Power distribution in an electric machine with a commutated rotor winding - Patent application

Abstract

To provide an electric machine with rectified rotor windings and a control method thereof.SOLUTION: An electric machine includes a stator defining multiple stator poles with associated stator windings configured to receive a stator current. The electric machine also includes a rotor defining multiple fixed rotor poles with associated rotor windings, the rotor defining a field excited by magnetic fields produced by the stator windings when receiving the stator current to produce relative motion between the rotor and the stator and, the rotor being maintained in synchronicity with the magnetic fields produced by the stator during operation of the electric machine. The electric machine also includes a rectification system configured control against an alternating current being induced in the rotor poles as the field is excited by magnetic fields produced by the stator windings when receiving the stator current.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] Priority claims

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. patent application Ser. No. 63 / 059930, filed July 31, 2020, the entire contents of which are incorporated herein by reference.

[0002] Technical Field

[0002] The present invention relates to electric motors and generators. [Background technology]

[0003] background

[0003] Electric motors generally comprise a fixed component, often referred to as a stator, and a rotating component, often referred to as a rotor. An electric current is converted into an electromagnetic field, which generates a mechanical force, or torque, between the stator and rotor. The mechanical force, or torque, can be used to perform work. A generator operates on a similar principle, but by converting mechanical force into an electric current. The principles described herein are primarily described with respect to rotational force, or torque, but are also applicable to linear motors. In the case of a linear motor, in some implementations, the rotor acts as the fixed component and the stator acts as the component that is translated. Summary of the Invention [Problem to be solved by the invention]

[0004] overview

[0004] This disclosure describes techniques related to wirelessly transferring power within an electric machine. [Means for solving the problem]

[0005]

[0005] An exemplary implementation of the subject matter described within this disclosure is an electric machine having the following features: A stator defining a plurality of stator poles with associated stator windings; A rotor defining a plurality of fixed rotor poles with associated rotor windings, the associated rotor windings including a commutator and configured to be excited only by the stator; The rotor defining a rotor magnetic field that can be excited by a magnetic field generated by the stator windings to generate relative motion between the rotor and the stator; A controller detecting, through the stator windings, a magnetic field of the rotor measured relative to the nearest one of the rotor poles. Current phase shifter angle The controller is configured to send current depending on the operating conditions. Current phase shifter angle The controller is configured to adjust the magnitude of the delivered current depending on the operating conditions. During operation, the rotor is maintained in synchronization with the magnetic field generated by the stator windings.

[0006]

[0006] In some implementations, the stator windings include concentrated windings.

[0007]

[0007] In some implementations, the stator windings include distributed windings.

[0008]

[0008] In some implementations, the stator windings include salient pole windings.

[0009]

[0009] In some implementations, the rotor windings include concentrated windings.

[0010]

[0010] In some implementations, the rotor windings include salient pole windings.

[0011]

[0011] In some implementations, the rotor windings include non-lap windings.

[0012]

[0012] In some implementations, the commutator includes a diode.

[0013]

[0013] In some implementations, the commutation direction alternates between the rotor poles.

[0014]

[0014] In some implementations, the rotor includes a permanent magnet.

[0015]

[0015] In some implementations, the permanent magnets are substantially aligned with the rotor poles.

[0016] An exemplary implementation of the subject matter described in this disclosure is a method of controlling an electric machine. The method includes the following features: A stator winding of a stator is energized to generate a stator magnetic field within the stator. The stator magnetic field establishes a magnetic flux, which changes a corresponding rotor magnetic field within the ferromagnetic material in the rotor poles. The shift in the stator magnetic field generates a tangential force on the rotor. The generated tangential force causes the rotor to move. A commutator inhibits delay in the excitation of the magnetic flux in the air gap. The air gap is defined between the inner surface of the stator and the outer surface of the rotor. Decay of the magnetic flux in the rotor is resisted by current in the rotor winding in response to the magnetic field shift. The stator magnetic field and the rotor are maintained in synchronization with each other during operation. A current is passed through the stator winding and measured relative to the nearest one of the rotor poles. Current phase shifter angle The magnitude of the delivered current is adjusted depending on the operating conditions. Current phase shifter angle is adjusted depending on the operating conditions.

[0017]

[0017] In some implementations, maintaining the magnetic flux includes resisting a first change in the magnetic flux by inducing a first current in a first direction in the rotor winding until the first current decreases to zero, and maintaining the magnetic flux includes allowing a second change in the magnetic flux to induce a current in a second direction in the rotor winding.

[0018]

[0018] In some implementations, the opposing tangential forces are suppressed by a commutator.

[0019]

[0019] In some implementations, the commutator includes a diode.

[0020]

[0020] An exemplary implementation of the subject matter described in this disclosure is a wound field rotor synchronous machine having the following features: A stator defining a plurality of stator poles with associated stator windings; A rotor defining a plurality of rotor poles; The rotor configured to rotate synchronously with the stator; The rotor including a rotor winding associated with each of the rotor poles; The rotor windings configured to be excited by a magnetic field generated by the stator windings to generate a rotor magnetic field; The rotor windings including a commutator; Permanent magnets embedded within the rotor; A controller configured to excite the stator windings; The controller configured to measure, through the stator windings, a magnetic field measured relative to the nearest rotor pole; Current phase shifter angle The controller is configured to generate a stator magnetic field within the stator by sending control signals to the stator windings by sending currents through the Current phase shifter angle The controller is configured to adjust the magnitude of the delivered current depending on the operating conditions.

[0021]

[0021] In some implementations, the permanent magnets are not aligned with the rotor poles.

[0022]

[0022] In some implementations, the commutator includes a Schottky diode.

[0023]

[0023] In some implementations, the commutator is configured to reduce torque ripple during operation.

[0024]

[0024] In some implementations, the position sensor is configured to detect a position of the rotor relative to the stator. In such cases, the controller is further configured to receive a position stream from the position sensor. The position stream represents the rotor position. The controller is further configured to determine, in response to receiving the position stream, that torque ripple exists. In response to determining that torque ripple exists, the controller determines a torque ripple relative to the rotor poles. Current phase shifter angleThe controller is further configured to adjust the magnitude of the current in response to determining that torque ripple is present.

[0025]

[0025] The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, drawings, and claims. [Brief explanation of the drawings]

[0026] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] FIG. 1 is a schematic diagram of an example of an electric drive system. [Figure 2]

[0027] FIG. 2 is a schematic diagram of an exemplary power switch for an electrical winding. [Figure 3A]

[0028] 1 is a perspective view of an exemplary electric machine. [Figure 3B]

[0028] FIG. 1 is a side view of an exemplary electric machine. [Figure 3C]

[0029] 1 is a perspective view of an exemplary electric machine. [Figure 3D]

[0029] FIG. 1 is a side view of an exemplary electric machine. [Figure 4]

[0030] FIG. 1 is a side view of an exemplary electric machine. [Figure 5A]

[0031] FIG. 2 is a front view of an exemplary rotor coil. [Figure 5B]

[0032] FIG. 5B is a perspective view of the rotor coil of FIG. 5A. [Figure 5C]

[0033] FIG. 5C is a side view of the rotor coil of FIGS. 5A and 5B. [Figure 5D]

[0034] 10 is a graph showing various charge states and generated torque under a locked rotor condition (e.g., starting) and different phaser angles. [Figure 6]

[0035] FIG. 1 is a schematic diagram of an electric motor configured for control in accordance with the present disclosure. [Figure 7]

[0036] FIG. 1 is a block diagram of an exemplary controller that may be used in aspects of the present disclosure. [Figure 8]

[0037] 1 is a flowchart of a method that may be used in aspects of the present disclosure. [Figure 9A]

[0038] 1 is a flowchart of a method for responding to a torque increase request, according to an aspect of the present disclosure. [Figure 9B]

[0039] 10 is another flowchart of a method for responding to a torque increase request in accordance with an aspect of the present disclosure. [Figure 9C]

[0040] 1 is a flowchart of a method for starting an electric motor according to an aspect of the present disclosure. [Figure 9D]

[0041] 1 is a flowchart of a method for responding to a torque increase request, according to an aspect of the present disclosure. [Figure 10]

[0042] 1 is a graph of average magnetic field strength for various machine configurations. DETAILED DESCRIPTION OF THE INVENTION

[0027]

[0043] Like reference numbers and designations in the various drawings refer to like elements.

