JPS58131385A - Controller for number of compressors operated - Google Patents

Abstract

PURPOSE:To enable to achieve a predetermined discharge pressure with the minimum quantity of energy, by a method wherein a controlling action at the current time point is determined by selecting from a predetermined control table on the basis of the contents of a controlling action at the preceding time point and the discharge pressure at the current time point. CONSTITUTION:The controller 9 for the number of compressors operating has such a function that a signals for sequentially starting or stopping four compressors 1a-1d, a signal for causing one of the compressors to perform a capacity-controlled operation and a signal for causing a required number of the compressors to perform full-load operation are outputted to control panels 3a-3d so that the discharge pressure satisfy a preset value, based on the detection signal from a pressure detector 6. Determination of the controlling action can be easily conducted by referring to a predetermined specific table. Accordingly, since the controlling action at the current time point is determined on the basis of the controlling action at the preceding time point and the discharge pressure at the current time point, starting and stopping of the compressors and control of capacity can be performed in a fine manner in accordance with variations in load, and unnecessary energy consumption is saved and the useful life of the apparatus is prolonged.

Description

[Detailed description of the invention] The present invention relates to a compressor number control device.

Generally, the number of compressors is controlled by detecting the usage amount as discharge pressure with a pressure detector, and starting and stopping the compressors from a control panel according to the detected usage amount. FIG. 1 shows a conventional number control block diagram. In FIG. 1, Ia to Id are compressors, 28 to 2d are electric motors, 3a to 3d are control panels, and 4a to 4d are each compressor 1.
This is a pressure detector for capacity control for a to 1d. 5Fi
This is a discharge pipe that combines the discharged air from these four compressors 1a to 1d and sends it out to the plant. This discharge pipe 5 is provided with a pressure detector 6 for controlling the number of units for detecting the pressure of the discharged air.

7 is a number control device which starts four compressors 18 to ld one after another based on the detection signal of the pressure detector 6 so that the discharge pressure of the discharge pipe 5 exceeds the set value 11:@ .

Then, one compressor is operated under capacity control, and the necessary number of compressors among the four compressors are operated at full load. Capacity control operation of the compressor is performed by each control panel 38.
This is done by commands 8a to 8d from 3d.

FIG. 2 shows the relationship between the set value of the pressure detector for controlling the number of compressors and the control operation of the compressor. The set value of the discharge pressure is divided into five regions as shown in this figure. The control operation is determined by detecting the force 1 where the discharge pressure of each compressor 1a-,=ld is in this region using a plurality of pressure detectors 6.

In the number control device shown in FIGS. 1 and 2 described above,
The current control operation is uniquely determined by the current state of the discharge pressure, regardless of past changes in the discharge pressure. For this reason, it does not take into account the effect of changes in the discharge pressure due to control operations in the past, especially at the previous point in time. Exactly the same control operation will be performed when that pressure is reached. Therefore, unnecessary starting and stopping operations are performed, resulting in wasted energy consumption and shortened machine life.

The present invention has been devised to solve these problems, and is capable of achieving a predetermined discharge pressure with the least amount of energy.

The present invention is characterized by sequentially starting and stopping a plurality of compressors so that the discharge pressure reaches a predetermined value, and by operating one compressor under capacity control while controlling the other necessary number of compressors. In controlling the number of compressors operating at full load, the current control operation is selected from a predetermined control table based on the contents of the control operation one point before and the current discharge pressure. It is.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to the drawings.

FIG. 3 is a block diagram showing a system for controlling the number of devices equipped with an example of the device for controlling the number of devices according to the present invention. In Figure 3, the first
Components with the same reference numerals as those in the figure are the same parts. In the present invention, based on the detection signal of the number control device 9Fi pressure detector 6, the four compressors 1a-
1d'1ll The control panel sends a signal to start and stop the primary, a signal to cause one compressor to perform capacity control operation, and a signal to cause the required number of compressors among the four compressors 13 to 1d to operate at full load. It has the function of outputting to 38 to 3d.

The control operation of this number control device 9 will be explained using FIGS. 4 and 5. Conventionally, the control operation was determined by inputting the detection signal of the pressure detector 6 and comparing this input signal with the control details shown in FIG.
The control operation is determined by the method shown in the figure. That is, the time for the control operation is set relative to time, and the current control operation is determined based on the control operation one time before and the current discharge pressure. The determination of this control operation can be realized by various methods, but it is simple and effective to refer to the following Table 1, which is predetermined, so this method will be described in this embodiment.

Each control operation in Table 1 will be explained. In this table, global unload immediately unloads all operating compressors. In the additional stop, one compressor in operation is stopped, and the compressor (hereinafter referred to as a capacity machine) whose total amount is controlled by the compressor in operation is unloaded. The conditioning machine a/load is
Take the machine from on-load to unload or keep it unloaded. To turn the container on-load, change the container from unload to on-load, or cross over and keep it in the on-load state. Additional startup starts one stopped compressor and onloads the filling machine. In emergency activation, additional activation is performed at short time intervals.

For example, the current discharge pressure setting range POL
- When the range is PUII, if the previous control operations were all unloading, additional activation, and onloading of the filling machine, the filling machine is on-loaded. Also, the previous control operation unloads the filling machine.

FIG. 5 is a flowchart illustrating the control operation of an example of the control device of the present invention. Enter the power you memorized,
Compare these and the 19th. From this, the current control operation is determined. Generally, the effect of a control action does not appear in the discharge pressure immediately after the control action is performed, so a waiting time is set apart from the time of the control action until the next control action is performed. It is preferable not to perform any control operation even if the condition occurs.

As explained above, according to the present invention, the current control operation is determined based on the previous control operation and the current discharge pressure, so the compressor is started frequently in response to changes in load. Stopping and capacity control can be performed. Therefore, not only unnecessary energy consumption can be saved, but also unnecessary starting/stopping of the compressor and capacity control operations can be avoided, so that the influence on the life of the mechanical parts can be reduced.

[Brief explanation of drawings]

Figure 1 is a control system diagram for conventional control of the number of compressors.
FIG. 2 is an explanatory diagram showing the relationship between the set value of the pressure detector for controlling the number of units used in the conventional control method and the control operation of the compressor, and FIG. FIG. 4 is a time chart for explaining the control method of the present invention, and FIG. 5 is a flow chart for explaining the control operation of the present invention. 18-1d... Compressor, 2a-2d... Electric motor, 3
a to 3d... Control panel, 4a to 4d... Pressure detector for capacity control, 5... Discharge pipe, 6... Pressure detector for number control, 9... Number control device. Shoulder 1 Figure VZ Illustration 4 Figure No.-M・

Claims (1)

[Claims] 1. Compression in which several compressors are started and stopped in sequence so that the discharge pressure reaches a predetermined value, and one compressor is operated with capacity control, while the other required number of compressors are operated at full load. In controlling the number of machines, a control unit that selects and determines the current control operation from a predetermined control table based on the content of the control operation one time before and the current discharge pressure, and outputs this control operation command. A compressor number control device characterized by comprising: