Motor

Abstract

The present invention relates to an electric motor, in particular a claw-pole motor. The electric motor has a stator and a rotor. The electric motor also has a control unit, in particular operatively connected to the stator. The control unit is configured to control the electric motor to generate an excitation field and a rotating magnetic field. The electric motor has an H-bridge connected to the rotor, and the H-bridge is used to generate an excitation field. According to the present invention, the control unit is configured to detect a fault of a semiconductor switch of an inverter and generate a fault signal representing the fault. The control unit is preferably configured to reverse the direction of the excitation current of the electric motor according to the fault signal. The control unit is configured to change the phase position of the stator current according to the fault signal and thereby change the phase position of the control of the stator to generate a rotating field of the electric motor.

Description

Technical Field

[0001] The present invention relates to an electric motor, in particular a synchronous motor or a claw-pole motor. The electric motor has a stator and a rotor. The electric motor also has a control unit, in particular operatively connected to the stator, and the control unit is configured to control the electric motor to generate an excitation field and a rotating magnetic field. The electric motor has an H-bridge connected to the rotor, and the H-bridge is used to generate an excitation field. Background Art

[0002] DE 10 2017 101 069 A1 discloses a control unit for an electric machine, which is designed to inhibit a cycling state in an H-bridge as a function of a defective semiconductor switch of the H-bridge. Summary of the invention

[0003] According to the invention, the control unit is designed to detect a fault of a semiconductor switch of the inverter and to generate a fault signal representing the fault. The control unit is preferably designed to reverse the direction of the field current of the motor as a function of the fault signal. The control unit is designed to change the phase position of the stator current and thus the phase position of the stator for generating a rotating field of the motor as a function of the fault signal.

[0004] Thus, the electric machine can advantageously continue to operate in motor mode in emergency mode with a changed phase position and with a reversed excitation current compared to normal operation, and thus with a magnetic field that is aligned in the opposite direction and thus with a reversed polarity. It has been found that, in the event of a fault in a semiconductor switch of an inverter in a claw-pole electric machine, the excitation current can be conducted in the opposite, especially reversed direction compared to normal motor mode, depending on the fault, so that the excitation field and thus the magnetic poles of the excitation field are interchanged for the continued operation of the electric machine in motor mode. In the event of a fault, the magnetic north pole of the excitation field in normal operation becomes the magnetic south pole in the case of a reversed excitation current. The direction of rotation (especially the electrical direction of rotation) of the stator field and the changed spatial position of the rotor field in the stator, which is caused by the reversed polarity of the excitation field, and which energizes the rotor, operate independently of each other after current commutation when a semiconductor switch fails, which causes the now reversed rotor magnetic poles to repel each other in the rotating rotor field and thus causes the rotor to brake. When the north pole of the excitation field in the rotor follows the south pole of the rotating stator field and the north pole of the rotating stator field repels the north pole of the excitation field, this correlation is reversed to repulsion in the reversed excitation field, which produces a braking torque. The correspondingly changed phase position, in particular the electrical phase angle of the stator field, leads to the fact that the rotor field and the stator field operate in a relative manner in the reversed excitation field, so that the braking torque becomes effective only during the magnetic field commutation of the excitation field. After the phase shift of the rotating stator field, the mutually opposite magnetic poles of the rotor field and the stator field are again in a mutual magnetic attraction interaction, so that before the failure of the semiconductor switch, the relative magnetic state between the stator field and the excitation field is reestablished with the magnetic poles reversed for this purpose. Therefore, after the phase shift, the magnetic field of the stator is spatially moved, in particular reversed, in the direction of rotation of the rotor. Preferably, the control unit is configured to maintain the control mode for controlling the stator when the phase position is changed.

[0005] For example, the torque and the rotational speed of the rotor output by the electric machine are predetermined by the control mode, in particular the PWM mode.

[0006] The stator current is preferably designed to be periodic, for example sinusoidal.

[0007] In a preferred embodiment, the control unit is designed to invert the phase position of the electrical actuation for generating the rotating field, in particular compared to normal operation with intact semiconductor switches. Preferably, the control unit is designed to invert the phase such that the main directional component of the phase position (in particular of the phase pointer) points in the opposite direction after the inversion. Advantageously, the phase inversion leads to a polarity reversal of the magnetic stator field in the direction of rotation of the rotor and thus to a correct synchronous operation between the stator field and the excitation field, wherein the excitation field is generated by energizing the rotor.

