Motor drive device, motor drive method, and motor drive program

Abstract

A motor drive device 100 comprises: an acquisition unit 41 that detects and acquires a multi-phase output current from an inverter 22 that includes a plurality of switching elements Ua, Ub, Va, Vb, Wa, Wb for driving a multi-phase AC motor 3; a determination unit 42 that determines an overcurrent in the plurality of switching elements on the basis of the multi-phase output current acquired by the acquisition unit; and a generation unit 43 that generates a switching instruction on the basis of the determination by the determination unit, and that outputs the switching instruction to the plurality of switching elements. When it is determined by the determination unit 42 that an overcurrent is flowing, the generation unit 43: outputs an off instruction to at least one switching element with respect to a phase in which the determination unit has determined that no overcurrent is flowing, and then outputs an off instruction to at least one switching element with respect to a phase in which the determination unit has determined that an overcurrent is flowing.

Description

Motor drive device, motor drive method, and motor drive program

[0001] The embodiments described in this application relate to a motor driving device, a motor driving method, and a motor driving program.

[0002] In recent years, in motor drive devices that drive AC motors in machine tools, forging machines, injection molding machines, industrial machinery, or various robots, AC power supplied from an AC power source is first converted to DC power and then converted back to AC power, and this AC power is supplied as drive power to the motors provided for each drive shaft via motor power lines.

[0003] For this reason, the motor drive device is equipped with a converter (rectifier) ​​that converts (rectifies) AC power input from the AC power supply side into DC power, and an inverter that converts DC power in the DC link, which is the DC side of the converter, into AC power.

[0004] Conventionally, when an overcurrent due to a short circuit is detected in an inverter, it is common to immediately cut off (turn off) a switching element on the short-circuit path upon detection of the overcurrent in order to cut off the overcurrent early.

[0005] However, for example, in an inverter that drives a multi-phase AC motor, if a switching element on a short-circuit path that detects an overcurrent is immediately turned off, voltage oscillations may occur on the DC link due to the turn-off energy generated when the current is turned off, depending on the circuit. Furthermore, depending on the location of the short-circuit and the circuit configuration, voltage oscillations greater than those of the phase in which the overcurrent was detected may be applied to other switching elements due to reflection or superposition of the voltage oscillations. Therefore, even if there is no problem with the voltage of the phase in which the overcurrent was interrupted, overvoltages may occur in other phases, and switching elements outside the short-circuit path may be destroyed by overvoltages.

[0006] 2. Description of the Related Art In the past, attention has been focused on short circuits in inverters that drive polyphase AC motors, and various proposals have been made to reduce overvoltage breakdown of switching elements when an overcurrent occurs due to a short circuit.

[0007] JP 2008-118834 A JP 2013-198182 A

[0008] As mentioned above, for example, in an inverter that drives a polyphase AC motor, if a switching element on a short-circuit path where an overcurrent is detected is immediately turned off, a voltage oscillation larger than that of the phase where the overcurrent is detected may be applied to other switching elements, which may result in overvoltage breakdown.

[0009] Furthermore, even if an overcurrent is detected and a command is issued to shut off all phases of the switching elements simultaneously, it takes time for the switching elements to actually turn off completely, and there is a risk that the voltage oscillation will be applied to only one of the pair of switching elements, causing overvoltage breakdown.

[0010] The problem to be solved by the present invention is to provide a motor drive device, a motor drive method, and a motor drive program that can prevent overvoltage breakdown of power elements in an inverter even when a short circuit occurs in the power element.

[0011] According to one embodiment of the present invention, there is provided a motor drive device comprising: an acquisition unit that detects and acquires output currents of multiple phases from an inverter including multiple switching elements that drive a polyphase AC motor; a determination unit that determines overcurrent in the multiple switching elements based on the output currents of the multiple phases acquired by the acquisition unit; and a generation unit that generates switching commands based on the determination of the determination unit and outputs the commands to the multiple switching elements.

[0012] When the judgment unit determines that an overcurrent is flowing, the generation unit outputs an OFF command to at least one switching element in the phase in which the judgment unit determines that an overcurrent is not flowing, and then outputs an OFF command to at least one switching element in the phase in which the judgment unit determines that an overcurrent is flowing.

[0013] The objects and advantages of the invention will be realized and obtained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed.

[0014] FIG. 1 is a block diagram illustrating an example of a motor drive device according to the present embodiment. FIG. 2 is a diagram illustrating a first example of a motor drive device according to the present embodiment in comparison with a conventional example. FIG. 3 is a diagram illustrating the first example of a motor drive device according to the present embodiment. FIG. 4 is a diagram illustrating a second example of a motor drive device according to the present embodiment. FIG. 5 is a diagram illustrating a third example of a motor drive device according to the present embodiment. FIG. 6 is a diagram illustrating a fourth example of a motor drive device according to the present embodiment. FIG. 7 is a diagram illustrating a fifth example of a motor drive device according to the present embodiment. FIG. 8 is a diagram illustrating a sixth example of a motor drive device according to the present embodiment. FIG. 9 is a diagram illustrating a first modified example of a motor drive device according to the present embodiment. FIG. 10 is a diagram illustrating a second modified example of a motor drive device according to the present embodiment.

[0015] Examples of a motor drive device, a motor drive method, and a motor drive program according to this embodiment will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating an example of a motor drive device according to this embodiment. In FIG. 1, reference numerals 1, 3, 4, and 100 denote an AC power supply, a motor (a multi-phase AC motor), a control unit, and a motor drive device, respectively. The AC power supply 1 may be three-phase or single-phase, such as a three-phase 400V AC power supply, a three-phase 200V AC power supply, a three-phase 600V AC power supply, or a single-phase 100V AC power supply. In the following description, the AC power supply 1 is described as a three-phase AC power supply, and the motor 3 is described as a three-phase AC motor, by way of example.

[0016] 1, motor drive device 100 receives power from a three-phase AC power supply 1 and outputs drive power for each phase (U-phase, V-phase, and W-phase) of a three-phase motor 3. It includes a converter 21, an inverter 22, a DC link capacitor 23, and a control unit 4. Converter 21 is configured, for example, as a three-phase full-bridge circuit, and is a rectifier that converts AC power input from its AC input side into DC power and outputs it to a DC link on its DC output side. DC link capacitor 23 smoothes pulsation in the DC output of converter 21 and stores the DC power to be output to inverter 22.

[0017] The inverter 22 is connected to the converter 21 via a DC link, and converts DC power in the DC link into AC power for driving the motor and outputs it. That is, the inverter 22 receives DC power that is the output of the converter 21, smoothed and stored by a DC link capacitor 23, and controls the drive of the three-phase AC motor 3 based on a control signal (control command) from the control unit 4.

[0018] 1, the motor 3 is a three-phase AC motor, and therefore the inverter 22 is configured as a three-phase full-bridge circuit. That is, the inverter 22 includes power semiconductors (power elements) T1, T4, T2, T5, and T3, T6 connected to a high-potential power supply line and a low-potential power supply line for the U-phase, V-phase, and W-phase of the three-phase AC motor 3, respectively, and free wheeling diodes (FWDs) D1, D4, D2, D5, and D3, D6 connected in anti-parallel to each power semiconductor.

[0019] Here, for example, IGBTs (insulated gate bipolar transistors) are applied as the power semiconductors T1, T4, T2, T5, T3, and T6, but the power semiconductors are not limited to IGBTs, and various power elements can be applied, such as FETs (field-effect transistors), thyristors, GTOs (gate turn-off thyristors), SiC-MOSFETs (silicon carbide metal-oxide-semiconductor field-effect transistors), and power semiconductors using GaN (gallium nitride).

[0020] In FIG. 1 , reference symbol Ua denotes the U-phase pull-up side switching elements (T1 and D1), and Ub denotes the U-phase pull-down side switching elements (T4 and D4). Similarly, reference symbol Va denotes the V-phase pull-up side switching elements (T2 and D2), and Vb denotes the V-phase pull-down side switching elements (T5 and D5). Furthermore, reference symbol Wa denotes the W-phase pull-up side switching elements (T3 and D3), and Wb denotes the W-phase pull-down side switching elements (T6 and D6). Note that in the following description, as an example, the inverter 22 drives a three-phase AC motor 3. However, the motor drive device 100 of this embodiment is not limited to driving and controlling a three-phase AC motor, and may, of course, also drive and control various multi-phase AC motors, such as four-phase, six-phase, or twelve-phase motors.

[0021] [First Example] Figure 2 is a diagram illustrating a first example of a motor drive device according to this embodiment, compared with a conventional example. Here, Figure 2(A) is a diagram illustrating an example of an overcurrent (short-circuit current) flowing from a high-potential power line (pull-up side) to a low-potential power line (pull-down side), and an example of how the switching elements are turned off in that case. Figure 2(B) is a diagram illustrating an example of how the motor drive device of this first example turns off the switching elements when an overcurrent flows as shown in Figure 2(A).

[0022] The inverter 22 that drives and controls the three-phase AC motor 3 includes pairs of switching elements Ua, Ub, Va, Vb and Wa, Wb (e.g., six switching elements) provided in the U-phase, V-phase and W-phase, and when the three-phase AC motor 3 is driven, one of the pair of switching elements (e.g., three switching elements) is turned on and the other (e.g., three switching elements) is turned off.

[0023] 2A, for example, when one of the switching elements Ua, Vb, and Wa is turned on and the other switching elements Ub, Va, and Wb are turned off, a short circuit (inter-phase short circuit) occurs between the U phase and the V phase, causing an overcurrent to flow from the high potential power supply line to the low potential power supply line via the switching elements Ua and Vb. In this case, in a conventional example, an OFF command is generally output to the switching elements Ua and Vb on the short circuit path to shut them off (control from ON to OFF).

