METHOD FOR OPERATING AN ELECTRICALLY COMMUTATED MACHINE

Abstract

A method for operating an electrically commutated machine. In at least one method step, in particular in at least one method step of overmodulation operation of the electrically commutated machine, a precommutation angle of the electrically commutated machine is set depending on an efficiency of the electrically commutated machine.

Claims

1. A method for operating an electrically commutated machine, the method comprising, in at least one method step, setting a precommutation angle (16) of the electrically commutated machine depending on an efficiency of the electrically commutated machine.

2. The method according to claim 1, characterized in that in at least one method step, at least one commutation signal (18) of the electrically commutated machine is overmodulated.

3. A method according to claim 1, characterized in that in at least one method step, the precommutation angle (16) is set on the basis of at least one continuous current characteristic curve (20) of the electrically commutated machine.

4. The method according to claim 1, characterized in that at least one method step involves ascertaining at least one current characteristic curve (20) of the electrically commutated machine for setting the precommutation angle (16) at at least one operating temperature of the electrically commutated machine.

5. The method according to claim 1, characterized in that in at least one method step, the precommutation angle (16) is set to a value which achieves a highest efficiency for a given operating state.

6. The method according to claim 1, characterized in that in at least one method step, efficiency-dependent setting of the precommutation angle (16) is deactivated.

7. The method according to claim 1, characterized in that at least one method step involves determining a starting point (22) of a deviation from a current characteristic curve (20) of the electrically commutated machine for setting the precommutation angle (16) depending on at least one operating parameter of the electrically commutated machine.

8. The method according to claim 1, further comprising at least one compensation step (24) for adapting the precommutation angle (16) to an ambient parameter.

9. An electrically commutated machine comprising at least one open-loop or closed-loop control unit (26) for carrying out a method according to claim 1.

10. A cooling device for circulating a cooling fluid, comprising at least one conveying element (30) for conveying the cooling fluid, and comprising at least one electrically commutated machine according to claim 9 for driving the conveying element.

11. A method for operating an electrically commutated machine, the method comprising, in at least one method step of overmodulation operation (14) of the electrically commutated machine, setting a precommutation angle (16) of the electrically commutated machine depending on an efficiency of the electrically commutated machine.

12. The method according to claim 11, characterized in that in at least one method step of overmodulation operation (14) of the electrically commutated machine, at least one commutation signal (18) of the electrically commutated machine is overmodulated.

13. A method according to claim 11, characterized in that in at least one one method step of overmodulation operation (14) of the electrically commutated machine, the precommutation angle (16) is set on the basis of at least one continuous current characteristic curve (20) of the electrically commutated machine.

14. The method according to claim 11, characterized in that at least one method step involves ascertaining at least one current characteristic curve (20) of the electrically commutated machine for setting the precommutation angle (16) at at least one operating temperature of the electrically commutated machine.

15. The method according to claim 11, characterized in that in at least one method step of overmodulation operation (14) of the electrically commutated machine, the precommutation angle (16) is set to a value which achieves a highest efficiency for a given operating state.

16. The method according to claim 11, characterized in that in at least one method step of field weakening operation (21) of the electrically commutated machine, efficiency-dependent setting of the precommutation angle (16) is deactivated.

17. The method according to claim 11, characterized in that at least one method step involves determining a starting point (22) of a deviation from a current characteristic curve (20) of the electrically commutated machine for setting the precommutation angle (16) depending on at least one operating parameter of the electrically commutated machine.

18. The method according to claim 11, further comprising at least one compensation step (24) for adapting the precommutation angle (16) to an ambient parameter.

19. An electrically commutated machine comprising at least one open-loop or closed-loop control unit (26) for carrying out a method according to claim 11.

20. A cooling device for circulating air for cooling a vehicle motor, comprising at least one conveying element (30) for conveying the air, and comprising at least one electrically commutated machine according to claim 19 for driving the conveying element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further advantages will become apparent from the following description of the drawing. The drawing illustrates one exemplary embodiment of the invention. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them to form advantageous further combinations.

[0018] In the figures:

[0019] FIG. 1 shows a schematic illustration of a cooling device according to the invention,

[0020] FIG. 2 shows a schematic illustration of the electrically commutated machine according to the invention,

[0021] FIG. 3 shows a flow diagram of a method according to the invention in a schematic illustration, and

[0022] FIG. 4 shows a current characteristic curve of the method according to the invention.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a cooling device 28. The cooling device 28 is provided for circulating a cooling fluid, in particular for cooling a vehicle motor. The cooling device 28 comprises at least one conveying element 30. The conveying element 30 is provided for conveying the cooling fluid, in particular air. The cooling device 28 comprises at least one electrically commutated machine 12. The electrically commutated machine 12 is provided for driving the conveying element 30. Preferably, the conveying element 30 is embodied as a fan element. It is conceivable for the cooling device 28 to have a holding unit for mounting at a location of use, in particular in a vehicle motor compartment.

[0024] FIG. 2 shows the electrically commutated machine 12. The electrically commutated machine 12 comprises at least one open-loop or closed-loop control unit 26. The open-loop or closed-loop control unit 26 is provided for carrying out a method 10 (see FIG. 3). Preferably, the electrically commutated machine 12 comprises at least one stator 32. Preferably, the stator 32 comprises at least one inductive component 34, 36, 38. Preferably, the inductive component 34, 36, 38 is embodied as a wire winding around a structural element 40, 42, 44 of the stator 32. Preferably, the stator 32 comprises three inductive components 34, 36, 38. Preferably, at least two, preferably all, inductive components 34, 36, 38 comprise at least one common potential step, in particular a common ground. Preferably, the inductive components 34, 36, 38 are arranged at regular distances, in particular in a circular fashion, at the stator 32.

[0025] Preferably, the electrically commutated machine 12 comprises at least one switching unit 46, in particular a transistor unit, for switching the at least one inductive component 34, 36, 38. Preferably, the switching unit 46 is provided, in particular additionally, for amplifying a commutation signal 18 for the at least one inductive component 34, 36, 38. Preferably, the switching unit 46 is embodied as a bridge circuit and/or a half-bridge circuit, in particular as a B6 bridge and/or as a 2H bridge. Preferably, the open-loop or closed-loop control unit 26 is provided for controlling the switching unit 46, in particular for generating the commutation signal 18. Preferably, the open-loop or closed-loop control unit 26 is provided for applying a pulse width modulation to the commutation signal 18. Preferably, the electrically commutated machine 12 comprises at least one connection unit 47 for a current supply and/or voltage supply of the electrically commutated machine 12. Preferably, the electrically commutated machine 12 comprises at least one decoupling unit 48, in particular a link circuit capacitor unit, between the connection unit 47 and the switching unit 46.

[0026] Preferably, the electrically commutated machine 12 comprises at least the one rotor 50. Preferably, the rotor 50 is arranged at the stator 32. Preferably, the rotor 50 is embodied as an internal rotor. Preferably, the rotor 50 comprises at least one magnet element 52 for generating a magnetic moment. Preferably, the magnet element 52 is embodied as a permanent magnet element. Preferably, the rotor 50 comprises at least one rotor shaft 54 for transmitting a torque 53 to the conveying element 30. Preferably, the electrically commutated machine 12 is embodied in a brushless fashion. Preferably, the electrically commutated machine 12 comprises at least one housing unit 56, in particular for protecting the rotor 50 and/or electronic components of the electrically commutated machine 12 (cf. FIG. 1). Preferably, the electrically commutated machine 12 comprises at least one storage unit 58 for storing a current characteristic curve 20 (cf. FIG. 4). Preferably, the electrically commutated machine 12 comprises at least one sensor element 57 for detecting the, in particular amplified and/or modulated, commutation signal 18. It is also conceivable for the electrically commutated machine 12 to comprise at least one position sensor 55 for detecting a present position and/or speed of the rotor 50.

[0027] FIG. 3 shows the method 10. The method 10 is provided for operating the electrically commutated machine 12. In at least one method step, in particular in at least one method step of overmodulation operation 14 of the electrically commutated machine 12, a precommutation angle 16 of the electrically commutated machine 12 is set depending on an efficiency of the electrically commutated machine 12. In particular, in at least one modeling step 59, in particular during a preparation phase of the method 10, a mathematical model of the electrically commutated machine 12 is created, in particular by means of an external competing unit. In particular, in the modeling step 59, in particular during the preparation phase of the method 10, at least one machine parameter is detected and/or ascertained. Preferably, the machine parameters are detected, in particular during the preparation phase of the method 10, at an operating temperature of the electrically commutated machine 12, in particular at a typical ambient temperature of a location of use of the electrically commutated machine 12. Alternatively or additionally, when ascertaining the at least one machine parameter, a temperature-dependent correction value is applied to the at least one machine parameter. In a characteristic curve ascertaining step 60, in particular during a preparation phase of the method 10, the current characteristic curve 20 is ascertained with the aid of the mathematical model of the electrically commutated machine 12, in particular by means of the external computing unit. In the characteristic curve ascertaining step 60, in particular during the preparation phase of the method 10, this involves ascertaining at least the current characteristic curve 20 of the electrically commutated machine 12 for setting the precommutation angle 16 at at least one operating temperature of the electrically commutated machine 12. In particular, in the characteristic curve ascertaining step 60, in particular during the preparation phase of the method 10, the current characteristic curve 20 is stored in the storage unit 58. It is also conceivable for the model of the electrically commutated machine 12 to be stored in the storage unit 58. Preferably, the current characteristic curve 20 is stored in the storage unit 58 in the course of mounting of the electrically commutated machine 12 and/or in the course of installation of the electrically commutated machine 12, in particular of the cooling device 28. It is also conceivable for the current characteristic curve 20 to be updated for example in the course of maintenance work, in particular in an installed state of the electrically commutated machine 12, in particular of the cooling device 28.

