Cooling device for a frequency converter, converter assembly comprising said cooling device and refrigerating or conditioning plant comprising said converter assembly

A cooling device for a frequency converter of a refrigerating or conditioning plant comprises at least one thermal exchange element supplied with a total flow rate of refrigerating fluid; regulating means configured to selectively regulate the total flow rate of refrigerating fluid on the basis of at least one parameter indicative of the temperature of the frequency converter.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a U.S. national stage application under 35 U.S.C. § 371 of PCT Application No. PCT/IB2014/061921, filed Jun. 3, 2014, which claims priority to Italian patent application MI2013A000910, filed Jun. 3, 2013, the entireties of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a cooling device for a frequency converter, to a converter assembly comprising said cooling device and to a refrigerating or conditioning plant comprising said converter assembly.

BACKGROUND ART

Frequency converters, better known as “inverters”, are used to regulate capacity or flow rate of the compressor in refrigerating plants used in the refrigeration and air conditioning industry.

The frequency converter is indeed connected to the compressor so as to regulate the supply of the electric motor of the compressor and to modify compressor speed.

The possibility of varying compressor speed is of fundamental importance because it allows consumption to be reduced when the plant requires a smaller refrigerating capacity than the maximum one. Indeed, maximum power in refrigerating or conditioning plants is only required for short periods.

In addition to energy savings, the possibility of regulating compressor speed also optimizes temperature control, thus eliminating thermal shocks.

Frequency converters normally used in refrigerating plants require a cooling device, usually an air cooling device, configured to cool the electronic components of the converter.

Nevertheless, components of a frequency converter are subject to variable heating mode and time.

Cooling devices of known type are configured to uniformly and constantly cool the components of the converter. Such a solution involves the occurrence of over-cooling or of under-cooling situations, depending on the operating conditions of the converter.

This inevitably involves the creation of condensate in the converter, with apparent risks in terms of converter reliability, or the occurrence of high temperatures which cause the system to stop safely.

A known solution, described in document WO 2011/117829, provides associating the heat exchanger with a fan configured to uniformly distribute the temperature in the shell containing both the heat exchanger and the frequency converter. Nevertheless, such a solution provides bleeding a constant quantity of refrigerating fluid, at the compressor inlet of the refrigerating or conditioning plant, even when the cooling needs of the frequency converter are reduced. This involves a reduction of the flow rate of refrigerating fluid available for the plant and therefore an overall reduction of the refrigerating efficiency of the plant.

A further solution provides using sponges capable of absorbing the excess moisture in the converter. However, such a solution does not sufficiently ensure the integrity and reliability of the components of the frequency converter.

DISCLOSURE OF INVENTION

It is thus one object of the present invention to make a cooling device for a frequency converter of refrigerating or conditioning plant which does not have the drawbacks of known art herein noted; in particular, it is one object of the invention to make a cooling device capable of avoiding the formation of condensate in the frequency converter and which, at the same time, optimizes the efficiency of the refrigerating plant.

In accordance with such objects, the present invention relates to a cooling device for a frequency converter of a refrigerating or conditioning plant according to claim1.

It is a further object of the invention to provide a converter assembly for a refrigerating or conditioning plant capable of avoiding the formation of condensate in the frequency converter and of optimizing the efficiency of the refrigerating plant.

In accordance with such objects, the present invention relates to a converter assembly for a refrigerating or conditioning plant.

It is finally one object of the present invention to make a refrigerating or conditioning plant with optimized cooling efficiency with respect to the one of plants of the known art.

In accordance with such objects, the present invention relates to a refrigerating or conditioning plant.

BEST MODE FOR CARRYING OUT THE INVENTION

Numeral1inFIG. 1indicates a refrigerating plant in which a refrigerating fluid circulates.

Refrigerating fluid is intended as a refrigerating substance which may take on the liquid or gaseous state in plant1according to the pressure and temperature conditions to which it is subjected.

The refrigerating fluid may be selected in the group comprising HCFC, HFC, HC, CO2 and HFO.

Plant1comprises a compressor2, a condenser3, an expansion valve4, an evaporator5and a converter assembly6.

Compressor2is configured to compress the refrigerating fluid and supply it to condenser3by means of a high pressure delivery line7. In particular, the refrigerating fluid that is supplied to condenser3is in the form of vapour.

The refrigerating fluid in the form of vapour in condenser3is transformed into liquid form.

A high pressure line8supplies the refrigerating fluid output from condenser3to the expansion valve4, where the pressure of the liquid refrigerating fluid is lowered in order to lower the evaporation temperature.

A low pressure line9supplies the refrigerating fluid output from the expansion valve4to evaporator5, where heat is removed so that the refrigerating fluid evaporates at a constant pressure.

A low pressure suction line10supplies the refrigerating fluid in the form of vapour and at low pressure, to compressor2.

Compressor2is preferably a screw refrigerating compressor. It is understood that compressor2may be any other known type of compressor such as, for example, a piston compressor, a centrifugal compressor, etc.

Compressor2comprises an electric motor (not illustrated in the accompanying drawings for simplicity), the supply of which is regulated by the converter assembly6.

The converter assembly6comprises a frequency converter12, configured to regulate the supply of the electric motor of compressor2and to modify the speed of compressor2, and a cooling device13, configured to cool the frequency converter12.

The frequency converter12and the cooling device13are shown diagrammatically inFIG. 1and are preferably arranged in contact with each other to promote the conduction cooling of the frequency converter12.

The cooling device13is supplied with a refrigerating fluid.

In the non-limiting embodiment described and illustrated herein, the cooling device13is supplied with the same refrigerating fluid that circulates in the refrigerating or conditioning plant1. In particular, the cooling device13comprises a suction line14configured to draw the refrigerating fluid downstream of condenser3, a draining line15configured to drain the refrigerating fluid upstream of compressor2, and a thermal exchange element16connected to the suction line14and to the draining line15.

With reference toFIG. 2, the cooling device13also comprises a radiator17, which at least partly houses the thermal exchange element16.

The thermal exchange element16comprises at least a first portion18supplied, in use, with a first flow rate Q1of refrigerating fluid and at least a second portion19, which is also supplied, in use, with a second flow rate Q2of refrigerating fluid.

The first portion18is configured to cool a respective first region40(FIG. 3) of the frequency converter12, while the second portion is configured to cool a respective second region41(FIG. 3) of the frequency converter12.

Preferably, the first portion18and the second portion19are coplanar and are side by side to conduction cool the first region40(FIG. 3) and the second region41(FIG. 3), respectively, of the frequency converter12. Preferably, the first region40and the second region41(FIG. 3) are arranged side by side and comprise components with different thermal input to be disposed of, such as for example IGBTs and diodes.

In detail, the first portion18comprises a first inlet channel20, a first expansion element21, a first main channel22and a first regulating valve23.

The first inlet channel20and the first main channel are connected to each other by the first expansion element21. In the non-limiting embodiment described and illustrated herein, the first expansion element21is defined by a narrowing of cross-section between the first main channel22and the first inlet channel20.

The first inlet channel20is connected to the suction line14and is supplied with the refrigerating fluid drawn downstream of condenser3.

The narrowing defined, by the first expansion element21determines the expansion of the refrigerating fluid in the first main channel22.

The first regulating valve23is configured to regulate the first flow rate Q1of refrigerating fluid supplied to the main channel22.

The first regulating valve23is preferably a solenoid valve provided with a main body24and with an occluding element (not shown in the accompanying drawings).

The main body24comprises a coil in which a channel is made. The occluding element is coupled to a ferrous nucleus arranged in a channel, and to a spring, arranged in the inner channel abutting against the ferrous nucleus. The occluding element is arranged so as to selectively occlude the narrowing of cross-section of the expansion element21. One variant provides for the occluding element to be arranged so as to occlude the main channel22.

In use, when the coil is not supplied with current, the spring keeps the occluding element in the position occluding the narrowing.

When the coil is supplied with current, the ferrous nucleus is attracted by the coil until overcoming the force of the spring and determining a sufficient movement of the occluding element to free the narrowing.

One variant (not illustrated) provides the regulating valve23to be configured to make a fine regulation of the flow rate of refrigerating fluid supplied to the first portion18. For example, the regulating valve23may be a variable regulating valve.

Preferably, the first main channel22extends along a first serpentine path, which is preferably flat, and has a cross-section increasing along the flow direction of the refrigerating fluid.

Thereby, the expansion of the fluid is continuous along the first main channel22. The heat removed from the refrigerating fluid causes the temperature of the refrigerating fluid to increase. However, such rising of temperature is compensated for by the continuous expansion of the fluid along the first main channel22. Thereby, the temperature along the first main channel22is substantially kept constant.

Preferably, the first expansion element21and the first main channel22are wholly housed in radiator17, while the first inlet channel20and the main body24of the regulating valve23are arranged outside of radiator17.

The second portion19is substantially identical to the first portion18and comprises a second inlet channel26, a second expansion element27, a second main channel28and a second regulating valve29.

The second inlet channel26and the second main channel28are connected to each other by the second expansion element27. In the non-limiting embodiment herein described and illustrated, the second expansion element27is defined by a narrowing of cross-section between the second main channel28and the second inlet channel26.

The second inlet channel26is connected to the suction line14and is supplied with the refrigerating fluid drawn downstream of condenser3.

The narrowing defined by the second expansion element27determines the expansion of the refrigerating fluid in the second main channel28.

