JP2024034180A - gas compressor - Google Patents

Abstract

[Problem] Gas compressor capable of switching an electric motor from star connection to delta connection at the time of startup at an appropriate timing even when the conditions that change the starting torque of the gas compressor, such as the ambient temperature of the gas compressor, are different. provide a machine. A gas compressor includes a pump 11 mechanically connected to an electric motor 4 that drives compressor bodies 2 and 3, and an oil supply system 10 that supplies oil from the pump 11 to the compressor body. a pressure sensor 16 that detects the pressure of oil flowing through the motor, a starting device 31 that can switch the connection state of the electric motor 4 between a first connection that is a star connection and a second connection that is a delta connection, and a control that controls the starting device 31. A device 40 is provided. The control device 40 connects the starter 31 as a first connection when starting the compressor main body, determines whether the detected pressure value of the pressure sensor 16 is equal to or higher than the pressure threshold Pth during starting the compressor main body, and determines whether the detected pressure value is equal to or higher than the pressure threshold Pth. When it is determined that Pth is greater than or equal to the threshold value Pth, the starting device 31 is switched from the first connection to the second connection. [Selection diagram] Figure 2

Description

The present invention relates to a gas compressor, and more particularly to a gas compressor driven by an electric motor.

In a gas compressor, an electric motor is used as the prime mover of the compressor body. As a starting method for the electric motor that drives the gas compressor, a starting method using a star-delta connection is widely adopted. The star-delta connection is a star connection at the start of startup of the gas compressor (low rotational speed region of the electric motor), and is switched to delta connection after a predetermined time (for example, about 15 seconds) has elapsed since the start of startup. This method has the advantage that the electric motor starting device can be constructed at a relatively lower cost than other methods. However, this starting method does not allow excessive current to flow into the electric motor if the electric motor is only able to accelerate to a rotational speed insufficient for the maximum speed or rated speed when switching from star to delta connection. Flowing may cause tripping.

As a method for starting a compressor using star-delta connection, for example, the technique described in Patent Document 1 is known. The technology described in Patent Document 1 aims to optimize the start-up time of the electric motor by setting the time for supplying current to the electric motor by star connection to an appropriate time depending on the temperature of the lubricating oil of the compressor. . Specifically, the method for starting a compressor described in Patent Document 1 measures the temperature of oil that lubricates the compressor body, and determines the star time, which is the time during which current is supplied to the electric motor, by measuring the temperature of the oil that lubricates the compressor body. It is derived based on the temperature of , and switches from star connection to delta connection when the derived star time has elapsed.

Japanese Patent Application Publication No. 2015-78607

The startup time of the electric motor of the gas compressor, that is, the time it takes for the electric motor to reach its maximum speed or rated speed from the start of startup, varies depending on the magnitude of the load torque applied to the electric motor. The load torque is the torque required to accelerate the compressor body of the gas compressor. The load torque changes depending on, for example, a difference in the ambient temperature of the gas compressor. When the ambient temperature of the gas compressor changes, the temperature of the lubricating oil supplied to the compressor body changes, resulting in a change in the starting torque of the compressor body. The load torque may change not only due to differences in the ambient temperature of the gas compressor, but also due to differences in the flow rate of lubricating oil supplied to the compressor body and other factors.

The technique described in Patent Document 1 derives the star time based on the measured temperature of the lubricating oil of the compressor. That is, the switching timing (star time) from star connection to delta connection is estimated using the temperature of lubricating oil, which has little direct correlation with the rotation speed of the electric motor. Therefore, in this technology, if the starting torque of the compressor body changes due to the ambient temperature of the gas compressor and other factors (such as the amount of lubricating oil supplied), it is necessary to switch from star connection to delta connection. It is difficult to determine the appropriate switching timing, that is, whether the maximum speed or rated speed of the electric motor has been reached.

The present invention has been made to solve the above problems, and its purpose is to solve the above problems even when the conditions under which the starting torque of the gas compressor changes, such as the ambient temperature of the gas compressor, are different. An object of the present invention is to provide a gas compressor that can switch an electric motor from star connection to delta connection at appropriate timing during startup.

