Inverter Device

Abstract

This inverter device comprises a switching circuit that is connected to a motor having a plurality of phase windings, and a controller that controls the switching circuit. The switching circuit includes a plurality of series circuits of switch elements on the upstream side and switch elements on the downstream side along a direction for applying a direct current voltage, and the phase windings are connected to phase connection points of the switch elements of the series circuits. While sequentially switching a plurality of energization paths through which the current flows through the switch elements in a predetermined direction of the phase windings, the controller determines an abnormality of the switch elements in accordance with the state of a current flowing between the switching circuit and the motor and, before switching the energization paths, applies, to the phase windings, a reverse phase voltage for negating the current flowing between the switching circuit and the motor, through the switch elements.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an inverter device connected to a motor having multiple phase windings. [Background technology]

[0002] An inverter device connected to a motor having multiple phase windings includes a switching circuit that converts a DC voltage into an AC voltage by switching. The switching circuit includes multiple series circuits, each of which has an upstream switch element and a downstream switch element along the direction of application of the DC voltage. The interconnection points of the switch elements in these series circuits are connected to the respective phase windings of the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-187187 Summary of the Invention [Problem to be solved by the invention]

[0004] If an abnormality such as an open circuit or short circuit occurs in any of the switch elements of the switching circuit, the motor cannot be driven properly.

[0005] An object of the embodiments of the present invention is to provide an inverter device that can accurately and quickly detect an abnormality in the case where an abnormality occurs in each switch element of a switching circuit. [Means for solving the problem]

[0006] An inverter device according to an embodiment includes a switching circuit connected to a motor having multiple phase windings, and a controller for controlling the switching circuit. The switching circuit includes multiple series circuits each including an upstream switch element and a downstream switch element in a direction of DC voltage application, and each phase winding is connected to a connection point between the switch elements of the series circuits. The controller sequentially switches between multiple current paths through which current flows in a predetermined direction through each phase winding via each switch element, while determining an abnormality in each switch element based on the state of the current flowing between the switching circuit and the motor; and applies a negative-phase voltage to each phase winding via each switch element to cancel out the current flowing between the switching circuit and the motor before switching each current path. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the configuration of each embodiment. [Figure 2] FIG. 2 is a flowchart showing the control of the first embodiment. [Figure 3] FIG. 3 is a diagram showing current during a W-phase check operation in each embodiment. [Figure 4] FIG. 4 is a diagram showing a switching pattern and a change in current during a W-phase check operation in each embodiment. [Figure 5] FIG. 5 is a diagram showing current during a V-phase check operation in each embodiment. [Figure 6] FIG. 6 is a diagram showing current during a U-phase check operation in each embodiment. [Figure 7] FIG. 7 is a diagram showing current during an X-phase check operation in each embodiment. [Figure 8] FIG. 8 is a diagram showing current during a Z-phase check operation in each embodiment. [Figure 9] FIG. 9 is a diagram showing currents during a Y-phase check operation in each embodiment. [Figure 10] FIG. 10 is a diagram showing a switching pattern of each phase check operation in each embodiment. [Figure 11]FIG. 11 is a diagram showing the switching pattern and current changes during the check operation of each phase in each embodiment. [Figure 12] FIG. 12 is a diagram showing an example of a determination result in each embodiment. [Figure 13] FIG. 13 is a flowchart showing the control of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [1] First embodiment A first embodiment of the present invention will be described with reference to the drawings. In FIG. 1, M denotes a brushless DC motor (abbreviated as motor) used as a compressor motor for an air conditioner. It is composed of a stator with three phase windings Lu, Lv, and Lw star-connected around a neutral point C, and a rotor with a permanent magnet. The rotor rotates due to the interaction between the magnetic field generated by the phase windings Lu, Lv, and Lw and the magnetic field created by the permanent magnet. The unconnected ends of the phase windings Lu, Lv, and Lw are connected to the inverter device 1 of this embodiment via motor terminals 10. The winding style of motor M may also be a delta-connection.

[0009] The inverter device 1 includes input terminals P and N to which a DC voltage Vd is applied, a switching circuit 2 that receives the DC voltage Vd between the input terminals P and N and energizes and switches the energization of the phase windings Lu, Lv, and Lw, current sensors 3a, 3b, and 3c that detect the current (phase winding current) flowing in the current path between the switching circuit 2 and the phase windings Lu, Lv, and Lw, and a control unit 20 that controls the switching circuit 2.

[0010] The switching circuit 2 includes a series circuit of a switch element Tu on the upstream side and a switch element Tx on the downstream side in the direction of application of the DC voltage Vd, a series circuit of a switch element Tv on the upstream side and a switch element Ty on the downstream side in the direction of application of the DC voltage Vd, and a series circuit of a switch element Tw on the upstream side and a switch element Tz on the downstream side in the direction of application of the DC voltage Vd.