The second regulating valve29is configured to regulate the second flow rate Q2of refrigerating fluid supplied to the second main channel28.

The second regulating valve29is preferably a solenoid valve provided with a main body30and with an occluding element (not shown in the accompanying drawings).

The main body30comprises a coil in which a channel is made. The occluding element is coupled to a ferrous nucleus arranged in a channel, and to a spring, arranged in the inner channel abutting against the ferrous nucleus. The occluding element is arranged so as to selectively occlude the narrowing of cross-section of the second expansion element27. One variant provides for the occluding element to be arranged so as to occlude the main channel28.

In use, when the coil is not supplied with current, the spring keeps the occluding element in the position occluding the narrowing of the second expansion element27.

When the coil is supplied with current, the ferrous nucleus is attracted by the coil until overcoming the force of the spring and determining a sufficient movement of the occluding element to free the narrowing of the second expansion element27.

One variant (not illustrated) provides the regulating valve29to be configured to make a fine regulation of the flow, rate of refrigerating fluid supplied to the second portion. For example, the regulating valve29may be a variable regulating valve.

Preferably, the second main channel28extends along a second serpentine path, which is preferably flat, and has a cross-section increasing along the flow direction of the refrigerating fluid.

Thereby, the expansion of the fluid is continuous along the second main channel28. The heat removed from the refrigerating fluid causes the temperature of the refrigerating fluid to increase. However, such rising of temperature is compensated for by the continuous expansion of the fluid along the second main channel28. Thereby, the temperature along the second main channel28is substantially kept constant.

Preferably, the second expansion element27and the second main channel28are wholly housed in radiator17, while the second inlet channel26and the main body30of the second regulating valve29are arranged outside of radiator17.

Preferably, radiator17is defined by two semi-shells32,33coupled to each other.

The semi-shell33is configured to be coupled, in use, to the frequency converter12. In particular, the semi-shell33is provided with a face34adapted to be coupled to the frequency converter12.

One variant (not illustrated) provides the semi-shells32and33to be shaped so as to define suitable seats for housing the first main channel22and the second main channel28.

A further variant provides the semi-shells32and33to be shaped so as to define, when coupled, the first main channel22and the second main channel28.

In the non-limiting embodiment herein described and illustrated, the first regulating valve23and the second regulating valve29are solenoid valves, the supply of which is regulated by a device for controlling (not illustrated in the accompanying drawings for simplicity) the cooling device13.

The control device is preferably configured to regulate the supply of the first regulating valve23and of the second regulating valve29on the basis of at least one signal indicative of the temperature of the frequency converter12.

With reference toFIG. 3, the frequency converter12is provided with a first temperature sensor38arranged along a first region of the frequency converter12, which is arranged under the first portion18of the cooling device13, and with at least a second temperature sensor39arranged along a second region of the frequency converter12, which is arranged under the second portion19of the cooling device13.

The control device is configured to control the opening of the first regulating valve23when the temperature detected by the first temperature sensor38exceeds a first threshold value, and to control the opening of the second regulating valve29when the temperature detected by the second temperature sensor39exceeds a second threshold value.

One variant (not illustrated) of the present invention provides more than two temperature sensors distributed in the frequency converter12and which supply the control device with the data acquired. Advantageously, the cooling device12according to the present invention is configured so as to minimize the quantity of refrigerating fluid used to cool the frequency converter12.

Moreover, according to the present invention, the refrigerating fluid supplied to the cooling device13is drawn downstream of condenser3of the refrigerating or conditioning plant1. Minimizing the flow rate of a refrigerating fluid therefore determines increasing the total efficiency of the refrigerating or conditioning plant1with apparent economic and energy advantages.

Due to the present invention, the quantity of refrigerating fluid drawn by the refrigerating or conditioning plant1is equal to approximately 1% of the average flow rate circulating in the refrigerating or conditioning plant1. Moreover, such a quantity is drawn only when needed due to the presence of the regulating means.

Devices of the known art instead continuously draw a significant quantity of the average flow rate circulating in the refrigerating or conditioning plant1, thus reducing the efficiency thereof.

Furthermore, the division of the thermal exchange element16into a first portion18and into a second portion19, which are independently supplied, allows the cooling of the frequency converter12to be diversified according to needs.

This avoids the over-cooling of the components of the frequency converter12which typically overheat less, and the under-cooling of components which are typically very hot.

Due to the control of the refrigerating fluid flow rate in the cooling device13, it is therefore possible to avoid the creation of condensate in the frequency converter12essentially due to excess cooling.

In conclusion, by accurately controlling the operating temperature of all electric components, not only is the efficiency increased of the frequency converter, but also the reliability thereof.

Finally, it is apparent that modifications and variants may be made to the cooling device, to the converter assembly and to the refrigerating or conditioning plant without departing from the scope of the appended claims.