DESC:AN INVERTER AIR CONDITIONER CAPABLE TO OPERATE IN CONSTANT SPEED

FIELD OF THE INVENTION
[0001] The present disclosure relates, generally, to the field of air conditioner. More particularly, the present disclosure relates to an inverter air conditioner capable to operate in constant speed.

BACKGROUND OF INVENTION
[0002] In some region fast and constant cooling is largely required by the customer and a user normally employs a constant speed compressor air conditioner. However, the constant speed compressor air conditioner doesn’t have the mechanism to operate at different speed even if the product has fulfilled the desired requirement. Constant speed compressor air conditioner operates in only two state, either compressor running or compressor not running. Thus, in present scenarios the constant speed compressor air conditioners are nearing the end of their useful life due to BEE (Bureau of Energy Efficiency, Govt. of India) stringent energy efficiency Norms.
[0003] Due to stricter energy efficiency norms, the constant speed compressor air conditioners will become obsolete in near future. It is likely that, variable speed compressor air conditioners or inverter air conditioners may meet user and industrial preferences, owing to their capability to conserve energy by varying the speed of the compressor.
[0004] In some regions of India, such as Rajasthan/Punjab, where cooling requirement is more and Ambient temperature is very high, the inverter air conditioners however do not meet the requirement of user. Accordingly, despite drawbacks, constant speed air conditioners are relied on these regions for following reasons:
1. Constant speed compressor deliver faster/quick cooling as the system continuously works at maximum output throughout. Hence it cools the room faster than inverter air conditioner.
2. Since inverter air conditioner focuses on the saving energy, thus the cooling performance reduces when the indoor temperature approaches towards pre-set temperature by the user, whereas in the constant speed compressor air condition focuses on the cooling performance and deliver full capacity continuously till the room temperature equals to pre-set temperature by the user.
3. In conventional inverter air conditioner as the ambient temperature increases, the cooling performance has to be reduced at the cost of user comfort to protect the system from over pressure/temperature condition.
4. Constant speed compressor air conditioner doesn’t work below 195VAC and above 46°C, whereas the inverter air conditioner work at a wider voltage range 140VAC to 280VAC and operating temperature range up to 52°C.
All above conditions tend to compromise a user experience. Some relevant state of the art literatures has been provided below
[0005] Many air conditioners are available which are able to work in constant speed mode as well as in variable speed mode. CN101726135B titled as “Air-conditioning system with two working modes and control method thereof”, discloses an air-conditioning system with two working modes and a control method thereof. The air-conditioning system with two working modes comprises an air-conditioning refrigerating system and a motor for diving a compressor, wherein the air-conditioning refrigerating system consists of a condenser, an evaporator, an expansion valve and the compressor, the two working modes of the air-conditioning system comprises a synchronous working mode and a frequency conversion working mode; and the motor is a permanent magnet synchronous motor, and a three-phase winding of the motor is connected with a power module of a frequency converter and is connected with a power grid through a working mode switching circuit. By using the working modes of a fixed frequency air conditioner and a variable frequency air conditioner, the large-capacity compressor can be driven by the small-capacity frequency converter. The control method is favourable for reducing the cost of the large-capacity air-conditioning system and improving the reliability of the system. The control method for the air-conditioning system with two working modes is simple and convenient.
[0006] In this prior art, the compressor motor is a 3-phase synchronous AC motor which works on direct AC supply voltage as well as can be controlled with VFD drives for RPM. The compressor runs directly through 3-phase AC supply in fix-speed mode and in variable frequency mode, the same motor is driven through an SCR Circuit. In this method there are more losses are produced in the voltage and power due to the change in power factor. Moreover, in this method, the operation between synchronous mode and variable frequency mode is changed on output capacity requirement. The user has no ability to set mode as per requirement or comfort.
[0007] CN106949581B titled as “Variable frequency air conditioning system and control method thereof”, discloses a variable frequency air conditioning system and a control method thereof, wherein the variable frequency air conditioning system comprises a fixed frequency compressor, a variable frequency compressor, an evaporator, a first condenser and a second condenser, and the evaporator comprises a fixed frequency evaporation unit, a variable frequency evaporation unit and a step control regulating valve connected with the variable frequency evaporation unit. The fixed-frequency compressor, the first condenser and the fixed-frequency evaporation unit are sequentially connected to form a fixed-frequency air-conditioning loop; the variable-frequency compressor, the second condenser, the variable-frequency evaporation unit and the grading control regulating valve are sequentially connected to form a variable-frequency air conditioner loop; the evaporator is provided with a fan, and the graded control regulating valve is electrically connected with the fan and the variable frequency compressor so as to coordinate and control the output between the fan and the variable frequency compressor in a graded manner. The fixed-frequency and variable-frequency dual-system realizes step-less energy regulation by switching, and the stepped control regulating valve realizes the stepped control of the fan and the variable-frequency evaporation unit, so that the suction pressure regulation range of the variable-frequency compressor is improved, the suction pressure is reasonable, and the operation reliability of the variable-frequency compressor is ensured.
[0008] CN2401818Y titled as “One-driven-multiunit air conditioner”, discloses a one-driven-multiunit air conditioner. Indoor machines are mutually connected in parallel and are communicated with an outdoor machine heat exchanger and a compressor then. The utility model is characterized in that the refrigerant inlet end of each indoor machine is respectively communicated with an electronic expansion valve in series; the compressor comprises a variable capacity compressor and a constant speed compressor which are mutually connected in parallel. The output power of the compressor of the utility model can vary following the variation of power required by indoor machines.
[0009] In both of the above mentioned prior arts, CN106949581B and CN2401818Y, there are two types of compressor used to operate in two different modes. Fix Speed Compressor in Fix Speed Mode and variable frequency compressor in Variable mode. There are two different refrigerant circuits used for operation in different modes. The variable frequency air conditioning system adopts a fixed frequency system and a variable frequency system by switching between the fixed frequency compressor and the variable frequency compressor. Such type of arrangement is very expensive.
[0010] CN102032642A titled as “Control method of inverter air conditioner”, discloses a control method of an inverter air conditioner, comprising the following steps of: A. starting the inverter air conditioner; B. operating a controller or a control panel of the inverter air conditioner, starting a mode selection function of the air conditioner and selecting one work mode from an automatic mode, a speed-limiting mode or a constant speed mode; and C. ensuring that the inverter air conditioner works under the selected mode. A user can set the work mode of the inverter air conditioner according to the requirement per se to improve the comfortableness, so that the air conditioner is more humanized; and the air conditioner not only has the advantages of general air conditioners, but also can be set according to the requirement of the user, thereby solving the problems of the general air conditioners in noise, energy efficiency and comfortableness. In this prior art, the AC can run in following three modes; a) Automatic Mode, b) Frequency Limiting Mode & c) Constant speed mode. In "constant speed mode", the air conditioner is operated at a set frequency and is maintained. The set frequency of the air conditioner is the default set frequency of the air conditioner or the frequency set by a user. There is no provision for exit from this mode.
[0011] CN101769584B titled as “Method for intelligently controlling frequency of variable-frequency air-conditioner” discloses a method for intelligently controlling the frequency of a variable-frequency air-conditioner, comprising the following steps of: (1) reading the temperature difference delta T of the set temperature of the variable-frequency air-conditioner and indoor ambient temperature and calculating a frequency value Ft according to the temperature difference by a frequency converter;(2) reading each running parameter of the variable-frequency air-conditioner and controlling the air-conditioner to stop, or limit the frequency, or reduce the frequency or normally run according to the parameter value by using the frequency converter; (3) if each parameter displays that the frequency needs to be limited, ensuring the adjusted frequency Fobj to be equal to Ft, and if each parameter displays that the frequency needs to be reduced, ensuring the Fobj to be equal to Ft-delta T; (4) if each parameter displays the normal running, adjusting the frequency Ft according to the variation of the delta T in a certain time t1; and (5) outputting the Fobj to a driver of a variable-frequency compressor of the air-conditioner by using the frequency converter. The method can improve the comfort level, the using effect and the service life of the variable-frequency air-conditioner. This prior art provides a variable frequency air conditioner in particular to an intelligent control method for the frequency of a variable frequency air conditioner. There is no option given to user to set or switch modes.
[0012] In the above mentioned prior arts, separate units or compressor are used for constant speed and variable speed modes, which consumes more energy, leave a huge carbon footprint, and are expensive. Also the inverter AC vary their speed on the basis input voltage, not as per the user need, and employ a silicon controlled rectifier (SCR) circuit which are prone to losses and not energy efficient. Thus, there lies at least a need of an improved inverter AC which is capable to switch modes as per user needs, as well as energy efficient.

OBJECT OF THE INVENTION
[0013] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0014] It is a general or primary object of the present disclosure to provide an inverter air conditioner capable to run in fixed speed as well as variable speed as per user need.
[0015] It is another object of the present disclosure is to provide an inverter air conditioner has a single compressor capable to run in fixed speed as well as variable speed.
[0016] It is yet another object of the present disclosure is to provide an inverter air conditioner with an improved driver circuit which are not prone to losses.

SUMMARY OF THE INVENTION
[0017] This summary is provided to introduce concepts related to an air conditioner capable to run in fixed speed mode as well as variable speed mode. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0018] In an aspect, the present disclosure provides an inverter air conditioner (AC) capable to operate in constant speed/frequency comprising: a mode selector configured to enable user to select a mode from a variable speed mode and a fixed speed mode. The AC also has a temperature selector configured to enable user to select a desired temperature (set temperature) Ts, a temperature sensor configured to determine the temperature of surrounding (room temperature) Tr and a microcontroller configured to calculate the temperature difference ?T (Tr – Ts) between the desired temperature Ts and the temperature of surrounding Tr. The AC further has a microcontroller connected to a PWM generator configured to read the temperature difference ?T. In variable speed mode, the microcontroller calculates the frequency value F to drive a motor of a compressor that sets according to the value of ?T and selected mode. In fixed speed mode, the microcontroller (instead of calculating frequency) selects the frequency value F between at least between three frequency values selected form the group of F_stop, F_low and F_high on the basis of temperature difference ?T.
[0019] In an embodiment of fixed speed mode operation, the present disclosure provides that the microcontroller selects the frequency value F_stop which is equal to zero frequency and stops the motor when the ?T is less than zero.
[0020] In another embodiment of fixed speed mode operation, the present disclosure provides that the microcontroller selects the frequency value F_low which is equal to half of maximum value of frequency F_high when the ?T is zero.
[0021] In yet another embodiment, the present disclosure provides that the frequency value F_low is in the range of 10-55Hz.
[0022] In still another embodiment of fixed speed mode operation, the present disclosure provides that the microcontroller selects the frequency value F_high which is equal to maximum value of frequency when the ?T is greater than zero.
[0023] In a further embodiment, the present disclosure provides that the frequency value F_high is in the range of 56-110Hz.
[0024] In preferred embodiment of fixed speed mode operation, the present disclosure provides that the compressor will always run at a single speed F_high as an overriding value, until unless ?T is zero.
[0025] In another embodiment, the present disclosure provides that in variable speed mode, the microcontroller selects the frequency value F from a group of frequencies on the basis of temperature difference ?T.
[0026] In yet another embodiment, the present disclosure provides that in variable speed mode, the frequency value F is in the range of 10-110Hz.
[0027] In still another embodiment, the present disclosure provides that the microcontroller is sending the selected frequency to a PWM generator to generate switching signals to drive the motor through IGBT/IPM circuit.
[0028] In further embodiment, the present disclosure provides that a heat exchanger is provided at a condenser side to maintain a system pressure and temperature within a predetermined range by heat radiation, wherein heat exchanger comprises a 2-row, twenty-six hair pin for radiating heat and designed as a 5mm heat exchanger.
[0029] In preferred embodiment, the present disclosure provides that the heat exchanger at the condenser side is a high volume heat-exchanger.
[0030] In more preferred embodiment, the present disclosure provides that a heat exchanger is provided at an evaporator side comprising a two row, sixteen hair pin for heat radiation and designed as a 7mm heat-exchanger.
