Induction motor

Abstract

An induction motor (100) is provided, comprising: a rotor (120); a stator (140); and a phase-shift oscillator (160). The stator comprises: a first winding (141); and a second winding (142) arranged at a first angle (101) with respect to the first winding. The phase-shift oscillator comprises: a transistor (170), which is a high electron mobility transistor, HEMT; and a phase-shift network (180). The first winding is connected to a first node (181) of the phase-shift network, and wherein the second winding is connected to a second node (182) of the phase-shift network, wherein the phase-shift oscillator is configured to provide a first phase electrical signal at the first node and a second phase electrical signal at the second node, wherein a difference between the first phase and the second phase corresponds to the first angle. An electrically powered aircraft propulsion system comprising the induction motor is also provided.

Description

Technical Field

[0001] This invention relates to induction motors and circuit systems for driving such motors. Background Technology

[0002] An induction motor, also known as an asynchronous motor, is a commonly used AC motor. It can be used as both a motor and a generator. The most common application of an induction motor is as an induction motor. Induction motors can be configured as single-phase or multi-phase motors. An induction motor typically consists of a stationary stator and a freely rotating rotor.

[0003] In an induction motor, the alternating magnetic field of the stator windings induces a current in the rotor. This induced current then generates a counteracting magnetic field and produces torque, causing the rotor to rotate. The rotor of an induction motor can be a squirrel-cage rotor or a wound-rotor relative to the stator.

[0004] Induction motors are used in electrically propelled vehicles such as trains and road vehicles. They can also be used in electrically propelled aircraft, particularly fixed-wing and rotary-wing aircraft.

[0005] The main problem with electric aviation is that induction motors cannot yet replace aircraft engines that use chemical fuels. Besides the need for improved batteries, the main issue with electric induction motors is that they typically have too low a power-to-weight ratio to be practically suitable for aircraft propulsion.

[0006] Single-phase induction motors face particular obstacles in this regard because they require large capacitors to achieve high power output and winding ratios. Pushing induction motors to higher power outputs could consequently reduce their power-to-weight ratio. Therefore, improvements are needed in the technological field. Summary of the Invention

[0007] The purpose of this invention is to at least alleviate some of the problems mentioned above.

[0008] According to a first aspect, an induction motor is provided, including a rotor, a stator, and a phase-shift oscillator. The stator includes a first winding and a second winding. The second winding is arranged at a first angle relative to the first winding. The phase-shift oscillator includes a transistor and a phase-shift network. The first winding is connected to a first node of the phase-shift network. The second winding is connected to a second node of the phase-shift network. The phase-shift oscillator is configured to provide a first-phase electrical signal at the first node and a second-phase electrical signal at the second node. The difference between the first phase and the second phase corresponds to the first angle.

[0009] The first and second windings can alternatively be referred to as the main winding and auxiliary winding, respectively. A phase-shifting oscillator can be understood as a circuit system including at least one transistor that shifts the phase of the alternating current between different nodes of the phase-shifting oscillator circuit system. Specifically, phase shifting is achieved between different nodes of a phase-shifting network that is part of the phase-shifting oscillator. The phase-shifting network can be a resistor-capacitor (RC) based phase-shifting network. Alternatively, the phase-shifting network can be understood as the feedback network of the phase-shifting oscillator. The transistor can be, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar junction transistor (BJT). The term "transistor" can be understood to refer to the transistor circuit system or amplifier section of the phase-shifting oscillator. Such a transistor circuit system may further include, for example, the desired drive and / or bias circuit system.

[0010] The phase-shift oscillator can be an inverter or an inverter network, such as an inverter or inverter network configured for at least six phases. The inverter or inverter network can include the previously mentioned transistors. The inverter or inverter network can include the previously mentioned phase-shift network. Alternatively, a first winding can be connected to a first node of the inverter network, and a second winding can be connected to a second node of the inverter, wherein the inverter network is configured to provide a first-phase electrical signal at the first node and a second-phase electrical signal at the second node, wherein the difference between the first phase and the second phase corresponds to the first angle.

