Method for operating an electric machine, device for operating an electric machine, electric machine

Abstract

The invention relates to a method for operating an electric machine (1), wherein the machine (1) has a rotor (2) which is mounted so as to be rotatable and at least one motor winding (5), wherein a target rotational speed (N_Soll) is specified for the rotor (2), and wherein the motor winding (5) is loaded with a motor current such that an actual rotational speed (N_Ist) of the rotor (2) corresponds to the target rotational speed (N_Soll). It is provided that a target phase-lag angle (Phi_Schlepp_Soll) is specified for a current vector (13), which describes the motor current with reference to a coordinate system which is fixed on the rotor, wherein the target phase-lag angle (Phi_Schlepp_Soll) has an angle value from an angle interval of from 0° to 90°, and wherein a current amplitude (I_Abs) of the motor current is set such that an actual phase-lag angle (Phi_Schlepp_Ist) of the current vector (13) corresponds to the target phase-lag angle (Phi_Schlepp_Soll).

Description

Technical Field

[0001] The present invention relates to a method for operating an electric motor, wherein the machine has a rotatably supported rotor and at least one motor winding, wherein a target speed is predetermined for the rotor, and wherein the motor winding is loaded with motor current such that the actual speed of the rotor corresponds to the target speed.

[0002] Furthermore, the present invention relates to a device with a controller for operating a motor.

[0003] Furthermore, the present invention relates to a motor incorporating such a device. Background Technology

[0004] An electric motor typically has a rotatably supported rotor and at least one energized motor winding. The motor winding is, for example, a stator winding fixed to a housing, which is distributed around the rotor. During motor operation, a target speed is typically pre-defined for the rotor, and the motor winding is loaded with motor current so that the actual speed of the rotor corresponds to the target speed. That is, speed regulation is performed. Such methods are known, for example, from publication DE 10 2008 036 483 A1. In previously known methods, cascaded regulation systems consisting of field-oriented regulation and superimposed speed regulation are frequently used. Summary of the Invention

[0005] The method according to the invention, possessing the features of claim 1, has the advantage that it can particularly stably control high torque fluctuations, especially at low speeds. To this end, the invention specifies that a target hysteresis angle is pre-given for the current vector, which describes the motor current with reference to a coordinate system fixed on the rotor. The target hysteresis angle has angle values ​​from an angle range of 0° to 90°, and the current amplitude of the motor current is set such that the actual hysteresis angle of the current vector corresponds to the target hysteresis angle. That is, an angle value from an angle range of 0° to 90° is pre-given as the target hysteresis angle, and the current amplitude is set or changed such that the current vector has the target hysteresis angle as the actual hysteresis angle. Within the scope of the disclosure, the motor current should be understood as the entirety of the sinusoidal phase current flowing through the motor windings. Because the coordinate system is fixed on the rotor, it rotates with the rotor. Such a coordinate system is also referred to as a dq diagram. Here, the first coordinate axis of the coordinate system describes the current component of the forming field of the motor current. This first coordinate axis is oriented parallel to the magnetic field generated by the magnetic device of the rotor. The second coordinate axis of the coordinate system describes the current component of the motor current that forms the torque. This second coordinate axis is oriented perpendicularly to the magnetic field. Within the scope of the disclosure, the hysteresis angle is understood to be the angle by which the current vector lies in front of the first coordinate axis in the direction of rotor rotation. In this respect, the hysteresis angle corresponds to the difference between the current angle of the motor current on one hand and the rotation angle of the rotor on the other. According to the invention, the target hysteresis angle has an angle value from an angle range of 0° to 90°. If the actual hysteresis angle of the current vector corresponds to the predetermined target hysteresis angle, then the current vector lies in quadrant 1 of the coordinate system fixed on the rotor in the positive direction of rotor rotation. If the actual hysteresis angle of the current vector corresponds to the predetermined target hysteresis angle, then the current vector lies in quadrant 4 of the coordinate system fixed on the rotor in the negative direction of rotor rotation. This has the advantage that the motor remains relatively stable at a constant speed even in the presence of torque fluctuations. If the torque load of the motor changes, the current vector is set in quadrant 1 or quadrant 4 such that there is a balance between the motor output torque and the load torque. Thus, the orientation of the current vector is temporarily changed while the current amplitude remains constant. Because the current amplitude is set in such a way according to the invention that the actual lag angle corresponds to the target lag angle, the current amplitude is adapted so that the actual lag angle readjusts to the target lag angle. Here, the rotor speed and the frequency of the phase current are always at least substantially constant. Preferably, the motor is a permanent magnet excited synchronous motor. Preferably, the current amplitude is set by adjustment.