[0031] In another aspect, the present disclosure provides a method of controlling an inverter air conditioner capable to operate in variable or constant speed comprising: switching the inverter circuit in a mode selected by user by a mode selector from a variable speed mode and a fixed speed mode. The method includes receiving a desired temperature Ts selected by user by a temperature selector, determining the temperature of surrounding Tr by a temperature sensor and calculating temperature difference ?T (Tr – Ts) between the desired temperature Ts and the temperature of surrounding Tr by a microcontroller. The method also includes reading the temperature difference ?T and calculate the frequency value F to drive a motor that sets the microcontroller according to the value of ?T and selected mode. However, in fixed speed mode, the microcontroller selects the frequency value F between three frequency values selected form the group of F_stop, F_low and F_high on the basis of temperature difference ?T.
[0032] In an embodiment, the present disclosure provides that in variable speed mode, the microcontroller selects the frequency value F form a group of frequencies on the basis of temperature difference ?T.
[0033] In the present invention, in the constant speed mode, the proposed inverter air conditioner will work in two predefined compressor frequencies referred as F_high & F_low and in three levels where the inverter air conditioner can run in a constant speed to give Full cooling performance and also the user has flexibility to switch to inverter mode to save more energy.
[0034] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.
[0035] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF DRAWINGS
[0036] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0037] FIG. 1 illustrates the flowchart indicating the working of air conditioner in accordance with an embodiment of the present disclosure;
[0038] FIG. 2A illustrates the graphical representation of compressor frequency up-trend in constant speed mode, in accordance with an embodiment of the present disclosure;
[0039] FIG. 2B illustrates the graphical representation of compressor frequency down-trend in constant speed mode of inverter AC in accordance with an embodiment of the present disclosure;
[0040] FIG. 2C illustrates the graphical representation of compressor frequency up-trend and down-trend in variable speed mode of inverter AC in accordance with an embodiment of the present disclosure;
[0041] FIG. 3A illustrates the block diagram of motor driver circuit which run the compressor of inverter AC in accordance with an embodiment of the present disclosure;
[0042] FIG. 3B illustrates the circuit diagram of electrical drive which run the compressor of inverter AC in accordance with an embodiment of the present disclosure;
[0043] FIG. 3C illustrates the circuit diagram of inverter AC in accordance with an embodiment of the present disclosure;
[0044] FIG. 4 illustrates an assembly of PCB with heat sink of inverter AC in accordance with an embodiment of the present disclosure;
[0045] FIG. 5A illustrates a top view of high-volume heat exchanger in accordance with an embodiment of the present disclosure;
[0046] FIG. 5B illustrates a front view of high-volume heat exchanger in accordance with an embodiment of the present disclosure;
[0047] FIG. 5C illustrates a side view of high-volume heat exchanger in accordance with an embodiment of the present disclosure;
[0048] The figures depict embodiments of the present subject matter for illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF INVENTION
[0049] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0050] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0051] The terminology used herein is to describe particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0052] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0053] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0054] In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
[0055] Hereinafter, a description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary, a variety of optional components are described to illustrate the wide variety of possible embodiments of the present disclosure.
[0056] FIG. 1 illustrates the flowchart indicating the working of air conditioner in accordance with an embodiment of the present disclosure. More specifically, FIG. 1 refers the working of inverter air condition in constant speed mode by way of block diagram.
[0057] In the present disclosure an inverter air conditioner with an additional mode is provided where the proposed inverter air conditioner can run in a constant speed to give full cooling performance until product reaches towards pre-set temperature by user and provide highest cooling satisfaction to user. In this additional mode, the inverter air conditioner is working in at least three levels and the user has flexibility to switch to inverter mode to save more energy.
[0058] Upon activation of the constant speed mode in step 102 from a default inverter mode in step 101, the proposed inverter air conditioner will work in two predefined compressor frequencies referred as F_high & F_low under three condition. During the operation in constant speed mode, air conditioner will operate as per following conditions.
At step 103: when ?T= -1°c: compressor will set to F_stop level
At step 104, when ?T = 0°c: compressor will run at F_low level
At step 105, when ?T= 2°c: compressor will run at F_high level were ?(delta) T: Tr (room temperature) - Ts (set/desired temperature)
[0059] FIG. 2A and Fig. 2B refer a compressor frequency uptrend and down trend with respect to fixed/constant speed mode of operation. In constant speed mode, if ?t= -1°c, compressor will set to F_stop level. Upon the increase of temperature difference, the compressor will change its frequency from 0 to half value of maximum frequency. On further increase of temperature difference, the compressor will change its frequency from half value to maximum value of frequency. This increasing trend of frequency is shown in FIG. 2A.