[0011] The unconnected end of the phase winding Lu is connected to the interconnection point (output terminal) Qa of the switch elements Tu and Tx via the motor terminal 10. The unconnected end of the phase winding Lv is connected to the interconnection point (output terminal) Qb of the switch elements Tv and Ty via the motor terminal 10. The unconnected end of the phase winding Lw is connected to the interconnection point (output terminal) Qc of the switch elements Tw and Tz via the motor terminal 10.

[0012] The control unit 20 controls the start and stop of the motor M through the switching circuit 2, detects the operating state of the motor M based on the phase winding current, etc., and controls each switch element of the switching circuit 2 according to the detection results, thereby operating the motor M at a target frequency. Furthermore, the control unit 20 determines whether there is an abnormality in the switching circuit 2 or in the motor M before starting the motor M. The control unit 20 includes a determination unit 20a, a first control unit 20b, and a second control unit 20c as its main functions for this determination.

[0013] The judgment unit 20a judges whether there is an abnormality in the switch elements Tu to Tz and whether there is an abnormality in the motor M according to the state of the current flowing between the switching circuit 2 and the motor M, while sequentially switching between a plurality of current paths (first to sixth current paths) through which current flows in a predetermined direction in the phase windings Lu, Lv, and Lw through the switch elements Tu to Tz of the switching circuit 2 for a fixed time t each.

[0014] Before the judgment unit 20a switches each of the above current paths (first to sixth current paths), the first control unit 20b applies a negative-phase voltage for canceling out the current flowing between the switching circuit 2 and the motor M to the phase windings Lu, Lv, and Lw through the switch elements Tu to Tz of the switching circuit 2 for a certain time t that is the same as the setting time of the current path that was set immediately before the switching.

[0015] The second control unit 20c executes the determination by the determination unit 20a before starting the motor M, and starts the motor M if the result of the determination shows that there is no abnormality, and does not start the motor M if the result of the determination shows that there is an abnormality.

[0016] The control executed by the controller 20 will be described with reference to the flowchart of FIG. (W phase check operation) When starting of the motor M is required (YES in S1), the controller 20 executes a W-phase check operation (S2). Specifically, the controller 20 supplies a pulsed gate signal that turns on the switch elements Tw, Tx, and Ty and turns off the switch elements Tu, Tv, and Tz for a certain period of time t, thereby establishing a first current path for W-phase check, along which current flows from the positive terminal P to the switch element Tw, interconnection point Qc, phase winding Lw, phase windings Lu and Lv, interconnection points Qa and Qb, switch elements Tx and Ty, and then to the negative terminal N, as indicated by the dashed lines and arrows in Fig. 3. Thereafter, the controller 20 monitors the state of the current flowing between the switching circuit 2 and the motor M using current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory.

[0017] Following the W-phase check operation, the controller 20 determines whether or not the current Iw flowing between the switching circuit 2 and the motor M, specifically the current Iw flowing through the W-phase to be checked, is less than the threshold value Is shown in FIG. 4 (S2a). The current Iw flowing through the W-phase has the largest value among the currents Iu to Iw flowing through the respective phase windings. In this embodiment, the current flowing between the switching circuit 2 and the motor M refers to the absolute value of the current, regardless of the direction of flow. If the current is less than the threshold value Is (YES in S2a), the controller 20 determines in a decision step S14 (described later) that some abnormality has occurred and that no current is flowing. In this case, because the current is sufficiently small, the zero reset operation (described later) for attenuating the current is not performed, and the process proceeds to the next V-phase check operation (S4). The reason for omitting the zero reset operation here is that if the zero reset operation were performed when the current was small, a current would flow in the reverse direction in the motor windings, making it impossible to accurately check the next phase current.

[0018] If the current is equal to or greater than the threshold value Is (NO in S2a), the controller 20 executes a 0 (zero) reset operation (S3) having a switching pattern opposite to that of the W-phase check operation. Specifically, the controller 20 applies a negative-phase voltage Vo to the phase windings Lu, Lv, and Lw to cancel the current flowing between the switching circuit 2 and the motor M, as shown by the solid arrows in Fig. 3, by supplying pulsed gate signals that turn on the switch elements Tu, Tv, and Tz and turn off the switch elements Tw, Tx, and Ty for a time period substantially equal to the set time (fixed time t) of the first current path. By applying this negative-phase voltage Vo, the current flowing between the switching circuit 2 and the motor M can be rapidly attenuated.

[0019] Figure 4 shows the switching between the W-phase check operation and the zero reset operation, and the resulting change in the current Iw flowing from the switch element Tw to the phase winding Lw. A "dead time + α" is provided between the W-phase check operation and the zero reset operation, and the current determination timing for determining whether the current is below the threshold value Is is set during this "dead time + α" period. Without the zero reset operation, it would normally take time tx for the current Iw to drop to near zero. However, by adding the zero reset operation, the time it takes for the current Iw to drop to near zero under normal conditions can be reduced to time ta, which is significantly shorter than time tx. In other words, adding the zero reset operation shortens the time required to check for abnormalities before starting the motor M. This allows the motor M to start operating quickly when normal.

[0020] Here, by setting the time for applying the negative-phase voltage Vo by the zero reset operation to a constant time t that is approximately the same as the set time for the current path by the immediately preceding check operation, the currents generated by each current flow cancel each other out, making it possible to reduce the current Iw to approximately "0." Note that if the current flow period by the zero reset operation is shorter than that of the check operation, the current Iw will not be able to be reduced to "0" by the time difference. Conversely, if the current flow period by the zero reset operation is longer than that of the check operation, the current Iw will exceed "0," and a current will flow in the determined direction from that of the check operation. After the 0 reset operation, the controller 20 proceeds to the next V-phase check operation (S4).

[0021] (V phase check operation) In the V-phase check operation (S4), the controller 20 supplies a pulsed gate signal that turns on switch elements Tv, Tx, and Tz and turns off switch elements Tu, Tw, and Ty for a certain time t, thereby setting up a second current path for V-phase check along which current flows from positive terminal P to switch element Tv, interconnection point Qb, phase winding Lv, phase windings Lu and Lw, interconnection points Qa and Qc, switch elements Tx and Tz, and then negative terminal N, as shown by the dashed line and arrows in Figure 5. Thereafter, the controller 20 monitors the state of the current flowing between the switching circuit 2 and the motor M using current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory.

[0022] When switching to this V-phase check operation, either a 0 reset operation is executed (S3) immediately before switching to cancel the current due to the W-phase check operation, or the current during the W-phase check operation is below the threshold value Is (YES in S2a), and the state of the current flowing between the switching circuit 2 and the motor M can be accurately monitored without being disturbed by the current due to the W-phase check operation.

[0023] Following the V-phase check operation, the controller 20 determines whether the current Iv, which indicates the largest value, is less than the threshold value Is (S4a). If the current is less than the threshold value Is (YES in S4a), some abnormality occurred in the V-phase check, and no current is flowing. The controller 20 determines this in a determination step S14, which will be described later. In this case, because the flowing current is sufficiently small, the controller 20 proceeds to the next U-phase check operation (S6) without performing a zero reset operation to attenuate the current.

[0024] If the current is equal to or greater than the threshold value Is (NO in S4a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the V-phase check operation (S5). Specifically, the controller 20 applies a negative-phase voltage Vo to the phase windings Lu, Lv, and Lw to cancel the current flowing between the switching circuit 2 and the motor M, as shown by the solid arrows in Fig. 5, by supplying pulsed gate signals that turn on the switch elements Tu, Tw, and Ty and turn off the switch elements Tv, Tx, and Tz for a time period substantially equal to the set time (fixed time t) of the second current path. This application of the negative-phase voltage Vo allows the current flowing between the switching circuit 2 and the motor M to rapidly attenuate. After the 0 reset operation, the controller 20 proceeds to the next U-phase check operation (S6).

[0025] (U phase check operation) In the U-phase check operation (S6), the controller 20 supplies pulsed gate signals that turn on the switch elements Tu, Ty, and Tz and turn off the switch elements Tv, Tw, and Tx for a certain period of time t, thereby turning on the switch elements Tu, Ty, and Tz and turning off the switch elements Tv, Tw, and Tx, thereby establishing a third current path through which current flows from the positive terminal P to the switch element Tu, interconnection point Qa, phase winding Lu, phase windings Lv and Lw, interconnection points Qb and Qc, switch elements Ty and Tz, and then to the negative terminal N, as shown by the dashed lines and arrows in Figure 6. Thereafter, the controller 20 monitors the state of the current flowing between the switching circuit 2 and the motor M using current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory.

[0026] When switching to this U-phase check operation, either the 0 reset operation of S5 is executed immediately before switching to cancel the current due to the V-phase check operation, or the current in the V-phase check operation is below the threshold value Is (YES in S4a), and the state of the current flowing between the switching circuit 2 and the motor M can be accurately confirmed without being disturbed by the current due to the V-phase check operation.

[0027] Following the U-phase check operation, the controller 20 determines whether the current flowing between the switching circuit 2 and the motor M is below the threshold value Is (S6a). If the current is below the threshold value Is (YES in S6a), some abnormality occurred in the U-phase check and no current is flowing, and the controller 20 determines the abnormality in a determination step (S14) described below. In this case, the flowing current is sufficiently small, so the controller proceeds to the next U-phase check operation (S8) without performing a zero reset operation to attenuate the current.