[0006] According to a preferred embodiment, when an actual lag angle exceeds the target lag angle, the current amplitude of the motor current is increased, and / or when an actual lag angle is lower than the target lag angle, the current amplitude of the motor current is decreased. This method promotes the adaptation of the actual lag angle to a predetermined target lag angle during motor operation.

[0007] According to a preferred embodiment, the target hysteresis angle has an angle value ranging from 20° to 80°. The closer the angle value is to 90°, the smaller the current amplitude required to achieve the target speed. In this respect, a target hysteresis angle with a high angle value is advantageous in principle. However, the closer the angle value is to 90°, the smaller the gap, which allows the motor to respond to torque fluctuations by temporarily changing the actual hysteresis angle in quadrant 1 or quadrant 4. In this respect, a target hysteresis angle with an angle value ranging from 20° to 80° represents an advantageous compromise. Preferably, the target hysteresis angle has an angle value ranging from 30° to 70°, and particularly preferably from 55° to 65°.

[0008] Preferably, the target hysteresis angle is predetermined based on the load torque fluctuation. That is, the angle value of the target hysteresis angle is selected based on the load torque fluctuation. Preferably, the target hysteresis angle is predetermined based on the calculated load torque fluctuation and / or the expected load torque fluctuation. For example, when the calculated or expected load torque fluctuation is small, a target hysteresis angle with a large angle value is predetermined, and when the calculated or expected load torque fluctuation is high, a target hysteresis angle with a small angle value is predetermined.

[0009] Preferably, the target lag angle is predetermined based on the target rotational speed. That is, the angle value of the target lag angle is selected according to the target rotational speed. Therefore, it is possible to achieve precise adaptation of the target lag angle to different operating states of the motor, thereby enabling exceptionally stable motor operation.

[0010] According to an alternative implementation, the target lag angle is preferably predetermined independent of the target speed. That is, the same target lag angle is always predetermined for each target speed. This approach results in lower costs in terms of regulation technology.

[0011] According to a preferred embodiment, a threshold speed is predetermined, wherein the motor current amplitude is set such that the actual lag angle corresponds to the target lag angle only when a target speed below the threshold speed is predetermined. That is, the setting of the current amplitude according to the invention is stopped when a target speed exceeding the threshold speed is predetermined. Preferably, the predetermined setting of the target lag angle is also stopped when a target speed exceeding the threshold speed is predetermined. As mentioned earlier, the method according to the invention results in stable motor operation, particularly at low speeds. However, alternative methods for operating the motor at higher speeds may be advantageous. Preferably, when a target speed exceeding the threshold speed is predetermined, the motor is operated by means of a cascaded regulating system having field-oriented regulation with superimposed speed regulation.

[0012] Preferably, a speed from a speed range of 20 rpm to 200 rpm, particularly preferably from a speed range of 40 rpm to 200 rpm, is given in advance as a threshold speed.

[0013] Preferably, the current amplitude is set such that the actual hysteresis angle corresponds to the target hysteresis angle by means of field-oriented adjustment. This achieves precise setting of the current amplitude. Preferably, the target current amplitude is predetermined based on the deviation between the actual hysteresis angle and the target hysteresis angle. Preferably, then within the range of field-oriented adjustment, 0 is used as the target parameter for the current component used to form torque, the target current amplitude is used as the target parameter for the current component used to form the field, and the target current angle of the coordinate system with the reference fixed on the stator for the motor current is used as the guide angle. As explained above, when a target speed exceeding a threshold speed is predetermined, the motor is preferably operated by means of an adjustment system with a field-oriented regulator. In this respect, setting or adjusting the current amplitude by means of field-oriented adjustment is particularly advantageous because existing adjustment structures can be used.

[0014] The apparatus according to the invention for operating an electric motor having a rotatably supported rotor and at least one motor winding is characterized by a controller, specifically configured to execute the method according to the invention in compliant use. If the controller is used compliantly, then the method according to the invention is thus executed by or within the controller. Consequently, the advantages already mentioned are also obtained. Other preferred features and combinations thereof are derived from the description and from the claims.

[0015] The motor according to the invention has a rotatably supported rotor and at least one motor winding, and is characterized by having the features of claim 11 in relation to the device according to the invention. Thus, the advantages already mentioned are also obtained. Other preferred features and combinations thereof are derived from the description and from the claims. Attached Figure Description

[0016] The invention is explained in more detail below with the aid of the accompanying drawings. Wherein: Figure 1 The motor is shown; Figure 2 Multiple current vectors in a coordinate system fixed on the rotor are shown, and Figure 3 A method for operating a motor is shown. Detailed Implementation

[0017] Figure 1 The simplified diagram shows motor 1. Here, machine 1 is the pump motor 1 of a fluid pump, which is not shown further. In this respect, machine 1 is designed for operating the pump element of a fluid pump. However, the teachings of the disclosure can also be applied to motors with other applications.

[0018] The motor 1 has a rotor 2 rotatably supported in a housing (not shown). Here, the machine 1 is a synchronous motor 1 excited by a permanent magnet. Accordingly, the rotor 2 has a permanent magnet device 3 with at least one permanent magnet 4.

[0019] In addition, the machine 1 has a motor winding 5. Here, the motor winding 5 is constructed as a stator winding 5 and has three phases U, V and W, which are distributed around the rotor 2 so that the rotor 2 can rotate by energizing phases U, V and W with sinusoidal phase currents.

[0020] Motor 1 is equipped with an energy storage device 6. Phases U, V, and W are electrically connected to the energy storage device 6 via power electronics 7 having multiple switching elements.

[0021] Furthermore, the motor 1 has a device 8 for operating the machine 1. The device 8 has a controller 9, which is configured to operate or switch the switching elements of the power electronics 7.

[0022] The motor winding 5 is equipped with a sensor device 10, which has at least one current sensor 20 and is configured to detect the actual phase current flowing through phases U, V, and W. The sensor device 10 is connected to the controller 9 in terms of communication technology to provide the controller 9 with the detected actual phase current.

[0023] Rotor 2 is equipped with a rotation angle sensor 21. The rotation angle sensor 21 is configured to detect the actual rotation angle of rotor 2. Specifically, the rotation angle sensor 21 is configured to detect the mechanical actual rotation angle Phi_Rot_mech_Ist of rotor 2. The rotation angle sensor 21 is connected to controller 9 in a communication manner to provide the controller 9 with the detected actual rotation angle. Controller 9 is configured to determine the electrical actual rotation angle Phi_Rot_el_Ist of rotor 2 based on the mechanical actual rotation angle Phi_Rot_mech_Ist and the number of pole pairs.

[0024] Figure 2 A coordinate system fixed to the rotor, i.e., a coordinate system rotating together with the rotor 2, is shown. This coordinate system has a first coordinate axis 11 and a second coordinate axis 12. The first coordinate axis 11 is oriented parallel to the magnetic field generated by the permanent magnet device 3. The second coordinate axis 12 is oriented perpendicular to the magnetic field generated by the permanent magnet device 3. This type of coordinate system is also referred to as a dq diagram.

[0025] A first current vector 13 is shown in the coordinate system. This first current vector 13 describes a specific first motor current, that is, a specific combination of phase currents flowing through phases U, V, and W. Here, the length of the current vector 13 describes the current amplitude of the first motor current. The angle between the first coordinate axis 11 on one side and the first current vector 13 on the other side is the hysteresis angle of the first current vector 13. This hysteresis angle corresponds to the difference between the rotation angle of the rotor 2 on one side and the current angle of the first motor current on the other side.

