Power distribution within electric machine with rectified rotor windings

Abstract

An electric machine includes a stator defining a plurality of stator poles with associated stator windings configured to receive a stator current. The electric machine also includes a rotor defining a plurality of fixed rotor poles with associated rotor windings, where the rotor defines a field excitable by a magnetic field generated by the stator windings when receiving a stator current to generate a relative motion between the rotor and the stator, and wherein the rotor remains synchronized with the magnetic field generated by the stator during operation of the motor. The electric machine also includes a rectification system configured to control an alternating current induced in the rotor poles when the stator winding receives a stator current and when a magnetic field generated by the stator winding excites the magnetic field.

Description

[0001] This application is a divisional application of the Chinese invention patent application (application number: 202180063075.2, invention name: Power distribution in an electric motor with rectifier rotor winding, application date: August 2, 2021).

[0002] This application claims priority under 35 USC §119(e) to U.S. patent application serial number 63 / 059,930, filed on July 31, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to electric motors and generators. Background Art

[0004] An electric motor generally includes a stationary component, usually called a stator, and a rotating component, usually called a rotor. Electric current is converted into an electromagnetic field, which exerts a mechanical force or torque between the stator and the rotor, which can be used to do work. Generators work on a similar principle, where mechanical force is converted into electric current. Although mainly described with respect to rotational force or torque, the principles described herein also apply to linear motors. For linear motors, in some embodiments, the rotor acts as the stationary component, while the stator acts as the translating component. Summary of the invention

[0005] This disclosure describes techniques related to wirelessly transmitting power within electric machines.

[0006] An example embodiment of the subject matter described in the present disclosure is an electric machine having the following features. The stator defines a plurality of stator poles with associated stator windings. The rotor defines a plurality of fixed rotor poles with associated rotor windings, the rotor windings including a rectifier and configured to be excited only by the stator. The rotor defines a rotor field that can be excited by a magnetic field generated by the stator windings to produce relative motion between the rotor and the stator. The controller is configured to send current through the stator windings at a current angle measured relative to the nearest one of the rotor poles. The controller is configured to adjust the current angle in response to operating conditions. The controller is configured to adjust the current amplitude of the sent current in response to operating conditions. The rotor remains synchronized with the magnetic field generated by the stator windings during operation.

[0007] In some embodiments, the stator windings include concentrated windings.

[0008] In some embodiments, the stator windings include distributed windings.

[0009] In some embodiments, the stator windings include convex windings.

[0010] In some embodiments, the rotor windings include concentrated windings.

[0011] In some embodiments, the rotor windings include convex windings.

[0012] In some embodiments, the rotor windings include non-overlapping windings.

[0013] In some embodiments, the rectifier includes a diode.

[0014] In some embodiments, the commutation direction alternates between the rotor poles.

[0015] In some embodiments, the rotor includes permanent magnets.

[0016] In some embodiments, the permanent magnets are substantially aligned with the rotor poles.

[0017] An example implementation of the subject matter described in the present disclosure is a method of controlling an electric machine. The method includes the following features. The stator windings of the stator are excited to generate a stator magnetic field within the stator. The corresponding rotor magnetic field within the ferromagnetic material within the rotor poles is modified by the stator magnetic field by establishing magnetic flux. A force tangential to the rotor is generated by the offset of the stator magnetic field. The rotor is moved by the generated tangential force. The delay of flux excitation in the air gap is reduced by a rectifier. The air gap is defined between the inner surface of the stator and the outer surface of the rotor. In response to the magnetic field offset, the decay of the magnetic flux within the rotor is resisted by the current in the rotor windings. The stator magnetic field and the rotor remain synchronized with each other during operation. The current is sent through the stator windings at a current angle measured relative to the nearest one of the rotor magnetic poles. In response to operating conditions, the current amplitude of the sent current is adjusted. In response to operating conditions, the current angle is adjusted.

[0018] In some embodiments, maintaining flux includes resisting a first change in flux by inducing a first current in a first direction in the rotor winding until the first current decreases to zero, and maintaining flux includes allowing a second change in flux to induce a current in a second direction in the rotor winding.

[0019] In some embodiments, the reverse tangential force is reduced by a rectifier.

[0020] In some embodiments, the rectifier includes a diode.

[0021] An example embodiment of the subject matter described in the present disclosure is a wound field rotor synchronous machine having the following features. The stator defines a plurality of stator poles with associated stator windings. The rotor defines a plurality of rotor poles. The rotor is configured to rotate synchronously with the stator. The rotor includes a rotor winding associated with each rotor pole. The rotor winding is configured to be excited by a magnetic field generated by the stator winding to generate a rotor magnetic field. The rotor winding includes a rectifier. Permanent magnets are embedded in the rotor. A controller is configured to excite the stator winding. The controller is configured to generate a stator magnetic field in the stator by sending a control signal to the stator winding, which is achieved by sending a current through the stator winding at a current angle measured relative to the closest rotor pole. The controller is configured to adjust the current angle in response to operating conditions. The controller is configured to adjust the current amplitude of the sent current in response to operating conditions.

[0022] In some embodiments, the permanent magnets are staggered from the rotor poles.

[0023] In some embodiments, the rectifier includes a Schottky diode.

[0024] In some embodiments, the rectifier is configured to reduce torque ripple during operation.

[0025] In some embodiments, the position sensor is configured to detect the position of the rotor relative to the stator. In this case, 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 the presence of torque pulsation in response to receiving the position stream. The controller is further configured to adjust the current angle relative to the rotor pole in response to determining the presence of torque pulsation. The controller is further configured to adjust the current amplitude of the current in response to determining the presence of torque pulsation.

[0026] The details of one or more embodiments 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 DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of an example of an electric drive system.

[0028] Figure 2 is a schematic diagram of an example power switch for an electrical winding.

[0029] Figure 3A-3B are perspective and side views of an example motor.

[0030] Figure 3C-3D are perspective and side views of an example motor.

[0031] Figure 4 is a side view of an example motor.

[0032] Figure 5A is a front view of an example rotor coil.

[0033] Figure 5B yes Figure 5A A perspective view of the rotor coil.

[0034] Figure 5C yes Figure 5A and 5B Side view of the rotor coil.

[0035] Figure 5D is a graph showing various states of charge and resulting torque and different phasor angles under locked rotor conditions (eg, starting).

[0036] Figure 6 is a schematic diagram of an electric motor configured for control according to the present disclosure.

[0037] Figure 7 is a block diagram of an example controller that may be used with aspects of the present disclosure.

[0038] Figure 8 is a flow diagram of a method that may be used with aspects of the present disclosure.

[0039] Fig.9A is a flow chart of a method of responding to a torque increase request according to one aspect of the present disclosure.

[0040] Fig. 9B is another flow chart of a method of responding to a torque increase request according to one aspect of the present disclosure.

[0041] Fig. 9C is a flow chart of a method for starting a motor according to one aspect of the present disclosure.

[0042] Fig.9D is a flow chart of a method of responding to a torque increase request according to one aspect of the present disclosure.

[0043] Fig.10 is a graph of average magnetic field strength for various machine configurations.

[0044] Like reference numbers and numerals in the various drawings represent like elements. DETAILED DESCRIPTION

[0045] The present disclosure relates to a field-wound synchronous motor having a rotor and a stator that are directly coupled electromagnetically. The rotor coils may include rectifiers, such as diodes. Adding a rectifier helps reduce torque pulsation during motor operation. The rotor poles of the rotor are topologically and electrically fixed to the rotor surface. Except for the stator windings, the rotor is substantially energy-isolated from the stator components. That is, the rotor field is configured to be excited by the magnetic field generated by the stator windings. The stator magnetic field and the rotor remain synchronized with each other during operation. During operation, a controller is configured to send current through the stator and actively adjust the current amplitude and angle in response to current or changing operating conditions. This motor can operate with the efficiency of a synchronous motor without the need for expensive rare earth magnets and without the need for separate brushes or excitation circuits to excite the windings within the rotor.

