Magnet degradation and damage controls and diagnostics for permanent magnet motors

Patent metadata

Field	Value
Publication number	US-9647591-B2
Application number	US-201514751481-A
Country	US
Kind code	B2
Filing date	Jun 26, 2015
Priority date	Jan 2, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

Techniques for motor magnet degradation controls and diagnostics are disclosed. An exemplary technique determines q-axis current, d-axis current, q-axis voltage, and/or d-axis voltage of a permanent magnet motor based upon sensed current and voltage information of the motor. This information is utilized to determine flux information. The flux information is utilized in evaluating collective state conditions of a plurality of motor magnets and evaluating localized state conditions of a subset of the plurality of motor magnets. The evaluations can be used to identify degradation or damage to one or more of the magnets which may occur as a result of elevated temperature conditions, physical degradation, or chemical degradation.

First claim

What is claimed is:

1. A method comprising:
operating a system comprising a permanent magnet motor and a variable frequency drive, the permanent magnet motor comprising a stator including a plurality of windings electrically coupled to terminals and a rotor including a plurality of permanent magnets, the variable frequency drive including a plurality of outputs electrically coupled with the terminals;
determining magnetic flux information based upon information indicative of a motor current, information indicative of a terminal voltage, information indicative of a motor inductance, and information indicative of a motor resistance;
identifying a collective flux error condition associated with the plurality of permanent magnets collectively based upon the flux information; and
identifying a localized flux error condition based upon the flux information associated with a subset of the plurality of permanent magnets including at least one of the magnets.

2. A method according to claim 1 further comprising determining d-axis current information, q-axis current information, and q-axis voltage information based upon sensed motor operation information, and wherein the act of determining the magnetic flux information is based upon the d-axis current information, the q-axis current information, the q-axis voltage information, d-axis inductance information, and stator resistance information.

3. A method according to claim 2 wherein the d-axis current information, the q-axis current information, and the q-axis voltage information are defined in a rotor reference frame.

4. A method according to claim 2 wherein the act of determining magnetic flux information comprises:
multiplying the q-axis current information and the stator resistance information to determine a first product value;
subtracting the first product value from the q-axis voltage information to determine a difference value;
integrating the difference value over time to determine an integration value;
multiplying the d-axis current information and the d-axis inductance to determine a second product value; and
determining the flux value by subtracting the second product value from the integration value.

5. A method according to claim 1 wherein the act of identifying a collective flux error condition based upon flux information associated collectively with the plurality of permanent magnets comprises evaluating averaged or filtered flux information relative to a threshold.

6. A method according to claim 5 wherein the threshold comprises a predetermined flux value measured after assembly of the motor.

7. A method according to claim 5 wherein the threshold is based upon an instantaneous flux function of the motor characterized after assembly of the motor.

8. A method according to claim 1 wherein the act of identifying a localized flux error condition based upon flux information associated with a subset of the plurality of permanent magnets comprises evaluating sampled or continuous instantaneous flux information relative to a threshold.

9. A method according to claim 1 wherein the magnetic flux information comprises the flux linkage for the air gap intermediate the rotor and the stator.

10. A method according to claim 1 wherein the sensed motor operation information utilized to determine the d-axis current information, the q-axis current information, and the q-axis voltage information comprises stator current information and terminal voltage information.

11. A method according to claim 1 wherein the d-axis inductance information and the stator resistance information are represented by predetermined values.

12. A method according to claim 1 wherein the system further comprises a refrigeration loop including a compressor driven by the permanent magnet motor.

13. A method according to claim 1 wherein the act of determining magnetic flux information comprises determining d-axis current information, q-axis current information, and d-axis voltage information based upon sensed motor operation information, and the determining magnetic flux information is based upon the d-axis current information, the q-axis current information, the d-axis voltage information, q-axis inductance information, and stator resistance information.

14. A method according to claim 13 wherein the d-axis current information, the q-axis current information, and the d-axis voltage information are defined in a stator reference frame.

15. A method according to claim 13 wherein the act of determining magnetic flux information comprises:
multiplying the d-axis current information and the stator resistance information to determine a first product value;
subtracting the first product value from the d-axis voltage information to determine a difference value;
integrating the difference value over time to determine an integration value;
multiplying the q-axis current information and the q-axis inductance to determine a second product value; and
determining the flux value by subtracting the second product value from the integration value.

16. A system comprising:
a permanent magnet motor including a stator including a plurality of windings electrically coupled to terminals and a rotor including a plurality of permanent magnets;
a variable frequency drive including a plurality of outputs electrically coupled with the terminals;
a controller configured to provide control signals to the variable frequency drive and receive sensed information relating to operation of the permanent magnet motor;
wherein the controller is configured to determine a magnetic flux characteristic based upon information indicative of motor current and information indicative of terminal voltage, evaluate a collective deterioration condition of the plurality of permanent magnets based upon the magnetic flux characteristic, and evaluate a localized deterioration condition of a localized portion of the plurality of permanent magnets based upon the magnetic flux characteristic.

17. A method according to claim 16 wherein the controller is configured to determine d-axis current information, q-axis current information, and q-axis voltage information based upon sensed motor current and sensed terminal voltage, and to determine the magnetic flux information based upon the d-axis current information, the q-axis current information, the q-axis voltage information, d-axis inductance information, and stator resistance information.

18. A method according to claim 17 wherein the d-axis current information, the q-axis current information, and the q-axis voltage information are defined in a rotating coordinate system.

19. A system according to claim 16 wherein the collective deterioration condition comprises one or more of excessive temperature, physical damage, and chemical damage.

20. A system according to claim 16 wherein the localized deterioration condition comprises one or more of excessive temperature, physical damage, and chemical damage.

21. A system according to claim 16 wherein the controller is configured to determine the magnetic flux characteristic by executing instructions stored on a non-transitory computer readable medium, said instructions comprising an integration operation.

22. A system according to claim 21 wherein said instructions consist essentially of integration operations, multiplication operations, and addition or subtraction operations.

23. A system according to claim 21 wherein said instructions are independent of frequency information.

Assignees

• Trane Int Inc

Inventors

• West Nathan Thomas
• Foye David Marshall

Classifications

• G01R31/343

  in operation · CPC title

• G01R31/34

  Testing dynamo-electric machines · CPC title

• H02P29/0044

  Electricity · mapped topic

• H02P21/141 Primary

  Flux estimation · CPC title

• H02P29/0066

  Electricity · mapped topic