Ultra-compact, self-powered DC supply with surge voltage mitigation within electric machines

Abstract

A DC power supply circuit is connected across a stator coil of an electric motor, the stator coil configured to be energized with an alternating current (AC) power signal. The DC power supply circuit includes a first inductor, a second inductor, and a rectifier circuit. The first inductor is connected to one side of the stator coil, and the second inductor is connected to the other side of the stator coil. The first inductor and the second inductor operate as a low-pass filter, passing low-frequency voltage components of the AC power signal into the rectifier circuit. The rectifier circuit rectifies the low-frequency voltage components of the AC power signal into a rectified signal between a rectifier circuit first output terminal and a rectifier circuit second output terminal.

Description

ULTRA-COMPACT, SELF-POWERED DC SUPPLY WITH SURGE VOLTAGE MITIGATION WITHIN ELECTRIC MACHINESRELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 635,169, filed April 17, 2024, the entire disclosure of which is incorporated herein by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] The presently disclosed invention was made with support from the U.S. Government under Grant Number 3200004760 awarded by the Office of Naval Research. Thus, the U.S. Government has certain rights in the invention.BACKGROUND OF THE INVENTION1. Field of the Invention

[0003] The presently-disclosed subject matter relates to electric motors (i.e., electric machines), and, more specifically, to ultra-compact, self-powered DC power supplies with surge voltage mitigation within electric motors.2. Description of Related Art

[0004] Around 70% of the total electric consumption in the US is attributed to electric motors [1], This number is projected to increase in near future by transitioning to decarbonized transportation and the extensive use of variable frequency motor drive systems in various domains of the aviation, marine, and transportation sectors [2-4], Meanwhile, in motor-drive applications, emerging wide bandgap switches are getting a growing market share due to their high efficiency and improved power density [5], It is estimated that the GaN and SiC markets’ revenue will grow up to $2 billion and $6 billion by 2027, respectively [6],

[0005] Referring to FIG. 1, wide bandgap devices 10 are crucial for modem power electronics due to several key advantages they offer over traditional silicon-based devices,including high efficiency, fast switching speed, high voltage and high temperature withstanding capabilities. However, short rise time (high dv / dt) associated with these fastswitching semiconductors and interaction with cable 20 and motor 30 impedances can cause voltage reflections and transient overvoltage across motor terminals, as illustrated in the exemplary AC power signal 40 shown. If not mitigated, such voltage reflections and overvoltage will cause premature motor insulation aging and motor failures.

[0006] A “smart coil” circuit, including an adaptive impedance circuit (including a voltage sensing circuit and a gate driver circuit), connected in parallel with an inductive coil or coils of an electric motor, has been proposed. See, e.g., WO 2023 / 150785 A2. Such smart coil circuit requires a DC power supply to provide power to the adaptive impedance circuit. However, such a power supply might not be available at the motor junction box 50 (FIG. 1), and using an additional power supply will add to the cost and lower the power density, which defeats the purpose of smart coils.

[0007] Currently, there is no power supply that can utilize high-voltage AC power used to drive an electric motor to generate DC power at the motor. Thus, any application requiring DC power at the motor requires the use of an external, bulky, separately supplied DC power supply.BRIEF SUMMARY OF THE INVENTION

[0008] In accordance with one aspect of the invention, an electric motor system includes a rotor configured to be coupled to a mechanical load, stator windings configured to cause the rotor to turn, the stator windings including a stator coil, and a DC power supply circuit connected in parallel with the stator coil. The stator coil is configured to be energized with an alternating current (AC) power signal. The DC power supply circuit includes a low- pass filter configured to pass low-frequency voltage components of the AC power signal into the DC power supply circuit, and a rectifier circuit configured to rectify the low-frequency voltage components of the AC power signal into a rectified signal.

