Induction machine

Abstract

To provide an induction machine having an improved weight output ratio.SOLUTION: An induction machine comprising a rotor, a stator and a phase shift oscillator is provided. The stator includes a first winding and a second winding disposed at a first angle relative to the first winding. The phase shift oscillator comprises a transistor that is a high electron mobility transistor, and a phase shift circuit. The first winding of the induction machine is connected to a first node of the phase shift circuitry, the second winding is connected to a second node of the phase shift circuit, 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, and a difference between the first phase and the second phase matches the first angle. Also, an electric aircraft propulsion system comprising the induction machine is provided.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to induction machines and to drive circuits for such machines. [Background technology]

[0002] An induction machine is generally an alternating current (AC) powered electric machine, also known as an asynchronous machine. Induction machines may be used as both electric motors and generators. The most common use of induction machines is as induction motors. Induction machines may be configured as single-phase or polyphase machines. Induction machines generally have a fixed stator section and a freely rotating rotor section.

[0003] In an induction machine, current is induced in the rotor from the alternating magnetic field of the stator windings. The induced current then creates a counteracting magnetic field, producing torque and causing the rotor to rotate. The rotor in an induction machine may be a squirrel-cage rotor or a wound rotor relative to the stator.

[0004] Induction machines are used in electric propulsion vehicles such as trains and road vehicles. Induction machines may also be used for electric propulsion aircraft, particularly fixed-wing and rotary-wing aircraft.

[0005] A major problem in the electric aircraft industry is that induction machines are not yet able to replace chemically fueled aircraft engines. In addition to the need for improved batteries, a major problem with electric induction machines is that their power-to-weight ratios are generally too low to be practical for aircraft propulsion.

[0006] Single-phase induction machines are particularly hampered in that they require large capacitors for large power outputs and turns ratios. Pushing induction machines to higher power outputs can result in reduced power-to-weight ratios. Therefore, there is a need for improvements within the technology field. Summary of the Invention [Problem to be solved by the invention]

[0007] One object of the present invention is to alleviate at least some of the problems mentioned above. [Means for solving the problem]

[0008] According to a first aspect, an induction machine includes a rotor, a stator, and a phase-shift oscillator. The stator includes a first winding and a second winding. The second winding is disposed 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. A difference between the first phase and the second phase corresponds to the first angle.

[0009] The first winding and the second winding may alternatively be referred to as a main winding and an auxiliary winding, respectively. A phase-shift oscillator may be understood as an electrical circuit including at least one transistor that shifts the phase of an AC current between different nodes of a phase-shift oscillator circuit. In particular, the phase shift is realized between different nodes by a phase-shift network that is part of the phase-shift oscillator. The phase-shift network may be a resistor-capacitor (RC) based phase-shift network. The phase-shift network may alternatively be understood as a feedback network of the phase-shift oscillator. The transistor may be, for example, a metal-oxide semiconductor field-effect transistor (MOSFET) or a bipolar junction transistor (BJT). The term transistor may be understood to refer to a transistor electrical circuit or an amplifier section of a phase-shift oscillator. Such a transistor electrical circuit may further include, for example, a drive circuit and / or a bias circuit.

[0010] The phase-shift oscillator may be an inverter or inverter network, such as an inverter or inverter network configured with at least six phases. The inverter or inverter network may include the transistors described above. The inverter or inverter network may include the phase-shift network described above. Alternatively, the first winding may be connected to a first node of the inverter network, the second winding may be connected to a second node of the inverter, and the inverter network may be 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.

[0011] During the operation of an induction machine, the rotor rotates relative to the stator. The rotor may be understood as being concentrically positioned within the stator. Induction machines may operate by induction. When an AC current is input, windings positioned at specific relative angles to one another generate an AC magnetic field. These fields may induce currents in the rotor, which in turn generate their own magnetic fields. The interaction between the rotor's magnetic field and the stator windings produces rotor rotation. However, the AC magnetic field may need to be transformed or modulated to create a rotating magnetic field (RMF) to provide a more practical self-starting induction machine. Traditionally, for single-phase AC induction machines, the RMF is created by connecting a capacitor in series with one of the stator windings.