[0028] Detailed Description

[0044] The present disclosure relates to a wound-field synchronous motor with a rotor and stator that are directly electromagnetically coupled. The rotor coils may include a commutator, such as a diode. The addition of a commutator helps reduce torque ripple in the motor during operation. The rotor's rotor poles are topologically and electrically fixed to the rotor surface. The rotor is substantially energetically isolated from stator components other than the stator windings. That is, the rotor field is configured to be excited by the field generated by the stator windings. The stator field and rotor are maintained synchronized with each other during operation. During operation, a controller is configured to send current through the stator and actively adjust the magnitude and angle of the current in response to current or changing operating conditions. Such a motor can operate with the efficiency of a synchronous machine without requiring expensive rare-earth magnets or separate brushes or excitation circuits to excite the windings in the rotor.

[0029]

[0045] The electric machines described herein feature shorted concentrated windings that define the rotor poles. While shorted damper bars in the rotor have been proposed for transient damping, such damper bars tend to have limited frequency response. In contrast, shorted concentrated windings can provide effective transient damping over a wide range of frequencies during operation. Additionally, various electric machines described within this disclosure can take advantage of the inherent nonlinearities and asymmetries that occur during saturation of the rotor back iron, resulting in asymmetric inductance in the coils and resulting in net torque. Adding a commutator to the coils further increases this asymmetry and reduces torque ripple.

[0030]

[0046] Thus, the present disclosure provides subject matter for controlling electric machines or motors to achieve a variety of different goals, for example, to achieve desired operating goals without or with reduced reliance on rare earth elements or wear elements such as brushes or excitation circuits, or to improve other operating aspects of the system, such as generating a net torque designed to control undesirable torque ripple.

[0031]

[0047] 1 shows an electric drive system 100 including an electric motor 102 and an electric motor controller 104 coupled to the electric motor 102. The electric motor controller 104 is configured to operate the electric motor 102 to drive a load 110. The load 110 may be an additional gear train, such as a gear set, vehicle wheels, a pump, a compressor, or other electric motors that may be coupled together to operate in parallel.

[0032]

[0048] The motor 102 has an output shaft 107 that is rotatable relative to a motor housing 105, which serves as a datum for rotation and other motion of the motor components. In use, the output shaft 107 may be coupled to a load 110 to which the motor 102 may impart a rotational force when electrically activated by appropriate power and signals from a motor controller 104. The output shaft 107 may extend through the motor and may be exposed at both ends, meaning that rotational force may be transmitted at both ends of the motor. The motor housing 105 may be rotationally symmetric about the axis of rotation of the output shaft 107, but may also be of any external shape and may generally include means for securing the motor housing 105 to another structure to prevent housing rotation during motor operation.

[0033]

[0049] The electric motor 102 comprises an active magnetic component 106, such as a stator, and a passive magnetic component 108, such as a rotor. For purposes of explanation, the stator will be used as a representative example of an active magnetic component and the rotor will be used as a representative example of a passive magnetic component.

[0034]

[0050] The rotor 108 is associated with the stator 106 and may be disposed within the stator 106 (e.g., in an internal rotor radial gap motor) or parallel to the stator (e.g., in an axial gap motor or linear motor). As described in more detail below, appropriately controlled electrical activity in the stator 106 drives the motion of the rotor 108. The rotor 108 is rotationally coupled to the output shaft 107 such that any rotational component of the resulting rotor motion is transferred to and rotates the output shaft 107. The stator 106 is fixed to the motor 102 so that the rotor 108 moves about or parallel to the stator 106 during operation.

[0035]

[0051] As described throughout this disclosure, rectification system 112 may be included and implemented in a variety of different ways. For example, the rectification system may be configured to operate passively or actively. In some implementations, passive rectification may use one or more diodes. In some implementations, for active systems, active rectification may include one or more transistors, such as MOSFETs. In some implementations, rectification system 112 may be configured as a half-wave rectifier when using passive components, such as one or more diodes. In some implementations, rectification system 112 may be configured as a full-wave rectifier when using active rectification, for example.

[0036]

[0052] The inclusion of a commutation system 112, whether active or passive, can further mitigate torque ripple by controlling the AC components (specifically, negative current components) in the rotor coils or windings that may be present under excitation conditions. The AC components are generated during the charge phase (low Current phase shifter angle ) often occurs during the coil current flow, resulting in a decrease in the sheet current density. Rectification essentially eliminates this component, allowing the coil to Current phase shifter angle In some implementations, a high Current phase shifter angle is greater than 45 degrees, 65 degrees, or 75 degrees.

[0037]

[0053] The asymmetric electrical resistance of a commutated system allows for faster decay of current in rotor topologies (compared to non-commutated systems). For example, in a fractional slot stator, which may have salient poles, faster decay may be desirable to aid the charging or flux injection cycle and limit torque ripple. In a machine with a commutated rotor with a unidirectional passive circuit, for example a single diode, the winding current must be zero in order for flux to be injected into the rotor. Low Current phase shifter angle By oscillating at angles (e.g., less than 45 degrees, less than 35 degrees, or less than 15 degrees), the rotor current can be rapidly decayed to inject more flux into the system or to effectively field weaken the rotor for certain operating conditions (e.g., high speed or low torque operation).

[0038]

[0054] This disclosure also describes a linear electrical load 114, such as an electrical resistor, or a nonlinear electrical load, such as an avalanche diode or a voltage suppression gas discharge tube, that works in parallel with the commutation system to facilitate decay of rotor current before charging and limit damage caused by overvoltage discharge. In some implementations, the one or more linear loads 114 include an electrical resistor having a resistance greater than 100 ohms, 150 ohms, 300 ohms, or 1,000 ohms. In some implementations, the gas discharge tube or avalanche diode has a reverse breakdown voltage greater than 50 volts, 100 volts, 200 volts, 400 volts, 600 volts, or 800 volts, and a response time less than 10 ms, 5 ms, 2 ms, 0.5 ms, or 0.1 ms.

[0039]

[0055] Current flowing through a loop of wire creates a substantially uniform magnetomotive force (MMF), resulting in a motor pole within the wound or enclosed area. In a typical electric motor, such a loop has a diameter sufficient to carry the desired current load, but is thin enough that the skin depth at the driving frequency penetrates the loop completely. To increase the pole field strength, multiple turns, i.e., overlapping loops of wire, may be used. This topology is generally referred to as a wound-field pole. A collection of such overlapping loops is referred to as a coil. For purposes of this disclosure, multiple coils acting together within a stator or rotor are referred to as a winding. In some instances, the coils may overlap and surround multiple teeth on either the rotor or stator. Such lap-wound coils may be referred to as an armature or distributed winding. The magnetic pole is the magnetic center of the distributed winding, and therefore, the magnetic pole can move relative to the individual coils within such a distributed winding in response to the driving current passing through the winding.

[0040]

[0056] As examples described in more detail throughout this disclosure, the stator 106 defines a plurality of stator poles with associated electrical windings, and the rotor 108 includes a plurality of rotor poles. As examples described in more detail throughout this disclosure, the rotor 108, together with the stator 106, defines a nominal air gap between the stator poles and the rotor poles. The rotor 108 is movable relative to the stator 106 along the direction of motion.

[0041]

[0057] FIG. 2 illustrates another exemplary power switch 200 for an individual electrical winding 132. The power switch 200 may include an H-bridge circuit including four switching elements 202a, 202b, 202c, and 202d in an H-shaped configuration centered around the electrical winding 132. The switching elements 202a, 202b, 202c, and 202d may be bipolar or FET transistors. Each switching element 202a, 202b, 202c, and 202d may be coupled to a corresponding diode D1, D2, D3, and D4. The diodes are called catch diodes and may be Schottky diodes. The top end of the bridge is connected to a power source, e.g., a battery Vbat, and the bottom end is connected to ground. The gates of the switching elements 202a, 202b, 202c, and 202d may be coupled to the winding controller 130, which is operable to send corresponding control voltage signals to each switching element 202a, 202b, 202c, and 202d. The control voltage signal can be a DC voltage signal or an AC (alternating current) voltage signal.

[0042]

[0058] Switching elements 202a, 202b, 202c, and 202d can be individually controlled by motor controller 104 and can be turned on / off independently. In some cases, when switching elements 202a and 202d are turned on, the left stator lead is connected to a power source and the right stator lead is connected to ground. Current begins to flow through the stator, energizing electrical winding 132 in a forward direction. In some cases, when switching elements 202b and 202c are turned on, the right stator lead is connected to a power source and the left stator lead is connected to ground. Current begins to flow through the stator, energizing electrical winding 132 in the opposite, reverse forward direction. That is, by controlling the switching elements, electrical winding 132 can be energized / actuated in either of two directions. While primarily shown and described using a single-phase H-bridge configuration, a typical six-switch inverter system can be used with a polyphase machine without departing from this disclosure.

