PCB-based stranded, twisted excitation windings in rotary transformers

Abstract

Embodiments of the disclosure provide a rotary transformer (RT) comprising a printed circuit board (PCB) and a set of secondary windings integrated with the PCB. The set of secondary windings includes multiple conductor tracks extending over a first region of the PCB and a second region of the PCB. The multiple conductor tracks are organized in a first positional order in the first region of the PCB. The multiple conductor tracks are organized in a second positional order in the second region of the PCB.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of an earlier filing date from U.S. Provisional Application Serial No. 63 / 333,790, filed April 22, 2022, the entire disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION

[0002] A wound-rotor synchronous machine (WRSM) is an electric motor with a rotor and a stator. The stator is the stationary part of the machine, and the rotor is the rotating part. The stator typically has a multi-phase winding, and the rotor is made with a field winding instead of permanent magnets. The rotor rotates in a magnetic field, and the magnetic field can be generated by the windings or field coils. A field coil is an electromagnet used to generate a magnetic field in an electromagnetic machine, usually a rotating electrical machine such as a motor or generator. It contains a coil of wire through which a current flows. In the case of a machine with field coils, a current must flow in the coils to generate the field; otherwise, no power is transferred to or from the rotor.The process of generating a magnetic field using an electric current is called excitation. Field coils offer the most flexible form of magnetic flux regulation and deregulation, but at the expense of an electric current flow.

[0003] Typically, the rotor windings of a WRSM can be energized or excited using slip ring and brush assembly systems. However, slip ring and brush assembly systems have disadvantages, including inefficiency at high speeds, requiring frequent maintenance, and overall loss due to the high contact resistance between the brush and the slip ring, especially at high speeds.

[0004] To avoid the disadvantages of slip-ring and brush excitation methods, wireless (or contactless) excitation or wireless power transmission systems have been developed. Generally, wireless power transmission uses various technologies to transfer energy using electromagnetic fields (EMFs) without a physical connection. In a wireless power transmission system, a transmitter device, driven by electrical power from a power source, generates a time-varying EMF that transfers power via mutual inductance (M) across a space to a receiver device. The receiver device uses M to extract power from the EMF and deliver the extracted power to an electrical load. Wireless power transmission provides power to electrical devices when interconnecting wires are impractical, dangerous, or not possible.Wireless power delivery technologies primarily fall into two categories: near-field and far-field. In near-field technologies, the time-varying EMF is generated using a variety of techniques that include resonant inductive coupling. Resonant inductive coupling is the wireless near-field transfer of electrical energy between magnetically coupled coils that are part of a resonant circuit tuned to oscillate at the same frequency as the drive frequency.

[0005] Rotary transformers (RTs) are a type of wireless power transfer system that can be used for the controlled wireless excitation of the rotor windings of a WRSM. An RT performs the same general function as a conventional transformer, with both transferring electrical power from one circuit to another at the same frequency but at different voltages. A conventional transformer operates on the principle of electromagnetic induction, meaning that the electromotive force is induced in the closed circuit due to the surrounding variable magnetic field. An RT differs from a conventional transformer in that the RT geometry is arranged so that the primary and secondary windings can be rotated with respect to each other, with negligible changes in the electrical properties.In one common configuration, the RT can be constructed by winding the primary and secondary windings into separate halves of a cap core. The concentric halves face each other, with each half mounted on one of the parts that rotates relative to each other. Magnetic flux provides the coupling from one half of the cup core to the other across an air gap, thereby providing the "M" that transfers energy from the RT's primary windings to its secondary windings.

[0006] Known methods of using RT systems to provide excitation for a WRSM may include a resonant tuning network, also called a compensation network. A resonant tuning network may include circuit components (e.g., various combinations of resistors, inductors, and / or capacitors) that allow the associated transformer to store oscillating electrical energy similar to a tank circuit, thus acting as a bandpass filter, passing frequencies near their resonant frequency from the primary to the secondary winding while blocking other frequencies. The magnitude of M between the primary and secondary windings, along with the quality factor (Q-factor) of the circuit, determines the shape of the frequency response curve.Resonant circuits are often referred to as LC or LRC resonant circuits because of the inductive (L), resistive (R), and capacitive (C) components used to form the resonant circuit. In materials science, every material has its own natural frequency. When the external vibration equals the natural frequency, resonance occurs. In electrical engineering, the impedance of inductors and capacitors depends on frequency. Capacitive impedance is inversely proportional to frequency, while inductive impedance is directly proportional to frequency. At a certain frequency, the two cancel each other out. Such a circuit is called a resonant circuit, and this particular frequency is the resonant frequency.

[0007] In conventional RT systems, the resonant tuning network (or compensation network) is provided on the stationary (or stator or primary) side and the rotating (or rotor or secondary) side of the WRSM. For the primary coil, a basic function of "compensation" is to minimize the input apparent power and / or minimize the voltage-ampere rating (VA) of the network. For the secondary coil, compensation cancels the secondary coil's stray inductance to maximize the transmission capability.

[0008] In general, electric motors can be relatively complex structures with parts that rotate at high speeds and generate high temperatures. Additionally, the use of various forms of electromotive force (EMF), complex communication signals, radio-frequency (RF) communication signals, complex motor control processes, and the like can further increase complexity. Furthermore, for many applications, the size and weight of the motor must be controlled. Therefore, it makes sense to develop motor designs that prioritize compact dimensions, reduced costs, simple electrical, mechanical, and thermal design, reduced eddy current losses, and an improved method for providing PCB-based windings that can effectively and efficiently handle RF communication signals. BRIEF DESCRIPTION OF THE INVENTION

[0009] Embodiments of the disclosure provide a rotary transformer (RT) including a printed circuit board (PCB) and a set of secondary windings integrated with the PCB. The set of secondary windings includes a plurality of conductive traces spanning a first region of the PCB and a second region of the PCB. The plurality of conductive traces are organized in a first positional order in the first region of the PCB. The plurality of conductive traces are organized in a second positional order in the second region of the PCB.