[0060] Similarly, when ?t = 2°c: compressor will run at F_high level. Upon the decrease of temperature difference, the compressor will change its frequency from maximum value to half value of maximum frequency. On further drop of temperature difference, the compressor will change its frequency from half value of maximum value to zero. This decreasing trend of frequency is shown in FIG. 2B.
[0061] FIG. 2C illustrates a graphical representation of compressor frequency up-trend and down-trend in variable speed mode. In variable speed mode, the selection of the compressor speed/frequency is depending on the ?T (Tr – Ts) the difference between the room/surrounding temperature and the desired/set temperature by the user. At different values of ?T, microcontroller selects different target frequency levels out of multiple target levels. When the values of ?T is higher than the highest ?T Target level, microcontroller selects maximum frequency as a target frequency to run the compressor at the maximum speed. As the ?T reduces, based on the confidential algorithms, microcontroller selects lower target frequency. The uptrend and down trend of AC in variable speed mode is shown in FIG. 2C.
[0062] In the inverter AC as disclosed in present disclosure an improved drive circuit is provided which based on IGBT instead of SCR, thereby rendering the inverter AC free of losses.
[0063] FIG. 3A shows a general block diagram for motor driver circuit 300 or motor driver 300 which is essentially a IGBT/IPM Circuit. It mainly consists of power source, converter, motor, load, sensing module, and control module.
[0064] FIG. 3B illustrates the circuit diagram of motor driver 300 which drives the compressor of inverter AC in accordance with an embodiment of the present disclosure. The AC to DC conversion of electric power converts AC input power source 310 to the DC link voltage, as may be observed via a DC link capacitor 320. The DC to AC conversion is known as inverter operation which converts the DC power to AC power required by motor and is normally accomplished by pulse width modulation technique. As a part of inverter circuit 330, six IGBTs are used to drive 3-phase BLDC motor. A PWM generator 350 circuit is required to control the gate pulses of each IGBT. An MCU base controller 340 circuit is required to sense the feedback from motor speed and changes the required frequencies via the PWM generator 350 to achieve desired speed. The area indicated by dotted line represent the part of microcontroller 340 which is provided on a PCB 300 as later shown in Fig. 4.
[0065] As shown by dotted portion, the microcontroller block is provided with a speed controller and a current Controller. Speed controller section controls the speed by sensing the rotation per second of compressor rotor. Current controller section controls the total overall current flowing through the inverter circuit 330 in the microcontroller 340 and protect the system from overload. Additionally, it has an (A/D) analog to digital converter that converts the analog signal to digital signal in the microcontroller 340 and a current Sensor sense the current flowing through inverter section 330 and input current before DC link capacitor 320 in the microcontroller 340. Speed calculation is an algorithm in the microcontroller 340 that calculate the speed of compressor from the data received from current controller.
[0066] FIG. 3C shows a block diagram of the inverter AC 400 in accordance with an embodiment of present disclosure incorporating the motor drive and microcontroller circuit 300 of FIG. 3A and FIG. 3B. The inverter AC 400, which in an example corresponds to a split AC standard configuration, has two control unit, one is indoor control unit and other is outdoor control unit. The outdoor control unit receives the value of ambient temperature and the digital signal of various sensors such as discharge sensor provided in compressor, condenser sensor etc. The analog to digital unit receives the signal data and convert them to digital signal and sent the digital signals to outdoor controller. On the basis of received digital signal, the circuit 300 of Fig. 3B controls the speed of compressor and outdoor unit motor of the inverter AC which in turn runs condenser and evaporator. The indoor control unit is communicatively connected with the outdoor control unit. The indoor control unit receives value of ambient temperature and data from evaporator sensor and controls the speed of indoor motor.
