Patent Application
20210066983
The descriptions are generally related to motors, and more particular descriptions are related to stator conductors.
Electric motors are used in devices that range from small appliances and electronic devices to large motors for pumps and factors. Motors are one of the world's largest consumers of electricity, but are traditionally either very inefficient or very expensive. Energy efficiency for a motor refers to how much of the electrical energy input is converted to work output from the motor. Small appliance motors in the home traditionally have an efficiency slightly better than 50 percent. Large motors for pumps and factories often have efficiencies in excess of 90 percent, but are very expensive. Linear motors move equipment at high speeds and actuate along one axis, while rotary motors turn a shaft and often are geared to trade speed for torque.
In a traditional motor, conductors 112 insulated by paper, enamel, plastic such as polyimide films, or epoxy as insulators 114. The traditional wiring illustrated in coil 100 can cause failures such as motor burnout, where the thermal expansion increases pressure between wrapped wires at the same time as the insulation layers become softer with increased temperature. The combination can eventually cause the wires to short, arc, or otherwise fail after multiple cycles. Insulators 114 are usually thin to allow maximum current capabilities in relationship to the available volume of conductor 112. Making the insulation thicker to prevent shorts between windings would both decrease the amount of available conductor in a pole with a fixed volume available for windings, and increase the resistance of the stator windings. Motor efficiency increases as losses decrease, but the motor losses increase proportional to the square of the current multiplied by the resistance. Thus, increased winding resistance decreases motor efficiency. Additionally, traditional dielectrics or wire coatings for magnetic wire are good thermal insulators, which means increased coating thickness operates to increase the retention of heat in the wire. The thermal performance of wire coatings creates a contradiction in performance, where increasing the thickness allows higher voltages, but promotes overheating. Thin wire insulation is a major cause of motor failure in traditional designs, and overheating limitations define motor system performance envelopes.
The wires tend to be round, as illustrated, which tends to increase the contact stresses where the cylindrical shape comes into contact with another cylinder on a line or even a point if the wires are at an angle. Increasing pressure as the wires expand, coupled with the softening of the material of insulator 114 with heat can cause a short when the gap between the wires is small compared to the voltage differences. Once the windings start to arc, a runaway effect can literally cause the motor to burnout.
Coil 100 illustrates different stages of the wire in the coil, which may not necessarily all be present in the same coil, but are shown together in coil 100 for purposes of illustration. The wires where insulator 114 maintains its integrity (to the left side of coil 100) can remain electrically isolated 122. Once the coating starts to compress due to the heat and forces within the motor, the conductors 112 do not necessarily have to touch to cause electrical short 124, which can develop when the insulation does not provide electrical isolation for the voltages in use in the engine. As one illustration, insulator 114 is shown as “melted” in the electrically shorted scenario. More significant failure is illustrated as physical short 126, where insulator 114 is sufficiently displaced to allow conductors 112 of different wires to make physical contact.
Insulator 114 can be improved with additional layers or additional materials, which comes at the cost of increasing the thickness, reducing the available volume for conducting material, increasing the resistance of the windings, and decreasing the efficiency of the motor or other electrical device. Many materials that would be excellent insulators are not flexible and are not conducive to making windings because they have properties that does not provide good current flow (where magnetic flux is proportional to the current flowing in a loop). Increasing the flux requires increasing the current, and given a fixed resistance means increasing the voltage. A balance is usually created in the design for an appropriate voltage by increasing the number of windings, but this reduces the available volume for the conductor by requiring more insulation.
In a traditional motor, the stator often consists of multiple windings of traditional magnet wire, where the insulation is as thin as practical for the power, current, voltage, and thermal requirements of the device. What is often overlooked in motor applications is the effects of vibrations and thermal cycling, where the creation of power in the motor also creates equal and opposite forces that exert on the wires, causing rubbing between the wires, eventually leading to failure.
The following description includes discussion of figures having illustrations given by way of example of implementations of embodiments of the invention. The drawings should be understood by way of example, and not by way of limitation. As used herein, references to one or more “embodiments” are to be understood as describing a particular feature, structure, and/or characteristic included in at least one implementation of the invention. Thus, phrases such as “in one embodiment” or “in an alternate embodiment” appearing herein describe various embodiments and implementations of the invention, and do not necessarily all refer to the same embodiment. However, they are also not necessarily mutually exclusive.
Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as discussing other potential embodiments or implementations of the inventive concepts presented herein.
As described herein, a stator assembly includes layers of coated conductor. The coating is insulative and provides electrical isolation of adjacent conductor layers. The multiple layers of coated conductor form a stator core, and the stator includes magnet assemblies that sandwich the stator core. The conductor layers have a rectangular cross section.
In contrast to wire windings as a stator conductor, the stator assembly includes coated conductor, with a variable or non-constant cross section. In one embodiment, the stator assembly includes sapphire coated aluminum layers. Coated conductor layers in the stator can enable high performance motors to be built combining the best tradeoffs between minimizing the resistive losses and minimizing the eddy current losses. In one embodiment, the coating includes anodizing to produce microcrystals of sapphire or aluminum oxide, which has excellent insulative performance as well as excellent thermal conductivity. More specifically, the electrical insulation and thermal conductivity of sapphire on aluminum is improved relative to typical plastic, silicon, resin, or other traditional wire insulator. The improved properties decrease the likelihood of motor burnout or failure. In one embodiment, the processing patterns the conductor to reduce eddy current losses. In one embodiment, the processing patterns the conductor to improve fill factor to increase conductivity. In one embodiment, the patterning can provide both fill factor improvement as well as eddy current reduction.
The stator assembly in a motor can provide motors and electromotive devices with high efficiencies that are robust and allow overpowering beyond nominal ratings. For example, in one embodiment, a motor can temporarily be operated beyond normal ratings for temporary surges of power. For example, with proper thermal conductivity and electrical insulation with the coated conductor, temporary surges of approximately 200 percent or more power can be achieved. Typically the ratings refer to limits for sustained or prolonged operation. But with thermal conductivity and electrical insulation, temporary surges will not cause the breakdown of the motor. Thus, motors can be designed for efficiency in size and speed, while allowing bursts of power. Such a design allows the use of a smaller motor as compared to traditional design, which requires designing to the ratings seeing that even short durations of power can cause damage to a traditional motor.
Wire has a constant cross section. In one embodiment, the coated conductor is created from a chemical reaction of the conductor metal, such as sapphire coated aluminum, where sapphire is understood to be aluminum oxide. In one embodiment, the coated conductor is created from a chemical deposition or other process to provide a nano-layer of material on a conductor, such as diamond coated copper. The stator core includes a conductor with a high thermal transport coating material, where the coating has a high dielectric constant insulating the metal. In one embodiment, the insulative coating includes a traditional insulator, silicon, or a diamond-like coating. In one embodiment, the conductor with insulative coating is patterned to create magnetic fields for a linear motor or a rotary motor, and provides greater efficiencies, increased power density, and reliability. The use of advanced manufacturing techniques can result in lower motor costs than traditional motors that have windings on an iron-based core.
The stator core includes layers or one or more stacks of coated conductor. In one embodiment, the patterning of the conductor layers allows placing more conductor in a tighter volume, which reduces resistive losses. Thus, the stator can include multiple layers in a three dimensional shape. Multiple thin layers of coated conductor reduces the cross-sectional area of the conductor, which reduces eddy current losses relative to a conductor with a larger cross-sectional area. The cross section is not typically a consideration in traditional motors, seeing that insulated wire windings are used, which constrains the eddy currents.
Winding the wires around an iron-based motor core results in a manufacturing cost, even with automated manufacturing processes. The layers of coated conductor can be processed with mechanical equipment (e.g., die-stamping machines), laser or other precision-processing machining, or other manufacturing processes. With such processes, the conductor layers can be manufactured at a cost comparable to traditional motors, rather than high-end costs that might otherwise result.