[0009] In one implementation, the stator coil includes a stator coil first terminal and a stator coil second terminal. The low-pass filter may include a first inductor including a first inductor first terminal and a first inductor second terminal, the first inductor first terminal connected to the stator coil first terminal, and a second inductor including a second inductor first terminal and a second inductor second terminal, the second inductor first terminal connected to the stator coil second terminal. The rectifier circuit may include a rectifiercircuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal, the rectifier circuit first input terminal connected to the first inductor second terminal, the rectifier circuit second input terminal connected to the second inductor second terminal, and the rectified signal output between the rectifier circuit first output terminal and the rectifier circuit second output terminal. The rectifier circuit may be a bridge rectifier.

[0010] In another embodiment, the electric motor system further includes a DC / DC converter including a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DC converter first output terminal, and a DC / DC converter second output terminal. The DC / DC converter first input terminal is connected to the rectifier circuit first output terminal, and the DC / DC converter second input terminal is connected to the rectifier circuit second output terminal. The DC / DC converter is configured to convert the rectified signal into a stable DC voltage signal between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

[0011] In yet another embodiment, the electric motor system further includes a high-pass filter, the high-pass filter passing high-frequency voltage components of the AC power signal around the stator coil. The high-pass filter may include a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminal connected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

[0012] In still yet another embodiment, the electric motor system further includes a smoothing filter, the smoothing filter smoothing ripple in the rectified signal between the rectifier circuit first output terminal and the rectifier circuit second output terminal. The smoothing filter may include a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit first output terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.

[0013] In accordance with another aspect of the invention, a method of operating an electric motor includes energizing a stator coil of the electric motor with an alternating current (AC) power signal, passing low-frequency voltage components of the AC power signal through a low-pass filter into a DC power supply circuit connected in parallel with the stator coil, and rectifying, by a rectifier circuit, the low-frequency voltage components of the AC power signal into a rectified signal.

[0014] In one implementation, the stator coil has a stator coil first terminal and a stator coil second terminal, and the low-pass filter includes a first inductor and a second inductor. The first inductor has a first inductor first terminal and a first inductor second terminal. The first inductor first terminal is connected to the stator coil first terminal. The second inductor has a second inductor first terminal and a second inductor second terminal. The second inductor first terminal is connected to the stator coil second terminal. Also, the rectifier circuit includes a rectifier circuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal. The rectifier circuit first input terminal is connected to the first inductor second terminal, and the rectifier circuit second input terminal is connected to the second inductor second terminal. The rectified signal is between the rectifier circuit first output terminal and the rectifier circuit second output terminal. The rectifier circuit may be a bridge rectifier.

[0015] In one embodiment, the method of operating an electric motor further includes converting, by a DC / DC converter, the rectified signal into a stable DC voltage signal. The DC / DC converter includes a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DC converter first output terminal, and a DC / DC converter second output terminal. The DC / DC converter first input terminal is connected to the rectifier circuit first output terminal. The DC / DC converter second input terminal is connected to the rectifier circuit second output terminal. The stable DC voltage signal is provided between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

[0016] In another embodiment, the method of operating an electric motor further includes passing, by a high-pass filter, high-frequency voltage components of the AC power signal around the stator coil. The high-pass filter may include a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminal connected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

[0017] In yet another embodiment, the method of operating an electric motor further includes smoothing, by a smoothing filter, ripple voltage between the rectifier circuit first output terminal and the rectifier circuit second output terminal. The smoothing filter may include a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit firstoutput terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.

[0018] In accordance with yet another aspect of the invention, a DC power supply circuit is connected in parallel with a stator coil of an electric motor. The stator coil is configured to be energized with an alternating current (AC) power signal. The DC power supply circuit includes a low-pass filter configured to pass low-frequency voltage components of the AC power signal into the DC power supply circuit, and a rectifier circuit configured to rectify the low-frequency voltage components of the AC power signal into a rectified signal.

[0019] In one implementation, the stator coil has a stator coil first terminal and a stator coil second terminal, and the low-pass filter includes a first inductor and a second inductor. The first inductor has a first inductor first terminal and a first inductor second terminal. The first inductor first terminal is connected to the stator coil first terminal. The second inductor has a second inductor first terminal and a second inductor second terminal. The second inductor first terminal is connected to the stator coil second terminal. Also, the rectifier circuit includes a rectifier circuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal. The rectifier circuit first input terminal is connected to the first inductor second terminal, and the rectifier circuit second input terminal is connected to the second inductor second terminal. The rectified signal is between the rectifier circuit first output terminal and the rectifier circuit second output terminal. The rectifier circuit may be a bridge rectifier.

[0020] In one embodiment, the DC power supply circuit further includes a DC / DC converter including a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DC converter first output terminal, and a DC / DC converter second output terminal. The DC / DC converter first input terminal is connected to the rectifier circuit first output terminal, and the DC / DC converter second input terminal is connected to the rectifier circuit second output terminal. The DC / DC converter converts the rectified signal into a stable DC voltage signal between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

[0021] In another embodiment, the DC power supply circuit further includes a high- pass filter, the high-pass filter passing high-frequency voltage components of the AC power signal around the stator coil. The high-pass filter may include a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminalconnected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

[0022] In yet another embodiment, the DC power supply circuit further includes a smoothing filter, the smoothing filter smoothing ripple voltage between the rectifier circuit first output terminal and the rectifier circuit second output terminal. The smoothing filter may include a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit first output terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. l is a schematic diagram of an exemplary electric motor system according to the prior art.

[0024] FIG. 2 is schematic diagram of an exemplary electric motor drive system according to the prior art.

[0025] FIG. 3 is schematic diagram of an exemplary DC power supply circuit according to the invention.

[0026] FIG. 4 is a set of graphs of the experimental results of the exemplary DC power supply circuit of FIG. 3 using a first set of exemplary components and conditions.

[0027] FIG. 5 is a set of graphs of the experimental results of the exemplary DC power supply circuit of FIG. 3 using a second set of exemplary components and conditions.

[0028] FIG. 6 is a flow chart of an exemplary method of operating an electric motor according to the invention.DETAIL DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0029] The details of one or more embodiments of the presently-disclosed invention are set forth in this document. Modifications to embodiments described herein, and other embodiments, will be evident to those of ordinary skill in the art after a study of the information provided herein. The information provided herein, and particularly the specific details of the described exemplary embodiments, is provided primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom. In case of conflict, the specification of this document, including definitions, will control.

[0030] While the terms used herein are believed to be well understood by one of ordinary skill in the art, definitions are set forth herein to facilitate explanation of the presently-disclosed subject matter.

[0031] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the presently-disclosed subject matter belongs. Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the presently-disclosed subject matter, representative methods, devices, and materials are now described.

[0032] Following long-standing patent law convention, the terms “a”, “an”, and “the” refer to “one or more” when used in this application, including the claims.

[0033] FIG. 2 is a schematic diagram of an exemplary electric motor drive system 100. Electric motor drive system 100 utilizes an AC power supply 102 and turns, or operates, a mechanical load 104. Electric motor drive system 100 includes a motor controller 106 (also referred to as a variable speed drive) for controlling the generation of one or more phases of AC at a determined voltage and frequency for application to stator windings 108. Upon energizing stator windings 108, a rotor 110 electromagnetically coupled to stator windings 108 turns. Rotor 110 is coupled to mechanical load 104 and turns mechanical load 104.

[0034] Electric motor drive system 100 and, more specifically, motor controller 106 includes various power electronics for conditioning AC power, e.g., line frequency 230 volt or 480 volt, received from AC power supply 102. The power electronics may include, for example, components for conditioning line frequency AC power to be supplied to stator windings 108 with a desired current, i.e., phase, amplitude, and frequency. Such power electronics may include, for example, and without limitation, one or more rectifier stages, power factor correction (PFC) circuits, filters, transient protection circuits, EMF protection circuits, inverters, or power semiconductors. AC power supply 102 may supply any suitable frequency for a given application, including, for example, 50 Hertz, 60 Hertz, or 400 Hertz, among others. AC power supply 102 may supply any suitable voltage for a given application, including, for example, 100 volts, 110 volts, 200 volts, 220 volts, 300 volts, or 600 volts, among others.

[0035] More specifically, motor controller 106 includes a rectification circuit 112, a DC bus 114, and an inverter 116. Rectification circuit 112 converts, or rectifies, supplied ACvoltage to a DC voltage to energize DC bus 114. DC bus 114 may operate at any suitable DC voltage, including, for example, 300 VDC, 380 VDC, 480 VDC, 600 VDC, or any other DC voltage suitable for supply to inverter 116. DC bus 114 may also include one or more filter components, passive or active, for conditioning the DC voltage for supply to inverter 116. For example, in certain embodiments, DC bus 114 may include one or more capacitors coupled between positive and negative nodes of DC bus 114 to “smooth” and stabilize the DC bus voltage.

[0036] Inverter 116, sometimes referred to as a variable frequency drive, variable speed drive, or variable frequency variable voltage drive, generally includes a plurality of semiconductor switching devices for converting the DC bus voltage to a multi-phase, variable frequency, variable voltage AC power for energizing stator windings 108. The semiconductor switching devices in modem inverters may include, for example, WBG semiconductor switches such as SiC MOSFETs or GaN transistors. Previous generations of inverters utilized silicon-based power MOSFETs or IGBTs. Accordingly, modem inverters, such as inverter 116, can operate at switching frequencies five to ten times greater than with silicon-based devices. For example, in certain embodiments, WBG semiconductors switch at 100 kilohertz (kHz), 50 kHz, 40 kHz, 30 kHz, 20 kHz, 10 kHz, or any other suitable high frequency for WBG devices. Conversely, certain IGBT devices, for example, switch at 10 kHz, 5 kHz, 2.5 kHz, or lower. Operation of inverter 116 and, more specifically, operation of the individual WBG semiconductor switches is controlled by a microcontroller 118.

[0037] Microcontroller 118 is an embedded computing system for controlling operation of electric motor drive system 100 and, in particular, inverter 116. Microcontroller 118 includes memory 120 and a processing unit 122. Memory 120 stores one or more programs, applications, firmware, or other software instructions for execution by processing unit 122.

[0038] Inverter 116 generates a variable frequency, variable voltage output to energize stator windings 108. Inverter 116 is electrically connected to stator windings 108 by a cable 124 including a plurality of conductors 126. Cable 124 may include, for example, one or more dedicated conductors for each AC phase output from inverter 116. In certain embodiments, motor controller 106 is positioned remotely from stator windings 108 and rotor 110. In other embodiments, motor controller 106 is positioned integral with or adjacent to stator windings 108 and rotor 110. Accordingly, depending on the implementation, the lengths of conductors 126 can vary widely.

[0039] FIG. 3 is a schematic diagram of an exemplary first-ever, ultracompact, self- powered DC power supply circuit 200 configured for placement inside an AC motor (i.e., inside a junction box 50 (FIG. 1) of an AC motor). Additionally, the exemplary DC power supply circuit 200 effectively mitigates high-frequency reflective voltage stress across the connected motor coil. This exemplary DC power supply circuit 200 can power any auxiliary component intended for integration or embedding inside the AC motor or at its junction box. The exemplary DC power supply circuit 200 is connected in parallel with a stator coil 202 of the AC motor and draws power from the stator coil 202, eliminating the need for an external power supply. Being able to mitigate the surge overvoltage to some extent, the DC power supply circuit 200 can effectively increase the reliability and lifetime of the AC motor.

[0040] The stator coil 202 is configured to be energized with an alternating current (AC) power signal provided by a motor controller 106 (FIG. 2). An exemplary AC power signal could include a DC-link voltage of 400V, a switching frequency of 10 kHz, a fundamental frequency of 10 Hz, and a modulation index of 0.4, although these exemplary values are illustrative only and in no way limit the scope of the DC power supply circuit 200. The stator coil 202 includes a stator coil first terminal 204 and a stator coil second terminal 206.

