Electric motors with mitigation of electrically induced bearing damage (EIBD)

Abstract

The present disclosure relates to an electric motor assembly configured to mitigate electrically induced bearing damage (EIBD). More specifically, the electric motor assembly includes a chassis, a stator, a winding coil, a rotor, a shaft, conductors, a circuit, and insulators. The circuit can include one or more transformers capable of generating an injection voltage, which can mitigate shaft voltages that cause EIBD.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 381,914, entitled "ROTOR VOLTAGE CANCELLATION," filed November 1, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to electric motors, and more particularly, to systems and methods for mitigating electrically induced bearing damage (EIBD) occurring in electric motors. [Background technology]

[0003] Electric motors have a wide range of applications, including use in various types of vehicles, such as electric vehicles, combustion engine vehicles, and hybrid vehicles. These motors function by converting electrical energy into mechanical energy. This conversion process involves applying electricity to the motor, which then generates magnetic fields in two key components: the stator (stationary part) and the rotor (rotating part). The interaction between the magnetic fields of the stator and rotor generates mechanical energy, causing the rotor to rotate. Typically, electric motors are supplied with multiple phases of alternating current (AC), each of which generates a different phase of the magnetic field. The AC is generated from an inverter, such as a switching inverter. For example, an inverter receives direct current (DC) from an external power source, such as a battery, and converts the DC to AC by switching it at various frequencies (e.g., turning the DC on and off). The inverter's switching mechanism can therefore generate AC waveforms of various frequencies and phases, allowing the rotational speed of the electric motor (e.g., rotor rotation) to be modulated by adjusting the frequency of the supplied AC.

[0004] Examples of electric motor applications may include, but are not limited to, electric vehicles, electric pumps, electric fans, robotic systems, and the like. Summary of the Invention

[0005] Each claimed innovation has several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of the claims, some prominent features of this disclosure will now be discussed briefly.

[0006] One aspect of the present disclosure is an electric motor assembly including a chassis, a stator configured to receive energy from an external energy source, a winding coil configured to generate a magnetic field, the winding coil mounted in the stator, a rotor magnetically coupled to the stator, a shaft connected to the rotor, a bearing connected between the shaft and the chassis, a conductor capacitively coupled to the rotor, a circuit configured to generate an injection voltage, the circuit connected to the winding coil and the conductor, and an insulator connected between the conductor and the chassis.

[0007] In an electric motor assembly, a rotor is rotated by a magnetic field generated by winding coils.

[0008] The electric motor assembly can receive energy from an inverter that can supply AC current to the electric motor assembly, and the AC current can include three waveforms having the same frequency. Further, each waveform can have a phase difference of 120 degrees.

[0009] In an electric motor assembly, the circuit may include a transformer, which may generate injected energy by receiving an induced current from the neutral point of a winding coil.

[0010] In an electric motor assembly, the electric motor can include parasitic capacitances between the chassis and the winding coil, between the winding coil and the rotor, between the stator and the rotor, and across the bearings. Common-mode voltages can generate shaft voltages between the shaft and the chassis. The shaft voltages can be mitigated by the injection voltage.

[0011] In an electric motor assembly, the circuit may include a first transformer, a second transformer, a low-pass filter, and a high-pass filter. The first transformer receives energy from a conductor and can transmit high-frequency band signals by filtering the energy through the high-pass filter. The second transformer receives energy from the neutral point of a winding coil and can convert low-frequency band signals by filtering the energy through the low-pass filter.

[0012] In the electric motor assembly, the electric motor assembly can be mounted in an electric vehicle.

[0013] Another aspect of the present disclosure is an electric motor assembly including a chassis, a stator configured to receive energy from an external energy source, winding coils configured to generate a magnetic field, the winding coils mounted in the stator, a rotor magnetically coupled to the stator, a shaft connected to the rotor, a bearing connected between the shaft and the chassis, a conductor capacitively coupled to the rotor, a transformer configured to generate an injection voltage, the transformer connected to the winding coils and the conductor, and an insulator connected between the conductor and the chassis.

[0014] In an electric motor assembly, the transformer can be integrated on the top side of the printed circuit board (PCB) and the conductors can be integrated on the bottom side of the PCB. Additionally, the transformer can receive energy from the neutral point of the winding coil.

[0015] In an electric motor assembly, the electric motor may include parasitic capacitances between the chassis and the winding coil, between the winding coil and the rotor, between the stator and the rotor, and across the bearings, and shaft voltage may be generated from one or more of the parasitic capacitances. Additionally, the shaft voltage may be mitigated by the injection voltage.

[0016] In the electric motor assembly, the rotor can rotate based on the switching frequency of the inverter, which can supply AC to the electric motor assembly.

[0017] In the electric motor assembly, the received energy may be alternating current, and the alternating current may include three waveforms having the same frequency. Further, each waveform may have a phase difference of 120 degrees. Further, the frequency may be a switching frequency of an inverter configured to supply the AC to the electric motor assembly.

[0018] In an electric motor assembly, a transformer may be connected to the neutral point of the winding coil.

[0019] In an electric motor assembly, the distance between the conductors and the rotor can be determined based on parasitic capacitance.

[0020] Another aspect of the present disclosure is a method for mitigating EIBD in an electric motor, the method including the steps of starting operation of the electric motor by receiving an input at a neutral point of the electric motor, generating a common-mode voltage, generating a shaft voltage that is a portion of the common-mode voltage, and generating an injection voltage to mitigate the shaft voltage, the injection voltage being generated from a transformer connected between the neutral point and a conductor of the electric motor, the input of the transformer receiving the input signal from the neutral point and the output of the transformer being connected to a conductor positioned away from the rotor, the input and output of the transformer having opposite polarities.