In one embodiment, magnet layers 222 and 224 include a Halbach array. A Halbach array alternates the orientation of magnets with overlapping fields, with one set oriented to produce fields parallel to the working air gap (“North-South”), while additional magnets produce fields perpendicular to the air gap (“East-West”). With such an arrangement, the fields add magnetic flux on one side of the first array and cancel flux on the other, producing a greater magnetic field density where desired, and reducing the field where not beneficial without the need for a soft magnetic return path. The Halbach array can provide many variations of linear, cylindrical, and axial flux arrays. Any Halbach array will benefit from use with the layered coated conductor stators described throughout.
As illustrated, stator core 210 includes multiple layers of conductor 230 stacked on top of each other between the magnet layers. Conductors 230 include a cross section that is rectangular, and has a pattern to provide an electrical path radially around the stator within the conductor layer. In one embodiment, conductors 230 are patterned to stack with another group of conductor layers to increase the density of conductor within stator core 210.
In a traditional motor the stator often consists of multiple windings insulated by paper, enamel, or some plastic such as polyimide films that are usually thin to allow maximum current capabilities in relationship to the available volume. Decreasing the amount of available conductor in a pole with a fixed volume available for windings, by making the insulation thicker, would increase the required volume for insulation needed to prevent shorts between windings. Increasing the required volume of insulation increases the resistance of the stator windings, and increases the losses proportional to the square of the current multiplied by the resistance. It would also increase the retention of heat in the wire as most dielectrics used for magnet wire are good thermal insulators, creating a contradiction in performance, where increasing the thickness allows higher voltages, but promotes overheating. The thinness of the insulation is a major cause of motor failure in traditional designs and overheating limitations define motor system performance envelopes.
Copper is often the preferred conductor for motor windings, especially in small motors, due to superior electrical conductivity versus aluminum. Wire is traditionally extruded with a constant cross section and then coated with an insulating layer and wound in coils to provide a switchable magnetic field. The desired motor characteristics determine the winding choice in terms of thickness, number of windings and configuration. In general, eddy currents can be reduced by increasing the number of smaller parallel strands, but such an approach has a penalty in terms of the volume efficiency or packing density. Sixty percent more aluminum by cross-sectional area is needed to provide the same conductivity as the equivalent length of copper.
Many commonly used dielectrics are flammable, and will combust at the high temperatures possible in overheating conditions, made worse by the thermal insulating characteristics of these coatings. Thinner materials can fail both mechanically and electrically. Motor failure occurs when the losses which produce heat destroy the insulating material between the conductors, which can be referred to as insulation, dielectric, or coating. The destruction of the insulation produces a short which decreases the magnetic field, causing the power supply to try to drive the motor with even more current or voltage. When more current flows through the short, the conductor further heats up the affected region or creates a mechanical failure. Motors that experience such shorts have to be stripped and rewound, with associated costs of broken equipment, downtime, and repair costs. In many cases the complexity of manufacturing the windings creates high costs which are impractical to manufacture in mass production quantities.
With windings 302 and windings 304, there are still gaps between the conductors. Additionally, there is a practical limit on how thin insulators 312 and 322 can be. Reducing the thickness of traditional insulation coatings is impractical with plastic or other dielectrics since they provide both mechanical isolation and electrical isolation. As the motor spins and heats up, the magnetic force will create an equal and opposite force in the opposite direction, which causes the wires to press into each other, and the insulation provides the mechanical isolation of the wires. Many coatings become soft as they heat up. Thus, reducing the thickness of the insulation in windings 302 and 304 can cause mechanical as well as electrical isolation issues.
Assembly 306 includes a stack of conductors 330, which include coating 340. Making a stack of conductors 330 with thin coating 340, more conductor can be put into the available volume as compared to windings that result in gaps between wires. Many commonly used dielectrics are flammable, and will combust at the high temperatures possible in overheating conditions, made worse by the thermal insulating characteristics of these coatings. Making such coatings thinner can increase the risk of failure, both mechanically and electrically. However, coating 340 represents a coating created by bonding material to conductor 330. In one embodiment, coating 340 represents a chemical reaction with conductor 330.
For example, consider that conductor 330 is or includes aluminum, which can be chemically reacted to create an anodized coating. In one embodiment, coating 340 is sapphire (aluminum oxide) over the aluminum conductor. A chemically-reacted or bonded coating is mechanically much stronger, as well as superior in dielectric insulating characteristics to many traditional magnet wire coatings. As another example, diamond coated copper is even better for thermal conduction than sapphire over aluminum, although processing diamond onto copper may require controlling graphite and contaminate content, seeing that contaminates cause the diamond to become somewhat conductive, which degrades its performance as an electrical insulator. Pure diamond is ideal as an insulator. With greater strength, hardness, and dielectric constant, there are obvious advantages over both traditional coatings as well as sapphire coated aluminum. However, both sapphire and diamond coatings can be broken when applied as thin layers. Sapphire can be brittle and will crack when flexed. Diamond coatings may be preferably only a few microns thick, which easily break. However, it will be understood that sapphire coatings can heal with exposure to oxygen, whereas diamond coatings will not. With the ability to control the coating thickness by the electro-chemical or anodizing process, the insulation thickness of coating 340 can be controlled based on the required or planned voltages in the stator layers or windings. Thinner wires have reduced eddy currents generated, but given a required breakdown voltage, the ratio of the coating thickness to conductor area becomes a problem with very thin wires in traditional motor designs. The stacks of conductor 330 can achieve more conductor with thinner coating 340.
As is generally understood, the strength of the induced electromagnetic field is directly proportional to the current, and the power is proportional to the current multiplied by the counter electromotive force (EMF) voltage. Given these proportionalities, the designer can tune a particular motor's performance by either controlling the geometry of conductor 330 or controlling the thickness of coating 340, or controlling both. A designer can control the thickness and shape of conductor 330, and the type and thickness of coating 340.
Conductors 330 have a rectangular cross-section 332. Conductors in wire form, such as the metal wires in windings 302 and 304, are usually fixed in cross section or diameter, and the resistance is based on the amount of material for switching frequencies typically used in motors. Smaller cross sections have greater resistive losses than larger cross sections with the same conductor, at least in the case of aluminum. A wire size is typically chosen to allow a desired number of turns in the winding, to set the voltage and current by the minimum volume and packing requirements. Lowering the total system conductive losses by making some sections larger is possible by taking advantage of the available space or volume.
In one embodiment, increasing the amount of conductor 330 can reduce total resistance with an acceptable weight penalty or material costs. Increasing the amount of conductor 330, such as through the patterning (not shown in
Assembly 306 does not illustrate the magnets that would be part of a motor assembly. As mentioned above, the stack of conductors 330 can be sandwiched between two layers of magnets (such as what is illustrated in assembly 200), or two layers of conductors 330 can sandwich a magnetic layer. Traditional motors include silicon steel laminations that leverage the increased magnetic permeability of steel or other suitable materials over air. Such silicon steel laminations have several downsides that offset the increased field strength. One tradeoff is hysteresis losses as the fields switch back and forth during motor commutation. As the fields switch back and forth they can saturate, limiting the maximum field that can be produced. Additionally, traditional laminations add weight and occupy volume that could be used for additional conductors.
In one embodiment, the conductor stack of stator assembly 306 is used in a permanent magnet axial flux motor. Use of permanent magnets can enable the elimination of the steel laminations, which will free up volume that can be replaced with more conductors 330. Increasing the amount of conductor 330 to assembly 306 tends to increase the reluctance, and produces additional magnetic force for the same amount of current flowing. In one embodiment, a motor designed with assembly 306 utilizes additional poles, additional magnetic material, additional conductors, increased stator radius, or any combination of these. The increases in number of poles, amount of magnetic material, or radius can produce greater power and torque for a given volume and weight. It will be understood that such increases may require switching speeds relative to less material, and may increase operating voltages and magnetic poles and material.