[0043]

[0059] As described in further detail throughout this disclosure, the motor controller 104 may be configured to sequentially operate the switches 134 or 200 for corresponding pole excitation duty cycles to generate magnetic flux across the air gap between the stator poles and the rotor poles. The switches may be controlled to sequentially energize the stator poles to generate localized attractive forces that pull the rotor. Such sequential excitation (or actuation) may cause the rotor 108, output shaft 107, and load 110 to rotate.

[0044]

[0060] The components and controls of an electric motor may be discussed relative to the D-axis 312 (illustrated in FIG. 3) and Q-axis of the rotor and / or stator of the motor. The direct axis, or D-axis 312, in an electric motor may be defined as the centerline of the poles 308 perpendicular to the air gap 314 and may apply to either the stator poles 411 (see FIG. 4) or the rotor poles 408. The rotor may be characterized by the D-axis 312 at each pole when viewed in a synchronous reference frame. In a wound rotor, the D-axis 312 is the center point of the resulting magnetic center of the coil or field winding, whether the field winding is concentrated in a single large slot or spans multiple small slots. The stator poles may be similarly characterized.

[0045]

[0061] The Q axis is perpendicular to the D axis (i.e., 90 degrees electrically) in the magnetic reference frame. In general, forces along the Q axis generate electromotive forces, such as torque. Topologically, the Q axis of a rotor or stator is generally located directly between two magnetic poles.

[0046]

[0062] In systems where the control signal can be converted into DQ axis components, a third z-axis component also exists, which can be described as a signal or magnetic quantity that does not map directly to the D or Q axes, for example, a component orthogonal to the plane in which the Q and D components can be determined.

[0047]

[0063] Current phase shifter angle 318 is the relative angle of the rotor pole D-axis 312 with respect to the magnetic center of the stator (as illustrated in FIGS. 3A and 3B). Current phase shifter angle indicates that the stator magnetic center leads the rotor poles in the direction of motion. As a result of this situation, the stator magnetic center "pushes" the rotor poles towards the stator magnetic center. Similarly, a negative Current phase shifter angle indicates that the stator magnetic center is lagging behind the rotor poles. This situation "pushes" the rotor poles in the opposite direction. Current phase shifter angle 318 can be used in braking situations. In some implementations, the angle is greater than 90°. Current phase shifter angle 318 can be used. Current phase shifter angle 318 can "push" adjacent magnetic poles in the direction of motion. Current phase shifter angle 318 can be used to "push" adjacent poles in opposite directions, such as during a braking operation. Current phase shifter angle The conversion of 318 can be done using the following formula: θe=(P / 2)θm (1) θe is the synchronous reference frame Current phase shifter angle where P is the number of stator poles and θm is the Current phase shifter angle is. Current phase shifter angle Regardless, the D-axis component can be separated into a D-axis component and a Q-axis component. Generally, in the motors and generators described herein, the D-axis component acts to "charge" or modulate the magnetic field in the rotor poles, and the Q-axis component acts to apply a force or torque to the rotor poles. Throughout this disclosure, references will be made to the D-axis component and Q-axis component, depending on the operating conditions. Current phase shifter angle 318 and Current Phase Shifter Amplitude The regulation of both is described in detail.

[0048]

[0064] for example, Current phase shifter angle , duty cycle, and D-axis to Q-axis current injection can all be varied. In some examples, an increase in instantaneous D-axis current relative to the Q-axis current can be achieved by at least 5%, 10%, 20%, or 30% during the D-axis injection period. In some examples, during an injection cycle, the resulting Current phase shifter angleThe decrease in the charge current may be achieved during the injection cycle, for example, by 5 to 60 degrees, 10 to 50 degrees, 15 to 45 degrees, or 22.5 to 67.5 degrees. In some examples, injection pulse widths of 2 to 70 ms, 5 to 50 ms, or 10 to 25 ms may be used. In some examples, charge duty cycles of 5%, 10%, 15%, or 25% of the total operating time may be used. In some examples, the decrease in the charge current is determined by the rotor current decreasing to zero. Current phase shifter angle The transition time from D-axis injection to normal operation is 500 μs to 15 ms, 2 ms to 12 ms, or 4 ms to 10 ms. Current phase shifter angle is changed by less than 15 degrees, less than 10 degrees, or less than 5 degrees. In some examples, the magnitudes of the D-axis and Q-axis are simultaneously changed by at least 5%, 10%, 20%, or 30% during the D-axis injection period. The system may be operated as a current control or a voltage control. For example, regardless of the specific operating parameters, the signal may be injected through a current source inverter with the variance of the current injection ripple magnitude controlled to be within a desired tolerance.

[0049]

[0065] As described throughout this disclosure, the coil structure on the rotor receives power / signals from the stator via inductive coupling that includes at least one loop centered on a rotor pole. In some implementations, the rotor coil for the conductive loop forms a capacitance, and in some implementations, the capacitance is formed, inserted, or defined by a specific portion of the rotor coil or conductive loop. In some implementations, the rotor coil or conductive loop includes a resonant frequency. In some implementations, the resonant frequency of the rotor coil is within the permeability range of the magnetic pole or rotor coil material.

[0050]

[0066] In operation, the rotor poles can be flux-injected via the stator D-axis signal, and the coil structure resists the flux change in the poles, causing current to flow. The rotor Q-axis signal generates torque in the flux-injected machine. In some topologies, for example, salient-pole winding synchronous machines, the maximum torque per ampere (MTPA) can be between 60 and 90 degrees. Current phase shifter angle For given operating conditions (e.g., torque and speed), the controller calculates: Current phase shifter angle The MTPA (e.g., through a look-up table or model-based estimator) is established, which includes a combination of the D-axis current and the Q-axis current (main control part) that establishes Current phase shifter angle may be modulated or oscillated to periodically maintain a desired level of rotor flux, which may be monitored by an observer or estimator, or established by a model-based approach. As the D-axis is modulated to increase rotor flux, the magnitude of the Q-axis current is modulated proportionally to limit torque ripple and Current phase shifter angle may suppress the adverse effects of changes in Current phase shifter angle The change in

[0051]

[0067] 3A and 3B are perspective and side views of an exemplary electric machine 300. The electric machine 300 includes a stator 302 that defines multiple stator poles with associated stator windings 304. A "motor pole" may be described as a topological section of either the stator or rotor that emits magnetic flux of a single polarity across the air gap at a given time. When determining the number or location of motor poles, the magnetic flux carried by the stator or rotor back iron is considered. Magnetic poles are generally characterized by regions of high magnetic field that can exceed 5,000 gauss. Magnetic poles may originate from permanent magnets or electromagnetic fields. While the number of stator or rotor poles is often fixed at the time of manufacture, in some implementations described herein, the number of poles on the rotor, stator, or both can be changed during operation.

[0052]

[0068] While the stator 302 illustrated herein is shown as having distributed windings 304, salient, concentrated, and / or non-lapped stators may similarly be used without departing from this disclosure. The rotor 306 defines a plurality of rotor poles 308 with associated rotor coils 310. While the illustrated embodiment includes one-third rotor teeth compared to the stator teeth, other ratios may be used without departing from this disclosure; for example, the rotor may include one-half the number of teeth present on the stator. In some implementations, the rotor may include one-quarter the number of teeth present on the stator. Other ratios of rotor teeth to stator teeth may be used without departing from this disclosure, regardless of whether salient, concentrated, or distributed stator windings are used.

[0053]

[0069] As shown, each of the rotor coils 310 is shorted to a commutator 311. While illustrated with a commutator for each coil 310, other configurations may be used without departing from this disclosure. For example, multiple rotor coils may be electrically coupled in series or parallel to a single commutator. In some implementations, the commutator 311 may include a diode. Several types of diodes may be used, such as p-n junction diodes, gas diodes, Zener diodes, or Schottky diodes. In some implementations, if a Schottky diode is used, the Schottky diode may be a silicon carbide diode. The diode selection depends on various factors, including voltage drop, reverse voltage breakdown, and recovery time. Different diodes may be used depending on the desired operating conditions. Although several types of diodes are listed, other diodes may be used without departing from this disclosure. The commutator may pass current in only one direction through each of the rotor coils 310.