[0011] During the operation of an induction motor, the rotor rotates relative to the stator. The rotor can be understood as being concentrically placed inside the stator. Induction motors operate by induction. When alternating current is supplied, windings arranged at specific relative angles to each other generate an alternating magnetic field. These fields induce a current in the rotor, which in turn generates its own magnetic field. The interaction between the rotor's magnetic field and the magnetic field of the stator windings is what causes the rotor to rotate. However, to provide a more practical self-starting induction motor, it may be necessary to convert or modulate the alternating magnetic field to form a rotating magnetic field (RMF). Conventionally, for a single-phase AC induction motor, the RMF is formed by connecting a capacitor in series with one of the stator windings.

[0012] The inventors have realized that the desired phase shift between the currents fed to the first and second windings can be achieved using a phase-shifting oscillator. Therefore, the induction motor can generate RMF (Regenerative Dynamics) without requiring, or at least with little reliance on, conventional capacitors connected in series with one of the windings (e.g., the second winding), allowing the induction motor to self-start when operating as a motor, i.e., converting electrical energy into rotational / mechanical energy. Typically, higher power induction motor operation and larger windings require higher capacitance from the series capacitors, which in turn results in physically larger capacitors, i.e., heavier and bulkier. Therefore, by eliminating or at least with little reliance on series capacitors, the power-to-weight ratio of the induction motor can be improved.

[0013] Conversely, this allows for the generation of smaller, more compact electric motors with a higher power-to-weight ratio through phase shifting of an active RC phase-shifting oscillator. For induction motors, the rotor's rotational speed can be controlled by an AC voltage that weakens or strengthens the magnetic field generated by the windings, thus making the motor run faster. Power can be calculated as rotational speed multiplied by torque. More windings and phases can benefit from producing greater torque at the same power cost.

[0014] Active RC phase-shift oscillators (i.e., those incorporating transistors) may be more advantageous for induction motors than passive RC phase-shift oscillators. In the case of passive phase-shift oscillators, achieving a 90-degree phase shift can be difficult, although it may provide 45 or 60 degrees at certain frequencies. A 30-degree phase shift can be achieved for a 6-phase induction motor according to the invention. Cascading passive filters together to produce filters of higher orders can be difficult to implement accurately. This is because the dynamic impedance of each RC filter order affects its adjacent RC networks. Additionally, factors such as temperature can affect the phase shift, and component tolerances can introduce deviations in practice. Using transistors for active phase shifting can be advantageous because the circuit can include smaller-value resistors and capacitors, i.e., it does not include large, bulky, high-inductance inductors that would increase the motor's weight and form factor.

[0015] The first angle can be 60 degrees. Such a phase shift can be easily achieved using an RC-based phase shift network and a phase shift oscillator.

[0016] The stator may further include a third winding arranged at a second angle relative to the first winding. The third winding may be connected to a third node of the phase-shifting network. A phase-shifting oscillator may be configured to provide a third-phase electrical signal at the third node. The difference between the first and third phases may correspond to this second angle.

[0017] The term "electrical signal" can refer to various types of electrical signals, such as voltage or current. Several advantages can be achieved by utilizing a third node in the phase-shift network and the corresponding third stator winding. For example, such a third winding can promote a more uniform radial distribution of the windings, which in turn can facilitate a reduction in the winding ratio or an increase in the rotational speed, torque, and / or output power of the induction motor. This can be understood as enabling the use of a three-phase stator and all its inherent benefits for a single-phase AC input signal.

[0018] The second angle can be 120 degrees. Such a phase shift can also be easily achieved using an RC-based phase shift network and a phase shift oscillator.

[0019] The first winding can be a bipolar winding. The second winding can also be a bipolar winding. This can be understood as the winding loop returning to the other side of the stator, that is, at a 180-degree angle to the initial portion of the winding. Currents flowing in different directions relative to the rotor through the initial and loop portions of one of the windings can generate two different magnetic fields 180 degrees apart in orientation.

[0020] Therefore, the further utility of each phase electrical signal can be discovered. By using bipolar windings, the RMF formation is more uniformly radially distributed in the stator. Alternatively, the third winding can also be a bipolar winding.

[0021] A transistor can be a power transistor. A power transistor can be understood as a transistor configured to operate at high current and high voltage. Typically, higher current may result in a stronger RMF (Regenerative Dynamics). Consequently, this may lead to an increase in the rotating / mechanical output power of an induction motor. A power transistor can be configured for a threshold voltage of at least 1200V. A power transistor configured for a 1200V threshold voltage can be configured to begin conducting at a gate voltage (e.g., gate-source voltage) of 1200V.

[0022] A transistor can be a high electron mobility transistor (HEMT). This should be understood as a transistor comprising at least two distinct bandgap semiconductor structures forming a heterostructure and a common interface between the at least two semiconductor structures. Such a transistor can alternatively be called a heterostructure field-effect transistor (HFET). A transistor should also be understood to include source contacts, drain contacts, and gate contacts. HEMTs can offer several advantages, such as higher power operation and higher frequency switching.

[0023] Regardless of how higher transistor frequency switching is achieved, it can be advantageous because it improves the oscillation stability of the phase-shift oscillator at higher frequencies. Therefore, the oscillation may be less saturated, and the output (i.e., the electrical signal at the node) will be less distorted. Higher frequency switching can reduce or completely eliminate the need for additional circuitry for stabilizing the electrical signal. When using transistors such as HEMTs, the output noise (in terms of the electrical signal) may be lower than when using BJTs or MOSFETs.

[0024] Transistors can contain GaN. GaN can refer to the compound semiconductor gallium nitride. A transistor or its structure can be essentially composed of GaN or contain at least some GaN. GaN provides several advantages to transistors containing it. These advantages may include higher power operation and higher frequency switching. Transistors containing GaN can be GaN-based HEMTs.

[0025] Active phase shifters can provide good frequency stability and a sinusoidal output signal (to the windings). If the transistor is a low-noise amplifier (such as an amplifier based on a GaN-based HEMT), this signal is low-noise or even distortion-free. GaN-based HEMTs can achieve high gain and low noise. This makes them suitable for high-voltage applications, such as 220V for an approximately 250kW AC induction motor. The frequency range can be from a few Hz to several hundred kHz. This frequency can be suitable for regulating the speed of the induction motor.

[0026] The first and second windings can be configured to generate a magnetic field when transmitting current.

[0027] The induction motor may further include a current rectifier configured for regenerative charging. The current rectifier can be understood as a current rectifier circuit system. Therefore, in addition to operating solely as a motor, the induction motor can also operate as a generator, for example, for recharging a battery.

[0028] The induction motor according to any one of claims may further include a drive circuit system for driving transistors of a phase-shift oscillator. Alternatively, the induction motor may include a drive circuit system for driving transistors of an inverter or inverter network.

[0029] The first winding and / or the second winding may include a superconductor.

[0030] Therefore, higher currents can be generated, which in turn can generate a larger magnetic field while reducing energy loss.

[0031] Superconductors can include V3Ga, Ga 1-2x Cu x As xN or NbN.

[0032] An induction motor can be configured to receive AC input. The input to be received can be understood as a single-phase AC input.

[0033] A phase-shift oscillator can be configured to provide a 6-phase electrical signal. In this context, a 6-phase electrical signal refers to multiple electrical signals comprising six phases. A first-phase electrical signal and a second-phase electrical signal can be included in the 6-phase electrical signal. Therefore, the phase-shift oscillator can be configured to provide a first-phase electrical signal, a second-phase electrical signal, a third-phase electrical signal, a fourth-phase electrical signal, a fifth-phase electrical signal, and a sixth-phase electrical signal. Each of the 6-phase electrical signals can be provided at a different node in the phase-shift network, i.e., at the first node, the second node, the third node, the fourth node, the fifth node, and the sixth node.

