EP1956306A2

EP1956306A2 - Multi-system air-conditioner and method for controlling the same

Info

Publication number: EP1956306A2
Application number: EP07120691A
Authority: EP
Inventors: Kwang Il No. 512-1105 Sinnamusil-5th Apt. Nam; Byoung Guk No. 504-1002 Jugong-greenvill Apt. 1282 Lim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2007-02-06
Filing date: 2007-11-14
Publication date: 2008-08-13
Anticipated expiration: 2027-11-14
Also published as: KR101151321B1; KR20080073602A; EP1956306A3; EP1956306B1; CN101240933B; CN101240933A

Abstract

A multi-system air-conditioner for limiting a frequency-rising width of a compressor according to the air-volume of the indoor units, and enabling the indoor units to discharge the most comfortable-temperature air irrespective of the setup air-volume of the indoor units. The multi-system air-conditioner includes an outdoor unit, a plurality of indoor units connected to the outdoor unit, and a compressor for varying its own frequency according to operation capacity of the indoor units. The method for operating the multi-system air-conditioner includes: comparing, by each of the indoor units, a setup temperature with a room temperature, and calculating a capacity required for each indoor unit; calculating the sum of all the required capacities of the indoor units to calculate a combination ratio of all the operating indoor units; and comparing the calculated combination ratio with a reference combination ratio to determine whether the combination ratio of the indoor units is equal to or less than the reference combination ratio, limiting a frequency-rising width of the compressor to a predetermined value according to air-volumes of the operating indoor units when the calculated combination ratio is equal to or less than the reference combination ratio, and operating the air-conditioner at the limited value.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multi-system air-conditioner for connecting a plurality of indoor units to a single outdoor unit, and more particularly to a multi-system air-conditioner for actively controlling a frequency of a compressor so that the indoor units can discharge the air of a predetermined temperature although the air volume is changed to another, and a method for controlling the same.

2. Description of the Related Art

Generally, an air-conditioner has been widely used to reduce or increase a room temperature, and uses a general cooling cycle for circulating a refrigerant between the indoor and outdoor units. Therefore, the air-conditioner absorbs heat of a room when a liquid refrigerant is evaporated, and emits the heat when the refrigerant is liquefied, so that the cooling or heating operation can be carried out.
A general air-conditioner includes a single outdoor unit and a single indoor unit connected to the single outdoor unit. Recently, the number of users who desire to use a multi-system air-conditioner is rapidly increasing. The multi-system air-conditioner connects a plurality of indoor units to a single outdoor unit, so that the indoor units perform the cooling or heating operation independent of each other.
Since the multi-system air-conditioner connects the indoor units to only one outdoor unit, the operation capacity of the indoor units may be higher or less than that of the outdoor unit. Considering this situation, the multi-system air-conditioner uses an inverter compressor. Each indoor unit compares a room temperature with a reference temperature (or a preset temperature), and calculates a proper cooling/heating capacity using the required capacity of the corresponding indoor unit to decide a combination ratio of indoor-unit capacity (i.e., the agreement ratio of outdoor-unit capacity to indoor-unit capacity) as shown in FIG. 1, so that it changes a frequency within a predetermined range.
Referring to FIG. 1, if the indoor-unit combination ratio (%) is equal to or less than a maximum operation capacity of 130%, a frequency of the compressor is changed between a minimum cooling capacity and a maximum cooling capacity. If the indoor-unit combination ratio (%) is higher than the maximum operation capacity of 130%, the frequency of the compressor is fixed to a maximum frequency.
A frequency-rising limitation value of the compressor frequency shown in FIG. 1 is fixed to a maximum frequency in most cases excepting some cases (e.g., a case for protecting a system, and a frequency-rising limitation case for maintaining/decreasing a frequency according to operation modes), so that the compressor frequency is fixed to the maximum frequency and the compressor is operated at the maximum frequency.
However, the conventional air-conditioner aims to drop only the room temperature, but the recently-developed air-conditioner considers a noise of the indoor units to be the important factor for allowing a user to select a corresponding product. In the case of using the recently-developed air-conditioner, if the user sets the air volume of each indoor unit to a weak air-volume mode to decrease the noise of the indoor unit, the RPM of a fan motor of the indoor unit is decreased. However, the conventional multi-system air-conditioner has the same frequency limitation value at the strong and weak air-volume modes, irrespective of the air volume of the indoor unit. Therefore, the temperature of the air discharged from the indoor unit at the strong air-volume mode is lower than that of the weak air-volume mode as shown in FIG. 1, so that the user may feel the cold. And, if the temperature of the air discharged from the indoor unit is excessively decreased, the condensed water may be scattered all around.
Indeed, if the most comfortable room-temperature of the user is statistically calculated in all the air-conditioners, a duct- or roof- airconditioner provides the user with the most comfortable room-temperature of about 16°C, a wall- or stand- air-conditioner provides the user with the most comfortable room-temperature of about 14°C. However, the above-mentioned conventional multi-system air-conditioner controls the compressor frequency irrespective of the air volume of the indoor units, so that the temperature of the air discharged from the indoor units drops to about 11°C~12°C at which the user may feel the cold.