[0067] FIG. 4 illustrates an assembly 600 of a PCB or a motherboard instantiating the circuit 300 with a heat-sink 500 for the inverter AC 400 of Fig. 3C in accordance with an embodiment of the present disclosure. An embodiment of the present disclosure provides an inverter AC having the PCB instantiating the circuit 300 with improved and efficient heat sink 500 as shown in Fig. 4. The circuit 300 of preceding figures are incorporated as a system on chip (SOC) or a modular system upon the PCB. The selected component can withstand temperature above 65°C. With a newly designed Highly efficient heatsink, PCB component temperature is kept within the acceptable range, preventing a change in compressor speed during normal running. The new heatsink design will enable the AC to operate at maximum load even in hotter environments.
[0068] Additionally, the inverter AC 400 disclosed in present disclosure is protected using five different temperature sensors, the unit doesn't trip at higher temperatures because of high discharge pressure. Constant speed compressor air conditioner runs at fixed speed. The system is designed to deliver fix amount of cooling capacity and system pressure. When the system continuously runs at higher ambient or lower voltage, the component temperature increases due to continuous operation. Highly efficient heatsink helps to radiate heat for the components into the ambient and reduce extra burden from the component. Its overall help system to run continuously with full capacity even at higher ambient temperature.
[0069] When constant speed compressor air conditioner works continuously, compressor internal temperature increases and accelerate during higher temperature. As a result, it overshoots the max. temperature range and the OLP (Overload Protector) protect the compressor and trip. Whereas in Inverter air conditioners, the system pressure and temperature are continuously monitored with five negative temperature coefficient thermal sensors. It protects the system to run at higher system limits by change the compressor speed in higher ambient condition. The additional sensor gives precise system temperature parameter and real-time ambient temperature to the control unit to work efficiently.
[0070] The inverter air conditioner in accordance with an embodiment of present disclosure comprises a heat exchanger at an evaporator side comprising a two row, sixteen hair pin for heat radiation and designed as a 7mm heat-exchanger and a heat exchanger at a condenser side to maintain a system pressure and temperature within a predetermined range by heat radiation. The heat exchanger at condenser side comprises a 2-row, twenty-six hair pin for radiating heat and designed as a 5mm heat exchanger. The heat exchanger at the condenser side is a high volume heat-exchanger.
[0071] Fig. 5A-5C illustrate various views of high-volume heat exchanger 500 at a condenser side as referred by “CONDENSER” in Fig. 3C. FIG. 5A illustrates a top view of heat high-volume heat exchanger. FIG. 5B illustrates a front or plan view of heat high-volume heat exchanger and FIG. 5C illustrates a side view with respect to the plan view in Fig. 5B in accordance with an embodiment of the present disclosure. As shown in Fig. 5B, the heat exchanger at condenser side comprises a 2-row, twenty-six hair pin indicated by the reference sign “02”, for radiating heat and designed as a 5mm heat exchanger. The heat exchanger at the condenser side is a high volume heat-exchanger.
[0072] Due to the change in the frequency, the overall output capacity of an inverter air conditioner reduces at higher temperature, such that high-volume heat exchanger and robust system designing and balancing is required to maintain the system pressure and temperature at optimum limits to deliver almost 100% output even at higher ambient temperature. High-volume heat exchanger helps system to radiate the heat quickly and efficiently into the ambient. Accordingly, at least as shown in Fig. 5B, a system design of the state of the art heat exchanger at the condenser side is upgraded from 1-row to 2-row, twenty-six hair pin and 5mm heat exchanger at the condenser side. More volume is added in condenser side to dissipate more heat at high ambient. At evaporator side heat exchanger referred by “EVAPORATOR” in Fig. 3C, the system is designed with a two row, sixteen hair pin and 7mm heat exchanger.
[0073] The present invention is best suitable for north western area of Indian territory where ambient temperature goes very high above 46°C to 52°C as well as the voltage condition is less than 15% of rated voltage. Because of high ambient temperature, generally a conventional fixed speed air conditioner stops working due to overload protector inside compressor due to high discharge pressure and temperature. Conventional fix speed air conditioner doesn’t operate at lower input voltage less than 15% of rated voltage. At higher temperature conventional inverter air conditioner operates at lower compressor speed and protects system from overload tripping condition due to which, systems performance reduces. In the proposed inverter air conditioner, an additional mode is provided where the proposed inverter air conditioner can run in a constant speed to give full cooling performance until product reaches towards pre-set temperature by user and provide highest cooling satisfaction to user.