[0041] In a first stage, the exemplary DC power supply circuit 200, connected in parallel with the stator coil 202, is configured to divide the AC power signal into low- and high-frequency components. This stage includes a first inductor Li and a second inductor L2. The first inductor Li and the second inductor L2 operate as a low-pass filter, passing low- frequency voltage components of the AC power signal into the exemplary DC power supply circuit 200. In the exemplary embodiment, high-inductance inductors, each having an inductance of 220 pH, are employed to filter out high-frequency reflected voltages.

[0042] The first inductor Li includes a first inductor first terminal 208 and a first inductor second terminal 210. The first inductor first terminal 208 is in electrical communication with the stator coil first terminal 204.

[0043] The second inductor L2 includes a second inductor first terminal 212 and a second inductor second terminal 214. The second inductor first terminal 212 is in electrical communication with the stator coil second terminal 206.

[0044] Meanwhile, a high-pass filter 220 is connected in parallel with the stator coil 202. The high-pass filter 220 is configured to block low-frequency components of the AC power signal essential for proper operation of the stator coil 202, and to provide a low-impedance path for high-frequency voltage spikes resulting from voltage reflection and mitigate transient overvoltage at each switching state.

[0045] In the exemplary embodiment, the high-pass filter 220 includes a first capacitor Cin. The first capacitor Cin includes a first capacitor first terminal 222 and a first capacitor second terminal 224. The first capacitor first terminal 222 is in electrical communication with the stator coil first terminal 204, and the first capacitor second terminal 224 is in electrical communication with the stator coil second terminal 206. In the exemplary embodiment, Cin is a small-capacitance capacitor with a capacitance of 1.1 nF.

[0046] In a second stage, the exemplary DC power supply circuit 200 includes a rectifier circuit 230 including a rectifier circuit first input terminal 232, a rectifier circuit second input terminal 234, a rectifier circuit first output terminal 236, and a rectifier circuit second output terminal 238. The rectifier circuit first input terminal 232 is in electrical communication with the first inductor second terminal 210, and the rectifier circuit second input terminal 234 is in electrical communication with the second inductor second terminal 214. The rectifier circuit 230 is configured to rectify the low-frequency voltage components of the AC power signal passed by the first inductor Li and the second inductor L2 into a rectified signal between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238.

[0047] In the exemplary embodiment, the rectifier circuit is a bridge rectifier. The rectified signal exhibits ripple with a frequency twice as high as the fundamental AC power signal frequency.

[0048] The exemplary DC power supply circuit 200 further includes a smoothing filter 240. The smoothing filter 240 is configured to smooth the ripple in the rectified signal between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238.

[0049] In the exemplary embodiment, the smoothing filter 240 includes a second capacitor Cmid. The second capacitor Cmid includes a second capacitor first terminal 242 and a second capacitor second terminal 244. The second capacitor first terminal 242 is in electrical communication with the rectifier circuit first output terminal 236, and the second capacitor second terminal 244 is in communication with the rectifier circuit second output terminal 238. In the exemplary embodiment, Cmid is an electrolytic capacitor with a capacitance of 470 pF.

[0050] The average voltage across the smoothing filter 240 depends on the modulation index and DC-link voltage of the inverter driving the motor. To address this, a DC / DC converter 250 can be employed at the output stage to provide a stable voltage. The DC / DC converter 250 includes a DC / DC converter first input terminal 252, a DC / DC converter second input terminal 254, a DC / DC converter first output terminal 256, and a DC / DC converter second output terminal 258. The DC / DC converter first input terminal 252 is in electrical communication with the rectifier circuit first output terminal 236, and the DC / DC converter second input terminal 254 is in electrical communication with the rectifier circuit second output terminal 238. The DC / DC converter 250 is configured to convert the rectified signal into a stable DC voltage signal between the DC / DC converter first output terminal 256 and the DC / DC converter second output terminal 258.

[0051] In the exemplary embodiment, the DC / DC converter 250 may be a commercially available variable input, fixed output micro-module DC / DC converter, such as an LTM8046 or an LTM8067, both by Analog Devices, Inc. of Wilmington, Massachusetts, USA.