[0054]

[0070] The rotor poles 308 are topologically and electrically fixed to the rotor surface. A fixed-pole rotor is one in which the poles are topologically and electromagnetically fixed or held stationary relative to a synchronous reference frame; for example, rotor 306 is a fixed-pole rotor. That is, rotor 306 always rotates at substantially the same speed as, or synchronous with, the drive frequency provided by the stator (allowing for inherent levels of torque ripple). The synchronous reference frame is the same as the magnetic reference frame. For this reason, fixed-pole motors are often referred to as "synchronous" motors. Wound-field rotors, surface permanent magnet rotors, reluctance motors, and interior permanent magnet rotors are all examples of fixed-pole rotors. Fixed-pole rotor designs maximize the use of ferromagnetic material in the rotor's D-axis 312 region (the center of the rotor poles) and, in the case of wound-field rotors, ensure that the effective magnetic center coincides with the D-axis 312. As a result, a fixed pole rotor is considered more efficient than a moving pole rotor for a given size and power rating, but the fixed pole rotor has the disadvantage of being unable to maintain constant rotational speed under dynamic load conditions and dynamic operating speeds. Current phase shifter angle For example, accelerating or maintaining the speed of a motor during load changes can be difficult to control based on input from the position sensor 316. Current phase shifter angle 318, current magnitude, and / or drive frequency. The concepts described herein are primarily applicable to synchronous machines in which the stator field and rotor, e.g., rotor 306, remain synchronized with one another during operation.

[0055]

[0071] In contrast, the poles of a moving-pole rotor are not topologically or electromagnetically fixed, and move relative to a fixed reference frame during operation. This means that the rotor is constantly "slipping" and lagging behind the drive frequency provided by the stator, or moving out of synchronization. For this reason, these motors are often referred to as "asynchronous" motors. Examples of moving-pole rotors include wound squirrel-cage induction rotors, armature-wound rotors, brush motors, and other similar motors. Moving-pole rotors have Current phase shifter angle318 can be self-adjusting, but a design compromise must be made between the ferromagnetic material on the D-axis and the field winding on the Q-axis to allow the poles to move uniformly across the rotor surface. As a result, for a given size and power rating of moving-pole rotor, such a motor will have higher electrical resistance, require more starting current, and produce a lower field strength.

[0056]

[0072] The magnetic field of the rotor 306 is configured to be excited by the magnetic field generated by the stator windings 304. The rotor 306 and the stator 302 are configured to move relative to each other in response to the excited rotor magnetic field. The rotor 306 is substantially energetically isolated from components of the stator 302 other than the stator windings 304.

[0057]

[0073] In an electric machine, the stator and rotor may be coupled to enable power transfer, signal transmission, and / or electromagnetic field modulation during operation. Coupling may be classified as direct or indirect coupling. Direct coupling occurs between the stator and rotor along a primary working air gap, such as air gap 314. Indirect coupling occurs along a secondary interface away from the primary working air gap.

[0058]

[0074] Direct coupling is generally characterized as inductive coupling; for example, a squirrel-cage induction rotor is considered to be directly coupled to the stator. While direct coupling is common and easily controlled in asynchronous machines, direct coupling in synchronous machines is difficult to control for reasons explained throughout this disclosure. For example, rotor position often needs to be known to ensure that proper current magnitude and / or frequency are maintained.

[0059]

[0075] Indirect coupling operates along secondary couplings, which may be radially or axially oriented, and may communicate via electrical contacts, inductive coupling along separate air gaps, capacitive coupling, or optical coupling. Secondary couplings may be used for a variety of functions to improve the efficiency and / or overall controllability of electric machines, but often require additional components that can increase the weight, complexity, frequency of failure, and cost (both operational and capital) of machines utilizing such systems.

[0060]

[0076] Coupling may be further classified as power coupling or signal coupling. Power coupling transfers electrical power from the stator to the rotor, which is used to directly drive a magnetomotive force along the primary working air gap, thereby generating torque. Signal coupling transfers signals between the stator and rotor that can be used to individually regulate electrical circuits in the rotor or monitor rotor conditions, such as temperature or position relative to a fixed reference frame. Signal coupling transmits at very low power levels relative to the motor's rated power, e.g., less than 5% of the motor's rated power. In some implementations or under some operating parameters, it may be desirable for signal coupling to transmit power at levels relative to the motor's rated power, e.g., 7.5%, 5%, 3%, or 2.5%.

[0061]

[0077] Energetically isolated motors and generators such as those described throughout this disclosure primarily use direct coupling (within the limits of standard electromagnetic shielding) to transfer power and signals between the stator and rotor, without indirect or secondary coupling. The electric machines described herein include direct coupling for both power and signal coupling between the rotor 306 and the stator 302.

[0062]

[0078] In some implementations, the wound rotor may be rotated when at or from position D as shown in FIG. 3B. Current phase shifter angleThe rotor needs to be charged, or can benefit from being charged, when it moves to position Q through modulation of the rotor winding. Charging may mean generating a current in one or more rotor windings, or transferring, increasing, or storing magnetic flux in the rotor, each of which may involve some power transfer from the stator to the rotor. Such a task may be, for example, the transfer of stator excitation. Current phase shifter angle forward modulation of the stator excitation (e.g. Current phase shifter angle (advancing or retarding the stator excitation accordingly) Current phase shifter angle This may be accomplished in various ways by increasing the frequency of change in , increasing the magnitude of the excitation current (or any of the resulting signal components) in the stator, or any combination thereof. In some examples, the rotor magnetic field may need to be weakened (e.g., by reducing the level of current or magnetic flux present in the rotor and / or rotor field windings), for example, by operating at or near position D' (e.g., by transitioning from position Q to position D', or from position D' to Q'). Such a task may be accomplished by: Current phase shifter angle modulating the stator excitation (e.g. Current phase shifter angle (advancing or retarding the stator excitation accordingly) Current phase shifter angle This can be achieved in various ways, such as by lowering the frequency of change of the field, by reducing the magnitude of the excitation current (or any of the resulting signal components) in the stator, or any combination thereof. Alternatively or additionally, field weakening can be achieved through passive losses in the rotor field winding current due to ohmic losses. During operation, in some implementations, frequency and harmonic independence can be observed between the signal emitted by the stator and the fundamental operating frequency that determines the rotor speed. As discussed below, this disclosure recognizes that control of the electric motor can be achieved in a manner that prioritizes additional goals beyond simply moving the rotor, such as increasing system efficiency, controlling losses in the system, or mitigating the possibility of operating conditions that may impair or reduce the effectiveness of the system. Further details regarding such systems are provided throughout this disclosure, for example, in FIG. 6 and related discussion.

[0063]

[0079] 3C and 3D are perspective and side views of an exemplary electric machine 350. Electric machine 350 is substantially similar to electric machine 300, except for the differences described herein. Rotor 356 includes six rotor poles 358. Stator 352 includes distributed windings 354. Electric machine 350 has six rotor teeth (pole 358) and 36 stator teeth 370, resulting in a rotor tooth to stator tooth ratio of 1:6. This differs from electric machine 300, which has four rotor teeth (pole 308) and 12 stator teeth 320, resulting in a rotor tooth to stator tooth ratio of 1:3. Other rotor tooth to stator tooth ratios, such as a 1:2 or 1:4 ratio, may be used without departing from this disclosure. Other ratios of rotor teeth to stator teeth can be used without departing from this disclosure, whether salient concentrated or distributed stator windings are used.

[0064]

[0080] FIG. 4 is a side view of an exemplary electric machine 400. The electric machine 400 is substantially similar to the electric machine 300 described above, except for the differences described herein. The rotor 406 is the outer rotor, and the stator 402 is the inner stator. In other words, the rotor 406 surrounds the stator 402 and rotates around the stationary stator 402. The stator 402 defines stator poles 411 with salient, non-lapped, concentrated winding stator coils 404. The rotor 406 includes permanent magnetic material 416 embedded within the rotor 406. As shown, each rotor pole 408 includes four channels of permanent magnetic material 416 arranged in a generally "M" or "W" shaped configuration, although other arrangements may be used without departing from this disclosure. The permanent magnetic material 416 may include various materials, including ferrite, SmFeN, N35, and N45. Typically, a low magnetic strength permanent magnetic material is used, although less powerful magnetic material can be used without departing from this disclosure. The permanent magnetic material 416 can extend the entire longitudinal length of each rotor pole 408 or can extend partially across each rotor pole 408. In some implementations, the permanent magnetic material 416 can be configured in multiple layers or laminations.