[0026] Furthermore, a second current vector 14 is shown in the coordinate system. This second current vector 14 describes a specific second motor current. (As shown by...) Figure 2 As is obvious, the value of the first current vector 13 on the second coordinate axis 12 corresponds to the value of the second current vector 14 on the second coordinate axis 12. In this respect, when the motor winding 5 is loaded with the first motor current, the motor 1 produces the same motor output torque M1 as when the motor winding is loaded with the second motor current. However, the second current vector 14 differs from the first current vector 13 in its length and its hysteresis angle.

[0027] See below for reference Figure 3 The advantageous methods for operating machine 1 are explained in more detail.

[0028] In the first step S1, the controller 9 pre-sets a target speed N_Soll for the rotor 2. The target speed N_Soll is determined by... Figure 3 The method described is to set, or rather should set, the motor current as a target parameter, which causes the rotor 2 to rotate at a target speed N_Soll.

[0029] In the second step S2, the controller 9 compares the target rotational speed N_Soll with a pre-given threshold rotational speed. According to... Figure 3 In the embodiment described herein, a rotational speed of 100 rpm is pre-defined as a threshold rotational speed.

[0030] If the comparison shows that the target speed N_Soll exceeds the threshold speed, then refer to the third step S3. In the third step S3, the controller 9 operates the machine 1 by means of a cascaded adjustment system, which has torque adjustment with superimposed speed adjustment, and in particular field-oriented adjustment.

[0031] However, if the comparison shows that the target speed N_Soll is lower than the threshold speed, then refer to step S4. In step S4, the controller 9 calculates the target current angle Phi_I_el_Soll based on the target speed N_Soll as the motor current, referencing a coordinate system fixed on the stator. Here, the controller 9 calculates the current target current angle Phi_I_el_Soll by accumulating the angle value based on the target speed N_Soll. Accordingly, a target current angle Phi_I_el_Soll with a continuous trend or "angle ramp function" is obtained.

[0032] Furthermore, the target current angle Phi_I_el_Soll is limited in step S4. To this end, a threshold angle difference of 90° is predetermined, and the target current angle Phi_I_el_Soll is limited such that the angle difference between the target current angle Phi_I_el_Soll and the actual rotation angle Phi_Rot_el_Ist of rotor 2 is maximized to the threshold angle difference. That is, the target current angle Phi_I_el_Soll is first calculated based on the target rotational speed N_Soll. If the deviation between the target current angle and the actual rotation angle Phi_Rot_el_Ist is greater than 90°, the initially calculated target current angle Phi_I_el_Soll is reduced such that the angle difference with the actual rotation angle Phi_Rot_el_Ist is maximized to 90°. In the positive rotation direction of rotor 2, this prevents the target current angle Phi_I_el_Soll from falling outside quadrant 1 of the dq diagram. Accordingly, in the case of the rotor 2 rotating in the negative direction, the target current angle Phi_I_el_Soll is prevented from falling outside quadrant 4 of the dq diagram. This prevents motor 1 from losing synchronization.

[0033] In another embodiment, in step S1, the target rotational position of rotor 2 is predetermined instead of the target rotational speed N_Soll. In this case, the target rotational position is then directly converted into the target current angle Phi_I_el_Soll in step S4. Preferably, the target current angle Phi_I_el_Soll is also limited in this case, as explained previously.

[0034] In the fifth step S5, the controller 9 calculates the actual hysteresis angle Phi_Schlepp_Ist. Here, the controller 9 calculates the actual hysteresis angle Phi_Schlepp_Ist by constructing the difference between the target current angle Phi_I_el_Soll and the actual rotation angle Phi_Rot_el_Ist of the rotor 2.

[0035] In step S6, controller 9 pre-determines the target hysteresis angle Phi_Schlepp_Soll. Here, controller 9 pre-determines the target hysteresis angle Phi_Schlepp_Soll with a value of 60°. The target hysteresis angle Phi_Schlepp_Soll is determined by... Figure 3 The method shown is to set, or rather should set, the motor current because of the target parameter, the current vector of which has a target hysteresis angle Phi_Schlepp_Soll as the hysteresis angle.