[0046] The motors described herein are characterized by short concentrated windings that define the rotor poles. While the use of short damping bars within the rotor has been proposed for transient damping, they tend to have limited frequency response. In contrast, short concentrated windings can provide effective transient damping over a wider frequency range. In addition, the various motors described in the present disclosure can take advantage of the inherent nonlinearity and asymmetry that occurs during saturation of the rotor backiron. That is, the inductance within the coil becomes asymmetric, resulting in a net torque. Adding a rectifier with the coil further enhances this asymmetry and reduces torque ripple.

[0047] Thus, the present disclosure provides subject matter for controlling an electric motor or motors to achieve a variety of different objectives. For example, the present disclosure provides subject matter for achieving desired operating objectives without requiring or reducing reliance on rare earth elements or wear elements, such as brushes or excitation circuits, or for improving other operating aspects of the system, such as producing a net torque designed to control undesirable torque ripple.

[0048] Figure 1 An electric drive system 100 is shown that includes an electric motor 102 and a motor controller 104 coupled to the electric motor 102. The 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, a wheel, a pump, a compressor, or another motor, wherein multiple motors may be linked and run in parallel.

[0049] The electric motor 102 has an output shaft 107 that is rotatable relative to a motor housing 105, which is considered to be a reference relative to the rotation and other movements of the motor components. In use, the output shaft 107 can be coupled to a load 110, and when electrically activated by appropriate power and signals from the motor controller 104, the electric motor 102 can transfer rotational power to the load 110. The output shaft 107 can extend through the motor and be exposed at both ends, which means that rotational power can be transferred at both ends of the motor. The motor housing 105 can be rotationally symmetrical about the axis of rotation of the output shaft 107, but can be of any external shape, and can generally include a device for fixing the motor housing 105 to other structures to prevent the housing from rotating during operation of the motor.

[0050] The electric motor 102 includes an active magnetic component 106 such as a stator and a passive magnetic component 108 such as a rotor. For illustrative purposes, hereinafter, a stator is used as a representative example of an active magnetic component and a rotor is used as a representative example of a passive magnetic component.

[0051] The rotor 108 is associated with the stator 106 and may be disposed within the stator 106, such as in an internal rotor radial gap motor, or parallel to the stator, such as in an axial gap motor, or in a linear motor. As described more fully below, properly 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 so that any rotational component of the resultant rotor motion is transmitted to the output shaft 107, causing the output shaft 107 to rotate. The stator 106 is fixed to the electric motor 102 so that during operation, the rotor 108 moves around the stator 106 or parallel to the stator 106.

[0052] As described throughout this disclosure, a rectification system 112 may be included, and the rectification system 112 may be implemented in a variety of different ways. For example, the rectification system may be configured to operate passively or actively. In some embodiments, passive rectification may use one or more diodes. In some embodiments, in the case of an active system, the active rectification may include transistors, such as one or more MOSFETs. In some embodiments, when passive components such as one or more diodes are used, the rectification system 112 may be configured as a half-wave rectifier. In some embodiments, for example, when active rectification is used, the rectification system 112 may be configured as a full-wave rectifier.

[0053] Whether active or passive, the inclusion of a rectification system 112 can further mitigate torque ripple by controlling the AC component (specifically, the negative current component) in the rotor coils or windings that may be present under energized conditions. The AC component often appears during the charging phase (low current angles), resulting in reduced surface current density. Rectification substantially eliminates this component and creates a system where the coils flow current only at higher current phasor angles. In some embodiments, the higher current phasor angles are greater than 45 degrees, 65 degrees, or 75 degrees.

[0054] The asymmetric resistance of the rectified system allows for faster current decay in the rotor topology (compared to a non-rectified system). For example, in a fractional slot stator that may have salient poles, faster decay may be desirable to facilitate cycling of charge or flux generation and limit torque ripple. In a motor with a rectified rotor that has a unidirectional passive circuit, such as with a single diode, the current in the winding must be zero in order to inject volt-seconds into the rotor. Oscillation to a low current angle (e.g., less than 45 degrees, less than 35 degrees, or less than 15 degrees) can quickly decay the rotor current to further enable the system to generate flux, or effectively weaken the rotor field for certain operating conditions (e.g., high speed or low torque operation).

[0055] The present disclosure also describes a linear electrical load 114, such as a resistor, or a non-linear electrical load, such as an avalanche diode or a voltage arrester gas discharge tube, connected in parallel with the rectifier system to accelerate the rotor current decay before charging and limit the damage caused by the overvoltage discharge. In some embodiments, one or more linear loads 114 include a resistor with a resistance greater than 100 ohms, 150 ohms, 300 ohms, or 1000 ohms. In some embodiments, the reverse breakdown voltage of the gas discharge tube or avalanche diode is greater than 50 volts, 100 volts, 200 volts, 400 volts, 600 volts, or 800 volts, and the response time is less than 10ms, 5ms, 2ms, 0.5ms, or 0.1ms.

[0056] Current flowing through the loop of wire will produce a substantially uniform magnetomotive force (MMF), thereby generating motor poles within the area wrapped or surrounded. In a typical motor, this loop has a diameter sufficient to carry the desired current load, but is thin enough so that the skin depth of the drive frequency completely penetrates the loop. Many turns or overlapping loops of wire can be used to increase the magnetic field strength of the poles. This topology is often referred to as a wound field pole. Such a set of overlapping loops is called a coil. For the purposes of this disclosure, multiple coils acting together within a stator or rotor are referred to as windings. In some cases, the coils can overlap and surround multiple teeth on the rotor or stator. Such overlapping coils can be called an armature or distributed winding. The pole is the magnetic center of such a distributed winding, and therefore, depending on the drive current flowing through the winding, the pole can move relative to the individual coils within such a distributed winding.

[0057] The stator 106 defines a plurality of stator poles with associated electrical windings, and the rotor 108 includes a plurality of rotor poles, such as the examples shown in more detail throughout the present disclosure. The rotor 108 and the stator 106 together define a nominal air gap between the stator poles and the rotor poles, such as the examples shown in more detail throughout the present disclosure. The rotor 108 can move relative to the stator 106 along a motion direction.

[0058] Figure 2 Another example power switch 200 for a single electrical winding 132 is shown. The power switch 200 may have an H-bridge circuit including four switching elements 202a, 202b, 202c, 202d, with the electrical winding 132 at the center of the H-shaped configuration. The switching elements 202a, 202b, 202c, 202d may be bipolar or FET transistors. Each switching element 202a, 202b, 202c, 202d may be coupled to a respective diode D1, D2, D3, D4. The diode is referred to as a capture diode and may be of the Schottky type. The top end of the bridge is connected to a power source, such as a battery Vbat, and the bottom end is grounded. The gates of the switching elements 202a, 202b, 202c, 202d may be coupled to a winding controller 130, which may be operable to send a corresponding control voltage signal to each switching element 202a, 202b, 202c, 202d. The control voltage signal may be a DC voltage signal or an AC (alternating current) voltage signal.

