Claims:
1. A cooling system for an inverter drive, said inverter drive being placed in an outdoor unit of an air conditioning system, the cooling system comprising:
an air-tight housing enclosing the inverter drive to form a closed-loop air path inside the air-tight housing around the inverter drive; and
a means for passing air along and outside of one of sides of the air-tight housing for cooling the air within the air-tight housing circulating in the closed loop air path to cool the inverter drive.

2. The cooling system as claimed in claim 1, wherein a side of the air-tight housing in contact with the means for passing air is a plain or corrugated metal sheet.

3. The cooling system as claimed in claim 1 or 2, wherein the means for passing the cool air includes an air passage for passing the air through the air passage and a fan for drawing fresh air from the outside atmosphere.

4. The cooling system as claimed in claim 3, wherein the air passage is configured so that the fan draws the fresh air over an accumulator placed in the outdoor unit to cool air.

5. The cooling system as claimed in claim 3, wherein the air passage comprises a refrigerant line for cooling the fresh air.

6. An outdoor unit of an air conditioning system, comprising
a fan motor, a compressor, a condenser, an inverter drive, all installed in the air-tight housing;
an air-tight housing enclosing the inverter drive in the air-tight housing, said air tight chamber forms a closed-loop air path inside the air-tight housing around the inverter drive; and
a means for passing air along and outside of one of sides of the air-tight housing for cooling the air within the air-tight housing circulating in the closed loop air path to cool the inverter drive.

7. The outdoor unit as claimed in claim 6, wherein a side of the air-tight housing in contact with the means for passing air includes a plain or corrugated metal sheet.

8. The outdoor unit as claimed in claim 6 or 7, wherein the means for passing the cool air includes an air passage for passing the air through the air passage and a fan for drawing fresh air from the outside atmosphere.

9. The outdoor unit as claimed in claim 8, wherein the air passage is configured so that the fan draws the fresh air over an accumulator placed in the outdoor unit to cool air.

10. The outdoor unit as claimed in claim 8, wherein the air passage comprises a refrigerant line for cooling the fresh air.
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)

&

THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

INVERTER DRIVE COOLING SYSTEM FOR AN AIR CONDITIONING SYSTEM;


BLUE STAR LIMITED, A COMPANY INCORPORATED UNDER COMPANIES ACT 1956, WHOSE ADDRESS IS KASTURI BUILDINGS, MOHAN T. ADVANI CHOWK, JAMSHETJI TATA ROAD, MUMBAI-400020, MAHARASTRA, INDIA