[0010] Embodiments of the disclosure provide a method for forming an RT including a printed circuit board (PCB) and a set of secondary windings integrated with the PCB. The set of secondary windings includes a plurality of conductive traces spanning a first region of the PCB and a second region of the PCB. The plurality of conductive traces are organized in a first positional order in the first region of the PCB. The plurality of conductive traces are organized in a second positional order in the second region of the PCB. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a simplified block diagram illustrating a non-limiting example of an electric drive motor system with integrated power electronics in accordance with aspects of the disclosure; Fig. 2 is a simplified block diagram illustrating a three-dimensional (3D) view and a front view of a non-limiting example of how a portion of a rotating side of an electric machine may be configured to include integrated power electronics in accordance with aspects of the disclosure; Fig. 3 presents equations in accordance with aspects of the disclosure; Fig. 4 is a simplified block diagram illustrating a non-limiting example of a portion of an RT in accordance with aspects of the disclosure; Fig. 5 illustrates optimization equations in accordance with aspects of the disclosure; Fig. 6A depicts a simplified block diagram illustrating a multi-stranded conductive path in accordance with aspects of the disclosure; Fig. 6B depicts a simplified block diagram illustrating a multi-stranded conductive path in accordance with aspects of the disclosure; Fig. 6C depicts a simplified block diagram illustrating a multi-stranded conductive path in accordance with aspects of the disclosure; Fig. Figure 7A shows a PCB with untwisted turns; Fig. 7B illustrates a twisted strand PCB in accordance with aspects of the disclosure; Fig. 8A depicts a simplified block diagram illustrating full twist in accordance with aspects of the disclosure; Fig. 8B depicts a simplified block diagram illustrating partial twisting in accordance with aspects of the disclosure; Fig. 9 illustrates a twisted strand PCB in accordance with aspects of the disclosure; Fig. 10 is a simplified block diagram illustrating a non-limiting example of how layer-to-layer twisting may be implemented using via structures in accordance with aspects of the disclosure; and Fig. 11 is a simplified block diagram illustrating a computer system operable to implement embodiments of the disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the disclosure provide a novel integrated power electronics system that can be used in an electric motor drive system with a wireless power transfer (or RT) network. The electric motor drive system can include an electric motor (e.g., a WRSM) with a stationary side and a rotating side. In embodiments of the disclosure, the integrated power electronics system can be implemented as an integrated mounting and / or communication structure, wherein selected portions of the motor and / or the wireless power transfer system can be integrated to provide improved physical support, improved electronic communication, and improved cooling.On the rotating side, an example of the integrated mounting and / or communication structure can be used to integrate secondary windings; elements on the rotating side of the RT (if any); a rectifier; and various electronic connections between the secondary windings, the elements on the rotating side of the RT, and the rectifier. On the stationary side, an example of the integrated mounting and / or communication structure can be used to integrate an inverter; elements on the stationary side of the RT; primary windings; and various electronic connections between the inverter, the elements on the stationary side of the RT, and the primary windings.

[0012] In some embodiments of the disclosure, the integrated mounting and / or communication structure may be implemented as a multilayer printed circuit board (PCB) operable to incorporate, within its layers, primary windings, secondary windings, transistors (e.g., for the inverter), diodes (e.g., for the rectifier), wiring, and the like. On the rotating side, where cooling is required, the PCB may incorporate an assembly area operable to incorporate certain components (e.g., diodes for the rectifier) ​​and cooling mechanisms for the incorporated components.

[0013] The PCB-based secondary windings have similarities to other PCB-based, stationary planar inductor or transformer designs. However, the PCB-based secondary windings of an RT have two distinct features compared to the stationary planar transformer. In particular, the primary core must have a significantly large gap to accommodate the secondary PCB structure; and the primary and secondary windings are physically separated, meaning that the commonly used interleaving among the primary and secondary windings is not feasible for RT PCB-based applications. Therefore, the conventional design of multi-strand PCB-based windings causes significantly high loss in the RT application. In embodiments of the disclosure, an optimized multi-strand PCB-based winding design and optimization method are proposed to minimize loss and temperature rise.

[0014] Therefore, the integrated mounting and / or communication structures (e.g., a PCB) and / or the optimized multi-strand PCB-based winding design and optimization method described herein provide technical advantages and technical effects. The secondary windings and the rectifier subsystems are assembled in the same PCB structure, significantly simplifying the design, prototyping, and production of the associated RT. Embodiments of the disclosure also reduce or eliminate the difficulties in terminations and interconnections between the rectifier and the secondary winding assemblies. Embodiments of the disclosure further enable the assembly area (e.g., the assembly area housing the rectifier's diodes) to be mounted directly to the motor shaft using, for example, an aluminum support sleeve, which provides high mechanical robustness and easier thermal management.Therefore, in accordance with aspects of the disclosure, the integrated mounting and communication structure enables motor designs that prioritize compact size; reduced cost; simplicity in electrical, mechanical, and thermal design; reduced eddy current losses; and the ability to efficiently and effectively process RF communication signals.

[0015] Turning now to a more detailed description of embodiments of the disclosure, Fig. 1 illustrates a system 100 embodying aspects of the disclosure. The system 100 includes a power source 110 electronically coupled to an electric motor drive system 102. The electronic motor drive system 102 includes an inverter / RT system 120, a DC-excited motor 140, and a controller 170 configured and arranged as shown. In accordance with aspects of the disclosure, the inverter / RT system 120 includes an integrated mounting and communication structure 160 operable to be integrated with an inverter system 122; an RT system 124; electrical connectors 128 operable to electrically couple the inverter system 122 to the RT system 124; primary windings 126; and electrical connectors 130 operable to electrically couple the RT system 124 to the primary windings 126.In accordance with aspects of the disclosure, the DC-excited motor 140 includes an integrated mounting and communication structure 162 operable to integrate secondary windings 146; a rectifier system 142; and electrical connectors 150 operable to electrically couple the secondary windings 146 to the rectifier system 142. Although the inverter / RT system 120, the DC-excited motor 140, and the control unit 170 are illustrated as separate components, it is understood that the inverter / RT system 120, the DC-excited motor 140, and the control unit 170 may be configured and arranged in any suitable combination. For example, the control unit 170 may be incorporated into the inverter / RT system 120; the inverter / RT system 120 may be incorporated into the DC-excited motor 140; and / or the inverter / RT system 120 and the control unit 170 may be incorporated into the DC-excited motor 140.In addition, the system 100 includes a stationary side (e.g., stator side) 220 and a rotating side (e.g., a rotor side) 230. In general, the stationary side 220 includes the primary windings 126 and the circuit elements to its left, and the rotating side 230 includes the secondary windings 146 and the circuit elements to its right.