[0052] FIG. 4 shows experimental results of the exemplary DC power supply circuit 200 (FIG. 3) between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238 (FIG. 3) using the exemplary components and conditions described above. Namely, high-inductance inductors Li and L2, each with an inductance of 220 pH, were used to filter high-frequency reflected voltages. Additionally, a small capacitor Cm (1.1 nF) was placed to address overvoltage issues, while an electrolytic capacitor Cmid (470 pF), was utilized to smooth out the output voltage. The test conditions comprised a DC- link voltage of 400V, a switching frequency of 10 kHz, a fundamental frequency of 10 Hz, and a modulation index of 0.4. Thus, FIG. 4 shows a self-powered DC supply tested at 400V DC bus voltage, from top to bottom: first coil voltage, second coil voltage, third coil voltage, and the voltage between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238 (FIG. 3). Despite some ripples in the output voltage fluctuating at twice the fundamental frequency, FIG. 4 shows the successful generation of DC voltage from the coil voltages. The RMS voltage between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238 (FIG. 3) is 17.5 V with the peak-to- peak voltage ripple of 5 V. This setup can be optimized as a compact power supply for auxiliary electronic devices within or near the motor’s junction box 50 (FIG. 1).

[0053] FIG. 5 shows experimental results of the exemplary DC power supply circuit 200 (FIG. 3) between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238 (FIG. 3) with the DC-bus voltage reduced to 200V. Thus, FIG. 5 shows a self-powered DC supply tested at 200V DC-bus voltage, from top to bottom: first coil voltage, second coil voltage, third coil voltage, and the voltage between the rectifier circuit first output terminal 236 and the rectifier circuit second output terminal 238 (FIG. 3). The RMS and peak-to-peak voltages decrease to 9.35V and 2.2V, respectively, due to the lower DC-bus voltage and consequently lower voltage across the second coil. However, a commercially available variable-input, fixed-output DC / DC converters can easily provide a stable output based on this circuit.

[0054] FIG. 6 is a flow chart of an exemplary method 300 of operating an electric motor according to the invention.

[0055] Step S302 is energizing a stator coil of the electric motor with an alternating current (AC) power signal. The stator coil has a stator coil first terminal and a stator coil second terminal.

[0056] Step S304 is passing low-frequency voltage components of the AC power signal through a low-pass filter. In some embodiments, the low-pass filter includes a first inductor and a second inductor. The first inductor includes a first inductor first terminal and a first inductor second terminal, the first inductor first terminal connected to the stator coil first terminal. The second inductor includes a second inductor first terminal and a second inductor second terminal, the second inductor first terminal connected to the stator coil second terminal.

[0057] In some embodiments, step 306 is passing, by a high-pass filter, high- frequency voltage components of the AC power signal around the stator coil. In some embodiments, the high-pass filter includes a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminal connected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

[0058] Step 308 is rectifying, by a rectifier circuit, the low-frequency voltage components of the AC power signal into a rectified signal. In some embodiments, the rectifier circuit includes a rectifier circuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal. The rectifier circuit first input terminal is connected to the first inductor second terminal, andthe rectifier circuit second input terminal is connected to the second inductor second terminal. The rectified signal is between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

[0059] In some embodiments, step 310 is smoothing, by a smoothing filter, ripple voltage between the rectifier circuit first output terminal and the rectifier circuit second output terminal. In some embodiments, the smoothing filter includes a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit first output terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.

