Gas compressor

Abstract

The present invention provides a gas compressor that uses a plurality of drive circuits to drive a single electric motor, and can continue operation when a drive circuit has failed. A gas compressor (1) according to the present invention comprises: an electric motor (13) that operates in accordance with an operation parameter and drives a compressor body (4) for generating a compressed gas; a plurality of drive circuits (12a, 12b) that supply a drive current to the electric motor (13) as output; and a compressor control device (7) that can detect an abnormality in the drive circuits (12a, 12b). When an abnormality is detected in a drive circuit (12b), and the total output that can be supplied to the electric motor (13) by a normal drive circuit (12a) in which no abnormality has occurred is greater than or equal to the total output supplied to the electric motor (13) by the drive circuits (12a, 12b) at a point in time immediately before the abnormality was detected in the drive circuit (12b), the compressor control device (7) updates the operation parameter to a parameter for emergency operation.

Description

Gas compressor

[0001] The present invention relates to a gas compressor, and more particularly to a gas compressor in which an electric motor is driven by a plurality of drive circuits.

[0002] A gas compressor is a compressor driven by an electric motor that generates compressed gas. The compressed gas generated by a gas compressor is generally used to power equipment installed in facilities such as factories, or is used directly for work. When a gas compressor malfunctions, downtime occurs during which the compressor cannot be used while the condition of the equipment is investigated, parts necessary for repairs are obtained, and repair work is carried out. For this reason, when operating a gas compressor, maintenance inspections are carried out from the perspective of preventive maintenance against accidental malfunctions and deterioration of parts over time, and the installation of spare machines or alternative equipment is recommended, especially in important facilities.

[0003] Even with maintenance and inspection, it is difficult to prevent accidental breakdowns in gas compressors, which may result in the shutdown of the gas compressor or the shutdown of equipment or work that uses the compressed gas generated by the gas compressor. On the other hand, there are issues in that the installation of backup or alternative equipment is expensive and requires space for such equipment.

[0004] A gas compressor includes an electric motor and a drive circuit (power conversion device) that drives the electric motor. Generally, gas compressors are configured with multiple drive circuits that supply power to multiple electric motors, respectively, and with multiple drive circuits that supply power to a single electric motor. In gas compressors with the latter configuration, for example, the armature of the electric motor includes multiple windings or multiple sets of windings, and the drive circuit supplies power to each winding.

[0005] Patent Document 1 describes an example of a rotating electric machine that includes a motor having multiple winding sets (three windings for U phase, V phase, and W phase) and multiple power conversion devices (inverters) that supply drive current to each of these winding sets. By including two inverters, the rotating electric machine described in Patent Document 1 can continue to operate at half output using the other inverter even if one inverter fails, reducing the possibility that a failure in the rotating electric machine will affect other devices.

[0006] Japanese Patent Application Laid-Open No. 2017-121179

[0007] As described above, in conventional gas compressors, if an abnormality occurs in a drive circuit, such as an inverter, that drives the electric motor, downtime during which the gas compressor cannot be used may occur. Therefore, to reduce such downtime, a gas compressor that can continue operation without stopping even if an abnormality occurs in the drive circuit is desired. In particular, for gas compressors that have a configuration in which multiple drive circuits supply power to a single electric motor (i.e., a configuration in which one electric motor is driven by multiple drive circuits), it is desired that the compressor be able to continue operation efficiently even if an abnormality occurs in the drive circuit.

[0008] An object of the present invention is to provide a gas compressor in which one electric motor is driven by a plurality of drive circuits, and which can continue to operate even when a drive circuit fails.

[0009] A gas compressor according to the present invention includes a compressor main body that generates compressed gas and operates according to operating parameters, the gas compressor including an electric motor that drives the compressor main body, a plurality of drive circuits that supply drive current as an output to the electric motor, and a compressor control device including a memory device and capable of detecting an abnormality in the drive circuits. When an abnormality occurs in the drive circuits, the gas compressor switches to emergency operation, and the operating parameters for operating the gas compressor using only normal drive circuits, that is, drive circuits that are not abnormal among the plurality of drive circuits, are set as emergency operation parameters. The compressor control device is configured to update the operating parameters to the emergency operation parameters when it detects an abnormality in the drive circuits and if the total output that the normal drive circuits can supply to the motor is equal to or greater than the total output that the drive circuits were supplying to the motor immediately before the abnormality in the drive circuits was detected.

[0010] According to the present invention, it is possible to provide a gas compressor in which one electric motor is driven by a plurality of drive circuits, and which can continue to operate even when a drive circuit fails.

[0011] FIG. 1 is a diagram showing a schematic configuration of a gas compressor according to a first embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a compressor control device. FIG. 3 is a diagram showing a schematic configuration of a compressor display operation unit. FIG. 4 is a diagram showing a schematic configuration of an inverter control circuit. FIG. 5 is a diagram showing a schematic configuration of an inverter drive circuit. FIG. 6 is a flowchart showing an example of a process for switching to emergency operation when the gas compressor according to the first embodiment is in operation. FIG. 7 is a flowchart showing a process for switching to emergency operation when the gas compressor according to the first embodiment has stopped operation. FIG. 8 is a time chart showing an example of changes in the state of the gas compressor before and after switching to emergency operation in the first embodiment. FIG. 9 is a time chart showing an example of changes in the total and each output of the inverter drive circuit over time when switching to emergency operation in the first embodiment, the time chart showing a case where a retry process is not executed. FIG. 10 is a time chart showing an example of changes in the total and each output of the inverter drive circuit over time when switching to emergency operation in the first embodiment, the time chart showing a case where a retry process is executed. FIG. 11 is a diagram showing a schematic configuration of a gas compressor according to a second embodiment of the present invention. FIG. 12 is a diagram showing the relationship between the pressure loss ΔP from the pressure detection position to the end of the piping and the amount of gas used Q in the second embodiment. 1 is a flowchart showing an example of a process for executing increased air volume control of a gas compressor in a process for switching the gas compressor to emergency operation according to embodiment 2. FIG. 2 is a diagram showing the relationship between the target value of the discharge pressure of the gas compressor and the amount of gas used, and is a diagram showing a straight line β at which the output of the inverter drive circuit is constant, and curves α1 and α2 which represent the relationship between the target pressure P and the amount of gas used Q. FIG. 3 is a time chart showing an example of changes in the state of the gas compressor before and after switching to emergency operation when increased air volume control is executed in embodiment 2.

[0012] The gas compressor according to the present invention includes an electric motor that drives the compressor body that generates compressed gas, and a plurality of drive circuits (inverter drive circuits) that drive the electric motor, and operates according to operating parameters.

[0013] In this specification, the term "emergency operation" refers to the temporary operation of a gas compressor when an abnormality occurs in the drive circuit of the electric motor. Emergency operation refers to operation in which the operating parameters of the gas compressor are updated to parameters for operation performed by the gas compressor using a normal, non-faulty drive circuit, and the gas compressor is operated according to the updated operating parameters (parameters for emergency operation). The period of emergency operation may last for several days.

[0014] The gas compressor according to the present invention can continue to operate by performing emergency operation even if at least one drive circuit fails.

[0015] A gas compressor according to an embodiment of the present invention will be described below with reference to the drawings. In the drawings used in this specification, the same or corresponding components are designated by the same reference numerals, and repeated description of these components may be omitted. In the following description, an interface may be abbreviated as "I / F."

[0016] In the following embodiments, a gas compressor including one inverter control circuit and two inverter drive circuits will be described as an example, but the present invention can also be applied to gas compressors including multiple inverter control circuits or three or more inverter drive circuits.

[0017] A gas compressor according to a first embodiment of the present invention will be described. The gas compressor according to this embodiment compresses gas to generate compressed gas.

[0018] Fig. 1 is a diagram showing the schematic configuration of a gas compressor according to this embodiment. In Fig. 1, thin solid lines and thin solid arrows represent the flow of gas (including compressed gas), thin dashed lines represent control signals related to the gas compressor, and thick solid lines represent power wiring for a drive unit of the gas compressor.

[0019] The gas compressor 1 includes, as its main components, a compressor main body 4, an electric motor 13, a pressure sensor 6, a compressor control device 7, an inverter control circuit 11, multiple inverter drive circuits 12a, 12b, opening and closing devices 14a, 14b, 15a, 15b, a compressor display operation unit 10, and a power terminal block 16.

[0020] The gas compressor 1 draws in gas through an intake filter 2 and an intake throttle valve 3, and compresses the drawn gas to a predetermined pressure by a compressor body 4.

[0021] The compressor body 4 is driven by an electric motor 13 to generate compressed gas. The compressed gas passes through a check valve 5 and an aftercooler and a dryer (not shown), and is then discharged to the outside from a compressed gas outlet 9.

[0022] The electric motor 13 is driven by a plurality of drive circuits to drive the compressor main body 4. In this embodiment, as an example, the electric motor 13 is driven by being supplied with drive current from two inverter drive circuits 12a and 12b. That is, in the gas compressor 1 according to this embodiment, the electric motor 13 is driven by two drive circuits supplying power to one electric motor 13. Specifically, the electric motor 13 has two sets of stator windings, and the inverter drive circuit 12a supplies a drive current to one set of stator windings, and the inverter drive circuit 12b supplies a drive current to the other set of stator windings.

[0023] The pressure sensor 6 detects the pressure of the compressed gas discharged to the outside, and outputs the detected pressure to the compressor control device 7 as a detection signal.

[0024] The compressor control device 7 receives signals output from the pressure sensor 6, the inverter control circuit 11, and the compressor display / operation unit 10, and controls the operation of the gas compressor 1 based on the received signals. For example, the compressor control device 7 controls the start and stop of the operation of the gas compressor 1 and controls the change in the rotation speed of the electric motor 13 (variable control of the rotation speed). The compressor control device 7 can also change the amount of gas flowing in from the suction throttle valve 3 by controlling the opening and closing of the solenoid valve 8.

[0025] The inverter control circuit 11 controls the inverter drive circuits 12a and 12b.

[0026] The inverter drive circuits 12a and 12b are drive circuits that supply drive current to the electric motor 13 to drive the electric motor 13. The inverter drive circuits 12a and 12b are configured with inverters. In this embodiment, the two inverter drive circuits 12a and 12b are assumed to have the same output (drive current) that can be supplied to the electric motor 13.

[0027] The compressor control device 7 variably controls the rotation speed of the electric motor 13 by comparing the value of the detection signal input from the pressure sensor 6 with the value of the target pressure set in the gas compressor 1 and outputting a command to the inverter control circuit 11 so that the value of the detection signal becomes the target pressure. In accordance with the command from the compressor control device 7, the inverter control circuit 11 controls the frequency of the drive current supplied to the electric motor 13 by the inverter drive circuits 12a, 12b. In this way, the compressor control device 7 variably controls the rotation speed of the electric motor 13.

[0028] The switching devices 14a and 14b are arranged on the primary side (input side) and secondary side (output side) of the inverter drive circuit 12a, respectively. The switching devices 15a and 15b are arranged on the primary side (input side) and secondary side (output side) of the inverter drive circuit 12b, respectively. The switching devices 14a, 14b, 15a, and 15b are controlled to open and close by the compressor control device 7. The switching devices 14a, 14b, 15a, and 15b may notify the compressor control device 7 of the results of their opening and closing operations.

[0029] The compressor display operation unit 10 displays data and information output by the compressor control device 7, inputs operation instructions from the user of the gas compressor 1 to the gas compressor 1, and outputs these operation instructions to the compressor control device 7.

[0030] The power supply terminal block 16 is connected to a power supply external to the gas compressor 1 and receives power from the power supply. This power is supplied to the electric motor 13.

[0031] 2 is a diagram showing a schematic configuration of the compressor control device 7. The compressor control device 7 includes a control unit 17, a storage device 19, a memory 18, an input / output I / F 20, and a communication I / F 21.

[0032] The control unit 17 performs processes such as controlling the operation of the gas compressor 1. The control unit 17 also controls emergency operation of the gas compressor 1.

[0033] Storage device 19 stores software, setting values, and the like for operating gas compressor 1. For example, storage device 19 stores programs for control unit 17 to execute processes, and setting values, parameters, data, and the like required for control unit 17 to execute processes. For example, storage device 19 stores, as operating parameters for gas compressor 1, an upper limit value of the output frequency of electric motor 13 and a target pressure of the compressed gas supplied by gas compressor 1. The upper limit value of the output frequency of electric motor 13 can be considered to represent the amount of gas discharged from gas compressor 1.

[0034] The memory 18 temporarily stores programs for the control unit 17 to execute processes, as well as setting values, parameters, data, etc. required for the control unit 17 to execute processes. The memory 18 can read these programs, setting values, parameters, data, etc. from the storage device 19, for example, and store them therein.

[0035] The input / output I / F 20 is an interface for inputting operations to the control unit 17 and outputting instructions and processing results of the control unit 17 .

[0036] The communication I / F 21 is an interface for connecting the compressor control device 7 and the inverter control circuit 11 so that they can communicate with each other.

[0037] The compressor control device 7 controls the rotation speed of the electric motor 13 by the control unit 17 controlling the inverter drive circuits 12 a and 12 b via the inverter control circuit 11 .

[0038] 3 is a diagram showing a schematic configuration of the compressor display operation unit 10. The compressor display operation unit 10 includes a display unit 22 and an input / output I / F 23.

[0039] The display unit 22 displays the processing results and data output by the control unit 17 of the compressor control device 7, as well as the setting values, parameters, data, etc. stored in the memory 18 and storage device 19 provided in the compressor control device 7.

[0040] The input / output I / F 23 is an interface that allows a user of the gas compressor 1 to input operating instructions to the gas compressor 1 and displays data and information output by the compressor control device 7 to the user.

[0041] 4 is a diagram showing a schematic configuration of the inverter control circuit 11. The inverter control circuit 11 includes a control unit 24 and a communication I / F 25.

[0042] The control unit 24 controls the multiple inverter drive circuits 12a, 12b in accordance with instructions from the compressor control device 7, and can also grasp the status (e.g., whether or not there is an abnormality) of each of the multiple inverter drive circuits 12a, 12b.

[0043] The communication I / F 25 is an interface for connecting the inverter control circuit 11 and the compressor control device 7 so that they can communicate with each other.

[0044] 5 is a diagram showing a schematic configuration of the inverter drive circuits 12a and 12b. Each of the inverter drive circuits 12a and 12b includes a diode 26, a capacitor 27, a power switching element 28 (e.g., an IGBT), and the like.

[0045] Error information is defined for each abnormality in the components of the gas compressor 1. By referring to the definition of the error information, it is possible to understand what kind of error the error information indicates. The storage device 19 included in the compressor control device 7 stores this error information definition (the correspondence between the error information and the abnormality in each component of the gas compressor 1).

[0046] In this specification, abnormalities caused by failures in components constituting the inverter drive circuits 12 a, 12 b and abnormalities that are presumed to be caused by failures in these components are collectively referred to as “drive circuit system abnormalities.” Drive circuit system abnormalities are abnormalities in the inverter drive circuits 12 a, 12 b.

[0047] The compressor control device 7 can detect that a drive circuit system abnormality has occurred in at least one of the plurality of inverter drive circuits 12 a, 12 b. The compressor control device 7 detects that a drive circuit system abnormality has occurred in the inverter drive circuits 12 a, 12 b, for example, in the following manner.

[0048] The compressor control device 7 determines whether a drive circuit system abnormality has occurred for each of the multiple inverter drive circuits 12 a, 12 b. For example, when the inverter control circuit 11 detects an abnormality in the power switching element 28 included in the inverter drive circuit 12 b, it transmits error information corresponding to the abnormality and detection information that the error information has been detected by the inverter drive circuit 12 b to the compressor control device 7 via the communication I / F 25. The compressor control device 7 refers to the error information definition stored in the storage device 19, and if the received error information is error information indicating a drive circuit system abnormality, it determines that a drive circuit system abnormality has occurred.

[0049] The compressor control device 7 associates this determination result with the inverter drive circuit 12b in which the abnormality was detected, so that it is possible to know that an abnormality has occurred in the drive circuit system of the inverter drive circuit 12b.

[0050] 6 and 7, a process will be described in which the gas compressor 1 according to this embodiment switches from normal operation, in which no drive circuit abnormality has occurred, to emergency operation when a drive circuit abnormality (abnormality in the inverter drive circuits 12a, 12b) has occurred.

[0051] As described above, emergency operation is an operation that the gas compressor 1 temporarily performs when the inverter drive circuits 12a, 12b of the electric motor 13 fail. During emergency operation, the operating parameters of the gas compressor 1 are updated to parameters (emergency operation parameters) for operation using an inverter drive circuit that is not experiencing a drive circuit abnormality, and the gas compressor 1 is operated in accordance with the updated operating parameters. As described above, the operating parameters include the upper limit of the output frequency of the electric motor 13 (the amount of gas discharged from the gas compressor 1) and the target pressure of the compressed gas supplied by the gas compressor 1.

[0052] 6 is a flowchart showing an example of a process for switching the gas compressor 1 according to this embodiment from an operating state to an emergency operation state. The gas compressor 1 starts operation when a command to start operation is input by the user from the compressor display operation unit 10.

[0053] In step S10, the control unit 17 of the compressor control device 7 updates the state of the emergency operation flag stored in the memory 18 to match the state of the emergency operation flag in the storage device 19. The emergency operation flag is a flag that indicates whether the gas compressor 1 will perform emergency operation. If the emergency operation flag is on, the gas compressor 1 performs emergency operation. The storage device 19 stores the state of the emergency operation flag. If the updated emergency operation flag is on, the process of step S20 is executed, and if it is off, the process of step S30 is executed.

[0054] Step S20 is a process for carrying out emergency operation.

[0055] In step S20, the control unit 17 of the compressor control device 7 references information stored in the storage device 19 about the inverter drive circuit in which the drive circuit abnormality has occurred (information indicating which inverter drive circuit has the drive circuit abnormality), and identifies the inverter drive circuit in which the drive circuit abnormality has occurred. In step S80, which will be described later, the storage device 19 stores information about the inverter drive circuit in which the drive circuit abnormality has occurred. In this embodiment, the inverter drive circuit in which the drive circuit abnormality has occurred is inverter drive circuit 12b.

[0056] Hereinafter, an inverter drive circuit that is not experiencing a drive circuit system abnormality will be referred to as a “normal drive circuit.” In this embodiment, the normal drive circuit is inverter drive circuit 12a.

[0057] The compressor control device 7 then sends a command to the switching devices 15a, 15b, which are arranged on the primary and secondary sides of the inverter drive circuit 12b that has experienced the drive circuit system abnormality, to open the switching devices 15a, 15b and open the circuit. Upon receiving this command, the switching devices 15a, 15b open and open the circuit. For safety reasons, it is desirable for the switching devices 15a, 15b to feed back the results of this operation to the compressor control device 7. When the switching devices 15a, 15b open, the inverter drive circuit 12b that has experienced the drive circuit system abnormality is separated from the circuit and does not supply output to the electric motor 13.

[0058] Next, the compressor control device 7 refers to the storage device 19 and determines the total output of the normal drive circuits (in this embodiment, the output of the inverter drive circuit 12a). The storage device 19 stores the output values ​​of each of the multiple inverter drive circuits 12a, 12b. The total output of the normal drive circuits is the output (drive current) that the normal drive circuits can supply to the motor 13. In other words, the compressor control device 7 determines the output (drive current) that the multiple inverter drive circuits can supply to the motor 13 in a state in which a drive circuit system abnormality has occurred in the inverter drive circuit.

[0059] Based on the obtained results, the compressor control device 7 updates the operating parameters of the gas compressor 1 stored in the memory 18 to operating parameters (parameters for emergency operation) corresponding to operation at the output that the normal drive circuit can supply. The parameters for emergency operation are operating parameters for operating the gas compressor 1 using only the normal drive circuit among the multiple inverter drive circuits. For example, the compressor control device 7 updates the upper limit of the output frequency of the motor 13 (the amount of gas discharged from the gas compressor 1) as an operating parameter. For example, the compressor control device 7 multiplies the upper limit of the output frequency in a normal state in which the inverter drive circuits 12a and 12b are not experiencing any drive circuit system abnormalities by the ratio of the output of the normal drive circuit (inverter drive circuit 12a) to the total output of the inverter drive circuits 12a and 12b to obtain a new upper limit of the output frequency and update the operating parameters.

[0060] In this embodiment, one of the two inverter drive circuits 12a, 12b, the inverter drive circuit 12b, is experiencing a drive circuit system abnormality, so the total output that the normal drive circuits can supply to the motor 13 is the output of the inverter drive circuit 12a, which is 50% of the output in the normal state. Therefore, the control unit 17 updates the values ​​of the operating parameters stored in the memory 18 (for example, parameters representing the upper limit of the output frequency of the motor 13 (the amount of gas discharged from the gas compressor 1)) so as to limit the upper limit of the rotation speed of the motor 13 to 50% of the normal state. The operating parameters updated in this way are the parameters for emergency operation.

[0061] Furthermore, the control unit 17 may update the operating parameters stored in the memory 18 using the operating parameters stored in the storage device 19. For example, if the storage device 19 stores operating parameters set according to the number of normal drive circuits or a table summarizing parameters for emergency operation, the control unit 17 may update the operating parameters using these parameters.

[0062] Step S30 indicates that the gas compressor 1 is in operation. After step S20 is executed, the gas compressor 1 performs emergency operation in accordance with the parameters for emergency operation. If step S20 is not executed, the gas compressor 1 does not perform emergency operation, but performs normal operation when no abnormality in the drive circuit system has occurred. The compressor control device 7 may obtain an inverter error from the inverter control circuit 11 via the communication I / F 21 while the gas compressor 1 is operating.

[0063] In step S40, the control unit 17 of the compressor control device 7 determines whether or not an inverter error has been acquired from the inverter control circuit 11. If the control unit 17 has acquired an inverter error from the inverter control circuit 11, the error information stored in the memory 18 is updated to indicate the presence of an error, and the process of step S50 is executed. If the control unit 17 has not acquired an inverter error, the process of step S30 continues, and the operating state of the gas compressor 1 is maintained.

[0064] In step S50, if the inverter error acquired by the control unit 17 in step 40 is an error indicating a drive circuit system abnormality, the process of step S60 is executed, and if the error is not an error indicating a drive circuit system abnormality, the process of step S100 is executed. The storage device 19 stores information for determining whether the inverter error acquired by the control unit 17 is an error indicating a drive circuit system abnormality.

[0065] In step S60, the control unit 17 determines whether the emergency operation is enabled. The user of the gas compressor 1 sets in advance whether the emergency operation of the gas compressor 1 is enabled or disabled. The storage device 19 stores in advance the setting as to whether the emergency operation is enabled or disabled. The control unit 17 can determine whether the emergency operation is enabled or disabled by referring to the storage device 19. If the emergency operation is enabled, the process of step S70 is executed, and if the emergency operation is disabled, the process of step S120 is executed.

[0066] If the user has not set in advance whether to enable or disable the emergency operation of the gas compressor 1, the process of step S70 is executed.

[0067] In step S70, control unit 17 refers to storage device 19 and compares the total output that the normal drive circuit can supply to motor 13 (in this embodiment, the output that inverter drive circuit 12a can supply) with the minimum output of the inverter drive circuit required to operate gas compressor 1. Storage device 19 stores the value of the output that inverter drive circuit 12a can supply and the minimum output value of the inverter drive circuit required to operate gas compressor 1. If the total output that the normal drive circuit can supply is equal to or greater than the minimum output required to operate gas compressor 1, the process of step S80 is executed; if not, the process of step S120 is executed.

[0068] In step S80, the control unit 17 of the compressor control device 7 updates the state of the emergency operation flag stored in the storage device 19 to ON. If the state of the emergency operation flag is OFF, the control unit 17 changes it to ON, and if the state of the emergency operation flag is ON, the control unit 17 leaves it ON.

[0069] The process of step S10 (the process of updating the state of the emergency operation flag stored in the memory 18) may be executed after the process of step S80 has been executed.

[0070] In step S80, the control unit 17 then stores information about the inverter drive circuit in which the drive circuit abnormality has occurred in the storage device 19. In this embodiment, the control unit 17 stores in the storage device 19 information that the drive circuit abnormality has occurred in the inverter drive circuit 12b.

[0071] In step S90, the control unit 17 compares the total output power Xn that the normal drive circuit can supply to the motor 13 with the total output power Xc that the inverter drive circuit is currently supplying to the motor 13. If the total output power Xn that can be supplied is equal to or greater than the current total output power Xc, the process of step S10 is executed; otherwise, the process of step S110 is executed. The output power of the inverter drive circuit can be obtained from the storage device 19, as already described. The current total output power that the inverter drive circuit is supplying to the motor 13 can be obtained from the memory 18.

[0072] The present time refers to the time immediately before the time when the decision to switch to emergency operation was made. In this embodiment, the present time refers to the time immediately before the control unit 17 of the compressor control device 7 detected that a drive circuit abnormality occurred in the inverter drive circuit 12b.

[0073] In this embodiment, the control unit 17 compares the ratio Rn (=Xn / Xall) of the total output Xn that can be supplied by the normal drive circuits to the total output Xall that can be supplied by all the inverter drive circuits with the ratio Rc (=Xc / Xall) of the total output Xall to the current total output Xc that the inverter drive circuits are supplying to the motor 13. In this embodiment, the total output Xall is the sum of the output that can be supplied by the inverter drive circuit 12a and the output that can be supplied by the inverter drive circuit 12b, the total output Xn is the output that can be supplied by the inverter drive circuit 12a, and the current total output Xc is the sum of the output that the inverter drive circuits 12a and 12b are currently supplying to the motor 13.

[0074] In this embodiment, if the processing of step S90 determines that the ratio Rn (=Xn / Xall) is equal to or greater than the ratio Rc (=Xc / Xall), the processing of step S10 is executed; otherwise, the processing of step S110 is executed.

[0075] When the processing of step S10 is executed after step S90, the emergency operation flag is in the ON state, so the processing of step S20 is executed and the emergency operation of the gas compressor 1 is performed.

[0076] In step S100, the control unit 17 determines whether the inverter error acquired in step 40 is a retryable error. If the inverter error is a retryable error and the value of the retry counter is smaller than a predetermined specified value, the process of step S110 is executed; otherwise, the process of step S120 is executed. The storage device 19 stores information indicating which inverter errors are retryable, the value of the retry counter, and the specified value for the retry counter value. The control unit 17 references the storage device 19 and executes the determination process of step S100.

[0077] In step S110, the control unit 17 of the compressor control device 7 executes a retry process. The control unit 17 automatically sends to the inverter control circuit 11 a command to stop operation of the gas compressor 1 and a command to reset the error that is being reported. The control unit 17 then increments the value of the retry counter stored in the storage device 19 by 1 and waits for the restart wait time previously stored in the storage device 19 to elapse. After the restart wait time has elapsed, the control unit 17 sends a command to the inverter control circuit 11 to start operation of the gas compressor 1, and executes the process of step S10. That is, the gas compressor 1 waits while stopped for the restart wait time, and then resumes operation of the gas compressor 1.

[0078] In step S120, the control unit 17 of the compressor control device 7 sends a command to the inverter control circuit 11 via the communication I / F 21 to stop the gas compressor 1 due to the occurrence of an abnormality in the drive circuit system.

[0079] 7 is a flowchart showing a process for switching the gas compressor 1 according to this embodiment to emergency operation when the gas compressor 1 has stopped operating. Note that in FIG. 7, a description of steps that execute the same processes as the steps described in FIG. 6 will be omitted.

[0080] Step S130 indicates that the gas compressor 1 is in a stopped state.

[0081] In steps S40, S50, S60, S70, S80, and S120, the same processing as that described with reference to FIG. 6 is executed.

[0082] If the control unit 17 does not obtain an inverter error in step S40, the process proceeds to step S140.

[0083] In step S50, if the inverter error acquired by the control unit 17 in step S40 is not an error indicating a drive circuit system abnormality, the process proceeds to step S120.

[0084] In step S120, when the control unit 17 of the compressor control device 7 sends a command to the inverter control circuit 11 to abnormally stop the gas compressor 1, step S150 is executed.

[0085] In step S150, the control unit 17 of the compressor control device 7 determines whether or not an error reset has been input. The user of the gas compressor 1 can input an error reset by pressing the reset button provided on the compressor display operation unit 10. When the control unit 17 detects that an error reset has been input, it updates the error information stored in the memory 18 to indicate that there is no error, and then executes the process of S40.

[0086] In step S140, the control unit 17 of the compressor control device 7 determines whether or not a command to start operation of the gas compressor 1 has been input. A user of the gas compressor 1 can input the command to start operation using the compressor display / operation unit 10. If the control unit 17 detects that the command to start operation has been input, the gas compressor 1 starts operation and executes the processing of the flowchart shown in Fig. 6. If the control unit 17 does not detect that the command to start operation has been input, the processing of step S40 is executed.

[0087] Fig. 8 is a time chart showing an example of changes in the state of the gas compressor 1 before and after switching to emergency operation in this embodiment. Fig. 8 shows, as an example, a time chart in which the operation of the gas compressor 1 is switched to emergency operation when a drive circuit abnormality occurs in the inverter drive circuit 12b of the two inverter drive circuits 12a and 12b that supply drive current to the electric motor 13 of the operating gas compressor 1. Fig. 8 shows, as an example, examples of changes over time in the presence or absence of a drive circuit abnormality in the inverter drive circuits 12a and 12b, the state of the emergency operation flag, the upper limit values ​​of the total and individual outputs of the inverter drive circuits 12a and 12b, the target pressure of the compressed gas supplied by the gas compressor 1, and the upper limit value of the output frequency of the electric motor 13 (the amount of gas discharged from the gas compressor 1) output by the compressor control device 7 to the inverter control circuit 11.

[0088] The target pressure of the compressed gas and the upper limit of the output frequency of the electric motor 13 are operating parameters of the gas compressor 1. In this embodiment, the target pressure value of the compressed gas supplied by the gas compressor 1 at the compressed gas outlet 9 is set to 0.70 MPa as shown in "Target Pressure" in Fig. 8, and is not changed before or after switching to emergency operation.

[0089] In Fig. 8, time block A corresponds to the state in step S30 of the flowchart shown in Fig. 6, and is a time period indicating that the gas compressor 1 is in a normal operating state (not in emergency operation) in which no abnormality has occurred in the drive circuit system. Time point B is the time point at which the gas compressor 1 switches from normal operation to emergency operation. Time block C, like time block A, corresponds to the state in step S30 of the flowchart shown in Fig. 6, but is a time period indicating that the gas compressor 1 is in emergency operation.

[0090] As mentioned above, the present refers to the point immediately before the decision to switch to emergency operation was made, that is, the point immediately before point B shown in Figure 8 (the last point of time block A).

[0091] At time B, the inverter control circuit 11 transmits information to the compressor control device 7 that a drive circuit system abnormality has occurred in the inverter drive circuit 12b. Upon receiving this information, the compressor control device 7 executes steps S40 to S80 shown in FIG. 6 and updates the state of the emergency operation flag stored in the storage device 19 from OFF to ON. At this time, the output that can be supplied to the electric motor 13 from the inverter drive circuits 12a and 12b is 100% of the upper limit for the inverter drive circuit 12a, and is 0% for the inverter drive circuit 12b in which the drive circuit system abnormality has occurred. Therefore, the total output that can be supplied to the electric motor 13 from the two inverter drive circuits 12a and 12b has decreased to 50% of the total output in time block A.

[0092] When the state of the emergency operation flag is switched from off to on, the compressor control device 7 determines the output that the normal drive circuit can supply to the motor 13 (i.e., the output of the inverter drive circuit 12a) according to the processes of steps S10 and S20 shown in FIG. 6. Then, during emergency operation, the compressor control device 7 updates the operating parameters of the gas compressor 1 if the minimum output of the inverter drive circuit required to operate the gas compressor 1 does not exceed the total output that the normal drive circuit can supply to the motor 13 (in this embodiment, the output that the inverter drive circuit 12a can supply). In this embodiment, the compressor control device 7 reduces the upper limit of the output frequency, which is an operating parameter, from 100% before switching to emergency operation to 50% so that the gas compressor 1 operates at the output that the normal drive circuit (inverter drive circuit 12a) can supply.

[0093] In time block C, the gas compressor 1 is performing emergency operation. That is, the gas compressor 1 is operating in accordance with the operating parameters (upper limit value of the output frequency of the electric motor 13) updated at time point B.

[0094] 9A and 9B are time charts showing an example of the change over time of the total output of the inverter drive circuits 12a and 12b and the respective outputs when switching to emergency operation in this embodiment. Fig. 9A shows a time chart when the retry process of step S110 shown in Fig. 6 is not executed. Fig. 9B shows a time chart when the retry process of step S110 shown in Fig. 6 is executed.

[0095] 9A and 9B show an example in which a drive circuit system abnormality occurs in inverter drive circuit 12b of inverter drive circuits 12a and 12b, similar to the example shown in Fig. 8. The target pressure of the compressed gas supplied by gas compressor 1 is also similar to the example shown in Fig. 8. Also in Example 2, time charts similar to those shown in Figs. 9A and 9B can be obtained.

[0096] The operating states of the gas compressor 1 at time block A, time point B, and time block C in Figures 9A and 9B are the same as the operating states of the gas compressor 1 at time block A, time point B, and time block C in Figure 8.

[0097] Time block D in Fig. 9B indicates a time period (restart waiting time) during which the gas compressor 1 stops operating due to the retry process (step S110 shown in Fig. 6). After the operation of the gas compressor 1 is stopped, the gas compressor 1 restarts operation when the restart waiting time has elapsed.

[0098] Time point E in FIG. 9B is the time point at which the gas compressor 1 restarts operation after stopping operation for the restart waiting time.

[0099] At time point B, the compressor control device 7 executes the process of step S90 shown in FIG. 6 and compares the ratio Rn (in this embodiment, the ratio of the output Xn that can be supplied by the inverter drive circuit 12a, which is the normal drive circuit) with the ratio Rc (in this embodiment, the ratio of the current total output Xc that the inverter drive circuits 12a, 12b are supplying to the electric motor 13).

[0100] 9A, the ratio Rn is 100%, and the ratio Rc is 80% (=40%+40%). Because the ratio Rn is equal to or greater than the ratio Rc, the compressor control device 7 does not execute the retry process of step S110. Therefore, the compressor control device 7 does not execute the processes to be executed in the retry process (stopping the operation of the gas compressor 1, waiting for the restart waiting time, and restarting the operation).

[0101] Then, the compressor control device 7 sends a command to the inverter control circuit 11 to increase the output of the normal drive circuit (inverter drive circuit 12a) so that the total output of the inverter drive circuits 12a, 12b at the time point immediately before time point B (the last time point of time block A) can be maintained even after time point B. For example, as shown in Fig. 9A, the compressor control device 7 sends a command to the inverter control circuit 11 to cause the inverter drive circuit 12a to maintain the frequency of the drive current supplied to the electric motor 13 and increase the output to 80%.

[0102] As described above, if the retry process is not performed, the gas compressor 1 can switch to emergency operation while continuing its operating state without stopping operation, and the supply of compressed gas can continue without interruption.

[0103] In the example shown in Fig. 9B, the ratio Rn is 100%, and the ratio Rc is 160% (=80%+80%). Because the ratio Rn is less than the ratio Rc, the compressor control device 7 executes the retry process in step S110. Therefore, the compressor control device 7 executes the retry process in time block D in Fig. 9B, and performs the processes of stopping the operation of the gas compressor 1, waiting for the restart waiting time, and restarting the operation.

[0104] At the time immediately before time B, the total output of inverter drive circuits 12a, 12b is 80% of its upper limit, and the outputs of inverter drive circuits 12a, 12b are each 80% of their upper limit. At time B, in order to maintain the total output of inverter drive circuits 12a, 12b, if the frequency of the drive current supplied to motor 13 by inverter drive circuit 12a, which is a normal drive circuit, is maintained, the output of inverter drive circuit 12a needs to be increased to 160% of its upper limit.

[0105] Such control may result in undesirable situations, such as operation in a state where the output of the normal drive circuit (inverter drive circuit 12a) exceeds the upper limit, or loss of synchronization of the motor 13 due to a sudden change in the frequency of the drive current output by the normal drive circuit to the motor 13. The compressor control device 7 executes a retry process to avoid such situations. That is, the compressor control device 7 stops the operation of the gas compressor 1, and after the restart waiting time (time block D in FIG. 9B ) has elapsed, sends a command to the inverter control circuit 11 to set the output of the normal drive circuit (inverter drive circuit 12a) to 100%, thereby restarting the operation of the gas compressor 1 (time point E in FIG. 9B ).

[0106] As described above, the gas compressor 1 according to this embodiment updates the operating parameters of the gas compressor 1 to parameters (parameters for emergency operation) for operation using an inverter drive circuit (normal drive circuit) that is not experiencing an abnormality, even if an abnormality occurs in the inverter drive circuits 12a and 12b that supply drive current to the electric motor 13. By updating the operating parameters to parameters for emergency operation, the gas compressor 1 according to this embodiment can perform emergency operation and continue operation even if an abnormality occurs in the inverter drive circuits 12a and 12b.

[0107] In the gas compressor 1 according to this embodiment, when emergency operation is performed, the opening and closing devices 15a, 15b arranged on the primary and secondary sides of the inverter drive circuit 12b in which an abnormality has occurred automatically open, thereby isolating the inverter drive circuit 12b from the circuit and protecting the gas compressor 1. Therefore, the gas compressor 1 according to this embodiment can safely perform emergency operation.

[0108] In addition, the state of the emergency operation flag, which indicates whether the gas compressor 1 will perform emergency operation, is updated, and the memory device 19 stores the state of the emergency operation flag, so that the gas compressor 1 of this embodiment can smoothly resume operation in emergency operation mode even if the power is turned off and then turned on again.

[0109] Furthermore, the gas compressor 1 according to this embodiment does not require a standby machine or alternative equipment, so that even if an abnormality occurs in the inverter drive circuits 12a, 12b, operation can be continued inexpensively and easily.

[0110] A gas compressor 1 according to a second embodiment of the present invention will be described. When performing emergency operation, the gas compressor 1 according to this embodiment updates the target pressure of the compressed gas supplied by the gas compressor 1 as operating parameters, and changes the amount of gas discharged from the gas compressor 1. In the following description, differences between the gas compressor 1 according to this embodiment and the gas compressor 1 according to the first embodiment will be mainly described.

[0111] 10 is a diagram showing a schematic configuration of a gas compressor 1 according to this embodiment. The gas compressor 1 according to this embodiment has a configuration similar to that of the gas compressor 1 according to embodiment 1, and a piping system for circulating the compressed gas generated by the gas compressor 1 is connected to a compressed gas outlet 9. The most downstream portion of this piping system is called a piping end 31.

[0112] In this embodiment, this piping system includes a gas tank 29 and an air filter 30. The gas tank 29 is connected to the compressed gas outlet 9 by a pipe and stores the compressed gas generated by the gas compressor 1. The air filter 30 is connected by a pipe to the downstream side of the gas tank 29. Further piping is connected to the downstream side of the air filter 30. The most downstream part of this piping is the end 31.

[0113] After being discharged from the compressed gas outlet 9 to the outside of the gas compressor 1, the compressed gas passes through the gas tank 29 and the air filter 30 and is supplied to a user device from an end 31 of a pipe connected downstream of the air filter 30. The position at which the pressure sensor 6 detects the pressure of the compressed gas discharged to the outside of the gas compressor 1 is referred to as a pressure detection position 32. Hereinafter, the pressure loss of the compressed gas from the pressure detection position 32 to the end 31 of the pipe will be represented by ΔP.

[0114] 11 is a diagram showing the relationship between the pressure loss ΔP from the pressure detection position 32 to the end 31 of the piping and the amount of gas used Q. The amount of gas used Q is the amount of gas discharged from the gas compressor 1, i.e., the amount of compressed gas flowing through the piping from the pressure detection position 32 to the end 31 of the piping.

[0115] The maximum value of the amount of gas used Q (i.e., the maximum amount of gas discharged from the gas compressor 1) is designated as Qmax. Qmax may also be the rated value of the amount of gas discharged from the gas compressor 1 before switching to emergency operation. This rated value is a representative value in the product specifications of the gas compressor 1.

[0116] The pressure loss ΔP when the amount of gas used Q is at the maximum value Qmax is defined as ΔPmax.

[0117] The horizontal axis of Fig. 11 represents the ratio of the amount of gas used Q, i.e., the ratio of the amount of gas used Q to the maximum value Qmax of the amount of gas used Q. The vertical axis of Fig. 11 represents the ratio of the pressure loss ΔP, i.e., the ratio of the pressure loss ΔP to the pressure loss ΔPmax.

[0118] 11, it is known that the pressure loss ΔP of compressed gas is proportional to the square of the amount of gas used Q. For example, it is known that the pressure loss ΔP when the amount of gas used Q is 50% is 25% of the pressure loss ΔP (= ΔPmax) when the amount of gas used Q is 100% (Q = Qmax).

[0119] In particular, when the pressure loss ΔPmax when the amount of gas used Q is maximum (Q=Qmax) is known, the relationship between the amount of gas used Q and the pressure loss ΔP can be expressed by the following formula: ΔP=ΔPmax×(Q / Qmax)^2. Note that the pressure loss ΔPmax when the amount of gas used Q is maximum varies depending on the piping system installed downstream of the gas compressor 1. In this embodiment, it is assumed that the discharge gas amount of the gas compressor 1 varies with changes in the amount of gas used Q, and that the pressure loss ΔP from the pressure detection position 32 to the end of the piping 31 is proportional to the square of the amount of gas discharged from the gas compressor 1.

[0120] In this embodiment, the compressor control device 7 updates the operating parameters, namely, the target pressure of the compressed gas supplied by the gas compressor 1 and the discharge gas volume (upper limit of the output frequency of the electric motor 13) of the gas compressor 1. Below, an example will be described in which the compressor control device 7 executes airflow increase control to increase the air volume (discharge gas volume) of the gas compressor 1 by reducing the target pressure of the compressed gas during processing to switch from normal operation to emergency operation.

[0121] When the operation of gas compressor 1 is switched to emergency operation, the discharge gas amount, i.e., the amount of gas used Q, decreases. This reduces the pressure loss ΔP from pressure detection position 32 to end 31 of the pipe, and the pressure at end 31 of the pipe increases. Therefore, compressor control device 7 reduces the target pressure, which is an operating parameter, and increases the upper limit of the output frequency of motor 13 (i.e., the discharge gas amount of gas compressor 1) using the power margin created by the reduced target pressure.

[0122] FIG. 12 is a flowchart showing an example of a process for executing airflow increase control of the gas compressor 1 in a process for switching the gas compressor 1 to emergency operation according to this embodiment.

[0123] The control unit 17 of the compressor control device 7 executes the processes of steps S10 and S20 shown in Fig. 6. By the process of step S20, the control unit 17 of the compressor control device 7 opens the circuit by opening the switching devices 15a, 15b arranged on the primary and secondary sides of the inverter drive circuit (inverter drive circuit 12b in this embodiment) in which the drive circuit system abnormality has occurred. Furthermore, the control unit 17 calculates the total output of the normal drive circuits (the output that the inverter drive circuit 12a can supply to the electric motor 13).

[0124] In step S160, the control unit 17 of the compressor control device 7 determines whether the air boost control during emergency operation is enabled. The user of the gas compressor 1 sets in advance whether the air boost control during emergency operation is enabled or disabled. This setting is stored in the storage device 19 in advance. The control unit 17 can determine whether the air boost control is enabled by referring to the storage device 19. If the air boost control is enabled, the process of step S170 is executed, and if it is disabled, the remaining processes of step S20 are executed.

[0125] The remaining process in step S20 is a process of updating the operating parameters to parameters for emergency operation in the procedure described in Example 1. For example, as described in Example 1, the control unit 17 of the compressor control device 7 updates the upper limit value of the output frequency of the electric motor 13 (the amount of gas discharged from the gas compressor 1), which is an operating parameter stored in the memory 18, so as to limit the upper limit value of the rotation speed of the electric motor 13 to 50% of the normal state.

[0126] In step S170, control unit 17 refers to storage device 19 and compares target value PL of discharge pressure in air increase control during emergency operation with lower limit value PLlim of the target value of discharge pressure. Target value PL of discharge pressure is the target pressure of compressed gas in air increase control during emergency operation. Target value PL of discharge pressure in air increase control during emergency operation is determined by a calculation described below. Lower limit value PLlim of the target value of discharge pressure is a value that is predetermined for gas compressor 1 in order to protect gas compressor 1. Storage device 19 stores this lower limit value PLlim.

[0127] If the value of PL is equal to or greater than the value of PLlim, the process proceeds to S180. If the value of PL is smaller than the value of PLlim, the process proceeds to S190.

[0128] In steps S180 and S190, the control unit 17 updates the operating parameters to parameters for emergency operation.

[0129] In step S180, the control unit 17 sets the target pressure value of the compressed gas supplied by the gas compressor 1 to the target value PL of the discharge pressure in the air flow rate increase control during emergency operation, which is calculated by a calculation described below. The control unit 17 then sets the discharge gas rate of the gas compressor 1 (the upper limit of the output frequency of the motor 13) to the value QL of the used gas rate Q corresponding to the target value PL. The value QL is calculated by a calculation described below. The control unit 17 updates the operating parameters stored in the memory 18 with the operating parameters thus obtained (the target pressure of the compressed gas supplied by the gas compressor 1 and the discharge gas rate of the gas compressor 1).

[0130] In step S190, the control unit 17 sets the target pressure value of the compressed gas supplied by the gas compressor 1 to the lower limit value PLlim of the target value of the discharge pressure. Then, the control unit 17 sets the discharge gas rate of the gas compressor 1 (the upper limit value of the output frequency of the electric motor 13) to a value QLlim, which will be described later. The control unit 17 updates the operating parameters stored in the memory 18 with the operating parameters thus obtained (the target pressure of the compressed gas supplied by the gas compressor 1 and the discharge gas rate of the gas compressor 1).

[0131] After the processes of steps S180 and S190 are completed, the process of step S30 is executed.

[0132] An example of how to determine the target value PL of the discharge pressure in the air flow rate increase control during emergency operation, the value QL of the used gas amount Q corresponding to the target value PL, and the value QLlim will now be described with reference to Fig. 13. The target value PL, the value QL, and the value QLlim can be determined from the characteristics shown in Fig. 13.

[0133] FIG. 13 is a diagram showing the relationship between the target value P of the discharge pressure of the gas compressor 1 (target pressure P of the compressed gas) and the amount of gas used Q, and shows a straight line β at which the output of the inverter drive circuit is constant, and curves α1 and α2 that represent the relationship between the target pressure P and the amount of gas used Q.

[0134] The vertical axis in Fig. 13 represents pressure. Fig. 13 shows target values ​​(P1, P2, PL1, PL2) of the discharge pressure of the gas compressor 1, pressure loss ΔP (ΔP1, ΔP2) from the pressure detection position 32 to the end 31 of the piping, a lower limit value PLlim of the target value of the discharge pressure, and end pressures (PE1, PE2) required at the end 31 of the piping.

[0135] In Fig. 13, the horizontal axis represents the amount of gas used Q, i.e., the amount of gas discharged from the gas compressor 1. As in Fig. 11, the horizontal axis in Fig. 13 represents the ratio of the amount of gas used Q, i.e., the ratio of the amount of gas used Q to the maximum value Qmax of the amount of gas used Q.

[0136] First, the case where the process of step S180 shown in FIG. 12 is executed will be described.

[0137] Assume that the value of the end pressure required at the end 31 of the pipe is PE1. The target pressure P at which the value of the end pressure required at the end 31 of the pipe becomes PE1 can be expressed by the formula P = ΔP1 × (Q / Qmax)^2 + PE1 using the ratio (Q / Qmax) of the amount of gas used Q, as shown by the curve α1 in Fig. 13 .

[0138] Therefore, before switching to emergency operation, the condition for the target pressure (PL1) so that the discharge gas from the gas compressor 1 does not fall below the required end pressure (PE1) at the end 31 of the piping is that the target pressure PL1 does not fall below the sum of the pressure loss when the value of the amount of gas used Q is QL1 and the required end pressure (PE1). This condition can be expressed by the formula: PL1 ≥ ΔP1 × (QL1 / Qmax)^2 + PE1. Note that ΔP1 is the pressure loss from the pressure detection position 32 to the end 31 of the piping when the target pressure value before switching to emergency operation is P1 and the discharge gas amount is maximum (rated value Qmax).

[0139] Therefore, when the required terminal pressure is PE1, the target pressure value of the gas compressor 1 can be set to a value equal to or greater than the value given by curve α1, thereby making it possible to set the terminal pressure value at the end 31 of the piping to a value equal to or greater than the required terminal pressure (PE1).

[0140] If an abnormality occurs in the drive circuit system during operation under the conditions indicated by point a1 on curve α1 and emergency operation is performed using the process shown in Example 1, the target pressure remains the same as before switching to emergency operation, and the upper limit of the output frequency of motor 13 (the amount of gas discharged from gas compressor 1) is reduced to 50% of the value before switching to emergency operation. In other words, gas compressor 1 operates under the conditions indicated by point b1 in Figure 13.

[0141] Since the ratio of the discharge gas volume during operation under the conditions shown at point b1 is 50% of the discharge gas volume during operation under the conditions shown at point a1, the pressure loss during operation at point b1 is 25% of the pressure loss (ΔP1) during operation at point a1. Furthermore, during operation under the conditions shown at point b1, the value of the terminal pressure at the end 31 of the piping is 3 / 4ΔP higher than the required terminal pressure (PE1). As long as the value of the terminal pressure at the end 31 of the piping satisfies the required terminal pressure value (PE1), it is possible to reduce the target pressure to the value on the vertical axis shown at point c1 from curve α1 when the ratio of the discharge gas volume is 50%.

[0142] The excess output of the inverter drive circuit obtained by lowering the target pressure in this way can be used to increase the rate of discharged gas. In this case, in order to satisfy the required end pressure (PE1), it is necessary to consider that the value of the target pressure P is equal to or greater than the value given by the curve α1, and also that the current total output Xc supplied to the electric motor 13 by the inverter drive circuit does not exceed the total output Xn that the normal drive circuit can supply to the electric motor 13 (step S90 in FIG. 6).

[0143] On the other hand, as shown by the straight line β in Fig. 13, the relationship between the target pressure P and the amount of gas used Q (the amount of gas discharged or the upper limit of the output frequency) that does not exceed the upper limit of the output that the inverter drive circuit can supply can be expressed by the following formula, for example: P = aQ + b This straight line β passes through point b1 and is a straight line on which the output of the inverter drive circuit is constant.

[0144] The condition for preventing the output of the normal drive circuit from exceeding the total output Xn that the normal drive circuit can supply to the motor 13 due to an increase in the amount of discharged gas (i.e., by controlling the increased airflow rate) is that the motor should be operated with a target pressure and discharged gas that are equal to or less than the value given by the straight line β. This condition can be expressed by the formula PL1≦aQL1+b. The constant a is a value determined according to the rated value of the target pressure. The constant b is a value determined according to the lower limit of the target pressure.

[0145] In this embodiment, the relationship between the target pressure P and the amount of gas used Q (the amount of gas discharged, or the upper limit of the output frequency) that does not exceed the upper limit of the output that can be supplied by the inverter drive circuit is expressed by a mathematical formula that represents a straight line, but it can also be expressed by a mathematical formula that represents a curve, for example, rather than a mathematical formula that represents a straight line.

[0146] As described above, when the processing of step S180 shown in Fig. 12 is executed, the condition under which the value of the end pressure at the end 31 of the pipe satisfies the required end pressure (PE1) and the output of the normal drive circuit does not exceed the total output that the normal drive circuit can supply to the motor 13 is given by the intersection d1 of the curve α1 and the straight line β shown in Fig. 13. From the intersection d1, the target pressure PL (PL1) and the value QL (QL1) of the amount of gas used Q corresponding to the target pressure PL can be obtained.

[0147] Next, a case where the process of step S190 shown in FIG. 12 is executed will be described.

[0148] Assume that the required end pressure value at the end 31 of the pipe is PE2, which is smaller than PE1. In this case, as shown in Fig. 13, the point at which the end pressure value at the end 31 of the pipe satisfies the required end pressure (PE2) and the output of the normal drive circuit does not exceed the total output that the normal drive circuit can supply to the motor 13 is the intersection d2 of the pressure loss curve α2 and the straight line β.

[0149] The curve α2 is expressed by the formula P = ΔP2 × (Q / Qmax)^2 + PE2, where ΔP2 is the pressure loss from the pressure detection position 32 to the end 31 of the pipe when the target pressure value before switching to emergency operation is P2 and the discharge gas volume is at its maximum (Qmax).

[0150] The intersection point d2 shown in Fig. 13 is the intersection point between the pressure loss curve α2 and the straight line β, and provides a candidate target pressure value PL2 for the air flow increase control during emergency operation. However, as shown in Fig. 13, if the required terminal pressure value PE2 is small and the target pressure value P2 before switching to emergency operation is small, the value of PL2 provided by the intersection point d2 may fall below the lower limit value PLlim of the target value of the discharge pressure.

[0151] In this case, in order to protect the gas compressor 1, the target pressure in the air increase control during emergency operation is set to the lower limit PLlim. The discharge gas volume (amount of gas used Q) is set to a value QLlim obtained from the lower limit PLlim by the line β. In Figure 13, the point determined by the target pressure lower limit PLlim and the discharge gas volume QLlim is indicated by d2'. Point d2' indicates the operation in which the target pressure is lowest and the discharge gas volume is greatest during the air increase control during emergency operation.

[0152] As described above, when the processing of step S190 shown in Fig. 12 is executed, the gas compressor 1 is operated under the condition shown by point d2' in Fig. 13. The value of QLlim can be obtained from point d2'.

[0153] FIG. 14 is a time chart showing an example of changes in the state of the gas compressor 1 before and after switching to emergency operation when the airflow increase control is executed in this embodiment.

[0154] The time chart shown in Figure 14 is almost identical to the time chart shown in Figure 8 in Example 1, but differs from the time chart shown in Figure 8 in that the value of the target pressure, which is an operating parameter, changes before and after switching to emergency operation, and the upper limit value of the output frequency, which is an operating parameter, decreases from 100% before switching to emergency operation to 58%.

[0155] As in Example 1, time block A is the state at step S30 of the flowchart shown in Figure 6, and is a time period indicating that the gas compressor 1 is in a normal operating state (not in emergency operation) with no abnormality in the drive circuit system.

[0156] At time point B, as in Example 1, an abnormality occurs in the drive circuit system of the operating gas compressor 1, and the state of the emergency operation flag stored in the storage device 19 is updated from OFF to ON. At this time, the total output that can be supplied to the motors 13 of the two inverter drive circuits 12a and 12b has decreased to 50% of the total output in time block A.

[0157] In this embodiment, thereafter, the control unit 17 of the compressor control device 7 determines whether or not the air increase control during emergency operation is enabled in accordance with the process of step S160 shown in Fig. 12. If the air increase control is enabled, the process of step S170 is executed.

[0158] In step S170, the control unit 17 compares the lower limit value PLlim (0.45 MPa in FIG. 13 ) of the target value of the discharge pressure with the target value PL1 (0.60 MPa in FIG. 13 ) of the discharge pressure in the air flow rate increase control during emergency operation. The target value PL1 is a value given by the intersection d1 of the curve α1 and the line β. As already mentioned, the curve α1 is determined from the required end pressure value PE1 and the pressure loss ΔP1 up to the end 31 of the piping when the discharge gas volume of the gas compressor 1 is the rated value (the ratio of the discharge gas volume to the rated value is 100%). The line β represents the condition under which the output of the inverter drive circuit is constant.

[0159] In this embodiment, as shown in FIG. 13, the value of PL1 is equal to or greater than the value of PLlim, so the process of S180 in FIG. 12 is executed.

[0160] In step S180, the control unit 17 sets the target pressure value to a target value PL1 (0.60 MPa in FIG. 13), and sets the discharge gas amount (upper limit of the output frequency) to the used gas amount value QL1 (58% in FIG. 13). In this way, the control unit 17 updates the operating parameters (target pressure and upper limit of the output frequency).

[0161] Time block C in Fig. 14 is a time period indicating that the gas compressor 1 is in emergency operation, similar to time block A, and corresponds to step S30 of the flowchart shown in Fig. 6. In time block C, the gas compressor 1 is performing emergency operation while executing the airflow increase control in accordance with the operating parameters (target pressure and upper limit value of the output frequency) updated at time point B.

[0162] As described above, the gas compressor 1 according to this embodiment, like the gas compressor 1 according to the first embodiment, can perform emergency operation and continue operation even if an abnormality occurs in the inverter drive circuits 12 a, 12 b, by updating the operating parameters to parameters for emergency operation.

[0163] Furthermore, in emergency operation, the gas compressor 1 according to this embodiment can execute air boost control by taking into consideration the relationship between the target pressure P of the discharge gas and the amount of discharge gas (amount of gas used Q) that does not exceed the upper limit of the output that can be supplied by the inverter drive circuit, using the pressure loss ΔP from the pressure detection position 32 to the end 31 of the pipe and the value of the end pressure required at the end 31 of the pipe. In this embodiment, the pressure at the end 31 of the pipe can be set to the required end pressure without changing the output (drive current) supplied to the motor 13 from the first embodiment, and further, a larger amount of discharge gas can be obtained by air boost control than in the first embodiment.

[0164] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to embodiments that include all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to delete part of the configuration of each embodiment, or to add or replace other configurations.

[0165] 1...gas compressor, 2...suction filter, 3...suction throttle valve, 4...compressor body, 5...check valve, 6...pressure sensor, 7...compressor control device, 8...solenoid valve, 9...compressed gas outlet, 10...compressor display and operation unit, 11...inverter control circuit, 12a, 12b...inverter drive circuit, 13...electric motor, 14a, 14b, 15a, 15b...opening and closing device, 16...power supply terminal block, 17...control unit, 18...memory, 19...storage device, 20...input / output I / F, 21...communication I / F, 22...display unit, 23...input / output I / F, 24...control unit, 25...communication I / F, 26...diode, 27...capacitor, 28...power switching element, 29...gas tank, 30...air filter, 31...end of piping, 32...pressure detection position

Claims

1. A gas compressor comprising a compressor main body which generates compressed gas and which operates in accordance with operating parameters, comprising: an electric motor which drives the compressor main body; a plurality of drive circuits which supply a drive current to the electric motor as an output; and a compressor control device which has a memory device and is capable of detecting the occurrence of an abnormality in the drive circuits; wherein when an abnormality occurs in the drive circuits, an operation performed by the gas compressor is set as emergency operation, and the operating parameters for operating the gas compressor using only normal drive circuits which are drive circuits among the plurality of drive circuits and which are not experiencing an abnormality are set as parameters for emergency operation, and the compressor control device is configured to, when it detects the occurrence of an abnormality in the drive circuits, execute a process of updating the operating parameters to parameters for emergency operation if the total output which the normal drive circuits can supply to the electric motor is equal to or greater than the total output which the drive circuits were supplying to the electric motor immediately before the occurrence of the abnormality in the drive circuits was detected.

2. The gas compressor according to claim 1, wherein the operating parameters include at least one of an upper limit of an output frequency of the electric motor and a target pressure of the compressed gas.

3. The gas compressor according to claim 1, further comprising an opening / closing device arranged on the primary side and the secondary side of the drive circuit, wherein the compressor control device opens the opening / closing device arranged on the drive circuit in which an abnormality has occurred when updating the operating parameters.

4. The gas compressor according to claim 1, wherein the storage device stores a setting as to whether the emergency operation is enabled or not, and the compressor control device executes a process of updating the operating parameters when the emergency operation is set to enabled.

5. The gas compressor as described in claim 1, wherein when the state is on, a flag indicating that the gas compressor will perform the emergency operation is set to an emergency operation flag, the storage device stores the state of the emergency operation flag, and when the compressor control device detects that an abnormality has occurred in the drive circuit, the compressor control device sets the state of the emergency operation flag stored in the storage device to on, and when the emergency operation flag is on, the compressor control device executes a process to update the operating parameters.

6. A gas compressor as described in claim 2, comprising: a compressed gas outlet for discharging the compressed gas to the outside; and a pressure sensor for detecting the pressure of the compressed gas discharged to the outside, wherein the compressor control device updates the operating parameters based on a terminal pressure required at an end which is the most downstream part of a piping system connected to the compressed gas outlet, a pressure loss of the compressed gas from a pressure detection position where the pressure sensor detects the pressure to the end, a predetermined lower limit value of the target pressure, and a relationship between the target pressure and the discharge gas volume of the gas compressor.

7. The gas compressor according to claim 6, wherein the storage device stores a setting as to whether or not the air boost control during the emergency operation is enabled, and the compressor control device updates the operating parameters when the air boost control during the emergency operation is set to enabled.

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