JP2013132099A - Three-phase motor drive controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect open phase such as breaking in a three-phase motor regardless of states before start and during drive.SOLUTION: Before starting the three-phase motor, an operation of supplying current to a phase and absorbing current from the other two phases is performed for each phase and the presence or absence of abnormality is determined by determining whether direct current flows from an inverter circuit to a DC/DC conversion circuit for each operation (S2, S3). After starting, the above described direct current is continuously detected when drive current is supplied from the inverter circuit to the motor so as to rotate the three-phase motor and the presence and absence of the abnormality is determined by determining the number of saw tooth wave like peak which appears six in one rotational period of the motor not in an open phase state and reduces to two during the open phase (S5, S6). When the abnormality is determined in S6, the drive of the motor is stopped once and an abnormality notification is performed by confirming phase in the open phase state by performing a breakage detection processing same as in S2 (S7 to S9, S12).

Description

  The present invention relates to a three-phase motor drive control device for driving a three-phase motor, and more specifically, has a disconnection detection function for detecting an internal wiring of the three-phase motor and a disconnection of a distribution line connecting the device and the three-phase motor. The present invention relates to a three-phase motor drive control device.

  For example, in a semiconductor manufacturing apparatus such as a sputtering apparatus, a turbo molecular pump is used to create a high vacuum atmosphere in the chamber. In the turbo molecular pump, a three-phase motor capable of high-speed rotation of up to about 800 Hz or more is used as a pump motor. In such a three-phase motor, when the internal winding or the distribution line connecting the motor and the drive control device is broken, the motor does not operate and does not function as a vacuum pump.

  Various techniques for detecting the disconnection as described above, that is, the phase failure of the three-phase output are conventionally known. For example, on the premise that the rotational speed of a three-phase motor is increased to a certain speed during normal use, it is detected whether the speed has increased to a predetermined rotational speed when a predetermined time has elapsed from the start point. As a result, there is an apparatus that can detect a disconnection. However, since the rotational speed of the turbo molecular pump as described above increases considerably slowly, it takes time to increase the rotational speed to a predetermined rotational speed even if the motor is normal. For this reason, there is a problem that it takes time until the detection result of the presence / absence of disconnection is obtained, and when there is a disconnection, the time from the start up until then is wasted.

  In the device described in Patent Document 1, AC current detection means is provided on each of the three-phase output lines of the inverter circuit, and the presence or absence of disconnection is determined based on the detection signal. However, it is necessary to use an expensive current transformer having an iron core and a winding wound with a copper wire as an alternating current detection means, and the current transformer must be provided for each of the three phases, so the cost is considerably high. There is a problem of becoming something.

  In the device described in Patent Document 2, prior to starting the three-phase motor, the switching element on the high voltage side of any one phase (for example, R phase) of the three-phase bridge configuration and the other two phases (for example, S phase) And the other three switching elements are turned off, and a DC voltage is applied from the DC / DC conversion circuit to the three-phase inverter circuit in this state. The direct current flowing through is detected. If a current flows at this time, it is determined that there is no phase loss in the phase in which the switching element on the high voltage side is turned on. Then, the presence / absence of a phase failure is determined for all three phases, and if there is even one phase failure, the activation of the three-phase motor is stopped and an abnormality is reported. In this disconnection detection method, disconnection can be reliably detected without using a current transformer for AC current detection.

  However, in this method, since it is necessary to stop the three-phase AC drive for the three-phase motor during the disconnection detection operation, it is not possible to detect the disconnection continuously during the rotational drive of the three-phase motor. The semiconductor manufacturing apparatus using the above-described turbo molecular pump is often operated unattended, but when the operator is unaware of the abnormalities in the motor rotation and the vacuum level is reduced, a large loss occurs. It is necessary to take measures to prevent such a situation from occurring.

JP 2001-309669 A JP 2007-143244 A

  The present invention has been made to solve the above-mentioned problems. The main object of the present invention is to provide an internal wiring of the three-phase motor and the device substantially continuously during the rotational driving of the three-phase motor at a low cost. An object of the present invention is to provide a three-phase motor drive control device capable of accurately detecting the occurrence of disconnection without delay by detecting disconnection of a distribution line connecting the three-phase motor.

In order to solve the above-mentioned problems, the present invention includes an AC / DC converting means for converting commercial AC power into DC power, and switching connected in a three-phase bridge to convert the DC power into three-phase AC power. Three-phase drive current is supplied to the three-phase motor connected to the inverter means by controlling on / off of the inverter means having the elements and the switching elements on the high voltage side and the low voltage side of each phase of the inverter means A control means for operating the three-phase motor, and a three-phase motor drive control device comprising:
a) a current detector for detecting a direct current flowing through the inverter means by a DC voltage applied to the inverter means; and a direct current by the current detector while supplying a three-phase drive current to the three-phase motor. The presence or absence of a phase failure is detected by directly or indirectly detecting a change in the number of current waveform peaks that repeatedly appear during a period corresponding to one rotation of the three-phase motor based on the detection result. A first disconnection detection means including a driving phase loss determination unit for determining
b) With no three-phase drive current supplied to the three-phase motor, turn on any one-phase high-voltage switching element included in the inverter means and turn on the other two-phase low-voltage switching elements. In addition, the driving of the switching elements according to the driving pattern of turning off the other switching elements is sequentially executed for each phase, or the high voltage side switching elements and the low voltage side of the different phases included in the inverter means Disconnection detection control unit that sequentially executes driving of the switching elements according to the drive pattern of turning on the other switching elements and turning off the other switching elements for two or more drive patterns, and the disconnection detection control unit Each time the switching element is turned on / off with a different drive pattern, Ri determines whether current is flowing, and non-driving time of phase failure determination section for determining that there is a phase loss when there are drive pattern no current flows, and a second disconnection detecting means including,
And when the three-phase motor is supplied with a three-phase drive current and the first disconnection detecting means determines that there is a phase failure, the rotational drive of the three-phase motor is temporarily stopped. The second disconnection detection means determines whether or not there is an open phase, thereby detecting the internal wiring of the three-phase motor and the disconnection of the distribution line to the three-phase motor.

  That is, the three-phase motor drive control device according to the present invention includes first disconnection detection means for detecting a phase failure due to disconnection or the like in parallel with the drive of the three-phase motor while being rotationally driven. And a second disconnection detecting means capable of accurately detecting a phase failure in a state in which the phase motor is not rotationally driven and capable of detecting a phase in which the phase failure has occurred. And during acceleration or steady operation of the three-phase motor, the first disconnection detecting means repeatedly determines the presence or absence of the phase loss, and if it is determined that there is a phase loss, the rotational drive of the three-phase motor is temporarily stopped, The presence or absence of a phase failure is determined by the second disconnection detection means. If the second disconnection detecting means determines that there is no phase loss, the rotational drive of the three-phase motor is resumed. Even if the rotation drive of the three-phase motor is stopped, the rotation of the motor itself does not stop immediately, but is rotated by inertia. In particular, there is almost no influence from temporarily stopping the driving of the three-phase motor.

  When three-phase AC power is supplied to the three-phase motor by the inverter means and the motor is driven, six current waveform peaks appear during a period corresponding to one rotation of the three-phase motor. On the other hand, if one phase is lost due to disconnection or the like, for example, the state is substantially the same as that of single-phase driving, so the peak of the current waveform that appears during a period corresponding to one rotation of the three-phase motor is reduced to two. Therefore, in the first disconnection detection means, the driving phase loss determination unit detects the decrease in the number of peaks repeatedly appearing in the current waveform as described above or a phenomenon that occurs with the decrease, thereby generating a defect. Recognize that.

  More specifically, the driving phase loss determination unit determines a predetermined timing at which a peak of the current waveform appears when there is no phase loss (that is, in a normal state) during a period corresponding to a predetermined rotation of the three-phase motor. To obtain a signal reflecting the current value of the direct current, compare it with a signal for the same timing obtained when going back a predetermined time, and determine the presence or absence of phase loss based on the comparison result be able to. Note that the change in the DC current during the rotational driving of the three-phase motor is synchronized with the ON / OFF control signal of the switching element supplied from the control means to the inverter means, so that the control means sets the predetermined timing. Can do. Note that, from the principle of phase loss determination in the present invention, the predetermined rotation is typically one rotation, but is not necessarily limited to one rotation, for example, 1/2 rotation.

  In the above configuration, since the signal detected by the current detection unit can be digitally processed after being converted into a digital value, it can be processed by a general-purpose microcomputer. As a result, the cost can be reduced, and it is possible to easily cope with a change in conditions for the phase loss determination.

  On the other hand, the determination of the presence or absence of phase loss by the second disconnection detection means performed in a state in which the three-phase motor is not rotationally driven uses the method described in Patent Document 2 above. That is, a direct current is supplied to the three-phase motor with two or more different drive patterns, and it is determined whether the direct current flows by one phase or two phases. Accordingly, it is possible to identify not only whether or not a phase failure has occurred but also to identify the number of phases and the phase in which the phase failure has occurred and to notify the user.

  According to the three-phase motor drive control device of the present invention, the wire breaks almost continuously without affecting the rotation during the steady operation of the three-phase motor or during the course of increasing the rotational speed until the steady operation is reached. Can be detected. Accordingly, it is possible to quickly and surely detect a disconnection that occurs during the rotation of the three-phase motor, and to stop driving or issue a warning notification. In addition, even when it is erroneously detected that a disconnection is detected in the disconnection detection process while rotating the three-phase motor, the disconnection is more accurate when the drive is stopped. Since the presence / absence of a phase loss is reconfirmed by the detection process, it is possible to avoid undesired motor shutdown due to erroneous detection. Furthermore, when a phase failure occurs, the location and number of the phases are also determined, so that it is possible to provide useful information to the user regarding the failure. As a result, if the three-phase motor drive control device according to the present invention is used to drive a vacuum pumping turbomolecular pump of a semiconductor manufacturing apparatus, the risk of a vacuum drop due to disconnection can be detected quickly and reliably. It is possible to take appropriate measures such as stopping the service without delay.

  Since the second disconnection detecting means can detect the disconnection in a state where the three-phase motor is not rotationally driven, preferably, when the three-phase motor is activated, the second disconnection detecting means prior to the start of the open-circuit detection by the second disconnection detecting means. It is preferable to perform the presence / absence determination and start the three-phase motor if it is determined that there is no phase loss. As a result, if there is already a disconnection at the time of start-up, the disconnection can be detected before the start-up, so it is possible to speed up the response such as replacing the motor or repairing the disconnection point by eliminating unnecessary start-up. it can.

The block block diagram of the principal part of the three-phase motor drive control apparatus which is one Example of this invention. The control flowchart at the time of the three-phase motor drive in the three-phase motor drive control apparatus of a present Example. Schematic which shows the change of the rotational speed of a three-phase motor. The functional block diagram implement | achieved at the time of a 1st disconnection detection program execution. The figure which shows the actual example of the direct current detection signal at the time of normality and abnormality (one phase missing phase). The flowchart of a 2nd disconnection detection process. Explanatory drawing of the control method at the time of a 2nd disconnection detection process. The figure which shows the flow of the direct current at the time of the 2nd disconnection detection process in a three-phase inverter circuit and a three-phase motor. The figure which shows the time change of the direct current supplied to a three-phase inverter circuit. Explanatory drawing of the control method at the time of the 2nd disconnection detection process in the three-phase motor drive control apparatus which is another Example of this invention. The figure which shows the flow of the electric current at the time of the disconnection detection process shown in FIG. The block block diagram of the disconnection detection part in the three-phase motor drive control apparatus which is another Example of this invention. The wave form diagram for demonstrating operation | movement of the disconnection detection part of FIG.

  Hereinafter, a three-phase motor drive control apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the main part of the three-phase motor drive control device of this embodiment.

  As a schematic configuration of the three-phase motor drive control device of the present embodiment, AC power supplied from a single-phase 200V (or 100V) commercial AC power supply 1 is converted into DC power by a rectifier circuit 2, and further DC / In the DC conversion circuit 3, it is converted into DC power having a predetermined voltage. This DC power is converted into AC power supplied to the R, S, and T phases of the three-phase motor M by the three-phase inverter circuit 4.

  More specifically, the rectifier circuit 2 includes a diode bridge circuit and a smoothing electrolytic capacitor (not shown), and outputs a predetermined DC voltage. In the DC / DC converting circuit 3, a switching element 31 such as a power FET is connected in series to the primary winding of the transformer 32, and when the switching element 31 is turned on by a control signal from the control unit 5 described later, the primary of the transformer 32. A direct current flows through the winding and a voltage is generated across the secondary winding. This voltage is output through a circuit including diodes 33 and 34, a capacitor 35, and an output voltage detection unit 37 including two resistors connected in series. Further, a shunt resistor 36 for detecting a direct current is provided on the line on the low voltage side of the direct current / direct current conversion circuit 3.

  The three-phase inverter circuit 4 includes six switching elements 41, 42, 43, 44, 45, 46 such as power FETs and the like based on instructions from the control unit 5 and a switching unit in which a three-phase bridge connection is made. And an inverter driving unit 47 that independently turns on or off 41 to 46, and in each of the R phase, S phase, and T phase, switching elements 41, 43, 45 on the high voltage side and switching element 42 on the low voltage side. , 44 and 46 are connected to the respective phase terminals of the three-phase motor M through three distribution lines.

  The control unit 5 that controls the DC / DC conversion circuit 3 and the three-phase inverter circuit 4 is configured with a microcomputer including a CPU 51 as a center. The CPU 51 executes predetermined processing in accordance with a control program stored in a storage device such as a ROM. Here, the CPU 51 is broadly divided into a drive control program 52, a first disconnection detection program 53, and a second disconnection detection program 54. , And an abnormal time response program 55. The drive control program 52 is a program for general operations such as activation of the three-phase motor M and steady operation. On the other hand, the first and second disconnection detection programs 53 and 54 are programs for executing the disconnection detection processing characteristic of the present embodiment, and the abnormality response program 55 is an operation of the apparatus when a disconnection is detected. It is a program that governs. Further, the control unit 5 is connected to a display 6 for displaying an operation state and the like.

  The controller 5 detects the potential at both ends of the shunt resistor 36, and detects the value of the current i flowing through the shunt resistor 36 as a voltage value based on the potential difference. Further, the DC voltage applied to the three-phase inverter circuit 4 is recognized based on the voltage value input by the output voltage detection unit 37.

  Hereinafter, motor drive control including characteristic disconnection detection processing in the three-phase motor drive control device of the present embodiment will be described. FIG. 2 is a control flowchart for driving a three-phase motor in the three-phase motor drive control apparatus of this embodiment, and FIG. 3 is a schematic diagram showing changes in the rotational speed of the three-phase motor.

  When an activation instruction for the three-phase motor M is given by operating a switch (not shown) or the like (step S1), the controller 5 executes a second disconnection detection process according to the second disconnection detection program 54 prior to activation (step S2). . The second disconnection detection process is different from the first disconnection detection process described later, and detects disconnection in a state where the three-phase inverter circuit 4 is not driven so that the three-phase motor M rotates.

  Hereinafter, the second disconnection detection process will be described according to a detailed control flowchart shown in FIG. When the second disconnection detection process is started, first, disconnection detection flags F1, F2, and F3, which will be described later, are reset to “0” (step S201), and according to the R-line disconnection detection drive pattern (FIG. 7A). A control signal is sent to the inverter drive unit 47 so that each of the switching elements 41 to 46 is turned on or off (step S202). Specifically, as shown in FIG. 7A, the R-phase high-voltage side switching element 41 and the S-phase and T-phase low-voltage side switching elements 44 and 46 are turned on, and the other three switching elements. 42, 43 and 45 are turned off.

  As described above, when the respective switching elements 41 to 46 are turned on / off and a predetermined DC voltage is applied from the DC / DC conversion circuit 3 to the three-phase inverter circuit 4, the three-phase inverter circuit 4 and the three-phase motor M are applied. The current should flow through the path as shown in FIG. In this case, even if there is a break in one of the S-phase and T-phase distribution lines, a current i flows through the shunt resistor 36 because a current flows through the other of the S-phase and T-phase distribution lines. In other words, if the current i does not flow through the shunt resistor 36, it is a case where the R-phase distribution line is disconnected.

  Therefore, the controller 5 determines whether or not the current i is flowing through the shunt resistor 36 in a state where the R-line break detection driving pattern is set and the three-phase motor M is energized (step S203). If it is determined that the current is flowing, the process proceeds to step S205 as it is. On the other hand, when it is determined in step S203 that the current i is not flowing, the R-line disconnection flag F1 indicating disconnection of the R-phase distribution line (referred to as R-line) is set to “1” (step S204). Above, it progresses to step S205.

  Note that if an excessive direct current exceeding the maximum rating flows through the windings of the three-phase motor M, there is a risk of burning. Therefore, instead of suddenly applying a large DC voltage to the three-phase inverter circuit 4 with the switching elements 41 to 46 of the three-phase inverter circuit 4 turned on and off as described above, the voltage as shown in FIG. The value is gradually increased to the specified value. This is achieved by appropriately changing the duty ratio of the on / off control signal given to the switching element 31 by the control unit 5.

  When there is no disconnection in any of the distribution lines, the direct current gradually increases as shown in FIG. 9 along with the change in the applied voltage as described above, but the maximum value is the maximum rated current of the three-phase motor M. It is necessary to keep it smaller. Here, considering that various rated motors are used as the three-phase motor M, the maximum value of the direct current is set to about 1 [A] so that the maximum rating is smaller than the smallest motor. Of course, this value can be changed as appropriate, and if the current flowing when applying a DC voltage does not exceed the maximum rating from the resistance value of the winding of the motor M, etc. There is no need to gradually increase the voltage.

  In step S206, a control signal is sent to the inverter drive unit 47 so that the switching elements 41 to 46 are turned on or off according to the S-line break detection drive pattern as shown in FIG. At this time, a current should flow through the three-phase inverter circuit 4 and the three-phase motor M through a path as shown in FIG. 8B. If the S-phase distribution line is broken, the current i flows through the shunt resistor 36. Does not flow. Therefore, the controller 5 determines whether or not the current i is flowing through the shunt resistor 36 in a state where the S-line break detection drive pattern is set and the three-phase motor M is energized (step S206). If it is determined that it is flowing, the process proceeds to step S208 as it is. On the other hand, when it is determined in step S206 that the current i is not flowing, the S-line disconnection flag F2 indicating disconnection of the S-phase distribution line (referred to as S-line) is set to “1” (step S207). Above, it progresses to step S208.

  In step S208, a control signal is sent to the inverter drive unit 47 so that the switching elements 41 to 46 are turned on or off according to the T-line break detection drive pattern as shown in FIG. At this time, a current should flow through the three-phase inverter circuit 4 and the three-phase motor M through a path as shown in FIG. 8C. If the T-phase distribution line is disconnected, the current i flows through the shunt resistor 36. Does not flow. Therefore, the controller 5 determines whether or not the current i is flowing through the shunt resistor 36 in a state where the T-line break detection driving pattern is set and the three-phase motor M is energized (step S209). If it is determined that the current is flowing, the process proceeds to step S211 as it is. On the other hand, if it is determined in step S209 that the current i is not flowing, the T-line disconnection flag F3 indicating disconnection of the T-phase distribution line (referred to as T-line) is set to “1” (step S210). Above, it progresses to step S211.

  After completing the detection of disconnection of each phase of the R phase, S phase, and T phase as described above, the R line disconnection flag F1, the S line disconnection flag F2, and the T line disconnection flag F3 are all “0” in the initial state. (Step S211), if all are “0”, it is determined that there is no disconnection (Step S212), and it is determined that at least one of the flags F1, F2, and F3 is “1”. Then, it is determined that there is a disconnection (step S213).

  When the disconnection is detected only with any one of the disconnection detection drive patterns, as described above, it is determined whether the disconnection occurs in the R phase, the S phase, or the T phase. On the other hand, when two-phase (or all three-phase) distribution lines are disconnected at the same time, no current flows through the three-phase motor M in any disconnection detection drive pattern. Thereby, it is also possible to determine whether the disconnection is one phase or more than two phases.

  In addition, the time for supplying a direct current to the three-phase motor M for each phase may be at most about 100 ms, and the result of the presence or absence of disconnection of all the three-phase distribution lines can be found within 1 second at the longest. Therefore, even if the disconnection detection process is executed before starting, the starting time of the three-phase motor M is substantially not affected. Moreover, in order to detect that there is a disconnection (open phase) in any of R, S, and T phases, it is not necessary to execute the three disconnection detection drive patterns as described above. As will be described later, it is sufficient to execute two disconnection detection drive patterns.

  As a result of executing the second disconnection detection process in step S2 in FIG. 2 as described above, if it is determined that there is an abnormality (there is a disconnection) (Yes in step S3), the control unit 5 does not start ( In step S11), the display 6 notifies the abnormality (step S12). Of course, the user may be alerted by a buzzer sounding at the same time as the display. On the other hand, when it is determined in step S3 that there is no abnormality (no disconnection), driving of the three-phase motor M is started, and a three-phase drive current is supplied from the three-phase inverter circuit 4 to the three-phase motor M (step S4). As a result, as shown in FIG. 3, the rotational speed of the three-phase motor M gradually increases. A period indicated by i in FIG. 3 is a period during which the process of step S2 is executed.

  During the rotation drive of the three-phase motor M, the control unit 5 executes the first disconnection detection process according to the first disconnection detection program 53 (step S5). FIG. 4 is a functional block diagram realized when the first disconnection detection program 53 is executed, and FIG. 5 is a diagram showing an example of a DC current detection signal at the time of normality and abnormality (one phase missing phase).

When drive current is supplied from the three-phase inverter circuit 4 to the three-phase motor M, if the circuit is in a normal state with no disconnection, that is, no phase loss, the three-phase motor M rotates once as shown in FIG. In the DC current detection signal obtained by the shunt resistor 36 during the period, six peaks (peaks P _{1 to} P ₆ ) having a substantially triangular shape (sawtooth shape) appear. Since the direct current flowing through the shunt resistor 36 is due to the alternating current supplied to the three-phase motor M when each of the switching elements 41 to 46 in the three-phase inverter circuit 4 is turned on, the position where the peak of the current waveform occurs Is synchronized with an on / off drive signal supplied from the inverter drive unit 47 to each of the switching elements 41 to 46 under the instruction of the control unit 5. Therefore, when the driving state is normal, if the on / off drive signal that is, read the DC current detection signal at a predetermined timing synchronized with the control signal from the control unit 5, for example of the peak P ₁ to P ₆ The maximum value (peak value) can be acquired. Further, if the AC voltage from the commercial AC power supply 1 is substantially constant, there is almost no fluctuation in the peak value of the DC current detection signal during each rotation period of the three-phase motor M. This can also be confirmed from the actually measured waveform shown in FIG.

On the other hand, when one phase of the three-phase motor M is lost, the motor M is driven substantially in a single phase, and as shown in FIG. Two substantially triangular peaks (peaks P _A and P _B ) appear in the DC current detection signal. Since this phenomenon is independent of the rotational speed of the three-phase motor M, the same phenomenon occurs not only at a constant rotational speed but also during acceleration in which the rotational speed is increasing. When the first disconnection detection process is executed, the disconnection is detected by capturing the decrease in the number of substantially triangular peaks appearing in the DC current detection signal during one rotation of the three-phase motor M as described above.

  As in the example described later, it is also possible to directly determine whether or not the number of peaks has decreased, but in this example, it is indirect by recognizing that there is no peak at the position (timing) where the peak should occur. The presence or absence of a decrease in the number of peaks is determined. Specifically, as shown in FIG. 4, the functional block realized by executing the first disconnection detection program 53 is a one-rotation period of the three-phase motor M (strictly speaking, the control unit 5 uses the three-phase Peak value determination units 100A to 100F respectively corresponding to six peaks generated during a period in which the motor M is controlled to rotate once, that is, a period corresponding to one rotation, and each peak value determination unit 100A to 100A A disconnection determination unit 110 that receives an output of 100F and finally determines whether or not it is a disconnection, and an abnormality (NG) determination result in the disconnection determination unit 110 is realized by executing the abnormality response program 54. Is input to the abnormality processing unit 111. Each of the peak value determination units 100A to 100F includes a delay register unit 101 having a predetermined number of stages, and a comparator unit 102 that compares an output value of the register unit 101 with an input value.

In each of the peak value determination units 100A to 100F, the delay register unit 101 has a timing at which the above-described peak value can be taken in the DC current detection signal (current value data) converted into a digital value by an A / D converter (not shown). Newly captures and shifts the current value data that has already been captured. Accordingly, every time the three-phase motor M makes one revolution, new current value data is taken in, and the oldest peak value, that is, the peak value taken in the past by a predetermined number of stages, is discharged. 4, for example, the delay register unit 101 of the peak value determining section 100A captures the new peak value at the timing that can capture the peak value of the peak P ₁ in FIG. 5 (a), the delay of the peak value determination section 100F use register unit 101 captures the new peak value at the timing that can capture the peak value of the peak P _6.

The comparator unit 102 compares the newly acquired peak value with the peak value previously acquired by a predetermined number of stages, and outputs a determination result as to whether or not they match. However, it is unlikely that two peak values that are separated by a certain amount of time will coincide completely when considering a certain degree of fluctuation in the AC voltage, etc. Therefore, if the difference is within a predetermined allowable range, they will agree. Shall be deemed to be present. As a result, for all six peaks P _{1 to} P ₆ that should appear during one rotation period, it is determined whether or not the newly obtained peak value matches or does not coincide with the peak value obtained at a predetermined time. Will be. Note that when the rotational speed of the three-phase motor M is changing, the time of one rotation period itself changes, but the timing at which the peak value is taken into the delay register unit 101 also changes accordingly. The comparison itself has no effect.

  Ideally, in a normal state, the peak values of all the peaks in one rotation period should match. However, in practice, due to noise jumps and various other factors, the peak values of some peaks in one rotation period may be inconsistent even when no disconnection occurs. For this reason, if it is determined that an abnormality has occurred even if there is even a mismatch, the possibility of being determined to be abnormal even though it is actually normal increases considerably. Therefore, for example, the disconnection determination unit 110 determines that it is abnormal only when a state in which peak values do not coincide with each other during one rotation period occurs continuously for a predetermined number of rotation cycles. Thereby, the accuracy of disconnection detection can be improved. Although there is a slight delay between the occurrence of an abnormality and the detection of an abnormality, the delay is small, and the turbo molecular pump does not cause a substantial problem during the delay. Acceptable.

  When an open phase occurs due to disconnection or the like, and the waveform shape of the DC current detection signal changes as shown in FIG. 5B, the current value data newly taken into each delay register unit 101 at a predetermined timing greatly changes. To do. Therefore, it is determined that the peak value does not match in many of the six peak value determination units 100A to 100F, and the disconnection determination unit 110 determines that it is abnormal.

  As a result of executing the first disconnection detection process as described above, when it is determined that there is an abnormality (there is a disconnection) (Yes in step S6), the control unit 5 drives the drive current from the three-phase inverter circuit 4 to the three-phase motor M. Is temporarily stopped (step S7). However, even if the supply of the three-phase drive current is stopped, the three-phase motor M itself does not stop immediately but continues to rotate due to inertia. In this state, the control unit 5 executes the second disconnection detection process similar to step S2 according to the second disconnection detection program 54 (step S8). That is, when it is determined by the first disconnection detection process that there is a disconnection, the second disconnection detection process is executed to confirm this. As described above, since the execution time of the second disconnection detection process is about 1 second, the decrease in the rotational speed is slight during this time.

  Even when the result of executing the second disconnection detection process subsequent to the first disconnection detection process is determined to be abnormal (disconnected) (Yes in step S9), the drive current from the three-phase inverter circuit 4 to the three-phase motor M An abnormality notification is executed while stopping the supply of (step S12). Eventually, the three-phase motor M stops.

  On the other hand, if it is determined that there is no abnormality in the second disconnection detection process following the first disconnection detection process, there is an error due to some factor in the first first disconnection detection process even though there is actually no abnormality. And the supply of drive current from the three-phase inverter circuit 4 to the three-phase motor M is resumed (step S10), and the process returns to step S4. Therefore, when the three-phase motor M is in a normal operation state, specifically, the first disconnection execution process is repeatedly executed during the acceleration operation and the steady operation from the start to the steady operation. become.

  Note that the determination conditions in the disconnection determination unit 110 shown in FIG. 4 can be changed as appropriate. For example, if the detection target is unacceptable as described above, that is, if it is a driving target that immediately causes a major problem when a disconnection occurs, the number of rotation cycles for determining a continuous peak value mismatch state It is good to judge that it is abnormal only by detecting a peak value mismatch state in one rotation period. Further, the number of stages of the delay register unit 101, that is, the time difference for obtaining two peak values to be compared can be determined as appropriate. Actually, these can be dealt with only by changing the program, so the change is easy and does not require a large cost.

  In the above description, the match / mismatch of the maximum values of the peaks appearing in the DC current detection signal in the normal state is determined. However, the maximum value is not necessarily required, and the value of any position of each peak waveform is used. Obviously you can also. Further, as described above, six peaks appear during one rotation period, but it is not always necessary to determine the coincidence / non-coincidence of the peak values (or other values) of all the peaks. In the above description, the decrease in the number of peaks during one rotation period is determined. However, a period corresponding to a rotation other than one rotation such as a ½ rotation period and a ３ rotation period instead of a rotation period. Obviously, the number of peaks in the middle may be used.

  Next, a modified example of the first and second disconnection detection processing will be described.

FIG. 10 is an explanatory diagram of a control method which is a modified example of the second disconnection detection process, and FIG. 11 is a diagram showing a current flow at this time.
If the drive pattern is set as shown in FIG. 10 (a), current should flow through the route as shown in FIG. 11 (a). Therefore, if there is a break in the R-phase or S-phase distribution line, The current i does not flow through the shunt resistor 36. If the drive pattern is set as shown in FIG. 10 (b), current should flow through the route as shown in FIG. 11 (b). Therefore, when there is a break in the R-phase or T-phase distribution line, The current i does not flow through the shunt resistor 36. Therefore, even if any of the distribution lines of the R phase, the S phase, and the T phase is disconnected, the detection is possible. Of course, in this case, several drive patterns other than those described in FIG. 6 are possible.

FIG. 12 is a block diagram of a modification of the first disconnection detection process, and FIG. 13 is a waveform diagram for explaining the operation of the disconnection detection unit of FIG.
In this example, the function of the disconnection detection unit is achieved by an analog circuit and processing on a microcomputer. That is, the DC current detection signal (voltage signal) obtained in the shunt resistor 36 is smoothed by the RC filter 200 having a predetermined time constant composed of the resistor R1 and the capacitor C1, and is input to one input terminal of the comparator 201. Then, the direct current detection signal is inputted as it is to the other input end. By making the time constant of the RC filter 200 very large, the output Vref settles near the average value of the DC current detection signal having a sawtooth waveform. Since the comparator 201 determines the magnitude of the DC current detection signal based on the output Vref, the sawtooth DC current detection signal is converted into a binary pulse signal, and each pulse corresponds to the peak of the DC current detection signal. It will be a thing.

  Therefore, six binary pulses are generated during one rotation period of the three-phase motor M when there is no phase loss, and only two binary pulses are generated during one rotation period when an abnormality occurs when the phase failure occurs. The counting unit 203 obtained as a functional block in the microcomputer 202 counts the number of binary pulses in one rotation cycle, and sends the count result to the disconnection determination unit 204. Similarly to the disconnection determination unit 110 of the above-described embodiment, the disconnection determination unit 204 determines that it is abnormal if it detects that the count value is continuously 2 (or not 6), for example, for a predetermined number of rotation cycles. As a result, as in the above embodiment, it is possible to detect an open phase due to a disconnection or the like while the three-phase motor M is being driven. Of course, the counting unit 203 and the disconnection determination unit 204 in FIG. 12 may be configured by a hardware circuit.

  Each of the above embodiments is an example of the present invention, and it is obvious that changes, modifications, or additions can be made as appropriate within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply 2 ... Rectification circuit 3 ... DC / DC conversion circuit 31 ... Switching element 32 ... Transformer 33, 34 ... Diode 35 ... Capacitor 36 ... Shunt resistor 37 ... Output voltage detection part 4 ... Three-phase inverter circuits 41, 43 45 ... high voltage side switching elements 42, 44, 46 ... low voltage side switching elements 47 ... inverter drive unit 5 ... control unit 51 ... CPU
52 ... Drive control program 53 ... First disconnection detection program 54 ... Second disconnection detection program 55 ... Abnormality response program 6 ... Display units 100A to 100F ... Peak value determination unit 101 ... Delay register unit 102 ... Comparator unit 110 ... Disconnection determination unit 111 ... Abnormality processing unit 200 ... RC filter 201 ... Comparator 202 ... Microcomputer 203 ... Counting unit 204 ... Disconnection determination unit M ... Three-phase motor

Claims (3)

AC / DC converting means for converting commercial AC power to DC power, inverter means having switching elements connected in a three-phase bridge to convert the DC power to three-phase AC power, and for each phase of the inverter means Control means for operating a three-phase motor by supplying a three-phase drive current to a three-phase motor connected to the inverter means by controlling on / off of switching elements on a high-voltage side and a low-voltage side. In the three-phase motor drive control device
a) a current detector for detecting a direct current flowing through the inverter means by a DC voltage applied to the inverter means; and a direct current by the current detector while supplying a three-phase drive current to the three-phase motor. The presence or absence of a phase failure is detected by detecting a change in the number of current waveform peaks that repeatedly appear during a period corresponding to a predetermined rotation of the three-phase motor based on the detection result. A first disconnection detection means including a driving phase loss determination unit for determining
b) With no three-phase drive current supplied to the three-phase motor, turn on any one-phase high-voltage switching element included in the inverter means and turn on the other two-phase low-voltage switching elements. In addition, the driving of the switching elements according to the driving pattern of turning off the other switching elements is sequentially executed for each phase, or the high voltage side switching elements and the low voltage side of the different phases included in the inverter means Disconnection detection control unit that sequentially executes driving of the switching elements according to the drive pattern of turning on the other switching elements and turning off the other switching elements for two or more drive patterns, and the disconnection detection control unit Each time the switching element is turned on / off with a different drive pattern, Ri determines whether current is flowing, and non-driving time of phase failure determination section for determining that there is a phase loss when there are drive pattern no current flows, and a second disconnection detecting means including,
And when the three-phase motor is supplied with a three-phase drive current and the first disconnection detecting means determines that there is a phase failure, the rotational drive of the three-phase motor is temporarily stopped. The three-phase motor drive control is characterized by detecting the disconnection of the internal wiring of the three-phase motor or the distribution line to the three-phase motor by executing the determination of the presence or absence of the phase loss by the second disconnection detecting means. apparatus. The three-phase motor drive control device according to claim 1,
When the three-phase motor is started, the second disconnection detecting means determines whether or not there is a phase loss prior to the start, and if it is determined that there is no phase loss, the three-phase motor is started. A three-phase motor drive control device. The three-phase motor drive control device according to claim 1 or 2,
The driving phase loss determination unit acquires a signal reflecting the current value of the direct current at a predetermined timing when the peak of the current waveform appears when there is no phase loss in the period corresponding to the predetermined rotation of the three-phase motor. A three-phase motor drive control device that compares this with a signal for the same timing obtained at a time point that is traced back by a predetermined time, and determines the presence or absence of a phase loss based on the comparison result.

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