THE FOLLOWING SPECIFICATION PARICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION
The present invention relates generally to air conditioning systems and particularly to inverter drive cooling systems for cooling a Variable Frequency Drive (VFD) of the air conditioning systems.
BACKGROUND OF INVENTION
In air conditioning or refrigeration systems, a refrigerant fluid undergoes a cycle of four phases, namely, compression, condensation, expansion, and evaporation. Compressors are used to compress the refrigerant fluid in the air conditioning or refrigeration systems to maintain the air conditioning or refrigeration systems within desired limits under varying load conditions. A Variable Frequency Drive (VFD) (also referred to as “inverter drive”) is used to control speed of the compressors. The inverter drive includes power electronic components that control the speed of the compressor by varying a frequency and a voltage supplied to electric motors of the compressors. The inverter drive modifies the compressor speeds based on demand of cooling of the air conditioning systems. Generally, the inverter drives are found in a sealed or entirely closed-in portion of the outdoor section cabinet. The inverter drives get overheated and therefore, require cooling due to the need to protect the power electronic components.
Presently, in one method of cooling, outdoor/ambient air is used to cool the power electronic components. A fan is connected to pass air over the inverter drive. The fan draws fresh air from external atmosphere. The fresh air is passed over the inverter drive. The fresh air exchanges heat with the inverter drive. Since temperature of the fresh air is less than the temperature of the inverter drive, the temperature of the inverter drive is reduced. In such cases, however, interaction of moisture, pollutants, and salts which are typically found in the external atmosphere, with the inverter drive, leads to deterioration or failure of the power electronic components within the inverter drive.
Another way of cooling the inverter drive is mounting the power electronic components of inverter drive on a heat sink and removing heat from the heat sink by circulating coolant in or around the heat sink. The capability of the heat sink and the cooling system are of primary consideration in determining the power capacity of the inverter drive. However, the heat sink requires additional piping, controls, and heat-sink paste, etc. resulting into increased complexity and increased cost of the air conditioning or refrigeration systems.
Therefore, there is a need for an inverter drive cooling system that reduces complexity and improves efficiency of the air conditioning or refrigeration systems.
Summary of the invention
Accordingly, the present invention provides a cooling system for an inverter drive placed in an outdoor unit of an air conditioning system. The cooling system comprises an air-tight housing enclosing the inverter drive and a means for passing air. The air-tight housing forms a closed-loop air path around the inverter drive. The means for passing air passes air along and outside of one of sides of the air-tight housing for cooling the air within the air-tight housing circulating in the closed loop air path. The air circulating within the air-tight chamber cools due to the heat exchange between the air outside the air-tight chamber and thereby cools the inverter drive.
The present invention also provides an outdoor unit of an air conditioning system, comprising a fan motor, a compressor, a condenser, an inverter drive, all installed in an air-tight housing, the air-tight housing enclosing the inverter drive in the air-tight housing and a means for passing air along and outside of one of sides of the air-tight housing. The air-tight housing forms a closed-loop air path around the inverter drive inside the air-tight housing and the means passes air for cooling the air within the air-tight housing circulating in the closed loop air path to cool the inverter drive.
According to an embodiment of the present invention, the means for passing the cool air includes an air passage for passing the air through the passage and a fan to draw fresh air in the air passage. Advantageously, the passage is configured so that the fan draws the fresh air over an accumulator placed in the outdoor unit to cool air. Alternatively, the passage comprises a refrigerant line for cooling the air.
In an embodiment, the passage is configured so that the fan drives fresh air from the external atmosphere and passes the fresh air over a refrigerant line of the outdoor unit to cool air.
In an embodiment, the side of the air-tight housing in contact with the means for passing air is a plain or corrugated metal sheet.
BRIEF DESCRIPTION OF DRAWINGS
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments:
FIG. 1 shows an open view of a portion of outdoor unit comprising a system for cooling an inverter drive in accordance with an embodiment of the present invention;
FIGS. 2A & 2B show the various view of the cooling an inverter drive of FIG. 1 in accordance with an embodiment of the present invention;
FIG. 3 shows air flow passage over an accumulator of the outdoor unit of FIG. 1 in accordance with an embodiment of the present invention; and
FIG. 4 shows an exploded view of a cooling side of the system for cooling an inverter drive of the in accordance with one of the preferable embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.
References in the specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, characteristic, or function, described in connection with the embodiment, is included in at least one embodiment of the invention.
The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
It is very well known that an outdoor unit of an air conditioning system comprises a fan motor, a compressor, a condenser and an inverter drive installed in the air-tight housing along with their arrangement in the air-tight housing. Hence, to explain the present invention, only invention related views of the outdoor unit have been shown.
Referring FIG. 1 shows an open view of a portion of the outdoor unit (100) comprising a system for cooling an inverter drive (102) in accordance with an embodiment of the present invention. The outdoor unit (100) is included in an air conditioning system (not shown). The air conditioning system further includes an indoor unit (not shown). The inverter drive (102) is connected to a compressor (not shown) of the air conditioning system. The inverter drive (102) controls an operating speed of the compressor.