[0021] Another aspect of the present disclosure is a circuit for mitigating EIBD in an electric machine. The circuit includes a PCB substrate, a transformer integrated on a top side of the PCB substrate, the transformer configured to generate an injection voltage, an input configured to provide an input voltage to the transformer, the input being received from a neutral point of the electric machine, and an output of the transformer connected to a conductor of the circuit, the conductor being mounted on a bottom side of the PCB substrate, the output and the conductor being connected through a via in the PCB substrate. The electric machine can be an electric motor of an electric vehicle. The output can mitigate voltages generated by parasitic capacitances of the electric machine.

[0022] For purposes of summarizing the disclosure, certain aspects, advantages, and novel features of the innovations have been described herein. It should be understood that not all such advantages may necessarily be achieved in accordance with any particular embodiment. Thus, the innovations may be embodied or implemented to achieve or optimize one advantage or advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. [Brief explanation of the drawings]

[0023] The present disclosure is described herein with reference to drawings of specific embodiments that are intended to illustrate, but not limit, the disclosure. It should be understood that the accompanying drawings, which are incorporated in and constitute a part of this specification, are for the purpose of illustrating the concepts disclosed herein and may not be to scale.

[0024] [Figure 1] FIG. 1 illustrates an example of a cutaway view of an embodiment of an electric motor in accordance with one or more aspects of the present application.

[0025] [Figure 2A] FIG. 1 is a two-dimensional view of a conventional electric motor.

[0026] [Figure 2B]1 is a schematic diagram of a conventional electric motor.

[0027] [Figure 3A] FIG. 1 is a two-dimensional view of an electric motor according to one or more aspects of the present application.

[0028] [Figure 3B] FIG. 1 is a schematic diagram of an electric motor according to one or more aspects of the present application.

[0029] [Figure 4A] FIG. 1 illustrates rotor voltages corresponding to conventional electric motor operation.

[0030] [Figure 4B] FIG. 10 illustrates rotor voltages according to one or more aspects of the present application.

[0031] [Figure 5] FIG. 1 illustrates an example of a circuit having a smaller form factor.

[0032] [Figure 6] FIG. 1 illustrates an example of a flowchart for implementing a circuit for mitigating shaft voltage, in accordance with one or more aspects of the present application.

[0033] [Figure 7A] FIG. 1 illustrates an exemplary method for determining the parasitic capacitance of an electric motor. [Figure 7B] FIG. 1 illustrates an exemplary method for determining the parasitic capacitance of an electric motor. [Figure 7C] FIG. 1 illustrates an exemplary method for determining the parasitic capacitance of an electric motor.

[0034] [Figure 8] FIG. 1 illustrates an example of operating an electric motor by implementing a circuit for substantially reducing (e.g., substantially minimizing) shaft voltage, in accordance with one or more aspects of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0035] Although certain preferred embodiments and examples are disclosed below, the subject matter of the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses, as well as modifications and equivalents thereof. Accordingly, the scope of the appended claims is not limited by any of the specific embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable order and are not necessarily limited to any particular disclosed order. Various operations may be described as multiple separate operations in a manner that may be helpful in understanding a particular embodiment. However, the order of description should not be construed to imply that these operations are order-dependent. Furthermore, structures, systems, and / or devices described herein may be embodied as integrated or separate components. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments will be described. Not necessarily all such aspects or advantages are achieved by a particular embodiment. Thus, for example, various embodiments may be implemented to achieve or optimize one advantage or advantages as taught herein, without necessarily achieving other aspects or advantages as may be taught or suggested herein.

[0036] As demand for electric motors increases, there is growing interest in developing motors that can operate with significant lifespans. Therefore, reducing wear and tear on components is important. For example, electric motors that utilize a magnetic field between the stator and rotor can potentially minimize wear and tear. This is because these two components do not come into physical contact, thereby eliminating friction between them.

[0037] However, the operation of an electric motor can result in electrically induced bearing damage (EIBD). More specifically, an electric motor can receive energy (e.g., AC) from an inverter (e.g., a switching inverter). The inverter is configured to convert DC to AC, which is then utilized as the electric motor's energy source. The inverter can generate AC by switching operations. Typical steel bearings experience premature wear when installed in an electric machine powered by a switching inverter. This occurs due to the common-mode voltage inherent in switching inverter operation, which is partially captured by the rotor because part of the rotor is exposed to the windings carrying the inverter voltage. EIBD occurs when the rotor (and therefore the shaft) voltage rises above a threshold voltage, such as approximately 3.5 V, relative to the machine frame (usually the same as ground). Under these conditions, the thin insulating lubricant film on the bearing balls can break down, forming an arc. The accumulated charge then discharges onto the rotor through a substantially confined spot between the bearing ball and the race, forming a small weld and essentially initiating electrical discharge machining (EDM). This weld is subsequently pulled as the bearing moves, causing deformation on both the ball and race surfaces. This process repeats randomly every switching cycle. This phenomenon is more pronounced when the DC voltage connected to the inverter is high, as well as when the switching frequency is high, because all parts of the circuit are essentially interconnected through parasitic capacitance. Parasitic capacitance refers to the electrostatic capacitance that forms between two conductors, even when the designer does not intend it to.

