Magnetic saturation detection circuit, noise filter, motor driver, and magnetic saturation detection method

Abstract

To provide a technology that enables detection of magnetic saturation of a choke coil and monitoring of a high-frequency noise suppressing effect.SOLUTION: A magnetic saturation detection circuit includes: a detection part that detects a physical quantity related to magnetic saturation of a common-mode choke coil provided in series on a path from a power source; a determination part that determines that the magnetic saturation occurs in the common-mode choke coil, on a condition that intensity of a magnetic field of the common-mode choke coil, estimated from the detected physical quantity satisfies a prescribed reference; and a notification part that provides external notification of the result of the determination.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a magnetic saturation detection circuit for detecting magnetic saturation in a choke coil, a noise filter, a motor driver, and a magnetic saturation detection method. [Background technology]

[0002] Conventionally, in the fields of FA (Factory Automation) and robotics, a noise filter having a common mode choke coil is provided on a power supply path to suppress high-frequency noise generated during switching operations of power conversion. When a common mode current exceeding the regulation flows into the power supply path as high-frequency noise accompanying switching operations, the common mode choke coil provided in the noise filter may cause magnetic saturation, and may not be effective enough in suppressing high-frequency noise. In the above fields, if a sufficient suppression effect against high-frequency noise is not obtained, there is a risk that the noise that circulates through the power supply path may cause the circuit to malfunction or stop functioning in the equipment or peripheral devices that involve power conversion. For this reason, in a work site where equipment or devices that involve power conversion are installed, a worker performs monitoring work such as visually checking the sound emitted by the noise filter during operation of the equipment or the current waveform flowing through the noise filter with an oscilloscope or the like. In this way, it is time-consuming to confirm that magnetic saturation is not occurring, and the monitoring work is a burden on the worker. The following patent documents are prior art documents that describe technologies related to the technology described in this specification. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-100579 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, Patent Document 1 discloses detecting a ground fault current flowing through a choke coil in order to reduce the cost of devices (current transformers, zero-phase current transformers, etc.) that detect ground fault currents in power supply paths. Patent Document 1 describes whether the magnetic flux generated in the core by the AC current and the magnetic flux generated in the core by the return current cancel each other out in the core, but does not consider the suppression effect against magnetic saturation or high-frequency noise. Conventionally, the magnetic saturation of noise filters for motor drivers was confirmed by the manufacturer using a noise terminal voltage test to confirm the amount of noise, or by the user checking the coil sound and current waveform to confirm that the filter is not magnetically saturated. In consideration of the above problems, the object of the present invention is to provide a technology that can monitor the suppression effect of high-frequency noise as well as detect the magnetic saturation of a choke coil. [Means for solving the problem]

[0005] One aspect of the disclosed technique for solving the above problem is to a detection unit that detects a physical quantity related to magnetic saturation of a common mode choke coil that is provided in series with a path from a power supply; a determination unit that determines whether magnetic saturation has occurred in the common mode choke coil, on condition that the strength of the magnetic field of the common mode choke coil estimated from the detected physical quantity satisfies a predetermined standard; and a notification unit that notifies an external device of a result of the determination; A magnetic saturation detection circuit comprising:

[0006] This allows the magnetic saturation detection circuit (10, 10a, 10b) to estimate the magnetic field strength of the common mode choke coil 21 from physical quantities (current value, core magnetic flux) related to the magnetic saturation of the common mode choke coil 21 detected by the current transformer CT, which is the detection unit, and the magnetic flux measurement coil 23. The magnetic saturation detection circuit (10, 10a, 10b) determines that a magnetic saturation state exists when the estimated magnetic field strength exceeds a set threshold value or is equal to or greater than the threshold value, and can notify the outside of the result of this determination. Since it is possible to monitor the effect of suppressing high-frequency noise as well as detect the magnetic saturation of the choke coil, the workload associated with monitoring the magnetic saturation can be reduced.

[0007] In one embodiment of the disclosed technology, the notification unit may notify information related to suppression of high-frequency noise in a circuit including the power supply. This allows the magnetic saturation detection circuit (10, 10a, 10b) to notify information (cable length, cable type (with or without shielding), appropriate filter inductor settings, etc.) that prompts a review of stray capacitance on the power supply path, and the margin until magnetic saturation, via the notification unit 105, thereby improving usability regarding magnetic saturation countermeasures.

[0008] In one embodiment of the disclosed technology, the detection unit detects a current flowing through the common mode choke coil, and the determination unit estimates a magnetic field strength of the common mode choke coil from the detected current value, and determines that magnetic saturation has occurred in the common mode choke coil on the condition that the estimated magnetic field strength exceeds a first threshold. This allows the magnetic saturation detection circuit (10, 10a, 10b) which is a detection circuit to obtain a magnetic field strength H, which is the strength of a magnetic field generated in the common mode choke coil 21 from the current value using equation (1), and to determine whether the obtained magnetic field strength exceeds the first threshold by comparing it with a magnetic field at which magnetic saturation occurs. The magnetic saturation detection circuit (10, 10a, 10b) can determine whether magnetic saturation has occurred based on the magnetic field strength formed by the current flowing through the common mode choke coil 21.

[0009] In one embodiment of the disclosed technique, the detection unit detects a magnetic flux of a common mode choke coil, The determination unit may estimate the magnetic flux density of the common mode choke coil from the detected magnetic flux, and determine that magnetic saturation has occurred in the common mode choke coil on the condition that the estimated magnetic flux density exceeds a second threshold. This allows the magnetic saturation detection circuit (10, 10a, 10b) which is a detection circuit to obtain the magnetic flux density B, which is the strength of the magnetic field generated in the common mode choke coil 21 from the core magnetic flux, using equation (2), and to determine whether the obtained magnetic flux density exceeds the second threshold by comparing it with the magnetic flux saturation density, which is the second threshold. The magnetic saturation detection circuit (10, 10a, 10b) can determine whether magnetic saturation has occurred based on the magnetic flux density of the core 21a of the common mode choke coil 21.

[0010] In another embodiment of the disclosed technology, the noise filter may be provided with a common mode choke coil, and the notification unit may be provided with the magnetic saturation detection circuit according to claims 1 to 4 that notifies information related to the degree of noise removal by the noise filter. Even in this embodiment, the noise filter 20 can determine that magnetic saturation has occurred and notify the result of the determination to the outside when the strength of the magnetic field estimated by the magnetic saturation detection circuit (10, 10a, 10b) satisfies a predetermined condition. In addition, since the current magnetic field strength H, magnetic flux density B, and margin until magnetic saturation can be notified via the notification unit 105 as information related to the degree of noise removal by the noise filter, usability regarding magnetic saturation countermeasures can be improved. Even during operation of equipment, devices, etc. involving power conversion, the magnetic saturation of the choke coil can be detected and the suppression effect of high-frequency noise can be monitored without stopping the operation of the equipment. becomes visible.

[0011] In another embodiment of the disclosed technology, the motor driver may be provided with the magnetic saturation detection circuit according to any one of claims 1 to 4, or the noise filter according to claim 5, and may be configured to issue a notification to prompt a predetermined process based on the result of the determination notified by the magnetic saturation detection circuit or the noise filter. The motor driver 3 can take measures according to the presence or absence of magnetic saturation in the common mode choke coil 21 determined by the magnetic saturation detection circuit (10, 10a, 10b) without stopping the operation during operation. Since it is possible to monitor the effect of suppressing high frequency noise as well as detect the magnetic saturation of the choke coil, the workload of monitoring the magnetic saturation can be reduced.

[0012] In another embodiment of the disclosed technology, the predetermined process may be to prompt the user to replace a power line connecting the motor driver and a motor to which driving power generated by the motor driver is supplied, or to review a stray capacitance to ground that exists between the power line and the motor. When magnetic saturation occurs, it becomes possible to prompt the user to take specific measures to eliminate the magnetic saturation occurring in the noise filter 20 through a display panel of the motor driver 3 or the like.

[0013] In another embodiment of the disclosed technology, the magnetic saturation detection circuit may calculate a margin amount until magnetic saturation occurs when magnetic saturation does not occur in the common mode choke coil and notify the calculated margin amount. When magnetic saturation does not occur, the margin amount until magnetic saturation occurs can be displayed on the display panel of the motor driver 3, so that the number of motors 50 that can be driven by the motor driver 3, the number of cables that can be connected, etc. can be grasped, and usability regarding magnetic saturation countermeasures can be improved.

[0014] In another aspect of the disclosed technique, a physical quantity related to magnetic saturation of a common mode choke coil provided in series with a path from a power source is detected, determining that magnetic saturation has occurred in the common mode choke coil on the condition that the strength of the magnetic field of the common mode choke coil estimated from the detected physical quantity satisfies a predetermined standard; notifying an external party of the result of the determination; and 13. A method for detecting magnetic saturation comprising:

[0015] Even in this configuration, the magnetic saturation detection circuit (10, 10a, 10b) can estimate the magnetic field strength of the common mode choke coil 21 from physical quantities (current value, core magnetic flux) related to the magnetic saturation of the common mode choke coil 21 detected by the current transformer CT, which is a detection unit, and the magnetic flux measurement coil 23. The magnetic saturation detection circuit (10, 10a, 10b) can determine that a magnetic saturation state exists when the estimated magnetic field strength exceeds a set threshold value or is equal to or greater than the threshold value, and can notify the result of the determination to the outside. Even during operation of equipment, devices, etc. involving power conversion, it is possible to detect the magnetic saturation of the choke coil and monitor the suppression effect of high-frequency noise without stopping the operation of the equipment, thereby reducing the workload associated with monitoring the magnetic saturation. Effect of the Invention

[0016] According to the present invention, it is possible to monitor the effect of suppressing high frequency noise as well as detect the magnetic saturation of the choke coil, thereby reducing the workload associated with monitoring the magnetic saturation. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a schematic configuration of a noise filter according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing a schematic configuration of a magnetic saturation detection circuit according to a first embodiment of the present invention. [Diagram 3] 10A and 10B are diagrams illustrating measurement of core magnetic flux of a common mode choke coil according to a modified example of the present invention. [Figure 4] FIG. 13 is a block diagram showing a schematic configuration of a magnetic saturation detection circuit according to a modified example of the present invention. [Diagram 5] FIG. 11 is a block diagram showing a schematic configuration of a motor drive system according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a diagram illustrating an example of a hardware configuration of a control unit according to a second embodiment of the present invention. [Figure 7] 10 is a flowchart showing an example of a magnetic saturation detection process according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [Application example] Hereinafter, application examples of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a schematic configuration of a noise filter 20 according to an application example of the present invention. The noise filter 20 according to the application example includes a pair of input terminals (TP1, TP2), a pair of output terminals (TP3, TP4), and a common mode choke coil 21, suppresses high-frequency noise of the power supply power input between the pair of input terminals, and outputs the noise to the pair of output terminals. When a common mode current I specified in the specifications of the noise filter 20 flows on the power supply path, the common mode choke coil 21 may cause magnetic saturation, and may not be effective enough in suppressing high-frequency noise. For this reason, in equipment that generates desired power through switching operations, the current flowing through the noise filter 20 during power conversion is detected via a test circuit 9, and the waveform of the current is visually confirmed with an oscilloscope, etc., to confirm that magnetic saturation does not occur.

[0019] In the embodiment according to this application example, as shown in FIG. 2, a magnetic saturation detection circuit is provided that detects the occurrence of magnetic saturation in the common mode choke coil 21 of the noise filter 20 based on the current value flowing through the choke coil. For example, the magnetic saturation detection circuit detects the current value flowing through the common mode choke coil 21 of the noise filter 20 via a current detection unit. The magnetic saturation detection circuit obtains the magnetic field strength, which is the strength of the magnetic field generated in the common mode choke coil 21, from the detected current value, and judges whether the magnetic field strength exceeds the magnetic field at which magnetic saturation occurs. The magnetic saturation detection circuit according to this application example notifies the outside of the judgment result indicating the occurrence of magnetic saturation, which is judged based on the magnetic field strength formed by the current flowing through the common mode choke coil 21. According to this application example, the magnetic saturation generated in the common mode choke coil 21 can be grasped through the magnetic saturation detection circuit, so that there is no need to connect a test circuit 9 to the noise filter 20 to monitor the current waveform as in the conventional case.

[0020] In another embodiment of this application example, as shown in Figs. 3 and 4, the core magnetic flux of the common mode choke coil 21 is measured, a magnetic flux density indicating the strength of the magnetic field is obtained, and it is possible to determine whether or not the magnetic flux density exceeds the magnetic flux density that causes magnetic saturation. The magnetic saturation detection circuit 10a of another embodiment can determine the magnetic saturation that occurs in the common mode choke coil 21 based on the magnetic flux density B obtained from the core magnetic flux. The magnetic saturation detection circuit 10a can notify the determination result to the outside. For example, in the case of the noise filter 20 that integrally houses the magnetic saturation detection circuit 10a, if an LED or the like indicating that magnetic saturation occurs is provided on the housing, the notification unit 105 can turn on the LED based on the determination result. In the case where the noise filter 20 has a terminal that outputs a signal indicating the detection result, a higher-level device (such as a power converter or a power conversion system) that has the filter on its power supply path may perform processing such as turning on an LED or the like or displaying a notice on a display panel based on the signal indicating the detection result output from the output terminal. In this embodiment, the magnetic saturation detection circuit 10a is also used. Through this, it becomes possible to detect magnetic saturation of the choke coil and monitor the effect of suppressing high-frequency noise during operation of equipment involving power conversion.

[0021] As another embodiment of this application example, as shown in Figs. 5 to 7, a system including a magnetic saturation detection circuit that measures a physical quantity related to the magnetic saturation of the common mode choke coil 21 through the detection unit 29 of the noise filter 20 and detects the magnetic saturation from the physical quantity may be used. In this system, based on the notification from the magnetic saturation detection circuit, it is possible to light an LED or the like that indicates the magnetic saturation state provided on the housing or the like, display a message that magnetic saturation has occurred on a display panel or the like, or to notify through an electronic sound, speaker, or the like. According to the notified content, it is possible to promote the review of the stray capacitance to ground that induces magnetic saturation, such as changing the length of the power line W2, wiring layout, and cable type (with or without shielding), and the selection of a noise filter having an appropriate inductor according to the operating environment, etc. In addition, it is also possible to display the margin amount up to the magnetic saturation calculated by the magnetic saturation detection circuit. This improves the usability of monitoring the magnetic saturation.

[0022] Example 1 Hereinafter, specific embodiments of the present invention will be described in more detail with reference to the drawings.

[0023] <Circuit configuration> FIG. 1 is a block diagram showing a schematic configuration of a noise filter 20 according to an embodiment of the present invention. The noise filter 20 shown in FIG. 1 includes a pair of input terminals (TP1, TP2), a pair of output terminals (TP3, TP4), and a common mode choke coil 21. The noise filter 20 is provided, for example, in series on a power supply path, suppresses high-frequency noise of the power supply power input between the pair of input terminals (TP1, TP2), and outputs the noise to the pair of output terminals (TP3, TP4). The common mode choke coil 21 is inserted in series between the pair of input terminals (TP1, TP2) and the pair of output terminals (TP3, TP4), and includes a core 21a, a winding 21b, and a winding 21c. The winding 21b is connected in series between the input terminal TP1 and the output terminal TP3, and the winding 21c is connected in series between the input terminal TP2 and the output terminal TP4. Between the lines 22a-22b to which the common mode choke coil 21 and the output terminals (TP3, TP4) are connected, X capacitors (interphase capacitors) C1 and C2 and a Y capacitor C3 are provided. The X capacitors C1 and C2 are inserted in series between the lines 22a-22b, and one end of the Y capacitor C3 is connected to the connection point between the X capacitors C1 and C2, and the other end is connected to FG (Frame Ground), which is the ground reference potential on the housing side. The X capacitors C1 and C2 reduce normal mode noise between the lines 22a-22b, and the Y capacitor C3 reduces common mode noise.

[0024] Here, when a current I that generates a magnetic flux density exceeding the magnetic flux saturation density of the core of the noise filter 20 flows through the power supply path, the common mode choke coil 21 may become magnetically saturated, and there may be cases where the effect of suppressing high frequency noise is insufficient. For example, in equipment that generates desired power through the switching operation of a switching element or the like from AC power supplied from a main power supply, the current flowing through the noise filter 20 during power conversion is detected through a test circuit 9 or the like, and the waveform of the current is visually confirmed with an oscilloscope or the like to confirm that magnetic saturation is not occurring.

[0025] The test circuit 9 includes, for example, a rectifier circuit 9a, a voltage divider circuit 9b, and a regulator 9c. The rectifier circuit 9a receives AC power output from a pair of output terminals (TP3, TP4) of the noise filter 20. The rectifier circuit 9a rectifies the AC power through a bridge circuit formed of, for example, rectifier elements (diode elements), and the rectified DC power is output to the voltage divider circuit 9b. The voltage divider circuit 9b receives the DC power rectified through the rectifier circuit 9a and outputs it to the voltage divider circuit 9b. The voltage value of is divided to a predetermined voltage value and input to regulator 9c. The divided voltage value is stabilized by regulator 9c and supplied to a detection circuit such as an oscilloscope. In a facility where equipment involving power conversion is installed, an operator connects test circuit 9 to a pair of output terminals (TP3, TP4) of noise filter 20 and observes the current waveform output from test circuit 9 using an oscilloscope to check for magnetic saturation. In this way, in the conventional work, the workload of checking for magnetic saturation was high.

[0026] In the embodiment according to the present invention, a magnetic saturation detection circuit is provided that detects the occurrence of magnetic saturation in the common mode choke coil 21 of the noise filter 20 based on the current value flowing through the common mode choke coil 21. The magnetic saturation detection circuit detects the current value flowing through the common mode choke coil 21 of the noise filter 20 via a current detection unit. The magnetic saturation detection circuit obtains the magnetic field strength, which is the strength of the magnetic field generated in the common mode choke coil 21, from the detected current value and judges whether the magnetic field strength exceeds the magnetic field at which magnetic saturation occurs. The magnetic saturation detection circuit according to the present invention notifies the outside of the judgment result indicating the occurrence of magnetic saturation, which is judged based on the magnetic field strength formed by the current flowing through the common mode choke coil 21. According to the present embodiment, since the magnetic saturation generated in the common mode choke coil 21 can be grasped through the magnetic saturation detection circuit, there is no need to connect the test melting furnace 9 to the noise filter 20 and monitor the current waveform as in the conventional method. In addition, the magnetic saturation can be grasped during the operation of equipment, devices, etc. involving power conversion through the magnetic saturation detection circuit.

