US20170126166A1 - Determination of stator winding resistance in an electric machine - Google Patents
Determination of stator winding resistance in an electric machine Download PDFInfo
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- US20170126166A1 US20170126166A1 US14/932,613 US201514932613A US2017126166A1 US 20170126166 A1 US20170126166 A1 US 20170126166A1 US 201514932613 A US201514932613 A US 201514932613A US 2017126166 A1 US2017126166 A1 US 2017126166A1
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- 238000004804 winding Methods 0.000 title claims abstract description 70
- 238000000034 method Methods 0.000 claims abstract description 43
- 230000006870 function Effects 0.000 claims description 43
- 230000004907 flux Effects 0.000 claims description 35
- 238000004891 communication Methods 0.000 description 6
- 239000011162 core material Substances 0.000 description 5
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- 238000012360 testing method Methods 0.000 description 2
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- 230000005355 Hall effect Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
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- 230000002085 persistent effect Effects 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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- H02P29/0055—
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/34—Testing dynamo-electric machines
- G01R31/343—Testing dynamo-electric machines in operation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
- H02P21/143—Inertia or moment of inertia estimation
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- H02P21/148—
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
- H02P23/14—Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/60—Controlling or determining the temperature of the motor or of the drive
- H02P29/64—Controlling or determining the temperature of the winding
Definitions
- the disclosure relates generally to the determination of stator winding resistance in an electric machine assembly.
- An electric machine such as an interior permanent magnet machine generally includes a rotor having a plurality of magnets of alternating polarity.
- the rotor is rotatable within a stator which generally includes multiple stator windings and magnetic poles of alternating polarity.
- An electric machine such as a motor, takes in electrical energy in terms of a potential difference and a current flow, converting it to mechanical work. Because electric machines are not 100% efficient, some of the electric energy is lost to heat, due to electrical resistance of the windings.
- the electrical resistance of the stator windings at high rotor speeds varies considerably with operating temperature and current.
- An electric machine assembly has an electric machine having a stator and a rotor.
- the stator has stator windings at a stator winding temperature (t S ) and the rotor is configured to rotate at a rotor speed ( ⁇ ).
- a controller is operatively connected to the electric machine and configured to receive a torque command (T*).
- the controller has a processor and tangible, non-transitory memory on which is recorded instructions for executing a method for determining stator winding resistance. Execution of the instructions by the processor causes the controller to determine a high-speed resistance factor (r H ) for the stator windings.
- the high-speed resistance factor (r H ) is based at least partially on the torque command (T*), the stator winding temperature (t S ), the rotor speed ( ⁇ ), a characterized torque error and the number of pole pairs (P) of the electric machine.
- the controller may be operative to control at least one operating parameter of the electric machine based at least partially on the total resistance (R) for the stator windings to achieve improved performance and/or efficiency.
- a first temperature sensor may be operatively connected to the controller and configured to measure the stator winding temperature (t S ).
- a second temperature sensor may be operatively connected to the controller and configured to measure a rotor temperature.
- a magnetic flux sensor may be operatively connected to the controller and configured to measure a magnetic flux of the electric machine.
- R total resistance
- the high-speed resistance factor (r H ) accounts for variation in stator resistance when the rotor speed ( ⁇ ) is relatively high.
- the low-speed resistance factor (r L ) accounts for variation in stator resistance when the rotor speed ( ⁇ ) is relatively low.
- the weighting factor (k) may be one when the rotor speed ( ⁇ ) is at or above a predefined high speed threshold (e.g. ⁇ 5000 rpm).
- the weighting factor (k) may be zero when the rotor speed ( ⁇ ) is at or below a predefined low speed threshold (e.g. ⁇ 3000 rpm).
- Determining the high-speed resistance factor (r H ) includes: obtaining a first function (F 1 ), via the controller, as a product of a look-up factor and the torque command (T*), wherein the look-up factor is based at least partially on the rotor speed, the stator winding temperature (t S ) and a characterized torque error.
- the characterized torque error may be defined as the difference between any two independent or different estimates of torque produced by the machine.
- FIG. 1 is a schematic fragmentary partly sectional view of an electric machine assembly with a stator having a stator windings
- FIG. 2 is a flowchart for a method for determining the high-speed resistance factor (r H ), the low-speed resistance factor (r L ) and total resistance (R) for the stator windings of FIG. 1 ;
- FIG. 3 is an example diagram for obtaining a look-up factor used in the method of FIG. 2 ;
- FIG. 4 is an example torque versus machine speed diagram for the assembly of FIG. 1 .
- FIG. 1 schematically illustrates an electric machine assembly 10 .
- the assembly 10 includes an electric machine 12 .
- the assembly 10 may be a component of a device 11 .
- the device 11 may be a passenger vehicle, performance vehicle, military vehicle, industrial vehicle, robot, farm implement, sports-related equipment or any other type of apparatus.
- the electric machine 12 includes a stator 14 and a rotor 16 .
- the rotor 16 may include a first permanent magnet 18 and a second permanent magnet 20 of alternating polarity around the outer periphery of a rotor core 22 .
- the rotor 16 may include any number of permanent magnets; for simplicity only two are shown.