[0012] The inventors realized that a phase-shift oscillator may be utilized to achieve the required phase shift between the currents supplied to the first and second windings. Thus, the induction machine may generate RMF without requiring, or at least less reliant on, a traditional capacitor connected in series with one of the windings; for example, the second winding for an induction machine may be self-starting when operating as a motor, i.e., converting electrical energy into rotational / mechanical energy. Generally, higher-power induction machine operation and larger turns ratios require a larger series capacitor capacitance, which results in the capacitor being physically larger, i.e., heavier and bulkier. Therefore, by eliminating, or at least reducing the reliance on, the series capacitor, the power-to-weight ratio of the induction machine may be improved.

[0013] This, in turn, allows for smaller, more compact motors due to the phase shift of the active RC phase-shift oscillator. For induction motors, the rotor's rotational speed may be controlled by an AC voltage, which either weakens or strengthens the magnetic field generated by the windings, making the motor run faster. Power may be calculated by multiplying the rotor speed by the torque. Furthermore, windings and phases may be advantageous because they produce more torque for the same power cost.

[0014] Active RC phase-shift oscillators, i.e., using transistors, may be more advantageous for induction motors than passive RC phase-shift oscillators. Passive RC phase-shift oscillators may be difficult to achieve a 90-degree phase shift, while they may provide a 45- or 60-degree phase shift at a constant frequency. The phase shift for a six-phase induction motor in this invention may be a 30-degree phase shift. Cascading passive filters together to create a higher-order filter may be difficult to implement accurately because the dynamic impedance of each RC filter order affects its neighboring RC networks. In addition, for example, temperature may affect the phase shift, and in practice, component tolerances may produce deviations. Active phase-shift oscillators using transistors may be advantageous as they use circuits with small-value resistors and capacitors, i.e., they would not require large, bulky, high-inductance inductors, which would increase both the weight and form factor of the motor.

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

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

[0017] The term electrical signal may refer to various types of electrical signals, such as voltage or current. By utilizing a third node of the phase-shifting network and a matching third stator winding, several advantages may be realized. For example, such a third winding may promote a more uniform radial distribution of the windings, which may in turn be advantageous for reducing the turns ratio of the induction machine or increasing the rotational speed, torque, and / or output power. This may be understood as enabling the use of a three-phase stator with all its inherent advantages for a single-phase AC input electrical signal.

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

[0019] The first winding may be a bipolar winding. The second winding may be a bipolar winding. This may be understood as the windings looping back 180 degrees from the beginning of the winding on opposite sides of the stator. Two different magnetic fields oriented 180 degrees apart may be generated by currents flowing in different directions relative to the stator through the beginning and back-looping portions of one of the windings.

[0020] In this way, additional utility may be found in each phase electrical signal. By using a bipolar winding, the formation of the rotating magnetic field (RMF) is more uniformly distributed radially within the stator. Additionally, the third winding may be a bipolar winding.

[0021] The transistor may be a power transistor. A power transistor may be understood as a transistor configured to operate under high current and voltage. Generally, a higher current may generate a stronger rotating magnetic field (RMF), which may increase the rotational / mechanical output power of the induction machine. The power transistor may be configured with a voltage threshold of at least 1200V. A power transistor configured with a voltage threshold of 1200V may be configured to begin conducting at a gate voltage, e.g., a gate-source voltage of 1200V.

[0022] The transistor may be a high electron mobility transistor (HEMT), which should be understood as a transistor comprising at least two different bandgap semiconductor structures forming a heterostructure and a common contact between the at least two semiconductor structures. Such a transistor may also be referred to as a heterostructure field effect transistor (HFET). The transistor should also be understood as comprising source, drain, and gate contacts. HEMTs may offer various advantages, such as high power operation and higher switching frequencies.

[0023] Higher transistor frequency switching, regardless of how it is achieved, may be advantageous because it may improve the oscillation stability of the phase-shift oscillator at high frequencies. Thus, oscillations may be less saturated, resulting in less distortion of the output, i.e., the electrical signal at the node. Higher frequency switching may reduce or even completely eliminate the need for additional circuitry to stabilize the electrical signal. When using transistors such as HEMTs, the output may be less noisy (in terms of the electrical signal) than when using BJTs or MOSFETs.

[0024] The transistor may include GaN. GaN may refer to the compound semiconductor gallium nitride. The transistor or its structure may consist essentially of GaN or include at least some GaN. GaN offers several advantages to transistors that include it. These may include higher power operation and higher switching frequencies. The transistor that includes GaN may be a GaN-based HEMT.

[0025] The active phase shift may provide good frequency stability and a low-noise, possibly even undistorted, output sinusoidal electrical signal (to the windings) if the transistor is a low-noise amplifier, such as an amplifier based on a GaN-based HEMT. GaN-based HEMTs may achieve high gain and low noise. This may be suitable for high voltage applications, e.g., 220 V, for a ∼250 kW AC induction machine. The frequency range may be from a few Hz to several hundred Hz. The frequency may be suitable for regulating the speed of the induction machine.

[0026] The first winding and the second winding may be configured to generate a magnetic field when carrying a current.

[0027] The induction machine may further include a current rectifier configured for regenerative charging. The current rectifier may be understood as a current rectifying circuit. In this way, the induction machine may also operate as a generator, for example for recharging a battery, in addition to operating just as a motor.

[0028] The induction machine according to any of the claims may further comprise a drive circuit for driving the transistors of the phase shift oscillator, or alternatively, the induction machine may comprise a drive circuit for driving the transistors of the inverter or inverter network.

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

[0030] That way, higher currents and therefore larger magnetic fields may be generated with less energy loss.

[0031] Superconductors are V3Ga, Ga 1-2x Cu x As x It may contain N or NbN.

[0032] The induction machine may be configured to receive an AC input, which may be understood as a single-phase AC input.

[0033] The phase-shift oscillator may be configured to provide six-phase electrical signals. Here, six-phase electrical signals refer to a plurality of electrical signals having six phases. The first and second phase electrical signals may be included in the six-phase electrical signals. Thus, the phase-shift oscillator may be configured to provide a first, second, third, fourth, fifth, and sixth phase electrical signals. Each electrical signal of the six-phase electrical signals may be provided at a respective node of the phase-shift network, i.e., a first node, a second node, a third node, a fourth node, a fifth node, and a sixth node.

[0034] The induction machine may include six windings, each configured to receive a respective one of the six-phase electrical signals. The six windings may be bipolar windings. The six windings may be arranged around the stator with an angle separating successive windings. A phase difference between successive electrical signals of the six-phase electrical signal may correspond to the angle separating corresponding windings.

[0035] It will be appreciated that the phase shift oscillator may be configured to provide at least a six-phase electrical signal, and therefore more than six phases may be provided, each phase being provided to a respective winding.

[0036] The induction machine may be configured to receive a three-phase input electrical signal. The three-phase input electrical signal may be viewed as an AC input having three phases. The induction machine may be configured to convert the three-phase input electrical signal into a six-phase input electrical signal. The induction machine may be configured to convert the three-phase input electrical signal into an electrical signal having multiple phases, where the number of phases is a multiple of three.

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

[0038] Due to the improved power-to-weight ratio of induction machines, propulsion systems for electric aircraft based on such induction machines may offer many advantages. The improved power-to-weight may be carried over to the aircraft propulsion system, which may result in a lighter aircraft propulsion system and therefore a lighter aircraft overall. This may be advantageous in terms of improving battery life and the range of the electric aircraft.

[0039] Further scope of applicability of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, and various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

[0040] Therefore, it is to be understood that the invention is not limited to the particular components of the apparatus described, or to the acts of the method described for such apparatus, as such methods may vary. It is also to 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 should be noted that, as used in the specification and the appended claims, the articles "a," "an," "the," and "said" are intended to mean that there are one or more elements, unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices. Furthermore, the use of "comprising," "include," "containing," and similar expressions does not exclude other elements or steps. [Brief explanation of the drawings]

[0042] These and other aspects of the invention will now be described in more detail with reference to the accompanying drawings, which should not be considered restrictive, but instead for purposes of illustration and understanding.