[0065]

[0081] As shown, the permanent magnetic material 416 provides a net magnetic force that is substantially aligned with each rotor pole 408. In some implementations, the permanent magnetic material may be positioned such that the net magnetic force from the permanent magnetic material 416 is not aligned with the rotor pole 408. Generally, the placement of the permanent magnetic material depends on the desired cross-sectional magnetic flux density of the magnetic material within the rotor. In implementations in which the permanent magnetic material 416 is positioned within the rotor coils 310, the magnetic flux in each set of permanent magnetic material 416 can be individually adjusted and / or modulated by adjusting the charge of the surrounding rotor coils 310. Such implementations also protect the magnets from demagnetization that may be caused by a strong stator magnetic field. In implementations in which the permanent magnetic material 416 is not surrounded by the rotor coils, adjustments to the magnetic flux caused by the stator magnetic field may affect multiple sets of permanent magnetic material 416 within the rotor 406.

[0066]

[0082] 5A-5C show front, side, and perspective views of an exemplary rotor coil 310. As shown in FIGS. 3A, 3B, and 4, each rotor coil 310 functions as its own winding, with a single coil around each pole, such as rotor pole 308 or 408. As such, the rotor may be described as including concentrated, salient, and / or non-lap windings. In some implementations, the winding direction of each coil may alternate between adjacent rotor poles 308 or 408. For example, implementations using stators with salient, concentrated, and / or non-lap windings may use such an arrangement. Alternatively, the commutation direction of the commutator 311 may alternate between adjacent poles to achieve similar results. In some implementations, the winding direction need not alternate between adjacent rotor poles. For example, implementations using stators with distributed windings may use such an arrangement. Although the rotor coil 310 is shown as a single coil shorted to itself, other geometries can be used as long as each coil is shorted to itself and does not overlap adjacent coils. In some implementations, magnetic poles of like polarity can be shorted to share a commutator, for example. Similarly, magnetic poles of different polarity can be shorted to each other, depending on the winding direction of each pole. In general, rotor coils are often configured so that the current skin depth at power transfer frequencies completely penetrates the coil's conductor. In the context of this disclosure, "current skin depth" refers to the depth from the conductor surface through which current, particularly eddy currents induced by a changing magnetic field at a given frequency, primarily flows. For a given material, the skin depth can be calculated as follows: δ≒1 / √πfμσ (2) "f" is the magnetic switching frequency, μ is the magnetic permeability of the material (in H / mm), and σ is the electrical conductivity of the material. Achieving full skin-depth penetration within the rotor coil 310 allows for uniform inductance within the rotor coil 310. In some implementations, the drive frequency may range from 0 Hz to 20 Hz. In some implementations, the drive frequency may range from 100 Hz to 2000 Hz. Generally, the rotor coil is configured such that decay of magnetic flux within the rotor is resisted by current flow in the rotor coil in response to magnetic field shifts from the stator.

[0067]

[0083] Traditionally, synchronous motors do not have a magnetizing current to magnetize the material, so the magnets must be magnetized at the factory or before installation. Therefore, if the magnetic material demagnetizes during operation (e.g., because the stator is overloaded), the magnets may be damaged or the motor may not operate at all. The rotor coil 310 helps protect the permanent magnets from the effects of potential demagnetization of the stator.

[0068]

[0084] The commutator 311 in each of the rotor coils 310 helps reduce torque ripple in the electric motor during operation. The commutator does this by reducing the delay of magnetic flux excitation in the air gap 314. While the rotor coils 310 resist the decay of magnetic flux in the rotor due to current in the rotor winding in response to magnetic field shifts, the rotor coils 310 perform this function without commutation, regardless of the portion of the drive cycle to which the rotor coils 310 are exposed. That is, an uncommutated rotor coil is symmetrical with respect to both the positive and negative portions of the drive frequency. This configuration can result in a measurable amount of torque ripple. In rotor coils 310 with commutators 311, the rotor coils 310 can resist a first change in magnetic flux by inducing a first current in the rotor winding in a first direction until the first current decreases to zero, and allow a second change in magnetic flux to induce a current in the rotor winding in a second direction. That is, the current in the rotor windings is unidirectional, resulting in an asymmetric response and reducing torque ripple during operation.

[0069]

[0085] In operation, the current flowing through the coils (310, 410) and commutator can be reduced to zero. Current phase shifter angle This is done by reducing the angle 318 to less than 90° (i.e., "pull" instead of "push" adjacent poles). Current phase shifter angle The decay can occur within a time period where the angle is less than 90°. Such a time period can range from a few milliseconds to 2 seconds, depending on the speed and saturation of the rotors (306, 406). Then, as the current in the coils (310, 410) increases, Current phase shifter angle Throughout this process, the magnitude of the current is increased. Current phase shifter angle When adjusting the 318, try to cancel out the ripple current. Current phase shifter angle 318.

[0070]

[0086] FIG. 5D is a graph 550 showing various charge states 552 and generated torque 554 under a locked rotor condition (e.g., starting), as well as different phaser angles 556. Current phase shifter angle In (left), the rotor current 558 is shown to respond strongly to instantaneous stator current excitation. When operating between the Q axis (90°) and the D axis (0°), a high level of charge 552 is seen with substantial inductive decay (e.g., maintaining the magnetic field).

[0071]

[0087] Torque 554 is relatively large due to the low concentration of the stator Q-axis current. Current phase shifter angle 556. A damping can be observed due to the current 558 passing through the rotor coils (310, 410) to resist the change in magnetic flux. Under such a control scheme (in combination with coils 310 or 410), the rotor magnetic field Current phase shifter angle556, which may provide a wider operating range during operation. As can be seen from graph 550, the D-axis 312 to Q-axis operation demonstrates a shielding effect that protects the magnet material, allowing for reduced magnet material, lower coercivity materials, or both. As the stator Q-axis current increases, the rotor current is shown to contribute more to torque generation (130 degrees to 120 degrees). At 90 degrees, the current is orthogonal to the rotor D-axis and no net current is generated.

[0072]

[0088] Another advantage is that the field weakening due to D-axis injection is not constant, as compared to the case of permanent magnets. Similarly, the rotor field can be modulated by the magnitude of the current passing through the stator. In many cases, it is necessary to vary the current magnitude and Current phase shifter angle 556 can be adjusted simultaneously. Phaser The rotor current at angles θ is shown to be counter-circular with respect to the excitation current due to the presence of the commutation circuit. The rotor field increases during these periods due to the decay of the reactive field between the net D-axis injection and the stator excitation.

[0073]

[0089] The control section determines the desired rotor field modulation. Current phase shifter angle This current magnitude or amplitude modulation can be used to further limit torque ripple by modulating the rotor flux. The rotor flux can be transferred from the stator to the rotor through modulation on the D axis of the machine in a synchronous reference frame. This current magnitude or amplitude modulation is Current phase shifter angle Higher frequency modulation can further reduce torque ripple, especially in systems where higher frequency harmonics are attenuated and / or filtered by the system, which may include the inertial mass of the powertrain or vehicle load or even the rotor itself.

[0074]

[0090] In some instances, torque ripple may also modulate the magnitude or amplitude of the current in the D-axis of the machine in the synchronous reference frame, resulting in a desirable torque distribution suitable for maximum torque production. Current phase shifter angleIn such an example, the controller modulates the magnitude or amplitude of the current in the Q-axis in the synchronous reference frame proportionally with respect to the modulation in the D-axis. In some examples, such proportional modulation of the Q-axis magnitude is 5-10%, 10-20%, 20-40%, or 50-100% of the D-axis modulation. In some examples, this is achieved by adjusting the D-axis modulation to a value that is set or desired for maximum torque generation. Current phase shifter angle In some cases, such tolerances may allow for a set vibration tolerance. Current phase shifter angle The variance from 0-1%, 0-5%, 5-10%, 10-30%, or 30-60% is possible. The smaller the tolerance for vibration, the tighter the controller can control torque ripple, assuming the controller gives sufficient priority to maintaining the rotor field at the appropriate level of flux. These tolerances can also be described as the duty cycle of the stator excitation.

[0075]

[0091] To further illustrate such a control scheme, FIG. 6 shows a schematic diagram of an electric motor 600 along with the alignment between the rotor 602 and stator 604. Position D is defined as the alignment of opposing stator 604 and rotor 602 poles (i.e., NS and SN). Positions Q and Q' are defined as being electrically orthogonal to D and D' due to misaligned poles (i.e., approaching like poles and approaching opposite poles, respectively) or alignment of like stator 604 and rotor 602 poles (i.e., NN and SS). In some implementations, particularly with highly salient rotors, peak torque (e.g., due to its reluctance component) occurs between positions D and Q in the synchronous reference frame. In other implementations, such as cylindrical rotors (e.g., machines with low saliency), peak torque occurs between positions Q and D'. In instances where permanent magnet motors are used, peak torque operation may require demagnetization at high loads and weakening of the field at high speeds, which may compromise size / weight and / or torque production if weaker magnets are used.