[0024] Here, one of the pair of W-phase switching elements Wa, Wb is on and the other switching element Wb is off. Therefore, for example, when the switching elements Ua and Vb on the short-circuit path change from on to off, a voltage oscillation larger than that of the U-phase and V-phase in which the overcurrent was detected is applied across the W-phase switching element Wb, which may cause overvoltage breakdown in the switching element Wb.

[0025] In such a case, according to the motor drive device of the first embodiment, as shown in Fig. 2(B), before switching the switching elements Ua and Vb on the short-circuit path from on to off, for example, the W-phase switching element Wa is switched from on to off. This allows the voltage oscillation (overvoltage, surge voltage) applied across the switching element Wb in Fig. 2(A) to be divided by the switching elements Wa and Wb, thereby preventing (reducing) overvoltage breakdown. That is, according to the first embodiment, after outputting an OFF command to the W-phase switching element Wa through which no overcurrent is flowing (not through the short-circuit path), an OFF command is output to the switching elements Ua and Vb through which an overcurrent is flowing (which are on the short-circuit path).

[0026] 3A and 3B are diagrams illustrating a first example of a motor drive device according to the present embodiment. Here, FIG. 3A is a circuit diagram illustrating a short circuit and the operation that occurs in the first example, and FIG. 3B is a flowchart illustrating an example of control processing (processing of the motor drive program) in the first example. Similar to FIGS. 2A and 2B, FIGS. 3A and 3B illustrate a case in which a short circuit (interphase short circuit) occurs between the U and V phases, causing an overcurrent to flow from the high-potential power line to the low-potential power line via switching elements Ua and Vb.

[0027] As shown in FIG. 3A, the motor drive device 100 (controller 4) of the first embodiment includes an acquisition unit 41, a determination unit 42, and a generation unit 43. The acquisition unit 41 detects and acquires three-phase output currents from an inverter 22 including six switching elements Ua, Ub, Va, Vb, Wa, and Wb that drive a three-phase AC motor 3. The determination unit 42 determines overcurrents in the six switching elements Ua, Ub, Va, Vb, Wa, and Wb based on the three-phase output currents acquired by the acquisition unit 41. The generation unit 43 generates switching commands based on the determination of the determination unit 42 and outputs them to the six switching elements Ua, Ub, Va, Vb, Wa, and Wb.

[0028] Here, reference characters C1, C2, C3, C4, C5, and C6 indicate drive units that receive control commands (control signals) output from the generation unit 43 and control the on / off of the corresponding switching elements Ua, Ub, Va, Vb, Wa, and Wb. Needless to say, various known configurations can be applied to the drive units C1 to C6.

[0029] For example, when the determination unit 42 determines that an overcurrent is flowing in the U-phase and V-phase (switching elements Ua, Vb in the U-phase and V-phase), the generation unit 43 outputs an OFF command to the W-phase (switching element Wa in the W-phase: P11) in which the determination unit 42 determines that no overcurrent is flowing. Thereafter, the generation unit 43 outputs an OFF command to the switching elements Ua, Vb (P12) in the U-phase and V-phase in which the determination unit 42 determines that an overcurrent is flowing.

[0030] 3B, when an example of processing of the motor drive program in the first embodiment starts, in step ST11, the acquisition unit 41 acquires the currents of each phase (drive currents of U-phase, V-phase, and W-phase) that drive the three-phase AC motor 3 from the inverter 22, and the process proceeds to step ST12. In step ST12, the determination unit 42 determines whether or not there is an overcurrent in each phase, and if it determines that there is no overcurrent, the process returns to step ST11, and if it determines that there is an overcurrent, the process proceeds to step ST13.

[0031] In step ST13, the generator 43 generates OFF commands to turn off the switching elements in the following order: 1. The generator 43 outputs an OFF command (P11) to turn off the switching element Wa in a phase that is not determined to be an overcurrent, and then 2. The generator 43 outputs an OFF command (P12) to turn off the switching elements Ua and Vb in a phase that is determined to be an overcurrent. Then, the process proceeds to step ST14, where the switching elements are turned off in accordance with the timing of the generation by the generator 43. Specifically, the drivers C1, C2, C3, C4, C5, and C6 each receive the control commands output from the generator 43 and control the ON / OFF of the corresponding switching elements Ua, Ub, Va, Vb, Wa, and Wb.