[0043] As shown in the figures, the dimensions of layers and regions may be exaggerated for illustrative purposes and, thus, are provided to show the general structure. Like reference numerals refer to like elements throughout.

[0044] [Figure 1] Figure 1 shows a schematic diagram of an induction machine. [Figure 2] Figure 2 shows a circuit diagram of a three-phase induction machine based on a single-phase AC input electrical signal. [Figure 3] FIG. 3 shows a cross-sectional view of the stator-rotor configuration with further windings. [Figure 4] Figure 4 shows a circuit diagram of a six-phase induction machine based on a three-phase AC input electrical signal. [Figure 5] FIG. 5 shows a schematic diagram of an electric aircraft propulsion system. [Figure 6] Figure 6 shows a circuit diagram of an induction machine. [Figure 7] Figure 7 shows a schematic diagram of an induction machine. DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which presently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to those skilled in the art.

[0046] For clarity, the term horizontal and similar terms may refer to the horizontal direction in a drawing when the paper is in portrait orientation, and the term radial and similar terms may refer to features and orientations relative to the radius of a circular or cylindrical feature in a drawing.

[0047] 1 shows an induction machine 100. The induction machine 100 is shown to include a rotor 120 and a stator 140. The rotor 120 and the stator are both illustrated as being cylindrical in shape. The rotor 120 is shown to be concentrically disposed within the stator 140.

[0048] The rotor 120 may include a conductive material such as, for example, a metal. The rotor 120 may include one of copper, aluminum, and / or iron.

[0049] The rotor 120 may be a wound rotor or a squirrel-cage rotor. The rotor 120 may include a plurality of conducting bars extending horizontally along the cylindrical length of the rotor 120. These may be configured to have currents induced in them when placed in an alternating or rotating magnetic field. The rotor 120 may include a plurality of laminations stacked along the cylindrical length to mitigate the effects of eddy current formation. The laminations may include steel.

[0050] The stator 140 includes a first winding 141 and a second winding. The stator 140 may include a third winding 143. The windings 141, 142, 143 are evenly or optionally radially distributed around the stator. The windings 141, 142, 143 are shown as cylinders extending along the length of the larger stator 140 cylinder in FIG. 1.

[0051] The second winding 142 may be disposed at a first angle 101 relative to the first winding 141. The third winding 143 may be disposed at a second angle 102 relative to the first winding 141. The third winding 143 may also be disposed at the first angle 101 from the second winding 142. The first angle 101 may be 60 degrees. The second angle 102 may be 120 degrees.

[0052] The windings 141, 142, and 143 may be bipolar windings, whereby the windings 141, 142, and 143 may loop back 180 degrees from the opposite side of the stator 140, i.e., from the beginning of the windings 141, 142, and 143. FIG. 1 illustrates a dual-bipolar winding configuration with three corresponding main windings 141, 142, and 143, as well as antipodal or diametrically opposed windings. Counting the main and antipodal windings, FIG. 1 illustrates a total of six windings, spaced 30 degrees apart. The main windings 141, 142, and 143 and their corresponding antipodal windings may be directly connected, allowing current to flow through them as a single conductor. The main windings 141, 142, 143 and the corresponding antipodal windings may be arranged such that, when conducting the same current, the current flows in an opposite direction in the antipodal winding relative to the same current and direction through the corresponding main windings 141, 142, 143. In that way, the main windings 141, 142, 143 and the corresponding antipodal windings simultaneously produce relatively opposite magnetic fields.

[0053] The windings may be disposed in horizontal slots with holes in the stator 140. The first winding 141, the second winding 142, and the third winding 143 may be configured to generate a magnetic field around each winding 141, 142, 143 in an electrical circuit when an electric current is carried therethrough.

[0054] The windings 141, 142, 143 may include a conductive material such as, for example, a metal. The windings 141, 142, 143 may include, for example, copper or aluminum.