[0008] In a preferred embodiment, the displacement angle of the electrically controlled phase position is between 160 degrees and 200 degrees, more preferably 180 degrees, and the displacement angle is generated by the control unit in response to the fault signal.

[0009] Preferably, the electric machine has a rotor position sensor, which is designed to detect the rotor position of the rotor and generate a rotor position signal representing the rotor position. Preferably, the control unit is designed to change the phase position of the actuation of the stator as a function of the rotor position signal. The rotor position sensor is, for example, an AMR sensor (AMR=Anisotrope-Magneto-Resistive) or a GMR sensor (GMR=Giant-Magneto-Resistive).

[0010] In a preferred embodiment, the semiconductor switch bridge is a semiconductor switch full bridge, which includes two semiconductor switch half bridges. The half bridge preferably has a high-side semiconductor switch and a low-side semiconductor switch. For example, the semiconductor switches are formed by field effect transistors or IGBTs (IGBT=insulated gate bipolar transistors, Insulated-Gate-Bipolar-Transistor). The field effect transistor is, for example, a MOS-FET-transistor (MOS=metal oxide semiconductor, Metal-Oxide-Semiconductor) or a MIS-FET-transistor (MIS=metal insulator semiconductor, Metal-Insulator-Semiconductor).

[0011] In a preferred embodiment, the control unit is designed to perform a phase shift after the stator current has decayed, in particular during a zero crossing of the stator current. Thus, preferably, a stator current is regenerated in the stator coil winding after the stator current has decayed, which has a reversed phase and thus a reversed direction to reverse the stator poles.

[0012] In a preferred embodiment, the control unit is designed to allow the field current to decay, preferably before the current commutation or before the phase shift. Preferably, the control unit is designed to perform the current commutation of the field current stepwise, preferably (especially approximately) linearly decreasing. In a further embodiment, the control unit is designed to perform the current commutation of the field current exponentially decreasing. Advantageously, the field current can thereby be reduced rapidly.

[0013] In a preferred embodiment, the control unit is designed to carry out a phase shift after the excitation current has decayed. Advantageously, the current commutation can thus be carried out quickly, so that the smallest possible braking torque can occur during the phase change.

[0014] In a preferred embodiment, the control unit is designed to actuate the H-bridge to switch the polarity of the field coil during the current reduction interval. This advantageously enables a rapid elimination of the field to be performed for accelerated current commutation.

[0015] In a preferred embodiment, the control unit is designed to reduce, preferably allow a decay of, the stator current as a function of the fault signal. Further preferably, the control unit is designed to interrupt the stator current in the region of the current commutation of the field current. Advantageously, the field current can be eliminated quickly in this way.

[0016] In a preferred embodiment, the electric machine has a current sensor connected to the control unit. The current sensor is designed to detect the current direction or additionally the current intensity of the field current and to generate a current signal, which represents the current direction or additionally the current intensity of the field current. Advantageously, the beginning of current commutation in the field coil can thus be detected in good time before the braking torque can be fully built up.

[0017] In a further embodiment, the control unit is designed to detect the current direction of the excitation current as a function of the switching sequence of the semiconductor switches of the semiconductor switch full bridge.

[0018] In a further embodiment, the control unit is designed to detect the current direction of the excitation current as a function of a torque drop of the electric machine. The torque drop can be detected, for example, as a function of a rotor position signal generated by a rotor position sensor.

[0019] In a preferred embodiment, the control unit is designed to interrupt the activation of a phase as a function of the fault signal, in particular during a predetermined time interval. Advantageously, a phase reversal can thus be initiated quickly.

[0020] The invention also relates to a method for operating a claw-pole motor. In the method, a fault of a semiconductor switch, which generates an excitation current for the motor, is detected. Furthermore, in the method, a fault signal representing the fault is generated and, as a function of the fault signal, the phase position of the electrical generation of the excitation current is shifted by a predetermined displacement angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention is now described below with reference to the drawings and further exemplary embodiments. Further advantageous embodiments result from the combination of the features described in the dependent claims and in the drawings.

