a pole ratio of 1, while magnetic geared motors have a pole ratio greater than 1.

[0074] In an embodiment, the multiple gap magnetic geared machine includes a vernier motor. In the open slot configuration of the exemplary embodiment, the number of flux modulators is the same as the number of stator slots / teeth.

[0075] The stator core of the motor of the embodiment can be formed from electrical insulating layers / laminations or particles. Thin magnetic steel laminations are used to minimize stator core losses. For laminations, the lamination direction is the cross product of the air gap surface and the direction of motion (i.e., perpendicular to both). The stator has a yoke (annular portion) and teeth made of steel material (e.g., relative permeability much greater than 1). In some embodiments, a heat conducting frame is held to the back of the stator to provide mechanical structure and to draw heat away from the stator.

[0076] The rotor of the motor in the exemplary embodiment may be constructed of solid steel for cost savings or may be made from insulating laminations or particles. Thin magnetic steel laminations may be used to minimize the rotor core. In some embodiments, the rotor may be a surface permanent magnet (SPM) rotor with magnets bonded to the rotor ring structure (e.g., to the rotor yoke). The rotor has a yoke (annulus) of steel material. In some embodiments, the rotor may have magnets embedded inside the core (e.g., interior permanent magnet (IPM)). The rotor magnets may be "skewed" to reduce torque ripple. The rotor magnets may be split tangentially and axially with a layer of electrical insulation between them to reduce eddy current losses. A thermally conductive frame is held to the back of the rotor to provide mechanical structure and to draw heat away from the rotor.

[0077] In some embodiments, the use of Halbach magnetization for magnets in the rotor provides a multi-gap magnetic geared machine with very small size and very light weight. The use of surface permanent magnets in a Halbach array has been found to provide the most torque at the least weight among several options for rotor magnetization in embodiments.

[0078] However, embodiments are not limited to using Halbach magnetization in the rotor(s). The magnetic gears in embodiments can operate with many other types of rotor magnetization including, for example, standard magnet arrangements (e.g., alternating N, S magnets), consequent pole (e.g., small steel teeth around the magnets), and interior permanent magnets (IPM). Alternatively, in some embodiments, the rotor(s) may have no magnets at all, following a synchronous reluctance motor (SRM) design.

[0079] The windings are formed from connected coils, which are made from wound strands of wire or "preformed" rectangular copper bars. Concentrated windings have the fewest "end turns" which reduces weight. Formed windings have the highest "fill factor" which minimizes ohmic losses.

[0080] The embodiments use toroidal windings. The embodiment technology provides a stator core formed of a torus with teeth (and therefore slots). The winding wire fits within the slots as opposed to being evenly distributed around the torus as in the case of a toroidal transformer. A bundle or ribbon of twisted wire may be used to mitigate skin effect losses. The position of the wire strands may be controlled to mitigate proximity effect losses (e.g., with Litz wire, controlling the position within the slots, ribbons and ribbon sub-segments twisted between slots). In some embodiments, the windings may be split for redundancy. The windings may be split to provide different series / parallel combinations for induced voltage / impedance control. The windings and / or end turns may be formed from PCBs for axial and radial flux machines, respectively. In some embodiments, a combination of etched copper foil laminates may be stacked or wound to form flat or circular windings or circuits.

[0081] Embodiments arrange the stator and rotor in a multi-gap topology (e.g., with substantially more than 50% of the circumference of the stator cross section having magnetic flux across the air gaps) by placing multiple (e.g., 2-5) motor sections "back-to-back." The slots associated with each air gap can be rotated or shifted relative to each other (i.e., clocked) to trade off winding size and magnetic efficiency. Clocking can be used to cancel or minimize torque ripple that occurs at each air gap. A thermally conductive, structurally strong frame is placed in the "center" of the core to mechanically support the core and to carry heat away. The frame may be hollow and carry cooling fluid. In some embodiments, the stator slots can be "skewed" to reduce torque ripple.

[0082] The term "skew" may be used to describe any twist about the axis of rotation of the mechanism, either the stator core, rotor core, or magnets. Such twist may be engineered to control torque ripple.

[0083] The term "clocking" may be used to describe the relative angle between two components that share the same axis of rotation. This may also be called alignment or registration. While clocking generally refers to continuous angular alignment, the term "indexing" may be used to indicate discrete integer number of angular options.

[0084] The magnetic material (core and magnets) in the embodiments can be constructed in any of several ways. For example, the magnetic material may be constructed from laminated sheets by using thin laminations or segments with electrically insulating layers between the laminations. In another example, the magnetic material may be constructed from particles by using particles with electrically insulating films / layers between the particles. The particles can be sintered to a solid (e.g., ferrite) or bonded with an epoxy matrix (e.g., bonded magnets).

