Method and system for detecting winding resistance and winding temperature of an alternating current motor

Abstract

A method includes determining a vector state of an alternating current (AC) machine. The method includes obtaining a plurality of phase current samples of the AC machine when the vector state is a zero vector state, determining a decay time constant based on the plurality of phase current samples, and determining a resistance of a winding of the AC machine based on the decay time constant.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 140,579, filed January 22, 2021, the disclosure of which is incorporated herein by reference as if fully set forth herein. Technical Field

[0003] The present disclosure relates to systems and methods for detecting winding resistance and winding temperature of an alternating current (AC) motor. Background Art

[0004] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0005] AC motors provide power to various components and systems, such as hybrid electric vehicles (HEVs) and electric vehicles (EVs). A controller communicatively coupled to the AC motor can acquire performance data from one or more sensors of the AC motor to evaluate various performance characteristics of the AC motor. As an example, the controller can inject current into various phases of the AC motor, acquire temperature data from temperature sensors, and determine the temperature and / or resistance of a winding of a permanent magnet synchronous motor (PMSM) based on the temperature data. Furthermore, the controller can execute a field-oriented control routine based on the determined resistance and / or temperature of the winding.

[0006] However, temperature sensors may increase the size of the AC motor and the complexity of the controller logic required to process the sensor data. Summary of the Invention

[0007] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0008] The present disclosure provides a method including determining a vector state of an alternating current (AC) motor. The method includes obtaining a plurality of phase current samples of the AC motor when the vector state is a zero vector state; determining a decay time constant based on the plurality of phase current samples; and determining a resistance of a winding of the AC motor based on the decay time constant.

[0009] In some forms, the vector state is determined based on a plurality of switches of the inverter.

[0010] In some forms, the vector state is a zero vector state when each of the plurality of switches and the power source collectively form a short circuit.

[0011] In some forms, the vector state is a zero vector state when the AC machine is operating in a steady-state stall condition.

[0012] In some forms, the method further includes controlling the AC electric machine based on a space vector pulse width modulation routine.

[0013] In some forms, the decay time constant is determined based on a first current magnitude of a first phase current sample of the plurality of phase current samples and a second current magnitude of a second phase current sample of the plurality of phase current samples.

[0014] In some forms, the decay time constant is determined based on a difference between a first natural logarithm of the first current magnitude and a second natural logarithm of the second current magnitude.

[0015] In some forms, the decay time constant is determined based on a first time stamp of a first phase current sample of the plurality of phase current samples and a second time stamp of a second phase current sample of the plurality of phase current samples.

[0016] In some forms, the decay time constant is determined based on a difference between the first time stamp and the second time stamp.

[0017] In some forms, the resistance is determined based on a baseline inductance of the winding.

[0018] In some forms, the method further includes determining a temperature of the winding based on the resistance.

[0019] In some forms, the temperature is determined based on a baseline resistance of the winding and a temperature coefficient of the resistance of the winding.

[0020] The present disclosure provides a system comprising: a processor; and a non-transitory computer-readable medium comprising instructions executable by the processor. The instructions comprise determining a vector state of an alternating current (AC) electric machine. The instructions comprise, when the vector state is a zero vector state, obtaining a plurality of phase current samples of the AC electric machine; determining a decay time constant based on the plurality of phase current samples; and determining a resistance of a winding of the AC electric machine based on the decay time constant.

[0021] In some forms, the vector state is determined based on a plurality of switches of an inverter communicably coupled to the processor.

[0022] In some forms, the vector state is the zero vector state when each of the plurality of switches and a power source collectively form a short circuit.

[0023] In some forms, the vector state is the zero vector state when the AC electric machine is operating in a steady state stall condition.

[0024] In some forms, the decay time constant is determined based on a first current magnitude of a first phase current sample of the plurality of phase current samples and a second current magnitude of a second phase current sample of the plurality of phase current samples.

[0025] In some forms, the decay time constant is determined based on a first time stamp of the first phase current sample and a second time stamp of the second phase current sample.

[0026] In some forms, the decay time constant is determined based on a difference between a first natural logarithm of the first current magnitude and a second natural logarithm of the second current magnitude and a difference between the first time stamp and the second time stamp.