[0032] As described above, according to the first embodiment, for example, when the determination unit 42 determines that an overcurrent is flowing in the U-phase and V-phase (switching elements in the U-phase and V-phase), the generation unit 43 outputs (P11) an OFF command to at least one switching element Wa in the W-phase in which the determination unit 42 determines that no overcurrent is flowing. Thereafter, the generation unit 43 outputs (P12) an OFF command to at least one switching element Ua, Vb in the U-phase and V-phase in which the determination unit 42 determines that an overcurrent is flowing. This makes it possible to prevent overvoltage breakdown of the switching element Wb in the W-phase, as described with reference to FIGS. 2A and 2B, for example.

[0033] [Second Example] Figure 4 is a diagram illustrating a second example of a motor drive device according to the present embodiment. Here, Figure 4(A) is a circuit diagram illustrating a short circuit and the operation at that time in the second example, and Figure 4(B) is a flowchart illustrating an example of the processing of the motor drive program in the second example. Similar to Figures 3(A) and 3(B) described above, Figures 4(A) and 4(B) illustrate a case in which a short circuit occurs between the U phase and the V phase, causing an overcurrent to flow from the high-potential power line to the low-potential power line via switching elements Ua and Vb.

[0034] 4(A) and 4(B) with the above-described FIGS. 3(A) and 3(B), in the second embodiment, the switching element Ua in the U phase and the switching element Vb in the V phase are turned off with a time lag. That is, when the determination unit 42 determines that a short circuit has occurred between the U phase and the V phase, the generation unit 43 does not output OFF commands to the switching elements Ua and Vb simultaneously (P12 in FIG. 3(A)) as in the first embodiment, but in the second embodiment, the generation unit 43 outputs, for example, an OFF command to the switching element Ua (P22) and then outputs an OFF command to the switching element Vb with a time lag (P23).

[0035] 4B, when an example of processing of the motor drive program in the second embodiment starts, in step ST21 the acquisition unit 41 acquires the drive currents of the U-phase, V-phase, and W-phase of the three-phase AC motor 3 output from the inverter 22, and then the process proceeds to step ST22. In step ST22, the determination unit 42 determines whether or not an overcurrent exists in each phase, and if it determines that an overcurrent does not exist, the process returns to step ST21, but if it determines that an overcurrent exists, the process proceeds to step ST23.

[0036] In step ST23, the generator 43 generates OFF commands to shut off the switching elements in the following order: 1. Outputs an OFF command (P21) to turn off the switching element Wa in a phase that is not determined to be an overcurrent. 2. Then, outputs an OFF command (P22) to turn off at least one phase (the switching element Ua in the U phase) among the phases determined to be an overcurrent. 3. After a time lag, outputs an OFF command (P23) to turn off the remaining phase (the switching element Vb in the V phase) determined to be an overcurrent. Then, the process proceeds to step ST24, where the switching elements are shut off (shutoff control) via, for example, the drivers (C1 to C6) in accordance with the timing of the generation by the generator 43.

[0037] 4A, according to the second embodiment, the generation unit 43 outputs (P21) an OFF command to the switching element Wa (Wa, Wb) in at least one phase (W phase) in which it has been determined by the determination unit 42 that no overcurrent is flowing. Thereafter, it outputs (P22) an OFF command to the switching element Ua in the remaining phase (U phase) in which it has been determined by the determination unit 42 that an overcurrent is flowing, and further, after a time lag, it outputs (P23) an OFF command to the switching element Vb in the remaining phase (V phase) in which it has been determined by the determination unit 42 that an overcurrent is flowing.

[0038] That is, according to the second embodiment, by cutting off the switching elements Ua and Vb in the phase in which it is determined that an overcurrent is flowing with a time lag, it is possible to reduce the instantaneous applied voltage level and further prevent overvoltage breakdown of the switching elements.

[0039] [Third Example] Figure 5 is a diagram illustrating a third example of a motor drive device according to the present embodiment. Here, Figure 5(A) is a circuit diagram illustrating a short circuit and the operation at that time in the third example, and Figure 5(B) is a flowchart illustrating an example of control processing in the third example. Note that Figures 5(A) and 5(B) illustrate a case where a short circuit (ground fault) occurs between the U phase and the low-potential power supply line (ground line), causing an overcurrent to flow from the high-potential power supply line to the low-potential power supply line via the switching element Ua.

[0040] 5A, for example, when a ground fault occurs in the U phase, the generation unit 43 outputs (P31) an OFF command to the switching elements Va, Vb, Wa, and Wb in the V phase and the W phase in which the determination unit 42 has determined that no overcurrent is flowing. Thereafter, the generation unit 43 outputs (P32) an OFF command to the switching element Ua in the U phase in which the determination unit 42 has determined that an overcurrent is flowing.

[0041] 5B, when an example of processing of the motor drive program in the third embodiment starts, in step ST31, the acquisition unit 41 acquires the drive currents of the U-phase, V-phase, and W-phase of the three-phase AC motor 3 output from the inverter 22, and the process proceeds to step ST32. In step ST32, the determination unit 42 determines whether or not an overcurrent exists in each phase, and if it determines that an overcurrent does not exist, the process returns to step ST31, but if it determines that an overcurrent exists, the process proceeds to step ST33.