The system for cooling an inverter drive of the outdoor unit (100) shows an air-tight housing (108) around an inverter drive (102) along with an accumulator (104) and open view of the air-tight housing portion (105) of the outdoor unit (100).
The air-tight housing (108) encloses the inverter drive (102) to form a closed-loop air path around the inverter drive (102) preferably at a backside of the inverter drive (102). The flow of the air in the closed-loop air path is depicted as closed-loop air flow (110). Advantageously, the closed-loop air flow (110) flows naturally through the closed-loop air path in the air-tight housing (108). Alternatively, the closed-loop air path may include a drive fan unit to forcefully circulate air in the closed-loop air path within the air-tight housing (108).
Referring Figures 2A and 2B show a means for passing air according to the present invention that comprises a fan (not shown) for drawing fresh air from outside surrounding atmosphere and an air passage (106) for passing fresh air. As shown in Figure 2A and 2B, a side (202) of the air-tight housing (108) is in contact with the air passage (106) of a means for passing air that together acts a heat exchanger.
As shown in Figures 2-4, the side of the air-tight housing (108) in contact with the air passage (106) of a means for passing air includes a corrugated metallic sheet (202). Alternatively, a plain sheet may also be placed in place of the corrugated metallic sheet (202).
The closed-loop air flow (110) flows along one side of the corrugated metallic sheet (202). Fresh air flows along other side of the corrugated metallic sheet (202) through the air passage (106) and is depicted by the fresh air flow (210). The fresh air flow (210) is drawn from surrounding atmosphere of the outdoor unit by a fan (not shown) to pass through a passage of the air passage (106) for passing air. The fresh air being drawn from the surrounding atmosphere is at a lower temperature and the closed-loop air (110) flows around the inverter drive (102) at a higher temperature. The corrugated metallic sheet (202) enables heat-transfer between the fresh air (210) and the closed-loop air (110). The cooled closed-loop air (110) flows within the closed-loop air path within the air-tight housing (108) for cooling the inverter drive (102). Therefore, a temperature of the inverter drive (102) is maintained within a desired temperature range, thereby increasing the efficiency of the air conditioning system.
Referring FIG. 2B shows a back view of the system for cooling in accordance with an embodiment of the present invention. The air flow (210) is expelled in to the external atmosphere through a discharge port (302) at the end of the air passage (106).
Referring FIG. 3 shows an exploded view of the accumulator (104) of the outdoor unit (100) in accordance with one of the preferable embodiment of the present invention. According to the present invention, the means for passing air is configured in such a way that the fresh air entering in the air passage (106) gets cooled by passing over the accumulator (104) of the outdoor unit. The fan (not shown) of the means for passing air can be fitted before the accumulator (104) or at the discharge port of the passage for drawing the fresh air. Alternatively, a means for passing is configured in such a way that a part of fresh air drawn the condenser fan unit (not shown) of the outdoor unit (100) can be diverted to pass over the accumulator for cooling and then pass through the air passage (106) thereby the condenser fan acts as a fan of the means for passing air. Alternatively, the fresh air can be directly passed through the air passage (106) without cooling or passing over the accumulator (104). The said arrangement depends upon the weather or atmospheric conditions where the outdoor unit (100) is to be installed. In an alternative embodiment, the means for passing air comprises a refrigerant line for cooling the air at an inlet of the air passage (106)
Referring FIG. 4 shows an exploded view of the air passage (106) of FIG. 2 in accordance with an embodiment of the present invention. The air passage (106) includes the corrugated metallic sheet (202) which is also a side of the air-tight housing (108), the discharge port (302), and a cover (502).
The discharge port (302) is located on upper back side of the heat exchanger through which the hot air (210) is discharged in to the external atmosphere. The cover (502) is placed over the corrugated metallic sheet (202) such that a space between the cover (502) and the corrugated metallic sheet (202) forms the air passage (106) through which the cool air (210) flows. The corrugated metallic sheet (202) increases surface area enabling maximum heat exchange between the cool air and the closed-loop air.
In operation, the fan draws the fresh air (410) and passes the fresh air (410) over the accumulator (104). The fresh air (410) exchanges heat with the accumulator (104) and is converted in to cool air (210). The cool air (210) is passed through the air passage (106). The closed-loop air (110) is passed on the other side of the corrugated metallic sheet (202) of the air passage (106). The heat is exchanged between the closed-loop air (110) and the cool air (210) such that the temperature of the closed-loop air (110) is reduced after the heat exchange. The hot air (210) is thereafter discharged in to the external atmosphere through the discharge port (302). As a result, the inverter drive (102) within the air-tight housing (108) is cooled by the closed-loop air flow (110).
As in the present invention, the inverter drive (102) is housed in the air tight housing (108), no dust enters, hence no dust accumulates over the inverter drive (102) or moisture contact with the components of the inverter drive (102) thereby safeguard the components of the inverter drive (102). Further, the present invention indirectly cools the inverter drive (102) thereby safeguarding from overheating and increasing the life of the inverter drive (102) substantially and increasing the efficiency of the outdoor unit (100).
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Further, it will be apparent to one of the ordinary skill in the art that many modifications, improvements and sub-combinations of the various embodiments, adaptations and variations can be made to the invention without departing from the scope thereof as claimed in the following claims: