JP2013123334A - Three-phase motor drive controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect phase interruption such as disconnection of a three-phase motor during rotational drive of the three-phase motor with a simple and inexpensive structure.SOLUTION: When a driving current is supplied to a three-phase motor M from a three-phase inverter circuit 4 in order to rotate the three-phase motor M, a control part 5 detects a DC current flowing through a shunt resistor 36. When there is no phase interruption such as disconnection, six sawtooth peaks appear in a DC current detection signal during one revolution of the motor M. On the contrary, if phase interruption is caused in one phase, the number of peaks during one revolution is reduced to two. Therefore, in the control part 5, current value data timely read when the six peaks during the normal time appear are used to compare the value at the time traced back by a prescribed time with the latest value, and whether or not the number of peaks decreases is thereby determined. If abnormality is recognized as a result, driving of the three-phase motor M is stopped and the abnormality is notified by a display 6.

Description

  The present invention relates to a drive control device for driving a three-phase motor, and more specifically, a three-phase motor having a disconnection detecting 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 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 motor 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 in order to solve the above-mentioned problems. The object of the present invention is to provide an internal wiring of the three-phase motor substantially continuously during driving of the three-phase motor at a low cost. It is providing the three-phase motor drive control apparatus which can detect the disconnection of the distribution line which connects the said apparatus and a 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 a switching element connected in a three-phase bridge to convert DC power into three-phase AC power. Inverter means, and control means for energizing a three-phase motor connected to the inverter means by controlling on / off of switching elements on the high voltage side and low voltage side of each phase of the inverter means, In a three-phase motor drive control device comprising an internal wiring of a three-phase motor and a disconnection detecting means for detecting disconnection of a distribution line to the three-phase motor,
The disconnection detecting means is
a) current detection means for detecting a direct current flowing in the inverter means by a DC voltage applied to the inverter means;
b) DC current is detected by the current detection means while the three-phase motor is rotationally driven, and a current waveform repeatedly appearing during a period corresponding to a predetermined rotation of the three-phase motor based on the detection result. A phase failure determination means for determining the presence or absence of phase loss by directly or indirectly detecting a change in the number of peaks;
It is characterized by having.

  When three-phase AC power is supplied to the three-phase motor by the inverter means and the motor is rotationally 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 three-phase motor drive control device according to the present invention, the phase loss determination means detects the reduction in the number of peaks repeatedly appearing in the current waveform as described above or a phenomenon caused by the reduction. Recognize that occurred. Therefore, the determination of the phase loss is performed in parallel with the normal rotational drive of the three-phase motor. 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.

  As one aspect of the three-phase motor drive control device according to the present invention, the phase loss determination means is configured such that the phase of the current waveform is peaked when there is no phase loss (that is, during normal operation) during a period corresponding to a predetermined rotation of the three-phase motor. A signal that reflects the current value of the DC current is acquired at a predetermined timing when appears, and this is compared with the signal for the same timing obtained at a time point that is traced back by a predetermined time. It can be set as the structure which judges the presence or absence. 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.

  In the above configuration, since the signal detected by the current detection means 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 the condition for determining the phase loss.

  Further, as another aspect of the three-phase motor drive control device according to the present invention, the phase loss determination means includes a pulsing means for comparing a signal obtained by the current detection means with a predetermined threshold value and converting the pulse signal into a pulse signal. And counting means for counting the pulse signal during a period corresponding to one rotation of the phase motor, and the presence or absence of a missing phase can be determined based on the counting result by the counting means. Here, the predetermined threshold value can be a signal level obtained by integrating a signal obtained by the current detection means for a predetermined time.

  In the above configuration, for example, the pulsing means can be constituted by an analog circuit including a comparator and the processing by the counting means can be performed by a general-purpose microcomputer. Thereby, although it is necessary to add an analog circuit, the microcomputer program can be simpler than the above-described embodiment.

  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 rotational driving of the three-phase motor, and to stop the driving or perform a warning notification. Therefore, if the three-phase motor drive control device according to the present invention is used for driving the vacuum pumping turbo molecular pump of the semiconductor manufacturing apparatus, the production line is stopped by detecting the danger that the degree of vacuum will drop due to disconnection. Appropriate responses can be taken without delay.

  In the three-phase motor drive control device according to the present invention, it is possible to detect an open phase caused by a disconnection or the like regardless of the type and specification of the three-phase motor to be driven. Therefore, even if the three-phase motor to be driven is changed, it is not necessary to change the conditions for determining the phase loss, and the versatility of the device can be improved. In addition, a current transformer that detects an alternating current flowing through the three-phase motor is unnecessary, and an increase in cost can be suppressed to a minimum.

The block block diagram of the principal part of the three-phase motor drive control apparatus which is one Example of this invention. The functional block diagram implement | achieved at the time of the disconnection detection program at the time of rotation in FIG. 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 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. As is well known, the CPU 51 executes a predetermined process in accordance with a control program stored in a storage device such as a ROM. Here, the CPU 51 is roughly divided into a normal drive control program 52, a disconnection detection program 53, and an abnormal time response. Program 54. The normal 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 disconnection detection program 53 is a program for executing the disconnection detection processing characteristic of the present embodiment, and the abnormality response program 54 is a program that controls the operation of the apparatus when a disconnection is detected. 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.

  In the three-phase motor drive control device of the present embodiment, when the three-phase motor M is in a normal operation state, specifically, during steady operation or during acceleration operation from startup to steady operation, Detection of the internal wiring of the phase motor M and the disconnection of the distribution line is repeatedly executed. This disconnection detection operation will be described with reference to FIGS. 2 to 3 in addition to FIG. FIG. 2 is a functional block diagram realized when the rotation disconnection detection program in FIG. 1 is executed, and FIG. 3 is a diagram showing an example of a DC current detection signal at normal time and abnormal (one phase missing phase).

As shown in FIG. 3 (a), when a drive current is supplied from the three-phase inverter circuit 4 to the three-phase motor M for normal operation, the three-phase During the period of one rotation of the motor M, six peaks (peaks P _{1 to} P ₆ ) appear in the DC current detection signal in a substantially triangular shape (sawtooth shape). 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, Te than at a predetermined timing synchronized with the control signal from the controller 5 to read the DC current detection signal, the peak P ₁ to P ₆ For example, 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 in each rotation cycle 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. There are two substantially triangular peaks (peaks P _A and P _B ) appearing in the DC current detection signal during the period. 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. In the three-phase motor drive control device of the present embodiment, the three-phase motor M is obtained by capturing the decrease in the number of substantially triangular peaks appearing in the DC current detection signal during one rotation period of the three-phase motor M. Disconnection is detected during driving.

Although it is possible to directly determine whether or not the number of peaks has decreased as in the example described later, in this embodiment, 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 indirectly determined.
Specifically, as shown in FIG. 2, the functional block realized by executing the rotation 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). Thus, the current value data that has been newly acquired and has already been acquired is shifted. Therefore, new current value data is taken in every rotation period of the three-phase motor M, and the oldest peak value, that is, the peak value taken in the past by a predetermined number of stages, is discharged. 2, for example, the delay register unit 101 of the peak value determining section 100A captures the new peak value each following timing capable capture the peak value of the peak P ₁ in FIG. 3 (a), the peak value determination section 100F delay register unit 101 captures the new peak value each following timing capable 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, the peak values of all the peaks during one rotation period of the three-phase motor M should match in the normal state. 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 due to a disconnection or the like occurs and the waveform shape of the DC current detection signal changes as shown in FIG. 3B, current value data newly taken into each delay register unit 101 at a predetermined timing is obtained. It changes a lot. Therefore, many of the six peak value determination units 100 </ b> A to 100 </ b> F are determined to be inconsistent with the peak value, and the disconnection determination unit 110 sends a determination result that indicates an abnormality to the abnormality processing unit 111. In response to this, the abnormality processing unit 111 displays an abnormality occurrence on the display device 6 and sends a drive stop control signal to the inverter driving unit 47. As a result, the drive current to the three-phase motor M is cut off. Of course, the user may be alerted by a buzzer sounding at the same time as the display.

  The determination conditions in the disconnection determination unit 110 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, it is not always necessary to use the maximum value, and the value at 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.

  In the above-described embodiment, the presence / absence of a decrease in the number of peaks is determined based on the result of coincidence / non-coincidence of the peak values of the DC current detection signal. Absent. Furthermore, it is not realized by the operation of the program on the microcomputer, but can be realized by a hardware circuit (analog or digital), or by a combination of the hardware circuit and the processing on the microcomputer. You can also

  An example of the latter will be described with reference to FIGS. FIG. 4 is a block diagram of a disconnection detection unit in a three-phase motor drive control apparatus according to another embodiment of the present invention, and FIG. 5 is a waveform diagram for explaining the operation of the disconnection detection unit of FIG.

  In this embodiment, 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. As shown in FIG. 5, by setting 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 shape. 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 period, 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, for example, it is detected that the count value is continuously 2 (or not 6) for a predetermined number of rotations. 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. 4 may be configured by a hardware circuit.

  The above-described embodiment 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 alternating current power supply 2 ... Rectifier circuit 3 ... DC / DC converting circuit 31 ... Switching element 32 ... Transformer 33 ... 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 section 5 ... control section 51 ... CPU
52 ... Normal drive control program 53 ... Disconnection detection program 54 ... Abnormality response program 6 ... Indicators 100A to 100F ... Peak value determination unit 101 ... Delay register unit 102 ... Comparator unit 110 ... Disconnection determination unit 111 ... Abnormal 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 a switching element connected in a three-phase bridge to convert DC power to three-phase AC power, and a high frequency for each phase of the inverter means Control means for energizing the three-phase motor connected to the inverter means by controlling on / off of the voltage-side and low-voltage side switching elements, and the internal wiring of the three-phase motor and the distribution line to the three-phase motor In a three-phase motor drive control device comprising a disconnection detecting means for detecting disconnection of
The disconnection detecting means is
a) current detection means for detecting a direct current flowing in the inverter means by a DC voltage applied to the inverter means;
b) DC current is detected by the current detection means while the three-phase motor is rotationally driven, and a current waveform repeatedly appearing during a period corresponding to a predetermined rotation of the three-phase motor based on the detection result. A phase failure determination means for determining the presence or absence of phase loss by directly or indirectly detecting a change in the number of peaks;
A three-phase motor drive control device comprising: The three-phase motor drive control device according to claim 1,
The phase loss determination means 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. Is compared with a signal for the same timing obtained at a time point that is traced back by a predetermined time, and the presence or absence of a phase loss is determined based on the comparison result. The three-phase motor drive control device according to claim 1,
The phase loss determination unit compares the signal obtained by the current detection unit with a predetermined threshold value and converts it into a pulse signal, and counts the pulse signal during a period corresponding to one rotation of the three-phase motor. A three-phase motor drive control device comprising: a counting unit configured to determine whether or not there is a phase loss based on a counting result obtained by the counting unit.

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