[0036] In the seventh step S7, the controller 9 calculates the difference between the target hysteresis angle Phi_Schlepp_Soll and the actual hysteresis angle Phi_Schlepp_Ist as the adjustment difference. In this respect, the controller 9 pre-determines the target hysteresis angle Phi_Schlepp_Soll as a reference variable.

[0037] In step S8, controller 9 calculates the target current amplitude I_Abs_Soll based on the difference obtained in step S7, which is the motor current. By calculating the target current amplitude I_Abs_Soll, controller 9 facilitates the setting of the target current amplitude I_Abs_Soll, thereby setting or adjusting the target hysteresis angle Phi_Schlepp_Soll to the actual hysteresis angle Phi_Schlepp_Ist.

[0038] In the ninth step S9, the controller 9 manipulates the power electronic device 7, or the switching element of the power electronic device 7, such that the actual current vector of the motor current fixed on the stator (the actual current vector is represented by the actual current amplitude I_Abs_Ist and the actual current angle Phi_I_el_Ist) corresponds to the target current vector fixed on the stator, which is represented by the target current amplitude I_Abs_Soll obtained in step S8 and the target current angle Phi_I_el_Soll obtained in step S4.

[0039] Here, the controller 9 pre-determines the target current amplitude I_Abs_Soll and the target current angle Phi_I_el_Soll in step S9, and adjusts the actual current amplitude I_Abs_Ist and the actual current angle Phi_I_el_Ist by means of field orientation adjustment. Here, the target current amplitude I_Abs_Soll is pre-determined as the target parameter for the current component used to form the field. 0 is pre-determined as the target parameter for the current component used to form the torque. Furthermore, the target current angle Phi_I_el_Soll is pre-determined as the guide angle.

[0040] According to another embodiment, voltage regulation is performed in step S9. In this case, the target voltage amplitude U_Abs_Soll is then obtained in step S8. Furthermore, the target voltage angle Phi_U_el_Soll is obtained in step S4. Then, in step S9, the controller 9 manipulates the power electronics 7, or the switching element of the power electronics 7, such that the actual voltage vector fixed on the stator, represented by the actual voltage amplitude U_Abs_Ist and the actual voltage angle Phi_U_el_Ist, corresponds to the target voltage vector fixed on the stator, represented by the target voltage amplitude U_Abs_Soll and the target voltage angle Phi_U_el_Soll. That is, in step S9, the voltage characteristic parameter replaces the current characteristic parameter as the basis for regulation.

[0041] In the following text, see references Figure 2The various aspects of the method are explained in more detail again. As mentioned earlier, when the motor winding 5 is loaded with a first motor current, the same motor output torque M1 is generated as when the motor winding 5 is loaded with a second motor current. Hereinafter, it is assumed that this motor output torque M1 is sufficient to rotate the rotor 2 at a predetermined target speed N_Soll. Furthermore, it is assumed that the hysteresis angle of the first current vector 13 is a predetermined target hysteresis angle Phi_Schlepp_Soll. Finally, it is assumed that the second current vector 14 describes the motor current currently flowing through the motor winding 5. Therefore, the hysteresis angle of the second current vector 14 corresponds to the actual hysteresis angle Phi_Schlepp_Ist.

[0042] Based on this situation, in step S7, the controller 9 calculates the difference between the actual hysteresis angle Phi_Schlepp_Ist and the target hysteresis angle Phi_Schlepp_Soll. Because the actual hysteresis angle Phi_Schlepp_Ist is less than the target hysteresis angle Phi_Schlepp_Soll, the controller 9 calculates the target current amplitude I_Abs_Soll in step S8. This target current amplitude is less than the current amplitude described by the second current vector 14, that is, less than the current amplitude described by the first current vector 13.