[0022] Figure 1 An exemplary embodiment for an electric machine having a control unit which is designed to carry out a phase reversal as a function of a fault in a semiconductor switch;

[0023] Figure 2 The diagram shows that Figure 1 The control unit shown is capable of operating according to the diagram;

[0024] Figure 3 Shown for Figure 1 An embodiment of the position of the magnetic field of the electric machine in normal motor operation is shown in FIG.

[0025] Figure 4 Shown for Figure 1 An exemplary embodiment of the position of the magnetic field of an electric machine in the event of a fault in motor operation and in the event of a magnetic field reversal of the excitation field is shown in;

[0026] Figure 5 Shown for Figure 1 An exemplary embodiment of the position of the magnetic field of an electric machine in the event of a fault in motor operation after a polarity reversal of the excitation field and a magnetic displacement, in particular a magnetic reversal of the rotating stator field, is shown in FIG. DETAILED DESCRIPTION

[0027] Figure 1An embodiment for an electric motor 1 is schematically shown. The electric motor 1 has a stator 2 and a rotor 3. In this embodiment, the electric motor 1 is a separately excited electric motor, in particular a claw-pole motor. For this purpose, the rotor 3 has a rotor coil 4, which is configured to generate a magnetic field, in particular an excitation field. In this embodiment, the stator 2 has three stator coils 5, 50 and 51, which are configured to generate a rotating magnetic field to cause the rotor 3 to rotate. In other embodiments, the stator can have more than three, in particular a multiple of three, stator coils. Arrow 6 represents the direction of rotation of the stator field, and arrow 7 represents the direction of the magnetic moment associated therewith, which acts on the rotor 3 and is consistent with the direction of rotation of the stator field when the rotor is energized in an H-bridge and fault-free state.

[0028] The electric machine 1 also has a power output stage 40 and a control unit, in particular a processing unit 9. The power output stage 40 is connected to the stator 2 via an electrical connection 49 on the output side and is configured to energize the stator coils of the stator 2 to generate a rotating magnetic field. For this purpose, the power output stage 40 has a B6 bridge, which includes three semiconductor switch half bridges 46, 47 and 48.

[0029] The motor 1 also has a power output stage 8 to generate an excitation field, and the power output stage is configured as a semiconductor switch full bridge. In this embodiment, the power output stage 8 is connected to the rotor 3 by means of an electrical connection 14, and is electrically connected there to the rotor coil 4, for example, through a slip ring. The power output stage 8 is configured to energize the rotor coil 4 of the rotor 3 to generate an excitation field. For this purpose, the power output stage 8 has a semiconductor switch full bridge (also called an H bridge). The semiconductor switch full bridge has two semiconductor switch half bridges, wherein one half bridge has a high-side semiconductor switch 17 and a low-side semiconductor switch 18, and a half bridge complementary thereto has a high-side semiconductor switch 15 and a low-side semiconductor switch 16. The power output stage 8 is connected to the processing unit 9 on the input side through an electrical connection 39. The processing unit 9 is configured, for example, as a microprocessor, a microcontroller, an ASIC (ASIC = Application-Specific-Integrated-Circuit) or an FPGA (FPGA = Field-Programmable-Gate-Array).

[0030] The processing unit 9 is configured to generate a control pattern to control the power output stages 8 and 40, in particular to control the semiconductor switches of the power output stages, and to output the control pattern on the output side. To this end, the processing unit 9 has a pulse width modulator 10, which is configured to generate a control signal to control the stator coils 5, 50 and 51. The power output stage 40 can receive a control signal from the processing unit 9 via a connecting line 38, and the control signal is used to control the stator coils 5, 50 and 51. The connecting line 38 is configured to be multi-channel and can be formed, for example, by a data bus. The processing unit 9 also has a pulse width modulator 54 to control the H-bridge 8. The pulse width modulator 54 is configured to modulate the excitation current to change the power of the excitation coil 4. The processing unit 9 is configured, for example, to generate a control pattern for the H-bridge 8 and thus for the excitation coil 4 according to a fault signal, the control pattern being pulse width modulated for establishing or eliminating excitation and for current commutation.