- the rotor 16 is rotatable at a rotor speed ( ⁇ ) within the stator 14 . While the embodiment shown in FIG. 1 illustrates a three-phase, single pole-pair (i.e. two pole) machine, it is understood that any number of phases or pole pairs may be employed.
- the stator 14 includes a stator core 24 which may be cylindrically shaped with a hollow interior.
- the stator core 24 may include a plurality of inwardly-protruding stator teeth 26 A-F, separated by gaps or slots 28 .
- stator windings 30 may be operatively connected to the stator core 24 , such as for example, being coiled around the stator teeth 26 A-F.
- the electric machine 12 may take many different forms and include multiple and/or alternate components and facilities. While an example electric machine 12 is shown in the Figures, the components illustrated in the Figures are not intended to be limiting. Indeed, additional or alternative components and/or implementations may be used.
- the stator windings 30 may include six sets of windings; one set for each of three phases (the first phase through stator windings 30 A and 30 D, the second phase through stator windings 30 B and 30 E and the third phase through stator windings 30 C and 30 F). Alternatively, slip rings or brushes (not shown) may be employed. Referring to FIG. 1 , a quadrature (q) magnetic axis 32 and a direct (d) magnetic axis 34 are shown. The first and second permanent magnets 18 , 20 create a magnetic field and magnetic flux. The magnetic flux of the first and second permanent magnet fluxes 18 , 20 are aligned when the rotor angle 36 is zero. As previously noted, the electric machine 12 may be of any type, including, but not limited to, induction and synchronous machines.
- the assembly 10 includes a controller 40 operatively connected to or in electronic communication with the electric machine 12 .
- the controller 40 is configured to receive a torque command (T*).
- the controller 40 includes at least one processor 42 and at least one memory 44 (or any non-transitory, tangible computer readable storage medium) on which are recorded instructions for executing method 100 , shown in FIG. 2 , for determining electrical resistance of the stator windings 30 , including a high-speed resistance factor (r H ), a low-speed resistance factor (r L ) and a total resistance (R).
- the memory 44 can store controller-executable instruction sets, and the processor 42 can execute the controller-executable instruction sets stored in the memory 44 .
- the method 100 and assembly 10 described herein minimizes the use of extensive look-up tables and complex curve-fitting for estimating the variation in stator resistance at various rotor speeds.
- the controller 40 of FIG. 1 is specifically programmed to execute the steps of the method 100 (as discussed in detail below with respect to FIG. 2 ) and can receive inputs from various sensors.
- the assembly 10 may include a first temperature sensor 46 (such as a thermistor or thermocouple) in communication (e.g., electronic communication) the controller 40 , as shown in FIG. 1 .
- the first temperature sensor 46 is capable of measuring the temperature of the stator windings 30 A-F and sending input signals to the controller 40 .
- the first temperature sensor 46 may be installed or mounted on one of the stator windings 30 A-F.
- a second temperature sensor 48 may be in communication with the controller 40 and configured to measure the temperature of the rotor 16 , referred to herein as the “rotor temperature.”
- the assembly 10 may include a magnetic flux sensor 50 in communication (e.g., electronic communication) with the controller 40 .
- the magnetic flux sensor 50 is capable of measuring the magnetic flux emanating from the electric machine 12 , such as flux lines from permanent magnets 18 , 20 in the rotor 16 , and sending input signals to the controller 40 .
- the magnetic flux sensor 50 is a Hall-effect sensor, however, any type of magnetic flux sensing device known to those skilled in the art may be employed.
- controller 40 may be programmed to determine the magnetic flux based on other methods, without employing any sensors, such as finite element analysis (FEA) or any method or mechanism known to those skilled in the art.
- a battery pack 56 may be operatively connected to the machine 12 as a source of DC voltage.
- Step 100 a flowchart of the method 100 stored on and executable by the controller 40 of FIG. 1 is shown.
- Method 100 need not be applied in the specific order recited herein. Furthermore, it is to be understood that some steps may be eliminated.
- the method 100 utilizes estimated magnetic flux (from a magnetic flux sensor 50 or FEA model) and two independent motor torque estimations, such as using current-based (flux map) and active power-based estimates.
- method 100 may begin with step 102 , where the controller 40 is programmed or configured to obtain the high-speed resistance factor (r H ).
- Step 102 includes sub-steps 102 A through F.
- step 102 A of FIG. 2 the controller 40 is programmed or configured to obtain a first function (F 1 ) as a product of a look-up factor and the torque command (T*).
- the torque command (T*) may be received by the controller 40 in response to an operator input or an automatically-fed input condition monitored by the controller 40 . If the device 11 is a vehicle, the controller 40 may determine the torque command (T*) based on input signals from an operator through an accelerator pedal 52 and brake pedal 54 , shown in FIG. 1 .
- characterization data is taken at various rotor speeds ( ⁇ ) at a baseline temperature (C).
- the baseline temperature (C) may be varied based on the particular application. In one example, the baseline temperature (C) is 90 Celsius.
- the look-up factor is based at least partially on the rotor speed ( ⁇ ), the stator winding temperature (t S ) and a characterized torque error.