[0034] An induction motor may include six windings, each configured to receive a corresponding electrical signal from a six-phase electrical signal. These six windings may be bipolar windings. The six windings may be arranged around the stator and separated into consecutive windings at an angle. The phase difference between consecutive electrical signals in the six-phase electrical signal may correspond to the angle at which the corresponding winding is separated.

[0035] It should be understood that a phase-shift oscillator can be configured to provide at least six phase electrical signals. Therefore, more than six phases can be provided. Each phase can be provided to a corresponding winding.

[0036] An induction motor can be configured to receive a 3-phase input electrical signal. The 3-phase input electrical signal can be considered a 3-phase AC input. The induction motor can be configured to convert the 3-phase input electrical signal into a 6-phase electrical signal. Alternatively, the induction motor can be configured to convert the 3-phase input electrical signal into an electrical signal with a certain number of phases (the number of phases being a multiple of 3).

[0037] According to a second aspect, an electric aircraft propulsion system is provided. The electric aircraft propulsion system includes an induction motor according to the first aspect. The electric aircraft propulsion system further includes a bearing physically connected to and concentrically aligned with a rotor. The electric aircraft propulsion system further includes a battery electrically connected to the induction motor. The electric aircraft propulsion system further includes a control circuit system electrically connected to the induction motor, wherein the control circuit system is configured to control the induction motor.

[0038] Due to the improved power-to-weight ratio of induction motors, propulsion systems for electric aircraft can offer numerous advantages when based on such motors. The improved power-to-weight ratio can be transferred to the aircraft's propulsion system. This allows for a lighter propulsion system, and consequently, a lighter aircraft overall. This could be beneficial for extending the battery life and range of electric aircraft.

[0039] The further applicability of the present invention will become clear from the specific embodiments given below. However, it should be understood that while the specific embodiments and examples indicate preferred embodiments of the invention, they are given in an illustrative manner only, as various variations and modifications within the scope of the invention will become clear to those skilled in the art based on these specific embodiments.

[0040] Therefore, it should be understood that the present invention is not limited to the specific components of the described device or the operation of the described method, as such device and method can be modified. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0041] It must be noted that, unless the context clearly specifies otherwise, as used in this specification and the appended claims, the articles “a,” “an,” “the,” and “said” are intended to indicate the presence of one or more elements. Therefore, for example, references to “a unit” or “the unit” can include several devices, etc. Furthermore, the words “comprising,” “including,” “containing,” and similar expressions do not exclude other elements or steps. Attached Figure Description

[0042] The above and other aspects of the invention will now be described in more detail with reference to the accompanying drawings. These drawings should not be considered limiting; rather, they should be regarded as being for purposes of explanation and understanding.

[0043] As shown in the accompanying drawings, the dimensions of each layer and region may be exaggerated for illustrative purposes and are therefore provided to show the overall structure. Throughout the text, the same reference numerals refer to the same elements.

[0044] Figure 1 A schematic diagram of an induction motor is shown.

[0045] Figure 2 A circuit diagram of a three-phase induction motor based on a one-phase AC input signal is shown.

[0046] Figure 3 A cross-sectional view showing the stator-rotor configuration including more windings is shown.

[0047] Figure 4 The circuit diagram of a 6-phase induction motor based on a 3-phase AC input signal is shown.

[0048] Figure 5 A schematic diagram of an electric aircraft propulsion system is shown.

[0049] Figure 6 The circuit diagram of the induction motor is shown.

[0050] Figure 7 A schematic diagram of an induction motor is shown. Detailed Implementation

[0051] The invention will now be described more fully with reference to the accompanying drawings, in which presently preferred embodiments of the invention are illustrated. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to achieve thoroughness and completeness and to fully convey the scope of the invention to those skilled in the art.

[0052] For clarity, the term "horizontal" and similar terms may refer to the horizontal direction in a drawing when the paper is oriented vertically. The term "radial" and similar terms may refer to the feature and direction associated with the radius of a circular or cylindrical feature in a drawing.

[0053] Figure 1 An induction motor 100 is shown. The induction motor 100 is shown as including a rotor 120 and a stator 140. Both the rotor 120 and the stator are shown in a cylindrical shape. The rotor 120 is shown as being concentrically arranged within the stator 140.

