Protection device provided on ac input side of converter and converter having same
Patent Information
- Application Number
- PCT/JP2025/008956
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-11
- Publication Date
- 2026-09-17
Smart Images
Figure JP2025008956_17092026_PF_FP_ABST
Abstract
Description
A protective device provided on the AC input side of a converter, and a converter incorporating the same.
[0001] This disclosure relates to a protective device provided on the AC input side of a converter and a converter incorporating the same.
[0002] In a motor drive system, AC power supplied from an AC power source is converted to DC power by a converter and output to a DC link. Furthermore, an inverter converts the DC power in the DC link back to AC power for motor drive and supplies it to the motor. If a malfunction occurs in the motor drive system, an overcurrent may flow from the AC input side to the converter, potentially damaging the motor drive system. Therefore, protective devices are sometimes provided on the AC input side of the converter.
[0003] International Publication No. 2024 / 013889, Japanese Patent Publication No. 2010-259254
[0004] A protective device installed on the AC input side of a converter is provided with a switch that selectively switches between conduction and interruption operations for the power line between the AC power source and the converter. If a highly responsive semiconductor switching element is used as the switch, it is possible to immediately cause the semiconductor switching element to perform an interruption operation after detecting an abnormality. On the other hand, there is a problem that the frequency of surges increases because the interruption operation is likely to occur while current is still flowing through the semiconductor switching element. Therefore, it is desirable to reduce the frequency of surges that occur when the semiconductor switching element in the protective device is caused to perform an interruption operation in response to abnormality detection in the protective device installed on the AC input side of the converter.
[0005] According to one aspect of the present disclosure, the protective device comprises: a switch unit having semiconductor switching elements provided in each phase of a three-phase power line between a three-phase AC power source and a converter, which independently perform conduction and interruption operations for each phase of the three-phase power line; and a diode connected in antiparallel to the semiconductor switching elements; an input current detection unit that detects the current of each phase flowing from the three-phase AC power source to the AC input side of the converter via the three-phase power line; a storage unit that stores a table that defines the relationship between the nature of an abnormality and the degree of urgency of the interruption operation to be performed when the abnormality occurs; an abnormality detection unit that detects abnormalities occurring in a system including the converter; and a control unit that controls the conduction and interruption operations of the semiconductor switching elements. The control unit controls all three-phase semiconductor switching elements to perform an interruption operation immediately from the time of abnormality detection if an abnormality corresponding to a high degree of urgency in the table is detected, and controls the semiconductor switching elements to perform an interruption operation sequentially from the phase in which the current value detected by the input current detection unit falls within a predetermined current range.
[0006] This figure shows a protective device according to an embodiment of the disclosure. This is a flowchart showing the operation flow of the protective device according to an embodiment of the disclosure.
[0007] The following describes embodiments of the protective device provided on the AC input side of the converter with reference to the drawings. In the following description, components having the same or similar function are denoted by the same reference numerals. Duplication of these components may be omitted. The drawings have been scaled appropriately for ease of understanding.
[0008] Furthermore, in the following description, terms are defined in consideration of the function in the embodiments of this disclosure, and therefore terms may vary depending on the intent or convention of the user, operator, etc. For example, “connected” means “electrically connected.” A converter that converts AC power to DC power and outputs it may also be called a “rectifier,” “rectifier device,” “rectifier circuit,” or “forward converter.” An inverter that converts DC power to AC power and outputs it may also be called an “inverse converter.” “DC link” refers to the circuit portion that electrically connects the DC output side of the converter and the DC input side of the inverter. “DC link” may also be called a “DC link circuit,” “DC link section,” “DC link,” “DC link circuit,” “DC link section,” “DC bus,” or “DC intermediate circuit.” “DC link voltage” refers to the potential difference between the positive potential on the positive power line of the DC link and the negative potential on the negative power line. “Input current” refers to the current that flows from the three-phase AC power source to the converter via the three-phase power lines. In the context of semiconductor switching elements, "on" means that the element is closed and the current path through the element is open. "Off" means that the element is open and the current path through the element is closed. "On and off control" is sometimes written as "on-off control." The numerical examples provided below are just examples, and other values may be used. Also, the units for each parameter may be omitted.
[0009] <Configuration of the protective device according to the embodiment of the present disclosure> Figure 1 is a diagram showing a protective device according to the embodiment of the present disclosure.
[0010] The protective device 1 according to the embodiment of this disclosure is provided on the AC input side of the converter 2. The protective device 1 according to the embodiment of this disclosure is applicable to a power conversion system including the converter 2 and the inverter 4. Here, as an example, the power conversion system is provided as a motor drive device 100. The motor 6 can be driven by the motor drive device 100 connected to a three-phase AC power supply 5. Examples of the three-phase AC power supply 5 include a three-phase AC 400V power supply, a three-phase AC 200V power supply, and a three-phase AC 600V power supply. The type of motor 6 is not particularly limited and may be an induction motor or a synchronous motor, for example. The number of phases of the motor 6 is not particularly limited to the embodiment of this disclosure and may be three-phase or single-phase. Here, as an example, the motor 6 is provided as three-phase. The number of motors 6 is not particularly limited to the embodiment of this disclosure and may be multiple. Here, as an example, the motor 6 is provided as one. Machines on which the motor 6 is provided include, for example, machine tools and robots. The motor 6 is used as a drive source for, for example, the feed axis or spindle of a machine tool, or the arm of a robot.