[0031] In this embodiment, the processing unit 9 also has a phase shift unit 11, which is connected to the pulse width modulator 10 on the output side and is constructed to generate a fault signal based on the current signal and output the fault signal to the pulse width modulator 10 on the output side to generate a phase-shifted control signal. The current signal is received on the input side via the connecting pipeline 12.

[0032] The electric machine 1 also has a current sensor 13, which is designed as a shunt resistor in this exemplary embodiment and is arranged and designed to detect the current flowing in the rotor coil of the rotor 3 and to generate a current signal representing the current. The current sensor 13 is connected on the output side to the processing unit 9 via a connecting line 12 and there to the phase shift unit 11.

[0033] The electric machine 1 also has a rotor position sensor 52 which is connected to the processing unit 9 and is designed to detect a rotor position of the rotor 3 and to generate a rotor position signal which represents the rotor position.

[0034] Independently of or in addition to the current sensor 13 , the processing unit 9 is designed to determine a torque drop of the electric machine as a function of the rotor position signal and to generate an error signal as a function of the torque drop.

[0035] The processing unit 9 also has a timer 19, which is configured to generate and output a clock signal representing a clock cycle on the output side. The dashed arrow 41 shows the magnetic action direction of the magnetic moment, which is opposite to the rotation direction 6 of the rotating field, and is generated by the excitation field, and the magnetic action direction is caused by the repulsion of the same polarity of the excitation field and the stator field after the current commutation in the excitation coil. The pulse width modulator 10 is configured to generate a control signal for controlling the power output stage 8 according to the fault signal, in particular to energize the rotor coil 4 in the reversed current direction according to the clock signal. The pulse width modulator 10 is configured to generate a phase-shifted control signal with an inverted phase position according to the fault signal, which is used to control the power output stage 40, in particular to energize the stator 2 according to the clock signal. As a result, the motor 1 can continue to operate after the current commutation with a short torque drop during the current commutation in the excitation coil.

[0036] Figure 2 An exemplary embodiment is shown for diagram 20 . Diagram 20 shows the torque profile of the torque delivered by the electric machine 1 in the event of a fault and the current profiles of the field current and the stator current as a function of the phase shift, in particular the phase reversal.

[0037] The diagram 20 has a time axis 21 and a torque axis 22 which in particular forms the ordinate. The torque curve 23 represents the torque curve 23 obtained by Figure 1 , which torque is output by the electric machine 1 in the embodiment of the present invention, and which torque extends constantly during the time interval 27 until the fault time 24. Starting from the fault time 24, a time interval 28 extends, which extends to the time 25 at which the excitation current in the excitation coil 4 is completely eliminated. The processing unit 9 is designed, for example, to control the H bridge 8 during the time interval 28 to change the polarity of the excitation coil 8, which causes an accelerated decrease in the excitation current.

[0038] For this purpose, the curve 34 represents the excitation current, which flows in the excitation coil, wherein the ordinate 31 in the diagram 20 represents the current intensity of the excitation current. In this case, the excitation current flows through the high-side semiconductor switch 17 and the excitation coil 4 and the complementary low-side semiconductor switch 16 during normal operation, and is regulated by the processing unit 9 by the pulse-width-modulated actuation of the semiconductor switches 17 and / or 16. In the event of a fault in one of the semiconductor switches for the normal operation of the semiconductor switch full bridge, the remaining semiconductor switches can be actuated by the control unit in such a way that the current in the excitation coil can be eliminated by means of the remaining semiconductor switches that are still intact until the zero value of the excitation current is reached at the time 25. In the subsequent time interval 29, the excitation current (especially in the reversed current direction) can be reestablished in the excitation coil until a maximum value is reached at the time 26. In particular, as described in DE 10 2017 101 069 A1, in the case of a high-resistance faulty high-side semiconductor switch 17, the elimination of the excitation field and the current commutation can be performed, for example, by closing the remaining high-side semiconductor switch 15 and the low-side semiconductor switch 18 complementary thereto, the closing being controlled by the control unit 9 so that the excitation current flows through the rotor coil in a direction reversed compared to normal operation. The control unit 9 is further configured to simultaneously close similar semiconductor switches (in this example, the low-side semiconductor switches of the H-bridge) and thus allow the no-load current in the low-side loop to flow through the rotor coil. As a result, the current direction of the coil current of the rotor coil can be quickly reversed.