[0054] Rotor 120 may include a conductive material, such as a metal. Rotor 120 may include one of copper, aluminum, and / or iron.

[0055] Rotor 120 can be a wound rotor or a squirrel-cage rotor. Rotor 120 may include a plurality of horizontally elongated conductive strips along the length of the cylinder of rotor 120. These conductive strips may be configured to induce current thereon when placed in an alternating or rotating magnetic field. Rotor 120 may include a plurality of laminated layers stacked along the length of the cylinder to reduce the effects of eddy current formation. The laminated layers may comprise steel.

[0056] Stator 140 includes a first winding 141 and a second winding 142. Stator 140 may include a third winding 143. Windings 141, 142, and 143 may be radially distributed uniformly or arbitrarily around the stator. Windings 141, 142, and 143 are shown as along... Figure 1 The longer cylinder of the larger stator 140 extends into the cylinder.

[0057] The second winding 142 is arranged at a first angle 101 relative to the first winding 141. The third winding 143 may be arranged at a second angle 102 relative to the first winding 141. The third winding 143 may be further arranged at the first angle 101 with the second winding 142. The first angle 101 may be 60 degrees. The second angle 102 may be 120 degrees.

[0058] Windings 141, 142, and 143 can be bipolar windings. In this way, windings 141, 142, and 143 can loop back to the other side of stator 140, that is, at a 180-degree angle to the initial portion of windings 141, 142, and 143. Figure 1 A bipolar winding arrangement with three main windings 141, 142, and 143 is shown. These main windings have corresponding windings arranged in a counter-polar or diametrically opposed manner. Including the main windings and the counter-polar windings... Figure 1 A total of six windings are shown, arranged at 30-degree angles. The main windings 141, 142, and 143, and their corresponding pole-pole windings, can be directly connected, allowing current to flow through them as a single conductor. The main windings 141, 142, and 143, and their corresponding pole-pole windings, can be arranged such that when the same current is conducted, the current will flow in the pole-pole windings in the opposite direction to that of the same current flowing through the corresponding main windings 141, 142, and 143. Therefore, at any given time, each main winding 141, 142, and 143, and its corresponding pole-pole winding, will generate relatively opposite magnetic fields.

[0059] The windings can be located in hollowed-out horizontal slots in the stator 140. The first winding 141, the second winding 142, and the third winding 143 can be configured to generate magnetic fields around the respective windings 141, 142, and 143 when transmitting current.

[0060] Windings 141, 142, and 143 may contain conductive materials, such as metals. Windings 141, 142, and 143 may, for example, contain copper or aluminum.

[0061] Any of windings 141, 142, and 143 may include a superconductor. The superconductor may include V3Ga or Ga... 1- 2x Cu x As x N or NbN.

[0062] The stator 140 may also include multiple laminated layers stacked along the length of the stator 140 cylinder to reduce the effects of eddy current formation. The laminated layers may contain steel.

[0063] The induction motor 100 further includes a phase-shift oscillator 160. The phase-shift oscillator 160 includes a transistor 170. The phase-shift oscillator 160 further includes a phase-shift network 180.

[0064] The phase-shifting network 180 includes a first node 181 and a second node 182. The phase-shifting network may further include a third node 183.

[0065] Phase shift network 180 is shown as Figure 1 The RC network in the diagram. Phase-shift network 180 may include three capacitors connected to three resistors. Nodes 181, 182, and 183 may be formed between each capacitor / resistor pair. In such a phase-shift network, the phase of each capacitor / resistor pair is shifted by 60 degrees. The phase difference between node 181 and node 182 can be 60 degrees. The phase difference between node 181 and node 183 can be 120 degrees or 60+60 degrees.