The present application includes multiple means for solving the above problems. One example is a compressor body that compresses gas, an electric motor that drives the compressor body, and a pump that is mechanically connected to and driven by the electric motor, and the gas is discharged from the pump. An oil supply system that supplies oil to the compressor body, a pressure sensor that detects the pressure of oil flowing through the oil supply system, and a star connection that is electrically connected to the electric motor and determines the connection state of the windings of the electric motor. a starting device having an electric circuit that can be switched between a first connection to make a delta connection and a second connection to make a delta connection; and a control device for controlling connection of the electric circuit of the starter, the control device comprising: , when the start-up of the compressor main body is started, the electric circuit of the starting device is connected to the first connection, and the pressure value detected by the pressure sensor during the start-up of the compressor main body is equal to or higher than a pressure threshold value. When it is determined in the switching determination that the pressure value detected by the pressure sensor is equal to or higher than the pressure threshold value, the electric circuit of the starting device is disconnected from the first connection. The second connection is configured to switch to the second connection.

According to the present invention, since there is a correlation between the rotational speed of the electric motor that drives the compressor body and the pump and the supply pressure of oil from the pump, when the compressor body is started, the compressor body is By monitoring the oil supply pressure from the pump driven by the electric motor, it is possible to determine the appropriate timing to switch the electric motor connection state from star connection to delta connection. Therefore, even if the conditions that change the starting torque of the gas compressor, such as the ambient temperature of the gas compressor, are different, the starting device changes the electric motor from star connection to delta connection when starting the gas compressor. Switching can be performed at appropriate timing.
Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

1 is a system diagram showing a schematic configuration of a gas compressor according to an embodiment of the present invention. 2 is a flowchart showing an example of a procedure for starting a gas compressor by a control device that constitutes a part of the gas compressor according to the embodiment shown in FIG. 1. FIG. 2 is a graph showing the relationship between the rotational speed of the electric motor and the supply pressure from the pump at the time of starting the gas compressor according to the embodiment shown in FIG. 1. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a gas compressor according to the present invention will be described by way of example with reference to the drawings. In this embodiment, a screw type gas compressor is used as an example of the gas compressor. However, the present invention can be applied to all gas compressors driven by three-phase electric motors, such as scroll-type gas compressors and double-acting gas compressors.

[One embodiment]
The configuration of a gas compressor according to one embodiment will be described using FIG. 1. FIG. 1 is a system diagram showing a schematic configuration of a gas compressor according to an embodiment. In FIG. 1, black arrows indicate the flow of working fluid or lubricating oil of the gas compressor.

In FIG. 1, a gas compressor 1 is configured as a screw type compressor. The gas compressor 1 includes a low-pressure pre-stage compressor main body 2 that compresses and discharges the sucked gas, and a high-pressure post-stage compressor main body that further compresses and discharges the compressed gas discharged from the pre-compressor main body 2. 3, and an electric motor 4 that drives the front compressor body 2 and the rear compressor body 3. A gas filter 6 is arranged on the suction side of the pre-stage compressor main body 2. The discharge side of the front compressor body 2 and the suction side of the rear compressor body 3 are connected via an intercooler 7. The discharge side of the latter stage compressor main body 3 is connected to an aftercooler 8.

The front compressor body 2 and the rear compressor body 3 include a pair of screw rotors that mesh with each other and rotate, a plurality of bearings that rotatably support the pair of screw rotors, and a casing that accommodates the pair of screw rotors and the plurality of bearings. (It is shown schematically in FIG. 1, and each structure is not shown.) A plurality of working chambers are formed by a pair of screw rotors and a casing surrounding them. The plurality of working chambers move in the axial direction of the pair of screw rotors as the pair of screw rotors rotate. The front compressor body 2 and the rear compressor body 3 suck gas through the gas filter 6 as the volume of the working chamber increases as the pair of screw rotors rotate, and the volume of the working chamber decreases. This compresses the gas and finally discharges the compressed gas. The front compressor body 2 and the rear compressor body 3 are, for example, oil-free screw compressors that do not supply oil to the working chamber, and have timing gears that synchronize the rotation of a pair of screw rotors. are doing.

