TEMPERATURE DETERMINATION METHOD FOR MAGNET TEMPERATURES ON MAGNETS OF ELECTRIC MOTORS

Abstract

A temperature determination method for magnet temperatures on magnets of electric motors has a test mode. A first voltage is applied to a test winding of a test motor with test magnets for impressing a first voltage-time area at first angles of a test motor rotating field. The test magnets are subject to a predefined magnet temperature. First current values are ascertained at the first angles and stored based on the predefined magnet temperature. In a normal mode, a second voltage is applied to a motor winding of an operations motor with motor magnets for impressing a second voltage-time area at second angles of a motor rotating field. The motor magnets have an operation-dependent magnet temperature. Second current values are determined at the second angles and stored based on the operation-dependent magnet temperature. The operation-dependent magnet temperature is determined by comparing a second current value with a first current value.

Claims

1.-11. (canceled)

12. A temperature determination method for magnet temperatures on magnets of electric motors, the method comprising: in test mode: applying a first voltage to a test winding of a test motor with test magnets to impress a first voltage-time area at first angles of a test motor rotating field, wherein the test magnets are subjected to a predefined magnet temperature; determining first current values at the first angles; and storing the first current values as a function of the predefined magnet temperature; and in normal mode: subsequently applying a second voltage to a motor winding of an operational motor with motor magnets to subsequently impress a second voltage-time area at second angles of an operational motor rotating field, wherein the motor magnets have an operation-dependent magnet temperature; subsequently determining second current values at the second angles; subsequently storing the second current values as a function of the operation-dependent magnet temperature; and determining the operation-dependent magnet temperature by comparing a second current value of an operation-dependent magnet temperature with a first current value of a predefined magnet temperature.

13. The temperature determination method of claim 12, further comprising: determining and storing a first maximum current value from the first current values for the predefined magnet temperature; and determining a second maximum current value from the second current values for the operation-dependent magnet temperature; wherein the operation-dependent magnet temperature is determined by comparing the second maximum current value of the operation-dependent magnet temperature with the first maximum current value of the predefined magnet temperature.

14. The temperature determination method of claim 13, wherein the operation-dependent magnet temperature is equal to the predefined magnet temperature when the second maximum current value is equal to the first maximum current value.

15. The temperature determination method of claim 13, wherein the operation-dependent magnet temperature is estimated at the predefined magnet temperature when the second maximum current value is not equal to the first maximum current value.

16. The temperature determination method of claim 13, further comprising forming a characteristic from respective first maximum current values of a plurality of predefined magnet temperatures, wherein the temperature of the operation-dependent magnet temperature is determined by comparing the second maximum current value of the operation-dependent magnet temperature with the respective first maximum current values of the characteristic as a function of the plurality of predefined magnet temperatures.

17. The temperature determination method of claim 16, wherein the operation-dependent magnet temperature is equal to one of the plurality of predefined magnet temperatures when the second maximum current value is equal to a first maximum current value of the characteristic as a function of one of the plurality of predefined magnet temperatures.

18. The temperature determination method of claim 16, wherein the operation-dependent magnet temperature is estimated at a closest of the plurality of predefined magnet temperatures when the second maximum current value is not equal to the respective first maximum current values of the characteristic as a function of the plurality of predefined magnet temperatures.

19. The temperature determination method of claim 12, further comprising: carrying out the test mode when the test motor is at rest; and carrying out the normal mode when the operational motor is at rest.

20. The temperature determination method of claim 12, wherein the test magnets of the test motor and the motor magnets of the operational motor are designed as permanent magnets.

21. The temperature determination method of claim 12, wherein the second voltage-time area in the normal mode is equal to the first voltage-time area in the test mode.

22. The temperature determination method of claim 12, wherein the first angles are equal in number and respective angular values to the second angles.

Description

[0052] The above-described properties, features and advantages of the present invention and the manner in which they are achieved will become clearer and more readily understandable in connection with the following description of the exemplary embodiments which will be explained in more detail with reference to the accompanying drawings in which:

[0053] FIG. 1 schematically illustrates the temperature determination method according to the invention by means of a structogram,

[0054] FIG. 2 schematically illustrates a motor model for a test motor In test mode and an operational motor in normal mode for the temperature determination method according to the invention as shown in FIG. 1,

[0055] FIG. 3 shows a schematic diagram for determining an operation-dependent magnet temperature for the temperature determination method according to the invention as shown in FIG. 1 or 2, and

[0056] FIG. 4 shows a schematic diagram with a current curve of second current values determined in normal mode as a function of determined operating temperatures.

[0057] FIG. 1 schematically illustrates the temperature determination method 1 according to the invention by means of a structogram.

[0058] The temperature determination method 1 is used to determine magnet temperatures on the magnets of electric motors.

[0059] In a test mode 4 of the temperature determination method 1, the following steps are carried out.

[0060] By applying 5 a first voltage U.sub.1 to at least one test winding of a test motor 7 having test magnets 11, a first voltage-time area 9 is impressed at first angles ?.sub.1 of a test motor rotating field.

[0061] The test magnets 11 are subjected to at least one predefined magnet temperature T.sub.MV for this purpose.

[0062] Determination 12 of first current values I.sub.1 at the first angles ?.sub.1 is carried out and the first current values I.sub.1 are stored 13 as a function of the at least one predefined magnet temperature T.sub.MV.

[0063] The steps of the test mode can be repeated in order to determine and store corresponding first current values as a function of the respective predefined magnet temperature T.sub.MV for further predefined magnet temperatures T.sub.MV.

[0064] In normal mode 14 of the temperature determination method 1, the following steps are carried out.

[0065] On subsequent application 15 of a second voltage U.sub.2 to at least one motor winding of an operational motor with motor magnets 18, a second voltage-time area 20 is subsequently impressed 19 at second angles ?.sub.2 of an operational motor's rotating field.

[0066] Here the motor magnets have an operation-dependent magnet temperature T.sub.MN arising accordingly on the motor magnets during normal mode 14.

[0067] Second current values I.sub.2 are subsequently determined 21 at the second angles ?.sub.2 and the second current values I.sub.2 are subsequently stored 22 as a function of the operation-dependent magnet temperature T.sub.MN.

[0068] Temperature determination 23 of the operation-dependent magnet temperature T.sub.MN is performed by comparing 24 at least one of the second current values I.sub.2 of the operation-dependent magnet temperature T.sub.MN with at least one of the first current values I.sub.1 of the at least one predefined magnet temperature T.sub.MV.

[0069] For further elaboration of the temperature determination method 1, additional steps will now be presented which are not shown or not completely shown in FIG. 1.

[0070] From the first current values I.sub.1 for the at least one predefined magnet temperature T.sub.MV, a first maximum current value is determined and stored, and from the second current values I.sub.2 for the operation-dependent magnet temperature T.sub.MN, a second maximum current value is determined and stored.

[0071] In the case of the maximum current values determined, the operation-dependent magnet temperature T.sub.MN is determined 23 by comparing 24 the second maximum current value of the operation-dependent magnet temperature T.sub.MN with the first maximum current value of the at least one predefined magnet temperature T.sub.MV.

[0072] If the second maximum current value is not equal to the first maximum current value, the operation-dependent magnet temperature T.sub.MN is determined in relation to the at least one predefined magnet temperature T.sub.MV.

[0073] A characteristic can also be formed from the respective first maximum current values of a plurality of predefined magnet temperatures T.sub.MV. The operation-dependent magnet temperature T.sub.MN is then determined 23 by comparing 24 the second maximum current value of the operation-dependent magnet temperature T.sub.MN with the respective first maximum current values of the characteristic in relation to the plurality of predefined magnet temperatures T.sub.MV.

[0074] If at this point the second maximum current value is not equal to the respective first maximum current values of the characteristic as a function of the plurality of predefined magnet temperatures T.sub.MV, the operation-dependent magnet temperature T.sub.MN is estimated to a closest of the plurality of predefined magnet temperatures T.sub.MV. Interpolation methods can be used for the estimation.

[0075] FIG. 2 schematically illustrates a motor model which describes both a test motor 7 in test mode and an operational motor 17 in normal mode, in each case as a motor 3 for the temperature determination method according to the invention as shown in FIG. 1.

[0076] Schematically, three windings are disposed around magnets 2 of the motor 2, three test windings 6 in respect of the test motor 7 and three motor windings 16 in respect of the operational motor 17, here in the sense of a three-phase AC motor.

[0077] Similarly to the description of FIG. 1, the first voltage U.sub.1 is applied to each of these windings 6, 16 for test mode on the test windings 6 and the second voltage U.sub.2 is applied to the motor winding 16 for normal mode.

[0078] In test mode, the first voltage-time area 9 is impressed in the test winding 6 at the first angles ?.sub.1 over an angular range ?.sub.B here of 380? and the first current value I.sub.1 is determined in each case. Similarly, in normal mode the second voltage-time area 20 is impressed in the test winding 16 over the angular range ?.sub.B at the second angles ?.sub.2 and the second current value I.sub.2 is determined in each case.

[0079] The first angles ?1 describe a test motor rotating field 10 as a fixed-stator rotating electrical field of the test motor 7 in test mode and the second angles ?.sub.2 describe a motor rotating field 26 as a fixed-stator electrical rotating field of the operational motor 17 in normal mode.

[0080] FIG. 3 shows a schematic diagram for determining an operation-dependent magnet temperature T.sub.MN for the temperature determination method 1 according to the invention as shown in FIG. 1 or 2.

[0081] A first coordinate axis of the diagram shows the predefined magnet temperature T.sub.MV and the operation-dependent magnet temperature T.sub.MN as temperature in ? C. plotted against a second coordinate axis of first maximum current values I.sub.1max and second maximum current values I.sub.2max as current in A.

[0082] The first maximum current values I.sub.1maxmaximum first current value I.sub.11max, maximum second current value I.sub.12max, maximum third current value I.sub.13max and maximum fourth current value I.sub.14maxdetermined in test mode as a function of the specified magnet temperature form the characteristic 25.

[0083] For this purpose, a second maximum current value I.sub.2max was determined in normal mode, which value is reflected in the characteristic 25. The second maximum current value I.sub.2maxhere 5.9 Aresults in a temperature of 75? C. shown on the first coordinate axis.

[0084] The maximum first current value I.sub.11max was determined at a first angular value ?.sub.11 of the first angle ?.sub.1, the maximum second current value I.sub.12max at a second angular value ?.sub.12 of the first angle ?.sub.1, the maximum third current value I.sub.13max at a third angular value ?.sub.13 of the first angle ?.sub.1 and the maximum fourth current value I.sub.14max at a fourth angular value ?.sub.14 of the first angle ?.sub.1.

[0085] The second maximum current value I.sub.2max was determined at the second angle ?.sub.2.

[0086] FIG. 4 shows a schematic diagram with current curves of second current values I.sub.2 determined in normal mode as a function of determined operation-dependent magnet temperatures T.sub.MN1, T.sub.MN2, T.sub.MN3, T.sub.MN4.

[0087] A first coordinate axis of the diagram shows second current values I.sub.2 as currents in A, plotted against a second coordinate axis with second angles ?.sub.2 at which the second current values I.sub.2 were determined in normal mode.

[0088] As a result of the diagram, the operation-dependent magnet temperatures determined in normal mode are shown in the form of curves of a temperature profile of a first operation-dependent magnet temperature T.sub.MN1 above a second operation-dependent magnet temperature T.sub.MN2, a third operation-dependent magnet temperature T.sub.MN3 and a fourth operation-dependent magnet temperature T.sub.MN4.

[0089] From the height of the curves of the respective operation-dependent magnet temperatures T.sub.MV1, T.sub.MV2, T.sub.MV3 and T.sub.MV4, it is possible to determine the prevailing magnetism quality of the motor magnets of the operational motor in normal mode.

[0090] Thus, the curve of the fourth operation-dependent magnet temperature T.sub.MN4 shows a clear loss of magnetism at this fourth operation-dependent magnet temperature T.sub.MN4.