[0028] If the current is equal to or greater than the threshold value Is (NO in S6a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the U-phase check operation (S7). Specifically, the controller 20 supplies pulsed gate signals that turn on the switch elements Tv, Tw, and Tx and turn off the switch elements Tu, Ty, and Tz for a period of time substantially equal to the set time (fixed time t) of the third current path, thereby applying a negative-phase voltage Vo to the phase windings Lu, Lv, and Lw to cancel the current flowing between the switching circuit 2 and the motor M, as shown by the solid arrows in Fig. 6. Application of this negative-phase voltage Vo allows the current flowing between the switching circuit 2 and the motor M to rapidly attenuate. After the 0 reset operation, the controller 20 proceeds to the next X-phase check operation (S8).

[0029] (X-phase check operation) In the X-phase check operation (S8), the controller 20 supplies pulsed gate signals that turn on the switch elements Tv, Tw, and Tx and turn off the switch elements Tu, Ty, and Tz for a certain period of time t, thereby establishing a fourth current path through which current flows from the positive terminal P to the switch elements Tv and Tw, interconnection points Qb and Qc, phase windings Lv and Lw, phase winding Lu, interconnection point Qa, switch element Tx, and negative terminal N, as shown by the dashed lines and arrows in Figure 7. Thereafter, the controller 20 monitors the state of the current flowing between the switching circuit 2 and the motor M using current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory.

[0030] When switching to this X-phase check operation, either the 0 reset operation of S7 is executed immediately before the switch to cancel the current due to the U-phase check operation, or the current in the U-phase check operation is below the threshold value Is (YES in S6a), and the state of the current flowing between the switching circuit 2 and the motor M can be accurately monitored without being disturbed by the current due to the U-phase check operation.

[0031] Following the X-phase check operation, the controller 20 determines whether the current flowing between the switching circuit 2 and the motor M is below the threshold value Is (S8a). If the current is below the threshold value Is (YES in S8a), the controller 20 determines that the current is small and will not affect the determination of the next phase check, and proceeds to the next Z-phase check operation (S10).

[0032] If the current is equal to or greater than the threshold value Is (NO in S8a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the X-phase check operation (S9). Specifically, the controller 20 applies a negative-phase voltage Vo to the phase windings Lu, Lv, and Lw to cancel the current flowing between the switching circuit 2 and the motor M, as shown by the solid arrows in Fig. 7, by supplying pulsed gate signals that turn on the switch elements Tu, Ty, and Tz and turn off the switch elements Tv, Tw, and Tx for a time period substantially equal to the set time (fixed time t) of the fourth current path. By applying this negative-phase voltage Vo, the current flowing between the switching circuit 2 and the motor M can be rapidly attenuated. After the 0 reset operation, the controller 20 proceeds to the next Z-phase check operation (S10).

[0033] (Z-phase check operation) In the Z-phase check operation (S10), the controller 20 supplies pulsed gate signals that turn on the switch elements Tu, Tv, and Tz and turn off the switch elements Tw, Tx, and Ty for a certain period of time t, thereby establishing a fifth current path along which current flows from the positive terminal P to the switch elements Tu and Tv, interconnection points Qa and Qb, phase windings Lu and Lv, phase winding Lw, interconnection point Qc, switch element Tz, and negative terminal N, as shown by the dashed lines and arrows in Figure 8. Thereafter, the controller 20 monitors the state of the current flowing between the switching circuit 2 and the motor M using current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory.

[0034] When switching to this Z-phase check operation, either the 0 reset operation of S9 has been executed immediately before to cancel the current due to the X-phase check operation, or the current in the X-phase check operation is below the threshold value Is (YES in S8a), and the state of the current flowing between the switching circuit 2 and the motor M can be accurately monitored without being disturbed by the current due to the X-phase check operation.

[0035] Following the Z-phase check operation, the controller 20 determines whether or not the current flowing between the switching circuit 2 and the motor M is below the threshold value Is (S10a). If the current is below the threshold value Is (YES in S10a), the controller 20 determines that the current is small and will not affect the determination of the next phase check, and proceeds to the next Y-phase check operation (S12).

[0036] If the current is equal to or greater than the threshold value Is (NO in S10a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the Z-phase check operation (S11). Specifically, the controller 20 applies a negative-phase voltage Vo to the phase windings Lu, Lv, and Lw to cancel the current flowing between the switching circuit 2 and the motor M, as shown by the solid arrows in Fig. 8, by supplying a pulsed gate signal that turns on the switch elements Tw, Tx, and Ty and turns off the switch elements Tu, Tv, and Tz for a time period substantially equal to the set time (fixed time t) of the fifth current path. This application of the negative-phase voltage Vo allows the current flowing between the switching circuit 2 and the motor M to be rapidly attenuated. After the 0 reset operation, the controller 20 proceeds to the next Y-phase check operation (S12).