[0085] Eddy currents are another challenge in motor construction. Motors are built with ferromagnetic cores, copper windings, and some motors contain permanent magnets, all of which are conductive. Eddy currents are induced in conductive materials when exposed to time-varying magnetic fields and can be a significant source of power loss or wasted energy in motors. To mitigate these sources of loss, aspects can be configured to block eddy currents from flowing in each component.

[0086] In some aspects, as a general description, an approach to reducing eddy currents in a conductive part is to divide the part into several smaller parts with an electrically insulating layer between them.

[0087] For example, for ferromagnetic cores (e.g., stators and rotors), one way to mitigate eddy currents in embodiments is to use a stack of thin laminations of "magnetic steel," where each lamination has a thin electrically insulating coating to prevent current from flowing in the stack direction (lamination to lamination). Magnetic steel is an alloy of iron with high magnetic permeability and higher electrical resistivity. Another method is sintered powder metal, where the ferromagnetic particles have an electrically insulating film. This provides the lowest losses and allows magnetic flux to travel in both the axial and radial directions.

[0088] A winding consists of a set of coils connected in appropriate series and parallel connections. The coils are formed from one or many strands of "magnet wire", each with a thin, electrically resistive coating to restrict the current to flow only along the length of the wire. The strands are also often selected to mitigate the "skin effect", resulting in the lowest AC electrical resistance (thus minimizing ohmic losses). Some embodiments further improve winding resistance by using rectangular or square magnet wire and closely controlling the placement of each strand. This maximizes the "space factor" (fill factor), which is the ratio of copper cross-section to the available cross-section of the coil "slot". In some embodiments, the wire strands can be twisted in a particular way, often referred to as "Litz" wire (e.g., Litz wire or ribbon in type 7 / 8 construction), to mitigate the so-called "proximity effect", where different strands in the same bundle (or electrical node) have different induced voltages due to their relative position in the slot. Litz twist or other controlled strand placement methods can be used to ensure that each strand uses approximately the same amount of length in all potential slot positions, thus evening out this inter-strand voltage difference.

[0089] With regard to permanent magnets (PMs), in an exemplary embodiment, the PMs can be split both tangentially and axially / stack-wise with electrical insulation (which can be insulating material or simply space) between the magnet segments to reduce eddy currents. This is referred to as "magnet splitting."

[0090] The problem of efficient electric motors being too large and heavy is solved in embodiments of the present disclosure by maximizing magnetic flux linkage using substantially small stator and rotor masses. In an exemplary embodiment, the task of delivering electromagnetic torque to a moving / rotating output is addressed by creating a moving (e.g., time-varying) magnetic field with an electromagnet that interacts with a magnetic field created by a permanent magnet. The task of maximizing magnetic flux linkage, and therefore torque, is addressed by using magnetic gears. A vernier is one type of magnetic gear machine used in an exemplary embodiment.

[0091] Vernier magnetic gears require a coil span larger than one, an open slot configuration in the stator, allowing time-varying flux to cross the permanent magnets, and have the vernier flux carried in a ferromagnetic (e.g., silicon, cobalt steel, or other) rotor core. However, these aspects of the vernier present the following challenges: the large coil span results in a large end-turn mass with standard winding techniques; the open slot configuration causes side effects due to the proximity effect (e.g., non-uniform voltage and current distribution across the slots); the time-varying flux crossing the permanent magnets causes magnet eddy current losses; and the vernier flux carried by the rotor core causes rotor core losses.

[0092] In aspects, the challenge of large end-turn winding mass is addressed by placing two or more stators back-to-back, clocking them against each other, and forming a toroidal coil (gram winding) to form a compact winding with minimal end-turn copper. In some aspects, the challenge of proximity effect losses is addressed by techniques such as using ribbons of stranded wire, controlling the twist between the stator slots, and / or Litz wire braids / ribbons. In some aspects, the challenge of reacting torque and removing heat from the stators is addressed by structural thermally conductive spines placed between the stators and connecting them to the frame. In some aspects, the challenge of ohmic losses (e.g., heat) in the windings is addressed by forming ribbons from rectangular / square wire to minimize winding resistance in the finite slot area. In some aspects, the challenge of minimizing rotor mass is addressed by using permanent magnet Halbach arrays that generate more magnetic flux for the same mass and reduce the thickness of the rotor core. In some aspects, the rotor thermal issue is addressed by conducting heat generated in the magnets and core to a rotor frame that takes the heat away, and the frame may also deliver electromagnetic torque to a load output. In some aspects, the magnet eddy current loss issue is addressed by dividing the magnets with a thin electrically insulating barrier.

[0093] Aspects of this technology allow the option of eliminating the gearbox in many applications. Eliminating or minimizing the gearbox helps reduce weight and eliminate or reduce lubrication systems such as pumps, filters, piping, etc.

[0094] The aspects discussed thus far have referred to the invention as a motor. However, the motor can also be used as a generator or alternator. When mechanical shaft power is used to rotate the rotor, a voltage is induced in the windings that powers a load. Thus, the motor is equally well suited for generator as well as motor applications.

[0095] In one aspect, the present disclosure provides a magnetic geared apparatus configured as either an electric motor or generator, the apparatus including a stator structure and a rotor structure arranged to improve torque generation, the stator structure including N≧1 stator cores and shared toroidal electrical windings, and the rotor structure including an equal number of corresponding rotor cores.

[0096] The apparatus of the above paragraph, wherein the apparatus is a Vernier machine. The N stator cores of the Vernier machine are arranged back-to-back. The N stator cores may be integrated into a single physical core.

[0097] The apparatus of any one or more of the two paragraphs above, wherein a respective cold sheet (e.g., a "cold plate" (i.e., a planar cooling structure) for an axial flux machine or a "cold cylinder" for a radial flux machine) and one or more cooling channels are disposed between each pair of stator cores. Each cold sheet may incorporate one or more cooling channels.

[0098] The apparatus described in any one or more of the three paragraphs above may include any one or combination of the following: one or more thermal channels configured to transport heat from the stator structure; a housing structure and a plurality of mechanical supports configured to connect the N stator cores to the housing structure; a plurality of magnets arranged in a Halbach configuration and attached to at least one rotor core; the N stator cores and / or the N rotor cores configured to reduce eddy currents; electrically insulated ferromagnetic laminations arranged in a lamination direction perpendicular to the air gap surface and perpendicular to the direction of motion of the rotor relative to the stator, thereby limiting eddy currents in the stator core and rotor core; the N rotor cores and / or the N stator cores formed of ferromagnetic particles that are electrically insulated from each other, thereby limiting eddy currents in the rotor core and / or the stator core; the N stator cores including stator core teeth arranged in a substantially open slot configuration for magnetic flux modulation.

[0099] The apparatus described in any one or more of the four paragraphs above may have N stator cores substantially fused within a stator structure and / or N rotor cores may be substantially fused within said rotor structure, whereby the toroidal winding is substantially encompassed by the substantially fused stator and / or the substantially fused rotor.

[0100] The apparatus of any one or more of the five paragraphs above, comprising a housing structure and a plurality of mechanical supports configured to connect the N stator cores to the housing structure. The plurality of mechanical supports may be further configured to transport heat from the stator structure.

[0101] The toroidal winding in the apparatus of any one or more of the six paragraphs above may include a flat ribbon made of multiple strands of wire and disposed within the stator core slots. The ribbon may be made of Litz wire construction or the strands of wire may have a rectangular cross section, thereby minimizing ohmic losses. The position of each of the strands of wire within the ribbon may be varied with respect to the respective stator core slot to minimize proximity effects and thereby minimize ohmic losses.

[0102] The apparatus according to any one or more of the seven paragraphs above may have stator and rotor structures arranged to maximize axial and / or radial magnetic flux.

[0103] The apparatus described in the above paragraph, wherein (1) N=2 and N stator cores and N rotor cores are arranged to form a dual air-gap radial flux machine, (2) N=2 and N stator cores and N rotor cores are arranged to form a dual air-gap axial flux machine, (3) N=3 and N stator cores and N rotor cores are arranged to form a three-air-gap flux machine including either two axial air gaps and one radial air gap, or one axial air gap and two radial air gaps, (4) N=4 and N stator cores and N rotor cores are arranged to form a five-air-gap flux machine including either two axial air gaps and three radial air gaps, or three axial air gaps and two radial air gaps, or (5) N stator cores and N rotor cores are arranged to form a multiple air-gap machine in which the air gaps are adjacent, and the multiple air-gap flux machine may be configured as a linear machine.

[0104] All patents, patent applications and publications cited herein are hereby incorporated by reference for all purposes as if expressly stated.

[0105] While the present invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. 1. A magnetic geared machine configured as either an electric motor or generator and including a stator structure and a rotor structure arranged to improve torque generation, the stator structure includes N≧1 stator cores and a shared toroidal electrical winding; and the rotor structure including an equal number of corresponding rotor cores; A magnetic geared device.

2. 2. The magnetic geared device of claim 1, wherein said device is a vernier machine.

3. The magnetic geared device according to claim 2 , wherein the N stator cores are arranged back-to-back.

4. 4. The magnetic geared apparatus of claim 3, wherein a respective cold sheet and one or more cooling channels are disposed between each pair of back-to-back stator cores.

5. The magnetic geared apparatus of claim 4 , wherein each said cold sheet incorporates said one or more cooling channels.