[0038] Traditionally, to reduce or minimize electrical bearing damage, rotors may be physically grounded, allowing currents generated by parasitic capacitance to flow to ground instead of through the rotor and shaft to the bearing. For example, the rotor and the electric motor's chassis (which serves as the electric motor's ground) are electrically connected using conductive ball bearings between the rotor and stator. Another method involves using conductive brushes around the shaft to establish electrical contact with the motor's chassis. However, these traditional methods have technical limitations due to the inconsistent nature of the conductive compounds inside the bearing. Furthermore, implementing brushes can limit the operational life of the electric motor depending on the brush's lifespan. For example, brushes are in physical contact with one or more components of the electric motor, thereby causing unwanted wear and tear on the brushes due to physical contact (e.g., friction between components). Other traditional methods, such as using insulating bearings or chokes, also have technical limitations and do not address the underlying causes of generating unwanted voltages due to parasitic capacitance.

[0039] The present disclosure provides a technical solution for mitigating EIBD. More specifically, the present disclosure provides a method for mitigating undesired voltages that occur during operation of electric device applications, such as electric motors. Furthermore, the technical solution provided herein addresses the root cause of EIBD by minimizing or mitigating undesired voltages without implementing hardware that involves wear and tear on electric motor components.

[0040] In some aspects of the present disclosure, an electric motor can include an electrical circuit that can generate a voltage (e.g., an injection voltage) to mitigate undesired voltages. For example, a common-mode voltage generated by the switching operation of an inverter that supplies energy to the electric motor can result in an undesired voltage (shaft voltage) on the shaft of the electric motor. In some examples, the electrical circuit can generate an injection voltage (e.g., an undesired voltage that causes EIBD) that has an opposite polarity to the shaft voltage. For example, when the shaft voltage reaches a positive voltage, the injection voltage can reach a negative voltage with the same or similar absolute magnitude as the shaft voltage. Also, when the shaft voltage becomes negative, the injection voltage can become positive with the same absolute magnitude as the shaft voltage. In some embodiments, the injection voltage can be generated to maintain the shaft voltage below a threshold voltage that causes EIBD, such as a threshold voltage of approximately 3.5 V. As a result, the shaft voltage can be reduced to zero, near zero, or below the threshold voltage. This helps minimize or completely eliminate electric bearing damage.

[0041] In some embodiments of the present disclosure, one or more transformers are used as a source of injection voltage. For illustrative purposes, a conductor plate is capacitively coupled to the rotor, and the transformer receives its energy source through a conductive coupling with a winding neutral (e.g., a winding neutral of a winding coil) and ground (e.g., the chassis of the electric motor). For example, when the electric motor is operating, the conductor and rotor may be capacitively coupled. As a result, the transformer's energy source may be the connection between the winding neutral of the winding coil and a ground source (e.g., the chassis of the electric motor). By utilizing this energy source, the transformer generates an injection voltage that can be utilized to mitigate the shaft voltage.

[0042] One or more aspects of the present disclosure relate to a method for mitigating EIBD by minimizing or eliminating shaft voltage. In some embodiments, the method may include determining a parasitic capacitance of an electric motor. As disclosed herein, the parasitic capacitance is generated due to capacitive coupling between components of the electric motor. After determining the parasitic capacitance, the present disclosure provides a method for implementing a transformer and a conductor. More specifically, the present disclosure provides a method for determining the size of the conductor, parameters of the transformer, and the distance between the conductor and the rotor. In some embodiments, the transformer and the conductor are implemented on a printed circuit board (PCB). For example, one side of the PCB may implement a conductive material, and the other side of the conductive material may implement a transformer. In this example, the conductive material is capacitively coupled to the rotor and functions as a conductor. Furthermore, in this example, the transformer and the conductive material are connected by vias, so that the transformer can transfer energy from the via connection to the conductive material.

[0043] Some aspects of the present disclosure provide various transformer designs that can be implemented in electric motors. In some embodiments, the size of the transformer can be minimized by utilizing two or more transformers along with various filters (e.g., low-pass and high-pass filters). For example, two transformers can be implemented in the same circuit, with one transformer used for high-frequency energy signals and the other for low-frequency signals. This approach has the advantage of minimizing the size of the transformer circuit. For example, a single transformer that can cover both high and low frequencies may have a large form factor and may not be able to be implemented in an electric motor. However, using multiple transformers can reduce the form factor of the transformer circuit.

[0044] While various aspects are described according to exemplary embodiments and feature combinations, those skilled in the art will appreciate that the examples and feature combinations are exemplary in nature and should not be construed as limiting. More specifically, aspects of the present application may be applicable to various types of applications, and each application may require different specifications for the electric motor. For example, the specifications for an electric motor used in a fan are different from the specifications for an electric motor used in an electric vehicle. Therefore, the exemplary examples should not be construed as limiting.

[0045] FIG. 1 illustrates an example of a cutaway view showing one embodiment of an electric motor disclosed herein. As shown in FIG. 1, the electric motor can be assembled to a chassis 102, which can include a stator 104, a rotor 106, a shaft 108, and bearings 110. The stator 104 can include winding coils 112. In some embodiments, an alternating current (AC) can be applied to the winding coils 112 included in the stator 104, and the winding coils 112 can generate a magnetic field due to the received AC. In some embodiments, the AC is provided as a multi-phase waveform. For example, if there are three phases, the magnetic field generated in the winding coils can include three different magnetic fields, one for each phase. In some examples, the AC can be provided from an external power source, such as an inverter that connects to a battery, a power outlet, or the like. In some embodiments, the electric motor is connected to an inverter 150. For example, the inverter 150 is configured to provide AC to the electric motor by connecting to a ground source, such as the chassis 102. The inverter 150 can be configured to generate the required AC by converting DC received from an external source, such as a power outlet or a battery. The inverter 150 can be configured to generate AC waveforms with multiple distinct phases, such as three phases with each waveform (at the same frequency) shifted by 120 degrees. Additionally, the inverter's switching frequency can be correlated to the waveform's frequency. In some examples, the inverter's frequency is proportionally correlated to the rotational speed of the rotor 106 and shaft 108.