Since motors and other electromagnetic machines are typically thermally limited devices, a combination of reducing eddy current losses and reducing resistance losses produces motors with greater efficiencies. In one embodiment, coating 340 represents a material that is mechanically stronger than conductor 330. Mechanical strength refers to the ability to withstand the forces produced by operation (spinning and heating) of the motor. In traditional motor design, the insulation is mechanically weaker than the copper or aluminum wire, which creates a need for additional structures to maintain wire placement in the motor. By Newton's Law of Force, the wires and their insulators will be pushed and pulled as the EMFs are applied for advancing the rotor or moving a segment as a series of pulses. Such pushing and pulling creates forces on the insulation than can cause motor burnout. In one embodiment where coating 340 is mechanically stronger than conductor 330, the mechanical nature of the motor is inverted, and the insulation can provide structure for the stator. Thus, instead of requiring additional structure, in one embodiment, stator assembly 306 can become the structure for a frameless motor, or the mechanical system itself. In one embodiment, alternating layers of conductor 330 have alternating edge overlap, where in the event of a failure of an insulating anodized sapphire coating, there is a flat surface in contact with the edge instead of another edge. Such alternations can allow self-healing of the motor, because when exposed to oxygen, an anodized sapphire coating will heal naturally over time. The overlapping of the materials can reduce problems with vibrations as the layers of metal rub against each other.
Motor power is limited thermally when eddy current losses and resistance losses contribute to stator failure. Such losses can also result in mechanical failure by warping, overheating, or loss of lubrication due to excess heat, or a combination. Increasing efficiency by even ten percent from eighty to ninety percent, might not seem significant from the standpoint of total power consumption, but such improved efficiencies can decrease waste heat and required cooling by fifty percent, from twenty percent to ten percent of total power. Thus, even small efficiency improvements can eliminate cooling requirements which have their own power, size, and component costs.
Referring to coil 402, the coil includes an electrical path that winds radially around center 410, within a plane of the conductor layer. Coil 402 includes spokes 420 that extend between an inner connection 432 and an outer connection 434. Inner connection 432 is within the conductor layer close to center 410. Outer connection 434 is close to an outer edge of the conductor layer. As illustrated, coil 402 includes alternating outer and inner connections between adjacent spokes 420. The alternating connections provides the coiled electrical path of the conductor layer. Such a path can be considered from one perspective as a “two-dimensional”path as compared to the three dimensional path of a traditional winding, which has turns in all three dimensions, as opposed to have turns constrained within a plane.
Similar to coil 402, referring to coil 404, the coil includes an electrical path that winds radially around center 410, within a plane of the conductor layer. Coil 404 includes spokes 440 that extend between an inner connection 432 and an outer connection 454. Inner connection 452 is within the conductor layer close to center 410. Outer connection 454 is close to an outer edge of the conductor layer. As illustrated, coil 404 includes alternating outer and inner connections between adjacent spokes 440. The alternating connections provides the coiled electrical path of the conductor layer. Such a path can be considered from one perspective as a “two-dimensional” path as compared to the three dimensional path of a traditional winding, which has turns in all three dimensions, as opposed to have turns constrained within a plane.
The physical dimensions of the spokes and connections can be different depending on how many portions or segment of the conductor layer there are. It will be understood that the conductor layers are not limited to four or six portions, but can include any number of portions, including odd numbers of portions. The shape, size, and number of portions can be dependent on the implementation of the motor. Additionally, while a similar shape of the spokes and connection is illustrated for both coils 402 and 404, other shapes can be used. The spokes can be thicker or thinner, as well as the connections. In one embodiment, spokes 420 and 440 are wider as the spoke extends further away from center 410 to the stator edge. Varying the spoke width can increase the amount of conductor that can be packed within a stator assembly. In one embodiment, spokes 420 or spokes 440 or both have a consistent width from the inner connection to the outer connection. Different spoke widths can be observed as a varying cross-section of the conductor layer.
In general regarding the conductor layers, regardless of numbers of portions or size and shape of the spokes, the conductor layers are stacked for a stator assembly. Instead of winding around a steel core as previously done, coils 402 and 404 can wind radially around center 410, and connect to adjacent layers, either in series or in parallel, to provide more electrical path of conductor between layers in the stator assembly.
For purposes of example, consider a discussion with reference to coil 404 created from a layer of aluminum conductor. The discussion will be understood to be able to apply to layers of different conductor and different coatings. In one embodiment, coil 404 is one of multiple layers of aluminum. In one embodiment, coil 404 is created from processing a sheet of aluminum. Such processes aluminum can be created as a rectangular component that is adjusted to coil radially. In one embodiment, coil 404 is created by one or more of stamping or cutting the conductor. The processed conductor is treated to create an electrically conductive pathway with an insulator coating. In one embodiment, multiple layers are joined to create an inductor, and then processed to create the coating. In one embodiment, multiple layers are created and processed to create the coating, and then joined in layers. The inductors or coils can be formed into a stator, which can improve the amount of conductor in the volume, while reducing the amount of insulation required and the losses from eddy currents and bulk resistance.
Varying the order of joining, cutting, and stamping to optimize a particular characteristic can be made depending on the application for linear, rotary, or fixed couplings of magnetic fields for electromagnetic machines. Putting the conductors in varying configurations of series and parallel and varying the dimensions, number of layers, or complexity of the current path allows tuning of the machine to desired performance, efficiency, voltage, and maximum current carrying capabilities. In one embodiment, spokes 440 and inner and outer connections 452 and 454 can be formed through cutting aluminum by laser, plasma, water jet, stamping, or other process, or a combination. In one embodiment, spokes 440 can be further processed by cutting radius lines, or lines that extend along a radius of a circle with a center at center 410, and extend between inner connection 452 and outer connection 454. Such cutting can also be accomplished with laser, water jet, stamping, or other process, or a combination. Other drawings discussed below more explicitly illustrate such radius lines to create segments in the current path of the spoke.
Separating the spokes into multiple parallel segments limits the current path in one direction while only reducing the current path in the other dimension by the volume lost by the insulating layer and removed material. With multiple parallel current paths for at least a portion of the conductor coil, the performance can be tuned by selecting a configuration that provides the greatest current carrying capabilities while reducing eddy current and bulk resistance losses. In one embodiment, the portion of the conductor layer that has parallel paths is limited to a portion proximate where the conductor layer will pass by the magnets of the magnetic layers. In accordance with what is illustrated by coil 404, in one embodiment, the design can connect layers of desired thicknesses by joining them at the inner circumference, the outer circumference, or with alternating joints. Alternating the positions of cuts and edges as the layers overlap can prevent localized rubbing failure and heating if the conductor layers or plates are not fixed, and wear occurs due to motion.
In one embodiment, coil 404 replaces traditional insulation on the stator with anodized aluminum, which is a form of aluminum oxide also known as sapphire, achieves multiple advantages. Anodizing techniques can convert the surface of a layer of aluminum conductor into aluminum oxide or sapphire, which is a coating that is hard, strong, resistant to chemical attack, highly electrically insulating, and yet has good thermal conducting characteristics. As such, coil 404 can be used to create a stator with properties in terms of efficiency, durability, strength, and capabilities that are improved relative to traditional wound motors.
The anodizing creates sapphire, which even as a microscopic sponge-like material with holes, fingers, gaps, cracks, and varying thickness, has better dielectric or insulation characteristics than traditional wire insulators. Additionally, sapphire is much harder and tougher as compared to polyimides, plastic, enamel, paper, and other common wire coatings, and has approximately 100 times better thermal conductivity. The dielectric constant of sapphire is greater than 10 kilovolts per millimeter, or >10 kV/mm. The volume resistivity of sapphire is greater than 10 exp 14 ohm*cm. Thus, the volume resistivity of sapphire is approximately the same as silicon, but with a thermal conductivity of 30 W/mK versus a silicone rubber insulator with a thermal conductivity of 0.3 W/mK. The 100 times better thermal conductivity improves heat transfer, which reduces the risk of overheating the motor.
With modern manufacturing techniques, sapphire coated aluminum is relatively inexpensive, and naturally oxidizes or heals in the presence of oxygen to create a self-repairing mechanism. In one embodiment, the aluminum can be anodized to convert the surface of the conductive aluminum into aluminum oxide or sapphire. Sapphire coating is hard, strong, resistant to chemical attack, highly electrically insulating, and provides good thermal conducting characteristics. A coil or stator constructed from stacks of sapphire coated aluminum can provide a motor with higher efficiency, durability, strength, and over-driving capability as compared to traditional motors.
