Power module with cooling system

Abstract

To provide a power module by which un-conveniences of a conventional technique are corrected by changing a cooling system without degrading performances of the system.SOLUTION: This invention is related to a power module (12) for a railway vehicle and the module (12) has an electric current conversion unit (20), a closed circuit (28) of two-phases heat conduction fluid (30), a first heat exchanger (25) able to transfer heats of the heat conduction fluid to an air flow and a second heat exchanger (26) to transfer heats of a heat generation unit to the heat conduction fluid. The circuit of the heat conduction fluid has a main loop (32) and a secondary branch (34), both an inlet (40) and an exit (42) of the secondary branch depart from the first heat exchanger and are connected to the main loop, the inlet is arranged in a downstream side of the exit and the second heat exchanger (26) is arranged in the secondary branch.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric power module for a vehicle, in particular a railway vehicle, of the type comprising a heat-generating device responsible for the conversion of electric current, a closed circuit of a two-phase heat transfer fluid, a first heat exchanger capable of transferring heat of the heat transfer fluid to an air flow, and a second heat exchanger capable of transferring heat of the heat-generating device to the heat transfer fluid. [Background technology]

[0002] Such a power module with a cooling system is described in particular in document EP 2291067. The cooling system comprises in particular a tank of two-phase heat transfer fluid equipped with externally controlled heating and cooling means for supplying the second heat exchanger.

[0003] The device can adjust the pumped rate of heat transfer fluid in the circuit to vary the performance of the cooling system in response to heat dissipated by the power modules.

[0004] In such power modules, the circulation of the heat transfer fluid in the circuit is achieved by, for example, vaporizing the fluid in a second heat exchanger, but the operating temperature of the pump can approach 80°C, which may be too high for the power module's electronics.

[0005] Additionally, such cooling systems require the use of heat transfer fluids with high latent heat, a constraint that leads to the use of toxic fluids such as methanol. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] EP2291067 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to correct these disadvantages by modifying the cooling system without degrading the system's performance. [Means for solving the problem]

[0008] Therefore, the invention also relates to an electric power module of the aforementioned type, in which the circuit of the heat transfer fluid comprises a main loop and a secondary branch, the main loop comprising a first section and a second section connected to each other, a first heat exchanger arranged in the first section, the inlet and outlet of the secondary branch being connected to the second section of the main loop, the inlet being arranged in the second section downstream of the outlet along the direction of circulation of the heat transfer fluid in the main loop, and a second heat exchanger arranged in the secondary branch.

[0009] According to other advantageous aspects of the invention, the power module comprises any one or more of the following characteristics taken alone or in any technically possible combination: the second heat exchanger comprises at least one capillary evaporator through which a two-phase heat transfer fluid passes, said heat transfer fluid circulating in a closed circuit under the action of the pressure generated at the level of the gas-liquid interface in the or each capillary evaporator; - the or each capillary evaporator comprises a capillary wick capable of completely vaporizing the heat transfer fluid received in liquid state from the inlet of the second heat exchanger and delivering all of said heat transfer fluid in gaseous state to the outlet of said second heat exchanger. - The closed circuit is a capillary pumped loop without a mechanical pump for the circulation of the heat transfer fluid. The second heat exchanger is disposed on an inclined surface, and the inlet of the second heat exchanger is disposed above the outlet of the second heat exchanger. The inlet of the second heat exchanger is located lower than the inlet of the secondary branch. The heat transfer fluid is a fluorine-free compound, preferably acetone. - a first section of the main loop is connected to a plurality of second sections by a divider and a merger arranged at each end of the first section, the heat transfer fluid circuit comprises a plurality of secondary branches, each of the branches being connected to one of the second sections, and the power module comprises a plurality of second heat exchangers, each of the exchangers being arranged in one of the secondary branches.

[0010] The invention also relates to a drive box comprising a power module as described above.