[0046] The applied voltage can generate a current. The current can generate a magnetic field. These magnetic fields can generate a rotating magnetic field based on their different phases. This rotating magnetic field can induce a current in the rotor 106, which can rotate due to the rotating magnetic field. In some embodiments, the shaft 108 can be assembled to the rotor 106, and rotating the rotor 106 can rotate the shaft 108. As further described in FIG. 1 , the shaft 108 and chassis 102 are assembled with bearings 110.

[0047] The electric motor 100 may further include a transformer 114, a capacitor 116, an insulator 120, and a conductor 122. As disclosed herein, these additional components can be utilized to mitigate EIBD. For example, the transformer 114 is connected between the winding neutral 124 and the conductor 122. Without being bound by theory, the neutral can act as a source with respect to ground because a source (e.g., a battery, a power outlet, etc.) can be capacitively coupled to ground due to the parasitic capacitance inherent between the physical conductors. In some examples, the conductor 122 and the rotor 106 are capacitively coupled during operation of the electric motor 100 (e.g., while the rotor 106 is rotating). In some examples, the transformer 114 can generate an injection voltage to mitigate the shaft voltage (e.g., the voltage between the shaft 108 and the chassis 102) and induce a current in the rotor 106 through the conductor 122. This injection voltage can mitigate the shaft voltage Vshaft (shown in FIGS. 2B and 3B). Shaft voltage mitigation is described in more detail below.

[0048] 1, rotor 106 and shaft 108 rotate by inducing a rotating magnetic field generated from winding coils 112, so these components do not come into physical contact. Thus, electric motor 100 may be a permanent magnet electric motor.

[0049] The electric motor 100 may be applied to an electric vehicle. However, the present disclosure does not limit the application of the electric motor 100, and the electric motor 100 may be applied to any suitable application.

[0050] 2A and 2B show two-dimensional views of a conventional electric motor 200. As shown in FIG. 2A, the conventional electric motor 200 can be mounted to a chassis 202, which can include a stator 204, a rotor 206, a shaft 208, and bearings 210. The stator 204 can include a winding coil 212. As shown in FIG. 2A, during operation of the electric motor 200, parasitic capacitance exists between the two components. For example, when power is applied to the electric motor 200 (e.g., power is applied from an inverter), the DC supplied to the inverter can generate a common-mode voltage between the winding coil 212 (e.g., the winding neutral of the winding coil) and ground (e.g., the chassis 202). This common-mode voltage can charge the parasitic capacitances Cwg, Cwr, Crg, and Cb shown in FIG. 2A. For example, the common-mode voltage can charge the parasitic capacitive coupling Cwg between the winding coil 212 and the chassis 202. The common-mode voltage can also charge the parasitic capacitive coupling Cwr between the winding coil 212 and the rotor 206. Furthermore, the common-mode voltage can charge the parasitic capacitive coupling Crg between the rotor 206 and the chassis 202 (e.g., the stator 204 is in physical contact with the chassis). In some embodiments, Crg is related to the induced current from the stator to the rotor. Furthermore, as shown in FIG. 2B, Crg and Cb are connected in parallel and in series with Cwr. Therefore, a higher value of Crg can result in a lower shaft voltage Vshaft. In some embodiments, charging Cwr and Crg can induce a voltage on the shaft 208 due to the induced current on the rotor 206. This induced voltage can charge the parasitic capacitive coupling Cb between the chassis 202 and the shaft 208. These parasitic capacitive couplings Cwg, Cwr, Crg, and Cb can generate an undesirable voltage Vshaft across the shaft, which can cause damage to the bearing 210. This damage is commonly referred to as EIBD.

[0051] 2A. As shown in FIG. 2B, portion 252 corresponds to winding coil 212, portion 254 corresponds to chassis 202, and portion 256 corresponds to rotor 206. During operation of electric motor 200, a voltage applied to winding neutral 224 from inverter 150 shown in FIG. 1 can generate a common-mode voltage Vcm. A portion of common-mode voltage Vcm can generate a shaft voltage Vshaft due to parasitic capacitance, as shown in FIG. 2B.

[0052] To mitigate the shaft voltage Vshaft generated by the parasitic capacitance, the present disclosure provides an electric motor 300 by implementing additional circuitry, conductors, and insulators, as depicted in Figure 3A. Figure 3A shows a two-dimensional view of the electric motor shown in Figure 1.