Equivalents
[0074] The foregoing description of the preferred embodiment of the invention has been presented for illustration and description. It is not intended to be exhaustive, nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiment may be modified in light of the above teachings.
,CLAIMS:We Claim:
1. An inverter air conditioner (400) capable to operate in constant speed/frequency comprising:
a mode selector (102) configured to enable user to select a mode from a variable speed mode and a fixed speed mode;
a temperature selector configured to enable user to select a desired temperature (set temperature) Ts;
a temperature sensor configured to determine the temperature of surrounding (room temperature) Tr;
a microcontroller (340) configured to calculate the temperature difference ?T (Tr – Ts) between the desired temperature Ts and the temperature of surrounding Tr;
characterized in that
a microcontroller (340) configured to read the temperature difference ?T and calculate the frequency value F to drive a motor of a compressor that sets according to the value of ?T and selected mode,
wherein in fixed speed mode, the microcontroller (340) selects the frequency value F between three frequency values (103, 104, 105) selected form the group of F_stop, F_low and F_high on the basis of temperature difference ?T.
2. The inverter air conditioner (400) as claimed in claim 1, wherein the microcontroller (340) selects the frequency value F_stop which is equal to zero frequency and stops the motor when the ?T is less than zero.
3. The inverter air conditioner (400) as claimed in claim 1, wherein the microcontroller (340) selects the frequency value F_low which is equal to half of maximum value of frequency when the ?T is zero.
4. The inverter air conditioner (400) as claimed in claim 1, wherein the frequency value F_low is in the range of 10-55Hz.
5. The inverter air conditioner (400) as claimed in claim 1, wherein the microcontroller (340) selects the frequency value F_high which is equal to maximum value of frequency when the ?T is greater than zero.
6. The inverter air conditioner (400) as claimed in claim 1, wherein the frequency value F_high is in the range of 56-110Hz.
7. The inverter air conditioner (400) as claimed in claim 5, wherein the compressor operates at a single speed F_high, until unless ?T is zero.
8. The inverter air conditioner (400) as claimed in claim 1, wherein in variable speed mode, the microcontroller (340) selects the Frequency value F from a group of frequencies on the basis of temperature difference ?T.
9. The inverter air conditioner (400) as claimed in claim 8, wherein in variable speed mode, the Frequency value F is in the range of 10-110Hz.
10. The inverter air conditioner (400) as claimed in claim 1, wherein the microcontroller (340) is sending the selected frequency to a PWM generator (350) to generate switching signals to drive the motor through IGBT/IPM (330) inverter circuit.
11. The inverter air conditioner as claimed in claim 1, further comprising a heat exchanger at a condenser side to maintain a system pressure and temperature within a predetermined range by heat radiation, wherein heat exchanger comprises a 2-row, twenty-six hair pin for radiating heat and designed as a 5mm heat exchanger.
12. The inverter air conditioner (400) as claimed in claim 11, wherein the heat exchanger at the condenser side is a high volume heat-exchanger.
13. The inverter air conditioner (400) as claimed in claim 11, further comprising a heat exchanger at an evaporator side comprising a two row, sixteen hair pin for heat radiation and designed as a 7mm heat-exchanger.
14. A method of controlling an inverter air conditioner (400) capable to operate in constant speed comprising:
switching (102) the inverter in a mode selected by user by a mode selector from a variable speed mode and a fixed speed mode;
receiving a desired temperature Ts selected by user by a temperature selector;
determining the temperature of surrounding Tr by a temperature sensor;
calculating temperature difference ?T (Tr – Ts) between the desired temperature Ts and the temperature of surrounding Tr by a microcontroller (340);
characterized by
reading the temperature difference ?T and calculating the frequency value F to drive a motor that sets by the microcontroller (340) according to the value of ?T and selected mode,
wherein in fixed speed mode, the microcontroller selects the frequency value F between three frequency values (103, 104, 105) selected form the group of F_stop, F_low and F_high on the basis of temperature difference ?T.

15. The method as claimed in claim 14, wherein in variable speed mode, the microcontroller selects the frequency value F form a group of frequencies on the basis of temperature difference ?T.