[0060] Step 312 is converting, by a DC / DC converter, the rectified signal into a stable DC voltage signal. In some embodiments, the DC / DC converter includes a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DC converter first output terminal, and a DC / DC converter second output terminal. The DC / DC converter first input terminal is connected to the rectifier circuit first output terminal, and the DC / DC converter second input terminal is connected to the rectifier circuit second output terminal. The stable DC voltage signal is provided between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

[0061] It will be understood that various details of the presently disclosed subject matter can be changed without departing from the scope of the subject matter disclosed herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.BIBLIOGRAPHY[1] U.S. Department of Energy Office of Energy Efficiency & Renewable Energy, “Electric machines,” www.energy.gov / eere / amo / electric-machines, accessed: 2022- 07-11.[2] V. Madonna, P. Giangrande, W. Zhao, H. Zhang, C. Gerada, and M. Galea, “Electrical machines for the more electric aircraft: Partial discharges investigation,” IEEE Transactions on Industry Applications, vol. 57, no. 2, pp. 1389-1398, 2020.[3] P. Ghimire, D. Park, M. K. Zadeh, J. Thorstensen, and E. Pedersen, “Shipboard electric power conversion: System architecture, applications, control, and challenges [technology leaders],” IEEE Electrification Magazine, vol. 7, no. 4, pp. 6-20, 2019.[4] T. Van Do, J. P. F. Trov'ao, K. Li, and L. Boulon, “Wide-bandgap powersemiconductors for electric vehicle systems: challenges and trends,” IEEE Vehicular Technology Magazine, vol. 16, no. 4, pp. 89-98, 2021.[5] A. K. Morya, M. C. Gardner, B. Anvari, L. Liu, A. G. Yepes, J. Doval-Gandoy, and H. A. Toliyat, “Wide bandgap devices in ac electric drives: Opportunities and challenges,” IEEE Transactions on Transportation Electrification, vol. 5, no. 1, pp. 3- 20, 2019.[6] A. Bindra, “Emerging monolithic bidirectional switches bring new energy to wbg devices [from the editor],” IEEE Power Electronics Magazine, vol. 10, no. 1, pp. 4-8, 2023.

Claims

CLAIMSWhat is claimed is:

1. An electric motor system comprising: a rotor configured to be coupled to a mechanical load; stator windings configured to cause the rotor to turn, the stator windings including: a stator coil configured to be energized with an alternating current (AC) power signal; and a DC power supply circuit connected in parallel with the stator coil, the DC power supply circuit comprising: a low-pass filter configured to pass low-frequency voltage components of the AC power signal into the DC power supply circuit; and a rectifier circuit configured to rectify the low-frequency voltage components of the AC power signal into a rectified signal.

2. The electric motor system of claim 1, wherein: the stator coil includes a stator coil first terminal and a stator coil second terminal; the low-pass filter includes: a first inductor including a first inductor first terminal and a first inductor second terminal, the first inductor first terminal connected to the stator coil first terminal; and a second inductor including a second inductor first terminal and a second inductor second terminal, the second inductor first terminal connected to the stator coil second terminal; and the rectifier circuit includes a rectifier circuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal, the rectifier circuit first input terminal connected to the first inductor second terminal, the rectifier circuit second input terminal connected to the second inductor second terminal, and the rectified signal output between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

3. The electric motor system of claim 2, further comprising a DC / DC converter including a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DCconverter first output terminal, and a DC / DC converter second output terminal, the DC / DC converter first input terminal connected to the rectifier circuit first output terminal, and the DC / DC converter second input terminal connected to the rectifier circuit second output terminal, the DC / DC converter configured to convert the rectified signal into a stable DC voltage signal between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

4. The electric motor system of claim 2, further comprising a high-pass filter, the high-pass filter configured to pass high-frequency voltage components of the AC power signal around the stator coil.

5. The electric motor system of claim 4, wherein the high-pass filter includes a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminal connected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

6. The electric motor system of claim 2, further comprising a smoothing filter, the smoothing filter configured to smooth ripple in the rectified signal between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

7. The electric motor system of claim 6, wherein the smoothing filter includes a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit first output terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.

8. A method of operating an electric motor, the method comprising: energizing a stator coil of the electric motor with an alternating current (AC) power signal; passing low-frequency voltage components of the AC power signal through a low-pass filter into a DC power supply circuit connected in parallel with the stator coil; and rectifying, by a rectifier circuit, the low-frequency voltage components of the AC power signal into a rectified signal.