[0059] The switching elements 202a, 202b, 202c, 202d can be individually controlled by the motor controller 104 and can be independently turned on and off. In some cases, if the switching elements 202a and 202d are turned on, the left lead of the stator is connected to the power supply and the right lead is grounded. Current begins to flow through the stator, exciting the electrical winding 132 in the positive direction. In some cases, if the switching elements 202b and 202c are turned on, the right lead of the stator is connected to the power supply and the left lead is grounded. Current begins to flow through the stator, exciting the electrical winding 132 in the opposite reverse direction. That is, by controlling the switching elements, the electrical winding 132 can be excited / activated in either direction. Although primarily shown and described as using a single-phase H-bridge configuration, a typical six-switch inverter system can be used for a multi-phase motor without departing from the present disclosure.

[0060] The motor controller 104 can 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, as described in further detail throughout this disclosure. The switches can be controlled to sequentially excite the stator poles to generate a localized attractive force that pulls the rotor. This sequential excitation (or activation) can cause the rotor 108, the output shaft 107, and the load 110 to rotate.

[0061] Motor components and controls are sometimes discussed with reference to the D-axis 312 (example shown in FIG. 3 ) and Q-axis of the motor rotor and / or stator. The direct axis or D-axis 312 in the motor can be defined as the centerline of the pole 308 perpendicular to the air gap 314 and can be applied to the stator pole 411 (see FIG. Figure 4 ) or rotor poles 408. As seen in a synchronous reference frame, the rotor can be characterized by the D axis 312 of each pole. In a wound rotor, the D axis 312 is the center point of the combined magnetic center of the coils or field windings, regardless of whether the field windings are concentrated in a single large slot or dispersed in multiple smaller slots. The stator poles can be similarly characterized.

[0062] In the magnetic reference frame, the Q axis is orthogonal to the D axis (i.e., it is electrically 90° to the D axis). Typically, a force along the Q axis will produce an electromotive force, such as torque. Topologically, the Q axis of the rotor or stator is usually directly between the two magnetic poles.

[0063] In such a system, the control signal can be converted to DQ axis components, and a third z-axis component also exists and can be described as a signal or magnetic quantity that does not map directly to the D axis or Q axis, for example, a component that is orthogonal to the plane in which the Q and D components can be found.

[0064] The current phasor angle 318 is the relative angle between the rotor pole D axis 312 and the magnetic center of the stator ( Figure 3A and 3B). A positive current phasor angle indicates that the magnetic center of the stator is ahead of the rotor poles in the direction of motion. This condition causes the magnetic center of the stator to "pull" the rotor poles toward the magnetic center of the stator. Similarly, a negative current angle indicates that the magnetic center of the stator is behind the rotor poles. This condition "pulls" the rotor poles in the opposite direction. This negative current phasor angle 318 can be used in braking situations. In some embodiments, a current phasor angle 318 greater than 90° can be used. Such a large phasor current angle 318 can "push" adjacent poles in the direction of motion. Similarly, a current phasor angle 318 less than -90° can be used to "push" adjacent poles in the opposite direction, such as during braking operations. The following equation can be used to convert the current phasor angle 318 between stationary and synchronous reference frames:

[0065] θ e =(P / 2)θ m (1)

[0066] Among them, θ e is the current phasor angle in the synchronous reference frame, P is the number of stator poles, θ m is the current phasor angle in the stationary reference frame. Regardless of the current phasor angle, it can be decomposed into a D-axis component and a Q-axis component. Typically, for the motors and generators described herein, the D-axis component is used to "charge" or adjust the magnetic field within the rotor poles, while the Q-axis component is used to apply force or torque to the rotor poles. Throughout this disclosure, adjusting the current phasor angle 318 and the current phasor magnitude based on operating conditions is described in detail.

[0067] For example, the current angle, duty cycle, and D-axis to Q-axis current injection can all be changed. In some cases, during the D-axis injection period, an instantaneous D-axis current increase of at least 5%, 10%, 20%, or 30% can be achieved relative to the Q-axis current. In some cases, during the injection cycle, the reduction in the resulting current angle can be achieved, for example, 5-60 degrees, 10-50 degrees, 15-45 degrees, or 22.5-67.5 degrees. In some cases, an injection pulse width between 2-70 ms, 5-50 ms, or 10-25 ms can be used. In some cases, a charging duty cycle of 5%, 10%, 15%, or 25% of the total operating time can be used. In some cases, the current angle transition period from D-axis injection to normal operation is 500 µs to 15 ms, 2 ms-12 ms, or 4 ms-10 ms, determined by the rotor current dropping to zero. In some cases, the change in current angle is less than 15 degrees, 10 degrees, or 5 degrees. In some cases, during D axis injection, the D axis and Q axis amplitudes are simultaneously varied by at least 5%, 10%, 20%, or 30%. The system can be operated as current control or voltage control. For example, regardless of specific operating parameters, the signal can be injected through a current source inverter, where the current injection pulsation amplitude variation is controlled within a desired tolerance.

[0068] As described throughout this disclosure, the coil structure on the rotor receives power / signals from the stator via an inductive coupling, including at least one ring around the rotor pole. In some embodiments, the rotor coil for the conductive ring forms a capacitor, wherein, in some embodiments, the capacitor is formed, inserted or defined by a specific portion of the rotor coil or conductive ring. In some embodiments, the rotor coil or conductive ring includes a resonant frequency. In some embodiments, the resonant frequency of the rotor coil is within the transmittable range of the magnetically permeable pole or rotor coil material.

[0069] In operation, the rotor poles can generate flux through the D-axis signal on the stator, while the coil structure blocks the change of flux on the poles and flows current. The Q-axis signal on the rotor generates torque on the motor that generates flux. In some topologies, such as in a salient-pole winding synchronous motor, the maximum torque per ampere (MTPA) occurs at a current angle between 60-90 degrees. For given operating conditions (e.g., torque and speed), the controller establishes the MTPA (e.g., through a lookup table or a model-based estimator), which includes a combination of the D-axis and Q-axis currents (the main control components) that establish the current phasor angle. The current phasor angle can be modulated or oscillated to periodically maintain the desired level of rotor flux, which can be monitored by an observer or estimator, or established through a model-based approach. When the D-axis is modulated to increase the rotor flux, the amplitude of the Q-axis current can be proportionally modulated to limit torque pulsation and reduce any adverse effects of changing the current phasor angle, or to limit changes in the current phasor angle.

[0070] Figure 3A-3B 300. The motor 300 includes a stator 302 that defines a plurality of stator poles with associated stator windings 304. A "motor pole" can be described as a topological portion on a stator or rotor that emits a unipolar magnetic flux across an air gap at a given point in time. When determining the number or location of poles for an electric motor, the magnetic flux carried in the back iron of the stator or rotor is taken into account. The poles are typically characterized by high field regions that can exceed 5000 gauss. The poles can come from permanent magnets or electromagnetic fields. Although the number of poles on a stator or rotor is typically fixed during manufacturing, in some embodiments described herein, the number of poles of the rotor, stator, or both can be changed during operation.

[0071] Although the presently illustrated stator 302 is presently illustrated as having distributed windings 304, convex, centralized, and / or non-overlapping stators may similarly be used without departing from the present disclosure. The rotor 306 defines a plurality of rotor poles 308 having associated rotor coils 310. Although the illustrated embodiment includes 1 / 3 of the rotor teeth compared to the stator teeth, other ratios may be used without departing from the present disclosure, for example, the rotor may include 1 / 2 of the teeth present in the stator. In some embodiments, the rotor may include 1 / 4 of the teeth present in the stator. Other ratios of rotor teeth to stator teeth may be used without departing from the present disclosure, regardless of whether convex centralized stator windings are used or whether distributed stator windings are used.