6. The magnetic geared device according to claim 3 , wherein the N stator cores are integrated into a single core.

7. The magnetic geared apparatus of claim 1 , further comprising one or more thermal channels configured to transport heat away from the stator structure.

8. A housing structure, and a plurality of mechanical supports configured to connect the N stator cores to the housing structure; 10. The magnetic geared device of claim 1, further comprising:

9. The magnetic geared apparatus of claim 8 , wherein the plurality of mechanical supports are further configured to transport heat away from the stator structure.

10. a plurality of magnets arranged in a Halbach configuration and attached to at least one rotor core; 10. The magnetic geared device of claim 1, further comprising:

11. The magnetic geared device of claim 1 , wherein the N stator cores and / or the N rotor cores are configured to reduce eddy currents.

12. 2. The magnetic geared machine of claim 1, wherein electrically insulated ferromagnetic laminations are arranged in a lamination direction perpendicular to an air gap surface and perpendicular to a direction of motion of the rotor relative to the stator, thereby limiting eddy currents in the stator core and the rotor core.

13. 2. The magnetic geared device according to claim 1, wherein the N rotor cores and / or the N stator cores are formed of ferromagnetic particles that are electrically insulated from one another, thereby limiting eddy currents within the rotor cores and / or the stator cores.

14. The magnetic geared machine of claim 1 , wherein the N stator cores include stator core teeth arranged in a substantially open slot configuration for magnetic flux modulation.

15. The magnetic geared device of claim 1 , wherein the N stator cores include split-tooth flux modulators.

16. 2. The magnetic geared machine of claim 1, wherein the N stator cores are substantially fused within the stator structure and / or the N rotor cores are substantially fused within the rotor structure, such that the toroidal winding is substantially encompassed by a substantially fused stator and / or a substantially fused rotor.

17. The toroidal winding is A flat ribbon made of multiple strands of wire and placed within the stator core slots 2. The magnetic geared device of claim 1, comprising:

18. 20. The magnetic geared apparatus of claim 17, wherein the ribbon is made of Litz wire construction.

19. 20. The magnetic geared device of claim 17, wherein each of said strands of wire has a rectangular cross section, thereby minimizing ohmic losses.

20. 18. The magnetic geared device of claim 17, wherein the position of each of the strands of wire within the ribbon is varied with respect to a respective stator core slot to minimize the proximity effect and thereby minimize ohmic losses.

21. 10. The magnetic geared machine of claim 1, wherein the stator structure and the rotor structure are arranged to maximize axial and / or radial magnetic flux.

22. 2. The magnetic geared device of claim 1, wherein N=2, and the N stator cores and the N rotor cores are arranged to form a double-gap radial flux machine.

23. 23. The magnetic geared device of claim 22, wherein three of the four sides of the toroidal winding are cooled.

24. 2. The magnetic geared device of claim 1, wherein N=2, and the N stator cores and the N rotor cores are arranged to form a dual air-gap axial flux machine.

25. 2. The magnetic geared apparatus of claim 1, wherein N=3, and the N stator cores and the N rotor cores are arranged to form a three-gap flux machine including either two axial air gaps and one radial air gap or one axial air gap and two radial air gaps.

26. 2. The magnetic geared apparatus of claim 1, wherein N=4, and the N stator cores and the N rotor cores are arranged to form a five-gap flux machine including either two axial air gaps and three radial air gaps or three axial air gaps and two radial air gaps.

27. The magnetic geared machine of claim 1 , wherein the N stator cores and the N rotor cores are arranged to form a multi-gap machine, the air gaps being adjacent.

28. 28. The magnetic geared apparatus of claim 27, wherein the multiple air-gap flux machine is configured as a linear machine.

29. 20. The magnetic geared device of claim 17, wherein the multiple air gaps merge into a single combined air gap.

29. 2. The magnetic geared device of claim 1, wherein the toroidal winding is a printed circuit board (PCB) winding.

30. 1. A magnetic geared double air gap machine configured as either an electric motor or generator and including a stator structure and a rotor structure arranged to improve torque generation, the stator structure includes two stator cores and a shared toroidal electrical winding; and the rotor structure includes two corresponding rotor cores, the stator core and the rotor cores arranged to form a dual air-gap radial flux machine or a dual air-gap axial flux machine; Double gap device with magnetic gears.

31. 1. A magnetic geared three-gap machine configured as either an electric motor or generator and including a stator structure and a rotor structure arranged to improve torque generation, the stator structure includes three stator cores and a shared toroidal electrical winding; and the rotor structure includes three corresponding rotor cores, the stator core and the rotor cores arranged to form a three-gap flux machine including either two axial air gaps and one radial air gap or one axial air gap and two radial air gaps; Three-gap device with magnetic gears.

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