[0011] The invention also relates to a railway vehicle comprising a drive line comprising an electric motor and a drive box as described above, said drive box preferably being located on the roof of said vehicle.

[0012] The invention will be better understood from reading the following description, given solely by way of non-limiting example, and with reference to the drawings in which: [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a partial schematic cross-sectional view of a railway vehicle equipped with a power module with a cooling device according to an embodiment of the present invention, seen from the front. [Figure 2] FIG. 2 is a schematic diagram of the cooling device of FIG. 1. [Figure 3] 3 is a schematic diagram of the cooling device of FIGS. 1 and 2 as viewed from above. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] 1 shows a railcar 10 equipped with a power module 12, i.e., a power converter. The railcar 10 may be, for example, a motor vehicle of a train of passenger or freight cars. The railcar 10 includes a driveline electric motor (not shown) that is powered by the power module 12.

[0015] The rail vehicle 10 notably comprises a drive box 14 located on the roof of said vehicle as shown in FIG.

[0016] Consider an orthonormal basis (X, Y, Z) in which the Z direction corresponds to the vertical line, the X direction corresponds to the longitudinal direction of movement of the railcar 10, and the Y direction corresponds to the horizontal transverse direction.

[0017] The exterior surface of the drive box 14 is defined by a central panel 16 disposed generally in a plane (X, Y) and side panels 17 located on either side of the central panel 16. The side panels 17 are generally symmetrical to one another about the median plane (X, Y) of the railcar 10. Only one side panel 17 is shown in FIG. 1.

[0018] Each side panel 17 is angled so that the edge that meets the central panel 16 is higher than the opposite edge, giving the drive box 14 a conventional convex shape. For reference, the side panels are angled at an angle of 20° to 60° relative to the horizontal.

[0019] Drive box 14 also includes an interior structure having at least one inclined surface 18 generally parallel to and positioned below side panel 17. The space between side panel 17 and inclined surface 18 defines an interior compartment 19 of drive box 14.

[0020] The power module 12 comprises at least one conversion unit 20 capable of generating heat and a cooling device 22 for the at least one unit 20. Preferably, the power module 12 comprises a plurality of substantially identical conversion units 20, and the cooling device 22 is capable of cooling each of said units.

[0021] Preferably, the power module 12 further comprises at least one filter capacitor 24 electrically connected to the or each of the conversion units 20 .

[0022] The conversion unit 20 in particular comprises a plurality of semiconductor devices of the transistor type connected by connecting devices. Preferably, the semiconductor devices are insulated gate bipolar transistors (IGBTs). The IGBTs in particular have a switching function in the conversion unit 20.

[0023] The or at least one conversion unit 20 is preferably arranged in an internal compartment 19 of the drive box 14 .

[0024] The cooling device 22, shown schematically in Figure 2, comprises a first heat exchanger 25 and at least one second heat exchanger 26, and a closed fluid circuit 28 connecting the first exchanger 25 and the second exchanger 26. A two-phase heat transfer fluid 30 circulates in the fluid circuit 28.

[0025] The heat transfer fluid 30 is preferably a fluorine-free compound, more preferably acetone. Methanol can also be used. Hydrofluoroolefin (HFO)-based fluorinated gases R-1233zd(E) gas and R-1336mzz(Z) gas can also be used.

[0026] The first heat exchanger 25 is capable of exchanging heat between the heat transfer fluid 30 of the fluid circuit 28 and the outside air, in particular the air currents generated by the movement of the rail vehicle 10. This is called mixed convection. In a variant, the heat exchange between the heat transfer fluid 30 of the fluid circuit 28 and the outside air is carried out by natural convection (due to gradient phenomena) or forced convection (due to artificial circulation of the fluid).

[0027] The first heat exchanger 25 is, for example, a finned radiator. The first heat exchanger is preferably arranged in the center of the drive box 14 along the transverse direction Y, i.e. below the central panel 16.