[0011] As shown in Figure 1, the motor drive device 100 according to the embodiment of the present disclosure comprises a protection device 1, a converter 2, a smoothing capacitor 3, an inverter 4, a motor control device 8, a higher-level control device 9, a voltage detection unit 16, a temperature detection unit 17, and other circuits (not shown). Power supplies for driving each of these components, such as the protection device 1, the motor control device 8, the higher-level control device 9, the voltage detection unit 16, and the temperature detection unit 17, are not shown.
[0012] The three-phase AC power supply 5 and the AC input side of the converter 2 are connected by R-phase power line 51R, S-phase power line 51S, and T-phase power line 51T.
[0013] Converter 2 is a rectifier that converts AC power supplied from the AC input side into DC power and outputs this DC power to DC link 7, which is the DC output side of converter 2. Converter 2 is composed of a three-phase bridge circuit. Examples of converter 2 include PWM switching control type rectifiers, diode rectifiers, and 120-degree energization type rectifiers. In the example shown in Figure 1, converter 2 is composed of a PWM switching control type rectifier. For example, when converter 2 is composed of a PWM switching control type rectifier or a 120-degree energization type rectifier, it consists of a bridge circuit of semiconductor switching elements and diodes connected in antiparallel thereto, and each semiconductor switching element is controlled on / off according to a drive command received from the higher-level control device 9 to perform AC-DC power conversion. In this case, examples of semiconductor switching elements include IGBTs, FETs, thyristors, GTOs, and transistors, but other semiconductor switching elements may also be used. Diodes and semiconductor switching elements provided in converter 2 are not shown in the figure. The AC input side of converter 2 may include an AC reactor or an AC line filter, but these are omitted from the illustration here.
[0014] The smoothing capacitor 3 is provided in the DC link 7 between the DC output side of the converter 2 and the DC input side of the inverter 4. The smoothing capacitor 3 is sometimes referred to as a "DC link capacitor" or "DC link capacitor". The smoothing capacitor 3 has the function of suppressing the pulsation component of the DC output of the converter 2 and the function of storing the DC power used by the inverter 4 to generate AC power. Examples of smoothing capacitors 3 include electrolytic capacitors and film capacitors. The pre-charging circuit for pre-charging the smoothing capacitor 3 is not shown in the figure. In the example shown in Figure 1, there is one smoothing capacitor 3, but if the DC link voltage is a large voltage, multiple (for example, two) smoothing capacitors connected in series may be used.
[0015] The DC input side of the inverter 4 and the DC output side of the converter 2 are connected via the positive power line 52P and the negative power line 52N of the DC link 7. The inverter 4 consists of a bridge circuit of semiconductor switching elements and diodes connected in antiparallel thereto. The semiconductor switching elements and diodes provided within the inverter 4 are not shown in the figure. The inverter 4 is configured as a three-phase bridge circuit when the motor 6 is a three-phase AC motor, and as a single-phase bridge circuit when the motor 6 is a single-phase AC motor. In the example shown in Figure 1, the motor 6 is a three-phase AC motor, so the inverter 4 is configured as a three-phase bridge circuit. Examples of semiconductor switching elements include IGBTs, FETs, thyristors, GTOs, and transistors, but other semiconductor switching elements may also be used.
[0016] The inverter 4's power conversion operation is controlled, for example, by a PWM switching control method, based on the drive command generated by the motor control device 8. Specifically, the inverter 4 receives a drive command from the motor control device 8, converts the DC power supplied from the DC input side to the DC link 7 into AC power, and supplies this AC power to the motor 6 on the AC output side. The inverter 4 also receives a drive command from the motor control device 8, converts the AC power regenerated by the motor 6 into DC power, and returns it to the DC link 7.
[0017] The motor control device 8 generates drive commands for the inverter 4 based on the motor speed (speed feedback), current flowing through the motor windings (current feedback), a predetermined torque command, and the motor operation program of the motor 6, all of which are obtained via the encoder 61, in order to control the speed, torque, or rotor position of the motor 6. Note that the configuration of the motor control device 8 defined here is merely an example, and the configuration of the motor control device 8 may be defined to include terms such as a position command generation unit, a torque command generation unit, and a switching command generation unit.
[0018] The higher-level control unit 9 comprehensively controls the motor control unit 8, the control unit within the protection device 1, and other control units. For example, if the machine on which the motor 6 is installed is a machine tool, the numerical control unit corresponds to the higher-level control unit 9, and if the machine on which the motor 6 is installed is a robot, the robot controller corresponds to the higher-level control unit 9. Alternatively, the higher-level control unit 9 (numerical control unit, robot controller) may perform control equivalent to that of the motor control unit 8.
[0019] The voltage detection unit 16 and the temperature detection unit 17 are provided within a converter control device (not shown) that controls the converter 2 and a motor control device 8 that controls the inverter 4.
[0020] The voltage detection unit 16 detects the voltage in each circuit within the motor drive unit 100. For example, the voltage detection unit 16 detects the DC link voltage, which is the potential difference between the positive potential on the positive power line 52P of the DC link 7 and the negative potential on the negative power line 52N. Alternatively, the voltage detection unit 16 detects the terminal voltage of the smoothing capacitor 3 provided on the DC link 7. Furthermore, the voltage detection unit 16 detects the AC voltage (phase voltage or line voltage) on the AC input side of the converter 2. The data regarding the values of each voltage detected by the voltage detection unit 16 is used for abnormality detection processing. The data regarding the values of each voltage detected by the voltage detection unit 16 may also be used to control the power conversion operation of the inverter 4 by the motor control device 8, or to control the power conversion of the converter 2.
[0021] The temperature detection unit 17 detects the temperature at each location via temperature sensors (not shown) provided at various locations within the motor drive unit 100. Each temperature sensor is located, for example, near the semiconductor switching elements and / or diodes in the converter 2, near the semiconductor switching elements and / or diodes in the inverter 4, near the smoothing capacitor 3, and near the semiconductor switching elements S in the switch unit 11. R S S , and S T It is preferable to install it in the vicinity of the motor 6, such as on a heat-generating part (e.g., the iron core or windings). The data regarding the temperature values detected by the voltage detection unit 16 is used for abnormality detection processing.
[0022] A protection device 1 according to an embodiment of the present disclosure includes a switch unit 11, an input current detection unit 12, a storage unit 13, an abnormality detection unit 14, a control unit 15, a receiving unit 18, and other circuits (not shown). In Fig. 1, the protection device 1 and the converter 2 are shown as separate components; however, as a modification, the protection device 1 may be built in the converter 2 or a control device (not shown) that controls the converter 2.
[0023] The switch unit 11 in the protection device 1 is provided on each of an R-phase power line 51R, an S-phase power line 51S, and a T-phase power line 51T. The switch unit 11 includes a semiconductor switching element S R , S S , and S T . The R-phase semiconductor switching element S R is provided on the R-phase power line 51R, the S-phase semiconductor switching element S S is provided on the S-phase power line 51S, and the T-phase semiconductor switching element S T is provided on the T-phase power line 51T. A diode D R is connected in anti-parallel to the semiconductor switching element S R , a diode D S is connected in anti-parallel to the semiconductor switching element S S , and a diode D T is connected in anti-parallel to the semiconductor switching element S T . Examples of the semiconductor switching elements S R , S S , and S T include IGBTs, FETs, thyristors, GTOs, and transistors, but other semiconductor switching elements may also be used.
[0024] The conducting operation (on operation) and interrupting operation (off operation) of the semiconductor switching elements S R , S S , and S T are independently controlled by the control unit 15 for each phase.
[0025] The R-phase semiconductor switching element S RThe device selectively performs a conduction operation that allows current to flow from the three-phase AC power supply 5 to the AC input side of the converter 2 via the R-phase power line 51R when it is ON, and a disconnection operation that prevents current from flowing from the three-phase AC power supply 5 to the AC input side of the converter 2 via the R-phase power line 51R when it is OFF.
[0026] S-phase semiconductor switching element S S The device selectively performs a conduction operation that allows current to flow from the three-phase AC power supply 5 to the AC input side of the converter 2 via the S-phase power line 51S when it is ON, and a disconnection operation that prevents current from flowing from the three-phase AC power supply 5 to the AC input side of the converter 2 via the S-phase power line 51S when it is OFF.
[0027] T-phase semiconductor switching element S T The device selectively performs a conduction operation that allows current to flow from the three-phase AC power supply 5 to the AC input side of the converter 2 via the T-phase power line 51T when it is ON, and a disconnection operation that prevents current from flowing from the three-phase AC power supply 5 to the AC input side of the converter 2 via the T-phase power line 51T when it is OFF.
[0028] Semiconductor switching element S R S S , and S T For each of these, surge protection elements (not shown) are mounted on the three-phase power lines 51R, 51S, and 51T on the side to which the three-phase AC power supply 5 is connected (i.e., the side to which the three-phase AC power supply 5 of the protection device 1 is connected). Examples of surge protection elements include overvoltage protection elements such as varistors and surge arresters. Alternatively, instead of surge protection elements, film capacitors may be provided between the three-phase power lines 51R, 51S, and 51T on the side to which the three-phase AC power supply 5 is connected (i.e., the side to which the three-phase AC power supply 5 of the protection device 1 is connected).
[0029] The input current detection unit 12 detects the current of each phase flowing from the three-phase AC power supply 5 to the AC input side of the converter 2 via the R-phase power line 51R, the S-phase power line 51S, and the T-phase power line 51T. Here, as an example, the value of the current flowing from the three-phase AC power supply 5 toward the AC input side of the converter 2 is taken as positive, and the value of the current flowing from the AC input side of the converter 2 toward the three-phase AC power supply 5 is taken as negative. The data regarding the current values of each phase detected by the input current detection unit 12 is sent to the abnormality detection unit 14.
[0030] The receiving unit 18 receives alarm signals output from equipment related to the motor drive device 100. For example, the receiving unit 18 receives an alarm signal output from the motor control device 8. Also, for example, the receiving unit 18 receives an alarm signal output from the higher-level control device 9. Generally, the motor control device 8 and the higher-level control device 9 have a function to detect whether or not an abnormality has occurred in each part, such as the converter 2, inverter 4, DC link 7, and motor 6. When the motor control device 8 and / or the higher-level control device 9 detect an abnormality, an alarm signal corresponding to the content (type) of the abnormality is output. Identification information corresponding to the content (type) of the abnormality may be added to the alarm signal. When the receiving unit 18 receives an alarm signal from the motor control device 8 and / or the higher-level control device 9, it forwards the alarm signal to the abnormality detection unit 14.
[0031] The abnormality detection unit 14 detects abnormalities occurring in the motor drive device 100 based on the current value detected by the input current detection unit 12 and / or the alarm signal received by the receiving unit 18. Details of the abnormality detection process by the abnormality detection unit 14 will be described later.
[0032] In the embodiments of this disclosure, the semiconductor switching element S in the switch unit 11 is selected according to the degree of urgency of the shutdown operation of the switch unit 11 to be performed when an abnormality occurs. R S S , and S T The details of the shutdown operation change. In other words, if a highly urgent abnormality occurs, all three-phase semiconductor switching elements S will be shut down immediately after the abnormality is detected. R S S , and ST The system is shut off in response to the above. In addition, if a low-priority anomaly occurs, the system is shut off sequentially starting with the semiconductor switching elements of the phases in which the current flowing through the R-phase power line 51R, S-phase power line 51S, and T-phase power line 51T falls within a predetermined current range. An example of a table that associates the content (type) of anomaly with the level of urgency of that anomaly will be described later.
[0033] The control unit 15 controls the semiconductor switching element S R S S , and S T It controls the conduction (on) and interruption (off) operations. More details are as follows:
[0034] The control unit 15 controls the semiconductor switching element S while the abnormality detection unit 14 does not detect an abnormality in the motor drive device 100 (i.e., normal value). R S S , and S T Controls the device to conduct electricity (turn on).
[0035] When the abnormality detection unit 14 detects an abnormality occurring in the motor drive device 100, the control unit 15, as described below, refers to the table stored in the storage unit 13 and performs a shut-off operation (off operation) corresponding to the severity of the abnormality to the semiconductor switching element S R S S , and S T Control.
[0036] In other words, if the abnormality detection unit 14 detects an abnormality in the table that is associated with a high degree of urgency, the control unit 15 will check all three-phase semiconductor switching elements S R S S The system controls the operation so that both and S shut off simultaneously and immediately.
[0037] Furthermore, if the abnormality detection unit 14 detects an abnormality in the table that is associated with a low level of urgency, the control unit 15 will check all three-phase semiconductor switching elements S R S S , and S TThe control unit 15 repeatedly determines whether the value of the current detected by the input current detection unit 12 falls within a predetermined current range until the cutoff operation is performed. Then, the control unit 15 controls the three-phase semiconductor switching element S R S S , and S T The semiconductor switching elements of the phases in which the current flowing from the three-phase AC power supply 5 to the AC input side of the converter 2, as detected by the input current detection unit 12, falls within a predetermined current range, are sequentially shut off. Here, the "predetermined current range" may be set to, for example, "0 amperes or less," "less than 0 amperes," or "a small value near 0 amperes or less." The numerical examples given here are just examples, and other numerical values may be used.
[0038] In the embodiments of this disclosure, in order to implement a shutdown operation corresponding to the content (type) of the abnormality as described above, a table is prepared in advance that associates the content (type) of the abnormality with the degree of urgency of the abnormality, and is stored in the storage unit 13. The storage unit 13 may be a rewritable storage device, so that even after the "table" has been set, the table can be changed as needed.
[0039] As described above, according to the embodiment of this disclosure, when the abnormality detection unit 14 detects an abnormality in the table that is associated with a low degree of urgency, the three-phase semiconductor switching element S R S S , and S T The semiconductor switching elements of the phase in which the current value detected by the input current detection unit 12 falls within a predetermined current range (for example, 0 amperes or less) are sequentially shut off. As a result, the semiconductor switching elements S R S S , and S T In either case, the interruption operation will not be performed while current is flowing, so no surge will occur. On the other hand, if the abnormality detection unit 14 detects an abnormality that is associated with a high degree of urgency in the table, all three-phase semiconductor switching elements S R S S, and S immediately shuts off from the time of abnormality detection, thereby prioritizing protection for the converter 2. According to the embodiment of this disclosure, the semiconductor switching element S in the switch unit 11 responds to the degree of urgency of the shut-off operation when an abnormality occurs. R S S , and S T Since the nature of the shutdown operation changes, the overall frequency of surges associated with the shutdown operation can be reduced.
[0040] <Abnormality detection processing by the abnormality detection unit> The abnormality detection unit 14 detects abnormalities occurring in the motor drive device 100 based on the current value detected by the input current detection unit 12, the voltage values detected by the voltage detection unit 16, and / or the alarm signal received by the receiving unit 18. Here are some examples of the forms of abnormality detection processing by the abnormality detection unit 14.
[0041] In the first embodiment, the abnormality detection unit 14 detects that an abnormality has occurred when the value of the current detected by the input current detection unit 12 exceeds a predetermined current threshold. For example, semiconductor switching element S R S S , and S T When the system is conducting, an overcurrent flows if a ground fault or short circuit occurs in the R-phase power line 51R, S-phase power line 51S, and / or T-phase power line 51T. A current threshold is set to distinguish whether the current detected by the input current detection unit 12 is an overcurrent due to an abnormality or a normal current. The current threshold may be stored in a rewritable memory device (not shown) and rewritable by an external device, so that even after the current threshold has been set, it can be changed to an appropriate value as needed.
[0042] In the second embodiment, the abnormality detection unit 14 detects that an abnormality has occurred when the receiving unit 18 receives an alarm signal. The motor control device 8 and the higher-level control device 9 have functions to detect whether or not an abnormality has occurred in each part, such as the converter 2, inverter 4, DC link 7, and motor 6.
[0043] For example, if the voltage in any circuit within the motor drive device 100 detected by the voltage detection unit 16 falls outside a predetermined voltage range, the motor control device 8 and / or the higher-level control device 9 will output an alarm signal with identification information corresponding to the nature of the abnormality, indicating that an abnormality has occurred. For example, semiconductor switching element S R S S , and S T When the semiconductor switching element S is conducting, if a ground fault or short circuit occurs in the R-phase power line 51R, the S-phase power line 51S, and / or the T-phase power line 51T, the AC voltage (phase voltage or line voltage) on the AC input side of the converter 2 detected by the voltage detection unit 16 will be significantly smaller or significantly larger than the normal value. For example, semiconductor switching element S R S S , and S T When the motor drive unit 100 is operating due to conduction, if a short circuit or ground fault occurs in the DC link 7, the DC link voltage detected by the voltage detection unit 16 will be significantly lower or significantly higher than the normal value. For example, semiconductor switching element S R S S , and S T When the motor drive unit 100 is operating due to conduction, if a short circuit occurs in the smoothing capacitor 3, the terminal voltage of the smoothing capacitor 3 detected by the voltage detection unit 16 will be significantly smaller or significantly larger than the normal value. In order to distinguish whether the voltage detected by the voltage detection unit 16 is the voltage during an abnormality or the voltage during normal operation, a "voltage range" is set so that an abnormality can be determined. The voltage range may be stored in a rewritable memory device (not shown) and can be rewritten by an external device, so that even after the voltage range has been set, it can be changed to an appropriate value as needed.
[0044] For example, if the temperature detected by the temperature detection unit 17 exceeds a predetermined temperature threshold, the motor control device 8 and / or the higher-level control device 9 will output an alarm signal with identification information corresponding to the nature of the abnormality, indicating that an abnormality has occurred. For example, if a heat generation abnormality such as overheating occurs in the motor drive unit 100, the temperature detected by the temperature detection unit 17 will be higher than the normal temperature. A temperature threshold is set to distinguish whether the temperature detected by the temperature detection unit 17 is the temperature at the time of the abnormality or the normal temperature. The temperature threshold may be stored in a rewritable storage device (not shown) and rewritable by an external device, so that even after the temperature threshold has been set, it can be changed to an appropriate value as needed. As a modified example, the motor control device 8 and / or the higher-level control device 9 may detect that overheating has occurred in the motor drive unit 100 when a cooling device (not shown) provided in the motor drive unit 100 has stopped abnormally, and output an alarm signal with identification information corresponding to the nature of the abnormality.
[0045] When the motor control device 8 and / or the higher-level control device 9 detect an abnormality, an alarm signal is output with identification information corresponding to the nature of the abnormality added to it. When the receiving unit 18 receives an alarm signal from the motor control device 8 and / or the higher-level control device 9, it forwards the alarm signal to the abnormality detection unit 14. The abnormality detection unit 14 can also determine the nature (type) of the abnormality based on the identification information added to the alarm signal.
[0046] <Relationship between abnormality and the urgency of the shutoff operation> In the embodiments of this disclosure, the semiconductor switching element S in the switch unit 11 is determined according to the degree of urgency of the shutoff operation of the switch unit 11 that should be performed when an abnormality occurs. R S S , and S T The content of the shutdown operation changes. In order to implement shutdown operations according to the content (type) of the abnormality, a table is prepared in advance that associates the content (type) of the abnormality with the degree of urgency of the abnormality, and is stored in the storage unit 13.
[0047] Examples of abnormalities that can be associated with a high degree of urgency for tripping include overcurrents occurring in any of the R-phase power line 51R, S-phase power line 51S, and T-phase power line 51T, short circuits in the smoothing capacitor 3, abnormalities indicated by alarm signals output from the motor control device 8, and abnormalities indicated by alarm signals output from the higher-level control device 9. Abnormalities other than those listed here may also be included as abnormalities associated with a high degree of urgency.
[0048] Examples of abnormalities that can be associated with a low level of urgency for shutoff operations include overvoltage occurring in any circuit of the motor drive unit 100, abnormalities in the converter 2, abnormalities in the inverter 4, abnormalities in the motor 6, overheating occurring in equipment within the motor drive unit 100, and abnormalities indicated by alarm signals output from the motor control device 8, and abnormalities indicated by alarm signals output from the higher-level control device 9. Abnormalities other than those listed here may also be included as abnormalities associated with a low level of urgency.
[0049] The relationship between abnormalities and the urgency of the shutdown operation described above is just one example. For example, the user of the motor drive device 100 may arbitrarily set the relationship between abnormalities and the urgency of the shutdown operation. For example, there are various types of abnormalities indicated by alarm signals output from the motor control device 8, and the urgency of the shutdown operation will differ depending on the type of abnormality. Also, for example, there are various types of abnormalities indicated by alarm signals output from the higher-level control device 9, and the urgency of the shutdown operation will differ depending on the type of abnormality. A table associating the content (type) of an abnormality with the urgency of that abnormality is stored in the storage unit 13. The storage unit 13 may be a rewritable storage device, so that even after the "table" has been set, it can be changed as needed.
[0050] <Operation of the protective device according to the embodiment of this disclosure> Figure 2 is a flowchart showing the operation flow of the protective device according to the embodiment of this disclosure.
[0051] When the motor drive unit 100 is operating, in step S101, the control unit 15 determines whether or not the abnormality detection unit 14 has detected an abnormality.
[0052] If the abnormality detection unit 14 determines in step S101 that it has detected an abnormality, in step S102 the control unit 15 refers to the table stored in the storage unit 13 and determines whether the abnormality detected by the abnormality detection unit 14 is an abnormality of high urgency or low urgency requiring a shutdown operation.
[0053] If it is determined in step S102 that the interruption operation is an abnormality with a high degree of urgency, then in step S103 the control unit 15 immediately interrupts all three-phase semiconductor switching elements S R S S , and S T Control is performed to shut off the semiconductor switching elements S in the three phases. R S S , and S T The system will perform a blocking operation, and then the process will terminate.
[0054] If it is determined in step S102 that the abnormality is of low urgency for the tripping operation, in step S104 the control unit 15 determines whether the current flowing through the R-phase power line 51R detected by the input current detection unit 12 is within a predetermined current range (for example, 0 amperes or less).
[0055] If, in step S104, it is determined that the current flowing through the R-phase power line 51R is within a predetermined current range (for example, 0 amperes or less), then in step S105, the control unit 15 controls the R-phase semiconductor switching element S R Control is performed to shut off the R-phase semiconductor switching element S. R The device performs a shutoff operation, and then proceeds to step S106.
[0056] If it is not determined in step S104 that the current flowing through the R-phase power line 51R is within a predetermined current range (for example, 0 amperes or less), the process proceeds to step S106.
[0057] In step S106, the control unit 15 determines whether the current flowing through the S-phase power line 51S detected by the input current detection unit 12 is within a predetermined current range (for example, 0 amperes or less).
[0058] If it is determined in step S106 that the current flowing through the S-phase power line 51S is within a predetermined current range (for example, 0 amperes or less), in step S107, the control unit 15 controls the S-phase semiconductor switching element S S to perform a cutoff operation. In response to this, the S-phase semiconductor switching element S S performs the cutoff operation, and then the process proceeds to step S108.
[0059] If it is not determined in step S106 that the current flowing through the S-phase power line 51S is within the predetermined current range (for example, 0 amperes or less), the process proceeds to step S108.
[0060] In step S108, the control unit 15 determines whether the current flowing through the T-phase power line 51T detected by the input current detection unit 12 is within a predetermined current range (for example, 0 amperes or less).
[0061] If it is determined in step S108 that the current flowing through the T-phase power line 51T is within a predetermined current range (for example, 0 amperes or less), in step S109, the control unit 15 controls the T-phase semiconductor switching element S T to perform a cutoff operation. In response to this, the T-phase semiconductor switching element S T performs the cutoff operation, and then the process proceeds to step S110.
[0062] If it is not determined in step S108 that the current flowing through the T-phase power line 51T is within the predetermined current range (for example, 0 amperes or less), the process proceeds to step S110.
[0063] In step S110, the control unit 15 determines whether all three-phase semiconductor switching elements S R , S S , and S T have performed the cutoff operation.
[0064] In step S110, if it is not determined that all three-phase semiconductor switching elements S R , S S , and S T have performed the cutoff operation, the process returns to step S104.
[0065] In step S110, when it is determined that all three-phase semiconductor switching elements S R , S S , and S T have performed a shutoff operation, the process ends.
[0066] The processes of steps S101 to S110 are repeatedly executed at a predetermined cycle. Note that the process consisting of steps S104 and S105, the process consisting of steps S106 and S107, and the process consisting of steps S108 and S109 may be executed with their order changed.
[0067] <Processor and Memory> The protection device 1 is provided with at least one processor serving as an arithmetic processing unit. Examples of the arithmetic processing unit include IC, LSI, CPU, MPU, DSP, etc. The arithmetic processing unit includes an input current detection unit 12, an abnormality detection unit 14, a control unit 15, a voltage detection unit 16, a temperature detection unit 17, a reception unit 18, and other processing units. Each of these units included in the arithmetic processing unit is, for example, a functional module implemented by a program executed on the processor. For example, when the input current detection unit 12, the abnormality detection unit 14, the control unit 15, the voltage detection unit 16, the temperature detection unit 17, the reception unit 18, and other processing units are constructed in a program format, the functions of each unit can be implemented by causing the arithmetic processing unit to operate in accordance with this program. A program for executing each process in the input current detection unit 12, the abnormality detection unit 14, the control unit 15, the voltage detection unit 16, the temperature detection unit 17, the reception unit 18, and other processing units may be provided in the form of a program product stored (recorded) on a computer-readable storage medium (recording medium) such as a semiconductor memory, a magnetic storage medium (magnetic recording medium), or an optical storage medium (optical recording medium). Alternatively, the input current detection unit 12, the abnormality detection unit 14, the control unit 15, the voltage detection unit 16, the temperature detection unit 17, the reception unit 18, and other processing units may be implemented as a semiconductor integrated circuit in which a program that implements the functions of each unit is written.
[0068] Each of the motor control device 8 and the higher-level control device 9 is provided with at least one processor, which is an arithmetic processing unit. Examples of arithmetic processing units include ICs, LSIs, CPUs, MPUs, and DSPs. By operating the arithmetic processing unit according to a predetermined program, the respective functions of the motor control device 8 and the higher-level control device 9 can be realized. The programs for executing each process in the motor control device 8 and the higher-level control device 9 may be provided in the form of program products stored (recorded) on a computer-readable storage medium (recording medium), such as a semiconductor memory, a magnetic storage medium (magnetic recording medium), or an optical storage medium (optical recording medium). Alternatively, the motor control device 8 and the higher-level control device 9 may be realized as semiconductor integrated circuits on which the programs that realize their respective functions are written.
[0069] Furthermore, the protection device 1 is provided with at least one memory, which is a storage device (recording device). The storage unit 13 is configured within this memory. The memory also includes the input current detection unit 12, the abnormality detection unit 14, the control unit 15, the voltage detection unit 16, the temperature detection unit 17, the receiving unit 18, and various other storage units (recording units) within the processing unit. Examples of the memory include electrically erasable and recordable non-volatile memory such as EEPROM (registered trademark), or high-speed read / write random access memory such as DRAM or SRAM. The storage device may also have a configuration such as an HDD (hard disk drive) or SSD (solid state drive). The memory stores programs for operating the input current detection unit 12, the abnormality detection unit 14, the control unit 15, the voltage detection unit 16, the temperature detection unit 17, the receiving unit 18, and the other processing units. The memory also stores the detection results from the input current detection unit 12. The memory storage unit 13 stores a table that associates the content (type) of an anomaly with the degree of urgency of that anomaly. The memory stores the detection results from the anomaly detection unit 14. The memory stores the detection results from the voltage detection unit 16. The memory stores the detection results from the temperature detection unit 17. The memory temporarily stores the alarm signals received by the receiving unit 18. The memory stores the "predetermined current range" used to determine the magnitude of the current detected by the input current detection unit 12. The memory stores the current threshold, voltage threshold, and temperature threshold. The memory stores the "predetermined voltage range" used to determine the magnitude of the voltage detected by the voltage detection unit 16. The memory stores the semiconductor switching elements S generated by the control unit 15. R S S , and S T The on / off command for this is temporarily stored.
[0070] Furthermore, each of the motor control device 8 and the higher-level control device 9 is provided with at least one memory, which is a storage device (recording device). The memory may be an electrically erasable and recordable non-volatile memory such as EEPROM (registered trademark), or a high-speed read / write random-access memory such as DRAM or SRAM. The storage device may also have a configuration such as an HDD (hard disk drive) or SSD (solid-state drive). The memory stores programs for operating the motor control device 8 and the higher-level control device 9. The memory temporarily stores drive commands for the semiconductor switching elements in the inverter 4 generated by the motor control device 8. The memory temporarily stores drive commands for the semiconductor switching elements in the converter 2. The memory stores various programs and data related to the converter 2. The memory stores various programs and data related to the inverter 4. The memory stores various programs and data related to the motor control device 8. The memory stores various programs and data related to the higher-level control device 9. The memory stores various programs and data related to the motor drive device 100.
[0071] <Advantages of Embodiments and Modifications of the Disclosure> According to embodiments and modifications thereof, in a protective device provided on the AC input side of a converter, the frequency of surges occurring when an abnormality is detected and the semiconductor switching element in the protective device is shut off can be reduced.
[0072] Conventionally, electromagnetic contactors have been used as a switch to selectively switch between conduction and interruption operations for the power line between the AC power source and the converter. When an abnormality occurs, an interruption command is immediately issued to the electromagnetic contactor, but the response time of the electromagnetic contactor is low (for example, it takes several tens of milliseconds to switch from open to closed operation), so the inverter excitation is turned off first, and by the time the electromagnetic contactor actually performs the interruption operation, no current is flowing through the electromagnetic contactor, so no surge occurs. On the other hand, when a highly responsive semiconductor switching element is used as a switch to selectively switch between conduction and interruption operations for the power line between the AC power source and the converter, if an abnormality occurs and an interruption command is issued immediately, there is a high possibility that the semiconductor switching element will perform the interruption operation while current is still flowing through it, which increases the frequency of surges. When surges occur, the burden on the surge protection element increases, and selecting a more durable surge protection element leads to an increase in the cost of the motor drive system. In contrast, according to the embodiments and modifications thereof of this disclosure, when an abnormality is detected that corresponds to a low degree of urgency for the tripping operation, the semiconductor switching elements of the three phases are sequentially tripped, starting with the phase in which the value of the current flowing from the three-phase AC power supply to the AC input side of the converter falls within a predetermined current range. As a result, the tripping operation is not performed while current is flowing through any of the three phases of semiconductor switching elements, so no surge occurs. On the other hand, when an abnormality is detected that corresponds to a high degree of urgency for the tripping operation, all three phases of semiconductor switching elements immediately trip from the time the abnormality is detected, prioritizing protection for the converter, thus ensuring a certain level of safety. According to the embodiments and modifications thereof of this disclosure, the content of the tripping operation of the semiconductor switching elements in the switch section changes depending on the degree of urgency for the tripping operation when an abnormality occurs, so that the frequency of surges associated with the tripping operation can be reduced while ensuring a certain level of safety. Therefore, the burden and deterioration of the surge protection element can be reduced, and the usability of surge protection elements with relatively low durability can be increased, thus suppressing the cost increase of the motor drive device.
[0073] Although the present disclosure has been described in detail above, it is not limited to the individual embodiments and modifications described above. These embodiments and modifications can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the present disclosure or from the spirit of the present disclosure derived from the claims and their equivalents. Furthermore, these embodiments and modifications can be implemented in combination. For example, the order of operations and processes in the embodiments and modifications described above are shown as examples only and are not limited thereto. The same applies when numerical values or mathematical formulas are used in the description of the embodiments and modifications described above.
[0074] <Note> The following additional information is disclosed regarding the above embodiments and modifications.
[0075] (Note 1) A protective device comprising: a switch unit having semiconductor switching elements provided in each phase of the three-phase power line between a three-phase AC power source and a converter, which independently perform conduction and interruption operations for each phase of the three-phase power line, and a diode connected in antiparallel to the semiconductor switching elements; an input current detection unit that detects the current of each phase flowing from the three-phase AC power source to the AC input side of the converter via the three-phase power line; a storage unit that stores a table that defines the relationship between the nature of an abnormality and the degree of urgency of the interruption operation to be performed when the abnormality occurs; an abnormality detection unit that detects abnormalities occurring in the system including the converter; and a control unit that controls the conduction and interruption operations of the semiconductor switching elements, wherein the control unit controls all three-phase semiconductor switching elements to perform an interruption operation immediately from the time of abnormality detection when an abnormality corresponding to a high degree of urgency in the table is detected, and controls the semiconductor switching elements of the three-phase semiconductor switching elements to perform an interruption operation sequentially starting from the phase in which the value of the current detected by the input current detection unit falls within a predetermined current range. (Note 2) The protection device as described in Note 1, wherein the control unit, when it detects an abnormality associated with low urgency in the table, repeatedly determines whether the value of the current detected by the input current detection unit has fallen within a predetermined current range until all three-phase semiconductor switching elements shut off. (Note 3) The protection device as described in Note 1, wherein the abnormality detection unit detects that an abnormality has occurred when the value of the current detected by the input current detection unit exceeds a predetermined current threshold. (Note 4) The protection device as described in Note 1, further comprising a receiving unit that receives alarm signals output from equipment related to the system, wherein the abnormality detection unit detects that an abnormality has occurred when the receiving unit receives an alarm signal. (Note 5) The protection device as described in any one of Notes 1 to 4, wherein the abnormality associated with high urgency includes at least one of the following: an overcurrent occurring in any phase of the three-phase power line, a short circuit in a smoothing capacitor electrically connected to the DC output side of the converter, and an abnormality indicated by an alarm signal output from equipment related to the system.(Note 6) A protective device according to any one of Notes 1 to 5, wherein an anomaly associated with a low degree of urgency includes at least one of the following: an overvoltage occurring in any circuit within the system, an anomaly in the converter, an anomaly in an inverter electrically connected to the DC output side of the converter, an anomaly in a motor driven by AC power output from the inverter, an overheating occurring in equipment related to the system, and an anomaly indicated by an alarm signal output from equipment related to the system. (Note 7) A converter incorporating a protective device according to any one of Notes 1 to 6.
[0076] 1. Protection device 2. Converter 3. 3P, 3N. Smoothing capacitor 4. Inverter 5. Three-phase AC power supply 6. Motor 7. DC link 8. Motor control device 9. Higher-level control device 11. Switch unit 12. Input current detection unit 13. Memory unit 14. Anomaly detection unit 15. Control unit 16. Voltage detection unit 17. Temperature detection unit 18. Receiving unit 21. DC link voltage detection circuit 22. Voltage detection resistor 23. First voltage divider resistor 24. Second voltage divider resistor 25. First Zener diode 26. Second Zener diode 51R. R-phase power line 51S. S-phase power line 51T. T-phase power line 52P. Positive power line 52N. Negative power line 61. Encoder 100. Motor drive device D R , D S , D T Diode S R S S S T Semiconductor switching element T1, T2 connection point
Claims
1. A protective device comprising: a switch unit having semiconductor switching elements provided in each phase of a three-phase power line between a three-phase AC power source and a converter, which independently perform conduction and interruption operations for each phase of the three-phase power line, and a diode connected in antiparallel to the semiconductor switching elements; an input current detection unit that detects the current of each phase flowing from the three-phase AC power source to the AC input side of the converter via the three-phase power line; a storage unit that stores a table that defines the relationship between the nature of an abnormality and the degree of urgency of the interruption operation to be performed when the abnormality occurs; an abnormality detection unit that detects abnormalities occurring in the system including the converter; and a control unit that controls the conduction and interruption operations of the semiconductor switching elements, wherein the control unit controls all three-phase semiconductor switching elements to immediately perform an interruption operation from the time of abnormality detection when an abnormality corresponding to a high degree of urgency in the table is detected, and controls the semiconductor switching elements of the three phases to sequentially perform an interruption operation starting with the semiconductor switching elements of the phase in which the value of the current detected by the input current detection unit falls within a predetermined current range.
2. The protection device according to claim 1, wherein, when the control unit detects an abnormality associated with a low degree of urgency in the table, it repeatedly performs a determination of whether the value of the current detected by the input current detection unit has fallen within a predetermined current range until all three phase semiconductor switching elements shut off.
3. The protection device according to claim 1, wherein the abnormality detection unit detects that an abnormality has occurred when the value of the current detected by the input current detection unit exceeds a predetermined current threshold.
4. The protective device according to claim 1, further comprising a receiving unit that receives an alarm signal output from equipment related to the system, wherein the abnormality detection unit detects that an abnormality has occurred when the receiving unit receives the alarm signal.
5. The protective device according to any one of claims 1 to 4, wherein the abnormality associated with a high degree of urgency includes at least one of an overcurrent occurring in any phase of the three-phase power line, a short circuit in a smoothing capacitor electrically connected to the DC output side of the converter, and an abnormality indicated by an alarm signal output from equipment related to the system.
6. The protective device according to any one of claims 1 to 5, wherein the abnormality associated with low urgency includes at least one of the following: an overvoltage occurring in any circuit within the system, an abnormality in the converter, an abnormality in an inverter electrically connected to the DC output side of the converter, an abnormality in a motor driven by AC power output from the inverter, an overheating occurring in equipment related to the system, and an abnormality indicated by an alarm signal output from equipment related to the system.
7. A converter incorporating the protective device described in any one of claims 1 to 6.