[0066] The induction motor 100 may further include a drive circuit system for driving the transistor 170 of the phase-shift oscillator 160, such as... Figure 2 As shown. The circuit section containing transistor 170 and the bias / drive circuitry system can be referred to as the amplifier section. The amplifier section can shift the phase of the output connected to the phase shift network 180 by 180 degrees relative to the phase of the electrical signal input at the VIN terminal. The induction motor can be configured to receive an AC input, for example, through the VIN terminal.

[0067] The phase-shift oscillator can be operated by adding the phase shifts of the phase shift and phase shift network 180 associated with the amplifier section to complete a full 360-degree phase shift, i.e., 180+60+60+60=360 degrees.

[0068] The bias / drive circuitry may include two resistors that act as a voltage divider for the gate of transistor 170. A resistor connected between the transistor's drain and the power rail VDD limits the drain current. Another resistor connected between the transistor's source and ground GND can be used to improve circuit thermal stability. A capacitor may be connected as a bypass capacitor between the transistor's source and GND.

[0069] The first node 181 is connected to the first winding 141. The second node 182 is connected to the second winding 142. The third node 183 can be connected to the third winding 143. Nodes 181, 182, and 183 can be directly connected to the corresponding windings 141, 142, and 143, such as... Figure 1 As shown. Alternatively, nodes 181, 182, and 183 can be indirectly (i.e., via resistors) connected to the corresponding windings 141, 142, and 143, as shown. Figure 2 As shown.

[0070] Phase-shift oscillator 160 is configured to provide a first-phase electrical signal at a first node 181 and a second-phase electrical signal at a second node 182. The difference between the first phase and the second phase corresponds to a first angle 101. Phase-shift oscillator 160 can be configured to provide a third-phase electrical signal at a third node 183. The difference between the first phase and the third phase corresponds to a second angle 102.

[0071] Transistor 170 can be a MOSFET or a BJT. Transistor 170 can contain Si, SiC, or Ge. Transistor 170 can be a power transistor. Transistor 170 can be a HEMT. Transistor 170 can contain GaN. Transistor 170 can contain AlGaN. Transistor 170 can be a GaN / AlGaN HEMT.

[0072] The induction motor 100 may further include a current rectifier. The current rectifier can be configured for regenerative charging. The current rectifier can be used to charge a rechargeable battery.

[0073] like Figure 3 As shown, an induction motor can have a ratio of Figure 1 Examples of rotor 120 and stator 140 configurations with windings 141, 142, and 143 are provided. Figure 3 The example shows a total of 12 windings arranged at 30-degree angles. This arrangement can be configured to receive a 6-phase electrical signal input on windings 141, 142, and 143. This example can be further configured with... Figure 1 The corresponding pole windings are in the same situation.

[0074] like Figure 3 The observed 6-phase induction motor with rotor-stator configuration can be based on three original phases: 0°(+), 120°(+), and 240°(+), with polarity indicated in parentheses. Each of these phases has opposite pole-pole windings at 180°(-), 300°(-), and 60°(-). Additional poles are introduced at: 30°(+) and 210°(-); 30°(+) and 270°(+) and 90°(-); and 330°(+) and 150°(-), i.e., a 30-degree phase shift from the original electrical signal phases at 0°(+), 120°(+), and 240°(+).

[0075] In this sense, only the phase of the positive polarity is taken into account. Therefore, the polarity and angle in the clockwise direction can be 0°(+), 30°(+), 60°(+), 90°(-), 120°(+), 150°(-), 180°(-), 210°(-), 240°(+), 270°(+), 300°(-), 330°(-), or in pairs: 0°(+) and 180°(-); 30°(+) and 210°(-), 60°(-) and 240°(+), 90°(-) and 270°(+), 120°(+) and 300°(-), 150°(-) and 330°(-).

[0076] As already described, such a 6-phase induction motor can be made from, for example... Figure 4 The circuit setup shown is used to provide an electrical signal input. Essentially, the input electrical signal can be a three-phase electrical signal VIN, in which the three phase signals can be shifted to additional phases by different phase-shifting oscillators comprising a separate phase-shifting network 180. The three original phases occurring at three different nodes of VIN can be 0 degrees, 120 degrees, and 240 degrees. Nodes 181 and 182 of the phase-shifting network 180 are shown to provide different phase electrical signals to the first winding 141 and the second winding 142. The phase difference between the first node 181 and the second node 182 can be 30 degrees. Figure 4 The circuit is shown as comprising three transistors 170. Each transistor is shown as being connected to a corresponding phase shift network 180 and a corresponding input line for receiving one of the three input phase electrical signals VIN.

[0077] Alternatively, the induction motor 100 can be implemented as a two-phase induction motor. A two-phase induction motor may require only one additional phase. This additional phase can be obtained by using a high-pass filter or a low-pass filter. A -3dB filter can produce a phase shift angle of 45 degrees.

[0078] Typically, by incorporating a switching amplifier or transistor, such a filter can require a smaller and less bulky high-inductance inductor, and the circuit can be more easily designed and better suited for induction motor frequencies below 10 kHz. Phase shift can be achieved using a high-pass filter with an oscillator frequency f (in Hz), given by the following formula:

[0079] f = (2πRC) -1 (2N) -0.5

[0080] ...where R is the resistance in ohms, C is the inductance in farads, and N is an integer representing the number of RC feedback stages.

[0081] According to the present invention, the phase shift is not only used to initiate the rotation of the rotor 120, but also to improve the power output of the already rotating rotor 120 by generating the RMF more uniformly with windings spaced 30 degrees apart (6 phases) compared to 60 degrees for 3 phases. The phase shift can be achieved by a 180-degree phase shift of the transistors and a low-pass filter (negative phase) or a high-pass filter (positive phase) between the windings.

[0082] Furthermore, cascading many RC networks can affect the accuracy of the phase-shift oscillator frequency, which must be kept accurate according to the physical / geometric angle spacing of the windings corresponding to the six-phase electrical signals.

[0083] Figure 6 A circuit diagram of an induction motor 100 is shown. The first winding 141, second winding 142, and third winding 143 of the stator 140 are schematically shown herein as load resistors. In the shown circuit diagram, the first winding 141 is connected to a first node 181 of the phase-shift network 180 via a totem-pole circuit 194. Similarly, the second winding 142 is connected to a second node 182 of the phase-shift network 180 via a totem-pole circuit 194. Similarly, the third winding 143 is connected to a third node 183 of the phase-shift network 180 via a totem-pole circuit 194. The totem-pole circuit 194 herein can act as an amplifier to amplify electrical signals from the first node 181, second node 182, and third node 183 of the phase-shift network 180. Each totem-pole circuit 194 includes a pair of transistors 170, such as a pair of complementary transistors. The transistors 170 can be high electron mobility transistors. The pair of transistors 170 can be configured to provide a push-pull output at the node between the transistors 170 in the pair. A push-pull output can provide electrical signals to the windings. The circuit diagram is configured to provide a first-phase electrical signal at a first node 181, a second-phase electrical signal at a second node 182, and a third-phase electrical signal at a third node 183. The difference between the first and second phases can correspond to an angle in which the second winding 142 is arranged relative to the first winding. The difference between the first and third phases can correspond to an angle in which the third winding 143 is arranged relative to the first winding. The circuit diagram further includes an amplifier 193. The amplifier 193 may include one or more transistors 170 herein. The transistors 170 in the amplifier 193 may be high electron mobility transistors.

[0084] As readily understood, the circuit diagram can be extended to a 6-phase induction motor 100. The phase shift network 180 can be extended to include a fourth, fifth, and sixth node. Similarly, the induction motor 100 may include fourth, fifth, and sixth windings respectively connected to the fourth, fifth, and sixth nodes of the phase shift network 180. Each winding may be connected to a corresponding node of the phase shift network 180 via a totem-pole circuit 194. The Nth phase electrical signal at the Nth node of the phase shift network 180 may differ from the first phase electrical signal at the first node 181 of the phase shift network 180 by the angle of arrangement of the Nth winding relative to the first winding.

[0085] As is easily understood, the circuit diagram can be expanded to have 6 phases or more.