[0037] (Y phase check operation) In the Y-phase check operation (S12), the controller 20 supplies pulsed gate signals that turn on the switch elements Tu, Tw, and Ty and turn off the switch elements Tv, Tx, and Tz for a certain time t, thereby establishing a sixth current path through which current flows from the positive terminal P to the switch elements Tu and Tw, interconnection points Qa and Qc, phase windings Lu and Lw, phase winding Lv, interconnection point Qb, switch element Ty, and negative terminal N, as shown by the dashed lines and arrows in Figure 9. Thereafter, the controller 20 monitors the state of the current flowing between the switching circuit 2 and the motor M using current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory.

[0038] When switching to this Y-phase check operation, either the 0 reset operation of S11 has been executed immediately before, canceling the current due to the Z-phase check operation, or the current in the X-phase check operation is below the threshold value Is (YES in S10a), and the state of the current flowing between the switching circuit 2 and the motor M can be accurately monitored without being disturbed by the current due to the Z-phase check operation.

[0039] Following the Y-phase check operation, the controller 20 determines whether the current flowing between the switching circuit 2 and the motor M is less than the threshold value Is (S12a). If the current is less than the threshold value Is (YES in S12a), the controller 20 determines that the current is sufficiently small and proceeds to the next Y-phase check operation (S14).

[0040] If the current is equal to or greater than the threshold value Is (NO in S12a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the Y-phase check operation (S13). Specifically, the controller 20 applies a negative-phase voltage Vo to the phase windings Lu, Lv, and Lw to cancel the current flowing between the switching circuit 2 and the motor M, as shown by the solid arrows in Fig. 9, by supplying pulsed gate signals that turn on the switch elements Tv, Tx, and Tz and turn off the switch elements Tu, Tw, and Ty for a time period substantially equal to the set time (fixed time t) of the sixth current path. This application of the negative-phase voltage Vo allows the current flowing between the switching circuit 2 and the motor M to be rapidly attenuated. After the 0 reset operation, the controller 20 proceeds to the next determination process (S14).

[0041] The switching patterns for the check operations for each phase described above are shown in FIG.

[0042] (Determination process) In the determination process (S14), the controller 20 determines, based on the results of monitoring the current in the check operation for each phase, whether there is an abnormality in the switch elements Tu to Tz or in the motor M. An example of this determination result is shown in FIG.

[0043] When a current Iu flowing through the switch element Tu cannot be detected despite the setting of a current path via the switch element Tu, the controller 20 determines that an open fault has occurred in the switch element Tu. When a current Iv flowing through the switch element Tv cannot be detected despite the setting of a current path via the switch element Tv, the controller 20 determines that an open fault has occurred in the switch element Tv. Similarly, when a current Iw to Iz flowing through the switch elements Tw to Tz cannot be detected despite the setting of a current path via the switch elements Tw to Tz, the controller 20 determines that an open fault has occurred in the switch elements Tw to Tz.

[0044] If the controller 20 cannot detect the current Iu flowing through the switch element Tu despite the setting of a current path passing through the switch element Tu, and cannot detect the current Ix flowing through the switch element Tx despite the setting of a current path passing through the switch element Tx, the controller 20 determines that there is an abnormality in the phase winding Lu of the motor M, namely, a break in the wire, a so-called U-phase open fault.

[0045] If the controller 20 cannot detect the current Iv flowing through the switch element Tv despite the setting of a current path passing through the switch element Tv, and cannot detect the current Iy flowing through the switch element Ty despite the setting of a current path passing through the switch element Ty, the controller 20 determines that there is an abnormality in the phase winding Ly of the motor M, namely a broken wire, a so-called V-phase open fault.

[0046] If the controller 20 cannot detect the current Iw flowing through the switch element Tw despite the setting of a current path passing through the switch element Tw, and cannot detect the current Iz flowing through the switch element Tz despite the setting of a current path passing through the switch element Tz, the controller 20 determines that there is an abnormality in the phase winding Lz of the motor M, namely a broken wire, a so-called W-phase open fault.

[0047] If the current Iu to Iz flowing through the switch elements Tu to Tz cannot be detected despite the setting of a current path passing through the switch elements Tu to Tz, the controller 20 determines that there is a disconnection abnormality in the motor terminal 10 between the switching circuit 2 and the motor M.

[0048] If no abnormality is determined (YES in S15), that is, if it is determined to be normal, the controller 20 starts the motor M by switching the switching circuit 2 (S16).

[0049] If any abnormality is determined (NO in S15), the controller 20 does not start the motor M and keeps it stopped, and notifies the user of the abnormality, for example, by display or communication (S17). Here, the notification method may be, for example, one of three major categories shown in the leftmost column of FIG. 11: "No abnormality," "Element abnormality," and "Motor abnormality." This allows the repair worker to prepare a replacement inverter circuit board if the notification is "element abnormality," or to prepare a replacement motor if the notification is "motor abnormality." Furthermore, detailed abnormality determination results may be displayed in two columns on the right side of FIG. 11 in response to an operation, etc.

[0050] The magnitude of the current flowing during the phase check operation is significantly affected by the motor constants of motor M, particularly the R component of the phase winding. For this reason, it is preferable to set the fixed time t, which is the set time for the first to sixth current paths, taking into account the R component of the phase winding. Specifically, since the magnitude of the current is inversely proportional to the R component, the motor constants of motor M are measured in advance, and the larger the R component, the longer the fixed time t is set.

[0051] [2] Second embodiment In the phase check operation of the first embodiment, if the switch elements Tu to Tz and the motor M are normal, three currents Iu, Iv, and Iw flow between the switching circuit 2 and the phase windings Lu, Lv, and Lw. The three currents Iu, Iv, and Iw flow in different directions depending on the phase check operation, and also have different magnitudes depending on the phase check operation.

[0052] Taking this into consideration, in the second embodiment, the method of determining abnormality in the determination unit 20a is to use the results of monitoring the current during each phase check operation to determine whether there is an abnormality in the switch elements Tu to Tz and the motor M by comparing the magnitudes of the three currents Iu, Iv, and Iw that flow between the switching circuit 2 and the phase windings Lu, Lv, and Lw relatively.

[0053] Control executed by the controller 20 in this second embodiment will be described with reference to the flowchart of Fig. 2. Detailed description of the same controls as those in the first embodiment will be omitted.

[0054] (W phase check operation) In the W-phase check operation (S2), the controller 20 sets the first current path for W-phase check shown in Fig. 3 for a fixed time t, as in the first embodiment. This setting causes a current Iw to flow from the non-connected end of the phase winding Lw to the connected end (neutral point C), and currents Iv and Iu, which pass through the phase winding Lw, flow in the other direction from the connected end (neutral point C) of the phase windings Lv and Lu to the non-connected ends.

[0055] The directions and magnitudes of these three currents Iw, Iv, and Iu are shown in Fig. 12. The current Iw has a maximum value Imax, and of the currents Iv and Iu, for example, the current Iv has a minimum value Imin and the current Iu has an intermediate value Imid.

[0056] While monitoring the states of the currents Iw, Iv, and Iu with the current sensors 3a, 3b, and 3c, the controller 20 holds the monitoring results in the internal memory. In this monitoring, the controller 20 calculates a value Ia (= |Imax| + |Imid|) which is the sum of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the intermediate value Imid, and holds the calculation result in the internal memory.

[0057] Following the W-phase check operation, the controller 20 determines whether or not the sum value Ia is less than the threshold value Is (S2a). If the sum value Ia is less than the threshold value Is (Ia < Is) (YES in S2a), it is an abnormal state, and the subsequent 0 reset operation of the W phase is omitted, and the controller 20 proceeds to the next V-phase check operation (S4). When the sum value Ia is greater than or equal to the threshold value Is (NO in S2a), the controller 20 executes a 0 reset operation for the W-phase check operation (S3). After this 0 reset operation, the controller 20 proceeds to the next V-phase check operation (S4).

[0058] Note that different values are used for the threshold value Is in the first embodiment and the threshold value Is in this second embodiment. Since the second embodiment uses the sum value Ia of two current values, the threshold value Is in the second embodiment is set to a value larger than the threshold value Is in the first embodiment.

[0059] (V-phase check operation) In the V-phase check operation (S4), similar to the first embodiment, the controller 20 sets the second energization path for W-phase check shown in FIG. 5 for a fixed time t. By this setting, a current Iv flows from the non-connected end to the connected end (neutral point C) of the phase winding Lv, and currents Iw and Iu flow in the other direction from the connected end (neutral point C) of the phase windings Lw and Lu to the non-connected end through the phase winding Lv.

[0060] If an abnormality occurs, the currents Iv, Iw, and Iu fluctuate around 0, as shown in Fig. 12. The controller 20 monitors the states of the currents Iv, Iw, and Iu using the current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory. In this monitoring, the controller 20 calculates the sum Ia of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the median value Imid, and stores the calculation result in an internal memory.