[0076]

[0092] In some embodiments, permanent magnets may be used. To increase the magnetic current capability without the risk of demagnetization, rotor windings as described herein are used. At low torques, the rotor winding current can be reduced, lowering the cogging (resistive) torque and eliminating the need for a stronger permanent magnet active flux weakening. Current phase shifter angle Using modulation of the winding rotor, the winding rotor can be flux weakened or flux strengthened through a control mechanism (e.g., decreasing or increasing the current in the rotor field winding, decreasing or increasing the magnetic flux in the rotor pole body). As a non-limiting example, the synchronous excitation from the stator can be Current phase shifter angle can be modulated. In at least some configurations, no secondary control system or additional commutation hardware is required, such as in a wound rotor synchronous motor that controls the stator field.

[0077]

[0093] As described herein, wound rotor configurations according to the present disclosure do not require additional stator-to-rotor coupling elements. Rather, signals are transmitted using the stator and rotor windings along with the rotor laminations. This reduces costs and components, improves performance (e.g., eliminates brush ohmic losses), eliminates or controls physical contacts and wear components, reduces package size, and provides control flexibility compared to schemes that incorporate special detectors, sensors, wired or wireless connections, or brushes to transmit signals from the stator to the rotor.

[0078]

[0094] As described throughout this specification, in systems where control signals may be converted to DQ axis components, such as that shown in Figure 6, a third z-axis component also exists, which may be described as a signal or magnetic quantity that does not map directly to the D or Q axes, for example, a component orthogonal to the plane that may define the Q and D components as shown.

[0079]

[0095] In operation, field-oriented control, or vector control, involving specific modulations (e.g., modulation of signals or signal parameters) can be used to control various aspects of the rotor magnetic field. These modulations can be used to adjust the signal excitation coupling between the stator and rotor and to control the stator excitation waves (e.g., relative position and magnitude) relative to the rotor. Thus, the rotor response, i.e., the direct correlation of the currents induced in the rotor windings, can be effectively "engineered" by the stator and inverter. In other words, such control can shape the dynamic behavior of the machine in response to the currents in the D-axis and Q-axis magnetic fields, as coordinated by a controller, such as controller 104 or controller 700 (FIG. 7). Among other strategies (e.g., torque generation), vector modulation can be used to: Current phase shifter angle can be used to help define the modulation of

[0080]

[0096] This disclosure recognizes that vector control modulation can be used to directly affect rotor responses through applied stator signals. Furthermore, these rotor responses may be modulated in either the D-axis or the Q-axis. Current phase shifter angle This may be achieved using modulation. Current phase shifter angle The relative effectiveness of the modulation may be proportional to both the magnitude of the modulation and the rate of change (eg, over time). Current phase shifter angle The rate at which the modulation is performed may be varied by the controller and selected for the intended response in the rotor material or rotor response. In some cases, the frequency may be selected based on the speed of the machine, while in other cases, a fixed modulation may be selected. The frequency of the modulation may be selected based on various considerations. For example, in some configurations, the frequency may be at least 2-4 times higher than the fundamental frequency of the machine. In other situations, the modulation may be 5-10 times higher than the fundamental frequency of the machine. In yet further configurations, the frequency may be 10-30 times higher than the fundamental frequency of the machine. For example, in some configurations, the frequency may be selected to prevent interaction with torque generation (e.g., to reduce torque ripple).

[0081]

[0097] Current phase shifter angle can be controlled using vector component control, which can be described by letting id, iq, and iz be the fundamental frequency currents expressed in the DQ reference frame shown in FIG. Current phase shifter angle These signals may be directly modulated, or an independent excitation modulation may be applied to either the D or Q axis that is added to the fundamental current to give the total stator current: idtotal=id +idmodulation (3) iqtotal=iq +iqmodulation (4) iztotal=iz +izmodulation (5) where id, iq, and iz are normal excitation currents along each axis, and i excitation, i q excitation, and ize excitation are independent modulation signals that can be selected and controlled by a motor controller or other controller as described in more detail below. The modulation can be selected to be sinusoidal or can take any form; for example, such modulation can be further described as: idexcitation=md cos(wdt) (6) iqexcitation=mq sin(wqt) (7) izexcitation=mz sin(wzt) (8) The modulation magnitude and frequency are selected independently for each component and vector sum, Current phase shifter angle You can also change Current phase shifter angle It is also possible to directly control (γ) to vary the principal components as follows: idtotal=id*cos(γ) (9) iqtotal=iq*sin(γ) (10) iztotal=iz*sin(γ) (11) Similarly, the set Current phase shifter angle The following modulation can also be performed on idtotal=id*cos(γ+γmodulation) (12) iqtotal=iq*sin(γ+γmodulation) (13) iztotal=iz*sin(γ+γmodulation) (14) Here, γ modulation is, for example, a fixed Current phase shifter angle can be described as a sinusoidal oscillation centered on γdmodulation=md cos(wdt) (15) γqmodulation=mq sin(wqt) (16) γzmodulation=mz sin(wzt) (17)

[0082]

[0098] In each case, modulation may be applied to a single axis, leaving the other two axes unmodulated, and used to generate rotor response. Alternatively or additionally, D-axis current modulation can be used, and varied in parallel with Q-axis current modulation, with the goal of controlling or minimizing torque ripple. If D-axis modulation is insufficient, Q-axis modulation can be used. In some implementations, Q-axis modulation is used in combination with D-axis modulation to create rotating vector injection. Z-axis modulation does not inherently affect torque ripple and does not require knowledge of the DQ reference frame. However, Z-axis modulation often has limited effect on the rotor, but can be used to couple the stator to the rotor for either power or side-information coupling (e.g., speed and / or position).

[0083]

[0099] Current modulation, i.e., Phaser vibrationThe frequency of the pulses can be described by a duty cycle. This duty cycle can be divided into two main components: flux injection (e.g., D-axis) and torque generation (e.g., Q-axis). In starting conditions, before split operation between D-axis and Q-axis for torque generation, the duty cycle on D-axis for strong rotor flux injection can be 100%, or 75-100%, or 40-100%, and in split operation, it can be 50%-50% split, 30%-70%, 20-80%, 10-90% split (D-axis:Q-axis). This also means that during steady-state or quasi-steady-state operation, Current phase shifter angle And the resulting magnetic field varies by 5, 10, 20, or even 30-45 degrees around a certain angle. Current phase shifter angle In some implementations, the frequency of the oscillation or amplitude modulation can be varied to both elicit rotor response and / or limit torque ripple during operation.

[0084]

[0100] Additionally, the control strategy may utilize higher frequency operation, i.e., pulsing, to limit the amount of flux decaying over time in the rotor coils. That is, by shortening the time step of the rotor MMF cycle (which decays over time), it is possible to reduce the dispersion of the flux across the rotor coils, making the flux stiffer and reducing negative torque moments or the associated torque ripple. This helps inject flux into the rotor, limits torque ripple, and reduces the torque during operation. Current phase shifter angle Additional signal modulation, such as skewed signals, trapezoidal, or pulse width modulation (PWM) techniques, may be used to smooth the transition between them.

[0085]

[0101] Because stator-side currents may correspond to stator-side voltages, schemes involving signals embedded in currents may correspond to equivalent schemes involving signals embedded in voltages. Implementations described throughout this disclosure with respect to stator-side voltage signals may be equivalent to stator-side current signals, and vice versa, and may be similarly described.

[0086]

[0102] As mentioned above, the control of the rotor magnetic field is Current phase shifter angle This modulation may be defined by magnitude and frequency and may be observed by the machine magnetic field, the stator excitation, and the primary control components. Current phase shifter angle The modulation may be used to deliver power to an AC coil, Current phase shifter angle The vibration of is defined by the DQ reference frame Current phase shifter angle is defined with respect to a set operating point (e.g., Current phase shifter angle may be modulated to achieve a target torque per ampere, or MTPA). Current phase shifter angle The modulation perturbation may be defined by the oscillation, magnitude, and frequency of the excitation magnetic field. Current phase shifter angle Modulation of the magnitude of the current in can be used to transfer power to the rotor or induce a response in the rotor, with the largest response being most coupled to the rotor (in the DQ reference frame of a given pole). Current phase shifter angle For example, for a wound rotor aligned with the D axis relative to the axes of the synchronous reference frame, Current phase shifter angle is electrically 0° (where electrical 0° is defined as the D axis of the synchronous reference frame).