It will be understood that bending the conductor after it has been anodized to produce the sapphire coating will cause cracking. Thus, sapphire coated wire for use in traditional windings would not be possible. However, by stacking planar conductor layers, the cracking of the sapphire coating can be minimized, or effects from such cracking can be reduced. For example, such cracking may be limited to an area where the layers are meant to be connected, and so a short in the connecting portion has little to no meaningful impact on the performance of the stator. A thin aluminum oxide coating has a higher melting temperature than aluminum itself, making it difficult to burn out a motor that uses a stator of sapphire coated aluminum conductor. Traditional failures where the dielectric, insulator, or plastic heats up and fails producing shorts are reduced or even eliminated, making a motor inn accordance with what is described herein more robust than traditional motors.
Opening 540 represents a space between two spokes 510. In one embodiment, assembly 500 includes opening 540, which can provide space to nest with one or more other layers of conductors. In one embodiment, assembly 500 includes bends 522 and 524 to enable the nesting of multiple stacks of layers of conductors. In one embodiment, assembly 500 is nested with at least one stack of conductor layers that has no bends. In one embodiment, assembly 500 is nested with at least one stack of conductor layers that also has bends. In one embodiment, where stacks of layers are nested, the bending changes the electrical path length of one stack as compared to another. Electronics can control the duty cycle of driving the different paths to account for the variations in electrical path length for different stacks.
In one embodiment, assembly 500 is created with folding of electrical path 530 to provide the radial current path that provides field to drive the electromagnet motive force, and then the return path. The folding refers to the serpentine shape that results from various elements in accordance with assembly 500 coupled together to form a complete radial path (e.g., 360 degrees of folded path). The shape provided by the folding reduces the total path length verses two coils with a complete circular path.
Diagram 602 illustrates upper conductor 630 or an upper coil, which is designated as Phase 2. Diagram 602 illustrates lower conductor 640 or a lower coil, which is designated as Phase 3. Again, the labels of the phases is arbitrary, and is shown for purposes of illustration only. Additionally, designation of conductor 630 as an “upper” coil and conductor 640 as a “lower” coil is an arbitrary designation based on the specific orientation of diagram 602. In one embodiment, a motor with a three phase stator in accordance with diagram 602 can be mounted and used with the plane of conductors 620, 630, and 640 parallel with the ground, or perpendicular to the ground, or at any arbitrary angle with respect to the ground.
Diagram 602 includes crosshairs over each of conductors 620, 630, and 640, which demonstrates relative positions to each other for nesting. For example, taking flat conductor 620 as a “middle” conductor, the crosshairs align over the center point of the conductor. For upper conductor 630, the conductor is shown slightly offset above the center point of the crosshairs, and for lower conductor 640, the conductor is shown slightly offset below the center point of the crosshairs. It will be observed relative to the crosshairs how the crosshairs align on one edge of a spoke on upper conductor 630, which aligns with a complementary edge of a spoke of lower conductor 640, while the crosshair splits the middle between two spokes of flat conductor 620. It will be understood how the conductors can nest together, and with the bends in the upper and lower conductors, there will be a relatively flat stator core surface made up of alternating spokes of the three different phase stacks. The flat stator core is made up of roughly coplanar stacks interleaved with each other to position spokes of different stacks adjacent to each other. It will be understood that the path length of flat conductor 620 is actually shorter than the two bent or contoured coils of conductors 630 and 640. Traditionally such uneven path lengths would produce uneven force. In one embodiment, a solid state controller (e.g., digital microcontroller or microprocessor) drives the stator assembly of diagram 602 to compensate digitally for the uneven path lengths. The digital compensation enables lower cost mechanical systems in exchange for more complex control software.
Thus, as illustrated, in one embodiment a stator assembly includes a multiple stacks of multiple layers each. Each stack includes multiple layers of coated conductor coils, which can be electrically connected in accordance with any embodiment described herein. In one embodiment, some or all layers of a single conductor stack are connected in parallel to lower a required voltage to drive the EMF. In one embodiment, some or all layers of a single conductor stack are coupled in series to increase the required voltage. In one embodiment, the stacks include two or more coils in a serpentine shape where the coils fold over each other, to form a structure for the stator. It will be understood that the nesting of layers inside each other can increase the total amount of conductor per volume. Nesting the layers can additionally minimize the wearing and potential shorting of adjacent layers.
The perspective of diagram 604 more clearly indicates the curvature of upper conductor 630 and lower conductor 640, while the stack of conductor 620 is flat. Interleaving such stacks of layers of conductor can almost completely fill the gaps in the stator core, which provides a maximum amount of conductor in a given volume to place adjacent a magnet array. Increasing the amount of conductor in the given volume can reduce the resistive losses. In one embodiment, each phase includes a stack of layers of thin sheets of aluminum or other conductor material which lowers the eddy current losses by the square of the thickness of the plate verses a solid coil of the same shape. The thin sheet can decrease eddy current losses while increasing the voltage required to drive the current.
Assembly 700 includes radial current paths provided by conductors 722, 724, and 726. The radial current paths allow current to flow radially with respect to center 710, which provides an interface with an axle. Inner edge 732 is proximate center 710, and outer edge 734 is at a point of the conductors farthest from center 710. It will be observed that each spoke varies in cross sectional area going from inner edge 732 to outer edge 734, which increases the amount of conductor material that can be included in the stator.
In one embodiment, assembly 700 includes a flat radial section to allow a small gap between an axial flux magnetic array. The flat radial section includes the surface of the spoke of coated conductors between inner edge 732 and outer edge 734. The flat radial section can provide a relatively large surface area for cooling. The design of assembly 700 also reduces the amount of material outside the magnetic field while still maintaining a path for the current.
A stator in accordance with conductor stack 810 can lower the total system conductive losses by making some sections of the conductor larger to take advantage of the available space or volume, as opposed to a consistent cross section as with a traditional wire. In one embodiment, conductor stack 810 includes multiple layers of aluminum anodized with aluminum oxide. By patterning the conductors, current path 812 can include sections of larger cross section to reduce the total resistance by additional aluminum with only a slight weight penalty or material cost. The additional conductor material increases the machine efficiencies of the motor, and makes the stator stronger and stiffer. The increased amount of conductor can also allow more options for connecting layers and providing more material as a thermal heat sink for temporary overheating.
To create the required EMF to turn a rotor with a magnetic array, the system supplies a current through the conductor, and varies it as a magnetic field from another conductor or magnet moves. However, it will be understood that the movement of the relative magnetic fields produces a field opposing that motion, as described by Lenz's law. Conductor stack 810 illustrates induced eddy currents 814 from a magnet with a magnetic field oriented perpendicular to the direction of motion moving near conductor 810. The letter ‘B’ with the arrows represents a direction of magnetic flux due to a magnet assembly. The magnet assembly with the magnetic field B moving over a stator that includes current path 812 induces eddy currents 814 as current loops opposing the motion.
Eddy currents 814 produced in conductor 810 circulate, creating a field that must be overcome, which creates a source of losses. These losses can be decreased by making the path smaller, and putting several conductors in parallel to cause the current loops to cancel each other out. However, in a traditional system the use of parallel conductors introduces penalties from additional mechanical complexity, additional insulation, and increased resistive losses as the additional insulation decreases the available conductor. As illustrated, conductor stack 810 segments the conductor into relatively thin layers. The separation into layers can create more current paths 812 relative to a solid conductor of the same volume. The layers of conductor provide parallel paths, and the coating on the conductor provides insulation while not adding significant insulation volume.
In one embodiment, conductor stack 810 includes aluminum or copper or other metal conductor. In one embodiment, conductor stack 810 includes graphene or other non-metallic conductor. Whether metal or non-metal conductor, conductor stack 810 can improve the filling of available volume with a conductor that can minimize eddy current losses as well as resistive losses.
