Air conditioning apparatus and control method thereof

Information

  • Patent Grant
  • 6732539
  • Patent Number
    6,732,539
  • Date Filed
    Wednesday, November 27, 2002
    21 years ago
  • Date Issued
    Tuesday, May 11, 2004
    20 years ago
Abstract
An air conditioning apparatus and control method thereof is provided, in which a pulse width modulation compressor and a two-stage variable-capacity compressor are connected in parallel with each other to control capacities of the two compressors according to indoor air conditioning loads. The air conditioning apparatus is cost-competitive because a capacity supplied by the pulse width modulation compressor is relatively low in cost, and the cost required for manufacturing the compressor is reduced in proportion to the reduced capacity. Accordingly, with the air-conditioning apparatus an effect is obtainable in which a variable-capacity compressor with small capacity and a two-stage variable-capacity compressor with large capacity are controlled as if a large-scale variable-capacity compressor with a same capacity as a total capacity of the two compressors were linearly controlled.
Description




CROSS-REFERENCE TO RELATED APPLICATION




This application claims the benefit of Korean Application No. 2002-33222, filed Jun. 14, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates generally to an air conditioning apparatus and control method thereof, which has a pulse with modulation compressor and a two-stage variable-capacity compressor.




2. Description of the Related Art




Generally, a single air conditioning apparatus in which one indoor unit is connected to one outdoor unit does not have a large indoor air conditioning load (required capacity), so a fixed-capacity compressor is installed in the outdoor unit.




On the contrary, a multi-unit air conditioning apparatus in which a plurality of indoor units are connected to one outdoor unit is designed such that each of the indoor units independently copes with an air conditioning load of a corresponding indoor space. In such a multi-unit air conditioning apparatus, since air conditioning loads of respect indoor units are different and vary at any time, a variable-capacity compressor is installed in an outdoor unit, and a flow of refrigerant is controlled by ascertaining loads and operating states using communication between each of the indoor units and the outdoor unit. Further, the variable-capacity compressor is controlled by a microcomputer of the outdoor unit. The outdoor unit microcomputer checks the air conditioning requirements with respect to a corresponding indoor space, a temperature condition of the corresponding indoor space, etc. based on information received from each of the indoor units, and controls a capacity of the compressor according to the checked information.




However, since a conventional multi-unit air conditioning apparatus employs a construction in which a plurality of indoor units are connected to one outdoor unit, a compressor installed in the outdoor unit must be designed to endure a maximum indoor air conditioning load. Further, in order for a compressor to endure the maximum indoor air conditioning load, a significant difficulty arises in the production of the compressor. That is, a plurality of performance tests must be carried out so as to increase the capacity of the compressor.




A high-capacity compressor produced by the above process is problematic in that the high-capacity compressor is very expensive, relative to a conventional compressor.




A manner in which a variable-capacity compressor and a fixed-capacity compressor are mixed to cope with indoor air conditioning loads is used in consideration of the above problem.




As shown in

FIG. 1

, a variable-capacity compressor


10


, which operates at a capacity that is varied according to a frequency of an inverter circuit and a fixed-capacity compressor


20


which operates at a constant capacity are connected in parallel with each other. Further, an outdoor unit microcomputer controls capacities of the variable-capacity compressor


10


and the fixed-capacity compressor


20


according to indoor air conditioning loads (required capacities) received from respective indoor units. Referring to

FIG. 2

, if the indoor air conditioning loads are 0 to 50%, the outdoor unit microcomputer controls the capacity of the variable-capacity compressor


10


. In this case, the microcomputer controls the capacity of the variable-capacity compressor


10


by varying a frequency outputted to the variable-capacity compressor


10


from an inverter circuit within a predetermined range R


1


according to the indoor air conditioning loads (required capacities) received from the respect indoor units. Further, if the indoor air conditioning loads are 50 to 100%, the outdoor unit microcomputer controls the capacities of the variable-capacity compressor


10


and the fixed-capacity compressor


20


. In this case, the microcomputer copes with an insufficient capacity by controlling the capacity of an inverter-type variable-capacity compressor


10


operated according to frequency of the inverter circuit within a predetermined range R


2


after activating the fixed capacity compressor


20


.




However, if the conventional air conditioning apparatus is used for facilities such as large buildings, a capacity, which must be provided by a variable-capacity compressor, inevitably becomes large. Further, to produce such a high-capacity compressor as an independent device is difficult and expensive, even though an independent device can be produced, thus causing an economic burden by increasing a price of the compressor.




Therefore, in the multi-unit air conditioning apparatus, a method is required of effectively coping with a large-scale indoor air conditioning load (required capacity). Further, a method of accommodating requirements for the large-scale air conditioning capacity while using a conventional compressor is seriously required.




SUMMARY OF THE INVENTION




Accordingly, an air conditioning apparatus and control method thereof is provided, in which a pulse width modulation compressor and a two-stage variable-capacity compressor are connected in parallel with each other to cope with indoor air conditioning loads, thus realizing the compressors at a low price.




Additional aspects and 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 order to accomplish the above and other aspects an air conditioning apparatus is provided, comprising a first compressor controlled in a pulse width modulation manner; a second compressor connected in parallel with the first compressor and controlled to operate at one of a minimum capacity and a maximum capacity; and a control unit controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to indoor air conditioning loads.




Further, an air conditioning apparatus is provided, comprising a plurality of indoor units; and an outdoor unit connected to the plurality of indoor units comprising a first compressor controlled in a pulse width modulation manner; a second compressor connected in parallel with the first compressor and controlled to operate at one of a minimum capacity and a maximum capacity, and an outdoor control unit controlling the capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to indoor air conditioning loads required by the indoor units.




Further, a method of controlling an air conditioning apparatus is provided, the air conditioning apparatus having a plurality of indoor units connected to an outdoor unit comprising a first compressor controlling a capacity of the outdoor unit in a pulse width modulation manner and a second compressor operating at one of a minimum capacity and a maximum capacity, comprising calculating an air conditioning capacity required by corresponding indoor units; and controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to the calculated air conditioning capacity, wherein a maximum capacity of the first compressor is equal to the minimum capacity of the second compressor, and the maximum capacity of the second compressor is twice the minimum capacity of the second compressor.




An embodiment of the present invention uses two compressors connected in parallel with each other, and controls capacities of the two compressors similarly to an operation of controlling a capacity of a single large-capacity compressor. One of the compressors is a pulse width modulation compressor which linearly controls the capacity of the pulse width modulation compressor, and another compressor is a two-stage variable-capacity compressor which has a relatively large capacity and operates at two different capacities.











BRIEF DESCRIPTION OF THE DRAWINGS




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





FIG. 1

is a view showing a construction of a conventional air conditioning apparatus in which a variable-capacity compressor and a fixed-capacity compressor are connected in parallel with each other;





FIG. 2

is a graph showing an operation of controlling capacities of the compressors of

FIG. 1

;





FIG. 3

is a view showing a construction of an air conditioning apparatus in which a pulse width modulation compressor and a two-stage variable-capacity compressor are connected in parallel with each other according to an embodiment of the present invention;





FIG. 4

is a view showing a construction in which an oil equalization tube is connected to the compressors according to the embodiment of the present invention;





FIG. 5

is a graph showing an operation of controlling capacities of the compressors according to the embodiment of the present invention;





FIG. 6

is a flowchart of a method of controlling the air conditioning apparatus according to the embodiment of the present invention; and





FIG. 7

is a block diagram showing a multi-unit air conditioning according to the embodiment of the present invention.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Reference will now made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.





FIG. 3

is a view showing a construction in which a pulse width modulation compressor and a two-stage variable-capacity compressor are connected in parallel with each other according to an embodiment of the present invention.




As shown in

FIG. 3

, the air conditioning apparatus comprises two compressors


30


and


40


connected in parallel with each other. The compressors


30


and


40


can be applied to a multi-unit air conditioning apparatus, as shown in

FIG. 7

, in which a plurality of indoor units


60


are connected to one outdoor unit


80


. In this case, the compressors


30


and


40


are installed in the outdoor unit


80


, and capacities of the compressors


30


and


40


are under control of an outdoor unit controller


70


(i.e., a microcomputer).




A capacity of the first compressor


30


is controlled in response to a duty control signal outputted from a pulse width modulation circuit (not shown) under control of the outdoor unit controller


70


. That is, the outdoor unit controller


70


calculates an indoor air conditioning load (required capacity) by communicating with respective indoor units


60


and controls the capacities of the compressors according to the calculated indoor air conditioning load. In this case, the first compressor


30


is a pulse width modulation compressor whose capacity is controlled by modulating pulse widths corresponding to a loading operation (discharging refrigerant) and an unloading operation (not discharging refrigerant) within a given cycle according to a capacity of a compressor


30


controlled, and controlling a pulse width modulation (PWM) valve of the compressor


30


using the pulse width modulated duty control signal.




The second compressor


40


is a two-stage variable-capacity compressor which has a compressing room P, a bypass tube


40




a


connecting one side of the compressing room P with a suction side, and a valve


40




b


disposed in a middle of the bypass tube


40




a


. If the valve


40




b


is closed according to a control instruction of the outdoor unit controller


70


, the compressing room P performs a compression of all refrigerant, so the second compressor


40


is operated at 100% capacity, which is a maximum capacity. Alternatively, if the valve


40




b


is opened according to a control instruction of the outdoor unit controller


70


, a part of the refrigerant is leaked out through the suction side, so the second compressor


40


is operated at 50% capacity, which is a minimum capacity.




As described above, the second compressor


40


operates at one of a minimum capacity or a maximum capacity, which are two different capacities, determined by the outdoor unit controller


70


. It is further understood that additional compressors can be added to add more capacities as needed, which operates with a total capacity characteristic which is linear.




A maximum capacity of the first compressor


30


is equal to the minimum capacity of the second compressor


40


, and corresponds to a half of the maximum capacity of the second compressor


40


. The capacity of the first compressor


30


is set relatively low to reduce the manufacturing cost as much as possible because a variable-capacity compressor is expensive relative to a fixed-capacity compressor, and a typical compressor becomes more expensive as a maximum capacity of the compressor becomes larger.




A device to keep oil supplied to the first and second compressors


30


and


40


with different capacities may be provided. An oil equalization tube B may be employed, as shown in FIG.


4


.




As shown in

FIG. 4

, an oil separator


50


is arranged in discharge sides of the first and second compressors


30


and


40


to separate refrigerant and oil. A capillary tube


51


is disposed between the first compressor


30


and the oil separator


50


. Further, the oil equalization tube B is disposed between the first and second compressors


30


and


40


to connect an oil storing room of the first compressor


30


with an oil storing room of the second compressor


40


.




Oil separated from the refrigerant by the oil separator


50


returns to the first compressor


30


through the oil equalization tube B. In this case, an additional oil equalizing operation is not performed.




Hereinafter, the operation of the air conditioning apparatus and control method thereof according to the present invention is described in detail with reference to

FIGS. 5 and 6

.




The air conditioning apparatus is applied to a multi-unit air conditioning apparatus in which an indoor air conditioning load may be highly varied. In this case, the multi-unit air conditioning apparatus is described, in which a plurality of indoor units


60


are connected to one outdoor unit


80


, the indoor units


60


and the outdoor unit


80


mutually communicate with each other, and an outdoor unit controller


70


to control several compressors installed in the outdoor unit controls capacities of the compressors according to indoor air conditioning loads (required capacities) received from respective indoor units


60


.




First, the outdoor unit controller


70


calculates a total indoor air conditioning load (required capacity) by summing up the air conditioning loads received from corresponding indoor units


60


of the plural indoor units


60


at operation S


110


.




Then, the outdoor unit controller


70


determines whether the calculated total required capacity is 0 at operation S


120


. If the total required capacity is 0, the outdoor unit controller


70


stops operations of both the first and second compressors


30


and


40


at operation S


130


.




If the total required capacity is not 0 at operation S


120


, the outdoor unit controller


70


determines whether the total required capacity is equal to or less than 33% of a total capacity of the compressors


30


,


40


at operation S


140


. If the total required capacity is equal to or less than 33% of the total capacity of the compressors, the microcomputer stops an operation of the second compressor


40


, and controls the capacity of the first compressor


30


to correspond to the calculated total required capacity by applying a duty control signal to the first compressor through a pulse width modulation circuit and thereby controlling the PWM valve of the first compressor


30


to be opened (in an unloading operation of not discharging refrigerant) or closed (in a loading operation of discharging refrigerant) in response to the duty control signal, as shown in P


11


of

FIG. 5

, at operations S


150


, S


160


and S


170


.




If the total required capacity is more than 33% of the total capacity of the compressors


30


,


40


at operation S


140


, the outdoor unit controller


70


determines whether the total required capacity is equal to or less than 67% of the total capacity of the compressors at operation S


180


. If the total required capacity is equal to or less than 67% of the total capacity of the compressors, the outdoor unit controller


70


opens the valve


40




b


so as to allow the second compressor


40


to operate at a minimum capacity (with reference to B of FIG.


5


), and controls the capacity of the first compressor


30


to correspond to the calculated total required capacity by applying a duty control signal to the first compressor through the pulse width modulation circuit and thereby controlling the PWM valve of the first compressor


30


to be opened or closed in response to the duty control signal, as shown in P


12


of

FIG. 5

, at operations S


190


, S


200


and S


210


.




If the total required capacity is more than 67% of the total capacity of the compressors


30


,


40


at operation S


180


, the outdoor unit controller


70


closes the valve


40




b


so as to allow the second compressor


40


to operate at the maximum capacity (with reference to C of

FIG. 5

) and controls the capacity of the first compressor


30


to correspond to the calculated total required capacity by applying a duty control signal to the first compressor through the pulse width modulation circuit and thereby controlling the PWM valve of the first compressor


30


to be opened or closed in response to the duty control signal, as shown in P


13


of

FIG. 5

, at operations S


220


, S


230


and S


240


.




After the operations S


130


, S


170


, S


210


and S


240


are performed, processing returns to the starting operation.




As described above, an air conditioning apparatus and control method thereof is provided, in which a pulse width modulation variable-capacity compressor and a two-stage variable-capacity compressor are connected in parallel with each other, thus enabling the capacities of the compressors to be controlled in correspondence with the indoor air conditioning loads (required capacities). Further, the air conditioner is advantageous in that the air conditioner is cost-competitive because a capacity supplied by the pulse width modulation compressor is relatively low, and the cost required for manufacturing the pulse width modulation compressor is reduced in proportion to the reduced capacity requirements. It is understood that additional compressors can be used, and that the micro controller can be a computer implementing the control method which is programmed on a computer readable medium or in firmware.




Although a few preferred 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 this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.



Claims
  • 1. An air conditioning apparatus, comprising:a first compressor controlled in a pulse width modulation manner; a second compressor connected in parallel with the first compressor and controlled to operate at one of a non-zero minimum capacity and a maximum capacity; and a control unit to control capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to indoor air conditioning loads.
  • 2. The air conditioning apparatus according to claim 1, wherein the control unit controls a capacity of the first compressor using to a duty control signal to control a cycle for loading and unloading operations, a maximum capacity of the first compressor is equal to the minimum capacity of the second compressor, and the maximum capacity of the second compressor is at or greater than about twice the minimum capacity of the second compressor.
  • 3. The air conditioning apparatus according to claim 1, wherein the second compressor includes a bypass tube to bypass refrigerant to a suction side and a valve disposed in a middle of the bypass tube, andthe second compressor operates such that if the valve is closed, all refrigerant flows through a discharge side so that the second compressor operates at the maximum capacity, and if the valve is opened, a part of the refrigerant flows through the suction side so that the second compressor operates at the minimum capacity.
  • 4. The air conditioning apparatus according to claim 1, further comprising:an oil equalization tube to connect the first compressor with the second compressor so as to keep oil supplied to the first and second compressors in suitable states.
  • 5. An air conditioning apparatus, comprising:a plurality of indoor units; and an outdoor unit connected to the plurality of indoor units, comprising, a first compressor controlled in a pulse width modulation manner; a second compressor connected in parallel with the first compressor and controlled to operate at one of a non-zero minimum capacity and a maximum capacity, and an outdoor control unit to control the capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to indoor air conditioning loads required by the indoor units.
  • 6. A method of controlling an air conditioning apparatus, the air conditioning apparatus having a plurality of indoor units connected to an outdoor unit comprising a first compressor controlling a capacity of the first compressor in a pulse width modulation manner and a second compressor operating at one of a minimum capacity and a maximum capacity, comprising:calculating an air conditioning capacity required by corresponding indoor units; and controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is linearly controlled according to the calculated air conditioning capacity, wherein a maximum capacity of the first compressor is equal to the minimum capacity of the second compressor, and the maximum capacity of the second compressor is at or greater than about twice the minimum capacity of the second compressor.
  • 7. The control method of the air conditioning apparatus, according to claim 6, wherein the controlling comprises:stopping operations of the first and second compressors, if the calculated air conditioning capacity is 0; stopping an operation of the second compressor and controlling the capacity of the first compressor by determining a duty control signal corresponding to the calculated air conditioning capacity and performing loading and unloading operations in response to the duty control signal, if the required air conditioning capacity is greater than 0 and is less than or equal to the maximum capacity of the first compressor; allowing the second compressor to operate at the minimum capacity and controlling the capacity of the first compressor by determining the duty control signal corresponding to the calculated air conditioning capacity and performing the loading and unloading operations in response to the duty control signal, if the calculated air conditioning capacity is greater than the maximum capacity of the first compressor and is less than or equal to the maximum capacity of the second compressor; and allowing the second compressor to operate at the maximum capacity and controlling the capacity of the first compressor by determining the duty control signal corresponding to the calculated air conditioning capacity and performing the loading and unloading operations in response to the duty control signal, if the calculated air conditioning capacity is greater than the maximum capacity of the second compressor.
  • 8. An air conditioning apparatus, comprising:a first compressor controlled using pulse width modulation; a second compressor connected in parallel with the first compressor and operated at different non-zero capacities; and a control unit controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is varied according to indoor air conditioning loads.
  • 9. The air conditioning apparatus according to claim 8, wherein the control unit controls a capacity of the first compressor and a maximum capacity of the first compressor is substantially equal to a minimum one of the capacities of the second compressor, and a maximum one of the capacities of the second compressor being at or more than two times the minimum capacity of the second compressor.
  • 10. The air conditioning apparatus according to claim 8, wherein the control unit controls the capacity of the first compressor using to a duty control signal controlling a cycle for loading and unloading operations.
  • 11. The air conditioning apparatus according to claim 8, wherein the second compressor includes a bypass tube bypassing refrigerant to a suction side and a valve disposed in a middle of the bypass tube, andthe second compressor operates such that if the valve is closed, all the refrigerant flows through a discharge side of the second compressor, so the second compressor operates at one of the capacities capacity, and if the valve is opened, a part of the refrigerant flows through the suction side of the second compressor, so the second compressor operates another one of the capacities.
  • 12. The air conditioning apparatus according to claim 8, further comprising:an oil equalization connecting the first compressor with the second compressor so as to supply oil to the first and second compressors according to the indoor air conditioning loads.
  • 13. An air conditioning apparatus, comprising:a plurality of indoor units; and an outdoor unit connected to the plurality of indoor units, comprising, a variable-capacity compressor controlled using in pulse width modulation, a two-level compressor connected in parallel with the variable-capacity compressor and controlled to operate at one of a non-zero first capacity and a non-zero second capacity, and an outdoor control unit to control the capacities of the variable-capacity compressor and the two-level compressor such that a total capacity of the variable-capacity compressor and the two-level compressor is controlled by setting the capacity of the two-level compressor at one of the first capacity and the second capacity and varying the variable-capacity compressor using a duty control signal controlling a cycle for loading and unloading operations.