[0016] The energy source 110 can be implemented in various ways, including, for example, a battery. In some embodiments of the disclosure, the battery can be a battery pack having a set of one or more individual battery cells connected in series or parallel, operating under the control of one or more control units, such as a battery control module (BCM), that monitors and controls the performance of the battery pack. The BCM can monitor several battery pack-level properties, such as pack current, measured by a current sensor, pack voltage, and pack temperature, for example. The battery pack can be recharged from an external power source (not shown). The battery pack can include power conversion electronics operable to condition the power from the external power source to provide the proper voltage and current values ​​for the battery pack.The individual battery cells in a battery pack can be constructed from a variety of chemical formulations. Battery pack chemicals include, but are not limited to, lead acid, nickel cadmium (NiCd), nickel metal hydride (NIMH), lithium-ion, or lithium-ion polymer.

[0017] The inverter 122 may be a resonant inverter 122 electrically coupled between the power source 110 and the DC-excited motor 140 to transfer excitation energy from the power source 110 through the RT system 124 and the primary windings 126 to the DC-excited motor 140. In particular, the resonant inverter 122 is operable to provide energy from the power source 110 to the RT system 124 at a desired resonant frequency to provide excitation through the primary windings 126 to the DC-excited motor 140. In embodiments of the disclosure, the resonant inverter 122 is operable to convert the DC voltage from the power source 110 to an AC current at the desired resonant frequency as required by the AC-excited motor 140 and the RT system 124 for motor excitation.In embodiments of the disclosure, the resonant inverter 122 may be a resonant full-bridge inverter with four switches organized as two "phase legs." Each phase leg may include two switches connected in series between a positive DC rail and a negative DC rail. A phase node may be positioned between the two switches of each phase leg to provide the phases of an AC waveform output at a desired resonant frequency. In some embodiments of the disclosure, the resonant inverter 122 generates RF AC power. The controller 170 is electronically coupled to the phase leg switches to control the on / off states of the switches and thereby control the frequency and phase of the AC waveform generated by the resonant inverter 122.The control unit 170 includes a computing device that includes a computer or a microprocessor configured and operable to execute software instructions and programs, and may include associated firmware, such that the control unit is configured and operable to control the on / off switching operations of the resonant inverter 122. In embodiments of the disclosure, the control unit 170 may be configured and arranged to implement the features and functionality of the computing system 1100 (in . Fig. 11). The control unit 170 is also configured to send various control commands to the DC-excited motor 140, for example, to control the torque and / or speed of the motor 140.

[0018] The DC motor 140 can be any electric motor design suitable for the work the motor is required to perform. Examples of work that can be performed by motors in conventional automotive-based motor applications include operating or moving power windows; power seats; fans for the heater and radiator; windshield wipers; and / or the engine of a vehicle with a hybrid electric vehicle configuration. Regardless of the type of DC motor 140, it relies on electromagnetism and reversing magnetic fields to generate mechanical energy. A conventional implementation of the DC motor 140 includes five basic parts: a stator, a rotor, a solid axle, coils, and a squirrel cage.The stator winding in a DC motor is a ring of electromagnets that are paired and energized one after the other, creating the rotating magnetic field. The rotor in a DC motor has no direct connection to a power source and no brushes. Instead, it often uses the squirrel cage rotor described earlier. The squirrel cage rotor in a DC motor is a set of rotor bars connected to two rings, one at each end. The squirrel cage rotor goes into the stator. When excitation power is sent through the stator, it generates an EMF. The squirrel cage bars are conductors and therefore respond to the reversal of the stator's poles, causing the rotor to rotate and generate its own magnetic field. The key to an induction motor, where the rotor's field is induced by the stator's field, is that the rotor is always trying to catch up.It's always searching for stasis, so it rotates to reach that steady state. However, the EMF generated by the stator will always be slightly faster than the rotor's field. The rotor's rotation creates the torque needed to generate the mechanical power to turn a car's wheels or a fan's blades. Some DC motors use a wound rotor (e.g., a WRSM) wrapped with wire rather than a squirrel cage. In any case, there is only one moving part in a DC motor, meaning there are fewer elements to replace or maintain.

[0019] As mentioned, in some embodiments of the disclosure, the DC-excited motor 140 may be a WRSM. A WRSM is a rotating electric motor with a rotor and a stator. The stator is the stationary part of the machine, and the rotor is the rotating part of the machine. The stator typically has a multi-phase winding, and the rotor is equipped with a field winding instead of permanent magnets. The rotor rotates in a magnetic field, and the magnetic field can be generated by the windings or field coils. In a machine with field coils, an excitation current must flow in the windings to generate the field; otherwise, no power is transferred to or from the rotor. Field coils provide the most flexible form of magnetic flux regulation and deregulation, but at the expense of current flow. Conventionally, the rotor winding of a WRSM can be powered or excited using a slip ring and brush assembly.However, slip ring and brush assembly systems have disadvantages, including being inefficient at high speeds, requiring frequent maintenance, and overall lossy due to the high contact resistance between the brush and slip ring systems, especially at high speeds.