- the first method of estimating torque may be a current-based flux map method at the baseline temperature (C), as known to those skilled in the art.
- the second method of estimating torque may be an active power-based method at the baseline temperature (C), as known to those skilled in the art. Any two different methods of estimating torque known to those skilled in the art may be employed.
- the vertical axis 202 represents the difference between the torque estimated based on a flux map method versus an active power method [both at the baseline temperature (C)] as a function of speed.
- the horizontal axis 204 represents the torque command (T*) (in Newton-meters).
- Traces 206 , 208 and 210 represent data at rotor speed values of 1000 rpm, 1500 rpm and 2000 rpm, respectively.
- the traces 206 , 208 and 210 exhibit non-linearities at high commanded torque values, e.g. above approximately 80% of the peak torque command.
- the look-up factor may be taken as the slope of portion 212 , where traces 208 and 210 coincide. Any interpolation method known to those skilled in the art may be employed to obtain the look-up factor, such as simple linear approximation or a polynomial curve-fit or any other curve-fitting method.
- the look-up factor may characterize error between torque estimated from two different methods (both at the baseline temperature) as a function of rotor speed (in this case between 500 and 2000 rpm), up to 80% of peak torque.
- the predefined first constant (Y) may be taken as the y-intercept of the trace portion 208 . In one example, the value of Y is taken as 5%.
- FIG. 4 is an example torque versus rotor speed diagram for the machine of FIG. 1 and may be employed to obtain the torque achieved (T a ).
- the data may be obtained in a testing dynamo or lab conditions.
- the vertical axis 302 represents the torque achieved (in Newton-meters) and the horizontal axis 304 represents the motor speed (in RPM).
- the first portion 306 indicates the low-speed torque achieved (T LS ) at relatively lower rotor speeds, such as torque speeds lower than first speed ( ⁇ 1 ), indicated by line 308 .
- the second portion 310 indicates the high-speed torque achieved (T HS ) at relatively higher rotor speeds, such as torque speeds higher than second speed ( ⁇ 2 ), indicated by line 312 .
- the third portion 314 indicates the torque achieved in a “blend zone” with torque speeds between first and second speeds ( ⁇ 1 and ⁇ 2 ).
- the upper boundary 316 and lower boundary 318 show the limits of error 320 of the torque achieved.
- the low-speed torque achieved (T LS ) and the high-speed torque achieved (T HS ) may also be estimated as:
- P mech is defined as the mechanical output power of the machine
- P dc is defined as the DC power into the machine 12 and may be obtained as the product of the DC link voltage (V dc ) (e.g., voltage from a battery pack 56 operatively connected to the machine 12 ) and the DC current (i dc ).
- V dc DC link voltage
- i dc DC current
- P inv _ loss is defined as the inverter loss (converting DC to AC). It may be a nonlinear polynomial, based on the inverter models known to those skilled in the art.
- P Stat-loss is defined as the loss or heat dissipated in the stator windings 30. The value of heat dissipated may be characterized or obtained with sensors or FEA models while the machine 12 is not in use.
- the stator winding resistance (r C ) and torque achieved (T C ) at the baseline temperature, such as 90 Celsius, may be obtained through measurements in a laboratory setting or test cell.
- the magnetic flux may be measured using a magnetic flux sensor 50 or estimated, as previously described.
- the DQ reference frame currents (i d , t q ) are obtained from the detected currents of the motor (I a , I b and I c ) which are transformed to the DQ reference frame using motor position or rotor angle 36 (shown in FIG. 1 ).
- a position sensor 51 may be employed to determine the rotor angle 36 .
- the commanded currents (i* d , i* q ) are obtained based on the torque command (T*) using look up tables.
- step 102 F of FIG. 2 the controller 40 is configured to obtain the high-speed resistance factor (r H ) based at least partially on the second function (F 2 ), the third function (F 3 ), the fourth function (F 4 ) and the fifth function such that:
- the low-speed resistance factor (r L ) accounts for variation in stator resistance when the rotor speed ( ⁇ ) is relatively low.
- the controller 40 is configured to obtain a total resistance value (R) for the stator windings based at least partially on a weighting factor (k) and the first and low-speed resistance factors such that:
- R [k*r H +(1- k )* r L ] and 0 ⁇ k ⁇ 1.
- the weighting factor (k) may be one when the rotor speed ( ⁇ ) is at or above a predefined high speed threshold (e.g., ⁇ 5000 rpm).
- the weighting factor (k) may be zero when the rotor speed ( ⁇ ) is at or below a predefined low speed threshold (e.g. ⁇ 3000 rpm).
- execution of the method 100 by the controller 40 determines stator winding resistance at high motor speeds corresponding to the torque command (T*), which includes the effect of AC resistance that is known to change with stator winding temperature.
- the method 100 utilizes magnetic flux (from a magnetic flux sensor 50 or FEA model) and the difference between two independent torque estimations, such as for example, using current-based (flux map) and active power-based estimates of torque.
- Stator resistance variation at high speed is non-linear and varies with operating temperature and current. Real time accurate estimation of stator winding resistance allows for improved utilization of the available DC link (such as provided by battery pack 56 ), thereby increasing peak torque and motor efficiency.