[0027] In this embodiment, a current transformer CT is exemplified as an example of a current detection unit that detects a current flowing through the common mode choke coil 21. As shown in Fig. 1, the current transformer CT may detect a current flowing between a pair of input terminals (TP1, TP2) and the common mode choke coil 21 on the input side, or may detect a current flowing between the common mode choke coil 21 and a pair of output terminals (TP3, TP4) on the output side. When measuring the current flowing on the output side, it is desirable to measure the current flowing on the common mode choke coil side from a Y capacitor C3 provided between the lines 22a and 22b in order to accurately measure the common mode current flowing through the common mode choke coil 21.

[0028] FIG. 2 is a block diagram showing a schematic configuration of the magnetic saturation detection circuit 10 according to the present embodiment. FIG. 2 illustrates an example of a detection circuit that obtains the magnetic field strength generated in the common mode choke coil 21 from the current value detected by the current transformer CT and determines whether the magnetic field strength exceeds the magnetic field that generates magnetic saturation. The magnetic saturation detection circuit 10 in FIG. 2 includes a low-pass filter 101, a determination unit 11, and a notification unit 105. The low-pass filter 101 suppresses high-frequency components of the current detected by the current transformer CT other than the switching frequency that generates magnetic saturation. The notification unit 105 is an interface that outputs a signal indicating the magnetic saturation detected by the magnetic saturation detection circuit 10 to the outside. The current value detected by the current transformer CT (CT detection value) is low-pass filtered through the low-pass filter 101 and input to the determination unit 11.

[0029] In the determination unit 11, the calculation unit 102 determines the magnetic field strength H indicating the strength of the magnetic field generated in the common mode choke coil 21 from the current value input through the low-pass filter 101. The magnetic field strength H (A / m) can be determined using the following formula (1).

number

[0030] The magnetic field strength H obtained by the calculation unit 102 is input to the comparator 104 and compared with the threshold value 103. Here, the threshold value 103 is set with information indicating the strength of the magnetic field at which the magnetic saturation of the common mode choke coil 21 occurs. For example, in the case where the magnetic flux saturation density Bs is specified, the threshold value 103 is set with ([Bs·k / μ], k: adjustment coefficient, μ: magnetic permeability). In this embodiment, the information indicating the magnetic field strength set in the threshold value 103 (Bs·k / μ) corresponds to an example of the "first threshold value". For example, the comparator 14 compares the magnetic field strength H input to the positive terminal with the threshold value 103 input to the negative terminal, and judges whether the magnetic field strength H exceeds the magnetic field at which the magnetic saturation occurs. The result of the judgment is input to the notification unit 105 and is notified to the outside of the magnetic saturation detection circuit 10 via the notification unit 105.

[0031] The notification unit 105 may notify the outside of information related to suppression of high frequency noise together with the notification of the result of the judgment. For example, information (cable length, cable type (with or without shield), appropriate filter inductor setting, etc.) that prompts review of stray capacitance on the power supply path can be notified. Furthermore, when it is determined that magnetic saturation does not occur, the notification unit 105 may notify the magnetic field strength H calculated by the calculator 102 together with the result of the judgment, or may obtain the difference (margin) between the magnetic field strength H calculated by the calculator 102 and the threshold value 103 and notify the outside. By notifying the magnetic field strength H calculated by the calculator 102, the current suppression effect of high frequency noise can be grasped. Furthermore, by notifying the difference (margin) between the magnetic field strength H calculated by the calculator 102 and the threshold value 103, the margin until magnetic saturation occurs can be recognized. Based on the margin amount, for example, it becomes possible to grasp the number of cables that can be connected to a higher-level device (such as a power converter or power conversion system) or the number of electric motors that can be connected, thereby improving usability regarding magnetic saturation countermeasures.

[0032] The noise filter 20 shown in FIG. 1 integrally houses the magnetic saturation detection circuit 10 according to the present embodiment, and in the case where the housing of the noise filter 20 is provided with an LED or the like indicating that magnetic saturation has occurred, the notification unit 105 may light up the LED based on the result of the judgment. The LED lighting display allows the user to know that magnetic saturation has occurred in the common mode choke coil 21. The noise filter 20 may also be provided with a terminal that outputs a signal indicating the detection result. Information related to the suppression of high frequency noise can be notified to the outside via the terminal. A host device (such as a power converter or a power conversion system) on the power supply path of the noise filter 20 integrally housing the magnetic saturation detection circuit 10 according to the present embodiment can perform processing such as lighting up an LED or displaying a notification on a display panel based on a signal indicating the detection result output from the output terminal. According to this embodiment, the magnetic saturation of the choke coil can be detected through the magnetic saturation detection circuit 10 during operation of equipment involving power conversion.

[0033] [Modifications] In the first embodiment, an example of a circuit that determines magnetic saturation based on the magnetic field strength H obtained from the current flowing through the common mode choke coil 21 has been described. The magnetic saturation occurring in the common mode choke coil 21 can also be detected using the core magnetic flux of the core 21a. In the modified example, a magnetic saturation detection circuit 10a that uses the core magnetic flux of the core 21a will be described.

[0034] 3 is a diagram for explaining measurement of the core magnetic flux of common mode choke coil 21 according to the modified example. In the modified example, the core magnetic flux (Φ) of common mode choke coil 21 is detected through magnetic flux measuring coil 23 having n turns. The core magnetic flux (Φ) detected by magnetic flux measuring coil 23 is input to magnetic saturation detection circuit 10a.

[0035] FIG. 4 is a block diagram showing a schematic configuration of a magnetic saturation detection circuit 10a according to a modified example. 4 shows an example of a detection circuit that obtains a magnetic flux density indicating the strength of a magnetic field from the magnetic flux (Φ) detected through the magnetic flux measuring coil 23 and judges whether the magnetic flux density exceeds the magnetic flux density that causes magnetic saturation. The judgement unit 11a of the magnetic saturation detection circuit 10a calculates a magnetic flux density B (Wb / m 2 ) is calculated.

[0036] In the calculation unit 106, the core magnetic flux (Φ) detected by the magnetic flux measuring coil 23 and the cross-sectional area S (m 2 ), the magnetic flux density B, which indicates the strength of the magnetic field generated in the common mode choke coil 21, is calculated. 2 ) can be calculated using the following formula (2).

number

[0037] The magnetic flux density B found by the calculation unit 106 is input to the comparator 104 and compared with the threshold value 103a. Here, the threshold value 103a is set to a magnetic flux saturation density (B·m) that indicates the strength of the magnetic field at which magnetic saturation of the common mode choke coil 21 occurs. In the modified example, the magnetic flux saturation density set to the threshold value 103a corresponds to an example of a "second threshold value". For example, the comparator 14 compares the magnetic flux density B input to the positive terminal with the threshold value 103 input to the negative terminal, and determines whether the magnetic flux density B exceeds the magnetic flux saturation density (B / m). The result of the determination is input to the notification unit 105 and notified to the outside of the magnetic saturation detection circuit 10a via the notification unit 105.

[0038] Even in the modified example, the notification unit 105 can notify the outside of information related to the suppression of high-frequency noise together with the notification of the result of the judgment. That is, when magnetic saturation occurs, information (cable length, cable type (with or without shield), appropriate filter inductor setting, etc.) that prompts a review of the stray capacitance on the power supply path can be notified. Furthermore, when magnetic saturation does not occur, the magnetic flux density B calculated by the calculator 106 can be notified together with the result of the judgment, and the difference amount (margin amount) between the magnetic flux density B calculated by the calculator 106 and the magnetic flux saturation density that is the threshold value 103a can be obtained and notified to the outside. By notifying the magnetic flux density B calculated by the calculator 106, the current suppression effect of high-frequency noise can be grasped, and by notifying the difference amount (margin amount) between the magnetic flux density B calculated by the calculator 102 and the magnetic flux saturation density, the margin degree until magnetic saturation is reached can be recognized. Even in the modified example, the number of cables that can be connected to a higher-level device (such as a power converter or power conversion system) and the number of electric motors that can be connected can be considered based on the margin amount, thereby improving usability regarding magnetic saturation countermeasures.

[0039] Even in this modified example, the magnetic saturation detection circuit 10a can determine the magnetic saturation occurring in the common mode choke coil 21 based on the magnetic flux density B calculated from the core magnetic flux. The magnetic saturation detection circuit 10a can notify the determination result to the outside in the same manner as in the first embodiment. For example, in the case of the noise filter 20 that integrally houses the magnetic saturation detection circuit 10a, if an LED or the like is provided on the housing to indicate that magnetic saturation has occurred, the notification unit 105 can turn on the LED based on the determination result. In the case where the noise filter 20 has a terminal that outputs a signal indicating the detection result, a higher-level device (such as a power converter or a power conversion system) that has the filter on its power supply path can output the detection result from the output terminal. Based on the signal, processing such as lighting an indicator such as an LED or displaying a notification on a display panel, etc. In the modified example, the magnetic saturation detection circuit 10a can also detect magnetic saturation of the choke coil during operation of equipment involving power conversion.

[0040] Example 2 Next, a motor drive system including the magnetic saturation detection circuit (10, 10a) according to the first embodiment will be described. In the following, the magnetic saturation detection circuits 10, 10a are also collectively referred to as the "magnetic saturation detection circuit 10b". The noise filter 20 is described as including a detection unit 29, and a physical quantity related to the magnetic saturation of the common mode choke coil 21 is measured through the detection unit 29. As described in the first embodiment, such physical quantities are the current flowing through the common mode choke coil 21 and the core magnetic flux of the core 21a. The former is measured by a current transformer CT or the like, and the latter is measured by a magnetic flux measuring coil 23 having n turns or the like. These physical quantities can be measured using an appropriate detector according to the configuration of the facility or equipment involving power conversion. The noise filter 20 may also be provided with the magnetic saturation detection circuit (10, 10a) and notify the equipment or the like that constitutes the motor drive system as appropriate.

[0041] <System configuration> FIG. 5 is a block diagram showing a schematic configuration of a motor drive system 1 according to a second embodiment of the present invention. FIG. 5 illustrates a system configuration including a motor driver 3 that converts power supplied from a main power supply 2 for driving a motor into a desired drive power and outputs the power to a motor 50. The main power supply 2 is, for example, a commercial AC power supply, and supplies AC power to the motor driver 3 through a power line W1. The motor driver 3 converts the supplied AC power into DC power through a converter 30, and outputs the converted DC power to an inverter 40 through a DC bus 14. A smoothing capacitor C that smoothes fluctuations in the DC power conducted to the inverter 40 through the DC bus 14 is provided on the DC bus 14. The inverter 40 drives a switching element on and off based on a control command from a motor control unit 12, converts the DC power output from the converter 30 into a desired AC power, and generates drive power for driving and controlling the motor 50. The generated drive power is output to the motor 50 through a power line W2. The motor 50 controls a workpiece, a robot arm, or the like to be controlled based on the driving power supplied from the motor driver 3. The main power supply 2 and the motor 50 are grounded to a reference potential G1 and a reference potential G2, respectively. In addition, the Y capacitor C3 of the noise filter 20 is connected to the FG of the motor driver 3.

[0042] The motor driver 3 includes a control unit 4, a current detector 13, a noise filter 20, a converter 30, and an inverter 40. The control unit 4 includes a magnetic saturation detection circuit 10b, a motor control unit 12, and a notification unit 15. The control unit 4 is a unit including, for example, a processor (such as a CPU), a memory, a gate driver, a communication interface circuit, and the like. The noise filter 20 is connected to the power line W1 via a pair of input terminals (TP1, TP2), and is connected to the converter 30 via a pair of output terminals (TP3, TP4). The detection unit 29 of the noise filter 20 is connected to the magnetic saturation detection circuit 10b of the control unit 4. The converter 30 includes, for example, a bridge circuit formed of rectifier elements (diode elements), and outputs DC power rectified from AC power by the bridge circuit to the direct bus 14. The inverter 40 has a power conversion circuit including switching elements (IGBT, thyristor, GTO, MOSFET, etc.) as its components, and drives the switching elements on and off (PWM control) in accordance with control commands from the motor control unit 12, converts the DC power input through the DC bus 14 into AC power, and generates the desired drive power. The generated drive power is supplied to the motor 50 through a power line W2, and the current flowing through the power line is detected by a current detector (CT, clamp-type current sensor, etc.) 13. The current detector 13 is, for example, a CT (Current Transformer) provided at the output end of the inverter 40 of the motor driver 3. ) The current value detected by the current detector 13 is input to a motor control unit 12 of the control unit 4. The motor control unit 12 uses the current value detected by the current detector 13 and the rotational speed of the motor 50 as feedback information, and generates a control command for controlling the rotational speed, torque, rotational position, etc. of the motor based on a predetermined torque command and a program stored in a memory or the like.

[0043] As described in the first embodiment, in the detection unit 29 of the noise filter 20, the current flowing through the common mode choke coil 21 from the pair of input terminals (TP1, TP2) to the pair of output terminals (TP3, TP4) is measured by a current transformer CT or the like, and the measured current value is input to the magnetic saturation detection circuit 10b. In addition, the core magnetic flux (Φ) of the core 21a of the common mode choke coil 21 is measured by a magnetic flux measuring coil 23 or the like, and the measured core magnetic flux (Φ) is input to the magnetic saturation detection circuit 10b.

[0044] In the magnetic saturation detection circuit 10b, a judgment is made as to whether or not magnetic saturation has occurred based on a comparison between the magnetic field strength H (A / m) indicating the strength of the magnetic field generated in the common mode choke coil 21 from the current value measured by the detection unit 29 and a threshold indicating the strength of the magnetic field at which magnetic saturation occurs. Alternatively, a judgment is made as to whether or not magnetic saturation has occurred based on a comparison between the core magnetic flux (Φ) of the core 21a measured by the detection unit 29 and the cross-sectional area S (m 2 ) and the magnetic flux density B (Wb / m 2 ) is calculated, and based on a comparison between the magnetic flux density B and a threshold value indicating the magnetic flux saturation density, it is determined whether or not magnetic saturation has occurred. The result of the determination by the magnetic saturation detection circuit 10b is output to the notification unit 15.

[0045] The notification unit 15 notifies the result of the determination by the magnetic saturation detection circuit 10b through a display device, LED, or the like provided on the housing of the motor driver 3. When the result of the determination indicates that magnetic saturation has occurred, for example, a message indicating that magnetic saturation has occurred may be displayed on a display panel provided in the motor driver 3, or an LED or the like indicating the magnetic saturation state may be turned on. The worker can grasp the magnetic saturation that has occurred in the noise filter 20 from the displayed message or the LED lighting. The notification unit 15 may also notify a message or an alarm sound that prompts the operator to change the length, wiring layout, or cable type (with or without shielding) of the power line W2 connecting the motor driver 3 and the motor 50.

[0046] The magnetic saturation detection circuit 10b may calculate the difference (margin amount) between the magnetic field strength H indicating the strength of the magnetic field generated in the common mode choke coil 21 and a threshold value, and output the calculated difference information (margin information) to the notification unit 15. Similarly, the magnetic saturation detection circuit 10b may calculate the difference between the magnetic flux density B and the magnetic flux saturation density which is the threshold value, and output the difference information to the notification unit 15. The notification unit 15 may display the margin amount output from the magnetic saturation detection circuit 10b on a display panel or the like, so that the number of motors 50 driven by the motor driver 3, the number of cables that can be connected, and the like can be grasped. Usability regarding monitoring of magnetic saturation can be improved.

[0047] <Control unit configuration> Fig. 6 is a diagram illustrating an example of a hardware configuration of the control unit 4 according to the second embodiment. As illustrated in Fig. 6, the control unit 4 is configured as a computer including a processor 111, a main storage device 112, an auxiliary storage device 113, a communication IF 114, and an input / output IF 115, which are connected to each other by a connection bus 116. The main storage device 112 and the auxiliary storage device 113 are recording media readable by the control unit 4. Each of the above components may be provided in a plurality of units, or some of the components may not be provided.

[0048] The processor 111 is a central processing unit that controls the entire control unit 4. The processor 111 is, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The processor 111 provides functions that meet a specific purpose by, for example, deploying a program stored in the auxiliary storage device 113 in an executable manner in the working area of ​​the main storage device 112 and controlling peripheral devices through the execution of the program. However, some or all of the functions provided by the processor 111 may be implemented by an ASIC (Application Specific Integrated Circuit), a GPU (Graphics Processing Unit), etc. Alternatively, some or all of the functions may be provided by a specialized device such as a field-programmable gate array (FPGA) or a numerical calculation processor. The present invention may be realized by a large scale integration (LSI) or other hardware circuits. .

[0049] The main memory device 112 and the auxiliary memory device 113 constitute the memory of the control unit 4. The main memory device 112 stores the programs executed by the processor 111, data processed by the processor, etc. The main memory device 112 includes a flash memory, a random access memory (RAM), and a read only memory (ROM). The auxiliary memory device 113 is a storage medium that stores the programs executed by the processor 111, etc., and operation setting information, etc. The auxiliary memory device 113 includes, for example, a hard-disk drive (HDD), a solid-state drive (SSD), an erasable programmable ROM (EPROM), a flash memory, a USB memory, a secure digital (SD) memory card, etc. The communication IF 114 is used for communication with a communication network. The communication IF 114 is an interface. The communication IF 114 can adopt an appropriate configuration according to the connection method with the communication network to be connected. The input / output IF 115 is an interface for inputting and outputting data between the input device and the output device equipped in the motor driver 3. Predetermined information is outputted through the input / output IF 115 to a display device such as an LCD, or an LED or the like provided on the housing of the motor driver 3. In addition, an operation instruction is accepted through the input / output IF 115 via an operation button or an operation panel provided on the housing, and processing based on the operation instruction is performed.

[0050] <Processing flow> 7 is a flowchart showing an example of magnetic saturation detection processing executed by the motor driver 3 according to the second embodiment. In this flow, a physical quantity related to the magnetic saturation detected by the detection unit 29 is measured, and the magnetic field strength H or the magnetic flux density B calculated based on the physical quantity is compared with a threshold value to determine the magnetic saturation occurring in the common mode choke coil 21. The result of the determination is notified to an operator or the like via a notification device (LED, display panel, speaker, etc.) provided on the housing. The processing of this flow is periodically executed at a predetermined periodic interval.

[0051] After the process starts, a physical quantity related to the magnetic saturation of the common mode choke coil 21 detected via the detection unit 29 of the noise filter 20 is obtained (step S101), and the process proceeds to step S102. The value of the current flowing through the common mode choke coil 21 detected by the current transformer CT, or the core magnetic flux of the core 21a detected by the magnetic flux measuring coil 23 is obtained.

[0052] In step S102, a magnetic field strength H or a magnetic flux density B indicating the strength of the magnetic field of the common mode choke coil 21 is obtained from the acquired physical quantities. The magnetic field strength H is obtained using equation (1) with the current value detected by the current transformer CT, the number of turns N specified in the specifications of the common mode choke coil 21, and the magnetic path length l as parameters. The magnetic flux density B is obtained using equation (2) with the core magnetic flux (Φ) detected by the magnetic flux measuring coil 23 and the cross-sectional area S of the core 21a as parameters. The magnetic field strength H or the magnetic flux density B obtained from the detected physical quantities is temporarily stored in a predetermined area of ​​the main storage unit 112 constituting the memory, and the process proceeds to step S103.

[0053] In step S103, the magnetic field strength H or the magnetic flux density B is compared with a threshold value. The process proceeds to step S104. The magnetic field strength H is compared with a threshold value representing the strength of the magnetic field causing magnetic saturation, and the magnetic flux density B is compared with a threshold value representing the saturation magnetic flux density. Such threshold values ​​are stored in advance in a memory or the like. In step S104, magnetic saturation is determined based on the comparison result. In step S104, if the magnetic field strength H or the magnetic flux density B exceeds the threshold value or is equal to or greater than the threshold value, it is determined that magnetic saturation has occurred (step S104, "Yes"), and the process proceeds to step S105; otherwise (step S104, "No"), the process proceeds to step S106.

[0054] In step S104, magnetic saturation may be determined on the condition that the threshold value is exceeded or the threshold value is exceeded for a certain period of time. For example, a flag may be set when the threshold value is exceeded or the threshold value is exceeded, a timer may be provided to count the period from the flag being set, and magnetic saturation may be determined to have occurred when the timer value is equal to or exceeds the certain period of time. If the threshold value falls below or equal to the threshold value within the certain period of time, the flag may be reset. This may prevent malfunctions due to, for example, the generation of a sudden surge current.

[0055] In step S105, the magnetic saturation occurring in the common mode choke coil 21 is notified. For example, an LED or the like provided on the housing of the motor driver 3, which indicates the magnetic saturation state, is turned on. A message indicating the occurrence of magnetic saturation may be notified on a display panel or the like provided on the housing, or the occurrence of magnetic saturation may be notified through an electronic sound or a speaker. The magnetic saturation occurring in the noise filter 20 is grasped based on the message displayed on the display panel or the notification by the LED lighting or electronic sound. The control unit 4 that executes step S105 may display on the display panel a message or the like that prompts the user to change the length, wiring arrangement, or cable type (with or without shielding) of the power line W2 connecting the motor driver 3 and the motor 50. It is possible to prompt the user to review the stray capacitance to ground between the motor driver 3 and the motor 50, which is a cause of the magnetic saturation occurring in the noise filter 20, or to install a noise filter having an appropriate inductor according to the operating environment. After the process of step S105, the process proceeds to step S107.

[0056] In step S106, the difference (margin amount) between the magnetic field strength H indicating the strength of the magnetic field obtained from the physical quantity detected by the detection unit 29 and the threshold value, or the difference between the magnetic flux density B and the magnetic flux saturation density which is the threshold value, is calculated, and the difference (margin amount) is displayed on a display panel or the like provided on the housing of the motor driver 3. Based on the margin amount or the like displayed on the display panel, the number of motors 50 that can be driven by the motor driver 3 and the number of cables that can be connected can be grasped. Note that, when the ground stray capacitance of each motor and the ground stray capacitance of each cable are held as known information, the control unit 4 that executes step S105 may display the number of motors that can be driven, the number of cables that can be connected, etc. on the display panel or the like based on the ground stray capacitance. Usability regarding magnetic saturation countermeasures can be improved. After the process of step S106, the process proceeds to step S107.

[0057] In step S107, the magnetic field strength H or magnetic flux density B used to determine magnetic saturation is recorded in a memory or the like. The magnetic field strength H or magnetic flux density B is stored in a predetermined area of ​​the main memory unit 103 in association with, for example, time information when the processing of this flow was executed and attribute information. Examples of the attribute information include the identification number of the noise filter 20, the identification number of the motor 50, and the identification number of the power line W2. When analyzing magnetic saturation, this can be used as information for understanding the setting environment, operating environment, etc. of the motor driver 3 when magnetic saturation detection was performed. After the processing of step S107, this routine is temporarily terminated.

[0058] As described above, in the motor driver 3 according to the second embodiment, noise filtering due to high frequency noise during operation is performed based on the physical quantity related to magnetic saturation detected by the detection unit 29. In the second embodiment, the magnetic saturation of the common mode choke coil 21 can be detected by the current transformer CT. In the second embodiment, the value of the current flowing through the common mode choke coil 21 is detected by the current transformer CT, and the magnetic field strength H is obtained. In addition, the core magnetic flux formed in the core 21a of the common mode choke coil 21 is detected by the magnetic flux measuring coil 23, and the magnetic flux density B is obtained. In the second embodiment, the magnetic field strength H is compared with a threshold value representing the strength of the magnetic field causing magnetic saturation, and the magnetic flux density B is compared with a threshold value representing the saturation magnetic flux density, and the presence or absence of magnetic saturation occurring in the common mode choke coil 21 can be determined.

[0059] When magnetic saturation occurs, the motor driver 3 according to the second embodiment can, for example, light an LED or the like provided on a housing or the like to indicate the magnetic saturation state, display a message indicating that magnetic saturation has occurred on a display panel or the like provided on the housing or the like, or notify the user by an electronic sound, a speaker, or the like. According to the second embodiment, magnetic saturation occurring in the common mode choke coil can be detected without stopping the operation of the motor driver 3.

[0060] The motor driver 3 according to the second embodiment may display on a display panel or the like a message encouraging the selection of a noise filter having an appropriate inductor according to the length of the power line W2 connecting the motor driver 3 and the motor 50, the wiring layout, the type of cable (with or without shielding), and the operating environment. It becomes possible to appropriately encourage a review of the equipment environment and operating environment in the facility in which the motor driver 3 is installed.

[0061] Furthermore, when magnetic saturation is not occurring, the motor driver 3 according to the second embodiment can calculate the difference between the current magnetic field strength H and the strength of the magnetic field at which magnetic saturation occurs, or the difference between the current magnetic flux density B and the magnetic flux saturation density, as a margin amount, and display it on a display panel, etc. An operator can grasp the number of motors 50 that can be driven by the motor driver 3, the number of cables that can be connected, etc., based on the margin amount, etc., displayed on a display panel, etc., and therefore usability regarding magnetic saturation countermeasures can be improved.

[0062] (others) The above embodiment is merely an example, and the disclosure of the present embodiment may be modified as appropriate without departing from the spirit of the present disclosure. The processes and means described in the present disclosure may be freely combined and implemented as long as no technical contradiction occurs.

[0063] Furthermore, a process described as being performed by one device may be shared and executed by multiple devices. Or, a process described as being performed by different devices may be executed by one device. In a computer system, the hardware configuration for implementing each function can be flexibly changed.

[0064] <Computer-readable recording medium> A program for causing an information processing device or other machine or device (hereinafter, computer, etc.) to realize any of the above functions can be recorded on a recording medium readable by the computer, etc. Then, the computer, etc. can provide the function by reading and executing the program from the recording medium.

[0065] Here, a computer-readable recording medium refers to a recording medium that stores information such as data and programs through electrical, magnetic, optical, mechanical, or chemical action and can be read by a computer, etc. Among such recording media, those that can be removed from a computer, etc. include, for example, flexible disks, magneto-optical disks, CD-ROMs, CD-R / Ws, DVDs, Blu-ray disks, DATs, 8mm tapes, memory cards such as flash memory, etc. Furthermore, examples of recording media that are fixed to a computer, etc. include hard disks and ROMs.

[0066] In the following, the components of the present invention will be described with reference to the reference numerals in the drawings in order to make it possible to compare the components of the present invention with the configurations of the embodiments. <Invention 1> A detection unit (CT, 23) for detecting a physical quantity related to magnetic saturation of a common mode choke coil (21) provided in series in a path from a power source; a determination unit (11) that determines whether magnetic saturation has occurred in the common mode choke coil (21) on condition that the strength of the magnetic field of the common mode choke coil (21) estimated from the detected physical quantity satisfies a predetermined standard; and a notification unit (15) that notifies an external device of a result of the determination; A magnetic saturation detection circuit (10, 10a, 10b) comprising: <Invention 2> The magnetic saturation detection circuit (10, 10a, 10b) according to claim 1, wherein the notification unit (15) notifies information related to suppression of high-frequency noise in a circuit including the power supply. [Explanation of symbols]

[0067] 1 Motor drive system 2 Main power 3 Motor driver (drive device) 4. Control Unit 10, 10a, 10b Magnetic saturation detection circuit 11 Judgment section 15. Notification Department 20 Noise Filter 21 Common mode choke coil 21a Core, 21b, 21c Winding 23 Magnetic flux measuring coil 29 Detection unit 101 Low-pass filter 102, 106 Arithmetic section 103, 103a Threshold 104 Comparator 105 Notification Department 111 Processor 112 Main storage 113 Auxiliary storage 114 Communication Interface 115 Input / Output Interface 116 Connection Bus CT Current transformer

Claims

1. a detection unit that detects a physical quantity related to magnetic saturation of a common mode choke coil that is provided in series with a path from a power supply; a determination unit that determines whether magnetic saturation has occurred in the common mode choke coil, on condition that the strength of the magnetic field of the common mode choke coil estimated from the detected physical quantity satisfies a predetermined standard; and a notification unit that notifies an external device of information related to suppression of high frequency noise, including information that prompts a review of stray capacitance on a power supply path, together with the result of the determination; A magnetic saturation detection circuit comprising:

2. The detection unit detects a current flowing through a common mode choke coil, 2. The magnetic saturation detection circuit according to claim 1, wherein the determination unit estimates a magnetic field strength of the common mode choke coil from the detected current value, and determines that magnetic saturation has occurred in the common mode choke coil on the condition that the estimated magnetic field strength exceeds a first threshold value.

3. The detection unit detects a magnetic flux of a common mode choke coil, 2. The magnetic saturation detection circuit according to claim 1, wherein the determination unit estimates a magnetic flux density of the common mode choke coil from the detected magnetic flux, and determines that magnetic saturation has occurred in the common mode choke coil on the condition that the estimated magnetic flux density exceeds a second threshold value.

4. A noise filter comprising the magnetic saturation detection circuit according to any one of claims 1 to 3, The noise filter, wherein the notification unit further notifies information related to a degree of noise removal by the noise filter.

5. A motor driver comprising the magnetic saturation detection circuit according to any one of claims 1 to 3 or the noise filter according to claim 4, A motor driver which issues a notification to prompt a predetermined process based on information notified from the magnetic saturation detection circuit or the noise filter.

6. 6. The motor driver according to claim 5, wherein the predetermined processing prompts replacement of a power line connecting the motor driver and a motor to which driving power generated by the motor driver is supplied, or a review of a stray capacitance to ground existing between the power line and the motor.

7. 6. The motor driver according to claim 5, wherein the magnetic saturation detection circuit, when magnetic saturation does not occur in the common mode choke coil, calculates a margin amount until magnetic saturation occurs and notifies the calculated margin amount.

8. A physical quantity related to the magnetic saturation of a common mode choke coil that is provided in series with a path from a power supply is detected. determining that magnetic saturation has occurred in the common mode choke coil on the condition that the strength of the magnetic field of the common mode choke coil estimated from the detected physical quantity satisfies a predetermined standard; notifying, to an external device, information related to suppression of high frequency noise, including information prompting a review of stray capacitance on a power supply path, together with the result of the determination; and 13. A method for detecting magnetic saturation comprising:

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