[0086] Figure 7 A schematic illustration of an induction motor 100 is shown. As shown, a phase-shifting network 180 can be implemented in a field-programmable gate array (FPGA) 195. The windings of the stator 140 (in this case, the first winding 141, the second winding 142, and the third winding 143 of the stator 140) are connected to the FPGA 195 via a power bridge 196 (e.g., a gallium nitride power bridge 196). The power bridge 196 includes transistors 170, wherein the windings of the stator 140 are connected to nodes of the phase-shifting network 180 via the transistors of the power bridge 196. The transistors 170 of the power bridge 196 can be high electron mobility transistors.

[0087] Figure 5 A simplified top view of a twin-engine, propeller-powered fixed-wing aircraft is shown. The aircraft is shown as including an electric propulsion system 200. The electric propulsion system 200 includes an induction motor 100. The electric propulsion system 200 further includes a bearing 202 physically connected to and concentrically aligned with a rotor 120. The electric propulsion system 200 further includes a battery 204 electrically connected to the induction motor 100. The electric propulsion system 200 includes a control circuitry system 206 electrically connected to the induction motor. The control circuitry system 206 is configured to control the induction motor 100.

[0088] The electric aircraft propulsion system 200 can be configured to power a propeller or a turbine engine. The electric aircraft propulsion system 200 can be further configured to power the rotor of a rotorcraft.

[0089] Furthermore, variations of the disclosed embodiments are those that a person skilled in the art can understand and implement by studying the drawings, the disclosure, and the appended claims when practicing the claimed invention.

Claims

1. An induction motor comprising: a rotor; a stator; and a phase-shift oscillator wherein the stator comprises: ； a first winding; and a second winding arranged at a first angle relative to the first winding; wherein the phase-shift oscillator comprises: a transistor, the transistor being a GaN-based high electron mobility transistor (HEMT); and a phase-shift network; wherein the first winding is connected to a first node of the phase-shift network, and wherein the second winding is connected to a second node of the phase-shift network, wherein the phase-shift oscillator is configured to provide a first phase electrical signal at the first node and a second phase electrical signal at the second node, wherein a difference between the first phase and the second phase corresponds to the first angle, and wherein the phase-shift network is configured to generate a rotating magnetic field without using a series capacitor coupled to a stator winding. The first angle is 60 degrees.

2. The induction motor of claim 1, wherein, The stator further comprises a third winding arranged at a second angle relative to the first winding, wherein the third winding is connected to a third node of the phase-shift network, wherein the phase-shift oscillator is configured to provide a third phase electrical signal at the third node, wherein a difference between the first phase and the third phase corresponds to the second angle.

3. The induction motor of claim 1, wherein, The second angle is 120 degrees.

4. The induction motor of claim 3, wherein, The first winding is a bipolar winding, and wherein the second winding is a bipolar winding.

5. The induction motor of claim 1, wherein, The transistor is a power transistor.

6. The induction motor of claim 1, wherein, The first winding and the second winding are configured to generate a magnetic field when a current is transmitted.

7. The induction motor of claim 1, wherein, The current rectifier is configured for regenerative charging.

8. The induction motor of claim 1, further comprising a current rectifier, wherein, 9. The induction motor of claim 1, further comprising drive circuitry for driving the transistor of the phase-shift oscillator. The first winding and / or the second winding comprises a superconductor.

10. The induction motor of claim 1, wherein, 12. The induction motor of claim 1, configured to receive an alternating current input.

11. The induction motor of claim 10, wherein, The superconductor comprises V3Ga, Ga 1-2x Cu x As x N or NbN. The phase-shift oscillator is configured to provide a 6-phase electrical signal.

13. The induction motor of claim 1, wherein, 14. The induction motor of claim 1, configured to receive a 3-phase input electrical signal.

15. An electric aircraft propulsion system comprising: the induction motor of claim 1; a bearing physically connected to and concentrically aligned with the rotor; a battery electrically connected to the induction motor; and control circuitry electrically connected to the induction motor, wherein the control circuitry is configured to control the induction motor. ​ ​

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