[0072] As shown, each rotor coil 310 is short-circuited to a rectifier 311. Although each coil 310 is shown with a rectifier, other arrangements may be used without departing from the present disclosure. For example, a plurality of rotor coils may be electrically connected in series or in parallel to a single rectifier. In some embodiments, the rectifier 311 may include a diode. Several types of diodes may be used, such as a pn junction diode, a gas diode, a Zener diode, or a Schottky diode. In some embodiments, when a Schottky diode is used, the Schottky diode may be a silicon carbide diode. The choice of diode depends on a variety of 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 have been listed, other diodes may be used without departing from the present disclosure. The rectifier only allows current to flow through each rotor coil 310 in a single direction.

[0073] The rotor poles 308 are topologically and electrically fixed on the rotor surface. A fixed pole rotor is a rotor 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 will always rotate at substantially the same speed as the drive frequency provided by the stator, or synchronously with the drive frequency provided by the stator (taking into account the inherent level of torque pulsation). The synchronous reference frame is the same as the magnetic reference frame. Therefore, fixed pole motors are often referred to as "synchronous" motors. Field wound rotors, surface PM rotors, reluctance motors, and internal PM rotors are all examples of fixed pole rotors. The fixed pole rotor design maximizes the utilization of ferromagnetic material in the rotor D axis 312 area (the center of the rotor poles), and in the case of a wound excited rotor, ensures that the effective magnetic center is aligned with the D axis 312. Therefore, for a given size and power rating, a fixed pole rotor is considered more efficient than a moving pole rotor; however, a fixed pole rotor is difficult to control because it is challenging to maintain the fixed pole rotor at a constant current phasor angle under dynamic load conditions and dynamic operating speeds. For example, accelerating the motor or maintaining speed during load changes includes actively adjusting the current phasor angle 318, current amplitude, and / or drive frequency based on input from the position sensor 316. The concepts described herein are primarily applicable to synchronous motors because the stator field and the rotor (e.g., rotor 306) remain synchronized with each other during operation.

[0074] In contrast, the poles of a changing pole rotor are not topologically or electromagnetically fixed, but move relative to a stationary reference frame during operation. That is, the rotor will always "slip" and lag behind or become asynchronous with the drive frequency provided by the stator. For this reason, these motors are often referred to as "asynchronous" motors. Examples of changing pole rotors include wound and squirrel cage induction rotors, armature wound rotors, brushed motors, and other similar motors. While the shifting pole rotor is able to self-regulate the current phasor angle 318 during operation, a design compromise must be made between the D-axis ferromagnetic material and the Q-axis field windings to enable the poles to move evenly across the rotor surface. Therefore, in a changing pole rotor of a given size and power rating, such a motor has a higher resistance, requires a larger starting current, and has a lower field strength.

[0075] The 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 field. Except for the stator windings 304, the rotor 306 is substantially energy isolated from the components of the stator 302.

[0076] In an electric machine, the stator and rotor may be coupled to enable power transfer, signal transmission, and / or field modulation during operation. Coupling may be classified as direct or indirect. Direct coupling occurs between the stator and rotor along a primary operating air gap, such as air gap 314. Indirect coupling occurs along a secondary interface away from the primary operating air gap.

[0077] Direct coupling is often characterized as an inductive coupling, e.g., a squirrel cage induction rotor is considered to be directly coupled to the stator. While direct coupling is common and easy to control in asynchronous machines, direct coupling to synchronous machines is difficult to control for reasons described in this disclosure. For example, it is often necessary to know the rotor position to ensure that current amplitude and / or frequency are properly maintained.

[0078] The indirect coupling runs along the secondary coupling and may be radially oriented or axially oriented and may communicate via electrical contact, inductive coupling along a separate air gap, capacitive coupling, or optical coupling. While the secondary coupling may be used for a variety of functions to improve the efficiency and / or overall controllability of the motor, additional components are often required which can increase the weight, complexity, failure frequency, and cost (operating and capital) of a machine utilizing such a system.

[0079] The couplings can be further classified as power couplings or signal couplings. Power couplings transfer power from the stator to the rotor for direct driving of the magnetomotive force along the primary operating air gap, thereby generating torque. Signal couplings transfer signals between the stator and rotor that can be used to individually adjust circuits within the rotor or detect rotor conditions, such as temperature or position relative to a stationary reference frame. Signal couplings transfer power at very low power levels relative to the rated power of the motor, for example, less than 5% of the rated power of the motor. In some embodiments or under some operating parameters, it may be desirable for the signal coupling to transfer power at a level relative to the rated power of the motor, for example, 7.5%, 5%, 3%, or 2.5%.

[0080] Energy-isolated motors and generators, such as those described throughout this disclosure, primarily use direct coupling (within standard electromagnetic shielding tolerances) to transmit power and signals between the stator and rotor, without using indirect or secondary coupling. The electric machine described herein includes a direct coupling between the rotor 306 and the stator 302 for both power and signal coupling.

[0081] In some embodiments, when located at Figure 3BThe wound rotor may need to be charged or benefit from being charged when operating in position D as shown, or when transitioning from position D to position Q by modulation of the current phasor angle. Charging may mean generating 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. This task may be accomplished in a variety of ways, for example, by advancing the current phasor angle of the stator excitation (e.g., appropriately advancing or retarding the current angle of the stator excitation), increasing the frequency of variation of the stator excitation current phasor angle, increasing the amplitude of the excitation current in the stator (or any of its resultant signal components), or any combination thereof. In some cases, the rotor magnetic field may need to be weakened (e.g., reducing the level of current or magnetic flux present in the rotor and / or rotor field windings), for example, when operating at or near position D' (e.g., by transitioning from position Q to position D', or from position D' to Q'). This task can be accomplished in a variety of ways, such as modulating the current phasor angle (e.g., appropriately advancing or retarding the current angle of the stator excitation), reducing the frequency of the stator excitation current angle phasor changes, reducing the amplitude of the excitation excitation in the stator (or any of its resultant signal components), or any combination thereof. Alternatively or additionally, field weakening can be achieved by passive losses in the rotor field winding current due to ohmic losses. In operation, in some embodiments, frequency and harmonic independence between the signal emitted by the stator and the fundamental operating frequency that determines the rotor speed can be observed. As will be described, the present disclosure recognizes that control of the motor can be achieved in such a way that, in addition to simply moving the rotor, additional objectives are prioritized, such as increasing the efficiency of the system, controlling losses in the system, or mitigating the possibility of operating conditions that may damage or reduce the efficiency of the system. Further details regarding such a system are described in the present disclosure, for example, Figure 6 and related descriptions.

[0082] Figure 3C-3D 350 are perspective and side views of an example motor 350. Motor 350 is substantially similar to motor 300 except for any differences described herein. Rotor 356 includes six rotor poles 358. Stator 352 includes distributed windings 354. Motor 350 has six rotor teeth (poles 358) and thirty-six stator teeth 370, resulting in a rotor tooth to stator tooth ratio of 1:6. This is different from electric motor 300, which includes four rotor teeth (poles 308) and twelve stator teeth 320, resulting in a rotor tooth to stator tooth ratio of 1:3. Other rotor tooth to stator tooth ratios may be used without departing from the present disclosure, for example, a ratio of 1:2 or 1:4 may also be used. Other rotor tooth to stator tooth ratios may be used without departing from the present disclosure, regardless of whether a convex concentrated stator winding is used or whether a distributed stator winding is used.