[0020] To avoid the shortcomings of slip ring and brush assembly excitation methods, the RT compensation system 124, primary windings 126, and secondary windings 146 are operable to provide wireless excitation or wireless power transfer from the stationary side 220 to the rotating side 230. The secondary windings 146 are located close enough to the primary windings 126 to be within an EMF generated by the primary windings 126, so that M is present between the primary windings 126 and the secondary windings 146. The secondary windings use M to generate an AC charging signal, and the rectifier system 142 converts the AC charging signal to a DC charging signal, which is provided to the rotor (now shown separate from the motor 140).In some embodiments of the disclosure, the RT compensation system 124 may be implemented as a specially designed RT compensation system 124 on the stationary side only. In general, the RT is a circuit and method for wirelessly transferring power to the secondary windings of a WRSM for controlled excitation. An RT is essentially the same as a conventional transformer in that it transfers electrical energy from one circuit to another at the same frequency but different voltage. In general, a conventional transformer operates on the principle of electromagnetic induction, meaning the electromotive force is induced in the closed circuit by the variable magnetic field surrounding it.An RT differs from a conventional transformer in that the geometry of the RT is arranged so that the primary and secondary windings can be rotated with respect to each other with negligible changes in electrical properties. In one common configuration, the RT can be constructed by winding the primary and secondary windings in separate halves of a pot core. The concentric halves face each other, with each half attached to one of the parts that rotate with respect to each other. Magnetic flux provides the coupling of one half of the pot core to the other across an air gap, providing "M" that couples energy from the RT's primary windings to the secondary windings.

[0021] In conventional RT designs, a resonant tuning network (or compensation network) is provided on the stationary (or primary) side and on the rotating (or secondary) side of the WRSM. RT designs that have resonant circuit components on both the stationary and rotating sides of the WRSM are difficult to implement. For example, in practice, it is difficult to place a resonant tuning network or compensation circuit on the secondary side due to the very limited rotor space and the high-temperature operating conditions of the rotor, which exceed the temperature range of commercially available compact capacitors. Furthermore, placing a resonant tuning capacitor on the secondary side increases the complexity of the rotating part, increases mechanical mass, increases inertia, and reduces mechanical reliability, especially at high speeds.

[0022] The implementation of the RT compensation system 124 on the stationary side only addresses the difficulties associated with the actual implementation (i.e., construction and use) of conventional RT designs incorporating double-sided compensation networks by providing the benefits of wireless power transfer without the difficulties associated with providing compensation circuits on a rotating side of a DC-excited motor 140 (e.g., a WFSM). More specifically, the implementation of the RT compensation system 124 on the stationary side only is capable of wirelessly transferring rotor excitation current from the primary windings 126 to the secondary windings 146, thereby eliminating the brush and slip-ring maintenance issues, as well as the inefficiencies, manufacturing problems, and design disadvantages associated with brush and slip-ring systems.

[0023] In aspects of the disclosure, the stationary-side-only implementation of the RT compensation system 124 accounts for the lack of a resonant tuning capacitor on the secondary side by providing an additional resonant tuning capacitor (i.e., one of the resonant tuning capacitors of a stationary-side-only resonant LCC) on the primary side and adjusting the two primary-side resonant tuning capacitors such that the uncompensated secondary side does not impose inefficiencies or other disadvantages on the RT compensation system 124. In embodiments of the disclosure, a stationary-side-only LCC design methodology is provided that includes reflecting the secondary side's impedance and / or inductance to the primary side, and the leakage inductance of these secondary windings 146 is matched to the primary side.In general, a reflected impedance (or inductance) is the portion of the impedance of a circuit (e.g., circuit A) that is due to the influence of another coupled circuit (e.g., circuit B). In embodiments of the disclosure, this can be achieved by deriving equivalent circuit models of system 100 as well as the total impedance model of system 100, allowing the calculation of the reflected impedance from secondary to primary. A further simplification is applied to the derived equivalent circuit models so that the total impedance of resonant converter 122 can be calculated. To tune this total impedance to a unity power factor, a tuning capacitor of the LCC design is recalculated.Thus, when implemented only on the stationary side of the RT compensation system 124, the need for capacitor tuning on the secondary side and the need for a secondary side resonant tuning capacitor(s) and their tuning are eliminated by providing additional primary side tuning components (e.g., a resonant tuning capacitor(s)) and adjusting the values ​​of the tuning components on the primary side.

[0024] Fig. 2-10 illustrate examples of how various embodiments of the disclosure may be designed and manufactured in accordance with aspects of the disclosure. For the sake of brevity, conventional techniques related to making and using aspects of the disclosure may not be described in detail here. In particular, various aspects of fabricating PCBs, electrical components, electronic interconnections, bonding techniques, and the like that may be used to implement the various technical features described herein are well known. Accordingly, in the interest of brevity, many conventional implementation details are only briefly mentioned here or are omitted entirely, without recognizing the well-known system and / or process details.

[0025] In addition, although Fig. 2 on an exemplary implementation of the Fig. 1, the secondary windings 146, the electrical connectors 150 and the rectifier system 142, essentially the same structural and manufacturing options apply to the Fig. 1, the converter system 122, the electrical connectors 128, the RT compensation system 124, the electrical connectors 130, and the primary windings 126.

[0026] Fig. Figure 2 illustrates additional details such as the integrated mounting and communication structure 162, the secondary windings 146, the electrical connectors 150, and the rectifier system 142 (all shown in Fig. 1) may be implemented as integrated winding / rectifier 200 in accordance with aspects of the disclosure. Fig. Figure 2 illustrates a 3D view and a front view of the windings / rectifier 200, which includes a PCB mounting / communication element 210, a PCB-based secondary coil 212, a configuration of diodes 222 arranged as a rectifier circuit, a rectifier assembly 220, and a rotor shaft 224, configured and arranged as shown. In general, a rotor shaft is a central component of an electric motor. The rotor shaft is the support shaft of the laminated core of the rotor and thus transmits the electrically induced torque through a corresponding command from the control unit 170 (in Fig. 1). The PCB mounting / communication element 210 is an exemplary implementation of the integrated mounting and communication structure 162; the PCB-based secondary coil 212 is an exemplary implementation of the secondary windings 146; and the diodes 222 are configured to form a rectifier circuit, which is an exemplary implementation of the rectifier system 142. The PCB mounting / communication element 210 is a multi-layer PCB structure operable to include, in one or more of its layers, the PCB-based secondary coil 212 (with or without a magnetic core) formed as conductive traces, along with some or all of the electrical connectors 150 (shown in Fig. 1). In some embodiments of the disclosure, the rectifier diodes 222 may be incorporated into one or more layers of the PCB mounting / communication element 210. In some embodiments of the disclosure, the rectifier diodes 222 are mounted in a rectifier assembly 220 that is mounted (e.g., by soldering or another suitable bonding mechanism) to an exposed surface of the PCB mounting / communication element 210. In accordance with aspects of the disclosure, the PCB mounting / communication element 210 and the rectifier assembly 220 are physically bonded together to function as a unitary structure that houses the PCB-based secondary coil 212, the rectifier diodes 222, and portions of the electrical connectors 150.In some embodiments of the disclosure, the rectifier assembly 222 may be configured to include suitable thermal management elements operable to dissipate heat generated at the rotating side 230 during operation of the electric motor 140 (in . Fig. 1) is generated.

[0027] In alternative configurations of the windings / rectifier structure 200, the PCB mounting / communication element 210 may be configured and arranged to be physically mounted (e.g., by soldering or another suitable bonding mechanism) to an exposed outer surface of the rectifier assembly 220; and the rectifier assembly 220 may be physically mounted (e.g., by soldering or another suitable bonding mechanism) to an exposed outer surface of the rotor shaft 224. In another alternative configuration of the windings / rectifier structure 200, the PCB mounting / communication element 210 may be configured and arranged to be physically mounted (e.g., by soldering or another suitable bonding mechanism) to an exposed outer surface of the rotor shaft 224; and the rectifier assembly 220 may also be physically mounted (e.g.,by soldering or another suitable bonding mechanism) to an exposed outer surface of the rotor shaft 224. In some embodiments of the disclosure, the rectifier assembly 220 is also physically mounted (e.g., by soldering or another suitable bonding mechanism) to an exposed surface of the PCB mounting / communication element 210.

[0028] The PCB-based secondary windings 212 share similarities with other PCB-based, stationary, planar inductor or transformer designs. However, the PCB-based secondary windings of an RT have two distinctive features compared to the stationary planar transformer. Specifically, the primary core must have a significantly large gap to accommodate the secondary PCB structure; and the primary and secondary windings are physically separated, meaning that the conventionally used interleaving of the primary and secondary windings is not feasible for RT PCB-based applications. Therefore, the common design of multi-strand PCB-based windings results in significantly high loss in the RT application. Fig. 3-10 present an optimized multi-strand PCB-based winding design and optimization method that are functional to minimize loss and temperature rise.

[0029] Common PCB-based secondary winding configurations for RT applications exhibit high copper losses due to skin effects (current displacement effects), proximity effects, and eddy current losses. A large gap in the ferrite core causes significantly high leakage fluxes, further increasing losses and leading to temperature rises in the PCB. Dividing the copper winding tracks into multiple parallel paths reduces the skin effect and eddy current loss. However, the conventional winding design, which uses parallel tracks, results in unbalanced inductances between the twisted current paths, causing unbalanced losses and thermal hotspots in the PCB.

[0030] At HF, the current in the winding conductors tends to concentrate near the outer boundaries of the conductor, which is known as the skin effect. The skin effect is characterized by the skin depth, which is given by Equation 1 (shown in Fig. 3) where ρ is the electrical resistance of the material, f is the operating frequency, and µ is the magnetic permeability of the material. If the skin depth is much smaller than the conductor size, then the effective resistance of the conductor becomes high due to current displacement near its outer limits, causing high losses. Copper is widely used as a winding material in winding designs, including PCB-based winding constructions. Considering the conventional engineering limitations, RTs are usually operated at operating frequencies between about 20 kHz and 100 kHz. From Equation-1 (in Fig. 3) it can be seen that the skin depth of copper is approximately 0.206 mm at about 100 kHz and approximately 0.461 mm at about 20 kHz. To significantly reduce the skin effect, the width and thickness of the conductor should be less than twice the skin depth 2δ. Therefore, in a stranded conductor, each of the copper strands should be narrow and thin enough to reduce the skin effect. For example, at about 100 kHz, the thickness and width of the copper winding / conductor track should be less than about 0.4 mm.

[0031] A gap (e.g. gap 434 in Fig. 4) is in the core (e.g. core 432 in Fig. 4) of a section of an RT (e.g. 400 in Fig. 4). The gap is large enough to accommodate the thickness of a rotating PCB and the gaps (i.e., air gaps) between the PCB and the ferrite core for free rotation. The gap can be calculated using Equation-2 (in Fig. 3), where tpcb the thickness of the PCB and t air The gap between the PCB and the core is assumed to be essentially the same on both sides of the PCB. A significantly higher circulating current occurs on the conductors near the gap due to the higher leakage flux. From a magnetic point of view, therefore, a lower r g a lower flux leakage and thus lower eddy current losses in the PCB. From a mechanical perspective, however, a minimum PCB thickness is required to operate the PCB at high speeds, which can reach up to 25,000 revolutions per minute (rpm) or even higher. Likewise, a minimum air gap between the PCB and the core is required to maintain the required clearance, taking into account vibration, manufacturability, assembly tolerance, and high-speed deformation of the PCB. The gap t gTypically ranges from about 3 mm to about 10 mm, depending on the PCB material, operating speed, mechanical tolerances, operating temperature, and the like. With such a magnetic gap, the leakage flux near the air gap can be significantly higher, and the PCB winding traces would need to be designed and optimized accordingly to minimize eddy current. Embodiments of the disclosure, design methodologies, and resulting structures for the thickness, width, and positions of individual traces are optimized to minimize eddy current, loss, and temperature rise in the PCB.

[0032] Fig. Figure 7A shows an example of a PCB 710 with untwisted windings of 6 turns (T1, T2, T3, T4, T5, T6) with unbalanced induction between two strands (strand-1 and strand-2). Fig. 7A, it can be observed that due to the smaller radius of strand-1 on each turn, the total length of strand-1 is shorter than that of strand-2. Therefore, the resistance and inductance of strand-1 are lower than those of strand-2. Thus, the total current of the turns is unevenly distributed between strand-1 and strand-2, with strand-1 carrying a higher current than strand-2. Consequently, the loss and temperature of strand-1 are higher than those of strand-2. This phenomenon worsens as the number of strands per turn increases, resulting in larger differences between the radius of the outer strands compared to the inner strands.