[0039] The control unit is designed to allow the reversed excitation current to flow through the rotor coil 4 by closing the remaining low-side semiconductor switch 18 and the high-side semiconductor switch 15 in the case of a high-resistance faulty low-side semiconductor switch 16. The control unit 9 is further designed to simultaneously close similar semiconductor switches (in this example of a faulty low-side semiconductor switch, two high-side semiconductor switches of an H-bridge) and thus allow the no-load current in the high-side loop to flow through the rotor coil. As a result, the current direction of the coil current of the rotor coil can be quickly reversed.

[0040] A full bridge with a defective semiconductor switch can be further replaced by Figure 1 The control unit 9 in the embodiment is operated with a phase shift of 180 degrees, which is shown in Figure 2Phase curve 35 in the diagram. Here, the phase curve 35 represents the phase angle, and the change in the phase angle represents the displacement angle. Here, the phase pointer representing the phase shift points in the opposite direction. For this purpose, the ordinate 32 in the diagram 20 represents the phase position with respect to the control of the rotor coil, the semiconductor switch half bridge of which has a faulty semiconductor switch at the time 24 (i.e. the time of the fault). During the time interval 27 and during the time interval 28 until the time 25, the semiconductor switch full bridge is controlled with a phase angle at which the excitation current in the excitation coil has been eliminated, and the phase angle is used for the control with intact semiconductor switches. In this embodiment, the phase angle is 90 degrees by way of example. Starting from the time 25, during the time interval 29 and during the time interval 30 after the time interval 29, the phase angle is negative 90 degrees (electrical), at which the excitation current in the excitation coil can be eliminated, and at which the torque of the motor reaches its full value again at the time interval 30, and the phase angle is determined by the phase angle at the time interval 27. Figure 1 The processing unit 9 in is controlled.

[0041] exist Figure 1 The processing unit 9 in can be designed to interrupt the phase reversal in the region of the time 25 during the time interval in the region around the time 25, which is represented by the phase curve 35. This can advantageously prevent an undesired braking torque, in particular when the time 25 cannot be determined exactly.

[0042] Figure 2 The diagram 20 also shows an ordinate 33 which represents the magnitude of the stator current. Curve 36 represents the stator current which, until the time of the fault 24, has a magnitude which is particularly affected by the Figure 1 The processing unit 9 in the control - a constant value.

[0043] Starting from the fault time 24, the stator current can decrease until the time 25, at which the excitation current in the rotor coil decays. Starting from the time 25, the stator current can increase again, in particular stepwise, until the time 26, at which the amount of the excitation current in the excitation coil of the rotor is again fully built up in the direction of the reversal, which is represented by the curve 34. Thus, by removing the stator current during a phase shift, in particular during a phase reversal, a buildup of a negative braking torque can be advantageously prevented.

[0044] In a further embodiment, the processing unit 9 can be designed to interrupt the stator current at time 24 after the fault is detected and to start the phase reversal again with a changed phase position after reaching a predetermined rotor current at time 26. This results in a torque pause between times 24 and 26, in which the torque is reduced to a zero value.

[0045] Figure 3 A rotating stator field 42 of the stator 2 is schematically shown, which in normal operation has a direction 6, and which the excitation field 43 of the rotor 3 follows due to the torque 7. Among the poles of the stator field, pole 44 is shown by way of example, and among the poles of the excitation field of the rotor, pole 45 is shown by way of example. Figure 3 The black pole and the white pole are magnetized oppositely. For example, the black pole is the north pole and the white pole is the south pole. With the torque 7 in the same direction as the rotation direction 6, when opposite poles attract each other or like poles repel each other, Figure 1 The excitation field 43 of the rotor 3 in the embodiment follows the stator field 42 .

[0046] Figure 4 FIG. 4 shows a state in which a semiconductor switch of an H-bridge is faulty, wherein the current direction of the field current of the field coil 4 is reversed, for example by Figure 1 The processing unit 9 in the control. Now, at the location of the magnetic poles of the excitation field, the opposite magnetic poles are present after the current commutation. Therefore, the magnetic field of the excitation coil has been reversed. Now, the poles of the excitation field are close to the same magnetic poles of the stator field in the rotating stator field, which causes a repulsive or braking torque. This can be recognized in particular by the fact that the torque arrow 41 has an opposite direction relative to the rotation arrow 6.

[0047] Figure 5 Shown in Figure 1 The magnetic state of the motor 1 in FIG. 1 after the reversal of the field current and thus after the magnetic field reversal of the field of the excitation field in the rotor coil and after the phase shift of the rotating stator field by 180 degrees is determined by Figure 1 The processing unit 9 in the embodiment causes. Now, in the rotating stator field, after the magnetic field of the stator field has moved in the direction of rotation, the poles of the excitation field are again in the same relationship with the stator field as the H-bridge that energized the excitation coil before the fault. In this example, the phase angle 53 of the phase shift of the stator control is 180 degrees (electrical), and, as in Figure 5 In the diagram, the angle between the torque arrow 7 and the rotational direction 6 is 90 degrees in geometry. In particular, the torque arrow 7 and the rotational direction 6 point in the same direction again, so that the torque is built up in the same direction as the rotational direction.

[0048] exist Figure 5 In the example, the stator field and the excitation field are used to reconstruct the magnetic poles corresponding to Figure 3 Magnetic state.

Claims

1. An electric machine (1) having a stator (2) and a rotor (3), wherein: The electric motor (1) has a control unit (9) which is configured to control the electric motor (1) to generate an excitation field and a rotating magnetic field, wherein the electric motor (1) has an H-bridge (8) connected to the rotor (3), the H-bridge having a semiconductor switch full bridge. It is characterized in that The control unit (9) is configured to detect a fault in the semiconductor switches (17, 18) of the H-bridge (8), and to generate a fault signal representing the fault, and to reverse the direction of the excitation current of the motor according to the fault signal, and to change the phase position of the stator current to generate a rotating field (6) of the motor (1); and the control unit (9) is configured to reverse the phase position (35) of the electric control to generate the rotating field (6).

2. The electric machine (1) according to claim 1, characterized in that The displacement angle (37) of the electrically controlled phase position is between 160 degrees and 200 degrees, and is generated by the control unit (9) as a function of the fault signal.

3. The motor (1) according to claim 2, characterized in that: The electrically controlled displacement angle (35) is 180 degrees, and the displacement angle is generated by the control unit (9) according to the fault signal.

4. An electric machine (1) according to any one of the preceding claims, characterized in that The control unit (9) is designed to actuate the H-bridge (8) to switch the polarity of the field coil (4) and thereby to perform a rapid cancellation of the field for accelerated current commutation.

5. The electric machine (1) according to any one of the preceding claims 1 to 3, characterized in that The control unit (9) is designed to allow the field current (34) to decay and to carry out the change in the phase position after the field current has decayed.

6. The motor (1) according to claim 5, characterized in that: The control unit (9) is designed to allow a stator current (36) to decay and to carry out a change in the phase position after the stator current has decayed.

7. The electric machine (1) according to any one of the preceding claims 1 to 3, characterized in that The motor (1) has a current sensor (13) connected to the control unit (9), the current sensor being configured to detect a current direction or additionally detect a current intensity of the excitation current (34), and to generate a current signal representing the current direction or additionally representing the current intensity of the excitation current (34).

8. The electric machine (1) according to any one of the preceding claims 1 to 3, characterized in that The control unit (9) is designed to interrupt the activation of a phase as a function of the fault signal.

9. The electric machine (1) according to claim 1, characterized in that The electric motor is a claw-pole motor.

10. The electric machine (1) according to claim 5, characterized in that The control unit (9) is designed to carry out a change in the phase position during a zero crossing of the excitation current.

11. The electric machine (1) according to claim 8, characterized in that The control unit (9) is designed to interrupt the activation of the phase during a predetermined time interval as a function of the fault signal.

12. Method for operating an electric machine (1) according to any one of the preceding claims, wherein: A fault of a semiconductor switch (17, 18) which generates a field current (34) of the motor (1) is detected, a fault signal representative of the fault is generated, and an electrically generated phase position of a rotating field (6) is shifted by a predetermined displacement angle (37) in dependence on the fault signal.

Images