[0083] Figure 4 4 is a side view of an example motor 400. Except for any differences described herein, the motor 400 is substantially similar to the motor 300 described previously. The rotor 406 is an external rotor, and the stator 402 is an internal stator. In other words, the rotor 406 rotates around the stator 402 and around the stationary stator 402. The stator 402 defines a stator pole 411 having a concentrated, convex, non-overlapping stator coil 404. The rotor 406 includes a permanent magnetic material 416 embedded in the rotor 406. As shown, each rotor pole 408 includes four channels of permanent magnetic material 416, which are arranged in a generally "M" or "W" shaped configuration; however, other arrangements may be used without departing from the present disclosure. The permanent magnetic material 416 may include a variety of materials, including ferrite, SmFeN, N35, N45. Although lower power permanent magnetic materials are generally used, a lower number of higher power magnetic materials may be used without departing from the present disclosure. Permanent magnetic material 416 may extend across the entire longitudinal length of each rotor pole 408, or partially across each rotor pole 408. In some embodiments, permanent magnetic material 416 may be comprised of multiple layers or laminations.

[0084] As shown, the permanent magnetic material 416 produces a net magnetic force that is substantially aligned with each rotor pole 408. In some embodiments, the permanent magnetic material can be arranged so that the net magnetic force from the permanent magnetic material 416 is staggered with the rotor poles 408. Generally, the arrangement of the permanent magnetic material depends on the desired cross-sectional flux density of the magnetic material within the rotor. In an embodiment where the permanent magnetic material 416 is located within the rotor coils 310, the flux for each group of permanent magnetic material 416 can be individually adjusted and / or modulated by adjusting the charging of the surrounding rotor coils 310. This embodiment also protects the magnets from demagnetization caused by strong stator fields. In an embodiment where the permanent magnetic material 416 is not surrounded by rotor coils, the flux regulation caused by the stator field can affect multiple groups of permanent magnetic material 416 within the rotor 406.

[0085] Figures 5A-5C 3 are front, side and perspective views of an exemplary rotor coil 310. Figure 3A , 3BAs shown in Figures 4 and 5, each rotor coil 310 acts as its own winding, with a single coil surrounding each pole, such as rotor pole 308 or 408. In this way, the rotor can be described as including concentrated, convex and / or non-overlapping windings. In some embodiments, the winding direction of each coil can alternate with each adjacent rotor pole 308 or 408. For example, in an embodiment using a stator with convex, concentrated and / or non-overlapping windings, this arrangement can be used. Alternatively, the rectifier 311 can alternate with each adjacent pole, with similar results. In some embodiments, the winding direction does not need to alternate between adjacent rotor poles. For example, in an embodiment using a stator with distributed windings, this arrangement can be used. Although the rotor coil 310 is shown as a single coil short-circuited by itself, other geometries can also be used, as long as each coil is short-circuited by itself and does not overlap with adjacent coils. In some embodiments, poles with the same polarity can be short-circuited to each other, for example, to share a rectifier. Similarly, poles with opposite polarity can short circuit each other, depending on the winding direction of each pole. Typically, the rotor coils are often configured so that the current skin depth at the power transmission frequency fully penetrates the conductor of the coil. In the context of this disclosure, "current skin depth" refers to the depth from the surface of the conductor where current primarily flows, especially eddy currents induced by a magnetic field that varies at a given frequency. For a given material, the skin depth can be calculated as:

[0086] δ ≈1 / √πfμσ(2)

[0087] Where '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 embodiments, the drive frequency may extend between 0 Hz and 20 Hz. In some embodiments, the drive frequency may range between 100 Hz and 2000 Hz. Typically, the rotor coils are arranged such that the decay of the magnetic flux within the rotor is resisted by current within the rotor coils in response to magnetic field excursions from the stator.

[0088] Conventionally, synchronous motors do not have a magnetizing current to magnetize the material, so the magnets must be magnetized at the factory or before installation. For this reason, if the magnetic material demagnetizes during operation (for example, because the stator places too much load on it), the magnets can be damaged or the motor can fail to operate at all. The rotor coils 310 help protect the permanent magnets from potential demagnetization by the stator.

[0089] The rectifier 311 in each rotor coil 310 helps to reduce the torque pulsation in the motor during operation. The rectifier achieves this by reducing the delay of flux excitation in the air gap 314. Although the rotor coil 310 resists the attenuation of the magnetic flux in the rotor by the current in the rotor winding in response to the magnetic field offset, the rotor coil 310 performs this function without rectification, regardless of which part of the drive cycle the rotor coil 310 is in. That is, the unrectified rotor coil is symmetrical for both the positive part of the drive frequency and the negative part of the drive frequency. This arrangement can produce a measurable amount of torque pulsation. For the rotor coil 310 including the rectifier 311, the rotor coil 310 allows a first change in flux by inducing a first current in a first direction in the rotor winding until the first current is reduced to zero, and allows a second change in flux to induce a current in a second direction in the rotor winding. That is, the current in the rotor winding is unidirectional, thereby producing an asymmetric response and reducing torque pulsation during operation.

[0090] In operation, the current flowing through the coils (310, 410) and rectifiers is allowed to decrease to zero. This operation is performed by reducing the current phasor angle 318 to less than 90° (i.e., "pulling" the pole instead of "pushing" the next adjacent pole). The current in the coils (310, 410) and rectifier 311 is allowed to decay for a duration that the current phasor angle is less than 90°. Depending on the speed and saturation of the rotor (306, 406), this duration can range from a few milliseconds to two seconds. The current phasor angle then increases as the current in the coils (310, 410) increases. Throughout this process, the current amplitude can be modulated in conjunction with the current phasor angle 318 to offset pulsating current when the phasor angle 318 is adjusted.

[0091] Figure 5D 5 is a graph 550 showing various states of charge 552 and resulting torque 554 under locked rotor conditions (e.g., starting) and different phasor angles 556. At high current angles (left side), the rotor current 558 is shown to be highly reactive to the transient stator current excitation. When operating between the Q axis (90°) and the D axis (0°), high levels of charge 552 can be seen with considerable inductive decay (e.g., holding field).

[0092] Due to the low concentration of stator Q axis current, torque 554 is shown as being relatively at high current angle 556. The attenuation can be observed by the current 558 flowing through the rotor coils (310, 410) to resist the flux changes. Under this control scheme (in combination with coils 310 or 410), the rotor magnetic field can be modulated based on the current phasor angle 556. This can translate into a wide operating range during operation. As can be seen in the curve graph 550, the operation of the D axis 312 to the Q axis demonstrates a shielding effect that will protect the magnetic material, which allows less magnetic material, lower coercive force material, or both. As the stator Q axis current increases, the rotor current is shown to have a greater contribution to torque generation (130-120 degrees). At 90 degrees, the current is transverse to the rotor D axis and no net current is generated.

[0093] Another benefit is that the field weakening of the D axis injection is not constant compared to a permanent magnet motor. Similarly, the rotor magnetic field can be modulated by the current amplitude flowing through the stator. In many cases, the current amplitude and the current phasor angle 556 can be adjusted simultaneously to achieve the desired rotor magnetic field modulation. Due to the presence of the rectifier circuit, the rotor current with a phasor angle less than 90 degrees appears to be in an anti-periodic relationship with the excitation current. The rotor magnetic field increases during these periods due to the reactive field decay between the net D axis injection and the stator excitation.

[0094] Control can be used to further limit torque ripple by modulating the current phasor angle for a desired rotor magnetic field modulation. The rotor flux can be transferred from the stator to the rotor by modulation of the motor on the D axis in a synchronous reference frame. This current magnitude or amplitude modulation can change (reduce) the current phasor angle at the modulation frequency over the modulation duration. Higher modulation frequencies can further reduce torque ripple, particularly of systems where higher frequency harmonics are damped and / or filtered by the system, which can include inertial masses of the powertrain or vehicle loads, or even the rotor itself.