[0033] In embodiments of the disclosure, a strand-shaped twisted winding is disclosed to balance the mean length per strand (MLS) and current among the strands of the windings. Each of the strands is designed to minimize loss and maximum temperature in the PCB-based coil windings. The proposed design and optimization method minimizes the skin effect, the proximity effect, and eddy current losses due to stray magnetic fields and crosstalk between adjacent turns and strands. The number of layers of the PCB, the thickness of the PCB, the thickness of the inner and outer copper layers, the number of strands per turn, the width, and the position of the individual strands are the sensitive design and optimization parameters. Fig. 4-10 depict details of a design methodology consistent with aspects of the disclosure. The number of layers and the copper thickness in each layer are two design parameters used herein to minimize PCB loss and temperature. The maximum thickness of the copper layer is limited by the effect of skin depth. At approximately 100 kHz, the copper thickness can be as high as 15 oz, and at approximately 20 kHz, it can be even thicker. However, fabricating thicker copper layers is difficult and costly. However, if a lower copper thickness is chosen, such as 4 oz, a higher number of layers can be implemented to fabricate the PCB cost-effectively. As the number of PCB layers increases, the number of strands per turn increases proportionally, and this reduces PCB loss. However, the maximum number of layers is limited by the structural integrity of the PCB.

[0034] Fig. 4 illustrates a portion of an RT 400 in accordance with aspects of the disclosure. The RT 400 includes a rotatable PCB 410, secondary windings 412 integrated with the rotatable PCB 410, primary windings 126A, a ferrite core 432, and a gap 434 configured and arranged as shown. The loss and temperature rise of the PCB secondary windings 412 depend on the position and width of the strands T1 through T6, the number of strands per turn, and the thickness of the copper layers of the PCB 410. All turns may have the same number of strands or a different number of strands, depending on their relative position and the overall loss distribution in the PCB. For example, a higher number of strands is advantageous for the turns near the gap compared to the turns away from the gap. The Fig. The RT 400 shown in Figure 4 represents a PCB design with 6 turns and 5 strands per turn. The traces are arranged on only two of the PCB layers. Two additional layers (not shown) are required to implement the twists T1-T2, T2-T3, T4-T5, and T5-T6. Both the trace width and trace position are optimized for this design. The result shows that the widths of the strands closer to gap 434 are much narrower than the widths of the strands farther from gap 434. Fig. 5 illustrates Equation 3, which is an optimization equation in accordance with aspects of the disclosure. Using Equation 3, the strands of the PCB 410 are optimized to minimize the total power losses in the PCB 410, minimize the peak temperature rise in the PCB 410, and keep the traces away from the gap 434. In general, Equation 3 is an objective optimization function. The objective function set in the modeling software examines various design configurations to minimize the total power loss and peak temperature rise while attempting to keep the traces away from the air gap. Therefore, Equation 3 can be used in the modeling software running on the computer system 1100 (in Fig. 11) to achieve optimization goals.

[0035] Both the width (W) and position (P) of the conductive traces can be optimized. During the optimization process, the width of each of the strands can be entered as an optimization parameter. However, this significantly increases the optimization time due to the longer processing time. Fig. 6A, Fig. 6B and Fig. 6C illustrate example optimization methods consistent with aspects of the disclosure. Additionally, the number of layers and the thickness of each layer are two optimization parameters used in embodiments of the disclosure to determine the total loss and temperature rise of the PCB 410. Fig. Figure 6A shows a trace T1 illustrating an example in which both the position (P) and the width (W) of each strand in each layer are considered as optimization parameters. Fig. Figure 6B shows another example of trace T1, illustrating an example where both the position (P) and width (W) of each strand on a layer are considered as optimization parameters. Strands of the same turn in parallel layers are copies of the optimized layer. This method significantly simplifies optimization. Fig. Figure 6C shows another example of trace T1, illustrating an example where the position (P) of each strand on a layer IS is considered as an optimization parameter. The widths (W) of all strands are the same. This method further simplifies the optimization method.

[0036] Twisting functionality related to aspects of the disclosure will now be described. A winding design in accordance with aspects of the disclosure can be categorized into two topologies. The first topology is multiple turns per layer, distributed in a spiral pattern, and the second topology is only one turn with multiple strands placed above each layer. With respect to the first topology, twisting can be introduced at various locations in the winding to balance the currents among the strands in a winding. Fig. Figure 7A shows the axially symmetric cross-sectional view of a 6-turn PCB 710, where the winding has two strands. The six circular turns are wound as T1-T2-T3-T4-T5-T6. To ensure that the mean length per strand (MLS) is approximately equal, this disclosure proposes a turn-to-turn twist among the strands. For example, if the relative positions of the strands are reversed, as in the PCB 720 of Fig. As shown in Figure 7B, the MLS of strand 1 and strand 2 are approximately the same. This reversal of the relative strand positions is referred to herein as "twisting." Twisting can be introduced at various positions in the winding. For example, the following twisting options provide a balanced MLS in the following system. For option 1, apply two twists—one between T1 and T2; and another between T4 and T5. For option 2, apply two twists—one between T2 and T3; and another between T4 and T5. For option 3, apply four twists—one between T1 and T2; one between T4 and T5; one between T2 and T3; and one between T4 and T5. For option 4, apply one twist between T3 and T4.