[0087]

[0103] In some implementations, alternating commutation direction effectively means reversing the polarity of each rotor pole from its neighbor. In other words, a four-pole machine has NSNS. Alternatively, to achieve such alternating pole arrangements, the winding direction can be reversed from pole to pole to establish the appropriate polarity (e.g., when using a single coil and commutator). Alternatively, unidirectional windings may be used, and the commutator itself can be reversed from pole to pole to provide the appropriate polarity for the rotor.

[0088]

[0104] In some implementations, individual or parallel rotor coil windings are used to establish local magnetic flux conditions within the machine. In some implementations, grouped or series coil rotor coil winding(s) are used to balance rotor currents with magnetic flux throughout the machine. This can be done depending on the periodicity or symmetry of the machine. A combination of parallel and series individual and group windings can be used to achieve local control areas and distributed balance across the rotor or the entire machine.

[0089]

[0105] FIG. 7 is a block diagram of an example controller 700 that may be used in embodiments of the present disclosure. The controller 700 may be used in addition to or instead of the electric motor controller 104 described above. In the former example, the controller 700 and the electric motor controller 104 may be combined into a single integrated controller, or the controller 700 and the electric motor controller 104 may be separate, individual controllers. The controller 700 may, among other things, monitor parameters of the electric machines (300, 400) and send signals to actuate and / or adjust various operating parameters of the electric machines (300, 400). As shown in FIG. 7 , the controller 700, in certain examples, includes a processor 750 (e.g., implemented as a single processor or multiple processors) and a memory 752 (e.g., implemented as a single memory or multiple memories) that includes instructions that cause the processor 750 to perform the operations described herein. The processor 750 is coupled to an input / output (I / O) interface 754 for sending and receiving communications with components within the electric machines (300, 400), including, for example, rotor position sensors or current sensors. In certain examples, the controller 700 may additionally communicate status and send actuation and / or control signals (including power or drive signals to the stator) to one or more of the various electromechanical components of the electric machines (300, 400) (such as power or drive signals to the stator) and other sensors (e.g., temperature sensors, vibration sensors, and other types of sensors) provided on the electric machines (300, 400). Communications may be wired, wireless, or a combination of wired and wireless. In some implementations, the controller 700 may be a distributed controller with various parts located in different locations, for example, in different parts of a vehicle. Additional controllers may be used in combination with the controller 700, either as standalone controllers or networked controllers, without departing from this disclosure.

[0090]

[0106] The controller 700 may have various levels of autonomy for controlling the electric machine (300, 400). For example, the controller 700 may begin to sense changes in load and / or speed, and an operator may be able to adjust the power frequency, current magnitude, and / or Current phase shifter angle Alternatively, the controller 700 may begin to sense changes in load and / or speed, receive additional input from the operator, and adjust the frequency, current magnitude, and / or Current phase shifter angle Alternatively, the controller 700 may begin to sense changes in load and / or speed and adjust the frequency, current magnitude, and / or Current phase shifter angle can be adjusted.

[0091]

[0107] For example, in operation, the controller may be a controller configured to send control signals to the stator windings to excite the stator windings and generate a stator magnetic field within the stator. Current phase shifter angle and magnitude of the current, depending on the operating conditions of the electric machine (300, 400). Current phase shifter angle The controller may be configured to generate a stator magnetic field by actively adjusting the magnitude and magnitude of the stator magnetic field. Alternatively or additionally, the controller may receive a position stream from the position sensor 316. The position stream represents the rotor position. The position stream may be an analog or digital electrical or electromagnetic signal. In response to receiving the position stream, the controller may determine the presence, absence, or degree of torque ripple present. Then, in response to determining that torque ripple is present, the controller: Current phase shifter angle and / or the magnitude of the current may be adjusted.

[0092]

[0108] In some implementations, Current phase shifter angle 318 grows ahead of the rotor poles (308, 408) in the direction of travel during high torque conditions, i.e., when more current per unit torque is required, Current phase shifter angle 318. In general, Current phase shifter angleAs 318 increases, the rotor coils (310, 410) are more energized (more current flows through them) due to the smaller D-axis component 312. Current phase shifter angle The larger 318, the faster the magnetic field in each rotor winding decays. More activity in the coils can lead to increased unmitigated torque ripple, but the current amplitude increases while the D-axis component experienced by each pole increases. Current phase shifter angle This can counteract the potential negative torque caused by the increase in 318. Current phase shifter angle 318 is made smaller during high speed and low torque operation. Current phase shifter angle can be negative during braking operations. Regardless of the operating mode used, the controller 700 adjusts the Current phase shifter angle and / or the current amplitude can be adjusted.

[0093]

[0109] In particular, the main components of the machine Current phase shifter angle Alternatively, the current amplitude can be adjusted during operation to generate torque. In some instances, for example, if the rotor has sufficient magnetic field strength, no (or less) magnetizing current may be applied compared to a previous time step. In other instances, such as high-speed operation, it may be possible to lower the rotor magnetic field to reduce back electromotive force (EMF) and provide voltage headroom, reducing cogging torque and limiting torque ripple, and avoiding active field-weakening. The controller can communicate with the rotor through the stator at a wide range of frequencies, for example, from 50 to 1000 hertz (Hz). In some implementations, communication occurs at 100 to 1000 Hz. In either case, the system can transmit changes faster than conventional systems. For example, conventional squirrel-cage induction machines communicate at substantially 7 Hz. The high-frequency transmission capability allows the controller 700 to actively reduce torque ripple regardless of operating conditions and quickly respond to changing operating conditions.

[0094]

[0110] FIG. 8 is a flowchart of a method 800 that may be used in embodiments of the present disclosure. All or a portion of method 800 may be performed by controller 800 and / or motor controller 104. At 802, a stator winding of the stator is energized to generate a stator magnetic field within the stator. At 804, the stator magnetic field modifies a corresponding rotor magnetic field within the ferromagnetic material within the rotor. At 806, the shift in the stator magnetic field generates a tangential force on the rotor. At 808, the generated tangential force moves the rotor. The stator magnetic field and rotor are maintained synchronized with each other during operation. At 810, a commutator inhibits the delay of excitation of the magnetic flux in the air gap. The air gap is defined by the inner surface of the stator and the outer surface of the rotor.

[0095]

[0111] At 812, the decay of magnetic flux in the rotor is resisted by current in the rotor coils in response to the magnetic field shift. The resistance in the decay of magnetic flux is not symmetrical due to the inclusion of a commutator 311 in each rotor coil 310. Thus, a first change in magnetic flux is resisted by inducing a first current in a first direction in the rotor winding until the first current decreases to zero, and a second change in magnetic flux is allowed to induce a current in a second direction in the rotor winding.

[0096]

[0112] In some examples, at 814, a current is passed through the stator. Current phase shifter angle Usually, Current phase shifter angle leads the rotor pole in the direction of travel. In some examples, at 816, the magnitude of the current is adjusted in response to changing operating conditions. At 818, the magnitude of the current relative to the rotor pole (D-axis) is adjusted. Current phase shifter angle is adjusted in response to changing operating conditions. In particular, steps 814 and 816 are shown dotted because both steps are not required, nor are they required to be in that order. Current phase shifter angle may be adjusted independently of each other.

[0097]

[0113] The current electric machine operating power is then compared to the desired electric machine operating power. If the current electric machine operating power is at the desired electric machine operating power, the machine continues to operate using the most recently adjusted parameters of the stator current. Otherwise, the process continues by adjusting the magnitude or Current phase shifter angle Repeat by returning to adjusting at least one of the

[0098]

[0114] Referring now to FIG. 9A , a non-limiting example of process control according to the present disclosure is provided. In particular, FIG. 9A provides an exemplary flowchart for controlling an electric motor system to achieve increased torque 900 according to the present disclosure. Process 900 begins at 902 with a request for increased torque. According to the present disclosure, fulfilling this request can be conceptualized as performing two parallel workflows. However, in practice, the controller need not be programmed or designed to operate in independent, parallel, or other different flows. To fulfill the torque increase request 902, the controller determines that achieving the increased torque can be done by increasing rotor flux at 904. To do this, it increases Id at 906, which increases rotor flux at 908. This continues until the desired rotor torque is achieved, after which it decreases Id at 910. However, while attempting to increase rotor flux, the controller recognizes that Q-axis current modulation can also be used, and can be varied in parallel with D-axis current modulation, with the goal of controlling or minimizing torque ripple. Thus, the controller also acts to maintain torque performance at 912. To this end, the controller also modulates Iq at 914, thereby obtaining the desired torque increase at 916, but without the adverse effects of unstable torque performance, such as may be caused by torque ripple.