Applying the principle of reducing the surface area exposed to the magnetic flux to reduce the eddy currents, conductor stack 840 illustrates a similar conductor stack to conductor stack 810 of
In one embodiment, conductor stack 840 includes multiple layers of aluminum or other conductor, which is processed by stamping or cutting, or a combination, and joining into the stack, and treated to create an insulated stack of electrically conductive pathway as an inductor which for a stator. The order of stamping, cutting, joining, and treating to form the insulator can be varied. Varying the order of joining, cutting, and stamping can optimize a particular characteristic of current path 842, which can improve its suitability for an application of linear, rotary, or fixed couplings of magnetic fields for electromagnetic machines. The coated conductor maximizes the amount of conductor in the volume while minimizing the amount of insulation required. Conductor stack 840 can include varying configurations of series and parallel conductors, which can include varying dimensions, number of layers, varying shape or complexity of the current path, or a combination. It will be understood that the variations can allow the tuning of a machine to a desired combination of capabilities such as performance, efficiency, voltage, or maximum current carrying capability.
In one embodiment, conductor stack 840 includes multiple current path 842 in the same conductor plane, which are not electrically connected to each other. In one embodiment, conductor stack 840 includes multiple current paths 842 that are separated only along a path of the conductor where a magnetic array will pass over, and can be connected at the outer circumference, inner circumference, or both (for example, compare
In one embodiment, the various layers of conductor stack 840 can be connected at the inner circumference. In one embodiment, the various layers of conductor stack 840 can be connected at the outer circumference. In one embodiment, the various layers of conductor stack 840 can be connected at with alternating joints at inner and outer circumferences. In one embodiment, alternating layers of conductor stack 840 have different positions of the cuts and the edges as the layers overlap. Such variation can prevent localized rubbing failure and heating if the plates are not fixed, causing wear to occur due to motion. For example, consider current paths 842, showing three separate paths in a single conductor layer. If the next conductor layer had two separate paths, the one cut of that layer would not overlap with the two cuts of the illustrated layer, which could increase the electrical separation of the layers. Other variations will be understood in accordance with what is described.
In one embodiment, an inner circumference connection 1022 can allow the outer circumference to be free floating, allowing a stator to be connected to a shaft in the center (not shown), and the entire assembly to float relative to a housing (not shown) outside the outer circumference. For in wheel motors and other devices which are fixed to a shaft, conductor 1020 allows the outer circumference to be free standing.
Conductor core 1112 has conductor around center 1116. Magnet array 1114 is also in a circular pattern around center 1116. Center 1116 can allow for the inclusion of a shaft or rotor. In one embodiment, conductor core 1112 provides a stator core for an electric motor. In one embodiment, magnet array 1114 is separate from conductor core 1112 by a small air gap. Magnet array 1114 can be considered adjacent conductor core 1112 even when separated by an air gap. For example, magnet array 1114 can be secured in the illustrated arrangement by mounting in a housing that covers conductor core 1112. In one embodiment, magnet array 1114 includes magnets that are not rectangular, but are shaped to fill the space around the circle of assembly 1110.
Conductor core 1122 has conductor around center 1126. Magnet array 1124 is also in a circular pattern around center 1126. Center 1126 can allow for the inclusion of a shaft or rotor. In one embodiment, conductor core 1122 provides a stator core for an electric motor. In one embodiment, magnet array 1124 is separate from conductor core 1122 by a small air gap. Magnet array 1124 can be considered adjacent conductor core 1122 even when separated by an air gap. For example, magnet array 1124 can be secured in the illustrated arrangement by mounting in a housing that covers conductor core 1122. In one embodiment, magnet array 1124 includes rectangular magnets, which leaves small gaps between the magnets around the circle of assembly 1120. Assembly 1120 illustrates more magnets as compared to assembly 1110, providing more magnetic poles. It will be understood that assembly 1110 can include more magnets, and assembly 1120 can include fewer. Thus, the shape of the magnets is not necessarily related to the number of magnets in the array. More magnetic poles produces or requires higher frequency in operation as a motor or generator relative to fewer magnetic poles.
With reference to both
In one embodiment, assembly 1200 is part of a motor. Consider an example of a robotic device with the initial motion of a joint. To produce the torque required to move from a dead stop to lifting a mass, the initial power required to accelerate the arm and mass will be high, but once in motion, the power to continue at a constant velocity will be a tiny fraction of the initial power to overcome bearing losses. The initial or periodic motion of starting and stopping is much higher than the average power, requiring several times the average power requirements. However, it will be understood that the higher power is only needed for a relatively short period of time, such as a few seconds.
In one embodiment, the structure of assembly 1200 can allow the overdriving of the motor, with current or voltage or both that would be high enough to cause a failure if sustained. However, by driving the current or voltage or both for only a brief period and then allowing several seconds for cooling, the system can sustain high power period, while allowing for a smaller, lighter overall motor. The structure of assembly 1200 provides increased thermal conductivity between layers, which improves cooling. Additionally, in one embodiment, the motor can be driven with temporary power surges with less likelihood of overheating. The reduced likelihood of overheating allows the use of a smaller motor than would traditionally be used, because such a motor can temporarily be driven with excess current. The overdriving can be double or more the steady state usage. Use of a smaller motor reduces costs and reduces the motor weight, extending the applications of an electric motor in accordance with assembly 1200. Normally a motor is sized to the peak performance requirements even if it is used less than ten percent of the time. Such motor sizing adds excess weight, costs, and complexity. By sizing a motor to the average required load because of the ability to temporarily overdrive the motor to drive the peak requirements, the design can use a smaller, lighter, more cost effective motor without sacrificing performance.
For example, similar to the power required for initially moving a robotic appendage or joint, the power required for vertical takeoff and landing of electric aircraft during takeoff or maneuvering might exceed the requirements for cruising. A motor with a stator of stacked coils in accordance with assembly 1200 can withstand the high heat output and possible lower efficiencies for short durations. Once the desired altitude or steady state operation is reached, the motor controller can lower the power output, and operate within a motor's designed optimal efficiency range. Similarly, for accelerating an electric vehicle away from a stop, the electric vehicle might need five times the nominal power, for example, four wheels with 10 kilowatts nominal per wheel rating, can produce 200 kilowatts of power (268 Horsepower) for a few seconds. The same motors can provide high efficiency operation while driving at 55 miles per hour, which being lighter and smaller, and therefore resulting in less un-sprung mass than a nominal 50 kilowatt motor per wheel.
In one embodiment, system 1220 includes connectors 1242 and 1244 to connect different layers or different conductor stacks, or both. In an embodiment where multiple phases are used, connectors 1242 and 1244 can provide connection points to different phases. In one embodiment, connectors 1242 or 1244 or both can be on the inside of the assembly, closer to center 1224. While not specifically shown, it will be understood that system 1220 can include one or more bearings for a shaft. In an embodiment where the connectors are in center 1224, system 1220 can include one or more bearings around the outside of the conductor core.
Traditional motors often have silicon steel laminations that leverage the increased magnetic permeability of steel or other suitable materials over air. However, these laminations have several downsides that offset the increased field strength. They have hysteresis losses as the fields switch back and forth during motor commutation, they saturate, limiting the maximum field that can be produced, they add weight, and they occupy volume that could be used for additional conductors. In some electromotive machines such as Permanent Magnet Axial Flux motors by way of example, by eliminating the steel laminations, stators based on stacks of coated conductor as described herein can replace freed up volume with more conductors. Increasing the conductor increases the reluctance, but given the same current flowing, produces additional magnetic force. If space is available, advanced designs for axial flux motors can be optimized with additional poles, additional magnetic material, additional conductors, and increased radius, producing greater power and torque for a given volume and weight. The same motors can require higher switching speeds, voltages, and magnetic poles and material. If the magnetic fields can be produced by the conductor with lower losses and heat produced, the system benefits. Such a tradeoff can result in efficiencies well over ninety percent in motors. A stator in accordance with what is described herein can provide a motor that is cost-effective to produce as well as being efficient.
For example, assembly 1400 can include or be modified to include a mechanical mounting to couple the stator assembly to axle 1440. In such a design a rotor can rotate freely around the shaft. Such a design can be useful for an in wheel motor application. In another example, assembly 1400 can include or be modified to include a mechanical mounting to couple the stator assembly to a motor housing. In such a design a rotor can be fixed to axle 1440.
Metal 1510 provides electrical conduction for conductor 1500. In one embodiment, metal 1510 represents copper wire. In one embodiment, metal 1510 represents an aluminum wire. Metal 1510 can be another metal to provide conduction. Metal 1510 is illustrated as having a rectangular cross-section. In one embodiment, the rectangular cross-section is square. Metal 1510 can be referred to as a flat or ribbon type of wire.
Conductor 1500 can be referred to as a hybrid conductor, because metal 1510 is coated in two different types of insulator: a hard insulator and a soft or flexible insulator. Conductor 1500 includes ceramic insulator 1520, which directly contacts metal 1510 and adheres to the metal. Adhering refers to the mechanical connection of ceramic insulator 1520 to the metal. In one embodiment, ceramic insulator 1520 is also chemically bonded to metal 1510. With a chemical bonding, ceramic insulator 1520 adheres directly to the surface of metal 1510, where at least a thin layer of the metal and ceramic interact chemically.
Ceramic insulator 1520 can be in a hard insulator such as a glass compound or a ceramic compound. Ceramic refers to a non-conductive material, such as a crystalline oxide (for example, a metal-oxide), a crystalline nitride (for example, a metal nitride), or a crystalline carbide. In one embodiment, ceramic insulator 1520 is a glass compound, which refers to a crystalline structure that is translucent or transparent. As a crystalline structure, a glass compound can be considered a specific type of ceramic compound. Ceramic insulator 1520 provides electrical isolation between layers of metal 1510 even in high voltage applications. Ceramic insulator 1520 has good electrical isolation but is not flexible. Certain ceramics may not chemically adhere to metal or may not even mechanically adhere well to metals.
Flexible insulator 1530 represents a soft or flexible insulator that is directly in contact with ceramic insulator 1520. Flexible insulator 1530 can be like traditional insulation such as plastic, enamel, epoxy, polyimide film, or other relatively soft material that adheres to ceramic insulator 1520. Flexible insulator 1530 is a non-ceramic insulator or non-ceramic insulative coating. In one embodiment, flexible insulator 1530 mechanically adheres to ceramic insulator 1520. In one embodiment, flexible insulator 1530 mechanically and chemically adheres to ceramic insulator 1520.
Ceramic insulator 1520 and flexible insulator 1530 can be relatively thin layers of material. A single layer of insulation a micron thick on a 1 mm (millimeter) by 1 mm outer dimension square wire would have a cross section of 0.4 percent of the conductor volume. Nine wires with ⅓ mm×⅓ mm cross section would have 9 times the relative cross section of insulation or 3.6 percent, reducing the overall current carrying capability, which in turn would increase the resistance and lower the efficiency of a motor made with conductor 1500. Thus, the wires represented by metal 1510 can be coated by thin layers for ceramic insulator 1520 and flexible insulator, making the conductor what is termed magnet wire, where the insulation is as thin as practical for the power, current, voltage, and thermal requirements of the device.
While traditional insulator coatings can provide mechanical, electrical, and chemical insulation, they may still be susceptible to the vibrations and thermal cycling common in motor use, especially in higher power devices with constant use. The vibrations cause rubbing between the wires as they exert equal and opposite forces between the rotor and stator, which compresses traditional insulators and eventually leads to wear because of the creep of the insulation under heat and pressure, or other failure mechanisms.
In addition to ceramic insulator 1520 and flexible insulator 1530, conductor 1500 includes beads 1540, which turn flexible insulator 1530 into hybrid layer 1542. It will be observed that the circles or dots representing beads 1540 in conductor 1500 are only shown between layers of metal 1510. In one embodiment, a practical application of conductor 1500 will include beads 1540 combined with the material for flexible insulator 1530 to surround all of metal 1510.
In one embodiment, beads 1540 represent individual elements of a glass, ceramic, or metal oxide. In one embodiment, beads 1540 represent individual balls of material. The balls can be spherical or some other rounded shape. In one embodiment, beads 1540 represent individual elements of a powder, which refers to a material that may not have uniform shape or size, such as a powder of sapphire, a glass powder, or ceramic powder. In one embodiment, the balls have relatively uniform shape and size.
Conductor 1500 with hybrid layer 1542 provides a compound solution to provide magnet wire with a hard insulator, ceramic insulator 1520, to provide a hard coating that has good thermal transport properties. Ceramic insulator 1520 provides an insulator that does not fail under thermal expansion, vibration, or stress conditions, even if an arc passes through it. The combination of ceramic insulator 1520 and beads 1540 provides a hard and sturdy mechanical separation, which prevents both physical contact of the conductors, as well as maintaining spacing between them to prevent arcs and shorts. Ceramic insulator 1520 allows for a thin layer of conductor, which improves the cooling attributes of a motor or device using conductor 1500, because it has a high thermal conductivity.
With beads 1540, flexible insulator 1530 can be thinner as compared to traditional wiring, which means the flexible or organic coating will cause significant heating of the wire. Even when the wire heats up and flexible insulator 1530 softens, beads 1540 provide a layer to prevent shorting of the wire. Ceramic insulator 1520 should provide electrical isolation of the wires, but the reality is that if conductor 1500 is wrapped, ceramic insulator 1520 is subject to cracking, which could cause areas of potential vulnerability in the electrical isolation. Whereas flexible insulator 1530 could normally protect such areas, if flexible insulator 1530 softens under the pressure of use, such vulnerable areas could still be exposed, resulting in a short. With beads 1540, even if there are cracks or imperfections in ceramic insulator 1520 at the same time that flexible insulator 1530 is displaced, the beads can maintain sufficient distance between layers to prevent a short.
In one embodiment, the rectangular shape of metal 1510 provides a geometric advantage relative to the use of beads 1540. With the use of a rectangular metal 1510, beads 1540 can distribute the load on the metal due to the stresses of use of a motor or other device. In addition to spreading the load, the rectangular shape increases the packing density, given that rectangles pack denser than circles. In one embodiment, the size of beads 1540 is designed to maintain a minimal gap between layers of metal 1510. In one embodiment, conductor 1500 includes thousands of beads between each portion of metal 1510.
In one embodiment, conductor 1500 includes aluminum wire as metal 1510, which can be anodized with a thin layer of oxide to provide ceramic insulator 1520. The aluminum oxide can provide insulation as well as an oxide surface to improve the adhesion of flexible insulator 1530. In one embodiment, hybrid layer 1532 includes flexible insulator 1530 as a plastic, epoxy, or other matrix material mixed with a powder or beads of glass, aluminum oxide, or other suitable material, binding them to the surface of metal 1510, or more specifically, the surface of ceramic insulator 1520 on metal 1510.
Under the above example, the combination of materials of conductor 1500 allows flexing, with the aluminum oxide layer and glass beads providing enhanced insulation, and the spacing material of the aluminum oxide and glass beads preventing mechanical movement that would reduce the thickness of the binding material as it softens. The combination thus prevents the shorting typically encountered with wires that would use only one type of insulator, without the risk of defects in either layer of insulator. Such a combination can also allow an affordable composite solution when the ceramic is a simple anodized aluminum process, coupled with a simple enamel dip, combined with microbeads of glass, ceramic, or other high dielectric hard materials that have suitable spacing. The suitable spacing refers to a size that will maintain the spacing between layers of metal 1510 that would be required to prevent shorting even when conducting voltages expected for a given application.
It will be understood that conductor 1500 can have many variables, depending on the intended application. For example, ceramic insulator 1520 can have variations in relative thickness based on the voltages of the application. Additionally, or alternatively, the ratio of beads 1540 (or a hard powder) to binder material for hybrid layer 1542 can be tailored to the desired application, with thicker insulation for higher voltages.
In one embodiment, conductor 1500 uses flat copper wire coated with a hybrid of inert non-conductive filler or spacer material such as glass beads or aluminum oxide powder. In one such example, conductor 1500 includes metal 1510 and no separate ceramic insulator 1520. Rather, the ceramic can be entirely applied in the form of beads 1540 within flexible insulator 1530. Such an application would provide wire that performs equivalently to traditional magnet wire, which is hardier and less prone to shorting, arcing, or burning out. In one embodiment, metal 1510 can be aluminum, with ceramic insulator 1520. Alternatively, a ceramic coating can be applied to copper wire.
In accordance with diagram 1610, the traditional wire has conductor 1612 with insulator 1614. Insulator 1614 can be thin to make the traditional wire a magnet wire winding. Traditionally, the winding of diagram 1610 may include binding materials between the individual wires, which is not explicitly shown, but which would occupy some or all of the empty space between the wires. Thus, a bundle of traditional magnet wire can be fused into a single mechanical mass by heating or baking the assembly once it is wound or formed.
Despite the use of bindings to create a solid mass of a winding assembly, such devices are subject to burnout for the same reasons identified above with respect to traditional wire assemblies. Namely, the use of the binding tends to trap heat in the wiring as the device is cycled over and over, increasing the temperature. For binding materials that are soft enough to penetrate to most space between the wires, the binding material tends to soften at high temperatures, resulting in vibration pressure against the wires, which can cause electrical shorting. Binding material that can withstand higher temperatures may not provide as much gap coverage, and may still allow enough vibration pressure to allow failures. Regardless, if the binding material is not able to entirely fill the gaps in the wiring, there is more likelihood that adjacent wires can vibrate against each other, resulting in the failures mentioned previously.
It will be understood that even the application of beads in a composite coating of hard coating and flexible coating as mentioned above for conductor 1500, with round wires the beads would tend to be displaced. An electrical short with the round wires only requires a point on the circumference of one wire to be electrically close enough to a point on the circumference of another wire. The use of beads may make such an occurrence less likely. Thus, the use of a hard insulator and a soft insulator with beads could be applied to round wire such as that of diagram 1610. However, it is expected that the failure rate of such an application would still be significantly higher than that of a rectangular conductor.
In accordance with diagram 1620, the hybrid packed conductor has a type of wire that is square, rectangular, ribbon, or flat with a hard insulator coating directly in contact with the metal and a flexible insulator coating surrounding the hard insulator coating. Thus, conductor 1622 represents a metal wire or other conductor wire having an increased exposed surface area relative to conductor 1612 of diagram 1610. Increasing the exposed surface area means that conductors 1622 mechanically have lower contact pressure relative to conductor 1612, because the same forces are spread over a much greater area as compare to two round wires. Additionally, relative to diagram 1610, diagram 1620 has more conductor in the same area, which provides denser packing to allow more current flow, which will increase the magnetic flux of the stator. The increase in conductor and improved resistance to burnout provide better performance of the wrappings, even if the wire assembly is made without packing material as previously done.
Thus, diagram 1620 provides a wrapping with a hybrid insulation layer on the conductors that provides higher temperature, stronger and more durable insulation for electrical wiring for motors and other electromagnetic applications. Hybrid insulator 1626 represents the hybrid insulation layer, which can be in contact with hard insulator 1624. The conductor bundle of diagram 1620 has almost ideal packing density, very high thermal transport characteristics, and good electrical insulation characteristics. For applications where abrasion, force, temperature, and environmental factors can cause wiring to fail, the wrapping of diagram 1620 has many advantages over the traditional coated wire wrapping of diagram 1610. The hybrid insulation is minimal compared to bulky and expensive solutions, and is relatively inexpensive to apply.
Hard insulator 1624 may still be susceptible to minor cracking due to bending, stress, and thermal expansion. Traditional soft insulator could still expose such defects for the same reasons that the bending, stress, and thermal expansion will introduce stress that can compress and displace the soft insulator material. However, hybrid insulator 1626 with beads, which may include a powder, such minor cracking does not produce a failure mechanism. The beads will maintain sufficient electrical distance between layers. The nature of the beads may even cause them to collect in areas of cracking, due to the disruption or imperfection in the crystalline surface structure. Collection of beads in cracks would ensure that cracks are not expose to cracks in adjacent layers, because the beads will maintain the electrical distance between the layers, preventing shorting.
Stator 1700 includes core 1710, which can be a solid metal core, such as an iron core or a steel core. The view in the diagram is a cross-section view of stator 1700. Stator core 1710 includes laminations 1720 that extend radially out from center 1712. More specifically, considering the cross-section of stator 1700 as a circle with the center at center 1712, laminations 1720 extend out along a radius of the circle.
Laminations 1720 act as posts around which conductor can be wrapped. In one embodiment, laminations 1720 are wrapped with hybrid coated conductor 1730 in accordance with any hybrid conductor described. More specifically, hybrid coated conductor 1730 includes a conductive core such as metal, a hard insulator coating on the conductive core, and a soft insulator coating on the hard insulator coating. In one embodiment, the soft insulator coating includes beads, as ceramic or glass balls or spheres, or powder. In one embodiment, the beads are part of the material used to make the soft insulator coating. In one embodiment, the soft insulator coating is created, and then beads are applied to the coating. In one embodiment, the soft insulator coating includes multiple soft layers, which could be multiple layers of the same material, or layers of different material.
A motor that applies stator 1700 can run hotter without failing. Stator 1700 can allow a motor to be driven harder with more current, providing greater torque in a smaller package. Motors are typically sized for the peak power requirements, even if the peak only lasts a few seconds. With the ability to overdrive the motor based on the use of stator 1700, the motor can be designed to nominal power requirements, allowing the peak power to be obtained with momentary surges in power. The momentary surges would not risk failure because of the thermal performance and the electrical separation of hybrid coated conductors 1730. Motors that can run at higher temperature can have greater power densities, lower weight, lower cost, and greater performance. In some applications, a motor in accordance with stator 1700 can reduce cooling systems that would otherwise add weight, cost, and complexity to the total system.
Stator 1800 includes core 1810, which can be a solid metal core, such as an iron core or a steel core. The diagram includes a top view of stator 1800 on the left and a side view of the stator on the right. Core 1810 includes center 1812. In one embodiment, core 1810 is a disk of magnetic metal. In one embodiment, core 1810 is an iron disk. Core 1810 includes multiple slots or posts that radially surround center 1812. More specifically, considering the top view of stator 1800 as a circle with the center at center 1812, slots 1820 are centered on radius lines of the circle, with one end of the slot toward center 1812, and the other end toward an outer edge of stator 1800.
Slots 1820 act as posts around which conductor can be wrapped. In one embodiment, slots 1820 are wrapped with hybrid coated conductor 1830 in accordance with any hybrid conductor described. More specifically, hybrid coated conductor 1830 includes a conductive core such as metal, a hard insulator coating on the conductive core, and a soft insulator coating on the hard insulator coating. In one embodiment, the soft insulator coating includes beads, as ceramic or glass balls or spheres, or powder. In one embodiment, the beads are part of the material used to make the soft insulator coating. In one embodiment, the soft insulator coating is created, and then beads are applied to the coating. In one embodiment, the soft insulator coating includes multiple soft layers, which could be multiple layers of the same material, or layers of different material.
A motor that applies stator 1800 can run hotter without failing. Stator 1800 can allow a motor to be driven harder with more current, providing greater torque in a smaller package. Motors are typically sized for the peak power requirements, even if the peak only lasts a few seconds. With the ability to overdrive the motor based on the use of stator 1800, the motor can be designed to nominal power requirements, allowing the peak power to be obtained with momentary surges in power. The momentary surges would not risk failure because of the thermal performance and the electrical separation of hybrid coated conductors 1830. Motors that can run at higher temperature can have greater power densities, lower weight, lower cost, and greater performance. In some applications, a motor in accordance with stator 1800 can reduce cooling systems that would otherwise add weight, cost, and complexity to the total system.