[0037] As the number of turns increases, the twisting options increase to balance the MLS among the strands. Among the four twisting options mentioned above, the fourth has technical advantages over the others. Balanced MLS can be achieved with just one twist, from T3 to T4, in the middle of the turn as the traces move from one side of the PCB to the other. Likewise, this configuration does not require an additional PCB layer for the twisting, while other options (options 1-3) require two additional layers in the PCB to implement the twisting. Similarly, when there are only two strands, there is only one option for the strand twisting order: reversing the position of strand 1 and strand 2. As the number of strands increases, the options for repositioning the strands also increase.The reversal of the order of all strands is referred to here as a “full twist” (an example of this is shown in . Fig. 8A) and the repositioning of part of the strand is referred to here as partial twisting (an example of this is shown in Fig. 8B). Because the strands of each turn extend across more than one layer, the options and flexibility of a partial twist increase. As with full twist, the same MLS can be achieved by applying multiple partial twists, which can be advantageous when placing vias (which extend from one PCB layer to another PCB layer) to physically implement the twist in the PCB design.

[0038] As previously mentioned herein, a winding design in accordance with aspects of the disclosure can be categorized into two topologies. The first topology is multiple turns per layer, distributed in a spiral pattern, and the second topology is only one turn with multiple strands placed over each layer. With respect to the second topology, Fig. Figure 9 illustrates a PCB 910 with a winding design configured and arranged to include one turn (10 strands) on each layer, and a twist is introduced between turn-3 and turn-4. Such a twist can be introduced without using additional layers. For the PCB 910, each layer includes one turn. A full twist is introduced between turn-3 and turn-4, balancing the inductance and MLS of the strands. This design does not require an additional layer to apply the twist. The twist can be applied sequentially as the traces drop from layer 3 to layer 4. The MLS can be balanced by just one twist for an even and odd number of twists. Alternatively, two or more twists can be applied instead of one twist to achieve easier MLS balancing.The position, width and thickness of the traces and number of layers are subject to optimization following the proposed optimization procedure described in . Fig. 4-6C and previously described here.

[0039] Fig. 10 is a diagram illustrating an example of how a strand twist operation from a first layer of a PCB to a second lower layer of the PCB may be implemented using vias in accordance with aspects of the disclosure. As shown, at the first layer, strand-1 is physically and electrically coupled to via-1; strand-2 is physically and electrically coupled to via-2; strand-3 is physically and electrically coupled to via-3; strand-4 is physically and electrically coupled to via-4; strand-5 is physically and electrically coupled to via-5; and strand-6 is physically and electrically coupled to via-6.Via-1 carries strand-1 from the first layer of the PCB to the second layer of the PCB and further changes strand-1 from occupying a first and outermost position at the first layer to occupying a sixth and innermost position at the second layer of the PCB. Via-2 carries strand-2 from the first layer of the PCB to the second layer of the PCB and further changes strand-2 from occupying a second position at the first layer to occupying a fifth position at the second layer of the PCB. Via-3 carries strand-3 from the first layer of the PCB to the second layer of the PCB and further changes strand-3 from occupying a third position at the first layer to occupying a fourth position at the second layer of the PCB.Via-4 takes strand-4 from the first layer of the PCB to the second layer of the PCB and further changes strand-4 from occupying a fourth position at the first layer to occupying a third position at the second layer of the PCB. Via-5 takes strand-5 from the first layer of the PCB to the second layer of the PCB and further changes strand-5 from occupying a fifth position at the first layer to occupying a second position at the second layer of the PCB. Via-6 takes strand-6 from the first layer of the PCB to the second layer of the PCB and further changes strand-6 from occupying a sixth position at the first layer to occupying a first position at the second layer of the PCB.

[0040] Therefore, it is apparent from the foregoing detailed description that the integrated mounting and / or communication structures (e.g., a PCB) described herein provide technical advantages and technical effects. The secondary windings and the rectifier subsystems are incorporated into the same PCB structure, which greatly simplifies the design, prototyping, and production of the associated RT. Embodiments of the disclosure also reduce or eliminate the difficulties in connections and interconnections between the rectifier and secondary winding assemblies. Embodiments of the disclosure further allow the assembly portion (e.g., the assembly portion that houses the rectifier's diodes) to be mounted directly onto the motor shaft using an aluminum support sleeve, providing high mechanical robustness and easier thermal management.In accordance with aspects of the disclosure, the integrated mounting and communication structure therefore enables motor designs that prioritize compact size, reduced cost, simplicity in electrical, mechanical and thermal design, and reduced eddy current losses.

[0041] Fig. 11 illustrates an example of a computer system 1100 that may be used to implement the computer-based components in accordance with aspects of the disclosure. The computer system 1100 includes an example computing device ("computer") 1102 configured to perform various aspects of the content-based semantic monitoring operations described herein in accordance with aspects of the disclosure. In addition to computer 1102, the example computer system 1100 includes a network 1114 that connects the computer 1102 to additional systems (not shown) and may include one or more wide area networks (WANs) and / or local area networks (LANs) such as the Internet, intranet(s), and / or wireless communication network(s). The computer 1102 and additional system communicate via the network 1114, e.g., to communicate data between them.

[0042] The example computer 1102 includes processor cores 1104, main memory ("memory") 1110, and input / output component(s) 1112 that communicate with each other via bus 1103. Processor cores 1104 include cache memory ("cache") 1106 and controllers 1108 that contain branch prediction structures and associated search, hit, detection, and update logic, which are described in more detail below. Cache 1106 may include multiple cache levels (not shown) located on or off-chip of processor 1104. Memory 1110 may have various data stored therein, e.g., instructions, software, routines, etc., which may be transferred to / from cache 1106 for execution by processor 1104, e.g., by controllers 1108.Input / output component(s) 1112 may include one or more components that facilitate local and / or remote input / output operations to / from computer 1102, such as a display, a keyboard, a modem, a network adapter, etc. (not shown).

[0043] A cloud computing system 50 is in wired or wireless electronic communication with the computer system 1100. The cloud computing system 50 may supplement, support, or replace some or all of the functionality (in any combination) of the computer system 1100. Additionally, some or all of the functionality of the computer system 1100 may be implemented as a node of the cloud computing system 50.

[0044] The various winding optimization and twist design processes may be implemented by a computer-aided design (CAD) system capable of performing calculations, circuit modeling, and circuit simulation operations in accordance with aspects of the disclosure. In accordance with aspects of the disclosure, the previously described CAD system may be implemented using computer system 1100 (in Fig. 11) to execute CAD software applications capable of performing the various calculations and algorithms described herein.