[0042] In step ST33, the generator 43 generates OFF commands to shut off the switching elements in the following order: 1. Outputs OFF commands to shut off the switching elements in multiple phases (V phase, W phase) that are not determined to be overcurrent. 2. Outputs OFF commands to shut off the switching elements in the phase (U phase) that is determined to be overcurrent. Then, the process proceeds to step ST34, where the switching elements are shut off in accordance with the timing generated by the generator 43.

[0043] 5A, according to the third embodiment, the generation unit 43 outputs (P31) an OFF command to the switching elements Va, Vb, Wa, and Wb in the multiple phases (V phase, W phase) in which it has been determined that no overcurrent is flowing by the determination unit 42. Thereafter, it outputs (P32) an OFF command to the switching element Ua in at least one phase (U phase) in which it has been determined that an overcurrent is flowing by the determination unit 42.

[0044] [Fourth Example] Figure 6 is a diagram illustrating a fourth example of a motor drive device according to the present embodiment. Here, Figure 6(A) is a circuit diagram illustrating a short circuit and the operation at that time in the fourth example, and Figure 6(B) is a flowchart illustrating an example of control processing in the fourth example. Similar to Figures 5(A) and 5(B) described above, Figures 6(A) and 6(B) illustrate a case in which a ground fault occurs in the U phase and an overcurrent flows from the high-potential power line to the ground line (low-potential power line) via the switching element Ua.

[0045] As shown in FIG. 6A, in the fourth embodiment, the switching elements Va, Vb, Wa, and Wb in the V-phase and W-phase for which the determining unit 42 has determined that no overcurrent is flowing are not turned off simultaneously, but are turned off at staggered timings.

[0046] 6(B), when an example of processing of the motor drive program in the fourth embodiment starts, in step ST41, the acquisition unit 41 acquires the drive currents of the U-phase, V-phase, and W-phase of the three-phase AC motor 3 output from the inverter 22, and then the process proceeds to step ST42. In step ST42, the determination unit 42 determines whether or not an overcurrent exists in each phase, and if it determines that an overcurrent does not exist, the process returns to step ST41, but if it determines that an overcurrent exists, the process proceeds to step ST43.

[0047] In step ST43, the generator 43 generates OFF commands to shut off the switching elements in the following order: 1. Outputs OFF commands to the switching elements in some phases (W phase) among the multiple phases (V phase, W phase) that are not determined to be experiencing an overcurrent; 2. Outputs OFF commands to the switching elements in the remaining phase (V phase) among the multiple phases in which the determiner 42 has determined that no overcurrent is flowing; 3. Outputs OFF commands to the switching elements in the phase (U phase) determined by the determiner 42 to be experiencing an overcurrent; 4. Then, the process proceeds to step ST44, where the switching elements are shut off in accordance with the timing generated by the generator 43.

[0048] 6A, according to the fourth embodiment, the generation unit 43 outputs (P41) an OFF command to the switching elements Wa and Wb in some phases (W phase) among the multiple phases (V phase, W phase) in which the determination unit 42 has determined that no overcurrent is flowing. Then, the generation unit 43 outputs (P42) an OFF command to the switching elements Va and Vb in the remaining phase (V phase) among the multiple phases (V phase, W phase) in which the determination unit 42 has determined that no overcurrent is flowing. Then, the generation unit 43 further outputs (P43) an OFF command to the switching element Ua in the phase (U phase) in which the determination unit 42 has determined that an overcurrent is flowing.

[0049] [Fifth Example] Figure 7 is a diagram illustrating a fifth example of a motor drive device according to the present embodiment. Here, Figure 7(A) is a circuit diagram illustrating a short circuit and the operation that occurs in the fifth example, and Figure 7(B) is a flowchart illustrating an example of control processing in the fifth example. Figures 7(A) and 7(B) illustrate a case in which a short circuit occurs in all of the U, V, and W phases (a three-phase short circuit), causing an overcurrent to flow from the high-potential power line to the low-potential power line via switching elements Ua, Vb, and Wb.

[0050] 7A, when the determination unit 42 determines that an overcurrent is flowing in all phases (U phase, V phase, W phase), the generation unit 43 outputs (P51) an OFF command to the switching element Wb in at least one phase (W phase), then outputs (P52) an OFF command to the switching element Vb in the remaining phase (V phase) other than at least one phase, and then outputs (P53) an OFF command to the switching element Ua in the remaining phase (U phase) other than at least one phase.

[0051] 7B, when an example of processing of the motor drive program in the fifth embodiment starts, in step ST51, the acquisition unit 41 acquires the drive currents of the U-phase, V-phase, and W-phase of the three-phase AC motor 3 output from the inverter 22, and then the process proceeds to step ST52. In step ST52, the determination unit 42 determines whether or not an overcurrent exists in all phases, and if it determines that an overcurrent exists in all phases, the process proceeds to step ST53, but if it determines that an overcurrent does not exist in all phases, the process returns to step ST51.

