Magnet management in electric machines

• US 9,602,043 B2
• Filed: 08/29/2014
• Issued: 03/21/2017
• Est. Priority Date: 08/29/2014
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Reddy, Patel Bhageerath, El-Refaie, Ayman Mohamed Fawzi, Huh, Kum Kang
• Primary Examiner(s): Ip, Paul
• Application Number:
  US14/473,216
• Publication Number:
  US 20160065112A1
• Time in Patent Office: 935 Days
• Field of Search: 318/400.02, 318/400.08, 318/400.21, 318430-434, 318/492, 318/473
• US Class Current: 1/1
• CPC Class Codes: H02P 2207/05 Synchronous machines, e.g. with permanent magnets or DC excitation
• CPC Class Codes: H02P 29/62 for raising the temperature of the motor
• CPC Class Codes: H02P 29/662 the rotor having permanent magnets H02P29/67 takes precedence

Abstract

A magnet management method of controlling a ferrite-type permanent magnet electrical machine includes receiving and/or estimating the temperature permanent magnets; determining if that temperature is below a predetermined temperature; and if so, then: selectively heating the magnets in order to prevent demagnetization and/or derating the machine. A similar method provides for controlling magnetization level by analyzing flux or magnetization level. Controllers that employ various methods are disclosed. The present invention has been described in terms of specific embodiment(s), and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.

Claims

1. A method of controlling an electrical machine, the method comprising:

measuring one of flux information and temperature information of a plurality of ferrite-type permanent magnets of a motor;

sending back-emf-information from an operating point control module in communication with the motor to a magnet management module, wherein the magnet management module;

receives of one the flux information and the temperature information;

determines if the temperature is below a predetermined temperature; and

if so, then perform at least one of the following;

selectively heats the plurality of ferrite-type permanent magnets in order to prevent demagnetization of the plurality of ferrite-type permanent magnets; and

derates the electrical machine.

2. The method of claim 1, the plurality of ferrite-type permanent magnets is selectively heated for a predetermined time period.

3. The method of claim 1, the plurality of ferrite-type permanent magnets is selectively heated until the plurality of permanent magnets reach a predetermined temperature.

4. The method of claim 1, the plurality of ferrite-type permanent magnets is selectively heated for a predetermined rate of rise temperature.

5. The method of claim 1, wherein the step of determining whether the temperature is below the predetermined temperature comprises determining if a time delay is available prior to operating the electrical machine.

6. The method of claim 5, wherein, if the time delay is not available, then the electrical machine is derated by limiting a maximum current through the electrical machine.

7. The method of claim 5, wherein if the time delay is available, then the plurality of ferrite-type permanent magnets are selectively heated in order to prevent demagnetization of the plurality of permanent magnets.

8. The method of claim 1, wherein the electrical machine is derated by limiting a current available to the electrical machine.

9. The method of claim 1, if the temperature is below the predetermined temperature, then operation of the electrical machine is deactivated.

10. The method of claim 1, wherein the magnet management module repeats at least one of the receiving step, the determining step, the selectively heating step, and the derating step.

11. The method of claim 1, wherein the temperature information of the plurality of ferrite-type permanent magnets is estimated based on one of:

indirectly measuring at least one temperature of the plurality of ferrite-type permanent magnets; and

estimating one of motor terminal quantities; and

injecting one of a test current and a test voltage to the electrical machine.

12. The method of claim 11, wherein the step of indirect measurement of at least one temperature of the plurality of ferrite-type permanent magnets comprises one of measuring one of:

a lamination temperature, an ambient temperature, a housing temperature, and a winding temperature; and

applying a thermal model of the electrical machine.

13. A control module for controlling an electrical machine, comprising:

a magnet management module in communication with an operating point control module,

wherein the magnet management module;

receives a temperature of a plurality of ferrite-type permanent magnets in an electrical machine;

compares the temperature with a predetermined temperature; and

sends current injection information to the operating point control module of the electrical machine, wherein the current injection information comprises instructions configured to prevent demagnetization of the plurality of ferrite-type permanent magnets.

14. The control module of claim 13, wherein back-emf information from the operating point control module is received by the magnet management module.

15. The control module of claim 14, wherein the back-emf information is derived from a current, a voltage, and a position of the electrical machine.

16. The control module of claim 13, wherein the current injection information comprises instructions for the operating point control module to perform at least one of:

heat the plurality of ferrite-type permanent magnets for a fixed duration of time;

heat the plurality of ferrite-type permanent magnets to a predetermined temperature; and

heat the plurality of ferrite-type permanent magnets to a predetermined rate of rise in temperature.

17. The control module of claim 13, wherein the current injection information comprises instructions for the operating point control module to perform at least one of:

derate operation of the electrical machine; and

delay operation of the electrical machine.

18. The control module of claim 17, wherein the instruction for derating operation of the electrical machine comprises instructions to limit current to the electrical machine.

19. The control module of claim 17, wherein the instruction for delaying operation of the electrical machine comprises instructions to perform one of:

deactivate operation of the electrical machine;

delay operation of the electrical machine for a time duration;

delay operation of the electrical machine until a predetermined temperature is reached; and

delay operation of the electrical machine until a predetermined rate of rise in temperature is reached.

20. The control module of claim 13, wherein the magnet management modules estimates the temperature of the plurality of ferrite-type permanent magnets based on one of:

indirectly measuring at least one temperature of the plurality of ferrite-type permanent magnets;

estimating one of motor terminal quantities; and

injecting one of test current and test voltage to the electrical machine.

21. A controller for an electrical machine, comprising:

a magnet management module in communication with an operating point control module, wherein the magnet management module;

receives or estimate a back-emf of a ferrite-type permanent magnet machine, said ferrite-type permanent magnet machine having a plurality of ferrite-type permanent magnets;

compares the received or estimated back-emf with a predetermined back-emf; and

sends current injection information to the operating point control module, wherein the current injection information comprises instructions configured to prevent demagnetization of the plurality of ferrite-type permanent magnets.

22. The controller of claim 21, wherein the current injection information comprises instructions configured to perform at least one of:

derate operation of the ferrite-type permanent magnet machine; and

delay operation of the ferrite-type permanent magnet machine.

23. The controller of claim 22, wherein the derate operation comprises instructions to limit current to the ferrite-type permanent magnet machine.

24. A method of controlling a ferrite-type permanent magnet electrical machine, the method comprising:

measuring a magnetization level of a plurality of ferrite-type permanent magnets of a motor;

sending the magnetization level to a magnet management module, wherein the magnet management module;

determines if the magnetization level is above a predetermined level; and

if so, then perform

at least one of the following;

selectively heat the plurality of ferrite-type permanent magnets in order to prevent demagnetization of the plurality of ferrite-type permanent magnets; and

derate the electrical machine.

25. The method of claim 24, wherein the magnetization level is estimated based on one of:

at least one of voltage and current quantities;

injecting one of test voltage and test current to the electrical machine; and

short circuit testing.

26. A controller, comprising:

a magnet management module in communication with an operating point control module, wherein the magnet management module;

injects one of a current or a voltage to a ferrite-type permanent magnet machine, said ferrite-type permanent magnet machine having a plurality of ferrite-type permanent magnets;

estimates impedance based on the injecting;

selectively heats the plurality of ferrite-type permanent magnets based on the estimated impedance; and

limits current to the machine.