[0028] The second heat exchanger 26 is capable of exchanging heat between the conversion unit 20 and the heat transfer fluid 30 of the fluid circuit 28. The second heat exchanger 26 is therefore arranged in thermal contact with the conversion unit 20. Preferably, the IGBTs of the conversion unit are in thermal contact with the second heat exchanger 26.

[0029] Effective thermal contact between the IGBTs and the second heat exchanger 26 is achieved through a thermally conductive interface, such as a dry interface type, in particular made of graphite.

[0030] The second heat exchanger 26 is preferably located in the interior compartment 19 of the drive box 14, for example against the inclined surface 18. The preferred construction of the second heat exchanger 26 will be described in more detail below.

[0031] Fluid circuit 28 specifically comprises a main loop 32 and a secondary branch 34. Main loop 32 comprises a first section 36 and a second section 37 connected to each other.

[0032] The first heat exchanger 25 is disposed in a first section 36 of the main loop 32 and includes an inlet 38 and an outlet 39. Preferably, the outlet 39 is located lower than the inlet 38 relative to the vertical line.

[0033] The secondary branch 34 is connected to a second portion 37, also called an injector, of the main loop 32. More specifically, an inlet 40 and an outlet 42 of the secondary branch are connected to the injector 37, with the inlet 40 being located downstream of the outlet 42 along the direction of circulation of the heat transfer fluid in the main loop 32.

[0034] The second heat exchanger 26 is disposed in the secondary branch 34 .

[0035] The outlet 42 of the secondary branch 34 is preferably lower relative to the vertical line than the inlet 40. The position of the inlet 40 of the secondary branch 34 is preferably lower relative to the vertical line than the junction 46 and / or the inlet 38 of the first heat exchanger 25.

[0036] Preferably, the first section 36 of the main loop 32 is connected to the injector 37 by a flow divider 44 and a flow junction 46 arranged at each end of the first section 36. More preferably, the fluid circuit 28 comprises a plurality of injectors 37 connected to the first section 36 by the flow dividers 44 and the flow junction 46 and a plurality of secondary branches 34 each connected to the injector 37, and the cooling device 22 comprises a plurality of second heat exchangers 26 each arranged in one of the secondary branches 34. Each of the second heat exchangers 26 is arranged in thermal contact with the conversion unit 20 of the power module 12.

[0037] The second heat exchanger 26, shown in more detail in Figure 3, is described in more detail below. When a power module 12 includes multiple second heat exchangers 26, they are considered to be substantially identical.

[0038] The second heat exchanger 26 includes an inlet 50 , an outlet 52 , and at least one capillary evaporator 54 disposed between the inlet 50 and the outlet 52 .

[0039] Preferably, the inlet 50 is located at a higher vertical position than the outlet 52. In the embodiment shown in FIG.

[0040] More preferably, the inlet 40 of the secondary branch 34, the inlet 50 and outlet 52 of the second heat exchanger 26, and the outlet 42 of the secondary branch 34 are arranged in this order from top to bottom.

[0041] 3, the inlet 50 and outlet 52 are formed by a dividing pipe and a merging pipe, respectively, and the second heat exchanger 26 comprises a plurality of capillary evaporators 54 arranged in parallel. The number of capillary evaporators in the second heat exchanger 26 is preferably between one and three.

[0042] In the embodiment shown in FIG. 3, the second heat exchanger 26 further comprises an outer casing 55 that supports the capillary evaporator 54 .

[0043] Each capillary evaporator 54 has a square cross section and is elongated in shape extending generally along an axis 56, and comprises an outer frame 57, a capillary wick 58 housed within said outer frame, and an inner chamber 60 bounded by the capillary wick 58. In the illustrated embodiment, axis 56 lies generally in a (Y, Z) plane and is inclined relative to the vertical.

[0044] A first axial end of the internal chamber 60 is connected to a branch pipe forming the inlet 50 of the second heat exchanger 26. A second axial end of the internal chamber, lower than the first end, is closed by a capillary wick 58.

[0045] A first axial end of the outer frame 57 is closed by a capillary wick 58. A second end of the frame, which is lower than the first end, is connected to a junction pipe which forms the outlet 52 of the second heat exchanger 26.

[0046] The capillary wick 58 is formed from a porous material, more particularly a material that includes a meniscus (not shown) connecting the inner chamber 60 and the outer frame 57 .

[0047] As will be explained hereinafter, the capillary evaporator(s) 54 circulate the fluid 30 within the closed fluid circuit 28. Preferably, the fluid circuit 28 does not include a mechanical pump for circulating the heat transfer fluid 30, however, and the circulation is accomplished solely by the capillary evaporator(s) 54.

[0048] The operation of the power module 12 will now be described.

[0049] The electric motor of the drive line of the rail vehicle described above is operated to move the rail vehicle. In addition, at least one conversion unit 20 of the power module 12 is also operated. The components of the conversion unit, in particular the IGBTs, emit heat, which is dissipated by conduction through the housing 55 of the second heat exchanger 26 to the outer casing 57 of the capillary evaporator 54. The heat transfer fluid 30 then vaporizes at the level of the outer casing, thereby starting the pump formed by the capillary evaporator. This self-pressurization makes it possible to lower the onset temperature of thermosiphoning.

[0050] The heat transfer fluid 30 thereby enters the second heat exchanger 26 in liquid form at the level of the inlet 50, vaporizes while passing through the capillary wick 58 and leaves in vapor form at the level of the outlet 52 of said exchanger, thereby absorbing the heat given off by the conversion unit 20 through the second heat exchanger 26.

[0051] The vapor generated there then joins the outlet 42 of the secondary branch 34 located at the bottom of the fluid circuit 28. As a result, in the injector 37, gas bubbles 62 mix with the liquid heat transfer fluid 30 circulating in the main loop 32. The presence of the bubbles 62 helps the liquid to circulate upward from below towards the junction 46. The heat carried by the bubbles 62 also warms the liquid heat transfer fluid 30, which also favors its upward movement.

[0052] The two-phase heat transfer fluid 30 then enters the first section 36 of the fluid circuit 28 and reaches the inlet 38 of the first heat exchanger 25. At the level of the first exchanger, the heat transfer fluid 30 transfers heat to an air flow, such as that generated by the movement of a rail vehicle. The gas concentration in the heat transfer fluid 30 decreases, and the temperature of the fluid also decreases, which favors its downward movement towards the outlet 39 of the first heat exchanger 25.

[0053] The cooled heat transfer fluid 30 joins the injector 37 at the level of the flow divider 44 and then passes to the level of the outlet 42 of the above-mentioned secondary branch 34, thereby maintaining the circulation cycle of said fluid 30 in the circuit 28.

[0054] Thus, the main loop 32 of the fluid circuit 28 operates according to the thermosiphon principle, but the velocity of the fluid 30 is increased by the injection of gas bubbles 62 at the outlet 42 of the secondary branch 34 .

[0055] Compared to known capillary pumping systems such as that described in document EP 2291067, this increased fluid velocity allows the use of heat transfer fluids with lower latent heat without compromising the performance of the cooling device, thus allowing the use of fluids such as acetone as the heat transfer fluid 30, which are less toxic than methanol.

[0056] At the level of the inlet 40 of the secondary branch 34, a first portion of the fluid 30 remains in the injector 37, while a second portion of said fluid moves towards the second heat exchanger 26. Due to the inclined position of the second heat exchanger 26, gas bubbles 62 are unlikely to enter said second heat exchanger 26. Therefore, the heat transfer fluid 30 enters in liquid form into the inner chamber 60 of each capillary evaporator 54 and then vaporizes in the capillary wick 58.

[0057] Unlike the capillary evaporator described in document EP 2291067, the evaporation temperature of the heat transfer fluid 30 in the capillary wick 58 is not constant, but can vary within a range depending on the heat exchange conditions in the first exchanger 25.

