Determination of stator winding resistance in an electric machine

Patent metadata

Field	Value
Publication number	US-9647602-B1
Application number	US-201514932613-A
Country	US
Kind code	B1
Filing date	Nov 4, 2015
Priority date	Nov 4, 2015
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

An electric machine assembly includes 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 (ω). A controller is operatively connected to the electric machine and has a processor and tangible, non-transitory memory on which is recorded instructions for executing a method for determining stator winding resistance. The controller is configured to determine a high-speed resistance factor (r H ) which is based at least partially on the torque command (T*), the stator winding temperature (t S ), the rotor speed (ω), a characterized torque error and the number of pole pairs (P). The controller may determine a total resistance value (R) based on a weighting factor (k), the high-speed resistance factor (r H ) and the low-speed resistance factor (r L ).

First claim

The invention claimed is:

1. An electric machine assembly comprising: an electric machine including a stator and a rotor, the stator having stator windings at a stator winding temperature (t s ) and the rotor being configured to rotate at a rotor speed (ω);
wherein the electric machine defines a number of pole pairs (P);
a controller operatively connected to the electric machine and configured to receive a torque command (T*);
wherein, the controller has a processor and tangible, non-transitory memory on which is recorded instructions for executing a method for determining stator winding resistance;
wherein 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 ) being based at least partially on the torque command (T*), the stator winding temperature (t s ), the rotor speed (ω) and the number of pole pairs (P);
wherein the controller is configured to determine a low-speed resistance factor (r L ) for the stator windings based at least partially on a predefined wire coefficient (α), a measured stator resistance (r 0 ) at a predefined measuring temperature (t 0 ), and a temperature difference between the stator winding temperature (t s ) and a predefined measuring temperature (t 0 ) such that: r L =[r 0 (1+α×(t s −t 0 ))]; and
wherein the controller is further configured to determine a total resistance (R) for the stator windings based at least partially on a weighting factor (k), the high-speed resistance factor (r H ) and the low-speed resistance factor (r L ) such that: R=[k×r H +(1−k)×r L ] and 0<k<1.

2. The assembly of claim 1 , further comprising:
a first temperature sensor operatively connected to the controller and configured to measure the stator winding temperature (t S );
a second temperature sensor operatively connected to the controller and configured to measure a rotor temperature; and
a magnetic flux sensor operatively connected to the controller and configured to measure a magnetic flux of the electric machine.

3. The assembly of claim 1 , wherein:
the weighting factor (k) is one when the rotor speed (ω) is above a predefined high speed threshold; and
the weighting factor (k) is zero when the rotor speed (ω) is below a predefined low speed threshold.

4. The assembly of claim 1 , wherein 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 (ω), the stator winding temperature (t S ) and a characterized torque error; and
wherein the characterized torque error is defined as a difference between two independent estimates of torque produced by the machine.

5. The assembly of claim 4 , wherein determining the high-speed resistance factor (r H ) includes: obtaining a second function (F 2 ), via the controller, as a sum of the first function (F 1 ), a torque achieved (T a ) at a rotor temperature and a predefined first constant (Y) such that: F 2 =(F 1 +T a +Y).

6. The assembly of claim 5 , wherein determining the high-speed resistance factor (r H ) includes: obtaining a third function (F 3 ), via the controller, as a product of a stator winding resistance (r C ) at a baseline temperature and a torque achieved (T C ) at the baseline temperature such that: F 3 =(T C *r C ).

7. The assembly of claim 6 , wherein determining the high-speed resistance factor (r H ) includes: obtaining a fourth function (F 4 ), via the controller, as a difference between the magnetic flux (ψ tr ) at the rotor temperature and the magnetic flux (ψ C ) at the baseline temperature such that: F 4 =(ψ tr −ψ C ).

8. The assembly of claim 7 , wherein determining the high-speed resistance factor (r H ) includes: obtaining a fifth function (F 5 ), via the controller, as a product of the pole pair (P), the rotor speed (ω), a commanded current (i d * ) and an inductance factor (L d0 ) such that: F 5 =[P*ω*i d * *L d0 ].

9. The assembly of claim 8 , wherein determining the high-speed resistance factor (r H ) includes obtaining 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 (F 5 ) such that: r H =[1/(2*F 2 )][2*F 3 −(3*F 4 *F 5 )].

10. A method for determining stator winding resistance in an electric machine assembly, the electric machine assembly including an electric machine with a stator having stator windings, a rotor configured to rotate at a rotor speed (ω) and a controller operatively connected to the electric machine, the controller having a processor and tangible, non-transitory memory, the method comprising:
determining a high-speed resistance factor (r H ) for the stator windings based at least partially on the torque command (T*), the stator winding temperature (t s ), the rotor speed (ω) and the number of pole pairs (P);
determining a low-speed resistance factor (r L ) for the stator windings based at least partially on a predefined wire coefficient (α), a measured stator resistance (r 0 ) at a predefined measuring temperature (t 0 ), a temperature difference between the stator winding temperature (t s ) and a predefined measuring temperature (t 0 ) such that: r L =[r 0 (1+α×(t s −t 0 ))];
determining a total resistance (R) for the stator windings based at least partially on a weighting factor (k), the high-speed resistance factor (r H ) and the low-speed resistance factor (r L ) such that: R=[k×r H +(1−k)×r L ] and 0<k<1;
and controlling the electric machine based upon the total resistance (R) for efficiency.

11. The method of claim 10 , wherein determining the high-speed resistance factor (r H ) includes:
obtaining a first function (F 1 ) 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 (ω), the stator winding temperature (t S ) and a characterized torque error.

12. The method of claim 11 , wherein determining the high-speed resistance factor (r H ) includes:
obtaining a second function (F 2 ) as a sum of the first function (F 1 ), a torque achieved at the rotor temperature (T tr ) and a predefined first constant (Y) such that: F 2 =(F 1 +T tr +Y); and
obtaining a third function (F 3 ) as a product of a stator winding resistance (r C ) at a baseline temperature and a torque achieved (T C ) at the baseline temperature such that: F 3 =(T C *r C ).

13. The method of claim 12 , wherein determining the high-speed resistance factor (r H ) includes:
obtaining a fourth function (F 4 ) as a difference between a magnetic flux (ψ tr ) at a rotor temperature and a magnetic flux (ψ C ) at a baseline temperature such that: F 4 =(ψ tr −ψ C ).

14. The method of claim 13 , wherein determining the high-speed resistance factor (r H ) includes:
obtaining a fifth function (F 5 ) as a product of the pole pair (P), the rotor speed (ω), a commanded current (i d * ) and an inductance factor (L d0 ) such that: F 5 =[P*ω*i d * *L d0 ].

15. The method of claim 14 , wherein determining the high-speed resistance factor (r H ) includes:
obtaining 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 (F 5 ) such that: r H =[1/(2*F 2 )][2*F 3 −(3*F 4 *F 5 )].

Assignees

• Gm Global Tech Operations Llc

Inventors

• Simili Dwarakanath V
• Jang Jihoon
• Jurkovic Sinisa

Classifications

• G01R31/343 Primary

  in operation · CPC title

• H02P29/0055 Primary

  Electricity · mapped topic

• H02P21/148

  Electricity · mapped topic

• G01R27/02 Primary

  Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant (by measuring phase angle only G01R25/00) · CPC title

• H02P21/14

  Estimation or adaptation of machine parameters, e.g. flux, current or voltage · CPC title