[0052] In step ST53, the generator 43 generates OFF commands to turn off the switching elements in the following order: 1. Outputs OFF commands to the switching elements in at least one phase. Then, 2. Outputs OFF commands to the switching elements in the remaining phases. Then, the process proceeds to step ST54, where the switching elements are turned off in accordance with the timing generated by the generator 43.

[0053] That is, as shown in FIG. 7A , according to the fifth embodiment, when the determination unit 42 determines that an overcurrent is flowing through all phases and that a three-phase short circuit has occurred, the generation unit 43 outputs (P51) an OFF command to the switching element Wb in at least one phase (W phase). Thereafter, the generation unit 43 outputs (P52) an OFF command to the switching element Vb in the V phase other than the W phase. Thereafter, the generation unit 43 further outputs (P53) an OFF command to the switching element Ua in the U phase other than the W phase. Here, after outputting (P51) the OFF command to the switching element Wb, it is also possible to simultaneously output OFF commands to the switching elements Vb and Ua.

[0054] [Sixth Example] Figure 8 is a diagram for explaining a sixth example of the motor drive device according to the present embodiment. Here, Figure 8(A) is a circuit diagram for explaining a short circuit and the operation at that time in the sixth example, and Figure 8(B) is a flowchart for explaining an example of a control process in the sixth example. Here, Figure 8(A) is substantially the same as Figure 7(A) described above.

[0055] 8A, when the determination unit 42 determines that an overcurrent is flowing in all phases (U phase, V phase, W phase), the generation unit 43 outputs an OFF command to the switching element in the phase at the top of the structure, and then outputs OFF commands to the switching elements in the remaining phases. That is, in the sixth embodiment, the OFF command is first output (P61) to the switching element Wb in the phase at the top of the structure (W phase: the W phase located at the end of the wiring in the circuit configuration) in the fifth embodiment described above. Thereafter, the process is substantially the same as in the fifth embodiment.

[0056] 8(B), when an example of processing of the motor drive program in the sixth embodiment starts, in step ST61, the acquisition unit 41 acquires the drive currents of the U-phase, V-phase, and W-phase of the three-phase AC motor 3 output from the inverter 22, and then the process proceeds to step ST62. In step ST62, the determination unit 42 determines whether or not an overcurrent exists in all phases, and if it determines that an overcurrent exists in all phases, the process proceeds to step ST63, but if it determines that an overcurrent does not exist in all phases, the process returns to step ST61.

[0057] In step ST63, the generator 43 generates OFF commands to shut off the switching elements in the following order: 1. The generator 43 outputs OFF commands to the switching elements in the phase at the top of the structure. Then, 2. The generator 43 outputs OFF commands to the switching elements in the remaining phases. Then, the process proceeds to step ST64, where the generator 43 controls the shutoff of the switching elements (via the drivers C1 to C6) in accordance with the timing of the commands generated by the generator 43.

[0058] That is, as shown in FIG. 8A , according to the sixth embodiment, when the determination unit 42 determines that an overcurrent is flowing through all phases and that a three-phase short circuit has occurred, the generation unit 43 first outputs an OFF command (P61) to the switching element Wb in the W-phase, which is structurally located at the end of the wiring. Thereafter, the generation unit 43 outputs an OFF command (P62) to the switching element Vb in the V-phase other than the W-phase. Thereafter, the generation unit 43 further outputs an OFF command (P63) to the switching element Ua in the U-phase other than the W-phase. Here, after first outputting an OFF command (P61) to the switching element Wb, it is also possible to simultaneously output OFF commands to the switching elements Vb and Ua.

[0059] In this way, according to the motor drive devices of the first to sixth embodiments, it is possible to prevent overvoltage breakdown in the switching elements when various overcurrents flow, such as, for example, a phase-to-phase short circuit, a ground fault, and a three-phase short circuit in the inverter.

[0060] [First Modification] Figure 9 is a diagram illustrating a first modification of the motor drive device according to the present embodiment, where Figure 9(A) is a circuit diagram illustrating a short circuit and the operation at that time in the first modification, and Figure 9(B) is a flowchart illustrating an example of a control process in the first modification.

[0061] 9A with the above-described FIG. 3A, in this first modified example, the acquisition unit 41 detects and acquires the output currents of multiple phases (U phase, V phase) excluding the output current of at least one phase (W phase) of the inverter 22, rather than the output currents of all phases (U phase, V phase, W phase) that drive the motor 3. In other words, the output current of the W phase is estimated by the estimation unit 44 based on the output currents of the U phase and V phase acquired by the acquisition unit 41.