[0099]

[0115] 9B, another non-limiting example of a control process 918 for responding to a request for increased torque at 920 is provided. In response to the request at 920, the controller determines that achieving increased torque can be accomplished by requesting an increase in rotor flux at 922. To accomplish this, the controller determines that the rotor flux is increased towards the D axis at 924. Current phase shifter angle This easily increases the rotor flux at 924, and the rotor field moves towards the Q axis at 928. Current phase shifter angle In parallel, the controller works to maintain torque performance at 930 by modulating Iq as described above, thus resulting in the requested torque increase at 934.

[0100]

[0116] 9C, another non-limiting example of a control process for arriving at a desired torque profile at start-up is provided at 936. At start-up, the rotor is locked at 938. To begin rotation, at 940: Current phase shifter angle is modulated toward the D axis, and at 942 the rotor flux is established or increased as the rotor moves toward the D axis. Current phase shifter angle is modulated towards the Q axis and this process continues at 946 until the desired torque is produced.

[0101]

[0117] 9D provides yet another non-limiting example of a control process for reaching a desired torque at 948. In this case, the process begins with the motor already running at high speed 950. At 952: Current phase shifter angle The modulation duty cycle is reduced, reducing the amplitude of the current modulation at 954. As a result, the rotor flux decreases at 956. The back EMF decreases at 958, and the cogging torque decreases as the rotor flux decreases at 960. This control ultimately results in an increase in torque at 962, given the higher speed of the motor at 950.

[0102]

[0118] Thus, the described system and method has been found to lead to a net increase in torque through sinusoidal excitation due to asymmetric flux vector control of the rotor field lines along the stator D-axis, resulting in a net rotor field D-axis current injection. As a result, net D-axis current injection is possible in conventional circuits with analog circuitry. Machines with rotor coil configurations experience less saturation and provide a net advantage over shorted coils in terms of average torque generation. Net D-axis current injection allows for greater sheet current density under equivalent stator excitation due to rotor coil reactive current.

[0103]

[0119] Thus, particular implementations of the inventive subject matter have been described. Other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results.

Claims

1. 1. A method of controlling an electric machine, comprising: exciting a stator winding of a stator of the electric machine with a stator current; generating a stator magnetic field within the stator with the energized stator windings; generating a corresponding rotor magnetic field in a ferromagnetic material within a rotor of the electric machine by the stator magnetic field, the rotor defining a plurality of rotor poles and including a rotor winding associated with each of the plurality of rotor poles; generating a tangential force on the rotor due to the shift of the stator magnetic field; moving the rotor with the generated force tangential to the rotor, the stator field and the rotor being maintained in synchronization with one another during operation of the electric machine; suppressing attenuation of magnetic flux excitation in the air gap between the stator and the rotor by a commutator included in the rotor winding; resisting decay of magnetic flux in the rotor with current in the rotor winding in response to the shift of the stator magnetic field; achieving a target operational output of the electric machine; Including, the resistance to the decay of the magnetic flux is asymmetric due to the inclusion of the commutator; a first change in the magnetic flux is resisted by inducing a first current in a first direction in the rotor winding until the first current decreases to zero, and a second change in the magnetic flux is allowed to induce a second current in a second direction in the rotor winding; reducing the current flowing through the rotor winding and the commutator to zero during operation by reducing the current phaser angle to less than 90°; increasing a current phaser angle as the current in the rotor winding increases; A method wherein a current phaser angle is a relative angle of the rotor poles with respect to the magnetic center of the stator.

2. the electric machine comprising a commutation system including a commutator disposed across each of the plurality of rotor poles; The method of claim 1 , wherein the commutation system is configured to control for alternating currents induced in the plurality of rotor poles when the corresponding rotor magnetic fields are excited by the stator magnetic field.

3. suppressing the attenuation of magnetic flux excitation in the air gap between the stator and the rotor by the commutator; 3. The method of claim 1 or 2, comprising inhibiting the decay of magnetic flux excitation in the air gap by the commutator to reduce torque ripple during operation of the electric machine.

4. 4. The method of claim 1, further comprising selecting adjustments to at least one of a current phaser angle or a current magnitude to control rotor torque ripple while achieving the target operating output of the electric machine.

5. Sending the stator current through the stator at a current phaser angle; The method of any one of claims 1 to 4, wherein the current phaser angle leads the rotor pole in the direction of motion or is measured relative to the nearest one of the rotor poles.

6. 6. The method of claim 1, further comprising adjusting a current phaser angle of the stator current relative to a magnetic pole in response to changes in one or more operating conditions based on the target operational output of the electric machine.

7. adjusting the current phaser angle includes adjusting the current phaser angle on only one axis of the electric machine; The method of claim 6 , wherein the one axis comprises one of a D-axis or a Q-axis of the electric machine.

8. determining a target rotor motion corresponding to the target operational output of the electric machine; modulating current in the D-axis to control rotor torque ripple while the rotor is performing the target rotor motion; achieving the target operational output of the electric machine; and The method of claim 7 further comprising:

9. 9. The method of claim 1, further comprising adjusting a current magnitude of the stator current based on the target operational output of the electric machine and in response to changes in one or more operating conditions, independently of a current phaser angle of the stator current.

10. The method of any preceding claim, further comprising determining a target rotor motion corresponding to the target operational output of the electric machine.

11. calculating a vector control modulation to be applied to the stator that produces the target rotor motion; adjusting a current phaser angle of the stator current based on the vector control modulation to cause the rotor to achieve the desired rotor motion and achieve the desired operating output of the electric machine; The method of claim 10 further comprising:

12. The method of claim 11 , further comprising modulating at least one of the magnitude or frequency of the stator current based on the vector control modulation.

13. adjusting at least one of the frequency or amplitude of the stator current to cause the rotor to achieve the desired rotor motion; Achieving the target operational output of the electric machine, or controlling rotor torque ripple when the rotor is performing the target rotor motion to achieve the target operational output of the electric machine. The method of claim 12 further comprising:

14. increasing a current phaser angle of the stator current to lead the rotor poles along the stator windings to deliver increased torque and thereby achieve the target operating output of the electric machine; Increasing the current phaser angle of the stator current and simultaneously increasing the magnitude of the stator current to control rotor torque ripple. The method of any one of claims 1 to 13, further comprising:

15. 15. The method of claim 1, further comprising increasing the stator current phaser angle to deliver reduced torque at increased rotor speed to achieve the target operating output of the electric machine.

16. 16. The method of claim 1, further comprising making the stator current phaser angle negative to provide a braking function for the rotor, thereby achieving the target operating output of the electric machine.

17. 17. The method of any one of claims 1 to 16, further comprising, in response to determining that a present operational output of the electric machine differs from the target operational output of the electric machine, iteratively adjusting at least one of a current magnitude of the stator current or a current phaser angle of the stator current until the operational output of the electric machine is the same as the target operational output of the electric machine.

18. and, in response to determining that a current operational output of the electric machine is the same as the target operational output of the electric machine, operating the electric machine using one or more most recently adjusted parameters of the stator current.

18. The method of any one of claims 1 to 17, wherein the one or more most recently adjusted parameters of the stator current include at least one of an adjusted current phaser angle or an adjusted current amplitude.

19. 1. An electric machine comprising: a stator defining a plurality of stator poles with associated stator windings configured to receive a stator current; a rotor defining a plurality of rotor poles fixed by associated rotor windings, the rotor being excited by a magnetic field generated by the stator windings in response to the stator current being received by the stator windings to define a magnetic field that produces relative motion between the rotor and the stator, the rotor being maintained in synchronization with the magnetic field generated by the stator during operation of the electric machine; exciting the stator windings of the stator with the stator current; generating a stator magnetic field within the stator with the energized stator windings; generating a corresponding rotor magnetic field in a ferromagnetic material within the rotor using the stator magnetic field; generating a tangential force on the rotor due to the shift of the stator magnetic field; moving the rotor with the generated force tangential to the rotor; suppressing attenuation of magnetic flux excitation in the air gap between the stator and the rotor by a commutator included in the rotor winding; resisting decay of magnetic flux in the rotor with current in the rotor winding in response to the shift of the stator magnetic field; achieving a target operational output of said electric machine; a controller configured to Equipped with the resistance to the decay of the magnetic flux is asymmetric due to the inclusion of the commutator; a first change in the magnetic flux is resisted by inducing a first current in a first direction in the rotor winding until the first current decreases to zero, and a second change in the magnetic flux is allowed to induce a second current in a second direction in the rotor winding; reducing the current flowing through the rotor winding and the commutator to zero during operation by reducing the current phaser angle to less than 90°; increasing a current phaser angle as the current in the rotor winding increases; A current phaser angle is the relative angle of the rotor poles with respect to the magnetic center of the stator.

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