JP5178011B2 - Compressor and control method of compressor - Google Patents

Description

The present invention relates to a technique for controlling the operation of the compressor and the compressor.

In a device including a compressor and having a rotating machine and a synchronous motor (hereinafter referred to as “motor”) in the configuration, when the motor is operated exceeding the rated value when the motor is controlled, The load protection device may detect an overload and stop the motor. However, depending on the device, it may not be desirable to stop the motor, and it may be necessary to prevent it from stopping if possible. Japanese Patent Application Laid-Open No. H10-228561 discloses a countermeasure for this.
JP-A-6-22577

  In Patent Document 1, “when the output torque of the motor detected based on the detected actual current from the actual current detecting means is equal to or higher than the rated torque, the output torque is integrated, and the integrated value is an acceleration prohibition set value. If the value exceeds the value, the target rotation speed output means is controlled so that the motor has a constant rotation speed.After that, when the integrated value decreases and falls below the reacceleration set value, the motor is reaccelerated. And a torque integrating means for controlling the target rotational speed output means ”, and by adopting such a configuration, the above-described stopping of the electric motor is avoided.

  By the way, what is disclosed in Patent Document 1 is described for a general electric motor control device. For example, in a compressor, an electric motor may stop due to an overload. In that case, it is known that the process may be stopped in the process at the time of starting the residual pressure of the compressor. Here, the above-mentioned residual pressure activation refers to an activation method in which restarting is performed even if residual pressure exists at the compressor outlet immediately after the compressor is stopped. If the compressor can be started by this residual pressure activation, conventionally, the inconvenience that the compressor could not be restarted only after waiting for several minutes is eliminated.

  In the residual pressure start-up, the load of the motor that drives the compressor is the sum of the “load of the compressor” for driving the compressor by the motor and the “acceleration torque” for accelerating the motor and the compressor. . When starting up the residual pressure, if the "compressor load" is large due to the residual pressure, the motor will be overloaded and the motor will step out, or the protective device will operate and the motor will stop. It was known that it was going to be a problem.

  About the load with respect to the electric motor at the time of the above-mentioned residual pressure starting, it changes in relation to the pressure in the process part of a compressor.

  In the residual pressure activation, the operation is performed with the suction throttle valve of the compressor closed. For this reason, the pressure on the suction side of the compressor is equal to the residual pressure and is higher than the atmospheric pressure. After the motor is started, when the suction side pressure falls below atmospheric pressure, the suction valve is opened to take in the atmosphere and the compression operation is continued. Before and after the period of opening the intake throttle valve, the “compressor load” is large, and if it exceeds the load that can be generated by the electric motor, step-out occurs. Therefore, in order to solve the step-out and stop of the motor at the time of starting the residual pressure, it is necessary to control the motor in consideration of these pressures. The control of the electric motor in consideration of the pressure and the like is not disclosed in Patent Document 1.

  In the present invention, a compressor control system, a motor control method, and a compressor control system, in which it is an object to solve the above-mentioned problems, and a more reliable compressor does not need to increase the capacity of the motor and the motor control device, and An object of the present invention is to provide an electric motor control method.

  In the residual pressure start-up, “acceleration required for accelerating the electric motor and the compressor by keeping the rotational speed output from the rotational speed command generator constant for a certain period after starting the compressor. "Torque" is reduced, and the load required for the motor is made equal to or less than the torque at which the motor steps out.

The compressor according to the present invention is driven by a synchronous motor and compresses air, a suction throttle valve that shuts off the suction side of the screw compressor when the screw compressor is stopped, and the synchronization at startup. Having a speed holding period for holding the rotational speed of the synchronous motor before reaching the target rotational speed of the motor, and rotating the rotational speed of the synchronous motor so as to accelerate the synchronous motor after the speed holding period is exceeded. And a motor control device that controls the speed and causes the synchronous motor to reach the target rotational speed.

Furthermore, the compressor according to the present invention is characterized in that acceleration of the synchronous motor is stopped during the speed holding period, and rotation control of a command value at a constant rotational speed is performed.

Furthermore, the compressor of the present invention includes a pressure sensor for measuring the pressure on the intake side of the screw compressor, and the electric motor control device has a pressure measured by the pressure sensor that is greater than atmospheric pressure in advance. The synchronous motor is accelerated when the pressure value is equal to or higher than a predetermined pressure value, and when the pressure measured by the pressure sensor is less than the pressure value, acceleration of the synchronous motor is stopped to enter the speed holding period, and the pressure sensor The suction throttle valve is opened when the pressure measured in step (b) is lower than atmospheric pressure.

Further, in the compressor according to the present invention, the motor control device accelerates the synchronous motor until the rotational speed command value reaches a predetermined rotational speed before reaching the target rotational speed, and the predetermined motor speed is determined in advance. When the rotation speed command value reaches a predetermined rotation speed, acceleration of the synchronous motor is stopped until a predetermined time set as a setting time for holding the rotation speed command is reached.

The compressor control method of the present invention includes a screw compressor that is driven by a synchronous motor and compresses air, and a suction throttle valve that shuts off a suction side of the screw compressor when the screw compressor is stopped. When the screw compressor is started up, the electric motor control device is configured so that the pressure on the intake side of the screw compressor measured by the pressure sensor is a value greater than atmospheric pressure in advance. The synchronous motor is accelerated when the pressure value is equal to or higher than a predetermined pressure value, and when the pressure on the intake side of the screw compressor measured by the pressure sensor is less than the pressure value, the synchronous motor is accelerated. It enters a speed holding period during which the synchronous motor is controlled to rotate at a constant rotational speed, and the pressure on the intake side of the screw compressor measured by the pressure sensor is less than atmospheric pressure. Characterized so that the opening the intake throttle valve.

  According to the present invention, it is possible to obtain a compressor control system in which a more reliable compressor does not increase the capacity of the electric motor and the electric motor control device.

The present invention includes a compressor having a valve at an air intake port, an electric motor that operates the compressor, and an electric motor control device that controls and drives the rotational speed of the electric motor, and the electric motor control device includes the compressor When the electric motor is started under a condition where the internal pressure is higher than atmospheric pressure, the rotational speed of the electric motor is set to a substantially constant value during a period when high motor torque is required until the valve of the air intake port is opened. It is a compressor control system that is held stably and does not step out.
In addition, the present invention is a compressor control system in which the electric motor control device maintains a rotational speed at a substantially constant value by using a rotational speed command value to the electric motor.
And this invention is an electric motor control apparatus which controls and drives the rotational speed of the electric motor which operates the compressor which has a valve in the air intake port, Comprising: Under the conditions where the pressure inside the said compressor is higher than atmospheric pressure When starting up the electric motor, during a period when a high motor torque is required until the valve of the air intake port is opened, the rotation speed of the electric motor is maintained at a substantially constant value and is stably performed without being stepped out. An electric motor control device.
Furthermore, the present invention is an electric motor control device that maintains a rotational speed at a substantially constant value by using a rotational speed command value to the electric motor.
The present invention also relates to an electric motor control method for controlling and driving the rotational speed of an electric motor that operates a compressor having a valve at an air intake port, wherein the internal pressure of the compressor is higher than atmospheric pressure. When starting the electric motor, a method for controlling the electric motor that stably maintains the rotational speed at a substantially constant value during a period in which a high motor torque is required until the valve of the air intake port is opened, and does not step out. It is.
Next, the best mode for carrying out the present invention will be described. An embodiment of the compressor control system, the motor control device, and the motor control method of the present invention will be described with reference to the drawings.

  Example 1 will be described. FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. Based on the command output from the voltage command calculation unit 20 and the AC power output from the PWM calculation unit 30 and the inverter unit 40 so that the rotation speed is output from the rotation speed command generator 10 of the motor control device. The electric motor 50 is driven, and the air is compressed by the screw compressor 60.

  The screw compressor 60 sucks the air taken in from the air filter 70 through the pipe 100 and discharges the compressed air. The suction throttle valve 80 is arranged in the middle of the pipe 100 and shuts off the atmosphere and the suction side of the compressor so that air does not flow backward when the compressor is stopped.

  The pressure sensor 90 is arranged in the middle of the pipe 100 and measures the pressure on the suction side of the compressor. Based on the information from the pressure sensor 90, the rotational speed command generator 10 determines the acceleration and constant speed period and commands the rotational speed of the electric motor 50.

  The control at the time of starting the residual pressure in the compressor rotation speed command generator 10 will be described with reference to the flowchart shown in FIG. In FIG. 2, when the residual pressure activation is started (step 200), the motor is first accelerated (step 210). When the suction side pressure of the compressor 60 measured by the pressure sensor 90 is equal to or greater than “atmospheric pressure + α” (step 220—NO), the process returns to step 210 to accelerate the motor. Here, α is a pressure with which a sufficient margin can be provided for the torque that can be output without the motor stepping out.

  When the suction side pressure of the compressor 60 measured by the pressure sensor 90 becomes less than “atmospheric pressure + α” (step 220—YES), the acceleration of the electric motor 50 is stopped and the rotation control is held at a constant speed A ( Step 230). Here, since the compressor 60 continues the compression operation, the suction-side pressure of the compressor 60 continues to decrease and becomes equal to or lower than the atmospheric pressure. When the pressure on the suction side of the compressor 60 is equal to or lower than the atmospheric pressure, the suction throttle valve 80 is opened. The constant speed A may be a substantially constant speed depending on the control method employed.

  Next, when the suction side pressure of the compressor 60 measured by the pressure sensor 90 is less than the “pressure in steady operation” (step 240 -NO), the process returns to step 230 to maintain the rotational speed A of the motor, Do not accelerate. When the suction side pressure of the compressor 60 measured by the pressure sensor 90 returns to the “pressure in steady operation” or more (step 240-YES), the motor is resumed (step 250), and reaches the target rotational speed. Acceleration is continued until (step 260-YES).

  A second embodiment will be described. FIG. 3 is a diagram for explaining the configuration of the second embodiment of the present invention. In the present embodiment, the pressure sensor 90 is removed from the configuration of the first embodiment (see FIG. 1). This configuration enables control without using pressure information on the suction side.

  The control at the time of the residual pressure starting in the rotational speed command creation device 10 of Example 2 is demonstrated using the flowchart shown in FIG. In FIG. 4, when the residual pressure activation is started (step 300), the motor is first accelerated (step 310). Then, instead of the suction side pressure in the first embodiment, the determination based on the rotational speed command is performed. If the rotational speed command value is less than “the rotational speed (frequency) at which rotational speed command holding is started” (step 320—NO), the process returns to step 310 to accelerate the motor. Here, “the number of rotations at which the rotation number command is held” is set in advance to the number of rotations (rotation speed) that can be accelerated without the motor stepping out.

  Next, when the rotational speed command value is equal to or greater than “the rotational speed at which the rotational speed command is held” (step 320—YES), the acceleration of the electric motor 50 is stopped and the rotational control is performed at a constant rotational speed A (step 330).

  Here, the elapsed time after maintaining the rotation speed is measured. If the elapsed time since the rotation speed is held is equal to or less than the “set time for holding the rotation speed command” (step 340—NO), the process returns to step 330 to hold the rotation speed command value A of the electric motor 50 and accelerate. Do not do. When the elapsed time since the rotation speed command is held exceeds the “set time for holding the rotation speed command” (step 340-YES), the acceleration of the electric motor 50 is restarted (step 350) and the target rotation speed is reached. Acceleration is continued until (step 360-YES). Here, it is assumed that the “set time for holding the rotational speed command” is obtained in advance by measuring and setting the time until the load becomes sufficiently small.

  FIG. 5 is a relationship diagram of the rotational speed N, motor torque τM, suction side pressure P1, and drive time t required for the compression operation of the compressor 60 in the present embodiment. When the residual pressure is high and this embodiment is not used, before and after the suction side pressure becomes equal to or lower than the atmospheric pressure, the limit value of the motor torque τM that the motor can output is exceeded, causing the motor to step out (dotted line) ). By using this embodiment, the front-rear rotational speed at which the suction side pressure is equal to or lower than the atmospheric pressure is kept constant, the torque corresponding to “acceleration torque” is reduced, and the limit value of the motor torque τM that can be output by the electric motor is reached. It can be started without causing any adjustment (solid line).

It is a figure which shows the structure of the electric motor control apparatus in Example 1. FIG. It is a flowchart figure of speed control of the electric motor control device in Example 1. It is a figure which shows the structure of the electric motor control apparatus in Example 2. FIG. It is a flowchart figure of speed control of the electric motor control apparatus in Example 2. FIG. It is a related figure of the suction side pressure in the compressor control system of an Example, and the torque required for compression operation.

Explanation of symbols

  10: Rotational speed command generator, 20: Voltage command calculation unit, 30: PWM calculation unit, 40: Inverter unit, 50: Electric motor, 60: Screw compressor, 70: Air filter, 80: Suction throttle valve, 90: Pressure sensor , 100: piping

Claims (5)

A screw compressor driven by a synchronous motor to compress air ;
A suction throttle valve that shuts off the suction side of the screw compressor when the screw compressor is stopped;
At the time of start-up, there is a speed holding period for holding the rotational speed of the synchronous motor before reaching the target rotational speed of the synchronous motor, and the synchronous motor is accelerated so as to accelerate after the speed holding period is exceeded. and controlling the rotational speed of the rotational speed of the electric motor, compressor, characterized in that said synchronous motor and a motor control device for reaching the target speed. The compressor according to claim 1 stops acceleration of the synchronous motor, characterized by rotation control and to Rukoto constant rotational speed command value in the velocity hold period. A pressure sensor for measuring the pressure on the intake side of the screw compressor;
The motor controller is
When the pressure measured by the pressure sensor is greater than atmospheric pressure and greater than or equal to a predetermined pressure value, the synchronous motor is accelerated.
When the pressure measured by the pressure sensor is less than the pressure value, the acceleration of the synchronous motor is stopped to enter the speed holding period, and the suction throttle valve is turned on when the pressure measured by the pressure sensor is lower than the atmospheric pressure. The compressor according to claim 1, wherein the compressor is opened . The motor controller is
Accelerate the synchronous motor until the rotational speed command value reaches a predetermined rotational speed before reaching the target rotational speed,
When the rotation speed command value to the rotational speed of said predetermined reaches, claims, characterized that you stop the acceleration of the synchronous motor until a predetermined set time as the set time for the rotational speed command holding The compressor according to 1 . A screw compressor driven by a synchronous motor to compress air;
A compressor control method comprising a suction throttle valve that shuts off a suction side of the screw compressor when the screw compressor is stopped ,
At the time of starting the screw compressor, the electric motor control device determines that the pressure on the intake side of the screw compressor measured by the pressure sensor is greater than atmospheric pressure and is equal to or greater than a predetermined pressure value. Accelerating the synchronous motor,
When the pressure on the intake side of the screw compressor measured by the pressure sensor is less than the pressure value, the acceleration of the synchronous motor is stopped and the synchronous motor is controlled to rotate at a constant rotational speed. The compressor control method according to claim 1, wherein the suction throttle valve is opened when a pressure on the intake side of the screw compressor measured by the pressure sensor becomes equal to or lower than an atmospheric pressure during a holding period .

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