- the controller 40 (and execution of the method 100 ) improves the functioning of the assembly 10 by determining the stator winding resistance of a complex system with minimal calibration required.
- the controller 40 of FIG. 1 may be an integral portion of, or a separate module operatively connected to, other controllers of the assembly 10 .
- the controller 40 of FIG. 1 includes a computer-readable medium (also referred to as a processor-readable medium), including any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer).
- a medium may take many forms, including, but not limited to, non-volatile media and volatile media.
- Non-volatile media may include, for example, optical or magnetic disks and other persistent memory.
- Volatile media may include, for example, dynamic random access memory (DRAM), which may constitute a main memory.
- DRAM dynamic random access memory
- Such instructions may be transmitted by one or more transmission media, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer.
- Some forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read.
- Look-up tables, databases, data repositories or other data stores described herein may include various kinds of mechanisms for storing, accessing, and retrieving various kinds of data, including a hierarchical database, a set of files in a file system, an application database in a proprietary format, a relational database management system (RDBMS), etc.
- Each such data store may be included within a computing device employing a computer operating system such as one of those mentioned above, and may be accessed via a network in any one or more of a variety of manners.
- a file system may be accessible from a computer operating system, and may include files stored in various formats.
- An RDBMS may employ the Structured Query Language (SQL) in addition to a language for creating, storing, editing, and executing stored procedures, such as the PL/SQL language mentioned above.
- SQL Structured Query Language
Abstract
Description
- The disclosure relates generally to the determination of stator winding resistance in an electric machine assembly.
- An electric machine such as an interior permanent magnet machine generally includes a rotor having a plurality of magnets of alternating polarity. The rotor is rotatable within a stator which generally includes multiple stator windings and magnetic poles of alternating polarity. An electric machine, such as a motor, takes in electrical energy in terms of a potential difference and a current flow, converting it to mechanical work. Because electric machines are not 100% efficient, some of the electric energy is lost to heat, due to electrical resistance of the windings. The electrical resistance of the stator windings at high rotor speeds varies considerably with operating temperature and current.
- An electric machine assembly has an electric machine having a stator and a rotor. The stator has stator windings at a stator winding temperature (tS) and the rotor is configured to rotate at a rotor speed (ω). A controller is operatively connected to the electric machine and configured to receive a torque command (T*). The controller has a processor and tangible, non-transitory memory on which is recorded instructions for executing a method for determining stator winding resistance. Execution of the instructions by the processor causes the controller to determine a high-speed resistance factor (rH) for the stator windings. The high-speed resistance factor (rH) is based at least partially on the torque command (T*), the stator winding temperature (tS), the rotor speed (ω), a characterized torque error and the number of pole pairs (P) of the electric machine.
- The controller may be configured to determine a low-speed resistance factor (rL) for the stator windings based at least partially on a predefined wire coefficient (a), a measured stator resistance (r0) at a predefined measuring temperature (t0), a temperature difference between the stator winding temperature (tS) and a predefined measuring temperature (t0) such that: rL=[r0(1+α*(tS-t0)]. The controller may be configured to determine a total resistance (R) for the stator windings based at least partially on a weighting factor (k) and the high and low-speed resistance factors such that R=[k* rH+(1-k)* rL] and 0≦k≦1. The controller may be operative to control at least one operating parameter of the electric machine based at least partially on the total resistance (R) for the stator windings to achieve improved performance and/or efficiency.
- A first temperature sensor may be operatively connected to the controller and configured to measure the stator winding temperature (tS). A second temperature sensor may be operatively connected to the controller and configured to measure a rotor temperature. A magnetic flux sensor may be operatively connected to the controller and configured to measure a magnetic flux of the electric machine. A method for determining the high and low-speed resistance factors and total resistance (R) is provided. The method and assembly described herein minimizes the use of extensive look-up tables and complex curve-fitting for estimating the variation in stator resistance at various rotor speeds. The method utilizes estimated magnetic flux (from a magnetic flux sensor or FEA model) and two independent torque estimations, such as using current-based (flux map) and active power-based estimates.
- The high-speed resistance factor (rH) accounts for variation in stator resistance when the rotor speed (ω) is relatively high. The low-speed resistance factor (rL) accounts for variation in stator resistance when the rotor speed (ω) is relatively low. The weighting factor (k) may be one when the rotor speed (ω) is at or above a predefined high speed threshold (e.g. ω≧5000 rpm). The weighting factor (k) may be zero when the rotor speed (ω) is at or below a predefined low speed threshold (e.g. ω≦3000 rpm).
- Determining the high-speed resistance factor (rH) includes: obtaining a first function (F1), via the controller, as a product of a look-up factor and the torque command (T*), wherein the look-up factor is based at least partially on the rotor speed, the stator winding temperature (tS) and a characterized torque error. The characterized torque error may be defined as the difference between any two independent or different estimates of torque produced by the machine. A second function (F2) may be obtained, via the controller, as a sum of the first function (F1), a torque achieved (Ta) at the rotor temperature and a predefined first constant (Y) such that: F2=(F1+Ta+Y).
- A third function (F3) may be obtained, via the controller, as a product of a stator winding resistance (rC) at a baseline temperature and a torque achieved (TC) at the baseline temperature such that: F3=(TC*TC). A fourth function (F4) may be obtained, via the controller, as a difference between a magnetic flux (ψtr) at the rotor temperature and a magnetic flux (ψC) at the baseline temperature such that: F4=(ψtr-ψC). A fifth function (F5) may be obtained, via the controller, as a product of the pole pair (P), the rotor speed (ω), a commanded current (i*d) and an inductance factor (Ld0) such that: F5=[P*ω*i*d*Ld0].
- The high-speed resistance factor (rH) may be obtained based at least partially on the second function (F2), the third function (F3), the fourth function (F4) and the fifth function (F5) such that: rH=[1/(2* F2)] [2*F3—(3*F4*F5)].
- The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in connection with the accompanying drawings.
-
FIG. 1 is a schematic fragmentary partly sectional view of an electric machine assembly with a stator having a stator windings; -
FIG. 2 is a flowchart for a method for determining the high-speed resistance factor (rH), the low-speed resistance factor (rL) and total resistance (R) for the stator windings ofFIG. 1 ; -
FIG. 3 is an example diagram for obtaining a look-up factor used in the method ofFIG. 2 ; -
FIG. 4 is an example torque versus machine speed diagram for the assembly ofFIG. 1 . - Referring to the drawings, wherein like reference numbers refer to like components,
FIG. 1 schematically illustrates anelectric machine assembly 10. Theassembly 10 includes anelectric machine 12. Theassembly 10 may be a component of adevice 11. Thedevice 11 may be a passenger vehicle, performance vehicle, military vehicle, industrial vehicle, robot, farm implement, sports-related equipment or any other type of apparatus. - Referring to
FIG. 1 , theelectric machine 12 includes astator 14 and arotor 16. Therotor 16 may include a firstpermanent magnet 18 and a secondpermanent magnet 20 of alternating polarity around the outer periphery of arotor core 22. Therotor 16 may include any number of permanent magnets; for simplicity only two are shown. Therotor 16 is rotatable at a rotor speed (ω) within thestator 14. While the embodiment shown inFIG. 1 illustrates a three-phase, single pole-pair (i.e. two pole) machine, it is understood that any number of phases or pole pairs may be employed. - The
stator 14 includes astator core 24 which may be cylindrically shaped with a hollow interior. Thestator core 24 may include a plurality of inwardly-protrudingstator teeth 26A-F, separated by gaps orslots 28. In the embodiment shown inFIG. 1 ,stator windings 30 may be operatively connected to thestator core 24, such as for example, being coiled around thestator teeth 26A-F. Theelectric machine 12 may take many different forms and include multiple and/or alternate components and facilities. While an exampleelectric machine 12 is shown in the Figures, the components illustrated in the Figures are not intended to be limiting. Indeed, additional or alternative components and/or implementations may be used. - Electric current flowing in the
stator windings 30 causes a rotating magnetic field in thestator 14. Referring toFIG. 1 , thestator windings 30 may include six sets of windings; one set for each of three phases (the first phase throughstator windings stator windings stator windings FIG. 1 , a quadrature (q)magnetic axis 32 and a direct (d)magnetic axis 34 are shown. The first and secondpermanent magnets permanent magnet fluxes rotor angle 36 is zero. As previously noted, theelectric machine 12 may be of any type, including, but not limited to, induction and synchronous machines. - Referring to
FIG. 1 , theassembly 10 includes acontroller 40 operatively connected to or in electronic communication with theelectric machine 12. Thecontroller 40 is configured to receive a torque command (T*). Referring toFIG. 1 , thecontroller 40 includes at least oneprocessor 42 and at least one memory 44 (or any non-transitory, tangible computer readable storage medium) on which are recorded instructions for executingmethod 100, shown inFIG. 2 , for determining electrical resistance of thestator windings 30, including a high-speed resistance factor (rH), a low-speed resistance factor (rL) and a total resistance (R). Thememory 44 can store controller-executable instruction sets, and theprocessor 42 can execute the controller-executable instruction sets stored in thememory 44. Themethod 100 andassembly 10 described herein minimizes the use of extensive look-up tables and complex curve-fitting for estimating the variation in stator resistance at various rotor speeds. - The
controller 40 ofFIG. 1 is specifically programmed to execute the steps of the method 100 (as discussed in detail below with respect toFIG. 2 ) and can receive inputs from various sensors. Referring toFIG. 1 , theassembly 10 may include a first temperature sensor 46 (such as a thermistor or thermocouple) in communication (e.g., electronic communication) thecontroller 40, as shown inFIG. 1 . Thefirst temperature sensor 46 is capable of measuring the temperature of thestator windings 30A-F and sending input signals to thecontroller 40. Thefirst temperature sensor 46 may be installed or mounted on one of thestator windings 30A-F. Alternatively, sensor-less stator winding temperature estimation techniques known to those skilled in the art may be employed, including, but not limited to: a high-frequency carrier signal injection technique and a motor thermal model computed based on machine geometry and its thermal and electrical properties. Asecond temperature sensor 48 may be in communication with thecontroller 40 and configured to measure the temperature of therotor 16, referred to herein as the “rotor temperature.” - Referring to
FIG. 1 , theassembly 10 may include amagnetic flux sensor 50 in communication (e.g., electronic communication) with thecontroller 40. Themagnetic flux sensor 50 is capable of measuring the magnetic flux emanating from theelectric machine 12, such as flux lines frompermanent magnets rotor 16, and sending input signals to thecontroller 40. In one example, themagnetic flux sensor 50 is a Hall-effect sensor, however, any type of magnetic flux sensing device known to those skilled in the art may be employed. Additionally,controller 40 may be programmed to determine the magnetic flux based on other methods, without employing any sensors, such as finite element analysis (FEA) or any method or mechanism known to those skilled in the art. Abattery pack 56 may be operatively connected to themachine 12 as a source of DC voltage. - Referring now to
FIG. 2 , a flowchart of themethod 100 stored on and executable by thecontroller 40 ofFIG. 1 is shown.Method 100 need not be applied in the specific order recited herein. Furthermore, it is to be understood that some steps may be eliminated. Themethod 100 utilizes estimated magnetic flux (from amagnetic flux sensor 50 or FEA model) and two independent motor torque estimations, such as using current-based (flux map) and active power-based estimates. Referring toFIG. 2 ,method 100 may begin withstep 102, where thecontroller 40 is programmed or configured to obtain the high-speed resistance factor (rH). Step 102 includes sub-steps 102A through F. - In step 102A of
FIG. 2 , thecontroller 40 is programmed or configured to obtain a first function (F1) as a product of a look-up factor and the torque command (T*). The torque command (T*) may be received by thecontroller 40 in response to an operator input or an automatically-fed input condition monitored by thecontroller 40. If thedevice 11 is a vehicle, thecontroller 40 may determine the torque command (T*) based on input signals from an operator through anaccelerator pedal 52 andbrake pedal 54, shown inFIG. 1 . - To obtain the look-up factor, characterization data is taken at various rotor speeds (ω) at a baseline temperature (C). The baseline temperature (C) may be varied based on the particular application. In one example, the baseline temperature (C) is 90 Celsius. The look-up factor is based at least partially on the rotor speed (ω), the stator winding temperature (tS) and a characterized torque error. The characterized torque error (ΔT) is defined as the difference between a first torque estimate T1 (i.e., torque estimated using a first method) and a second torque estimate T2 (i.e., torque estimated using a second method), such that (ΔT=T1-T2). The first method of estimating torque may be a current-based flux map method at the baseline temperature (C), as known to those skilled in the art. The second method of estimating torque may be an active power-based method at the baseline temperature (C), as known to those skilled in the art. Any two different methods of estimating torque known to those skilled in the art may be employed.
- Referring to
FIG. 3 , an example diagram for obtaining the look-up factor is shown. InFIG. 3 , thevertical axis 202 represents the difference between the torque estimated based on a flux map method versus an active power method [both at the baseline temperature (C)] as a function of speed. Thehorizontal axis 204 represents the torque command (T*) (in Newton-meters).Traces - As shown in
FIG. 3 , thetraces FIG. 3 , the look-up factor may be taken as the slope ofportion 212, where traces 208 and 210 coincide. Any interpolation method known to those skilled in the art may be employed to obtain the look-up factor, such as simple linear approximation or a polynomial curve-fit or any other curve-fitting method. The look-up factor may characterize error between torque estimated from two different methods (both at the baseline temperature) as a function of rotor speed (in this case between 500 and 2000 rpm), up to 80% of peak torque. - In
step 102B ofFIG. 2 , thecontroller 40 is configured to obtain a second function (F2) as a sum of the first function (F1), a torque achieved (Ta) at a rotor temperature and a predefined first constant (Y) such that: F2= (F1+Ta+Y). The predefined first constant (Y) may be taken as the y-intercept of thetrace portion 208. In one example, the value of Y is taken as 5%. The torque achieved (Ta) is understood to be electrical torque and may be defined as a weighted sum of a low-speed torque achieved (TLS) and a high-speed torque achieved (THS), such that: Ta=[(1-K)* TLS+K*THS]. -
FIG. 4 is an example torque versus rotor speed diagram for the machine ofFIG. 1 and may be employed to obtain the torque achieved (Ta). The data may be obtained in a testing dynamo or lab conditions. InFIG. 4 , thevertical axis 302 represents the torque achieved (in Newton-meters) and thehorizontal axis 304 represents the motor speed (in RPM). Thefirst portion 306 indicates the low-speed torque achieved (TLS) at relatively lower rotor speeds, such as torque speeds lower than first speed (ω1), indicated byline 308. Thesecond portion 310 indicates the high-speed torque achieved (THS) at relatively higher rotor speeds, such as torque speeds higher than second speed (ω2), indicated byline 312. Thethird portion 314 indicates the torque achieved in a “blend zone” with torque speeds between first and second speeds (ω1 and ω2). The weighting factor for a particular rotor speed (ω), may be obtained as: K=(ω-ω1)/(ω2-ω1). Theupper boundary 316 andlower boundary 318 show the limits oferror 320 of the torque achieved. The low-speed torque achieved (TLS) and the high-speed torque achieved (THS) may also be estimated as: -
- Here, Pmech is defined as the mechanical output power of the machine, Pdc is defined as the DC power into the
machine 12 and may be obtained as the product of the DC link voltage (Vdc) (e.g., voltage from abattery pack 56 operatively connected to the machine 12) and the DC current (idc). Additionally, Pinv _ loss is defined as the inverter loss (converting DC to AC). It may be a nonlinear polynomial, based on the inverter models known to those skilled in the art. PStat-loss is defined as the loss or heat dissipated in thestator windings 30. The value of heat dissipated may be characterized or obtained with sensors or FEA models while themachine 12 is not in use. - In
step 102C ofFIG. 2 , thecontroller 40 is configured to obtain a third function (F3), as a product of a stator winding resistance (rC) at a baseline temperature (C) and a torque achieved (TC) at the baseline temperature (C) such that: F3=(TC*rC). The stator winding resistance (rC) and torque achieved (TC) at the baseline temperature, such as 90 Celsius, may be obtained through measurements in a laboratory setting or test cell. - In
step 102D ofFIG. 2 , thecontroller 40 is configured to obtain a fourth function (F4) as a difference between a magnetic flux (ψtr) at the rotor temperature and a magnetic flux (ψC) at the baseline temperature such that: F4=(ψtr-ψC). The magnetic flux may be measured using amagnetic flux sensor 50 or estimated, as previously described. - In
step 102E ofFIG. 2 , thecontroller 40 is configured to obtain a fifth function (F5) as a product of the pole pair (P), the rotor speed (ω), a commanded current (i*d) and an inductance factor (Ld0) such that: F5=[P*ω*i*d*Ld0]. The DQ reference frame currents (id, tq) are obtained from the detected currents of the motor (Ia, Ib and Ic) which are transformed to the DQ reference frame using motor position or rotor angle 36 (shown inFIG. 1 ). Aposition sensor 51 may be employed to determine therotor angle 36. The commanded currents (i*d, i*q) are obtained based on the torque command (T*) using look up tables. The inductance (L) of the stator winding may be obtained by any method known to those skilled in the art. In one example, the inductance (L) is obtained as a function of the number of turns in the stator winding (N), the relative permeability of the winding core material (μ), the area of the winding/coil in square meters and the average length of the winding/coil in meters (l), such that: L=(N2*μ*A/l). - In
step 102F ofFIG. 2 , thecontroller 40 is configured to obtain the high-speed resistance factor (rH) based at least partially on the second function (F2), the third function (F3), the fourth function (F4) and the fifth function such that: -
r H=[1/(2*F 2)][2*F 3—(3*F 4*F5)]. - In
step 104 ofFIG. 2 , thecontroller 40 is configured to obtain a low-speed resistance factor (rL) for the stator windings based at least partially on a predefined wire coefficient (α), a measured stator resistance (r0) at a predefined measuring temperature (t0), a temperature difference between the stator winding temperature (tS) and a predefined measuring temperature (t0) such that: r2=[r0(1+α*(tS-t0)]. The low-speed resistance factor (rL) accounts for variation in stator resistance when the rotor speed (ω) is relatively low. - In
step 106 ofFIG. 2 , thecontroller 40 is configured to obtain a total resistance value (R) for the stator windings based at least partially on a weighting factor (k) and the first and low-speed resistance factors such that: -
R=[k*r H+(1-k)* r L] and 0≦k≦1. - The weighting factor (k) may be one when the rotor speed (ω) is at or above a predefined high speed threshold (e.g., ω≧5000 rpm). The weighting factor (k) may be zero when the rotor speed (ω) is at or below a predefined low speed threshold (e.g. ω≦3000 rpm).
- In summary, execution of the
method 100 by thecontroller 40 determines stator winding resistance at high motor speeds corresponding to the torque command (T*), which includes the effect of AC resistance that is known to change with stator winding temperature. Themethod 100 utilizes magnetic flux (from amagnetic flux sensor 50 or FEA model) and the difference between two independent torque estimations, such as for example, using current-based (flux map) and active power-based estimates of torque. Stator resistance variation at high speed is non-linear and varies with operating temperature and current. Real time accurate estimation of stator winding resistance allows for improved utilization of the available DC link (such as provided by battery pack 56), thereby increasing peak torque and motor efficiency. - The controller 40 (and execution of the method 100) improves the functioning of the
assembly 10 by determining the stator winding resistance of a complex system with minimal calibration required. Thecontroller 40 ofFIG. 1 may be an integral portion of, or a separate module operatively connected to, other controllers of theassembly 10. - The
controller 40 ofFIG. 1 includes a computer-readable medium (also referred to as a processor-readable medium), including any non-transitory (e.g., tangible) medium that participates in providing data (e.g., instructions) that may be read by a computer (e.g., by a processor of a computer). Such a medium may take many forms, including, but not limited to, non-volatile media and volatile media. Non-volatile media may include, for example, optical or magnetic disks and other persistent memory. Volatile media may include, for example, dynamic random access memory (DRAM), which may constitute a main memory. Such instructions may be transmitted by one or more transmission media, including coaxial cables, copper wire and fiber optics, including the wires that comprise a system bus coupled to a processor of a computer. Some forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip or cartridge, or any other medium from which a computer can read. - Look-up tables, databases, data repositories or other data stores described herein may include various kinds of mechanisms for storing, accessing, and retrieving various kinds of data, including a hierarchical database, a set of files in a file system, an application database in a proprietary format, a relational database management system (RDBMS), etc. Each such data store may be included within a computing device employing a computer operating system such as one of those mentioned above, and may be accessed via a network in any one or more of a variety of manners. A file system may be accessible from a computer operating system, and may include files stored in various formats. An RDBMS may employ the Structured Query Language (SQL) in addition to a language for creating, storing, editing, and executing stored procedures, such as the PL/SQL language mentioned above.
- The detailed description and the drawings or figures are supportive and descriptive of the disclosure, but the scope of the disclosure is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed disclosure have been described in detail, various alternative designs and embodiments exist for practicing the disclosure defined in the appended claims. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims.
Claims (17)
F 5 =[P*ω*i* d *L d0].
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US14/932,613 US9647602B1 (en) | 2015-11-04 | 2015-11-04 | Determination of stator winding resistance in an electric machine |
DE102016120056.5A DE102016120056A1 (en) | 2015-11-04 | 2016-10-20 | DETERMINATION OF STATISTICS DEVELOPMENT IN AN ELECTRIC MOTOR |
CN201610921159.6A CN106655980B (en) | 2015-11-04 | 2016-10-21 | The determination of stator winding resistance in motor |
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CN111175651A (en) * | 2020-01-10 | 2020-05-19 | 河北大学 | Big data-based wind turbine generator fault early warning and diagnosis system |
US20230019118A1 (en) * | 2021-07-15 | 2023-01-19 | Daniel R. Luedtke | Vehicle electric motor temperature estimation using neural network model |
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CN108258966B (en) * | 2018-01-10 | 2019-08-02 | 深圳赛美控电子科技有限公司 | A kind of method and device of Field orientable control |
RU2683954C1 (en) * | 2018-06-07 | 2019-04-03 | Общество с ограниченной ответственностью "СовЭлМаш" | Method for determining the resistance of the phases of three-phase electric rotating machines with combined windings |
IT201800010932A1 (en) * | 2018-12-10 | 2020-06-10 | Carel Ind Spa | OPERATING METHOD OF A REFRIGERATOR COMPRESSOR AND REFRIGERATOR COMPRESSOR |
US11366147B2 (en) * | 2020-09-02 | 2022-06-21 | Rockwell Automation Technologies, Inc. | Motor stator resistance calculation |
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JP3502040B2 (en) * | 2000-12-27 | 2004-03-02 | 本田技研工業株式会社 | Brushless DC motor constant detection device, brushless DC motor control device, and brushless DC motor constant detection program |
US8604803B2 (en) * | 2006-05-19 | 2013-12-10 | Pratt & Whitney Canada Corp. | System and method for monitoring temperature inside electric machines |
US7839108B2 (en) * | 2008-01-24 | 2010-11-23 | Gm Global Technology Operations, Inc. | Electric motor stator winding temperature estimation |
JP5055246B2 (en) * | 2008-10-31 | 2012-10-24 | 日立オートモティブシステムズ株式会社 | Control device for rotating electrical machine |
US8384338B2 (en) * | 2009-01-30 | 2013-02-26 | Eaton Corporation | System and method for determining stator winding resistance in an AC motor using motor drives |
US8487575B2 (en) * | 2009-08-31 | 2013-07-16 | GM Global Technology Operations LLC | Electric motor stator winding temperature estimation |
US8174222B2 (en) * | 2009-10-12 | 2012-05-08 | GM Global Technology Operations LLC | Methods, systems and apparatus for dynamically controlling an electric motor that drives an oil pump |
US8421391B2 (en) * | 2010-05-12 | 2013-04-16 | GM Global Technology Operations LLC | Electric motor stator winding temperature estimation systems and methods |
US8866428B2 (en) * | 2011-06-02 | 2014-10-21 | GM Global Technology Operations LLC | Method and apparatus for thermally monitoring a permanent magnet electric motor |
US8786244B2 (en) * | 2011-09-22 | 2014-07-22 | GM Global Technology Operations LLC | System and method for current estimation for operation of electric motors |
JP6261873B2 (en) * | 2013-04-18 | 2018-01-17 | 株式会社東芝 | Electric locomotive control device |
US20150229249A1 (en) * | 2014-02-13 | 2015-08-13 | GM Global Technology Operations LLC | Electronic motor-generator system and method for controlling an electric motor-generator |
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CN111175651A (en) * | 2020-01-10 | 2020-05-19 | 河北大学 | Big data-based wind turbine generator fault early warning and diagnosis system |
US20230019118A1 (en) * | 2021-07-15 | 2023-01-19 | Daniel R. Luedtke | Vehicle electric motor temperature estimation using neural network model |
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