JPH02208451A - Refrigerating cycle device - Google Patents

Abstract

PURPOSE:To reduce a refrigerating capacity and minimize fluctuation in electric energy by controlling properly an operation frequency of an inverter-driven first compressor before starting of stopping a second compressor which receives the supply of electric power from a commercial power source. CONSTITUTION:A control means 20 compares a load read from a load detector 21 with a preset value and properly controls the operation frequency of an inverter 11 in proportion to its deviation, performing property ON/OFF control of a power supply switch 22, then controlling a refrigerating capacity of its entire refrigerating cycle device under start and stop control of a second compressor 14. In this case, the control means 20, when it is necessary to starts the compressor 14 as a result of its increased load during the operation of a first compressor 12, reduces compulsorily the operation frequency of the inverter 11 to a specified low level of preset frequency for a specified time prior to its starting and raises compulsorily the operation frequency of the inverter 11 to a specified high level of preset frequency for a specified time prior to its shut down when it is necessary to stop the operation of the compressor 14 during the combined operation of the bath compressors 12 and 14.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention enables the combined operation of a variable-capacity compressor driven by an inverter and a constant-capacity compressor supplied with power from a commercial power source. The present invention relates to a refrigeration cycle device installed in the United States, and particularly to a refrigeration cycle device with improved control means for controlling the operation of these compressors.

(Prior Art) Conventionally, there is a refrigeration cycle device of this type configured as shown in FIG.
A second compressor 4 with a constant capacity, which is supplied with power from a commercial power supply 3, is connected in parallel with a refrigerant pipe 5, and an evaporator 6, an expansion mechanism 7, and a capacitor 8 are connected in this order through the refrigerant pipe to this parallel circuit. They are connected in an annular manner to form a diagonal leap loop that circulates the refrigerant.

The compressor control means 8 then controls the inverter 1 according to the deviation between the load read from the load detector 9 and the set value.
At the same time as controlling the operating frequency output from the second compressor 4, the power switch 10 of the second compressor 4 is opened.
! 11, the capacity of the first compressor 2 is controlled, and the second compressor +j4(1)ON-
(Problems to be Solved by the Invention) However, such conventional refrigeration cycle devices have problems in that the energy saving effect is low and the refrigeration cycle is unstable.

When the second compressor 4j4 is turned on by the compressor control means 8 due to an increase in load while the first compressor 2 is in operation, the refrigerating capacity changes to the load shown by the solid line in the figure as shown in ff14 (A). This causes an overshoot O to occur, and also produces a steep peak Pb in the amount of power as shown in FIG. 4<8).

On the other hand, when the operation of the second compressor 4 is stopped by the compressor control means 8 to reduce the load while the first compressor 2 and the second compressor 4 are being operated together, the state shown in FIG. 4(A) occurs. As shown, an undershoot U occurs in the refrigeration capacity, and a steep decrease pu occurs in the electric power l.

Therefore, in such a conventional example, when the second compressor 14 is turned on and off (ON-OFF), the refrigeration capacity changes rapidly, making the refrigeration cycle unstable, and the amount of electricity changes rapidly, reducing the energy-saving effect. There is an issue of low performance.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a refrigeration cycle device that can both improve energy saving effects and stabilize the refrigeration cycle.

[Structure of the invention]

(Means for Solving the Problems) The present invention is designed to prevent the refrigeration capacity and electric energy from changing when the second compressor is turned on and off (ON-OFF), which is supplied with power from a commercial power source. By appropriately controlling the operating frequency of the first compressor 2 driven by an inverter, fluctuations in refrigeration capacity and electric energy are reduced.

That is, the present invention provides a refrigeration cycle device in which a first compressor that is operated with variable capacity depending on the operating frequency output from an inverter and a second compressor that is supplied with power from a commercial power source can be operated in combination. Before starting the second compressor,
The operating frequency from the inverter is forcibly lowered to a set frequency lower than its maximum frequency for a required period of time, and when the operation of the second compressor is stopped, the operating frequency from the inverter is reduced before the operation is stopped. The present invention is characterized in that $q control means is provided for controlling the frequency to be forcibly raised to a set frequency higher than the lowest frequency for the required time.

(Function) When starting the second compressor while the first compressor is operating in response to an increase in load, before starting the second compressor, the operating frequency output from the inverter is changed by the 61111 means.
The frequency is controlled to be forcibly lowered to a set frequency lower than the maximum frequency of the inverter for the required time.

Therefore, when the second compressor is started, the refrigeration capacity and electric energy of the first compressor have already been reduced, and this reduction reduces the increase in the refrigeration capacity and electric energy when the second compressor is started. This makes it possible to reduce rapid fluctuations in the refrigeration capacity and electric energy of the refrigeration cycle as a whole.

Furthermore, when a load decrease occurs during the combined operation of the first and second compressors and the operation of the second compressor is stopped, the control means adjusts the operating frequency from the inverter to a level lower than the lowest frequency of the inverter before stopping the operation of the second compressor. It is controlled to forcibly raise the frequency to a required high setting frequency for a required period of time.

Therefore, when the operation of the second compressor is stopped, the power capacity and refrigeration capacity of the first compressor have already been increased. It is possible to reduce the slump, and it is possible to reduce rapid fluctuations in the refrigeration capacity and electric energy of the entire refrigeration cycle device.

As a result, according to the present invention, the second compressor starts and stops (
It is possible to reduce power consumption and rapid fluctuations in refrigeration capacity during ON-OFF>, thereby achieving both improved energy saving effects and stabilization of the refrigeration cycle.

(Example) An example of the present invention will be described below based on FIGS. 1 to 3.

FIG. 1 is an overall configuration diagram of an embodiment of the present invention. In the figure, a first compressor 12 with a variable capacity driven by an inverter 11, and a second compressor 12 with a constant capacity supplied with power from a commercial power source 13 are shown. The suction ports and the discharge ports of the compressors 14 are connected in parallel by parallel piping 15.

An evaporator 17, an expansion mechanism 18, and a condenser 19 are sequentially and annularly connected to the parallel pipe 15 via a refrigerant pipe 16 to form a closed refrigeration cycle in which the refrigerant is circulated.

The control means 20 is connected to the inverter 11 via a signal line indicated by a broken line in the figure, a load detector 21 attached to the evaporator 17 to detect the load thereof, a commercial power source 13, and a second compressor 14 (not shown). They are each electrically connected to a power switch 22 interposed in a power supply line connecting the power supply terminals.

The inverter 11 receives power from a commercial power source 13, converts the power frequency to a required operating frequency, supplies it to the first compressor 12, controls its rotation speed, and thereby controls its compression capacity. This inverter 11
The operating frequency output from the control means 2o is appropriately controlled.

That is, the control means 20 compares the load read from the load detector 21 with a set value, and according to the Va difference, appropriately controls the operating frequency of the inverter 11, and also controls the power switch 22 to turn on and off as appropriate. According to the second
The compressor 14 is turned on and off to control the refrigeration capacity of the entire refrigeration cycle apparatus.

In addition, when performing load following operation for the load fluctuation shown in FIG. 2(A), for example, the control means 20 appropriately controls the operating frequency of the inverter 11 to
2, and controls the compression capacity of the second compressor 1.
It is designed to control the start and stop of 4.

Moreover, as shown in FIG. 2(B), the control means 20 controls the operation of the second compressor 1 while the first compressor 12 is in operation.
4, the operating frequency of the inverter 11 is forcibly lowered to the required low set frequency f1 for the required time, while the first and second compressors 12.1
4, when the operation of the second compressor 14 is stopped, the operating frequency of the inverter 11 is controlled to be forcibly increased to the required high setting frequency fh for the required time before the operation is stopped. It looks like this.

That is, the control means 20 controls the first and second compressors 12 and 14 according to the control program shown in FIG. 3, in which P1 to P14 indicate each step of the flowchart. .

That is, the control means 20 reads the load from the load detector 21 at Pl, compares it with the set value, determines whether the load is increasing at P2, and if YES, goes to P3, and if No, goes to P4. Proceed each.

In P3, the operating frequency of the inverter 11 is increased to a higher required operating frequency corresponding to the load increase, and in P5, it is determined whether this operating frequency has reached the maximum frequency, and YES is determined.
If so, proceed to P6.

In P6, it is further determined whether or not the second compressor 14 is in operation, and if NO, the operating frequency of the inverter 11 is lowered to a required low setting frequency in Pl, and then, in P8, the second compressor 14 is in operation. The compressor 14 is started.

Therefore, when starting the second compressor 14 due to an increase in load, the operating frequency of the inverter 11 is lowered to the low set value fo, which is lower than the R high frequency, and the first compressor 12 is activated. Since the power capacity ω and the refrigeration capacity of the second compressor 14 are lowered in advance, it is possible to reduce the increase in the power capacity and the refrigeration capacity when the second compressor 14 is started.

On the other hand, if a load reduction occurs in P4, the operating frequency of the inverter 11 is lowered in P9, and the compression capacity of the first compressor 12 is reduced in accordance with the load reduction.

Furthermore, the PIO determines whether the operating frequency of this inverter 11 has reached the lowest frequency, and if YES,
At P11, it is determined whether or not the second compressor 14 is in operation, and if the answer is No, at P12, the operation of the first compressor 12 is stopped.

On the other hand, when the second compressor 14 is in operation, the operating frequency of the inverter is increased to a high set value fh higher than its lowest frequency at Pl3, and then Pl4
The operation of the second compressor 14 is stopped at Pl.
Go back and repeat this.

Therefore, when stopping the operation of the second compressor 14, the operating frequency of the inverter 11 is increased to a high set value beforehand, and the operation frequency of the first compressor 12 is increased.
Since the power capacity and refrigeration capacity of the second
It is possible to reduce the drop in power capacity and refrigeration capacity when the compressor 14 is stopped.

Next, the operation of this embodiment will be described in the case where load follow-up operation is performed in response to refrigeration load fluctuations as shown in FIG. 2(A).

First, when the load gradually increases from a low load as shown in FIG.
tIIl and load following operation is performed.

If the load increase exceeds the maximum operating frequency of the inverter 11, it will be necessary to start the second compressor 14, but before that, the operating frequency of the inverter 11 must be increased as shown in FIG. The second compressor 14 is activated after having previously lowered the frequency fJ to the required low setting frequency fJ.

Therefore, before starting the second compressor 14, the operating frequency of the inverter 11 is lowered to the required low setting frequency fI, so that the power capacity and refrigeration Rapid increases in capacity can be absorbed and reduced, and rapid fluctuations in power capacity and refrigeration capacity can be reduced.

On the other hand, the load gradually decreases, and the load decrease causes the inverter 1 to
When the lowest frequency of 1 is reached, it is necessary to stop the operation of the second compressor 14, but instead of starting the second compressor 14 immediately, the inverter 11
The operating frequency of is controlled to the set frequency fh, and the power capacity and refrigeration capacity are increased in advance.

Due to this attack, the operation of the second compressor 14 is stopped, and at that time, the power capacity and refrigeration capacity are rapidly reduced, but this decrease is almost offset by the power capacity and refrigeration capacity of the first compressor, which have been increased in advance. Therefore, sudden fluctuations in power capacity and refrigeration capacity can be prevented.

As a result, according to this embodiment, the second compressor 14
Since it is possible to reduce rapid fluctuations in power capacity and refrigeration capacity when turning on and off (ON-OFF), it is possible to improve energy saving effects and stabilize the refrigeration cycle.

〔Effect of the invention〕

As explained above, the present invention reduces the rapid fluctuations in power capacity and refrigeration capacity when the second compressor starts and stops by almost offsetting them with the fluctuations in the power capacity and refrigeration capacity of the first compressor. Therefore, rapid fluctuations in power capacity and refrigeration capacity when the second compressor starts and stops can be reduced, and it is possible to improve the energy saving effect and stabilize the refrigeration cycle.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a refrigeration cycle device according to the present invention,
Figure 2 (A) is a graph showing refrigeration load and capacity fluctuation;
Fig. 2 (B) is a graph showing the control method of the control means shown in Fig. 1 in the case of load following operation for the load fluctuation shown in <A), and Fig. 3 is a graph showing the control method of the control means shown in Fig. 1. Flowchart of built-in control program, Fig. 4 (A), (B)
5 is a graph showing the fluctuations in the refrigeration container and electric power capacity during operation in the conventional example, and FIG. 5 is a configuration diagram of the conventional refrigeration cycle device. DESCRIPTION OF SYMBOLS 11... Inverter, 12... First compressor, 13... Commercial power supply, 14... Second compressor, 17... Evaporator, 19... Capacitor, 2
0...t, lJ 111 means. Applicant's agent Hisashi Hatano T (1119 hours) T (time) Figure 1 T (epJFJ'1) T (hour) No. 4

Claims (1)

[Claims] A refrigeration cycle device in which a first compressor that is operated with variable capacity according to the operating frequency output from an inverter and a second compressor that is supplied with power from a commercial power source can be operated together. When starting, the operating frequency from the inverter is forcibly lowered to a set frequency lower than the maximum frequency for a required time before starting, and when stopping the operation of the second compressor, before starting,
A refrigeration cycle device characterized in that a control means is provided for controlling the operating frequency from the inverter to forcibly increase it to a set frequency higher than the lowest frequency for a required period of time.