The intercooler 7 cools the high-temperature compressed gas discharged from the pre-compressor main body 2, and is, for example, an air-cooled heat exchanger. The aftercooler 8 cools the high temperature compressed gas discharged from the latter stage compressor main body 3, and is, for example, an air-cooled heat exchanger.

An oil supply system 10 is connected to the front compressor body 2 and the rear compressor body 3. The oil supply system 10 supplies lubricating oil for lubricating the bearings of the screw rotor and the timing gear to the front compressor body 2 and the rear compressor body 3. The oil supply system 10 includes, in order from the upstream side, a pump 11 that supplies lubricating oil to the front compressor body 2 and the rear compressor body 3, and a lubricant that is supplied from the pump 11 to the front compressor body 2 and the rear compressor body 3. It includes an oil cooler 12 that cools oil, and an oil filter 13 that filters out impurities contained in the lubricating oil supplied from the pump 11 to the front compressor body 2 and the rear compressor body 3. The pump 11 is configured to be mechanically connected to and driven by an electric motor 4 that drives the front compressor body 2 and the rear compressor body 3. A discharge line of the pump 11 is connected to a gear case 26 of a gear device 20, which will be described later, via a pressure regulating valve 14. The pressure regulating valve 14 is configured to open when the discharge pressure of the pump 11 exceeds a set pressure. When the pressure regulating valve 14 is opened, excess pressure is released to the gear case 26, and the pressure of the lubricating oil supplied to the bearings and timing gears of the front compressor body 2 and the rear compressor body 3 is kept approximately constant. It has a function.

A pressure sensor 16 and a temperature sensor 17 are installed downstream of the oil filter 13 in the oil supply system 10. The pressure sensor 16 detects the pressure of oil discharged from the pump 11 and flowing through the oil supply system 10. The pressure sensor 16 of this embodiment, like existing pressure sensors, detects the pressure of lubricating oil flowing out from the oil filter 13 and introduced into the front compressor body 2 and the rear compressor body 3. , has a function of monitoring the supply pressure of lubricating oil to the front stage compressor body 2 and the rear stage compressor body 3. The temperature sensor 17 detects the temperature of the lubricating oil that is cooled by the oil cooler 12 and then introduced into the first stage compressor main body 2 and the second stage compressor main body 3.

The front compressor body 2 and the rear compressor body 3 are mechanically connected to an electric motor 4 via a gear device 20 . The pump 11 of the oil supply system 10 is also mechanically connected to the electric motor 4 via a gear device 20 . The gear device 20 includes a motor-side bull gear 21 and a motor-side pinion 22 provided on the shaft portion of the electric motor 4, and a pre-stage pinion provided on the shaft portion of the screw rotor of the pre-stage compressor main body 2 and meshing with the motor-side bull gear 21. 23, a rear-stage pinion 24 that is provided on the shaft of the screw rotor of the rear-stage compressor main body 3 and meshes with the motor-side bull gear 21, and a pump-side gear 25 that is provided on the shaft of the pump 11 and meshes with the motor-side pinion 22. , and a gear case 26 that accommodates these gears 21, 22, 23, 24, and 25. The driving torque of the electric motor 4 is transmitted from the motor-side bull gear 21 to the front-stage compressor body 2 via the front-stage pinion 23, and is also transmitted from the motor-side bull gear 21 to the rear-stage compressor body 3 via the rear-stage pinion 24. be done. Further, the driving torque of the electric motor 4 is transmitted from the motor side pinion 22 to the pump 11 via the pump side gear 25. Lubricating oil for the oil supply system 10 is stored in the lower part of the gear case 26. That is, the gear case 26 also functions as a storage tank for lubricating oil in the oil supply system 10. Lubricating oil in the oil supply system 10 circulates between the front compressor main body 2, the second compressor main body 3, and the gear case 26.

The electric motor 4 is a three-phase electric motor having three-phase windings. The electric motor 4 is electrically connected to a starting device 31 and is configured to be connected to a power source 100 via the starting device 31. The starting device 31 has an electric circuit (not shown) that can switch the connection state of the windings of the electric motor 4 between a first connection, which is a star connection, and a second connection, which is a delta connection. It is possible to adjust the current or voltage applied to the electric motor 4 from the power source 100 by switching the connection of the electric circuit. The starting device 31 is configured to switch the electric circuit to the first connection (star connection) or the second connection (delta connection) in response to a switching command Cs from the control device 40. Note that the power source 100 may be an external power source for the gas compressor 1 or may be a part of the configuration of the gas compressor 1.

When an operation command signal is input from an operation switch or an external control panel (both not shown), the control device 40 controls the connection of the electric circuit of the starting device 31 to supply electric power from the power source 100 to the electric motor 4. The gas compressor 1 (first stage compressor main body 2 and second stage compressor main body 3) is started. The control device 40 employs a star-delta connection starting method as a starting method for the electric motor 4. The control device 40 of the present embodiment monitors the pressure of lubricating oil discharged by the pump 11 and flowing through the oil supply system 10 using the pressure sensor 16 while the gas compressor 1 (electric motor 4) is being started. The present invention is characterized in that the switching timing from star connection to delta connection is determined based on the detected value of . Details of how the control device 40 starts the gas compressor 1 (electric motor 4) will be described later.

Next, the operation (operation) of the gas compressor according to one embodiment will be explained using FIG. 1. During normal operation of the gas compressor, the front compressor main body and the latter compressor main body (electric motor) are controlled to be driven at a substantially constant rotation speed.

In the gas compressor 1 having the above-described configuration shown in FIG. The machine body 2 and the rear compressor body 3 are rotationally driven. As a result, gas (for example, air) is sucked into the front compressor main body 2 via the gas filter 6. The sucked gas is compressed by the pre-compressor main body 2 and then discharged to the intercooler 7. The high temperature compressed gas discharged from the front compressor body 2 is cooled by the intercooler 7 and then sucked into the rear compressor body 3. The cooled compressed gas is further compressed by the latter stage compressor main body 3 and then discharged to the aftercooler 8. The high-temperature, high-pressure compressed gas discharged from the second-stage compressor main body 3 is cooled to a desired temperature by the aftercooler 8 and then supplied to external equipment (not shown).

Further, the rotational driving force of the electric motor 4 is transmitted from the motor side pinion 22 of the gear device 20 to the pump side gear 25, so that the pump 11 of the oil supply system 10 is rotationally driven. As a result, the lubricating oil stored in the gear case 26 of the gear device 20 is pumped to the oil cooler 12 by the pump 11. The lubricating oil discharged from the pump 11 is cooled by an oil cooler 12, and impurities are filtered out by an oil filter 13. The cooled and purified lubricating oil is supplied to the front compressor body 2 and the rear compressor body 3 (bearings, timing gears, etc.). When the discharge pressure of the pump 11 is greater than the set pressure, the pressure regulating valve 14 is opened. Therefore, the discharge pressure of the pump 11 is maintained substantially constant.

The pressure and temperature of the lubricating oil (lubricating oil flowing on the most downstream side of the oil supply system 10) introduced into the front compressor body 2 and the rear compressor body 3 are detected by a pressure sensor 16 and a temperature sensor 17, respectively. The pressure sensor 16 outputs a detection signal to the control device 40 according to the detected pressure value of the lubricating oil. The temperature sensor 17 outputs a detection signal to the control device 40 according to the detected temperature value of the lubricating oil. The control device 40 monitors the state (pressure and temperature) of the lubricating oil supplied to the front compressor body 2 and the rear compressor body 3 based on the detection signal from the pressure sensor 16 and the detection signal from the temperature sensor 17. do.