[0055] Any one of the windings 141, 142, and 143 may include a superconductor. The superconductor may include V3Ga, Ga 1-2x Cu x As x It may contain N or NbN.

[0056] The stator 140 may also include multiple laminations stacked along the cylindrical length of the stator 140 to mitigate the effects of eddy current formation. The laminations may include steel.

[0057] The induction machine 100 further comprises a phase shift oscillator 160. The phase shift oscillator 160 comprises a transistor 170. The phase shift oscillator 160 further comprises a phase shift network 180.

[0058] The phase shift network 180 includes a first node and a second node. The phase shift network may further include a third node 183.

[0059] Phase shift network 180 is shown in FIG. 1 as an RC network. 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 is shifted by 60 degrees for each capacitor / resistor pair. The phase difference between nodes 181 and 182 may be 60 degrees. The phase difference between nodes 181 and 183 may be 120 degrees or 60+60 degrees.

[0060] The induction machine 100 may further include a drive circuit for driving the transistor 170 of the phase shift oscillator 160, as shown in FIG. 2. The portion of the circuit including the transistor 170 and the bias / drive circuit may be referred to as an amplifier section. The amplifier section may shift the phase of the output connected to the phase shift network 180 by 180 degrees from the phase of the electrical signal input through the VIN terminal. The induction machine may be configured to receive an AC input, for example, through the VIN terminal.

[0061] The phase shift oscillator may operate by adding a phase shift to the phase shift of the phase shift network 180 in conjunction with the amplifier section to complete a full 360 degree phase shift, e.g., 180+60+60+60=360 degrees.

[0062] The bias / drive circuit may include two resistors acting as a voltage divider for the gate of transistor 170. One resistor is connected between the drain of the transistor and the power supply rail VDD to limit the drain current. The other resistor, connected between the source of the transistor and ground GND, may be used to improve thermal stability. A capacitor may be connected as a bypass capacitor between the source of transistor 170 and GND.

[0063] 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 may be connected to the third winding 143. The nodes 181, 182, and 183 may be directly connected to the respective windings 141, 142, and 143, as shown in FIG. 1. Alternatively, the nodes 181, 182, and 183 may be indirectly connected to the respective windings 141, 142, and 143 via resistors, as shown in FIG. 2.

[0064] The phase-shift oscillator 160 may be 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 the first angle 101. The phase-shift oscillator 160 may 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 the second angle 102.

[0065] Transistor 170 may be a MOSFET or a BJT. Transistor 170 may include Si, SiC, or Ge. Transistor 170 may be a power transistor. Transistor 170 may be a HEMT. Transistor 170 may include GaN. Transistor 170 may include AlGaN. Transistor 170 may be a GaN / AlGaN HeMT.

[0066] The induction machine 100 may further include a current rectifier, which may be configured for regenerative charging, and which may be used to charge a rechargeable battery.

[0067] As shown in FIG. 3, the induction machine may feature a rotor 120 and stator 140 configuration with additional windings 141, 142, and 143 than the example of FIG. 1. The example of FIG. 3 shows a total of 12 windings spaced 30 degrees apart. Such a configuration may be arranged to receive a six-phase electrical signal on windings 141, 142, and 143. This example may further feature corresponding antipodal windings, similar to the example of FIG. 1.

[0068] As shown in Figure 3, a rotor-stator six-phase induction machine configuration may be based on three initial phases with polarities in parentheses: 0°(+), 120°(+), and 240°(+). Each of these phases has windings with opposite and antipodal poles: 180°(-), 300°(-), and 60°(-). Further, poles may be introduced at 30°(+) and 210°(-); 30°(+), 270°(+), and 90°(-); and 330°(+) and 150°(-), i.e., a 30-degree phase shift from the initial electrical signal phases of 0°(+), 120°(+), and 240°(+).