[0095] In some cases, torque ripple is also limited or significantly reduced by modulating the current magnitude or amplitude on the D axis of the motor in a synchronous reference frame while considering a desired current angle suitable for maximum torque production. In this case, the controller modulates the current magnitude or amplitude on the Q axis in the synchronous reference frame proportionally relative to the modulation on the D axis. In some cases, this proportional modulation of the Q axis amplitude is 5-10%, 10-20%, 20-40%, or 50-100% of the D axis modulation. In some cases, a certain oscillation tolerance is allowed around the set or desired current angle to produce maximum torque. In some cases, this tolerance is 0-1%, 0-5%, 5-10%, 10-30%, or 30-60% variation relative to the set current angle. Assuming that the controller has provided sufficient priority to maintain the rotor magnetic field at the appropriate flux level, the smaller the oscillation tolerance, the tighter the controller can control the torque ripple. These oscillation tolerances can also be described as the duty cycle of the stator excitation.

[0096] To further describe this control scheme, Figure 6 A schematic diagram of an electric motor 600 is shown with alignment between a rotor 602 and a stator 604. Position D is defined as relative stator 604 and rotor 602 pole alignment (i.e., NS and SN). Positions Q and Q' are defined as completely misaligned poles (i.e., close to similar poles and opposite poles, respectively), or electrically orthogonal to D and D', as similar stator 604 and rotor 602 poles are aligned (i.e., NN and SS). In some embodiments, particularly in rotors with high saliency, peak torque occurs between the D and Q positions in a synchronous reference frame (e.g., due to their reluctance component). In other embodiments such as circular rotors (e.g., less convex machines), peak torque occurs between the Q and D' positions. In the case of permanent magnet motors, peak torque operation can result in demagnetization at high loads and the need to weaken the magnetic field at high speeds. Weaker magnets can be used to the detriment of size / weight and / or torque generation.

[0097] In some embodiments, permanent magnets may be used. In order to increase the magnetic flux capacity without the risk of demagnetization, the rotor windings described herein are used. At lower torques, the rotor winding current reduction can be allowed to reduce the cogging (resistive) torque and eliminate the need for active flux weakening of stronger permanent magnets. By using the modulation of the current phasor angle of the present invention, a wound rotor can be flux weakened or enhanced through a control mechanism (e.g., the current in the rotor field winding is reduced or increased and the flux in the rotor poles themselves). As a non-limiting example, the current phasor angle of the synchronous excitation from the stator 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, such as for controlling the stator magnetic field).

[0098] As described herein, the wound rotor configuration according to the present disclosure does not require additional stator-rotor coupling elements. Instead, the stator windings and rotor windings and rotor laminations are used to transmit signals. This reduces cost and component parts, improves performance (e.g., eliminates ohmic losses of brushes), eliminates or controls physical contact and wear parts, reduces packaging size, and provides control flexibility compared to solutions that incorporate special detectors, sensors, wired or wireless connections, or brushes to transmit signals from the stator to the rotor.

[0099] As described throughout this disclosure, in systems where control signals can be converted into DQ axis components, such as Figure 6 As shown, a third z-axis component also exists and can be described as a signal or magnetic quantity that does not map directly onto the D axis or the Q axis. For example, as shown, a component that is orthogonal to the plane in which the Q and D components can be defined.

[0100] In operation, field oriented or vector control with specific modulation (e.g., signal or signal parameter modulation) can be used to control various aspects of the rotor field. These modulations can be used to adjust the signal excitation coupled between the stator and the rotor, as well as control the stator excitation wave relative to the rotor (e.g., relative position and amplitude). Thus, the stator and inverter can effectively "steer" the rotor response or the direct correlation of the current induced in the rotor windings. In other words, such control can produce the dynamic behavior of the machine, which is a function of the current in the D-axis and Q-axis fields, which is controlled by a controller such as controller 104 or controller 700 ( Figure 7 ) coordination. In other strategies (e.g., torque generation), vector modulation can be used to help define the modulation of the current phasor angle.

[0101] The present disclosure recognizes that vector control modulation can be used to directly affect rotor reactions through applied stator signals. In addition, these rotor reactions can be modulated on the D axis or Q axis and can be achieved using current phasor angle modulation. The relative effectiveness of the current phasor angle modulation can be proportional to the amplitude and percentage change (e.g., over a period of time) of the modulation. The speed of adjusting the current phasor angle can be varied on the controller and can be selected based on the expected response of the rotor material or the rotor response. In some cases, the frequency can be selected based on the speed of the machine, while in other cases, a fixed modulation can be selected. The frequency of the modulation can be selected based on various considerations. For example, in some configurations, the frequency can be at least 2-4 times higher than the fundamental frequency of the machine. In other cases, the modulation can be 5-10 times higher than the fundamental frequency of the machine. In further configurations, the frequency can be 10-30 times higher than the fundamental frequency of the machine. For example, in some configurations, the frequency can be selected to prevent interaction with torque generation (e.g., reduce torque pulsation).

[0102] The current phasor angle can be controlled using vector component control, which can be achieved by letting i d 、i q and i z is Figure 6 The stator current is described by the current at the fundamental frequency represented in the DQ reference frame shown (e.g., including the main control component of the current phasor angle). These signals can be modulated directly, or alternatively, an independent excitation modulation can be added on either D / Q axis, which is superimposed on the fundamental current to produce the total stator current:

[0103] (3)

[0104] (4)

[0105] (5)

[0106] Among them, i d 、i q and i z is the normal excitation current along each axis, , and is an independent modulation signal that can be selected and controlled by a motor controller or other controller, as will be discussed further. The modulation can be selected to be sinusoidal or take any form, for example, such modulation can be further described as:

[0107] (6)

[0108] (7)

[0109] (8)

[0110] The modulation amplitude and frequency can be selected independently for each component and the vector sum to change the current phasor angle, or the main component can be changed by directly controlling the current phasor angle (γ):

[0111] (9)

[0112] (10)

[0113] (11)

[0114] Similarly, the set current phasor angle can be modulated, for example:

[0115] (12)

[0116] (13)

[0117] (12)

[0118] in, It can be described, for example, as a sinusoidal oscillation around a fixed current angle:

[0119] (13)

[0120] (14)

[0121] (15)

[0122] In each case, modulation can be applied to a single axis without applying modulation to the other two axes and used to produce a rotor response. Alternatively or additionally, D-axis current modulation can be used, or D-axis current modulation can be varied together with Q-axis current modulation, with the goal of controlling or minimizing torque pulsation. If D-axis modulation is not sufficient, Q-axis modulation can be used. In some embodiments, Q-axis modulation is used in conjunction with D-axis modulation to form a rotating vector injection. Z-axis modulation itself does not affect torque pulsation and does not require knowledge of the DQ reference system. However, the effect of Z-axis modulation on the rotor is often limited, but can be used to couple the stator to the rotor for power or accessory information coupling (e.g., speed and / or position).

[0123] The frequency of the current modulation or the current phasor oscillation can be described by a duty cycle. The duty cycle can describe the operation divided between the main components of flux generation (e.g., D axis) and torque generation (e.g., Q axis). Under starting conditions, the duty cycle on the D axis can be 100%, or 75-100%, or 40-100%, which is used to generate hard flux on the rotor before the operation is separated between the D axis and the Q axis to produce torque, where there can be 50%-50% separation, 30%-70%, 20%-80%, 10%-90% separation (D axis: Q axis). This can also be manifested as an oscillation around the current phasor angle, where the current phasor angle and the resultant magnetic field vary around an angle of 5 degrees, 10 degrees, 20 degrees, or in some cases 30-45 degrees during steady-state or quasi-steady-state operation. In some embodiments, the frequency of the oscillation or amplitude modulation can be varied to cause rotor response and / or limit torque pulsations in operation.