[0058] Such a device makes it possible to dispense with the fluid tank described in document EP 2291067 and also with the actuation of the thermal control means of said tank. [Explanation of symbols]

[0059] 10 vehicles 12 Power Module 14 Drive box 16 Central Panel 17 Side Panel 18 Slope 19 Interior compartment 20 Conversion units, heat-generating equipment 22 Cooling device 24 filter capacitor 25 First heat exchanger 26 Second heat exchanger 28 Closed circuit 30 Heat Transfer Fluids 32 Main Loop 34 Secondary Branch 36 First Part 37 Second part, injector 38 Entrance 39 Exit 40 Entrance 42 Exit 44 Flow divider, flow pipe 46 Combiner, merge pipe 50 Entrance 52 Exit 54 Capillary evaporator 55 Exterior 56 axes 57 Outer Frame 58 Capillary core 62 Bubbles

Claims

1. A power module (12) for a vehicle (10), in particular a rail vehicle, comprising: a heat-generating device (20) that contributes to the transformation of the electric current; a closed circuit (28) of a two-phase heat transfer fluid (30); a first heat exchanger (25) capable of transferring the heat of said heat transfer fluid to an air stream; a second heat exchanger (26) capable of transferring heat from said heat-generating equipment to said heat transfer fluid; A power module (12) comprising: the circuit (28) of the heat transfer fluid (30) comprises a main loop (32) and a secondary branch (34), the main loop comprises a first section (36) and a second section (37) connected to each other, the first heat exchanger (25) being disposed in the first section; an inlet (40) and an outlet (42) of the secondary branch are connected to the second portion of the main loop, the inlet being located downstream of the outlet at the second portion along the direction of circulation of the heat transfer fluid in the main loop; A power module (12) characterized in that the second heat exchanger (26) is arranged in the secondary branch.

2. 2. The power module (12) of claim 1, wherein the second heat exchanger (26) comprises at least one capillary evaporator (54) through which the two-phase heat transfer fluid (30) passes, the heat transfer fluid circulating in the closed circuit under the action of a pressure generated at the level of a gas-liquid interface in the at least one capillary evaporator.

3. 3. The power module (12) of claim 2, wherein the at least one capillary evaporator (54) comprises a capillary wick (58) that completely vaporizes the heat transfer fluid (30) received in a liquid state from the inlet (50) of the second heat exchanger, and that is capable of delivering all of the heat transfer fluid in a gaseous state to the outlet (52) of the second heat exchanger.

4. 4. The power module (12) of claim 2 or 3, wherein the closed circuit (28) is a capillary pumping loop without a mechanical pump for circulating the heat transfer fluid.

5. 5. The power module (12) of claim 2, wherein the second heat exchanger (26) is disposed on an inclined surface and an inlet (50) of the second heat exchanger is disposed above an outlet (52) of the second heat exchanger.

6. The power module (12) of claim 5, wherein the inlet (50) of the second heat exchanger (26) is at a lower elevation than the inlet (40) of the secondary branch (34).

7. The power module (12) of any one of claims 1 to 6, wherein the heat transfer fluid (30) is a fluorine-free compound, preferably acetone.

8. 8. The power module (12) according to claim 1, wherein the first portion (36) of the main loop (32) is connected to a plurality of second portions (37) by a divider (44) and a merger (46) arranged at each end of the first portion, and the circuit (28) of the heat transfer fluid comprises a plurality of secondary branches (34), each of the branches being connected to one of the second portions (37). The power module (12) further comprises a plurality of second heat exchangers (26), each of the second heat exchangers being arranged in one of the secondary branches (34).

9. A drive box (14) for a railway vehicle comprising a power module (12) according to any one of claims 1 to 8.

10. A railway vehicle (10) comprising a drive line comprising an electric motor and a drive box (14) according to claim 9, said drive box being preferably located on the roof of said vehicle.

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