Stator 1700 of
In one aspect, a stator assembly includes: a magnet assembly having magnets in a first plane in a radial pattern around a stator center point; and a stator core adjacent the magnet assembly, the stator core having a stack of multiple layers of coated conductor, wherein the conductor has a rectangular cross section, with an insulative coating chemically bonded to the conductor.
In one embodiment, the rectangular cross section varies from a smaller area at a point closer to the stator center point to a larger area at a point farther from the stator center point. In one embodiment, the conductor comprises patterned sheet metal. In one embodiment, the conductor comprises aluminum and the coating comprises sapphire. In one embodiment, the conductor comprises copper and the coating comprises diamond. In one embodiment, a layer of conductor includes multiple spokes, with a spoke electrically coupled proximate the stator center point to an adjacent spoke of the layer, and electrically coupled proximate a stator outer edge to a different adjacent spoke of the layer. In one embodiment, the stator having a plurality of stacks of multiple layers of coated conductor. In one embodiment, the plurality of stacks comprises a first stack to nest with a second stack, wherein spokes of the first stack interleave adjacent to and substantially coplanar with spokes of the second stack. In one embodiment, the plurality of stacks comprises a first stack having a first phase, and a second stack having a second phase different from the first phase. In one embodiment, the spokes include multiple parallel current paths aligned orthogonal to motion of magnetic poles of the first and second magnet assemblies. In one embodiment, the multiple parallel current paths of the spokes join to a single current path to electrically couple proximate the stator center point and join to a single current path to electrically couple proximate the stator outer edge. In one embodiment, the multiple layers of conductor comprise coils of metal in a serpentine shape where the coils fold over each other. In one embodiment, at least two of the layers of conductor are connected in parallel. In one embodiment, at least two of the layers of conductor are connected in series. In one embodiment, the magnet assembly comprises a first magnet assembly, and further comprising: a second magnet assembly having magnets in a second plane parallel to the first plane in a radial pattern around the stator center point; wherein the stator core is between the first and second magnet assemblies.
In one aspect, a motor assembly includes: a motor housing; a rotor; a shaft; and a stator assembly including a first magnet assembly having magnets in a first plane in a radial pattern around a stator center point; a second magnet assembly having magnets in a second plane parallel to the first plane in a radial pattern around the stator center point; and a stator core between the first and second magnet assemblies, the stator core having a stack of multiple layers of coated conductor, wherein the conductor has a rectangular cross section, with an insulative coating chemically bonded to the conductor.
In one embodiment, a layer of conductor includes multiple spokes, with a spoke electrically coupled proximate the stator center point to an adjacent spoke of the layer, and electrically coupled proximate a stator outer edge to a different adjacent spoke of the layer, and wherein the conductor comprises aluminum and the coating comprises sapphire. In one embodiment, the motor assembly comprises a linear motor. In one embodiment, further comprising: a mechanical mounting to couple the stator assembly to the shaft, where the rotor rotates freely around the shaft, wherein adjacent layers of the stator core connect proximate the stator center to each other. In one embodiment, the motor assembly comprises a motor of an in wheel motor. In one embodiment, further comprising: a mechanical mounting to couple the stator assembly to the motor housing, where the rotor is fixed to the shaft, wherein adjacent layers of the stator core connect proximate a stator outer edge to each other. In one embodiment, the rectangular cross section varies from a smaller area at a point closer to the stator center point to a larger area at a point farther from the stator center point. In one embodiment, the conductor comprises patterned sheet metal. In one embodiment, the conductor comprises aluminum and the coating comprises sapphire. In one embodiment, the conductor comprises copper and the coating comprises diamond. In one embodiment, a layer of conductor includes multiple spokes, with a spoke electrically coupled proximate the stator center point to an adjacent spoke of the layer, and electrically coupled proximate a stator outer edge to a different adjacent spoke of the layer. In one embodiment, the stator having a plurality of stacks of multiple layers of coated conductor. In one embodiment, the plurality of stacks comprises a first stack to nest with a second stack, wherein spokes of the first stack interleave adjacent to and substantially coplanar with spokes of the second stack. In one embodiment, the plurality of stacks comprises a first stack having a first phase, and a second stack having a second phase different from the first phase. In one embodiment, the spokes include multiple parallel current paths aligned orthogonal to motion of magnetic poles of the first and second magnet assemblies. In one embodiment, the multiple parallel current paths of the spokes join to a single current path to electrically couple proximate the stator center point and join to a single current path to electrically couple proximate the stator outer edge. In one embodiment, the multiple layers of conductor comprise coils of metal in a serpentine shape where the coils fold over each other. In one embodiment, at least two of the layers of conductor are connected in parallel. In one embodiment, at least two of the layers of conductor are connected in series. In one embodiment, the magnet assembly comprises a first magnet assembly, and further comprising: a second magnet assembly having magnets in a second plane parallel to the first plane in a radial pattern around the stator center point; wherein the stator core is between the first and second magnet assemblies.
In one aspect, a stator assembly includes: a stator core having slots radially around a center of the stator core; and a coated conductor wrapped around a slot, wherein the coated conductor includes a metal having a generally rectangular cross-section; a ceramic coating bonded to the metal; and a non-ceramic insulative coating over the ceramic coating, including non-conductive beads embedded in the non-ceramic insulative coating.
In one embodiment, the stator core comprises an iron core with slots extending away from the center of the stator core. In one embodiment, the stator core comprises an iron disk with slots on a surface of the iron disk. In one embodiment, the metal comprises copper or aluminum. In one embodiment, the ceramic coating bonded to the metal comprises ceramic coating chemically bonded to the metal. In one embodiment, the ceramic coating comprises metal oxide. In one embodiment, the ceramic coating comprises an oxide of the metal of the coated conductor. In one embodiment, the non-ceramic insulative coating comprises epoxy. In one embodiment, the non-ceramic insulative coating comprises plastic. In one embodiment, the beads comprise glass balls. In one embodiment, the beads comprise ceramic powder. In one embodiment, the beads comprise aluminum oxide powder.
In one aspect, motor assembly includes: a motor housing; a rotor; a shaft; and a stator assembly including a magnet assembly having magnets around the stator assembly; and a stator core with a coated conductor wrapped around a slot of the stator core, the coated conductor including: a metal having a generally rectangular cross-section; a ceramic coating chemically bonded to the metal; and a non-ceramic insulative coating over the ceramic coating, including non-conductive beads embedded in the non-ceramic insulative coating.
In one embodiment, the metal comprises copper or aluminum. In one embodiment, the ceramic coating comprises metal oxide. In one embodiment, the non-ceramic insulative coating comprises epoxy or plastic. In one embodiment, the beads comprise one of: glass balls, ceramic powder, or aluminum oxide powder. In one embodiment, the motor assembly comprises a linear motor. In one embodiment, the motor assembly includes: a mechanical mounting to couple the stator assembly to the shaft, where the rotor rotates freely around the shaft, wherein adjacent layers of the stator core connect to each other proximate a center of the stator core. In one embodiment, the motor assembly includes: a mechanical mounting to couple the stator assembly to the motor housing, where the rotor is fixed to the shaft, wherein adjacent layers of the stator core connect proximate a stator outer edge to each other.
Besides what is described herein, various modifications can be made to the disclosed embodiments and implementations of the invention without departing from their scope. Therefore, the illustrations and examples herein should be construed in an illustrative, and not a restrictive sense. The scope of the invention should be measured solely by reference to the claims that follow.
This application is a Continuation-in-Part of U.S. patent application Ser. No. 15/612,886, filed Jun. 2, 2017, entitled, “STATOR ASSEMBLY WITH STACK OF COATED CONDUCTORS”, now U.S. Pat. No. 10,778,049, and claims the benefit of priority of that application. The present application also claims the benefit of priority of U.S. Provisional Application No. 62/346,898, filed Jun. 7, 2016.
| Number | Date | Country | |
|---|---|---|---|
| 62346898 | Jun 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15612886 | Jun 2017 | US |
| Child | 17019124 | US |