[0028] Preferably, a setpoint rotational speed 64 is predefined for a rotational speed closed-loop control 62 of the method 10. By way of example, the setpoint rotational speed 64 is predefined by a user and/or received and/or interrogated from an external source. Preferably, in a rotational speed processing step 68, a deviation from an actual rotational speed 66 is processed, for example by means of a PI control element of the open-loop or closed-loop control units 26, to form a setpoint torque 72. Preferably, in particular by the open-loop or closed-loop control unit 26, in a torque processing step 74, a current setpoint value 76 for a partial current flowembodied as quadrature-axis current 78of a total current flow through the stator 32 and/or for the magnitude of the total current flow through the stator 32 is ascertained from the setpoint torque 72. In particular, a maximum current 77 that is maximally achievable is predefined by means of an, in particular operating-parameter-dependent, voltage limit. Preferably, in particular by the open-loop or closed-loop control unit 26, in an operation ascertaining step 80, the current setpoint value 76 is compared with the maximum current 77. In particular, a point of intersection of the maximum current 77 with the current characteristic curve 20 marks a starting point 22 of a deviation from the current characteristic curve 20 for setting the precommutation angle 16. The operation ascertaining step 80 involves determining the starting point 22 (cf. FIG. 4) of a deviation from the current characteristic curve 20 of the electrically commutated machine 12 for setting the precommutation angle 16 depending on at least one operating parameter of the electrically commutated machine 12. In particular, the starting point 22 is determined depending on the rotational speed, in particular by the open-loop or closed-loop control unit 26. In particular, the starting point 22 is determined depending on the operating temperature, in particular by the open-loop or closed-loop control unit 26. The method 10 comprises at least one compensation step 24 for adapting the precommutation angle 16 to an ambient parameter. Preferably, in the compensation step 24, the ambient parameter is detected and/or interrogated and/or received from an external source. In particular, in the compensation step 24, a correction value for the starting point 22 is ascertained, in particular by the open-loop or closed-loop control unit 26. In particular, the correction value is ascertained, in particular by the open-loop or closed-loop control unit 26, depending on an ambient parameter embodied as a supply voltage 93.

[0029] Preferably, in the operation ascertaining step 80, in particular by the open-loop or closed-loop control unit 26, regular operation 82 is activated in the case where the current setpoint value 76 undershoots the maximum current 77. Preferably, in the operation ascertaining step 80, in particular by the open-loop or closed-loop control unit 26, overmodulation operation 14 is activated in the case where the current setpoint value 76 exceeds the maximum current 77 by less than a modulation tolerance value. Preferably, the modulation tolerance value for the current setpoint value is more than 1.5%, preferably more than 3%, particularly preferably more than 4.5%, of the maximum current 77. Preferably, the modulation tolerance value for the current setpoint value is less than 10%, preferably less than 8.5%, particularly preferably less than 6.5%, of the maximum current 77. Preferably, in particular by the open-loop or closed-loop control unit 26, in a direct-axis current ascertaining step 84, in particular in regular operation 82 and/or in overmodulation operation 14, a setpoint value for a partial current flowembodied as direct-axis current 85of the total current flow is ascertained on the basis of the current characteristic curve 20. In the direct-axis current ascertaining step 84, the precommutation angle 16 is set on the basis of at least the continuous current characteristic curve 20 of the electrically commutated machine 12. In particular, in the direct-axis current ascertaining step 84, a setpoint value for the direct-axis current 85 is ascertained depending on the current setpoint value 76, in particular by the open-loop or closed-loop control unit 26. In the direct-axis current ascertaining step 84, the precommutation angle 16 is set to a value that achieves a highest efficiency for a given operating state. Preferably, in particular by the open-loop or closed-loop control unit 26, in overmodulation operation 14 of the electrically commutated machine 12, the current setpoint value 76 is chosen to be higher than the maximum current 77, in particular for an overmodulation of the commutation signal 18, in particular for increasing a root-mean-square value of the current flow through the stator 32.

[0030] Preferably, in the operation ascertaining step 80, in particular by the open-loop or closed-loop control unit 26, field weakening operation 21 is activated in the case where the current setpoint value 76 exceeds the maximum current 77, in particular by more than the modulation tolerance value for the current setpoint value. In a direct-axis current adapting step 86 of field weakening operation 21, efficiency-dependent setting of the precommutation angle 16 is deactivated. Preferably, in particular by the open-loop or closed-loop control unit 26, in the direct-axis current adapting step 86 in field weakening operation 21, the setpoint value for the partial current flowembodied as direct-axis current 85of the total current flow is increased and/or reduced depending on the setpoint torque 72.

[0031] Preferably, the setpoint value for the direct-axis current 85 and the setpoint value for the quadrature-axis current 78 are transferred to a current closed-loop control 88. Preferably, in a transformation step 90, the setpoint values for the direct-axis current 85 and the quadrature-axis current 78 are translated into setpoint values for partial currentsembodied as phase currentsof the total current flow through the individual inductive components 34, 36, 38, in particular with the inclusion of a present position of the rotor 50. Preferably, in a converter step 92, in particular by means of the open-loop or closed-loop control unit 26, on the basis of the setpoint values for the partial currentsembodied as phase currentsof the total current flow through the individual inductive components 34, 36, 38, at least the commutation signal 18 is output. Preferably, in the converter step 92, a pulse width modulation is applied to the commutation signal 18, in particular by the open-loop or closed-loop control unit 26. In the converter step 92, in overmodulation operation 14 of the electrically commutated machine 12, at least the commutation signal 18 of the electrically commutated machine 12 is overmodulated. In particular, the switching unit 46 is overdriven by the commutation signal 18 in overmodulation operation 14. In particular, the extrema of the, in particular amplified and/or modulated, commutation signal 18 are cut off by the switching unit 46 in overmodulation operation 14. In particular, in overmodulation operation 14, a time duration during which the amplified and/or modulated commutation signal 18 assumes an extremal value is increased relative to a corresponding time duration in regular operation 82.

[0032] Preferably, the, in particular modulated, commutation signal 18 is amplified by means of the switching unit 46 and the supply voltage 93. In particular, the inductive components 34, 36, 38 are driven by the, in particular amplified and/or modulated, commutation signal 18. Preferably, a current detecting step 94 involves detecting the, in particular amplified and/or modulated, commutation signal 18, in particular as phase currents. Preferably, the detected, in particular amplified and/or modulated, commutation signal 18, in particular in the form of phase currents, is fed back to the current closed-loop control 88. In particular, the detected, in particular amplified and/or modulated, commutation signal 18, in particular in the form of phase currents, in an inverse transformation step 96 before the current closed-loop control 88, is converted into a value for the quadrature-axis current 78 and the direct-axis current 85, in particular with the inclusion of a present position of the rotor 50. Preferably, a position ascertaining step 98 involves ascertaining a present position and/or a present speed, in particular the rotational speed of the rotor 50. It is conceivable for a position- and/or speed-dependent characteristic variable to be detected, in particular by means of the position sensor 55, in at least one position detecting step 100. Preferably, a signal induced in the inductive components 34, 36, 38 is evaluated for the position ascertaining step 98. In particular, the induced signal is detected together with the, in particular amplified and/or modulated, commutation signal 18, in particular by means of the sensor element 57.

[0033] FIG. 4 shows a current diagram 102. In the current diagram 102, the quadrature-axis current 78 is plotted against the direct-axis current 85. Lines of constant torque 53 are plotted in the current diagram 102. A current limit 104 is plotted in the current diagram 102. The maximum current 77 for at least one operating state is plotted in the current diagram 102. Preferably, the current characteristic curve 20 describes a relation between the direct-axis current 85 and the quadrature-axis current 78. Preferably, the current characteristic curve 20 assigns a direct-axis current 85 to each quadrature-axis current 78. Preferably, the current characteristic curve 20 assigns a direct-axis current 85 to each quadrature-axis current 78 with a defined efficiency. Preferably, in the characteristic curve ascertaining step 60, for each quadrature-axis current 78, predefined in particular by an operating state, that direct-axis current 85 which together with the quadrature-axis current 78 achieves the highest efficiency is ascertained. Preferably, the current characteristic curve 20 is limited at least by the current limit 104. Preferably, the current limit 104 is provided by a current supply and/or a current limiting element, in particular a fuse element, of the electrically commutated machine 12. Preferably, the current characteristic curve 20 is limited by the maximum current 77 during operation of the electrically commutated machine 12. Preferably, the maximum current 77 is limited by a voltage supply and/or a voltage limiting element, in particular a fuse element, of the electrically commutated machine 12. In particular, the maximum current 77 is limited by an, in particular rotational-speed-dependent, induced signal. In particular, the maximum current 77 is limited by an impedance, in particular a temperature-dependent electrical resistance, of the stator 32. Preferably, the point of intersection of the maximum current 77 with the current characteristic curve 20 predefines the starting point 22. In particular, the starting point 22 marks a transition from regular operation 82 and/or overmodulation operation 14 to field weakening operation 21.