  • 14. The air conditioning apparatus according to claim 13, whereina maximum capacity of the variable-capacity compressor is equal to the first capacity of the two-level compressor, and the second capacity of the two-level compressor is two times or more the first capacity of the two-level compressor.
  • 15. A method of controlling an air conditioning apparatus, the air conditioning apparatus having a plurality of indoor units connected to an outdoor unit comprising a first compressor controlling a capacity of the first compressor using pulse width modulation and a second compressor operating at one of a first capacity and a second capacity, a maximum capacity of the first compressor is equal to the first capacity of the second compressor, and the second capacity of the second compressor is two times or more the first capacity of the second compressor, the method comprising:calculating an air conditioning capacity according to indoor air conditioning loads; and controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is varied according to the calculated air conditioning capacity by setting a capacity of the second compressor to one of the first capacity and the second capacity, and varying by pulse width modulating the capacity of the first compressor.
  • 16. The control method of the air conditioning apparatus according to claim 15, wherein controlling capacities further comprises:stopping operations of the first and second compressors, if the calculated air conditioning capacity is 0; stopping an operation of the second compressor and controlling the capacity of the first compressor by determining a duty control signal corresponding to the calculated air conditioning capacity and performing loading and unloading operations in response to the duty control signal, if the calculated air conditioning capacity is greater than 0 and is less than or equal to the maximum capacity of the first compressor; allowing the second compressor to operate at the first capacity and controlling the capacity of the first compressor by determining the duty control signal corresponding to the calculated air conditioning capacity and performing the loading and unloading operations in response to the duty control signal, if the calculated air conditioning capacity is greater than the maximum capacity of the first compressor and is less than or equal to the second capacity of the second compressor; and allowing the second compressor to operate at the second capacity and controlling the capacity of the first compressor by determining the duty control signal corresponding to the calculated air conditioning capacity and performing the loading and unloading operations in response to the duty control signal, if the calculated air conditioning capacity is greater than the second capacity of the second compressor.
  • 17. The control method of the air conditioning apparatus according to claim 15, wherein controlling capacities further comprises:operating the first and second compressors at the calculated air conditioning capacity by setting the capacity of the second compressor to operate at a higher capacity of the first capacity of the second compressor and the second capacity of the second compressor, while not exceeding the calculated air conditioning capacity, and by adjusting the capacity of the first compressor to operate at a capacity equal to a difference between the calculated air conditioning capacity and the capacity set for the second compressor.
  • 18. The control method of the air conditioning apparatus according to claim 15, wherein controlling capacities further comprises:setting the capacity of the second compressor to operate at a higher capacity of the first capacity of the second compressor and the second capacity of the second compressor, not exceeding the calculated air conditioning capacity; and adjusting the capacity of the first compressor to operate at a capacity substantially equal to a difference between the calculated air conditioning capacity and the capacity of the second compressor in said setting.
  • 19. An air conditioning apparatus having a first compressor and a second compressor and a control unit, wherein:the first compressor is controlled using pulse width modulation; the second compressor is connected in parallel with the first compressor and is operated at one of a non-zero first capacity and a non-zero second capacity; and the control unit controls capacities of the first and second compressors and varies a total capacity of the first and second compressors according to indoor air conditioning loads.
  • 20. A controller for controlling an air conditioning apparatus having a first compressor and a second compressor, comprising:a control unit controlling the first compressor using pulse width modulation and the second compressor, which is connected in parallel with the first compressor and operated at different non-zero capacities, and the control unit controls the first and second compressors by varying the capacities of the first and second compressors such that a total capacity of the first and second compressors is varied according to indoor air conditioning loads.
  • 21. A machine readable storage medium for controlling a computer to operate an air conditioning apparatus having a plurality of indoor units connected to an outdoor unit comprising a first compressor operating using pulse width modulation, and a second compressor operating at one of a first capacity and a second capacity, a maximum capacity of the first compressor being substantially equal to a minimum one of the capacities of the second compressor, and a maximum one of the capacities of the second compressor being at or more than two times the minimum capacity of the second compressor, the machine readable storage medium storing a program to execute:calculating an air conditioning capacity according to indoor air conditioning loads; and controlling capacities of the first and second compressors such that a total capacity of the first and second compressors is varied according to the calculated air conditioning capacity by setting a capacity of the second compressor to one of the first capacity and the second capacity, and varying by pulse width modulating the capacity of the first compressor.
  • 22. An air conditioning apparatus, comprising:at least three or more compressors connected in parallel, one of the at least three or more compressors controlled using pulse width modulation, and the remaining compressors operated at different non-zero capacities; and a control unit controlling capacities of the first and second compressors such that a total capacity of the at least three or more compressors is linearly varied according to indoor air conditioning loads.
Priority Claims (1)
Number Date Country Kind
10-2002-33222 Jun 2002 KR
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Number Name Date Kind
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5050397 Sugiyama et al. Sep 1991 A
6018957 Katra et al. Feb 2000 A
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6401469 Dennis et al. Jun 2002 B1
6612121 Moon et al. Sep 2003 B2
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Entry
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