SUMMARY OF THE INVENTION

Therefore, it is an aspect of the invention to provide a multi-system air-conditioner for limiting the range of increasing the compressor frequency according to air-volumes of the indoor units, so that it allows the indoor units to discharge the air of a predetermined temperature most comfortable for the user even when the user changes a setup air-volume to another air-volume, and a method for controlling the same.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In accordance with the invention, the above and/or other aspects can be achieved by the provision of a method for operating a multi-system air-conditioner which includes an outdoor unit, a plurality of indoor units connected to the outdoor unit, and a compressor for varying its own frequency according to operation capacity of the indoor units, the method comprising: comparing, by each of the indoor units, a setup temperature with a room temperature, and calculating a capacity required for each indoor unit; calculating the sum of all the required capacities of the indoor units to calculate a combination ratio of all the operating indoor units; and comparing the calculated combination ratio with a reference combination ratio to determine whether the combination ratio of the indoor units is equal to or less than the reference combination ratio, limiting a frequency-rising width of the compressor to a predetermined value according to air-volumes of the operating indoor units when the calculated combination ratio is equal to or less than the reference combination ratio, and operating the air-conditioner at the limited value.
Preferably, the combination ratio of the indoor units is equal to the sum of required capacities of the indoor units compared with a capacity of the outdoor unit.
Preferably, the limiting of the frequency-rising width of the compressor includes: checking the air-volumes of all the operating indoor units, determining an air-volume correction coefficient of each of the indoor units, and calculating a maximum frequency capacity (Qmax) of each operating indoor unit on the basis of the determined air-volume correction coefficient of each indoor unit; and limiting a maximum frequency of the compressor for each air-volume according to the calculated maximum operation capacity (Qmax).
Preferably, the maximum operation capacity of each operating indoor unit is calculated by the following equation:
wherein, the capacity for each indoor unit indicates capacity values varying with conditions of the operating indoor units, the air-volume correction coefficient for each indoor unit indicates the air-volume correction values determined according to the air-volumes of the operating indoor units, the capacity calculation coefficient indicates a proportional constant calculated by the capacity and air-volume correction coefficient for each indoor unit, the average air-volume correction coefficient of the operating indoor units indicates an average value of air-volume correction values determined according to the air-volumes of the operating indoor units, and the capacity calculation constant indicates an error value for reducing an error rate created when the capacities of the indoor units are calculated.
Preferably, the capacity for each indoor unit, the capacity calculation coefficient, and the capacity calculation constant are indicative of data pre-stored in a controller according to situations of the operating indoor units.
Preferably, the method further comprises: if the combination ratio of the indoor units is higher than the reference combination ratio, limiting the frequency-rising width of the compressor to a default value indicating an allowable capacity of the compressor, irrespective of the air-volumes of the operating indoor units, and operating the air-conditioner.
In accordance with another aspect of the present invention, there is provided a multi-system air-conditioner comprising: an outdoor unit; a plurality of indoor units connected to the outdoor unit; a compressor for varying its own frequency according to operation capacity of the indoor units; and a controller for comparing a setup temperature with a room temperature by each of the indoor units, calculating a capacity required for each indoor unit, calculating the sum of all the required capacities of the indoor units to calculate a combination ratio of all the operating indoor units, comparing the calculated combination ratio with a reference combination ratio to determine whether the combination ratio of the indoor units is equal to or less than the reference combination ratio, limiting a frequency-rising width of the compressor to a predetermined value according to air-volumes of the operating indoor units when the calculated combination ratio is equal to or less than the reference combination ratio, and operating the air-conditioner at the limited value.
Preferably, the controller is indicative of an outdoor controller contained in the outdoor unit.
Preferably, the controller checks the air-volumes of all the operating indoor units, determines an air-volume correction coefficient of each of the indoor units, calculates a maximum frequency capacity (Qmax) of each operating indoor unit on the basis of the determined air-volume correction coefficient of each indoor unit, and limits a maximum frequency of the compressor for each air-volume according to the calculated maximum operation capacity (Qmax).
Preferably, if the combination ratio of the indoor units is higher than the reference combination ratio, the controller limits the frequency-rising width of the compressor to a default value indicating an allowable capacity of the compressor, irrespective of the air-volumes of the operating indoor units, and operates the air-conditioner.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 shows a graph for controlling a compressor frequency of a conventional multi-system air-conditioner;
FIG. 2 is a conceptual diagram illustrating refrigerant passages of an air-conditioner according to the present invention;
FIG. 3 is a block diagram illustrating a multi-system air-conditioner according to the present invention;
FIGS. 4A to 4B are flow charts illustrating a method for operating the multi-system air-conditioner according to the present invention; and
FIG. 5 shows a graph for controlling a compressor frequency of the multi-system air-conditioner according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.
FIG. 2 is a conceptual diagram illustrating refrigerant passages of an air-conditioner according to the present invention. For the convenience of description and better understanding of the present invention, it is assumed that the multi-system air-conditioner includes a single outdoor unit 10 and four indoor units 20A, 20B, 20C, and 20D connected to the single outdoor unit 10.
Referring to FIG. 2, the multi-system air-conditioner includes the single outdoor unit 10 and a plurality of indoor units 20A, 20B, 20C, and 20D connected in parallel to the outdoor unit 10, and arranges refrigerant pipes between the indoor units 20A, 20B, 20C, 20D and the outdoor unit 10, so that the indoor units 20A, 20B, 20C, and 20D are connected to the outdoor unit 10 via the refrigerant pipes.
The outdoor unit 10 includes a compressor 11, a 4-way valve 12, an outdoor heat-exchanger 13, an outdoor unit fan 14, four electronic expansion valves (EEVs), and an accumulator 16. The four electronic expansion valves (EEVs) correspond to the four indoor units 20A, 20B, 20C, and 20D, respectively. The indoor units 20A, 20B, 20C, and 20D include the indoor heat- exchangers 21A, 21 B, 21C, and 21D, indoor fans 22A, 22B, 22C, and 22D, and indoor temperature sensors 23A, 23B, 23C, and 23D, respectively.
The compressor 11 is used as an inverter-type compressor, which compresses the absorbed refrigerant of a low-temperature and low-pressure so that it discharges the gaseous refrigerant of a high-temperature and high-pressure.
The 4-way valve 12 includes two independent passages, so that the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 is applied to the indoor heat- exchangers 21A, 21 B, 21C, and 21 D via one of the two passages during the heating mode, and is applied to the outdoor heat-exchanger 13 via the other passage during the cooling mode. If the user selects the heating mode or the cooling mode, the 4-way valve 12 is switched on or off to divert the flow of the refrigerant according to the user-selected operation mode.
The outdoor heat-exchanger 13 serves as a condenser for condensing the high-temperature and high-pressure gas refrigerant to the normal-temperature and high-pressure liquid refrigerant in the cooling mode. And, the outdoor heat-exchanger 13 serves as an evaporator for evaporating the low-temperature and low-pressure liquid refrigerant to the gas refrigerant in the heating mode. As a result, the outdoor heat-exchanger 13 can exchange heat with peripheral air according to enthalpy variation.
The outdoor fan 14 serves as a catalyzer for expediting the heat-exchanging operation between the refrigerant flowing in the outdoor heat-exchanger 13 and the air, so that the heat-exchanging capacity of the outdoor unit 10 increases.
The EEVs 15A, 15B, 15C, and 15D are connected between the outdoor heat-exchanger 13 and the indoor heat- exchangers 21 A, 21 B, 21C, and 21D, and expand the normal-temperature and high-pressure liquid refrigerant condensed by one of the heat-exchangers to the low-temperature and low-pressure refrigerant in which the liquid refrigerant and the gas refrigerant are mixed, so that the refrigerant is depressurized.
The accumulator 16 is mounted to a suction part of the compressor 11, so that the refrigerant sucked from the compressor 11 is changed to the gas refrigerant.
The indoor heat- exchangers 21A, 21B, 21C, and 21D serve as an evaporator in the cooling mode, and serve as a condenser in the heating mode, thereby exchanging heat with peripheral air.
The indoor fans 22A, 22B, 22C, and 22D expedites the heat-exchanging between the refrigerant flowing in the indoor heat- exchanger 21A, 21B, 21C, or 21D and the air, and at the same time discharge the cool or warm air to the room to be cooled or heated.
The indoor temperature sensors 23A, 23B, 23C, and 23D detect the room temperatures of the individual indoor units 20A, 20B, 20C, and 20D.
In order to activate the cooling mode or the heating mode, the above-mentioned multi-system air-conditioner diverts the flow of refrigerant by switching the 4-way valve 12 according to a user command.
For example, in the case of the heating mode, the 4-way valve is switched on so that the refrigerant forms a cooling cycle along the solid-line arrow of FIG. 2, in which the cooling cycle is composed of the compressor 11 → the 4-way valve 12 → the indoor heat- exchangers 21A, 21B, 21C, and 21D → the EEVs 15A, 15B, 15C, and 15D → the outdoor heat-exchanger 13 → the 4-way valve 12 → the accumulator 16 → the compressor 11.
In the case of the cooling mode, the 4-way valve 12 is switched off so that the refrigerant forms a cooling cycle along with the dotted-line arrow of FIG. 2, in which the cooling cycle is composed of the compressor 11 → the 4-way valve 12 → the EEVs 15A, 15B, 15C, and 15D → the indoor heat- exchangers 21A, 21B, 21C, and 21D → the 4-way valve 12 → the accumulator 16 → the compressor 11.
FIG. 3 is a block diagram illustrating a multi-system air-conditioner according to the present invention.
Referring to FIG. 3, the outdoor unit 10 includes a microcomputer (also called a microprocessor) and its peripheral circuits, and further includes an outdoor controller 17 for controlling overall operations of the outdoor unit 10, and an inverter circuit 18 for controlling an output frequency of the compressor 11 to change a rotation number of the compressor 11.
The outdoor controller 17 receives the cooling or heating command from the individual indoor units 20A, 20B, 20C, and 20D, controls the refrigerant discharged from the compressor 11 to flow in either the outdoor heat-exchanger 13 or the indoor heat- exchanger 21A, 21B, 21C, and 21D via the 4-way valve 12, so that the cooling or heating operation is carried out.
The outdoor controller 17 receives a control signal from the indoor units 20A, 20B, 20C, and 20D and the comparison result between the setup temperature and the room temperature, and controls rotation of the EEVs 15A, 15B, 15C, and 15D, the outdoor fan 14, and the rotation number of the compressor 11. In this case, the outdoor controller 17 controls the capacity of the compressor 11 (i.e., the output frequency of the inverter circuit) according to the sum of capacities (i.e., the cooling/heating capacities) required for the indoor units 20A, 20B, 20C, and 20D.
The inverter circuit 18 rectifies the voltage supplied from the commercial AC source, converts the rectified voltage into a voltage level of a predetermined frequency according to a control command of the outdoor controller 17, and transmits the converted result to the compressor 11.
The indoor units 20A, 20B, 20C, or 20D include the microcomputer and its peripheral circuits, and further include the indoor controllers 24A, 24B, 24C, and 24D for controlling overall operations of the indoor units 20A, 20B, 20C, and 20D, respectively. The indoor controllers 24A, 24B, 24C, and 24D are connected to the outdoor controller 17 via a communication line, and transmit user commands (e.g., the setup temperature and the setup air-volume) entered by a remote-controller and the room temperatures of the respective indoor temperature sensors 23A, 23B, 23C, and 23D to the outdoor controller 17.
Operations and effects of the above-mentioned multi-system air-conditioner will hereinafter be described with reference to FIGS. 4A and 4B.
FIGS. 4A to 4B are flow charts illustrating a method for operating the multi-system air-conditioner according to the present invention.
Referring to FIGS. 4A and 4B, the multi-system air-conditioner including four indoor units 20A, 20B, 20C, and 20D connected to only one outdoor unit 10 is designed to control a maximum operation frequency of the compressor 11, and a detailed description thereof will hereinafter be described.
The outdoor controller 17 determines whether the multi-system air-conditioner starts operation at operation S100. If it is determined that the multi-system air-conditioner starts operation at operation S100, the outdoor controller 17 receives operation information (e.g., the setup temperature and the setup air-volume) entered by the user from the indoor controllers 24A, 24B, 24C, and 24D contained in the indoor units 20A, 20B, 20C, and 20D at operation S102.
In this case, the indoor temperature sensors 23A, 23B, 23C, and 23D of the indoor units 20A, 20B, 20C, and 20D detect the room temperature of the individual indoor units 20A, 20B, 20C, and 20D, and deliver the detected result to the indoor controllers 24A, 24B, 24C, and 24D, respectively, at operation S104.
Therefore, the indoor controllers 24A, 24B, 24C, and 24D compare the setup temperatures of the indoor units 20A, 20B, 20C, and 20D with the room temperature, calculate the appropriate cooling/heating capacity using the required capacity values of the indoor units 20A, 20B, 20C, and 20D, respectively, and transmit the calculated result to the outdoor controller 17 at operation S106.
Therefore, the outdoor controller 17 calculates the sum of the calculated capacities of the indoor units 20A, 20B, 20C, and 20D, and calculates capacities required for all the indoor units 20A, 20B, 20C, and 20D at operation S108. As well known in the art, each indoor unit 20A, 20B, 20C, or 20D compares the setup temperature with the room temperature, and calculates the required capacity to acquire the appropriate cooling/heating capacity according to the comparison result, so that the required capacities of all the indoor units 20A, 20B, 20C, and 20D can be calculated, and a detailed description thereof will herein be omitted for the convenience of description.
In this way, if the required capacity Q of the indoor units 20A, 20B, 20C, and 20D are calculated, the outdoor controller 17 compares the calculated capacity Q with a second reference capacity Q2 (i.e., 130%) at operation S110. If the calculated capacity Q is higher than the second reference capacity Q2 at operation S110, the outdoor controller 17 determines that the combination ratio (i.e., the sum of all capacities of the indoor units 20A, 20B, 20C, and 20D) of the capacities of the indoor units 20A, 20B, 20C, and 20D is equal to or higher than 130%. This combination ratio of 130% indicates that the area of evaporators of the indoor units 20A, 20B, 20C, and 20D is very large, so that the outdoor controller 17 may have difficulty in obtaining a sufficient temperature of the discharging air although a frequency increases to an allowable capacity of the compressor 11. Therefore, if the cooling mode is required due to a high difference between the room temperature and the setup temperature, the outdoor controller 17 allows the compressor 11 to be operated within a predetermined range from an initial frequency to a maximum frequency (about 100Hz) indicating a default value, irrespective of the air-volume of the indoor unit 20A, 20B, 20C, or 20D, so that the maximum frequency of the compressor 11 is limited to the default frequency and the compressor 11 is operated at operation S112 as shown in FIG. 5.
If the calculated capacity Q is equal to or less than the second reference capacity Q2 at operation S110, the outdoor controller 17 compares the calculated capacity Q with a first reference capacity Q1 (i.e., 100%) at operation S114. If the calculated capacity Q is higher than the first reference capacity Q1 at operation S114, the outdoor controller 17 determines that the combination ratio of the capacities of the indoor units 20A, 20B, 20C, and 20D is in the range from 100% to 130%. This combination ratio of 100% ~ 130% indicates that the area of evaporators of the indoor units 20A, 20B, 20C, and 20D is larger than the capacity of the outdoor unit 10, the compressor 11 limits its own maximum frequency to the rated frequency of about 60Hz as shown in FIG. 5, so that the operation range of the compressor 11 is equal to the range from the rated capacity to the minimum capacity at operation S116.
In this way, if the combination ratio of the indoor units 20A, 20B, 20C, and 20D is higher than the capacity of the outdoor unit 10, and the maximum frequency is limited to about 80% of the rated frequency, the temperature of the discharging air increases because the indoor units 20A, 20B, 20C, and 20D are larger than the outdoor unit 10. Therefore, in order to acquire the sufficient temperature of the discharging air, the outdoor controller 17 allows the capacity to increase to the rated capacity.
In the meantime, if the calculated capacity Q is equal to or less than the first reference capacity Q1 at operation S114, the outdoor controller 17 determines that the combination ratio of the indoor units 20A, 20B, 20C, and 20D is equal to or less than 100%. This combination ratio of 100% or less indicates that the combination ratio (i.e., the sum of all capacities of the indoor units 20A, 20B, 20C, and 20D) of the indoor units 20A, 20B, 20C, and 20D is less than that of the outdoor unit 10. Although the operation capacity drops to 80%, the discharging air has a sufficiently-low temperature when all the air-volumes of the indoor units 20A, 20B, 20C, and 20D indicate the weak air-volume. The temperature of the air discharged from the indoor units 20A, 20B, 20C and 20D may be decreased according to the air volumes of the indoor units 20A, 20B, 20C, and 20D. In this case, the outdoor controller 17 must calculate the maximum operation capacity in consideration of the air-volumes of the indoor units 20A, 20B, 20C, and 20D, and must control the maximum frequency of the compressor 11.
For this purpose, the outdoor controller 17 determines whether the air-volume of a predetermined indoor unit (e.g., the indoor unit A) from among the operating indoor units 20A, 20B, 20C, and 20D is the strong air-volume at operation S118. If the strong air-volume mode is decided at operation S118, the correction coefficient of the air-volume is set to "RH" (e.g., about 1.2 in the strong air-volume mode) at operation S120.
If it is determined whether the air-volume of the operating indoor unit (e.g., the indoor unit A) is not equal to the strong air-volume at operation S118, the outdoor controller 17 determines whether the air-volume of the aforementioned operating indoor unit is equal to the medium air-volume at operation S122. If the medium air-volume is decided at operation S122, the outdoor controller 17 sets the air-volume correction coefficient to "RM" (e.g., about 1.0 in the medium air-volume mode) at operation S124.
If the air-volume of the operating indoor unit (e.g., the indoor unit A) is not equal to the medium air-volume at operation S122, the outdoor controller 17 determines that the operating indoor unit has the weak air-volume so that it sets the air-volume correction coefficient to "RL" (e.g., about 0.7 in the weak air-volume mode) at operation S126.
As described above, provided that the outdoor controller 17 determines the air-volume correction coefficient for each indoor unit 20A, 20B, 20C, or 20D using the above-mentioned method, and checks the air-volumes of all the indoor units 20A, 20B, 20C, and 20D at operation S128, the maximum operation capacity (Qmax) of the indoor units 20A, 20B, 20C, and 20D can be calculated by the following equation at operation S130: $Maximum operation capacity (Qmax) = Σ (Capacity for each indoor unit \times Air - volume correction coefficient for each indoor unit) \times Capacity calculation coefficient + (Average air - volume correction coefficient of the operating indoor units) \times Capacity calculation constant$
In this case, the capacity for each indoor unit indicates the capacity values varying with the condition of the operating indoor units 20A, 20B, 20C, and 20D. The air-volume correction coefficient for each indoor unit indicates the air-volume correction values determined according to the air-volumes of the operating indoor units 20A, 20B, 20C, and 20D. The capacity calculation coefficient indicates a proportional constant calculated by the capacity and air-volume correction coefficient for each indoor unit. The average air-volume correction coefficient of the operating indoor units indicates an average value of the air-volume correction values determined according to the air-volumes of the operating indoor units 20A, 20B, 20C, and 20D. The capacity calculation constant indicates an error value for reducing the error rate created when the capacities of the indoor units 20A, 20B, 20C, and 20D are calculated.
In this case, the capacity for each indoor unit, the capacity calculation coefficient, and the capacity calculation constant are acquired from basic data prescribed in the outdoor controller 17 according to conditions of the operating indoor units 20A, 20B, 20C, and 20D, and are pre-stored in an internal memory of the outdoor controller 17.
If the maximum operation capacity Qmax of the operating indoor units 20A, 20B, 20C, and 20D are calculated, the outdoor controller 17 variably controls the maximum frequency of the compressor 11 according to the maximum operation capacity Qmax of the indoor units 20A, 20B, 20C, and 20D, as shown in FIG. 5, at operation S132.
Thereafter, the outdoor controller 17 determines whether the multi-system air-conditioner stops operation at operation S134. If the multi-system air-conditioner does not stop operation at operation S134, the outdoor controller 17 returns to the operation S104. If the multi-system air-conditioner stops operation at operation S134, the outdoor controller 17 stops all operations of the multi-system air-conditioner.
As is apparent from the above description, the multi-system air-conditioner and a method for operating the same according to the present invention differently set the frequency-rising limitation width of the compressor according to situations of the indoor units, so that the temperature of the discharging air can be similarly maintained in the respective situations. The multi-system air-conditioner actively reflects the situations of the indoor units, so that it can provide the user with a more comfortable environment and can prevent the interior of a house or room from being damaged by an extremely-low air-temperature which may encounter the dewy interior and the water-scattering of the condenser.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims

A method for operating a multi-system air-conditioner which includes an outdoor unit, a plurality of indoor units connected to the outdoor unit, and a compressor for varying its own frequency according to operation capacity of the indoor units, the method comprising:
comparing, by each of the indoor units, a setup temperature with a room temperature, and calculating a capacity required for each indoor unit;

calculating the sum of all the required capacities of the indoor units to calculate a combination ratio of all the operating indoor units; and

comparing the calculated combination ratio with a reference combination ratio to determine whether the combination ratio of the indoor units is equal to or less than the reference combination ratio, limiting a frequency-rising width of the compressor to a predetermined value according to air-volumes of the operating indoor units when the calculated combination ratio is equal to or less than the reference combination ratio, and operating the air-conditioner at the limited value.
The method according to claim 1, wherein the combination ratio of the indoor units is equal to the sum of required capacities of the indoor units compared with a capacity of the outdoor unit.
The method according to claim 1, wherein the limiting of the frequency-rising width of the compressor includes:
checking the air-volumes of all the operating indoor units, determining an air-volume correction coefficient of each of the indoor units, and calculating a maximum frequency capacity (Qmax) of each operating indoor unit on the basis of the determined air-volume correction coefficient of each indoor unit; and

limiting a maximum frequency of the compressor for each air-volume according to the calculated maximum operation capacity (Qmax).
The method according to claim 1, wherein the maximum operation capacity of each operating indoor unit is calculated by the following equation: $Maximum operation capacity (Qmax) = Σ (Capacity for each indoor unit \times Air - volume correction coefficient for each indoor unit) \times Capacity calculation coefficient + (Average air - volume correction coefficient of the operating indoor units) \times Capacity calculation constant$

wherein,
the capacity for each indoor unit indicates capacity values varying with conditions of the operating indoor units,
the air-volume correction coefficient for each indoor unit indicates the air-volume correction values determined according to the air-volumes of the operating indoor units,
the capacity calculation coefficient indicates a proportional constant calculated by the capacity and air-volume correction coefficient for each indoor unit,
the average air-volume correction coefficient of the operating indoor units indicates an average value of air-volume correction values determined according to the air-volumes of the operating indoor units, and
the capacity calculation constant indicates an error value for reducing an error rate created when the capacities of the indoor units are calculated.
The method according to claim 4, wherein the capacity for each indoor unit, the capacity calculation coefficient, and the capacity calculation constant are indicative of data pre-stored in a controller according to situations of the operating indoor units.
The method according to claim 1, further comprising:
if the combination ratio of the indoor units is higher than the reference combination ratio, limiting the frequency-rising width of the compressor to a default value indicating an allowable capacity of the compressor, irrespective of the air-volumes of the operating indoor units, and operating the air-conditioner.
A multi-system air-conditioner comprising:
an outdoor unit;

a plurality of indoor units connected to the outdoor unit;

a compressor for varying its own frequency according to operation capacity of the indoor units; and

a controller for comparing a setup temperature with a room temperature by each of the indoor units, calculating a capacity required for each indoor unit, calculating the sum of all the required capacities of the indoor units to calculate a combination ratio of all the operating indoor units, comparing the calculated combination ratio with a reference combination ratio to determine whether the combination ratio of the indoor units is equal to or less than the reference combination ratio, limiting a frequency-rising width of the compressor to a predetermined value according to air-volumes of the operating indoor units when the calculated combination ratio is equal to or less than the reference combination ratio, and operating the air-conditioner at the limited value.
The multi-system air-conditioner according to claim 7, wherein the controller is indicative of an outdoor controller contained in the outdoor unit.
The multi-system air-conditioner according to claim 7, wherein the controller checks the air-volumes of all the operating indoor units, determines an air-volume correction coefficient of each of the indoor units, calculates a maximum frequency capacity (Qmax) of each operating indoor unit on the basis of the determined air-volume correction coefficient of each indoor unit, and limits a maximum frequency of the compressor for each air-volume according to the calculated maximum operation capacity (Qmax).
The multi-system air-conditioner according to claim 9, wherein the maximum operation capacity of each operating indoor unit is calculated by the following equation: $Maximum operation capacity (Qmax) = Σ (Capacity for each indoor unit \times Air - volume correction coefficient for each indoor unit) \times Capacity calculation coefficient + (Average air - volume correction coefficient of the operating indoor units) \times Capacity calculation constant$

wherein,
the capacity for each indoor unit indicates capacity values varying with conditions of the operating indoor units,
the air-volume correction coefficient for each indoor unit indicates the air-volume correction values determined according to the air-volumes of the operating indoor units,
the capacity calculation coefficient indicates a proportional constant calculated by the capacity and air-volume correction coefficient for each indoor unit,
the average air-volume correction coefficient of the operating indoor units indicates an average value of air-volume correction values determined according to the air-volumes of the operating indoor units, and
the capacity calculation constant indicates an error value for reducing an error rate created when the capacities of the indoor units are calculated.
The multi-system air-conditioner according to claim 7, wherein:
if the combination ratio of the indoor units is higher than the reference combination ratio, the controller limits the frequency-rising width of the compressor to a default value indicating an allowable capacity of the compressor, irrespective of the air-volumes of the operating indoor units, and operates the air-conditioner.