[0027] The present disclosure provides a method comprising determining a vector state of an alternating current (AC) electric machine, wherein the vector state is one of a zero vector state and a non-zero vector state. The method comprises, when the vector state is in the non-zero vector state: obtaining a plurality of phase current samples of the AC electric machine; determining a rise time constant based on the plurality of phase current samples; and determining a resistance of a winding of the AC electric machine based on the rise time constant.

[0028] Further areas of application will become apparent from the description provided herein. It should be understood that the description and specific examples, while indicating embodiments of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0029] For a better understanding of the present disclosure, various forms thereof will now be described, by way of example with reference to the drawings, in which:

[0030] FIG. 1A is a block diagram of an example vehicle in accordance with the teachings of the present disclosure;

[0031] FIG. 1B is a block diagram of an inverter in accordance with the teachings of the present disclosure;

[0032] FIG. 2A is a block diagram of a system for determining winding resistance and winding temperature in accordance with the teachings of the present disclosure;

[0033] FIG. 2B is a vector state diagram of a space vector pulse width modulation control routine in accordance with the teachings of the present disclosure;

[0034] FIG. 3A is a flowchart for determining rotor speed and rotor position in accordance with the teachings of the present disclosure;

[0035] FIG. 3B is a diagram of a space vector pulse width modulation control routine in accordance with the teachings of the present disclosure; and

[0036] FIG. 3C is a diagram of winding current during a space vector pulse width modulation control routine in accordance with the teachings of the present disclosure.

[0037] The drawings described herein are for purposes of illustration only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0038] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0039] The present disclosure provides a system for determining the resistance and / or temperature of one or more windings of an AC electric machine based on one or more instantaneous current measurements taken during a zero vector state of a space vector pulse width modulation routine. As described in further detail herein, the one or more instantaneous current measurements taken during the zero vector state enable the controller to determine or estimate the resistance and / or temperature of the one or more windings without the use of additional temperature / resistance sensors, thereby reducing the size of the AC electric machine and the complexity of the controller logic required to process the sensor data.

[0040] Reference FIG. 1A A vehicle 5 is shown. The vehicle 5 includes an AC electric machine 10, a power source 20, an inverter 30, a phase current sensor 40, a rotor sensor 50, and a controller 60. It should be understood that the vehicle 5 includes various other components and is not limited to the components described herein.

[0041] In one form, the AC electric machine 10 is a three-phase electric motor configured to generate torque required to drive a load, such as a ball ramp clutch assembly. Example AC electric machines 10 include, but are not limited to, synchronous electric machines (e.g., PMSMs), asynchronous electric machines, salient pole electric machines, non-salient pole electric machines, etc. It should be understood that the AC electric machine 10 can be various types of AC electric machines and is not limited to the examples described herein. In one form, the AC electric machine 10 can include windings 12 (e.g., three sets of windings corresponding to the three phases of the AC electric machine 10) and a rotor 14. While the AC electric machine 10 is illustrated as including the windings 12 and the rotor 14, it should be understood that the AC electric machine 10 can include various other components not illustrated herein. In one variation, the AC electric machine 10 can be replaced with a direct current (DC) electric machine configured to generate torque required to drive a load.

[0042] In one form, the power source 20 is configured to provide power to various components of the vehicle 5, such as the inverter 30 and the controller 60. As an example, the power source 20 includes a direct current (DC) power source (e.g., one or more batteries) configured to provide direct current power. As another example, the power source 20 includes an AC power source and a rectifier circuit configured to provide DC power.

[0043] In one form, the inverter 30 includes one or more circuits configured to convert power from the power source 20 into a three-phase AC electrical signal and provide the three-phase AC electrical signal to the AC electric machine 10. As an example and as shown in FIG. 1, the inverter 30 includes a bridge circuit 32 (e.g., a full-bridge circuit) configured to convert DC power from the power source 20 into a three-phase AC electrical signal and provide the three-phase AC electrical signal to the AC electric machine 10. FIG. 1BAs shown in FIG. 1, inverter 30 can be a three-phase voltage source inverter circuit including six switches 32-1, 32-2, 32-3, 32-4, 32-5, 32-6 (collectively referred to as switches 32) and three legs 34-1, 34-2, 34-3 (collectively referred to as legs 34). Example switches 32 include, but are not limited to, bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), and the like. In one form, each of legs 34 is electrically coupled to one of windings 12 of AC machine 10. It should be understood that inverter 30 can include various discrete and / or integrated circuits that output a three-phase AC electrical signal, and is not limited to the examples described herein. It should also be understood that inverter 30 can be implemented by various other inverters of other forms, including but not limited to two-level voltage source inverters, multi-level inverters, and the like.

