JPS58117373A - Apparatus for controlling numbers of operated compressors - Google Patents

Abstract

PURPOSE:To lower the power consumption of a compressor system and to prolong the service life of compressors, by providing a means for determining the effect waiting time by operating compressors on the basis of the number of actually operated compressors in an apparatus for controlling the number of operated compressors which controls starting and stopping operation of a plurality of compressors connected in parallel with each other. CONSTITUTION:In parallel operation of a multiplicity of compressors, the characteristics of operation differs from that in case of operating a small number of compressors. For instance, in case of stopping and starting operation of compressors in a predetermined sequence in response to the load change, the time required for the discharge pressure is lowered to a preset starting pressure from the time when a stop instruction is given is Ta when many compressors are operated. However, when the number of operated compressors is small, the time is shortened to Tb, as shown in the drawing. The above control can be achieved effectively by predetermining the relationship between the number of operated compressors and the stop-effect waiting time and putting it into a control means. Such an effect waiting control can be executed for stopping, starting, unloading, loading, etc. of the compressors.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compressor number control device that starts and stops a plurality of compressors in a predetermined order.

In conventional compressor number control, when starting and stopping compressors in sequence, an effect waiting time is set according to operations such as starting, stopping, or capacity control by the compressor in operation, and the waiting time for these effects is set. The next start/stop command or capacity control command is given only after a certain amount of time has elapsed.

This reduces power consumption due to unnecessary compressor operation,
This prevents clumsy start/stop operations and suppression of fluctuations in discharge pressure. However, these effect waiting times are fixed values regardless of the number of compressors in operation. Therefore, there was a problem that it was unreasonable from the viewpoint of power reduction.

The present invention has been made to eliminate the above-mentioned drawbacks, and aims to save power and prevent frequent starting and stopping operations.

The present invention is characterized by a compressor number control device that arranges a plurality of compressors in parallel and sequentially starts and stops the plurality of compressors according to the load, based on the current number of operating units. Means is provided for determining the effective waiting time due to the operating compressor.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing the configuration of a compressor equipped with an example of the number control device of the present invention. In the figure, eight compressors 0
A case will be explained taking as an example a case where 1 to C8 are operated in parallel. Compressed air from these compressors 01 to C8 is collected in the main pipe 2 and sent to a plant serving as a load. The usage amount of this load is determined by the pressure switch 3 as the discharge pressure in the main pipe 2.
Detected by Based on this detection signal, the unit-based system 4 controls each control panel 81 to S8 to start, stop, and control the capacity of the compressors C1 to C8 in a fixed order.
Outputs start, stop commands, and capacity control commands to the In addition, the number control device 4 controls the starting, stopping, and capacity side of the compressors 01 to C8. 14I C Onload, Unload) commands are stored with effect waiting times as shown in Table 1, and the next command is given only after these times have elapsed. ing.

Table 1 and Figure 2 show the relationship between the change in discharge pressure and the effect waiting time when the compressor is stopped.

The upper characteristic in Figure 2 shows that when eight compressors are in operation, the load usage decreases, the discharge pressure reaches the stop pressure set value, and the number control device 4 issues a stop command to one compressor. This is the case when it is output. In addition, the lower characteristic in Fig. 2 shows that when two compressors are operating, the load usage decreases, the discharge pressure reaches the stop pressure set value, and the number controller 4 outputs one compressor. This is the case when a stop command is output.

As is clear from Fig. 1, when eight compressors 01 to C8 are in operation and when only two compressors are in operation,
There are differences in the capacity of compressors and piping.

Furthermore, there are also differences in the changes in the output characteristics of the compressors themselves during operation and the degree of mutual influence. For this reason, the effect of stopping one unit should be manifested in different ways as changes in physical discharge pressure. For example, in the case of the upper characteristic in Figure 2, the degree of decrease in rJ:i and pressure force is gradual, and in the case of the lower characteristic in Figure 2, the degree of decrease in discharge pressure is gradual. There is a strong possibility that it will become. Therefore, when the stopping effect waiting time T is fixed regardless of conditions as in the conventional system, a problem arises as to which standard should be used to determine the stopping effect waiting time T. For example, the upper part of Figure 2
If we decide based on the case of sex, then the lower part of Figure 2 (1
! In the case of the characteristic l, it may be too long. That is, there is a possibility that the discharge pressure will decrease before the effect waiting time elapses, and the additional activation will be delayed and the discharge pressure will fluctuate. On the other hand, 111 at the bottom of Figure 2! If we decide based on the case of l'1M property, ±111! in Figure 2! In the case of characteristics I, it may be too short. In other words, since the necessary effect waiting time has not elapsed, there is a risk that the determination of the number-of-units control operation to be performed next may become inappropriate.

As the above examples show, it is inconvenient to fix the effect waiting time as shown in Table 1 regardless of the operating conditions from the viewpoint of saving power, frequency of start/stop operations, and fluctuations in discharge pressure. It is. For this reason, in the case of "Hon-Issu", the unit-based system 4 has a function of making the effect waiting time variable depending on the number of units in operation. FIG. 3 is an example of a method for determining the above-mentioned stopping effect waiting time. In this example, the stop effect waiting time is increased as the number of vehicles in operation increases. That is, when the number of operating vehicles is 8, the rj1 effect time is set to Ta, and when the number of operating vehicles is 2, the effect waiting time is set to Tb. When this is plotted on the time axis of FIG. 2, it can be seen that it can be determined appropriately in response to changes in the discharge pressure.

It should be noted that the number control device 4 shown in FIG. 1 has conventionally been constructed from a relay case. :, so it is difficult to provide the above function, but if this is configured using a microcomputer etc., the effect waiting time can be changed to EiJ relatively easily. FIG. 4 shows a flowchart in this case. The characteristics shown in FIG. 3 described above can be easily stored in advance in the form of formulas or tables, and read out as needed.

In the above embodiment, the case where the stopping effect waiting time is made variable is illustrated, but the other effect waiting times shown in Table 1 can be similarly made variable.

As described in detail above, according to the present invention, the necessary effect waiting time can be determined based on the current number of operating units, so power consumption due to unnecessary compressor operation and frequent startup/stopping can be avoided. It is possible to shorten the lifespan due to operation and suppress the adverse effects on the plant due to fluctuations in discharge pressure.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing the configuration of a compressor equipped with an example of the number system system a of the present invention, FIG. 2 is a diagram showing the fluctuation characteristics of discharge pressure due to the number system system, and FIG. Figure 3 is a graph representing the relationship for determining the stop effect latency stored in the inventive device; 01~C8...Compressor, 2...Main pipe, 3...Pressure switch ¥i 1 Figure penalty 2 Figure stopping force 1 Total -I++ Figure 3/23a s 67z i Number of punches (W) Fourth
Illustration procedure amendment (method) 1. Display of the incident 1982 Patent Application No. 126658 Bow 2, Name of the invention Compressor number control device 3, Person making the correction I411 '5101 Stock Co., Ltd. 11 [1 Manufacturing representative Table 6 Tama 1) Shigeru Katsu 4. Agent 7 Amendment 0 Contents As shown in the attached sheet (1) "This is a graph representing a relationship for the purpose of" in line 700 and 14 of the description is amended as follows. 4 is a flowchart illustrating the setting of the effect waiting time in an example of the device of the present invention.

Claims (1)

[Claims] In a compressor number control device that arranges multiple compressors in parallel and starts and stops the multiple compressors in sequence according to the load, the effective waiting time due to the compressors in operation based on the current number of operating compressors. A compressor number control device characterized by comprising means for determining the number of compressors.