[0124] Additionally, the control strategy may utilize higher frequency operation or pulsing to limit the amount of flux in the rotor coils that decays over time. That is, by shortening the time step between the rotor's MMF cycles (which decay over time), the change in flux through the rotor coils may be reduced to harden the flux and reduce any negative torque or associated torque ripple. Additional signal modifications such as skew signals, trapezoidal or pulse width modulation (PWM) techniques may be used to help flux produce the rotor, limit torque ripple and smooth the transition between current phasor angles on the fly.

[0125] Because the stator side current can correspond to the stator side voltage, the scheme including the signal embedded in the current can correspond to the equivalent scheme including the signal embedded in the voltage. Throughout this disclosure, the embodiments described with reference to the signal in the stator side voltage can be equivalent to and can also describe the signal in the stator side current, and vice versa.

[0126] As previously described, control of the rotor field can be manipulated by the controller through the stator windings using current phasor angle modulation. This modulation can be defined by amplitude and frequency and can be observed through the magnetic field, stator excitation, and main control components of the machine. Current phasor angle modulation can be used to transfer power to the AC coil, where the oscillation of the current angle is defined around a set operating point of the current angle defined by the DQ reference frame (for example, the current angle can be modulated to achieve a target torque per ampere MTPA). Current phasor angle modulation disturbances can be defined by the oscillation, amplitude, and frequency of the excitation field. Current amplitude modulation at a given current phasor angle can be used to transfer power to the rotor or induce a reaction in the rotor, where the maximum response can be seen at the current angle (in the DQ reference frame of a given magnetic pole) that is most coupled to the rotor. For example, for a wound rotor aligned with the D axis relative to the synchronous reference frame axis, the maximum power transfer will occur at a phasor current angle of 0° electrical angle (where 0° electrical angle is defined as the D axis of the synchronous reference frame).

[0127] In some embodiments, the alternating direction of commutation effectively means that the polarity of each rotor pole is opposite to that of its neighbor. In other words, a four-pole motor has NSNS. Alternatively, to achieve this alternating pole arrangement, the direction of the winding can be reversed from pole to pole to establish the proper polarity (e.g., when a single coil and rectifier is used). Alternatively, a unidirectional winding can be used, where the rectifier itself is flipped in direction from pole to pole to provide the proper polarity on the rotor.

[0128] In some embodiments, rotor coil windings, either singly or in parallel, are used to establish local flux conditions within the motor. In some embodiments, rotor coil windings, either in groups or in series, are used to balance rotor currents and fluxes on the motor. This can be done as a function of the motor's periodicity or symmetry. Combinations of singly and in groups, in parallel and in series, can be used to achieve control of local areas and distributed balancing on the rotor or motor.

[0129] Figure 7 is a block diagram of an example controller 700 that may be used with aspects of the present disclosure. The controller 700 may be used in addition to or in place of the aforementioned motor controller 104. In the former case, the controller 700 and the motor controller 104 may be combined into a single integrated controller, or the controller 700 and the motor controller 104 may be separate, discrete controllers. The controller 700 may, among other things, monitor parameters of the motors (300, 400) and send signals to actuate and / or adjust various operating parameters of the motors (300, 400). Figure 7 As shown, in some cases, the controller 700 includes a processor 750 (e.g., implemented as one or more processors) and a memory 752 (e.g., implemented as one or more memories), the memory 752 containing instructions for causing the processor 750 to perform the operations described herein. The processor 750 is connected to an input / output (I / O) interface 754 for sending and receiving communications with components in the motor (300, 400), including, for example, a rotor position sensor or a current sensor. In some cases, the controller 700 may additionally communicate status with one or more of the various motor components of the motor (300, 400) and other sensors (e.g., temperature sensors, vibration sensors, and other types of sensors) disposed in the motor (300, 400) and send actuation and / or control signals (including power or drive signals to the stator) thereto. The communication may be hardwired, wireless, or a combination of wired and wireless. In some embodiments, the controller 700 may be a distributed controller, with different parts of which are located in different locations, such as different sections of a vehicle. Additional controllers may be used in conjunction with controller 700 , either as stand-alone controllers or as networked controllers, without departing from the present disclosure.

[0130] The controller 700 may have different levels of autonomy for controlling the motors (300, 400). For example, the controller 700 may begin sensing a change in load and / or speed, and the operator adjusts the power frequency, current amplitude, and / or current angle. Alternatively, the controller 700 may begin sensing a change in load and / or speed, receive additional input from the operator, and adjust the frequency, current amplitude, and / or current angle without further input from the operator. Alternatively, the controller 700 may begin sensing a change in load and / or speed, and adjust the frequency, current amplitude, and / or current angle without input from the operator.

[0131] For example, in operation, the controller may be a controller configured to excite the stator windings and generate a stator magnetic field in the stator by sending control signals to the stator windings. The controller may be configured to generate a stator magnetic field by sending current through the stator at a current angle and amplitude, and actively adjust the current angle and amplitude according to the operating conditions of the motor (300, 400). Alternatively or additionally, the controller may receive a position stream from a position sensor 316. The position stream represents the rotor position. The position stream may be an analog or digital electrical signal or an electromagnetic signal. In response to receiving the position stream, the controller may determine the presence, absence, or severity of any torque pulsation that exists. The controller may then adjust the current angle and / or current amplitude in response to determining that there is a torque pulsation.

[0132] In some embodiments, the phasor current angle 318 increases in the direction of motion ahead of the rotor poles (308, 408) during high torque conditions. That is, an increased phasor current angle 318 may result in situations where a greater current per unit of torque is required. Generally, as the current phasor angle 318 increases, the rotor coils (310, 410) become more active (more current flows through the coils) due to the reduction in the D-axis component 312. In other words, as the current phasor angle 318 increases, the field of each rotor winding decays faster. Greater activity within the coils results in increased torque pulsations without mitigation; however, during the increase in the D-axis component experienced by each pole, the current amplitude may increase, thereby offsetting the potential negative torque generated by the increased current angle 318. Alternatively or additionally, the phasor current angle 318 decreases during high speed, low torque operation. Alternatively or additionally, the current angle may become negative during braking operations. Regardless of the operating mode used, the controller 700 is capable of adjusting the current angle and / or current amplitude to meet the current demands of the motor (300, 400) in a given situation.

[0133] In particular, the current phasor angle or current amplitude of the main components of the machine can be adjusted in operation to produce torque. In some cases, for example, when the rotor has sufficient magnetic field strength, no magnetizing current may be applied (or less magnetizing current may be applied) compared to the previous time step. In other cases, such as when running at high speeds, the rotor magnetic field may be allowed to degrade to reduce back electromotive force (EMF) and provide voltage margin, reduce cogging torque to limit torque pulsation, and avoid active field weakening operation. The controller is capable of communicating with the rotor through the stator at a wide range of frequencies, such as between 50 and 1000 Hertz (Hz). In some embodiments, communication occurs between 100 and 1000 Hz. Regardless, the system is able to communicate changes faster than conventional systems. For example, conventional squirrel cage induction motors communicate essentially at 7 Hz. The ability to transmit at higher frequencies allows the controller 700 to actively reduce torque pulsation regardless of operating conditions and quickly adjust to changes in operating conditions.

[0134] Figure 8 800 may be used with aspects of the present disclosure. All or part of the method 800 may be performed by the controller 800 and / or the motor controller 104. At 802, stator windings of a stator are energized to generate a stator magnetic field within the stator. At 804, a corresponding rotor magnetic field within a ferromagnetic material within a rotor is modified by the stator magnetic field. At 806, the offset of the stator magnetic field generates a force tangential to the rotor. At 808, the rotor is moved by the generated tangential force. The stator magnetic field and the rotor remain synchronized with each other during operation. At 810, a delay in flux excitation in an air gap is reduced by a rectifier. The air gap is defined by an inner surface of the stator and an outer surface of the rotor.

[0135] At 812, in response to the magnetic field shift, current within the rotor coil resists the decay of magnetic flux within the rotor. Due to the inclusion of rectifiers 311 on individual rotor coils 310, the resistance in flux decay is asymmetric. Thus, a first change in flux is resisted by inducing a first current in a first direction within the rotor winding until the first current decreases to zero, and a second change in flux is allowed to induce a current in a second direction within the rotor winding.

[0136] In some cases, at 814, current is sent through the stator at a current angle. Typically, the current angle is located ahead of the rotor poles in the direction of motion. In some cases, at 816, the current amplitude of the current is adjusted in response to the changing operating conditions. At 818, the current angle relative to the rotor poles (D axis) is adjusted in response to the changing operating conditions. In particular, 814 and 816 are shown in dashed form because these two steps are not required and are not required in this order. That is, the current amplitude and current angle can be adjusted independently.

[0137] Thereafter, the operation output of the motor at the current time is compared with the expected operation output of the motor. If the operation output of the motor at the current moment is at the expected operation output of the motor, the motor continues to operate using the most recently adjusted stator current parameter. If not, the process is repeated to return to adjust at least one of the current amplitude or current angle of the stator current until the operation output of the motor at the current time is at the expected operation output of the motor.

[0138] Reference now Fig.9A , provides a non-limiting example of process control according to the present disclosure. In particular, Fig.9A An example flow chart of controlling a motor system to deliver increased torque 900 according to the present disclosure is provided. Process 900 begins with a request or request for increased torque at 902. According to the present disclosure, satisfying the request can be conceptualized as executing two parallel work flows. However, in practice, the controller does not need to be programmed or designed to operate in independent, parallel or different flows. To satisfy the request for increased torque 902, the controller determines that the increased torque can be achieved by increasing the rotor flux at 904. To this end, Id is increased at 906, which increases the rotor flux at 908. This continues until the desired rotor torque is reached, and then Id is reduced at 910. However, in seeking to increase the rotor flux, the controller recognizes that Q axis current modulation can be used, or varied with D axis current modulation, in order to control or minimize torque pulsation. Therefore, at 912, the controller also works to maintain torque performance. To this end, the controller also adjusts Iq at 914, thereby producing the desired torque increase at 916, but without the adverse effects of unstable torque performance, such as the adverse effects of unstable torque performance caused by torque pulsation.

[0139] Reference now Fig. 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 the increased torque can be achieved by requesting an increase in rotor flux at 922. To achieve this, the controller seeks to modulate the current angle toward the D axis at 924, as this will easily increase the rotor flux at 924, which is further controlled by modulating the current angle toward the Q axis at 928. In parallel, the controller maintains torque performance by modulating Iq at 930, as described above. Therefore, as a result, at 934, the requested torque increase is delivered to.

[0140] Reference now Fig. 9C, another non-limiting example of a control process for reaching a desired torque from startup is provided at 936. At startup, the rotor is locked at 938. To begin rotation, at 940, the current angle is modulated toward the D axis, and at 942, as the rotor moves toward the D axis, the rotor flux builds or increases. At 944, the current angle is modulated toward the Q axis, and the process continues until the desired torque is produced at 946.

[0141] Fig.9D Yet another non-limiting example of a control process for achieving a desired torque at 948 is provided. In this case, the process begins with the motor already at high speed operation 950. At 952, the duty cycle of the current angle modulation is reduced, and at 954, the amplitude of the current modulation is reduced. As a result, the rotor flux decreases at 956. As the rotor flux decreases, at 958, the back EMF decreases, and at 960, the cogging torque decreases. Given the high operating speed of the motor at 950, this control ultimately produces an increase in torque at 962.

[0142] Thus, the described systems and methods show a net increase in torque developed with sinusoidal excitation due to net rotor field D-axis current injection resulting from the asymmetric flux vector of the rotor field lines along the stator D-axis. Net D-axis current injection is therefore feasible in conventional circuits with analog circuits. The motor with the rotor coil structure will be less saturated, presenting a net benefit of shorting the coils in terms of average torque production. Net D-axis current injection enables greater surface current density to be achieved with equivalent stator excitation due to the reactive rotor coil current.

[0143] Thus, certain embodiments of the subject matter have been described. Other embodiments 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 the desired results. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the particular order shown, or sequential order, to achieve the desired results.

Claims

1. A method for controlling a motor, the method comprising: exciting a stator winding of a stator of the electric machine by means of a stator current; A stator magnetic field is generated in the stator by the energized stator winding; generating a corresponding rotor magnetic field in a ferromagnetic material within a rotor of the electric machine via the stator magnetic field, the rotor defining a plurality of rotor poles and including a rotor winding associated with each of the rotor poles; generating a force tangential to the rotor by a shift in the stator magnetic field; moving the rotor by a force generated tangentially to the rotor, wherein the stator field and the rotor remain synchronized with each other during operation of the motor; reducing the attenuation of flux excitation in an air gap between the stator and the rotor by means of a commutator included in the rotor winding; In response to the displacement of the stator magnetic field, resisting the decay of the magnetic flux in the rotor by current in the rotor winding; and Achieving a target operating output of the motor.

2. The method according to claim 1, wherein: The electric machine includes a rectifier system including a respective rectifier arranged across each rotor pole, and The rectifier system is configured to control the alternating current induced in the rotor poles when the corresponding rotor magnetic field is excited by the stator magnetic field.

3. The method according to claim 1, wherein: Attenuation of the flux excitation in the air gap between the stator and rotor by means of a rectifier includes: The attenuation of the flux excitation in the air gap is reduced by the rectifier to reduce the torque ripple during motor operation.

4. The method of claim 1, wherein the resistance in flux decay is asymmetric due to the inclusion of a rectifier, and Wherein a first change in flux is resisted by inducing a first current in the rotor winding in a first direction until the first current decreases to zero, and a second change in flux is enabled to induce a second current in the rotor winding in a second direction.

5. The method according to claim 1, further comprising: Adjustments to at least one of the current angle or the current magnitude are selected to control rotor torque ripple while achieving a target operating output of the electric machine.

6. The method according to claim 1, further comprising: sending a stator current through the stator at a current angle, The current angle is measured in the direction of movement in front of the rotor pole or relative to the nearest one of the rotor poles.

7. The method according to claim 1, further comprising: Based on a target operating output of the electric machine, a current angle of the stator current relative to the rotor poles is adjusted in response to a change in one or more operating conditions.

8. The method according to claim 7, wherein: Adjusting the current angle includes adjusting the current angle on only one axis of the motor, and The one axis includes one of the D axis or the Q axis of the motor.

9. The method according to claim 8, further comprising: determining a target rotor motion corresponding to a target operating output of the motor; When the rotor performs the target rotor motion, modulating the current on the D-axis to control the rotor torque ripple; and Achieve the target operating output of the motor.

10. The method according to claim 1, further comprising: In response to changes in one or more operating conditions based on a target operating output of the electric machine, a current magnitude of the stator current is adjusted independently of a current angle of the stator current.

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