9. The method of operating an electric motor of claim 8, wherein: the stator coil includes a stator coil first terminal and a stator coil second terminal; the low-pass filter includes:a first inductor having a first inductor first terminal and a first inductor second terminal, the first inductor first terminal connected to the stator coil first terminal; and a second inductor having a second inductor first terminal and a second inductor second terminal, the second inductor first terminal connected to the stator coil second terminal; and the rectifier circuit includes a rectifier circuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal, the rectifier circuit first input terminal connected to the first inductor second terminal, the rectifier circuit second input terminal connected to the second inductor second terminal, and the rectified signal output between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

10. The method of operating an electric motor of claim 9, further comprising converting, by a DC / DC converter, the rectified signal into a stable DC voltage signal, the DC / DC converter including a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DC converter first output terminal, and a DC / DC converter second output terminal, the DC / DC converter first input terminal connected to the rectifier circuit first output terminal, the DC / DC converter second input terminal connected to the rectifier circuit second output terminal, and the stable DC voltage signal provided between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

11. The method of operating an electric motor of claim 9, further comprising passing, by a high-pass filter, high-frequency voltage components of the AC power signal around the stator coil.

12. The method of operating an electric motor of claim 11, wherein the high-pass filter includes a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminal connected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

13. The method of operating an electric motor of claim 9, further comprising smoothing, by a smoothing filter, ripple between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

14. The method of operating an electric motor of claim 13, wherein the smoothing filter includes a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit first output terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.

15. A DC power supply circuit connected in parallel with a stator coil of an electric motor, the stator coil configured to be energized with an alternating current (AC) power signal, the DC power supply circuit comprising: a low-pass filter configured to pass low-frequency voltage components of the AC power signal into the DC power supply circuit; and a rectifier circuit configured to rectify the low-frequency voltage components of the AC power signal into a rectified signal.

16. The DC power supply circuit of claim 15, wherein: the stator coil includes a stator coil first terminal and a stator coil second terminal; the low-pass filter includes: a first inductor including a first inductor first terminal and a first inductor second terminal, the first inductor first terminal connected to the stator coil first terminal; and a second inductor including a second inductor first terminal and a second inductor second terminal, the second inductor first terminal connected to the stator coil second terminal; and the rectifier circuit includes a rectifier circuit first input terminal, a rectifier circuit second input terminal, a rectifier circuit first output terminal, and a rectifier circuit second output terminal, the rectifier circuit first input terminal connected to the first inductor second terminal, the rectifier circuit second input terminal connected to the second inductor second terminal, and the rectified signal output between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

17. The DC power supply circuit of claim 16 further comprising a DC / DC converter including a DC / DC converter first input terminal, a DC / DC converter second input terminal, a DC / DC converter first output terminal, and a DC / DC converter second output terminal, the DC / DC converter first input terminal connected to the rectifier circuit first output terminal,and the DC / DC converter second input terminal connected to the rectifier circuit second output terminal, the DC / DC converter configured to convert the rectified signal into a stable DC voltage signal between the DC / DC converter first output terminal and the DC / DC converter second output terminal.

18. The DC power supply circuit of claim 16, further comprising a high-pass filter, the high- pass filter configured to pass high-frequency voltage components of the AC power signal around the stator coil.

19. The DC power supply circuit of claim 18, wherein the high-pass filter includes a first capacitor having a first capacitor first terminal and a first capacitor second terminal, the first capacitor first terminal connected to the stator coil first terminal, and the first capacitor second terminal connected to the stator coil second terminal.

20. The DC power supply circuit of claim 16, further comprising a smoothing filter, the smoothing filter configured to smooth ripple between the rectifier circuit first output terminal and the rectifier circuit second output terminal.

21. The DC power supply circuit of claim 20, wherein the smoothing filter includes a second capacitor having a second capacitor first terminal and a second capacitor second terminal, the second capacitor first terminal connected to the rectifier circuit first output terminal, and the second capacitor second terminal connected to the rectifier circuit second output terminal.

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