[0043] Finally, the controller 9 sets the target current amplitude I_Abs_Soll as the actual current amplitude I_Abs_Ist according to method step S9. Since the machine 1 remains stable in quadrant 1 of the coordinate system fixed to the rotor in the positive rotation direction, or in quadrant 4 of the coordinate system fixed to the rotor in the negative rotation direction, the hysteresis angle of the first current vector 13 is automatically set to the actual hysteresis angle Phi_Schlepp_Ist by setting the current amplitude described by the first current vector 13 as the actual current amplitude I_Abs_Ist. Here, the rotational speed of the rotor 2 and the frequency of the phase current remain at least substantially constant because the target current angle Phi_I_el_Soll varies with a constant angular velocity relative to the coordinate system fixed to the stator according to the target rotational speed N_Soll.

Claims

1. A method for operating an electric motor, wherein, The machine (1) has a rotatably supported rotor (2) and at least one motor winding (5), wherein a target speed (N_Soll) is given to the rotor (2) in advance, and wherein the motor winding (5) is loaded with motor current such that the actual speed (N_Ist) of the rotor (2) corresponds to the target speed (N_Soll). The feature is that a target hysteresis angle (Phi_Schlepp_Soll) is given in advance for the current vector (13), the current vector describing the motor current with reference to a coordinate system fixed on the rotor, wherein the target hysteresis angle (Phi_Schlepp_Soll) has an angle value from an angle range of 0° to 90°, and wherein the current amplitude (I_Abs) of the motor current is set such that the actual hysteresis angle (Phi_Schlepp_Ist) of the current vector (13) corresponds to the target hysteresis angle (Phi_Schlepp_Soll).

2. The method according to claim 1, characterized in that, If there is an actual hysteresis angle (Phi_Schlepp_Ist) that exceeds the target hysteresis angle (Phi_Schlepp_Soll), increase the current amplitude (I_Abs) of the motor current, and / or if there is an actual hysteresis angle (Phi_Schlepp_Ist) that is lower than the target hysteresis angle (Phi_Schlepp_Soll), decrease the current amplitude (I_Abs) of the motor current.

3. The method according to claim 1 or 2, characterized in that, The target hysteresis angle (Phi_Schlepp_Soll) has angle values ​​from an angle range of 20° to 80°.

4. The method according to claim 3, characterized in that, The target hysteresis angle (Phi_Schlepp_Soll) has angle values ​​from an angle range of 30° to 70°.

5. The method according to claim 3, characterized in that, The target hysteresis angle (Phi_Schlepp_Soll) has angle values ​​from an angle range of 55° to 65°.

6. The method according to claim 1 or 2, characterized in that, The target hysteresis angle (Phi_Schlepp_Soll) is pre-defined based on the load torque fluctuation.

7. The method according to claim 1 or 2, characterized in that, The target lag angle (Phi_Schlepp_Soll) is predetermined based on the target rotational speed (N_Soll).

8. The method according to claim 1 or 2, characterized in that, The target hysteresis angle (Phi_Schlepp_Soll) is given in advance without relying on the target rotational speed (N_Soll).

9. The method according to claim 1 or 2, characterized in that, A threshold speed is given in advance, wherein the current amplitude (I_Abs) of the motor current is set only when a target speed (N_Soll) lower than the threshold speed is given in advance, such that the actual hysteresis angle (Phi_Schlepp_Ist) corresponds to the target hysteresis angle (Phi_Schlepp_Soll).

10. The method according to claim 9, characterized in that, The speed range from 20 rpm to 200 rpm will be predetermined as the threshold speed.

11. The method according to claim 10, characterized in that, In the future, the speed range from 40 rpm to 200 rpm will be predetermined as the threshold speed.

12. The method according to claim 1 or 2, characterized in that, The current amplitude (I_Abs) is set by adjusting the field orientation so that the actual hysteresis angle (Phi_Schlepp_Ist) corresponds to the target hysteresis angle (Phi_Schlepp_Soll).

13. Equipment for operating an electric motor, wherein, The machine (1) has a rotor (2) rotatably supported and at least one motor winding (5), characterized in that the device (8) has a controller (9) configured to perform the method according to any one of claims 1 to 12 in accordance with prescribed use.

14. An electric motor having a rotatably supported rotor (2) and at least one motor winding (5), characterized in that The device (8) according to claim 13.

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