[0061] Following the V-phase check operation, the controller 20 determines whether the sum value Ia is less than the threshold value Is (S4a). If the sum value Ia is less than the threshold value Is (YES in S4a), the controller 20 proceeds to the next U-phase check operation (S6). If the sum value Ia is equal to or greater than the threshold value Is (NO in S4a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the W-phase check operation (S5). After this zero reset operation, the controller 20 proceeds to the next U-phase check operation (S6).

[0062] (U phase check operation) In the U-phase check operation (S6), the controller 20 sets the third current path for U-phase check shown in Fig. 6 for a fixed time t, as in the first embodiment. This setting causes a current Iu to flow from the non-connected end of the phase winding Lu to the connected end (neutral point C), and currents Iw and Iv, which pass through the phase winding Lu, flow in the other direction from the connected ends (neutral point C) of the phase windings Lw and Lv to the non-connected ends.

[0063] The directions and magnitudes of these three currents Iu, Iw, and Iv are shown in Fig. 12. The current Iu has a maximum value Imax, and of the currents Iw and Iv, for example, the current Iw has a minimum value Imin and the current Iv has an intermediate value Imid.

[0064] The controller 20 monitors the states of the currents Iu, Iw, and Iv using the current sensors 3a, 3b, and 3c, and stores the monitoring results in an internal memory. In this monitoring, the controller 20 calculates the sum Ia of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the median value Imid, and stores the calculation result in the internal memory.

[0065] Following the U-phase check operation, the controller 20 determines whether the sum value Ia is less than the threshold value Is (S6a). If the sum value Ia is less than the threshold value Is (YES in S6a), the controller 20 proceeds to the next X-phase check operation (S8). If the sum value Ia is equal to or greater than the threshold value Is (NO in S6a), the controller 20 executes a zero reset operation having a switching pattern opposite to that of the U-phase check operation (S7). After this zero reset operation, the controller 20 proceeds to the next X-phase check operation (S8).

[0066] The processing up to this point is similar for the X-phase check operation (S8) through the Y-phase check operation (S12).

[0067] (Determination process) In the determination process (S14), the controller 20 determines whether there is an abnormality in the switch elements Tu to Tz and the motor M based on the results of monitoring the current in the check operation for each phase.

[0068] After checking each phase, the controller 20 calculates the sum (=|Imax|+|Imid|) of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the middle value Imid, and stores the calculation result in the internal memory.

[0069] In all of the above-described W-phase to Y-phase check operations, if the sum Ia of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the intermediate value Imid is greater than the threshold value Is, the controller 20 determines that there is no open circuit abnormality in the switch elements Tw, Tu, and that there is no abnormality in the phase windings Lw, Lu (YES in S15). In this case, the controller 20 starts the motor M by switching the switching circuit 2 (S16). At this time, it may also be possible to notify that "no abnormality" has occurred.

[0070] 12, the sum Ia (=|Imax|+|Imid|) of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the intermediate value Imid in the V-phase check operation is less than the threshold value Is. In this case, in the determination (S14), the controller 20 determines that an open abnormality has occurred in the switch element Tv or that an abnormality has occurred in the phase winding Lv, and in the subsequent determination step S15, it is determined that "an abnormality has occurred" (NO in S15). In this case, the controller 20 does not start the motor M but keeps it stopped, and notifies the outside of the content of the abnormality, for example, by displaying or communicating (S17).

[0071] As described above, by viewing the results of monitoring the current during each phase check operation by relatively comparing the magnitudes of the three currents Iu, Iv, and Iw flowing between the switching circuit 2 and the phase windings Lu, Lv, and Lw, even in situations where the current during each phase check operation is not particularly large due to the state of the phase windings of the motor M, the sum of the absolute values ​​of the current values ​​of multiple phase windings can be used for judgment, thereby improving the accuracy of abnormality judgment for the switch elements Tu to Tz and the motor M and making an appropriate judgment.

[0072] In other words, if the current during the check operation for each phase does not become very large due to the state of the phase windings of the motor M, it may be difficult to properly determine an abnormality by comparing the current for one phase with the threshold value Is, but such a problem does not occur.

[0073] Although the sum (=|Imax|+|Imid|) of the absolute value |Imax| of the maximum value Imax and the absolute value |Imid| of the intermediate value Imid is compared with the threshold value Is in the above configuration, the sum Ia (=|Imax|+|Imin|) of the absolute value |Imax| of the maximum value Imax and the absolute value |Imin| of the minimum value Imin may be compared with the threshold value Is. Furthermore, the total value of the three current values ​​(=|Imax|+|Imid|+|Imin|) may be compared with the threshold value Is.

[0074] [3] Third embodiment The third embodiment differs from the first embodiment in the processing of the first control unit 20b of the controller 20. The other configurations are the same as those of the first embodiment. Before switching each current path (first to sixth current paths), the first control unit 20b applies a negative-phase voltage for canceling the current flowing between the switching circuit 2 and the motor M to the phase windings Lu, Lv, and Lw through the switch elements Tu to Tz of the switching circuit 2 only when the current flowing between that switching circuit 2 and the motor M is equal to or greater than a threshold value, and only for a period until the current flowing between that switching circuit 2 and the motor M becomes zero or close to zero. In this third embodiment, unlike the first and second embodiments, the duration of the zero reset operation is not a fixed constant time t, but is changed to an appropriate value depending on the state. The control executed by the controller 20 is shown in the flowchart of FIG. 13. (W phase check operation) After executing the W-phase check operation in S2, if the current flowing between the switching circuit 2 and the motor M is equal to or greater than the threshold value Is (NO in S2a), the controller 20 starts a zero reset operation (S3) and monitors whether the current flowing between the switching circuit 2 and the motor M has attenuated to or near zero (S3a). Here, the current flowing between the switching circuit 2 and the motor M is preferably the largest phase current value, i.e., |Imax|, but is not limited to this and other phase currents can also be used.

[0075] If the current has not decayed to zero or close to zero (NO in S3a), the controller 20 continues the zero reset operation in S3. If the current has decayed to zero or close to zero (YES in S3a), the controller 20 proceeds to the next V-phase check operation (S4).

[0076] If the current flowing between the switching circuit 2 and the motor M is less than the threshold value Is (YES in S2a), the controller 20 determines that the current flowing between the switching circuit 2 and the motor M is small, and proceeds to the next V-phase check operation (S4) without performing the 0 reset operation in S3.

[0077] (V phase check operation ~ Y phase check operation) The subsequent V-phase to Y-phase check operations also include attenuation determination processes S5a, S7a, S9a, S11a, and S13a, which are the same as S3a in the W-phase check operation. These determination processes are the same as each other, so a description thereof will be omitted.

[0078] [4] Variation In the above embodiments, the phase check operation is performed in the order of W phase, V phase, U phase, X phase, Z phase, and Y phase, but the order is not limited thereto.

[0079] In each of the above embodiments, the state of the current flowing between the switching circuit 2 and the motor M is detected by the current sensors 3a, 3b, and 3c. However, as shown by the dashed lines in FIG. 1, it is also possible to insert and connect shunt resistors Ra, Rb, and Rc into the current paths of the switch elements Tx, Ty, and Tz, and detect the presence or absence of current in each current path based on the voltage generated across these shunt resistors Ra, Rb, and Rc.

[0080] Furthermore, the above-described embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. These embodiments and modifications can be embodied in various other forms, and various omissions, rewritings, and modifications can be made without departing from the spirit of the invention. These embodiments and modifications are included within the spirit of the invention, and are also included in the scope of the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0081] 1... inverter device, 2... switching circuit, 3a, 3b, 3c... current sensors, M... motor, 20... controller, 20a... determination unit, 20b... first control unit, 20c... second control unit.

Claims

1. An inverter device connected to a motor having a plurality of phase windings, a switching circuit including a plurality of series circuits each including an upstream switch element and a downstream switch element in a direction in which a DC voltage is applied, the respective phase windings being connected to interconnection points of the respective switch elements of the series circuits; a controller for controlling the switching circuit; Equipped with The controller a plurality of current paths through which current flows in a predetermined direction through each of the phase windings through each of the switch elements, and determines whether or not there is an abnormality in each of the switch elements according to the state of the current flowing between the switching circuit and the motor; before switching each of the current paths, a negative-phase voltage for canceling the current flowing between the switching circuit and the motor is applied to each of the phase windings through each of the switch elements; An inverter device characterized by:

2. the controller applies, before switching each of the current paths, a negative-phase voltage for canceling the current flowing between the switching circuit and the motor to each of the phase windings through each of the switch elements for a period of time equal to a set time of the current path set immediately before the switching; The inverter device according to claim 1 .

3. the controller applies a negative-phase voltage for canceling a current flowing between the switching circuit and the motor to each phase winding through each switch element before switching each current path, only when the current flowing between the switching circuit and the motor is equal to or greater than a threshold value; The inverter device according to claim 1 or 2.

4. the controller applies, before switching each of the current paths, a negative-phase voltage for canceling out a current flowing between the switching circuit and the motor to each of the phase windings through each of the switch elements only when the current flowing between the switching circuit and the motor is equal to or greater than a threshold value, until the current flowing between the switching circuit and the motor becomes zero or close to zero; The inverter device according to claim 1 or 2.

5. The controller executes the determination before starting the motor, and starts the motor if the result of the determination shows that there is no abnormality, and does not start the motor if the result of the determination shows that there is an abnormality. The inverter device according to claim 1 .

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