[0062] As described above, this first modified example can be applied to the first to sixth embodiments described above. It goes without saying that the output current estimated by the estimation unit 44 is not limited to one phase, but may be two or more phases if, for example, the number of phases of the AC motor 3 increases and the number of current outputs of the inverter 22 also increases accordingly. Here, Figures 9(A) and 9(B) show the first modified example applied to the first embodiment described with reference to Figures 3(A) and 3(B), but as described above, this modified example can also be applied to the second to sixth embodiments.

[0063] 9(B), when an example of processing of the motor drive program in the first modified example starts, in step ST71, the acquisition unit 41 acquires the U-phase and V-phase drive currents of the three-phase AC motor 3 output from the inverter 22, and the process proceeds to step ST72. In step ST72, the acquisition unit 41 estimates the W-phase drive current based on the U-phase and V-phase drive currents acquired, and the process proceeds to step ST73.

[0064] In step ST73, the determination unit 42 determines whether an overcurrent exists in all phases (whether an overcurrent exists in each phase). If it determines that an overcurrent exists in all phases, the process proceeds to step ST74. If it determines that an overcurrent does not exist in all phases, the process returns to step ST71. In step ST74, the generation unit 43 generates OFF commands to shut off the switching elements in the following order. That is, the generation unit 43 1. outputs an OFF command to the switching element Wa (Wa, Wb) in the phase (W phase) that is not determined to be an overcurrent. Then, 2. outputs OFF commands to the switching elements Ua, Vb in the phases (U phase, V phase) that are not determined to be an overcurrent. Here, in FIG. 9A, the OFF command is output (P72) to the switching element Vb (Va, Vb) and then the OFF command is output (P73) to the switching element Ua (Ua, Ub). However, OFF commands can also be output simultaneously to the switching elements Ua and Vb (Ua, Ub, Va, Vb).

[0065] [Second Modification] FIG. 10 is a diagram illustrating a second modification of the motor drive device according to the present embodiment. Here, FIG. 10(A) is a circuit diagram illustrating a short circuit and the operation at that time in the second modification, and FIG. 10(B) is a flowchart illustrating an example of control processing in the second modification. Note that FIGS. 10(A) and 10(B) illustrate the application of the first modification described with reference to FIGS. 9(A) and 9(B), and FIG. 10(A) is similar to FIG. 9(A) described above. That is, this second modification can be applied to the first through sixth examples to which the first modification is applied, but it can also be applied to the first through sixth examples to which the first modification is not applied. In other words, the first and second modifications can be applied arbitrarily (as appropriate) to the first through sixth examples.

[0066] 10(B), when an example of processing of the motor drive program in the second modified example starts, in step ST81, the acquisition unit 41 acquires the U-phase and V-phase drive currents of the three-phase AC motor 3 output from the inverter 22, and the process proceeds to step ST82. In step ST82, the acquisition unit 41 estimates the W-phase drive current based on the U-phase and V-phase drive currents acquired, and the process proceeds to step ST83.

[0067] In step ST83, the determination unit 42 determines whether or not it is necessary to turn off the phases in which no overcurrent is flowing in advance, based on the current of each phase and its change over time (di / dt). If it is determined in step ST83 that an overcurrent is flowing and that turning off is necessary, the process proceeds to step ST84, where the interruption (the same processing) is performed in the same manner as in the above-described first to sixth embodiments (first to sixth embodiments to which modified example 1 is applied). Here, the determination by the determination unit 42 as to whether or not turning off is necessary can be made, for example, based on whether or not the di / dt (change in current per time) exceeds a predetermined value.

[0068] As in the second modification, for example, by comparing di / dt with a predetermined value to determine whether or not an overcurrent has flowed in a phase, it becomes possible to reduce unnecessary processing and continue driving the motor 3. The predetermined value to be compared with di / dt is selected to be optimal based on the capacity and specifications of the applied polyphase AC motor 3, as well as the specifications of the robot or the like in which the motor 3 is used.

[0069] In the above, the motor drive devices of the first to sixth embodiments described above, or the motor drive devices of the first to sixth embodiments to which the first and / or second modified embodiments are applied, can also be implemented as a motor drive method, and, for example, as a motor drive program to be executed by a calculation device in the motor drive device.

[0070] The motor drive program according to the present embodiment may be provided by recording it on a computer-readable non-transitory recording medium or a non-volatile semiconductor storage device, or may be provided via a wired or wireless connection. Examples of computer-readable non-transitory recording media include optical disks such as CD-ROMs (Compact Disc Read Only Memory) and DVD-ROMs, or hard disk drives. Examples of non-volatile semiconductor storage devices include PROMs (Programmable Read Only Memory) and flash memories. Furthermore, the program may be distributed from a server device via a wired or wireless wide area network (WAN), local area network (LAN), or the Internet.

[0071] As described above in detail, the motor drive device, motor drive method, and motor drive program according to this embodiment make it possible to prevent overvoltage breakdown of power elements in an inverter even if a short circuit occurs in the power elements.