[0069] Thus, only positive polarity counts as a phase. Therefore, clockwise polarity and angle may be 0°(+), 30°(+), 60°(+), 90°(-), 120°(+), 150°(-), 180°(-), 210°(-), 240°(+), 270°(+), 300°(-), 330°(-), or pairs of 0°(+) and 180°(-), 30°(+) and 210°(-), 60°(-) and 240°(+), 90°(-) and 270°(+), 120°(+) and 300°(-), 150°(-) and 330°(-).

[0070] Such a six-phase induction machine, as described above, may be supplied by an electrical signal input in a circuit configuration such as that shown in FIG. 4. Essentially, the input electrical signal may be a three-phase electrical signal V, with the three included phase signals being shifted to additional phases via different phase shift oscillators comprising separate phase shift networks 180. The first three phases appearing at three different nodes of V may be 0 degrees, 120 degrees, and 240 degrees. Nodes 181 and 182 of the phase shift network 180 are shown to supply 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 may be 30 degrees. The circuit diagram shown in FIG. 4 includes three transistors 170, each associated with a respective phase shift network 180 and a respective input line for receiving one of the three input phase electrical signals V.

[0071] Additionally, induction machine 100 may be implemented as a two-phase motor. A two-phase motor may require only one additional phase. Such an additional phase may be obtained using a high-pass or low-pass filter. A -3 dB filter creates a 45 degree phase shift angle.

[0072] Generally, by incorporating transistors such as switching amplifiers or such filters, smaller, less bulky high inductance inductors are required, making the circuit simpler in design and more suitable for induction machines with frequencies below 10 kHz. The phase shift is achieved by a high-pass filter with an oscillation frequency f in Hz given by f=(2πRC) ―1 (2N) ―0.5 R is a resistor with a resistance value of ohms, C is a capacitor with an inductance value of farads, and N is an integer indicating the number of RC feedback stages.

[0073] In accordance with the present invention, phase shifting is used to improve the power output of the rotor 120 not only while it is starting to rotate, but also once it is already rotating, by generating RMF more evenly in windings 30 degrees apart (60 degrees) compared to 60 degrees in three phases. The phase shifting may be achieved by a 180 degree phase shift of transistors and either low pass filters (negative phase) or high pass filters (positive phase) between the windings.

[0074] Furthermore, cascading many RC networks can affect the frequency accuracy of phase-shift oscillators, which must be precisely maintained according to the physical / geometric angular separation corresponding to the six-phase electrical signals.

[0075] FIG. 6 shows a circuit diagram of the induction machine 100 of the stator 140. The first winding 141, the second winding 142, and the third winding 143 are shown here schematically as load resistors. In the shown circuit diagram, the first winding 141 is connected to a first node 181 of a phase shift network 180 by a totem pole circuit 194. Similarly, the second winding 142 is connected to a second node 182 of the phase shift network 180 by the totem pole circuit 194. Similarly, the third winding 143 is connected to a third node 183 of the phase shift network 180 by the totem pole circuit 194. The totem pole circuit 194 here acts as an amplifier and may amplify electrical signals from the first node 181, the second node 182, and the 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 may be high electron mobility transistors. The pair of transistors 170 may be configured to provide a push-pull output at a node between the pair of transistors 170. The push-pull output may provide an electrical signal to the winding. 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 may correspond to an angle at which the second winding 142 is disposed relative to the first winding. The difference between the first and third phases may correspond to an angle at which the third winding is disposed relative to the first winding. The circuit diagram further includes an amplifier 193. Here, the amplifier 193 may include one or more transistors 170. Transistor 170 of amplifier 193 may be a high electron mobility transistor.

[0076] For clarity, the circuit diagram may be expanded to a six-phase induction machine 100. The phase shift network 180 may be expanded to include fourth, fifth, and sixth nodes of the phase shift network 180. Similarly, the induction machine 100 may include fourth, fifth, and sixth windings connected to the fourth, fifth, and sixth nodes of the phase shift network 180. Each winding may be connected to a respective node of the phase shift network 180 by a totem pole circuit 194. The Nth phase electrical signal at the Nth node in the phase shift network 180 may differ from the first phase electrical signal at the first node 181 in the phase shift network 180 depending on the angle of the Nth winding relative to the first winding.