[0053] As shown in FIG. 3A , the chassis 302 of the electric motor 300 can be assembled with the stator 304, the rotor 306, the shaft 308, the bearings 310, and the winding coils 312. Additionally, the electric motor 300 can include a transformer 314, an insulator 320, and a conductor 322. In some embodiments, the transformer 314 can be configured to generate an injection voltage. The injection voltage can be configured to mitigate the shaft voltage, such that the injection voltage has an opposite polarity to the shaft voltage, thereby mitigate the shaft voltage. For example, during operation of the rotor 306 (e.g., while rotating the rotor), the conductor 322 can capacitively couple with the rotor 306 (e.g., capacitive coupling, Ccond). For example, the rotor 306 can generate an electric field that can couple with the conductor 322 during its rotation. The amount of capacitance Ccond can be determined based at least on the distance between the conductor 322 and the rotor 306. In some examples, the transformer 314 can receive an input from the winding neutral 324 and convert the input to an output between the conductor 322 and the chassis 302. In some embodiments, the output voltage can have an opposite polarity to the input voltage polarity. By utilizing this input power, the transformer 314 can generate an injected voltage (e.g., an output voltage). In some examples, the injected voltage Vinjected (the output of the transformer 314) can charge a capacitance Ccond that exists between the conductor 322 and the rotor 306. An induced current due to Vinjected can flow through Ccond, and this current and Ccond can generate a voltage drop across Ccond. Thus, in some embodiments, Ccond can be related to Crg, and therefore, the shaft voltage Vshaft can be reduced. In some examples, the distance between the conductor 322 and the rotor 306 determines the amount of current that flows through Ccond, and the distance can be determined based on Vshaft.

[0054] In some cases, the transformer 314 can be implemented as a circuit. For example, the transformer 314 can be integrated with a PCB and connected to the winding neutral 324 of the winding coil 312 and the chassis 302. In some cases, the circuit can include additional passive electrical components, such as resistors and / or capacitors. These electrical components can be determined based on the required output of the transformer. For example, if the transformer 314 is configured to operate in a particular frequency band, one or more of these electrical components can be implemented to function as a frequency filter (e.g., a high-pass filter or a low-pass filter). In some examples, the circuit can also include the transformer 314 and conductors 322. For example, one side of the PCB can include the conductor 322 layer, and the other side of the PCB can include the transformer 314. The electric motor 300 can also include an insulator 320.

[0055] FIG. 3B shows a schematic diagram of FIG. 3A. As shown in FIG. 3B, portion 352 corresponds to the winding coil 312, portion 354 corresponds to the chassis 302, portion 356 corresponds to the rotor 306, and portion 358 corresponds to the conductor 322. As shown in FIG. 3B, the transformer 314 can generate an injection voltage Vinjected. The injection voltage Vinjected has an opposite polarity to the common-mode voltage Vcm. Therefore, the shaft voltage Vshaft can be canceled (e.g., reduced) by applying the injection voltage Vinjected. In some embodiments, the amount of the injection voltage Vinjected can be adjusted based on the value of Ccond. Therefore, the distance between the conductor 322 and the rotor 306 can be determined based on the amount of the common-mode voltage Vcm and the shaft voltage Vshaft. For example, the capacitance of Ccond is inversely related to the distance between the conductor 322 and the rotor 306.

[0056] 4A and 4B illustrate an example comparison of shaft voltage Vshaft 420 (e.g., the voltage between the rotor and the chassis because the rotor and shaft are conductively coupled) during operation of an electric motor. FIG. 4A corresponds to the operation of electric motor 200 shown in FIGS. 2A and 2B. As shown in FIG. 4A, a portion of common-mode voltage 422, Vcm, such as shaft voltage (Vshaft), is induced in the rotor. For example, because common-mode voltage 422, Vcm, is generated by inverter 150 and averaged at winding neutral 224 (shown in FIG. 2A), FIG. 4A illustrates a similar pattern between common-mode voltage 422, Vcm, and winding neutral voltage 424 (e.g., the voltage appearing at winding neutral 224 in FIG. 2A). Electric motor 200 does not include a transformer utilized to mitigate shaft voltage Vshaft. Thus, as shown in FIG. 4A, voltage 410 generated at rotor 206 can have shaft voltage Vshaft 420. This shaft voltage Vshaft can cause EIBD.

[0057] FIG. 4B corresponds to the operation of the electric motor 300 shown in FIGS. 3A and 3B. As depicted in FIG. 4B, there is a common-mode voltage 452, Vcm, generated from a DC inverter (e.g., a power supply) connected to the electric motor 300 (shown in FIG. 3A). Furthermore, the common-mode voltage 452, Vcm, can have a pattern similar to the winding neutral voltage 454 (e.g., the voltage appearing at the winding neutral 324 in FIG. 3A from the inverter). As shown in FIG. 4B, the shaft voltage 450, Vshaft, caused by the common-mode voltage 452, Vcm, is mitigated by the injected voltage, Vinjected, as shown in FIG. 3B. Thus, as shown in FIG. 4B, the shaft voltage 450, Vshaft (e.g., the voltage at the rotor) can be near zero. In some embodiments, this voltage can be below a threshold voltage, such as a voltage that can cause EIBD.

[0058] In some embodiments, the transformer 314 can be designed to operate over a wide frequency range. For example, the bandwidth of the frequency range can be from tens of kilohertz to hundreds of megahertz. This frequency range can be determined based on the switching frequency of the inverter. In some embodiments, the transformer 314 designed to operate over a wide frequency range can have a larger form factor. Therefore, in some applications where the size of the electric motor is limited, a small form factor for the transformer 314 is desirable. The switching frequency of the inverter can be determined based on the particular application, and this disclosure does not limit the frequency range.

[0059] FIG. 5 illustrates an example of a circuit 500 with a smaller form factor. As shown in FIG. 5, the circuit 500 can include two transformers, T1 and T2. Each transformer can be configured to operate in a specific frequency band, and therefore the combined size of T1 and T2 can be smaller than a single transformer capable of operating over a wide frequency range. The circuit can receive input by connecting point A to the winding neutral 324 (shown in FIG. 3A) and point G to the chassis 302. The output of the circuit 500 can correspond to point G connected to the chassis 302 and point B connected to the conductor 322. Therefore, the output voltage of the circuit can generate a voltage opposite to the input voltage. Furthermore, the circuit 500 can include a combination of a low-pass filter and a high-pass filter. Therefore, the input signal (generated between points A and G) can be filtered and fed to one of the transformers T1 or T2 based on its frequency. For example, T2 may have more transformer coils than T1 and may be configured to convert low-frequency band signals, while T1 may be configured to convert high-frequency band signals. In this example, the combination of C1 and R1 may filter the low-frequency band of the input signal and provide the filtered signal to T1. The combination of R1 and C2 may filter the high-frequency band of the input signal and provide the filtered signal to T2. R2 may be implemented as an output load to generate an output voltage between points B and G. Therefore, by utilizing a combination of multiple small transformers and frequency filters, the form factor of the transformer may be minimized. This disclosure does not limit the values ​​of C1, C2, R1, R2, T1, and T2, and these values ​​may be determined based on a particular application.

[0060] Figure 6 illustrates an example of implementing one or more transformers in an electric motor assembly to reduce shaft voltage. Figure 6 is described with reference to Figures 1, 2A and 2B, 3A and 3B, and 7A-7C.

[0061] In block 610, the electric motor receives input energy from an inverter, such as inverter 150 shown in FIG. 1 . In some embodiments, an alternating current (AC) can be applied to winding coils 112 included in stator 104, which can generate a magnetic field due to the received AC. The AC is generated from an inverter, such as a switching inverter. For example, the inverter receives direct current (DC) from an external power source, such as a battery, and converts the DC to AC by switching it (e.g., turning the DC on or off) at various frequencies. Thus, the inverter's switching mechanism can generate AC waveforms of various frequencies and phases, and the rotational speed (e.g., rotor rotation) of the electric motor can be modulated by adjusting the frequency of the supplied AC.

[0062] In block 620, the shaft voltage can be determined by measuring the parasitic capacitances Cwg, Cwr, and Crg. These capacitances can vary based on the specific application, and those skilled in the art can measure these capacitances. For example, as shown in FIG. 7A, the total capacitance C1 can be measured, where C1 represents the combined capacitance of Cwg and Crg. Then, as shown in FIG. 7B, the total capacitance C2 can be measured, where C2 represents the combined capacitance of Cwr and Crg. The shaft voltage can be measured based on the measured common-mode voltage Vcm and the capacitances in FIGS. 7A and 7B.

[0063] In block 630, the electric motor determines one or more transformers to de-rate the shaft voltage. In some embodiments, the transformer 314 can be configured to generate an injection voltage, as shown in FIG. 3B. The injection voltage can be configured to de-rate the shaft voltage, such as an injection voltage with opposite polarity to the shaft voltage, thus de-rating the shaft voltage. The transformer can be designed based on this required injection voltage. In some embodiments, a single transformer can be implemented to generate the injection voltage. In some embodiments, multiple transformers can be implemented to reduce the form factor with a wide bandwidth. An example of implementing two transformers is shown in FIG. 5.

[0064] The determined transformer may be implemented in the electric motor at block 640. For example, the input of the transformer may be connected between the winding neutral 324 and the chassis 302, as shown in FIG. 3A. In another example, two transformers may be implemented in the electric motor, as described in FIG. 5.

[0065] Figure 8 illustrates an example of operating an electric motor such as that described in Figures 3A and 3B. The electric motor may implement circuitry configured to generate an injection voltage to mitigate the shaft voltage of the electric motor.

[0066] At block 810, the electric motor begins operation. The electric motor receives input energy from an inverter, such as inverter 150 shown in FIG. 1 . In some embodiments, an alternating current (AC) can be applied to winding coils 112 included in stator 104, which can generate a magnetic field due to the received AC. The AC is generated from an inverter, such as a switching inverter. For example, the inverter receives direct current (DC) from an external power source, such as a battery, and converts the DC to AC by switching it (e.g., turning the DC on or off) at various frequencies. Thus, the inverter's switching mechanism can generate AC waveforms of various frequencies and phases, and the rotational speed (e.g., rotor rotation) of the electric motor can be modulated by adjusting the frequency of the supplied AC.

[0067] In block 820, operation of the electric motor generates a common-mode voltage. The common-mode voltage may be generated by the inverter when performing switching operations. For example, as described in FIG. 4B, common-mode voltage 452 is generated at winding neutral 324 (shown in FIG. 3A).

[0068] Operation of the electric motor generates a shaft voltage in block 830. As depicted in FIG. 4A, the shaft voltage 420 can be a portion of the common-mode voltage 422.

[0069] In block 840, operation of the electric motor generates an injection voltage. In some embodiments, the circuit can include one or more transformers. In some embodiments, the transformer 314 (shown in FIG. 3A) can be configured to generate the injection voltage, as shown in FIG. 3B. The injection voltage can be configured to mitigate the shaft voltage, such as where the injection voltage has an opposite polarity to the shaft voltage, thus mitigate the shaft voltage. The transformer can be designed based on this required injection voltage. In some embodiments, a single transformer can be implemented to generate the injection voltage. In some embodiments, multiple transformers can be implemented to reduce the form factor with a wide bandwidth. An example of implementing two transformers is shown in FIG. 5.

[0070] When a feature or element is referred to herein as being "on" another feature or element, it may be directly on the other feature or element, or intervening features and / or elements may also be present. In contrast, when a feature or element is referred to as being "directly on" another feature or element, there may not be intervening features or elements. When a feature or element is referred to as being "connected," "attached," or "coupled" to another feature or element, it will also be understood that it may be directly connected, attached, or coupled to the other feature or element, or intervening features or elements may be present. In contrast, when a feature or element is referred to as being "directly connected," "directly attached," or "directly coupled" to another feature or element, there may not be intervening features or elements.

[0071] Although described or illustrated with respect to one embodiment, the features and elements so described or illustrated may apply to other embodiments. Those skilled in the art will also understand that a reference to a structure or feature being located "adjacent" to another feature may have portions that overlap or underlie the adjacent feature.

[0072] The terms used herein are for the purpose of describing particular embodiments and implementations only and are not intended to be limiting. For example, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It will be further understood that as used herein, the terms "comprises" and / or "comprising" specify the presence of stated features, steps, operations, processes, functions, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, processes, functions, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ."

[0073] In the above description and in the claims, phrases such as "at least one of" or "one or more of" may appear followed by a linked list of elements or features. The term "and / or" may also appear with a list of two or more elements or features. Unless implicitly or explicitly contradicted by the context of use, such phrases are intended to mean any of the listed elements or features individually, or any of the listed elements or features in combination with any of the other listed elements or features. For example, the phrases "at least one of A and B," "one or more of A and B," and "A and / or B" are intended to mean "A alone, B alone, or A and B," respectively. A similar interpretation is intended for lists containing more than two items. For example, the phrases "at least one of A, B, and C," "one or more of A, B, and C," and "A, B, and / or C" are intended to mean "A alone, B alone, C alone, A and B, A and C, B and C, or A, B, and C," respectively. Use of the term "based on" above and in the claims is intended to mean "based at least in part on," allowing for unrecited features or elements.

[0074] Spatially relative terms, such as "forward," "backward," "below," "belower," "lower side," "upper," and "above," may be used herein for ease of description to describe the relationship of one element or feature to another, as shown in the figures. It will be understood that spatially relative terms are intended to encompass different orientations of the device during use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as being "below" or "below" other elements or features will be oriented "above" the other elements or features due to the inverted state. Thus, the term "below" can encompass both an upward and downward orientation, depending on the reference point or orientation. The device may be otherwise oriented (rotated 90 degrees or to other orientations), and the spatially relative descriptors used herein will be interpreted accordingly. Similarly, terms such as "upwardly," "downwardly," "vertical," and "horizontal" may be used herein for descriptive purposes only, unless otherwise specified.

[0075] Although the terms "first" and "second" may be used herein to describe various features / elements (including steps or processes), these features / elements should not be limited by these terms as an indication of the order of the features / elements or whether one is primary over the other, unless the context dictates otherwise. These terms may be used to distinguish one feature / element from another. Thus, a first feature / element described could be referred to as a second feature / element, and similarly, a second feature / element described below could be referred to as a first feature / element without departing from the teachings provided herein.

[0076] As used in this specification and claims, including when used in the examples, unless expressly specified otherwise, all numbers can be read as if they were preceded by the word "about" or "approximately," even if the term does not explicitly appear. The phrase "about" or "approximately" can be used when describing a magnitude and / or location to indicate that the stated value and / or location is within a reasonably expected range of value and / or location. For example, a numerical value can have a value of + / -0.1% of the stated value (or range of values), + / -1% of the stated value (or range of values), + / -2% of the stated value (or range of values), + / -5% of the stated value (or range of values), + / -10% of the stated value (or range of values), etc. Any numerical value given herein should also be understood to include approximately or approximately that value unless the context dictates otherwise.

[0077] For example, if the value "10" is disclosed, "about 10" is also disclosed. Any numerical range recited herein is intended to include all subranges subsumed therein. As would be appreciated by one of ordinary skill in the art, when a value is disclosed, it is understood that "less than or equal to" that value, "greater than or equal to" that value, and possible ranges therebetween are also disclosed. For example, if a value "X" is disclosed, "less than or equal to X" and "greater than or equal to X" (e.g., where X is a number) are also disclosed. It is also understood that throughout this application, data may be provided in several different formats, and that this data may represent endpoints or starting points, and ranges for any combination of the data points. For example, if a specific data point "10" and a specific data point "15" may be disclosed, it is understood that greater than, greater than, less than, less than, and equal to 10 and 15, as well as between 10 and 15, may be considered disclosed. It is also understood that each unit between two specified units may also be disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 may also be disclosed.

[0078] While various exemplary embodiments have been disclosed, any of several modifications can be made to the various embodiments without departing from the teachings herein. For example, the order in which various described method steps are performed can be changed or rearranged in different or alternative embodiments, and in other embodiments, one or more method steps can be skipped entirely. Optional or desirable features of the various apparatus and system embodiments may be included in some embodiments and not in other embodiments. Therefore, the foregoing description has been provided primarily for illustrative purposes and should not be construed as limiting the scope of the claims and any particular embodiment or the specific details or features disclosed.

[0079] The examples and illustrations contained herein show, by way of illustration and not limitation, specific embodiments in which the disclosed subject matter may be practiced. As noted above, other embodiments may be utilized and derived, such that structural and logical substitutions and changes may be made without departing from the scope of the present disclosure. Such embodiments of the disclosed subject matter may be referred to herein, individually or collectively, by the term "invention" for convenience only, and no attempt is made to spontaneously limit the scope of this application to any single invention or inventive concept when multiple inventions are in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, any configuration intended, practical, or calculated to achieve the disclosed objectives, whether expressly stated or implied, may be substituted for the specific embodiment shown. The present disclosure is intended to cover any and all adaptations or variations of the various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon reviewing the above description.