[0045] The various components / modules of the systems illustrated herein are shown separately for ease of illustration and explanation. In embodiments of the disclosure, the functions performed by the various components / modules / models may be distributed differently than shown here without departing from the scope of the various embodiments of the disclosure described herein, unless expressly stated otherwise.

[0046] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It is further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, acts, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, acts, element components, and / or groups thereof.

[0047] The diagrams presented here are for illustrative purposes only. Many variations of the diagram or the steps (or operations) described therein may exist without departing from the spirit of the disclosure. For example, the actions may be performed in a different order, or actions may be added, deleted, or modified. Also, the term "coupled" describes a signal path between two elements and does not imply a direct connection between the elements without intervening elements / connections. All such variations are considered part of the present disclosure.

[0048] The following definitions and abbreviations are to be used for the interpretation of the claims and the description. As used herein, the terms "comprises," "comprising," "contains," "containing," "has," "having," "includes," or "containing," or any other variation thereof, are intended to cover non-exclusive inclusion. For example, a composition, mixture, process, method, article, or device that includes a list of elements is not necessarily limited to only those elements, but may also include other elements not expressly listed or pertaining to that composition, mixture, process, method, article, or device.

[0049] Additionally, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are to be understood to include any integer greater than or equal to one, i.e., one, two, three, four, etc. The term "a plurality" is to be understood to include any integer greater than or equal to two, i.e., two, three, four, five, etc. The term "connection" can include both an indirect "connection" and a direct "connection."

[0050] The terms "about," "substantially," "approximately," and variations thereof are intended to convey the degree of error associated with a measurement of the particular quantity based on the equipment available at the time of filing the application. For example, "about" may include a range of ± 8%, 5%, or 2% of a given value.

[0051] Aspects of the disclosure may be embodied as a system, a method, and / or a computer program product at any possible level of integration of technical detail. The computer program product may include a computer-readable storage medium (or media) having computer-readable program instructions thereon for causing a processor to perform aspects of the present disclosure.

[0052] The computer-readable storage medium may be a tangible device capable of holding and storing instructions for use by an instruction execution device. The computer-readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing.A non-exhaustive list of more specific examples of computer-readable storage media includes the following: a portable computer diskette, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punched cards or raised structures in a groove with instructions recorded thereon, and any suitable combination of the foregoing.A computer-readable storage medium, as used herein, is not to be construed as containing transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber optic cable), or electrical signals transmitted through a wire.

[0053] The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or section of instructions comprising one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions specified in the blocks may occur in a different order than indicated in the figures. For example, two blocks shown in order may actually execute substantially concurrently, or the blocks may sometimes execute in reverse order, depending on the functionality involved.It is also noted that each block of the illustrated block diagrams and / or flowchart, and combinations of blocks in the illustrated block diagrams and / or flowchart, may be implemented by hardware-based special purpose systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0054] While the disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, the invention is not intended to be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but the invention is intended to include all embodiments falling within the scope of the claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 333,790

[0001]

Claims

[1] Rotary transformer (RT), comprising: a printed circuit board (PCB); and a set of secondary windings integrated with the PCB; wherein the set of secondary windings comprises a plurality of conductive traces extending across a first region of the PCB and a second region of the PCB; wherein the plurality of conductive traces are organized in a first positional order in the first region of the PCB; and wherein the plurality of conductive traces are organized in a second positional order in the second region of the PCB. [2] The RT of claim 1, wherein the PCB further comprises a first of the plurality of conductive traces. [3] The RT of claim 2, wherein the first of the plurality of conductive traces has a first position location in the first position sequence. [4] The RT of claim 3, wherein the first of the plurality of conductive traces has a second position location in the second position order. [5] RT according to claim 4, wherein the first position location in the first position order is different from the second position location in the second position order. [6] The RT of claim 5, wherein the RT further comprises a first via element. [7] The RT of claim 6, wherein a first end of the first via element is physically and electrically coupled to the first of the plurality of conductive traces in the first region. [8] The RT of claim 7, wherein a second end of the first via element is physically and electrically coupled to the first of the plurality of conductive traces in the second region. [9] RT according to claim 8, wherein: the first region comprises a first layer of the PCB; and the second region comprises a second layer of the PCB. [10] RT according to claim 1, wherein: each of the plurality of conductive tracks comprises several strands; each of the plurality of strands comprises a width (W) and a position (P) within its associated conductive trace; W and P are optimized to minimize inductance loss; and W and P are further optimized to minimize peak PCB temperature. [11] A method of manufacturing a rotary transformer (RT), the method comprising: Forming a printed circuit board (PCB); and Forming a set of secondary windings integrated with the PCB; wherein the set of secondary windings comprises a plurality of conductive traces extending across a first region of the PCB and a second region of the PCB; wherein the plurality of conductive traces are organized in a first positional order in the first region of the PCB; and wherein the plurality of conductive traces are organized in a second positional order in the second region of the PCB. [12] The method of claim 11, wherein the PCB further comprises a first of the plurality of conductive traces. [13] The method of claim 12, wherein the first of the plurality of conductive traces has a first position location in the first position sequence. [14] The method of claim 13, wherein the first of the plurality of conductive traces has a second position location in the second position sequence. [15] The method of claim 14, wherein the first position location in the first position order is different from the second position location in the second position order. [16] The method of claim 15, further comprising forming a first via element of the PCB. [17] The method of claim 16, wherein a first end of the first via element is physically and electrically coupled to the first of the plurality of conductive traces in the first region. [18] The method of claim 17, wherein a second end of the first via element is physically and electrically coupled to the first of the plurality of conductive traces in the second region. [19] The method of claim 18, wherein: the first region comprises a first layer of the PCB; and the second region comprises a second layer of the PCB. [20] The method of claim 11, wherein: each of the plurality of conductive tracks comprises several strands; each of the plurality of strands comprises a width (W) and a position (P) within its associated conductive trace; W and P are optimized to minimize inductance loss; and W and P are further optimized to minimize peak PCB temperature.

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