[0077] For clarity, the circuit diagram may be extended to more than six phases.

[0078] 7 shows a schematic diagram of the induction machine 100. As shown, the phase shift circuitry 180 may be applied to a field programmable gate array (FPGA) 195. The windings of the stator 140, in this case a first winding 141, a second winding 142, and a third winding 143, are connected to the FPGA 195 by a power bridge 196, for example a gallium nitride power bridge. The power bridge 196 includes transistors 170, and the windings of the stator 140 are connected to nodes of the phase shift circuitry 180 by the transistors of the power bridge 196. The transistors 170 of the power bridge 196 may be high electron mobility transistors.

[0079] 5 shows a top view schematic of a two-engine, propeller-powered fixed-wing aircraft. The aircraft is shown equipped with an electric aircraft propulsion system 200. The electric aircraft propulsion system 200 includes an induction machine 100. The electric aircraft propulsion system 200 further includes an axle 202 physically connected to and concentrically aligned with the rotor 120. The electric aircraft propulsion system 200 further includes an electric battery 204 electrically connected to the induction machine 100. The electric aircraft propulsion system 200 includes a control circuit electrically connected to the induction machine. The control circuit 206 is configured to control the induction machine 100.

[0080] The electric aircraft propulsion system 200 may be configured to power a propeller or turbine type engine. The electric aircraft propulsion system 200 may be configured to power a rotor of a rotorcraft.

[0081] Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Claims

1. A rotor (120); a stator (140); a phase shift oscillator (160); The stator includes: a first winding (141); a second winding (142) disposed at a first angle (101) relative to the first winding; The phase shift oscillator comprises: a transistor (170), said transistor (170) being a high electron mobility transistor (HEMT); a phase shift network (180); the first winding is connected to a first node (181) of the phase shift network and the second winding is connected to a second node (182) 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, a difference between the first phase and the second phase corresponding to the first angle.

2. The induction machine of claim 1 , wherein the first angle is 60 degrees.

3. 3. The induction machine of claim 1, wherein the stator further comprises a third winding (143) disposed at a second angle (102) relative to the first winding, the third winding connected to a third node (183) of the phase shift network, the phase shift oscillator configured to provide a third phase electrical signal at the third node, a difference between the first phase and the third phase corresponding to the second angle.

4. 4. The induction machine of claim 3, wherein the second angle is 120 degrees.

5. 5. The induction machine according to claim 1, wherein the first winding is a bipolar winding and the second winding is a bipolar winding.

6. The induction machine according to any one of claims 1 to 5, wherein the transistor is a power transistor.

7. The induction machine according to any one of claims 1 to 6, wherein the transistor comprises gallium nitride (GaN).

8. The induction machine according to any one of claims 1 to 7, wherein the first winding and the second winding are configured to generate a magnetic field based on the transmission of a current therethrough.

9. An induction machine according to any preceding claim, further comprising a current rectifier, the current rectifier being configured for regenerative charging.

10. An induction machine according to any preceding claim, further comprising a drive circuit for driving the transistors of the phase shift oscillator.

11. An induction machine according to any preceding claim, wherein the first winding and / or the second winding comprises a superconductor.

12. The superconductor is V ３ Ga, Ga １-２ｘ Cu ｘ As ｘ The induction machine of claim 11 , comprising N or NbN.

13. An induction machine according to any preceding claim, configured to receive an AC input.

14. An induction machine as claimed in any preceding claim, wherein the phase shift oscillator is arranged to provide a six-phase electrical signal.

15. An induction machine according to any preceding claim, configured to receive a three-phase input electrical signal.

16. An induction machine (100) according to any one of claims 1 to 15; an axle (202) physically connected to and concentrically aligned with said rotor (120); an electric battery (204) electrically connected to the induction machine; A control circuit V electrically connected to the induction machine ３ Ga, Ga １-２ｘ Cu ｘ As ｘ N, or NbN circuit (206), the control circuit configured to control the induction machine; An electric aircraft propulsion system (200) comprising:

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