[0080] The disclosed subject matter is provided herein with reference to one or more features or embodiments. Those skilled in the art will recognize and appreciate that, despite the detailed nature of the exemplary embodiments provided herein, changes and modifications may be applied to said embodiments without limiting or departing from the generally intended scope. These and various other adaptations and combinations of the embodiments provided herein are within the scope of the disclosed subject matter, as defined by the complete set of disclosed elements and features and their equivalents.

Claims

1. 1. An electric motor assembly comprising: A chassis, a stator configured to receive energy from an external energy source; a winding coil configured to generate a magnetic field, the winding coil mounted within the stator; a rotor magnetically coupled to the stator; a shaft connected to the rotor; a bearing connected between the shaft and the chassis; a conductor capacitively coupled to the rotor; a circuit configured to generate an injection voltage, the circuit being connected to the winding coil and the conductor; An electric motor assembly comprising:

2. The electric motor assembly of claim 1 , wherein the rotor is rotated by the magnetic field generated by the winding coils.

3. 10. The electric motor assembly of claim 1, wherein the energy is received from an inverter configured to supply an alternating current to the electric motor assembly, the alternating current including three waveforms having the same frequency.

4. 4. The electric motor assembly of claim 3, wherein each waveform is 120 degrees out of phase.

5. The electric motor assembly of claim 1 , wherein the circuit includes a transformer configured to generate injected energy by receiving current from a winding neutral.

6. 2. The electric motor assembly of claim 1, wherein the electric motor includes parasitic capacitances between the chassis and the winding coil, between the winding coil and the rotor, between the stator and the rotor, and across the bearings, and wherein a common mode voltage generates a shaft voltage between the shaft and the chassis.

7. The electric motor assembly of claim 6 , wherein the shaft voltage is reduced by the injected voltage.

8. 2. The electric motor assembly of claim 1, wherein the circuit comprises a first transformer, a second transformer, a low-pass filter, and a high-pass filter, the first transformer configured to transmit a high frequency band signal by receiving energy from the conductor and filtering the energy through the high-pass filter, and the second transformer configured to convert a low frequency band signal by receiving the energy from a winding neutral and providing the energy to the conductor.

9. The electric motor assembly of claim 1 , wherein the electric motor assembly is mounted in an electric vehicle.

10. 1. An electric motor assembly comprising: A chassis, a stator configured to receive energy from an external energy source; a winding coil configured to generate a magnetic field, the winding coil mounted within the stator; a rotor magnetically coupled to the stator; a shaft connected to the rotor; a bearing connected between the shaft and the chassis; a conductor capacitively coupled to the rotor; one or more transformers configured to generate an injection voltage, the one or more transformers connected to the winding coil and the conductor; An electric motor assembly comprising:

11. 11. The electric motor assembly of claim 10, wherein the transformer is integrated on a top side of a printed circuit board (PCB) and the conductors are integrated on a bottom side of the PCB.

12. The electric motor assembly of claim 11 , wherein the transformer receives energy from a winding neutral.

13. 11. The electric motor assembly of claim 10, wherein the electric motor includes parasitic capacitances between the chassis and the winding coil, between the winding coil and the rotor, between the stator and the rotor, and across the bearings, and the shaft voltage is generated from one or more of the parasitic capacitances.

14. The electric motor assembly of claim 13 , wherein the shaft voltage is reduced by the injected voltage.

15. The electric motor assembly of claim 10 , wherein the rotor rotates based on a switching frequency of an inverter, the inverter configured to supply AC to the electric motor assembly.

16. 11. The electric motor assembly of claim 10, wherein the received energy is an alternating current, and the alternating current includes three waveforms having the same frequency.

17. 17. The electric motor assembly of claim 16, wherein each waveform is 120 degrees out of phase.

18. 17. The electric motor assembly of claim 16, wherein the frequency is a switching frequency of an inverter configured to supply AC to the electric motor assembly.

19. 11. The electric motor assembly of claim 10, wherein the transformer is connected to a winding neutral.

20. The electric motor assembly of claim 10 , wherein the distance between the conductor and the rotor is determined based on a parasitic capacitance.

21. 1. A method for mitigating EIBD in an electric motor, comprising: starting operation of the electric motor, the electric motor being started by receiving an input at a phase of the electric motor; generating a common mode voltage; generating a shaft voltage that is a portion of the common mode voltage; generating an injection voltage to mitigate the shaft voltage, the injection voltage being generated from a transformer connected between a winding neutral and a conductor of the electric motor, an input of the transformer receiving an input signal from the winding neutral, an output of the transformer connected to the conductor located away from the rotor, the input and output of the transformer having opposite polarities; A method comprising:

22. 1. A circuit configured to mitigate EIBD in an electric machine, comprising: a PCB substrate; a transformer integrated on top of the PCB substrate, the transformer configured to generate an injection voltage; an input configured to provide an input voltage to the transformer, the input being received from a winding neutral of the electric machine; and an output of the transformer connected to a conductor of the circuit, the conductor being mounted on the bottom of the PCB substrate, the output and the conductor being connected through a via in the PCB substrate; The circuit includes:

23. 23. The circuit of claim 22, wherein the electric machine is an electric motor in an electric vehicle.

24. 23. The circuit of claim 22, wherein the output reduces voltages generated by parasitic capacitances of the electric machine.

25. 23. The circuit of claim 22, wherein the output reduces a shaft voltage.

Images