[0072] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0073] REFERENCE SIGNS LIST 1 AC power supply (three-phase AC power supply) 3 Motor (three-phase AC motor) 4 Control unit 21 Converter 22 Inverter 23 DC link capacitor 41 Acquisition unit 42 Determination unit 43 Generation unit 44 Estimation unit 100 Motor drive device

Claims

1. an acquisition unit that detects and acquires a multi-phase output current from an inverter including a plurality of switching elements that drives a multi-phase AC motor; a determination unit that determines an overcurrent in the plurality of switching elements based on the output currents of the plurality of phases acquired by the acquisition unit; a generating unit that generates a switching command based on the determination by the determining unit and outputs the switching command to the plurality of switching elements; When the determination unit determines that an overcurrent is flowing, the generation unit After outputting an OFF command to at least one switching element in a phase in which it has been determined by the determination unit that no overcurrent is flowing, a motor drive device that outputs an OFF command to at least one switching element in a phase in which the determination unit has determined that an overcurrent is flowing;

2. The generation unit is After outputting an OFF command to a switching element in at least one phase in which it has been determined by the determination unit that no overcurrent is flowing, 2. The motor drive device according to claim 1, further comprising: an off command outputting a time lag to switching elements in the remaining phases in which the determining unit has determined that an overcurrent is flowing.

3. The generation unit is outputting an OFF command to switching elements in a plurality of phases in which it has been determined by the determination unit that no overcurrent is flowing; 2. The motor drive device according to claim 1, further comprising: an OFF command outputted to a switching element in at least one phase in which the determining unit has determined that an overcurrent is flowing.

4. The generation unit is An OFF command is output to switching elements in some of the phases among the plurality of phases in which it is determined by the determination unit that no overcurrent is flowing, and then outputting an OFF command to switching elements in the remaining phases of the plurality of phases in which it has been determined by the determination unit that no overcurrent is flowing; and 2. The motor drive device according to claim 1, further comprising: an OFF command outputted to a switching element in at least one phase in which the determining unit has determined that an overcurrent is flowing.

5. The generation unit is When the determining unit determines that an overcurrent is flowing in all phases, an OFF command is output to a switching element in at least one phase, and then 2. The motor drive device according to claim 1, further comprising: an OFF command outputted to switching elements in phases other than the at least one phase.

6. The generation unit is 6. The motor drive device according to claim 5, further comprising: a switch that switches the motor drive circuitry so as to turn off the switching elements when the switch determines that an overcurrent is flowing in all phases;

7. The acquisition unit detects and acquires output currents of multiple phases excluding an output current of at least one phase of the inverter, The inverter further includes an estimation unit that estimates an output current of the at least one removed phase based on the output currents of the multiple phases acquired by the acquisition unit, 7. The motor drive device according to claim 1, wherein the determination unit determines an overcurrent in the plurality of switching elements based on the output currents of the plurality of phases acquired by the acquisition unit and the output current of the at least one phase estimated by the estimation unit.

8. 7. The motor drive device according to claim 1, wherein the determination unit determines an overcurrent in the plurality of switching elements based on a time change in the output current of the plurality of phases acquired by the acquisition unit.

9. moreover, The motor drive device according to claim 1 , further comprising a drive unit that controls the driving of the plurality of switching elements based on a command output from the generation unit.

10. the polyphase AC motor is a three-phase AC motor, 7. The motor drive device according to claim 1, wherein the determination unit determines an overcurrent in at least one switching element in at least one of a U phase, a V phase, and a W phase in the three-phase AC motor.

11. Detecting and acquiring a multi-phase output current from an inverter including a plurality of switching elements that drives a multi-phase AC motor; determining an overcurrent in the plurality of switching elements based on the acquired output currents of the plurality of phases; generating a switching command based on the determined overcurrent in the plurality of switching elements; A motor drive method for outputting the switching commands to the plurality of switching elements, comprising: When it is determined that an overcurrent is flowing, After outputting an OFF command to at least one switching element in a phase in which it is determined that no overcurrent is flowing, A motor driving method comprising: outputting an OFF command to at least one switching element in a phase in which it is determined that an overcurrent is flowing.

12. A processing unit includes: Detecting and acquiring a multi-phase output current from an inverter including a plurality of switching elements that drives a multi-phase AC motor; determining an overcurrent in the plurality of switching elements based on the acquired output currents of the plurality of phases; generating a switching command based on the determined overcurrent in the plurality of switching elements; A motor drive program for executing a process of outputting the switching command to the plurality of switching elements, When it is determined that an overcurrent is flowing, the arithmetic processing device After outputting an OFF command to at least one switching element in a phase in which it is determined that no overcurrent is flowing, A motor driving program that executes a process of outputting an OFF command to at least one switching element in a phase in which it is determined that an overcurrent is flowing.