Next, a hardware configuration of a control device that constitutes a part of a gas compressor according to an embodiment and a method for starting the gas compressor using the control device will be described using FIGS. 1 and 2. FIG. 2 is a flowchart showing an example of a procedure for starting a gas compressor by a control device that constitutes a part of the gas compressor according to the embodiment shown in FIG.

In FIG. 1, the control device 40 of the gas compressor 1 is constituted by a microcomputer including, as a hardware configuration, a storage device 41 consisting of a RAM, ROM, etc., and a processing device 42 consisting of a CPU, MPU, etc. In the storage device 41, programs and various information necessary for starting the gas compressor 1 are stored in advance. The processing device 42 starts up the gas compressor 1 by reading a program and various information from the storage device 41 as appropriate and executing processing according to the program.

Specifically, in FIG. 2, the control device 40 shown in FIG. control flow). First, the control device 40 sets the electric circuit of the starting device 31 to a first connection in which the connection state of the windings of the electric motor 4 is a star connection, and connects the electric circuit of the starting device 31 to the power source 100 via the starting device 31 set to the first connection. is supplied to the electric motor 4 (the windings are connected in a star connection) (step S10). As a result, starting of the electric motor 4 is started. By starting the electric motor 4, the front compressor body 2 and the rear compressor body 3 are started, and the pump 11 is started.

Next, the control device 40 determines whether the pressure of the lubricating oil flowing through the oil supply system 10 is equal to or higher than the pressure threshold (step S20). This is to determine when to switch the connection state of the windings of the electric motor 4 from star connection to delta connection. In a starting method using a star-delta connection of an electric motor, a switch to a delta connection is required when the electric motor reaches a maximum speed or rated speed or its vicinity. In this embodiment, the discharge pressure of the pump 11 that is mechanically connected to and driven by the electric motor 4 changes in accordance with the increase or decrease in the rotational speed of the electric motor 4. That is, there is a correlation between the rotational speed of the electric motor 4 and the discharge pressure of the pump 11 (see FIG. 3, which will be described later). Therefore, the control device 40 determines whether the rotational speed of the electric motor 4 has reached an appropriate rotational speed for switching to the delta connection based on the pressure of the lubricating oil discharged from the pump 11 and flowing through the oil supply system 10. It is configured to make a determination.

Specifically, the control device 40 determines whether the pressure detection value Ps from the pressure sensor 16 is greater than or equal to the pressure threshold Pth. If the pressure detection value Ps is smaller than the pressure threshold Pth (in the case of NO), the process returns to step S20 again, and the process continues in step S20 until the pressure detection value Ps from the pressure sensor 16 becomes equal to or higher than the pressure threshold Pth (YES). repeat. If the pressure detection value Ps from the pressure sensor 16 reaches the pressure threshold Pth or more (in the case of YES), the control device 40 proceeds to step S30.

The pressure threshold value Pth is, for example, a preset fixed value, and is stored in the storage device 41 in advance. However, since the pressure of the lubricating oil flowing through the oil supply system 10 differs depending on the detection position, it is necessary to set it to an appropriate value depending on the installation position of the pressure sensor 16. In the present embodiment, the pressure sensor 16 is installed downstream of the oil filter 13, which is the most downstream side of the oil supply system 10, and lubricates the oil immediately before being introduced into the front compressor body 2 and the rear compressor body 3. Detecting oil pressure. In this case, the pressure of the lubricating oil discharged from the pump 11 is a value lower than the pump discharge pressure due to pressure loss in the oil cooler 12, pressure loss in the oil filter 13, pressure loss in the pipeline, etc. . Therefore, the pressure threshold Pth is determined by the discharge pressure or discharge flow rate of the pump 11 when the electric motor 4 is at the maximum speed or rated speed (when the gas compressor 1 is in normal operation), the pressure loss at the oil cooler 12, the oil filter 13 It is set taking into consideration the pressure loss in the pipe and the pressure loss in the pipeline.

In step S20, when the pressure detection value Ps from the pressure sensor 16 reaches the pressure threshold Pth or more (in the case of YES), the control device 40 switches the electric circuit of the starting device 31 from the first connection to the second connection ( Step S30). That is, the connection state of the windings of the electric motor 4 is switched from star connection to delta connection. Specifically, the control device 40 outputs the switching command Cs to the starting device 31. As described above, since there is a correlation between the rotational speed of the electric motor 4 and the discharge pressure of the pump 11, when the pressure detection value Ps from the pressure sensor 16 reaches the pressure threshold value Pth or more, the electric motor 4 It is assumed that the rotation speed has reached the appropriate rotation speed for switching to delta connection.

Next, the operation at startup of the gas compressor according to one embodiment will be described using FIGS. 1 to 3. FIG. 3 is a graph showing the relationship between the rotational speed of the electric motor and the supply pressure from the pump when the gas compressor according to the embodiment shown in FIG. 1 is started. In Figure 3, the horizontal axis T represents the elapsed time from the start of the gas compressor, the vertical axis R and the solid line on the right side represent the rotational speed of the electric motor, and the vertical axis P and the dashed dotted line on the left side represent the previous stage from the pump in the refueling system. It shows the supply pressure of lubricating oil to the compressor and downstream compressor.

The control device 40 shown in FIG. 1 starts starting up the gas compressor 1 when the operation command signal is input (when the elapsed time T shown in FIG. 3 is 0). Specifically, the control device 40 sets the electric circuit of the starting device 31 to the first connection in which the connection state of the windings of the electric motor 4 is a star connection, and connects the electrical circuit of the starting device 31 to the electric power of the power source 100 via the starting device 31. It is supplied to the motor 4 (step S10 shown in FIG. 2).

As a result, starting of the electric motor 4 shown in FIG. 1 is started. By starting the electric motor 4, the front compressor body 2 and the rear compressor body 3 are started, and the pump 11 of the oil supply system 10 is started. As shown in FIG. 3, the electric motor 4 is accelerated by the supply of electric power from the power supply 100, so that the rotational speed gradually increases according to the elapsed time T from the start of activation. As the rotation speed of the electric motor 4 increases, the rotation speed of the pump 11 of the oil supply system 10 also increases. As a result, the pressure P of the lubricating oil supplied from the pump 11 to the front compressor body 2 and the rear compressor body 3 gradually increases in accordance with the elapsed time T from the start of startup.

At this time, the control device 40 determines whether the pressure P (detected value of the pressure sensor 16) of the lubricating oil supplied from the pump 11 to the front compressor body 2 and the rear compressor body 3 is equal to or higher than the pressure threshold Pth. By making this determination, the timing of switching from star connection to delta connection is determined (step S20 shown in FIG. 2). In FIG. 3, during the elapsed time T from 0 to Ts, the supply pressure P of lubricating oil from the pump 11 (detected value of the pressure sensor 16) has not reached the pressure threshold value Pth, so the control device 40 31 in the first connection (repetition of step S20 shown in FIG. 2), power supply to the electric motor 4 whose windings are star-connected is maintained.

When the supply pressure P of lubricating oil from the pump 11 (detected value of the pressure sensor 16) reaches the pressure threshold Pth, that is, when the elapsed time T is Ts, the control device 40 controls the connection of the windings of the electric motor 4. The state is switched from star connection to delta connection (step S30 shown in FIG. 2). At this time (at the elapsed time Ts), the rotation speed of the electric motor 4 has reached the maximum speed or the rated speed Rr due to the acceleration of the electric motor 4 due to the electric power supply. Therefore, excessive current does not flow through the electric motor 4, and the starting of the electric motor 4 can be completed.

As described above, in this embodiment, when the electric motor 4 (gas compressor 1) is started, by monitoring the supply pressure of lubricating oil from the pump 11, which has a correlation with the rotational speed of the electric motor 4, The appropriate timing for switching the connection state of the electric motor 4 from star connection to delta connection is being determined.

As described above, the gas compressor according to one embodiment includes a pre-stage compressor main body 2 and a post-stage compressor main body 3 (compressor main bodies) that compress gas, and a pre-stage compressor main body 2 and a post-stage compressor main body 3. It includes an electric motor 4 that drives the (compressor main body) and a pump 11 that is mechanically connected to and driven by the electric motor 4. An oil supply system 10 that supplies the compressor body 3 (compressor body), a pressure sensor 16 that detects the pressure of lubricating oil (oil) flowing through the oil supply system 10, and an electric motor 4 that is electrically connected to the electric motor 4. a starting device 31 having an electric circuit that can switch the connection state of the windings between a first connection in which the winding is a star connection and a second connection in which the connection is a delta connection; and a control for controlling the connection of the electric circuit of the starter 31. A device 40 is provided. The control device 40 connects the electric circuit of the starting device 31 as a first connection when starting up the pre-stage compressor main body 2 and the post-compressor main body 3 (compressor main body). A switching determination is made to determine whether the pressure value detected by the pressure sensor 16 is equal to or higher than the pressure threshold Pth during startup of the main body 3 (compressor main body), and the pressure value detected by the pressure sensor 16 in the switching determination is The electric circuit of the starting device 31 is configured to be switched from the first connection to the second connection when it is determined that the pressure is equal to or higher than the pressure threshold value Pth.

According to this configuration, the rotational speed of the electric motor 4 that drives the front compressor body 2, the rear compressor body 3 (compressor body), and the pump 11 and the supply pressure of lubricating oil (oil) from the pump 11 can be adjusted. Since there is a correlation between By monitoring the supply pressure of lubricating oil (oil) from the pump 11 driven by the electric motor 4, it is possible to determine the appropriate timing to switch the connection state of the electric motor 4 from star connection to delta connection. Therefore, even if the conditions under which the starting torque of the gas compressor changes, such as the ambient temperature of the gas compressor 1, are different, the star connection of the electric motor 4 by the starting device 31 at the time of starting the gas compressor 1 can be prevented. Switching to delta connection can be performed at appropriate timing.

Further, in this embodiment, the pressure threshold value Pth is a preset fixed value and is stored in the control device 40 in advance. According to this configuration, the control flow for starting the control device 40 can be simplified.

In addition, in the present embodiment, the oil supply system 10 cools lubricating oil (oil) supplied from the pump 11 to the pre-stage compressor main body 2 and the post-stage compressor main body 3 (compressor main body), in addition to the pump 11. an oil cooler 12 (heat exchanger); and an oil filter 13 (filter) that filters impurities in the lubricating oil (oil) supplied from the pump 11 to the front compressor body 2 and the rear compressor body 3 (compressor body). including. Further, the pressure sensor 16 is installed downstream of the oil cooler 12 (heat exchanger) and the oil filter 13 (filter) in the oil supply system 10.

According to this configuration, since the installation position of the pressure sensor 16 in the oil supply system 10 is the same as that in the oil supply system of an existing gas compressor, when the gas compressor 1 is started, the electric motor 4 is connected from the star connection to the delta connection. There is no need for a new pressure sensor to determine the switching timing, and the existing pressure sensor can be used.

[Other embodiments]
Note that the present invention is not limited to the embodiments described above, and includes various modifications. The embodiments described above have been described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. That is, it is also possible to add, delete, or replace a part of the configuration of one embodiment with other configurations.

For example, in the embodiment described above, the front compressor body 2 and the rear compressor body 3 are configured as a liquid-free screw compressor that does not inject liquid such as oil or water into the working chamber. showed that. However, it is also possible to configure the front compressor main body and the latter compressor main body as a liquid supply type screw compressor in which a liquid such as oil or water is injected into the working chamber. When the liquid injected into the working chamber is lubricating oil, the oil supply system 10 in one embodiment is configured to supply lubricating oil to the working chambers of the front compressor main body and the latter compressor main body. is also possible.

Furthermore, in the embodiment described above, an example was shown in which the pressure sensor 16 was installed downstream of the oil filter 13 in the oil supply system 10. However, the pressure sensor 16 may be configured to detect the pressure of the lubricating oil discharged from the pump 11 and flowing through the oil supply system 10. For example, the pressure sensor may be installed downstream of the oil cooler 12 and upstream of the oil filter 13 in the oil supply system 10 (not shown). Further, the pressure sensor may be installed upstream of the oil cooler 12 in the oil supply system 10 so as to detect the discharge pressure of the pump 11 (pressure sensor 16 indicated by a chain line in FIG. 1).

Further, in the embodiment described above, an example was shown in which the pressure threshold value Pth was a preset fixed value. However, it is also possible to set the pressure threshold value Pth based on the detected value of the pressure sensor 16 instead of setting it as a fixed value. Specifically, when the front compressor main body 2 and the rear compressor main body 3 (gas compressor 1) are stopped, the control device 40 controls the front compressor main body 2 and the latter compressor main body 3 (gas compressor 1). ) is configured to store in the storage device 41 the pressure value detected by the pressure sensor 16 in the normal operating state immediately before stopping. Further, the control device 40 is configured to set the pressure threshold Pth based on the pressure value of the pressure sensor 16 stored in the storage device 41. The pressure value detected by the pressure sensor 16 during normal operation of the gas compressor 1 is supplied from the pump 11 to the front compressor body 2 and the rear compressor body 3 when the electric motor 4 is at the maximum speed or rated speed. Indicates the pressure of lubricating oil (oil). That is, the pressure value can be used as an index for determining the maximum speed or rated speed of the electric motor 4. According to this configuration, unlike the case where the pressure threshold value Pth is a fixed value, there is no need to consider pressure loss of the oil cooler 12 and the oil filter 13.

1...Gas compressor, 2...Pre-stage compressor main body (compressor main body), 3...Post-stage compressor main body (compressor main body), 4...Electric motor, 10...Oil supply system, 11...Pump, 12...Oil cooler (heat exchanger), 13...Oil filter (filter), 16...Pressure sensor, 31...Starting device, 40...Control device, Pth...Pressure threshold value

Claims (4)

A compressor body that compresses gas;
an electric motor that drives the compressor main body;
an oil supply system including a pump mechanically connected to and driven by the electric motor and supplying oil discharged from the pump to the compressor main body;
a pressure sensor that detects the pressure of oil flowing through the oil supply system;
a starting device that is electrically connected to the electric motor and has an electric circuit that can switch the connection state of the windings of the electric motor between a first connection that is a star connection and a second connection that is a delta connection;
and a control device that controls connection of the electric circuit of the starting device,
The control device includes:
When starting the compressor main body is started, the electric circuit of the starting device is connected to the first connection,
performing a switching determination to determine whether a pressure value detected by the pressure sensor during startup of the compressor main body is equal to or higher than a pressure threshold;
The electric circuit of the starting device is configured to be switched from the first connection to the second connection when it is determined in the switching determination that the pressure value detected by the pressure sensor is equal to or higher than the pressure threshold value. A gas compressor characterized by: The gas compressor according to claim 1,
The gas compressor, wherein the pressure threshold is a preset fixed value and is stored in the control device in advance. The gas compressor according to claim 1,
The control device is configured to store, when the compressor main body is stopped, a pressure value detected by the pressure sensor in a normal operating state immediately before stopping the compressor main body,
The gas compressor, wherein the control device sets the pressure threshold value based on a stored pressure value in the switching determination. The gas compressor according to claim 1,
In addition to the pump, the oil supply system includes a heat exchanger that cools oil supplied from the pump to the compressor body, and a filter that filters impurities in the oil supplied from the pump to the compressor body. including,
The gas compressor, wherein the pressure sensor is installed downstream of the heat exchanger and the filter in the oil supply system.

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