[0044] In one form and with reference back to FIG. 1, FIG. 1A Phase current sensors 40 are configured to generate information representative of current magnitudes of AC electrical signals provided by inverter 30 to windings 12 of AC machine 10. As an example, phase current sensors 40 can be Hall effect sensors, transformers, current clamp meters, fiber optic current sensors, and the like. In some forms, the number of phase current sensors 40 can be equal to the number of phases of AC machine 10. Rotor sensor 50 is configured to generate information representative of a speed and / or angular position of rotor 14. As an example, rotor sensor 50 can be an encoder, an electromagnetic resolver, and the like.

[0045] In one form, controller 60 can include various hardware components such as transceivers, routers, input / output ports, and the like to perform the functions described herein. Further, controller 60 can include a field oriented control (FOC) module 62, a characterization module 64, and a space vector pulse width modulation (SVPWM) control module 66 implemented by one or more processors configured to execute instructions stored in a non-transitory computer readable medium such as random access memory (RAM) and / or read only memory (ROM).

[0046] In one form, FOC module 62 is configured to determine stationary reference frame voltage magnitudes based on currents obtained from phase current sensors 40. SVPWM control module 66 is configured to control switches 32, and thereby operation of AC machine 10, based on the stationary reference frame voltage magnitudes determined by FOC module 62. Characterization module 64 is configured to selectively obtain current data from phase current sensors 40 based on states of switches 32, and determine resistances and / or temperatures of windings 12 based on the sensor data. Additional details of the functions of FOC module 62, characterization module 64, and SVPWM control module 66 will be described below with reference to FIGS. 2-4. FIG. 2A-2BThe description is made.

[0047] Referring FIG. 2A , an example functional block diagram of the FOC module 62, the characteristic module 64, and the SVPWM control module 66 is shown. In one form, the FOC module 62 includes a phase current determination module (PCDM) 70, a stationary reference frame generation module (SRFGM) 80, a rotating reference frame generation module (RRFGM) 90, a rotating reference frame voltage module (RRFVM) 100, and a stationary reference frame voltage module (SRFVM) 110.

[0048] In some forms, the PCDM 70 determines the magnitude of the phase current for each winding 12 (I A , I B , I C ) based on sensor data acquired from the phase current sensors 40.

[0049] In one form, the SRFGM 80 converts the phase current for each winding 12 (I A , I B , I C ) into a two-axis stationary reference frame representation of the phase current, such as a stationary axis orthogonal axis coordinate system (i.e., an αβ coordinate system). As an example, the SRFGM 80 can convert the phase current (I A , I B , I C ) into an αβ coordinate system (I α , I β ) by performing a Clarke transformation, as indicated by the following relationship:

[0050]

[0051]

[0052] In one form, the RRFGM 90 converts the αβ coordinate system representation of the phase current (I α , I β ) into a two-axis rotating reference frame representation of the phase current, such as a direct orthogonal zero coordinate system (i.e., a dq coordinate system). As an example, the RRFGM 90 converts the αβ coordinate system representation of the phase current (I α , I β ) into a dq coordinate system (I q , I d ) by performing a Park transformation, as indicated by the following relationship:

[0053] I d = I α cos θ + I I sin θ (3)

[0054] I q =-I α sinθ+I β cosθ (4)

[0055] In the relationships (3) and (4), I d is the d-axis phase current, I q is the q-axis phase current, and θ is a rotation angle by which the dq coordinate system is rotated from the αβ coordinate system and is based on an angular position acquired from the rotor sensor 50.

[0056] In one form, the RRFVM 100 determines dq coordinate system representations of phase voltages (V q , V d ) based on dq coordinate system phase currents (I q , I d ) and reference dq coordinate system phase currents (I q *, I d ). In one form, the RRFVM 100 can be implemented by a proportional-integral (PI) controller. The RRFVM 100 can determine the reference dq coordinate system phase currents (I q *, I d ) based on a difference between a speed of the rotor 14 (indicated by the rotor sensor 50) and a torque of the rotor 14 (indicated by the phase current sensor 40) and a torque command. It should be understood that the reference dq coordinate system phase currents (I q *, I d ) can be determined in other forms based on current fluxes of the windings 12. Thus, the RRFVM 100 can determine the dq coordinate system phase voltages (V q , V d ) based on a difference between the dq coordinate system phase currents (I q , I d ) and the reference dq coordinate system phase currents (I q *, I d ), proportional, integral constants, and an integration routine performed by the PI controller.

[0057] In one form, the SRFVM 110 converts the dq coordinate system representations of phase voltages (V q , V d ) into αβ coordinate system representations of phase voltages (V α , V β ). As an example, the SRFVM 110 performs an inverse Park transformation to obtain the αβ coordinate system of phase voltages (V α , V β ) as shown in the following relationships:

[0058] V α = Vd cos θ - V q sin θ (5)

[0059] V β = V d sin θ + V q cos θ (6)

[0060] In the relationships (5) and (6), θ is a rotation angle by which the dq coordinate system is rotated from the αβ coordinate system, and is based on an angular position acquired from the rotor sensor 50.

[0061] The SVPWM control module 66 is configured to selectively control the voltage magnitude and / or frequency of the three-phase AC electrical signals provided to the AC motor 10 based on an αβ coordinate system representation of the phase voltages (V α , V β , hereinafter referred to as "reference signals"). To control the voltage magnitude and / or frequency of the signals provided to the AC motor 10, the SVPWM control module 66 selectively activates the switches 32 of the inverter 30 based on the reference signals and a vector state diagram. To selectively activate the switches 32, the SVPWM control module 66 is configured to selectively provide a bias voltage to the switches 32, and thereby turn on or turn off the switches 32.

[0062] As an example and with reference to FIG. 2B , a vector state diagram 200 is shown having vector states (V0-V7) and reference signals 202. The vector states (V0-V7) correspond to states of the switches 32 of the inverter 30, and can be one of a zero vector state or a non-zero vector state (first vector state, second vector state,..., and sixth vector state). As an example and with reference to FIG. 1B and FIG. 2B , a zero vector state (V0) corresponds to switches 32-4, 32-5, 32-6 being turned on and switches 32-1, 32-2, 32-3 being turned off (i.e., winding 12 is shorted, the AC motor 10 is operating in steady state stall, etc.). Another zero vector state (V7) corresponds to switches 32-1, 32-2, 32-3 being turned on and switches 32-4, 32-5, 32-6 being turned off.

[0063] As another example, the first vector state (VI) can correspond to switches 32-1, 32-5, 32-6 being on and switches 32-2, 32-3, 32-4 being off. The second vector state (V2) can correspond to switches 32-1, 32-2, 32-6 being on and switches 32-3, 32-4, 32-5 being off. The third vector state (V3) can correspond to switches 32-2, 32-4, 32-6 being on and switches 32-1, 32-3, 32-5 being off. The fourth vector state (V4) can correspond to switches 32-2, 32-3, 32-4 being on and switches 32-1, 32-5, 32-6 being off. The fifth vector state (V5) can correspond to switches 32-3, 32-4, 32-5 being on and switches 32-1, 32-2, 32-6 being off. The sixth vector state (V6) can correspond to switches 32-1, 32-3, 32-5 being on and switches 32-2, 32-4, 32-6 being off. It should be understood that the non-zero vector states can have different combinations of switch states and are not limited to the examples described herein.

[0064] The SVPWM control module 66 is configured to selectively activate the switches 32 based on the location of the reference signal 202 on the vector state diagram 200. As an example, if the reference signal 202 is located between the first vector state (VI) and the third vector state (V3), the SVPWM control module 66 activates the switches 32 according to the first vector state (VI) for a first time period and according to the third vector state (V3) for a second time period. Thus, a resulting vector based on the first time period and the second time period under the first vector state (VI) and the third vector state (V3), respectively, equals the reference signal 202.

[0065] Returning to FIG. 2A The characteristic module 64 can include a zero vector state detection module (ZVSDM) 120, a current decay sampling module (CDSM) 130, a decay time constant module (DTCM) 140, and a resistance / temperature module (RTM) 150.

[0066] The ZVSDM 120 is configured to detect the vector state of the switches 32 indicated by the SVPWM control module 66. As an example, the ZVSDM 120 is configured to determine whether the switches 32 are in a zero vector state or one of the non-zero vector states.

[0067] In response to the ZVSDM 120 determining that the switch 32 is in the zero- vector state, the CDSM 130 obtains a plurality of instantaneous phase current samples of the winding 12 as the current decays during the steady-state stall operation of the AC machine 10. In one form, each of the windings 12 can be represented as a resistor-inductor (RL) circuit during the steady-state stall operation of the AC machine 10. Accordingly, the instantaneous phase current samples can be determined based on the following relationships:

[0068]

[0069]

[0070]

[0071] In the relationships (7), (8), and (9), i1(t) is the magnitude of the first instantaneous phase current sample, i2(t) is the magnitude of the second instantaneous phase current sample, t1 is the timestamp of the first instantaneous phase current sample, t2 is the timestamp of the second instantaneous phase current sample, R S is the resistance of the winding 12, L S is the inductance of the winding 12, I0 is the steady-state current based on the resistance (R S ) of the winding and the voltage of the winding 12, and τ is the decay time constant of the winding 12.

[0072] In one form, the DTCM 140 is configured to determine the decay time constant of the winding 12. The DTCM 140 can determine the decay time constant based on the natural logarithm of the magnitudes of the first and second instantaneous phase current samples and the difference between the timestamps of the first and second instantaneous phase current samples. More specifically, the DTCM 140 can divide the magnitude of the first instantaneous phase current sample by the magnitude of the second instantaneous phase current sample to determine the decay time constant (τ), as shown in the following relationship:

[0073]

[0074] In one form, the RTM 150 is configured to determine the resistance of the winding 12 based on the decay time constant. Since the inductance (L S ) of the winding 12 does not vary with temperature, the resistance (R S ) of the winding 12 can be determined based on a baseline inductance (L0) of the winding 12 at a predefined temperature (e.g., room temperature), as shown in the following relationship:

[0075]

[0076] In one form, the RTM 150 is further configured to determine the resistance (R Sto determine the temperature of winding 12. RTM 150 can use a known resistance-temperature conversion relationship to determine the temperature of winding 12 (T) as shown in the following relationship:

[0077] R s = R0[1 + C(T - T0)] (12)

[0078] In relationship (12), R0is the resistance of winding 12 (R S ) at a predefined temperature (e.g., room temperature), C is the temperature coefficient of resistance of winding 12, and T0is the temperature of winding 12 (R S ) at a predefined temperature (e.g., room temperature).

[0079] Although FIG. 2A-2B disclosed that controller 60 is configured to determine the resistance and / or temperature of winding 12 during zero vector states, it should be appreciated that in other variations, controller 60 can also determine the resistance and / or temperature of winding 12 during non-zero vector states. As an example, in one form, in response to ZVSDM 120 determining that switches 32 are in a non-zero vector state, CDSM 130 acquires a plurality of instantaneous phase current samples of winding 12 using relationships (7), (8), and (9) as the current rises. Subsequently, DTCM 140 can determine the rise time constant of winding 12 using relationship (10), and RTM 150 can determine the resistance and / or temperature of winding 12 based on the rise time constant using relationships (11) and / or (12) as the current rises.

[0080] Furthermore, although FIG. 2A-2B disclosed that controller 60 controls the voltage magnitude and / or frequency of the three-phase AC electrical signal provided using SVPWM control module 66, it should be appreciated that other control routines can be performed in other variations. As an example, SVPWM control module 66 of controller 60 can be replaced with other modules configured to perform other field-oriented control routines, block commutation routines, sinusoidal commutation routines, trapezoidal commutation routines, etc. to selectively control the voltage magnitude and / or frequency of the signal provided to AC motor 10. Thus, for other control routines of AC motor 10, ZVSDM 120 of controller 60 can determine whether switches 32 are in a zero vector state (i.e., when switches 32-4, 32-5, 32-6 are on and switches 32-1, 32-2, 32-3 are off, or when switches 32-1, 32-2, 32-3 are on and switches 32-4, 32-5, 32-6 are off) and determine whether in a non-zero vector state in a similar manner.

[0081] With reference to FIG. 3AThe routine 300 for determining the resistance of the winding 12 is shown and executed by the controller 60. At 304, the controller 60 determines the vector state of the SVPWM routine. At 308, the controller 60 determines whether the SVPWM routine is in a zero vector state. As an example and as described above, the SVPWM routine is in a zero vector state if the switches 32-1, 32-2, 32-3 (or the switches 32-4, 32-5, 32-6) are either collectively activated (e.g., time period (1, 1, 1) of the SVPWM curve 350 shown in FIG. 3B) or collectively deactivated (e.g., time period (0, 0, 0) of the SVPWM curve 350). If the SVPWM routine is in a zero vector state, the routine 300 proceeds to 312. Otherwise, if the SVPWM routine is not in a zero vector state, the routine 300 proceeds to 304. FIG. 3B At 312, the controller 60 acquires a plurality of instantaneous phase current decay samples (e.g., the instantaneous phase current decay samples 362 and 364, the instantaneous phase current decay samples 372, 374, and / or the instantaneous phase current decay samples 382, 384 of the current plot 360 shown in FIG. 3B). At 316, the controller 60 determines a decay time constant of the winding 12 based on the plurality of instantaneous phase current decay samples. At 320, the controller 60 determines a resistance and / or a temperature of the winding 12 based on the decay time constant.

[0082] At 312, the controller 60 acquires a plurality of instantaneous phase current decay samples (e.g., the instantaneous phase current decay samples 362 and 364, the instantaneous phase current decay samples 372, 374, and / or the instantaneous phase current decay samples 382, 384 of the current plot 360 shown in FIG. 3B). At 316, the controller 60 determines a decay time constant of the winding 12 based on the plurality of instantaneous phase current decay samples. At 320, the controller 60 determines a resistance and / or a temperature of the winding 12 based on the decay time constant. FIG. 3C

[0083] It should be appreciated that in other variations, a routine similar to the routine 300 can be executed to determine the resistance of the winding 12 during a non-zero vector state. As an example, if the SVPWM routine (or other control routine of the AC machine 10) is not in a zero vector state, the controller 60 can acquire a plurality of instantaneous phase current rise samples (e.g., the instantaneous phase current samples in one of the time periods (1, 0, 0) and (1, 1, 0) shown in FIG. 3B). Subsequently, the controller 60 can determine a rise time constant of the winding 12 based on the plurality of instantaneous phase current rise samples and determine a resistance and / or a temperature of the winding 12 based on the rise time constant. FIG. 3C

[0084] Unless specifically stated otherwise, all measurements, values, ratings, positions, materials, acts, or the like, involve a tolerance, and are not limited to the precise numeric value, in describing the bounds of the application, the word "approximately" or "about" can have the same meaning. Such modifications are intended to include, where appropriate, permutations of elements: adding elements dissipating previously used elements; substituting new elements for old; eliminating elements; and / or the like.

[0085] ​​As used herein, the phrase at least one of A, B, and C should be interpreted as meaning using the logic of non-exclusive logical OR (A or B or C), and should not be interpreted as meaning "at least one of A, at least one of B, and at least one of C."

[0086] The description of the present disclosure is merely exemplary in nature and, thus, variations that do not depart from the essence of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

[0087] In the drawings, the arrow direction indicated by an arrowhead generally denotes the information flow (such as data or instructions) of interest to the illustration. For example, when elements A and B exchange a variety of information, but the information transmitted from element A to element B is relevant to the illustration, an arrow can be directed from element A to element B. This one-way arrow does not mean that no other information is transmitted from element B to element A. Further, for the information transmitted from element A to element B, element B can send a request for the information to element A or receive an acknowledgement of the information.

[0088] In this application, the terms "module" and / or "controller" can refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0089] The term memory is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not include transitory propagating signals or electromagnetic waves through a medium, such as on a carrier wave; thus, the term computer-readable medium can be considered tangible and non-transitory. Non-limiting examples of non-transitory, tangible computer-readable media are nonvolatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only circuits), volatile memory circuits (such as fixed random-access memory circuits or dynamic random-access memory circuits), magnetic storage media (such as analog or digital magnetic tape or a hard disk drive), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0090] The apparatus and methods described in this application can be implemented in part or in whole through special purpose computers, which are created by configuring general purpose computers to create one or more specific functions, as described above. The functions described above can be implemented in software that is executable on a general purpose computer, a special purpose computer, or a computer created by configuring a general purpose computer through use of a computer program.

Claims

1. A method comprising: determining a vector state (V) of an alternating current (AC) machine (10); and when the vector state (V) is a zero vector state: obtaining a plurality of phase current samples (i) of the AC machine; determining a decay time constant (τ) based on the plurality of phase current samples (i); and determining a resistance (R) of a winding (12) of the AC machine (10) based on the decay time constant (τ) S ), wherein the decay time constant (τ) is determined based on a first current magnitude of a first phase current sample of the plurality of phase current samples and a second current magnitude of a second phase current sample of the plurality of phase current samples (i), and the decay time constant (τ) is determined based on a difference between a first natural logarithm of the first current magnitude and a second natural logarithm of the second current magnitude.

2. The method of claim 1, wherein, the vector state (V) is determined based on a plurality of switches (32) of an inverter (30).

3. The method according to claim 2, wherein, the vector state (V) is the zero vector state when each of the plurality of switches (32) and a power source (20) collectively form a short circuit.

4. The method of claim 2, wherein, the vector state (V) is the zero vector state when the AC machine (10) is operating under a steady state stall condition.

5. The method of claim 1, further comprising controlling the AC machine (10) based on a space vector pulse width modulation routine.

6. The method of claim 1, wherein, the decay time constant (τ) is determined based on a first time stamp of a first phase current sample of the plurality of phase current samples and a second time stamp of a second phase current sample of the plurality of phase current samples (i).

7. The method of claim 6, wherein, the decay time constant (τ) is determined based on a difference between the first time stamp and the second time stamp.

8. The method of claim 1, wherein, The resistance (R S ) is determined based on a baseline inductance of the winding (12).

9. The method of claim 1, further comprising determining a temperature of the winding (12) based on the resistance (R S ).

10. The method of claim 9, wherein, the temperature is determined based on a baseline resistance of the winding (12) and a temperature coefficient of resistance of the winding (12).

11. A system comprising: a processor; and a non-transitory computer readable medium comprising instructions executable by the processor, wherein the instructions comprise: determining a vector state of an alternating current (AC) machine; and when the vector state is a zero vector state: obtaining a plurality of phase current samples of the AC machine; determining a decay time constant based on the plurality of phase current samples; and determining a resistance of a winding of the AC machine based on the decay time constant, wherein the decay time constant is determined based on a first current magnitude of a first phase current sample of the plurality of phase current samples and a second current magnitude of a second phase current sample of the plurality of phase current samples, and the decay time constant is determined based on a difference between a first natural logarithm of the first current magnitude and a second natural logarithm of the second current magnitude. the vector state is determined based on a plurality of switches of an inverter communicably coupled to the processor.

12. The system of claim 11, wherein, the vector state is the zero vector state when each of the plurality of switches and a power source collectively form a short circuit.

13. The system of claim 12, wherein, the vector state is the zero vector state when the AC machine is operating under a steady state stall condition.

14. The system of claim 12, wherein, the decay time constant is determined based on a first time stamp of the first phase current sample and a second time stamp of the second phase current sample.

15. The system of claim 11, wherein, the decay time constant is determined based on a difference between the first time stamp and the second time stamp.

16. The system of claim 15, wherein, ​ 17. A method comprising: determining a vector state of an alternating current (AC) motor, wherein the vector state is one of a zero vector state and a non-zero vector state; and when the vector state is in the non-zero vector state: obtaining a plurality of phase current samples of the AC motor; determining a rise time constant based on the plurality of phase current samples; and determining a resistance of a winding of the AC motor based on the rise time constant determined by a decay time constant module, wherein the decay time constant module is configured to determine a decay time constant (τ) based on a first timestamp of a first phase current sample of the plurality of phase current samples and a second timestamp of a second phase current sample of the plurality of phase current samples (i), and further based on a difference between the first timestamp and the second timestamp.

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