Patent ID: 12250796

DESCRIPTION OF EMBODIMENTS

A power conversion apparatus according to embodiments of the present disclosure is described in detail below with reference to the accompanying drawings. In the drawings, the components identical or corresponding to each other are provided with the same reference symbol.

Embodiment 1

A power conversion apparatus according to Embodiment 1 is described below focusing on an exemplary self-cooled power conversion apparatus installed on the roof of a railway vehicle to cool electronic components using traveling wind.

A power conversion apparatus1illustrated inFIG.1converts DC power fed from a power source, which is not illustrated, into three-phase AC power to be fed to a motor M1, which is a load, and then feeds the three-phase AC power to the motor M1. A typical example of the power source is a current collector to acquire electric power from an overhead wire. The motor M1is a three-phase induction motor, for example.

In detail, the power conversion apparatus1includes a primary terminal31aconnected to the power source, a primary terminal31bthat is grounded, a filter capacitor FC1of which the ends are connected to the respective primary terminals31aand31bto remove ripples, and a power converter32to convert the DC power fed from the power source into three-phase AC power and feed the converted power to the motor M1. The power converter32includes switching elements33aand33bcorresponding to the U phase, switching elements33cand33dcorresponding to the V phase, and switching elements33eand33fcorresponding to the W phase. The switching elements33ato33fare turned on or off by a switching controller, which is not illustrated, so that the power converter32converts the DC power fed from the power source into three-phase AC power and feeds the converted power to the motor M1.

As illustrated inFIG.2, the power conversion apparatus1is installed on a roof100aof a vehicle100. In detail, the power conversion apparatus1is mounted on the top end in the vertical direction of the roof100awhile the vehicle100is horizontally oriented. InFIG.2, the X axis indicates the traveling direction of the vehicle100. In other words, the vehicle100runs toward the positive side in the X-axis direction or the negative side in the X-axis direction. The Y axis indicates the width direction of the vehicle100, in other words, the lengthwise direction of railroad ties. The Z axis is orthogonal to each of the X and Y axes. The Z axis indicates the vertical direction while the vehicle100is horizontally oriented.

The power conversion apparatus1is installed on the roof100aof the vehicle100and includes a housing10to accommodate electronic components11, which is described below, a cooling device12, which is described below, mounted on the housing10, and a cover20disposed over the cooling device12. The electronic components11indicate the switching elements33ato33fand any heat emitter, such as diode or thyristor, included in the power converter32inFIG.1.

As illustrated inFIG.3andFIG.4, which is a sectional view taken along the line A-A ofFIG.3, the housing10accommodates the electronic components11and has an opening10aon the top in the vertical direction. The opening10ais closed by a heat-receiving block13of the cooling device12, which is described below. The closing of the opening10aby the heat-receiving block13suppresses the ambient air, water, dust, and other contaminants entering the housing10. In Embodiment 1, the housing10has the opening10apenetrating through the housing10in the Z-axis direction while the vehicle100is horizontally oriented.

The housing10is preferably attached on the roof100asuch that the housing10can be attached to and detached from the roof100ain the vertical direction while the vehicle100is horizontally oriented. Since the housing10is attachable and detachable in the vertical direction, detachment of the housing10from the roof100afor maintenance of the power conversion apparatus1does not require detachment of electronic equipment surrounding the power conversion apparatus1, and can thus be readily completed. Also, attachment of the housing10to the roof100adoes not require detachment of the electronic equipment surrounding the power conversion apparatus1, and can thus be readily completed.

The electronic components11are mounted on a first main surface13aof the heat-receiving block13included in the cooling device12. The electronic components11emit heat in response to energization and transfer the heat to the heat-receiving block13, as is described in detail below.

The cooling device12includes the heat-receiving block13provided with the electronic components11, and one or more heat pipes14that are partially fixed at the heat-receiving block13and extend in a direction away from the heat-receiving block13. Each of the heat pipes14accommodates refrigerant. The cooling device12is preferably further provided with one or more fins15fixed on the outer surfaces of the heat pipes14. In Embodiment 1, the cooling device12includes the heat-receiving block13, the one or more heat pipes14, and the one or more fins15.

The cooling device12and the electronic components11mounted on the heat-receiving block13of the cooling device12are included in a unit40, which is preferably attached to the housing10such that the unit40can be attached to and detached from the housing10in the vertical direction while the vehicle100is horizontally oriented. In detail, the unit40includes the heat-receiving block13, the one or more heat pipes14, the one or more fins15, and the electronic components11mounted on the heat-receiving block13. Since the unit40is attachable and detachable in the vertical direction, detachment of the unit40from the housing10for maintenance of the unit40does not require detachment of the electronic equipment surrounding the power conversion apparatus1, and can thus be readily completed. Also, attachment of the unit40to the housing10does not require detachment of the electronic equipment surrounding the power conversion apparatus1, and can thus be readily completed.

The top end in the vertical direction of the cooling device12is preferably located higher than the top end in the vertical direction of the electronic equipment surrounding the power conversion apparatus1while the vehicle100is horizontally oriented. This arrangement, in which the top end in the vertical direction of the cooling device12is higher than the top end in the vertical direction of the surrounding electronic equipment, can improve the cooling efficiency of the power conversion apparatus1.

The individual components of the cooling device12having the above-described configuration are described below focusing on an exemplary cooling device12including eight heat pipes14.

The heat-receiving block13has the first main surface13aand a second main surface13bthat face the opposite sides in the Z-axis direction. The electronic components11are attached to the first main surface13a. The heat pipes14are attached to the second main surface13b. In detail, the heat pipes14are inserted and fixed in grooves formed on the second main surface13b. The heat-receiving block13is attached to the housing10and thus closes the opening10a. The heat-receiving block13is made of a material having a high thermal conductivity, for example, a metal, such as copper or aluminum.

The heat pipes14are inserted in the respective grooves on the second main surface13bof the heat-receiving block13and thus fixed at the heat-receiving block13. The heat pipes14transfer heat received from the electronic components11via the heat-receiving block13to traveling wind A1, which is described below, generated as the vehicle100travels. The heat pipes14have a sufficiently high thermal conductivity of, for example, 5,000 W/mK. Each of the heat pipes14rapidly transfers heat received from one end fixed at the heat-receiving block13to the other end and is therefore capable of efficient transfer of heat to the ambient air.

The structure of each of the heat pipes14is described in detail below. Each heat pipe14has a header portion14aand a plurality of branch portions14bin communication with the header portion14a. In detail, the heat pipe14has a single header portion14aand four branch portions14b. The header portion14ais inserted in each groove on the second main surface13bof the heat-receiving block13, and fixed at the heat-receiving block13by any fixing procedure, such as bonding with an adhesive or soldering. The header portion14ais fixed at the heat-receiving block13while being partially exposed from the heat-receiving block13. The header portion14ais made of a material having a high thermal conductivity, for example, a metal, such as copper or aluminum.

The branch portions14bare fixed at the header portion14aby a procedure, such as welding or soldering, and are in communication with the header portion14a. The branch portions14bextend in a direction away from the heat-receiving block13, in detail, a direction away from the second main surface13b. In Embodiment 1, the branch portions14bextend in the Z-axis direction. The branch portions14bare made of a material having a high thermal conductivity, for example, a metal, such as copper or aluminum.

Each of the heat pipes14accommodates refrigerant. The refrigerant is in a gas-liquid two-phase state at an ordinary temperature. The refrigerant is made of a substance, such as water, evaporated when receiving heat from the electronic components11, and condensed into liquid when discharging heat to the air around the cooling device12via the heat pipes14and the fins15, which are described below.

The individual fins15are fixed on the outer surfaces of the heat pipes14. In detail, each of the fins15has through holes and fixed at the branch portions14bwhile the branch portions14bextend through the respective through holes. The fins15are made of a material having a high thermal conductivity, for example, a metal, such as copper or aluminum. In Embodiment 1, the fins15are made of flat-plate members, arranged with spaces therebetween in the Z-axis direction, and fixed at the branch portions14b.

The cover20is attached to the housing10and disposed over the cooling device12. The cover20has any number of vents20ahaving any shape on the two surfaces intersecting the traveling direction of the vehicle100. In detail, the two surfaces of the cover20orthogonal to the X axis has the vents20athat penetrate through the cover20in the X-axis direction.

A mechanism for cooling the electronic components11in the power conversion apparatus1having the above-described configuration is described below. When the electronic components11emit heat in response to energization of the power converter32during running of the vehicle100, the heat is transferred from the electronic components11via the heat-receiving block13and each of the header portions14ato refrigerant. The transferred heat raises the temperature of the refrigerant and evaporates a part of the refrigerant. The evaporated refrigerant flows from the header portions14ainto the branch portions14bvia their proximal ends, and travels inside the branch portions14btoward their distal ends. In other words, the evaporated refrigerant travels inside the heat pipes14toward the positive side in the Z-axis direction.

During running of the vehicle100, the traveling wind A1generated as the vehicle100travels flows into the cover20via the vents20aon one surface of the cover20. For example, as the vehicle100travels toward the positive side in the X-axis direction, the traveling wind A1toward the negative side in the X-axis direction is generated and enters the cover20via the vents20aformed on one surface of the cover20, as illustrated inFIG.3. The traveling wind A1that has entered the cover20flows toward the negative side in the X-axis direction while coming into contact with the cooling device12, in detail, the branch portions14band the fins15. The traveling wind A1then exits the cover20via the vents20aformed on the other surface of the cover20.

While the refrigerant is traveling inside the branch portions14btoward the distal ends of the branch portions14bas described above, the heat is transferred from the refrigerant via the branch portions14band the fins15to the traveling wind A1. The heat discharge from the refrigerant lowers the temperature of the refrigerant. The refrigerant is accordingly condensed into liquid. The refrigerant in the liquid state flows toward the proximal ends of the branch portions14band returns to the header portion14a. In other words, the refrigerant in the liquid state flows inside the branch portions14btoward the negative side in the Z-axis direction and returns to the header portion14a. When the refrigerant that has condensed and returned to the header portion14areceives the heat from the electronic components11via the heat-receiving block13, the refrigerant is evaporated again, flows into the branch portions14b, and then travels toward the distal ends of the branch portions14b, in other words, travels toward the positive side in the Z-axis direction. The refrigerant thus repeats the above-described evaporation and condensation and thereby circulates, so that the heat emitted from the electronic components11is discharged to the traveling wind A1, resulting in cooling of the electronic components11.

When the heat emitted from the electronic components11is transferred from the electronic components11via the heat-receiving block13and the header portions14ato the refrigerant, then the refrigerant that has not been evaporated, that is, the refrigerant in the liquid state has internal temperature differences and generates convection. The convection allows the refrigerant to diffuse and transfer the heat from the electronic components11in the X-axis direction, leading to efficient cooling of the electronic components11.

The above-described circulation and convection of the refrigerant can achieve cooling of the electronic components11.

In order to improve the cooling efficiency of the power conversion apparatus1, the branch portions14bare preferably extended as long as possible within the vehicle gauge. The vehicle gauge means the maximum dimensions of the vehicle100in the section orthogonal to the traveling direction of the vehicle100, that is, in the YZ plane. In other words, the vehicle100and the components installed in the vehicle100are located within the vehicle gauge in the YZ plane.

The vehicle gauge in the Z-axis direction may vary depending on the position in the Y-axis direction. The vehicle gauge in the Z-axis direction corresponds to the maximum dimension of the vehicle100in the Z-axis direction in the YZ plane. For example, the maximum height of the vehicle100at the center in the Y-axis direction is higher than the maximum height of the vehicle100at the ends in the Y-axis direction. In this case, the top ends in the vertical direction of the branch portions14bat the center in the Y-axis direction are located higher than the top ends in the vertical direction of the branch portions14bat the ends in the Y-axis direction, while the vehicle100is horizontally oriented. This configuration allows the branch portions14bto be extended as long as possible within the vehicle gauge, thereby improving the cooling efficiency of the power conversion apparatus1.

Also, the fins15are preferably expanded as large as possible within the vehicle gauge. The vehicle gauge in the Y-axis direction may vary depending on the position in the Z-axis direction. The vehicle gauge in the Y-axis direction corresponds to the maximum dimension of the vehicle100in the Y-axis direction in the YZ plane. For example, above the roof100a, the vehicle gauge in the Y-axis direction has a narrower width at a higher position in the Z-axis direction. In this case, a length W1in the Y-axis direction of the fin15disposed at a higher position in the vertical direction is shorter than a length W2in the Y-axis direction of the fin15disposed at a lower position in the vertical direction. This configuration allows the fins15to be expanded as large as possible within the vehicle gauge, thereby improving the cooling efficiency of the power conversion apparatus1.

In order to extend the branch portions14bas long as possible and expand the fins15as large as possible within the vehicle gauge, the cover20preferably has a shape along the vehicle gauge.

Since the traveling wind A1receives heat from the heat pipes14and the fins15as described above, the traveling wind A1at a downstream site has a higher temperature than that at an upstream site. In other words, the heat pipe14at a posterior site in the traveling direction of the vehicle100has lower cooling efficiency than that of the heat pipe14at an anterior site in the traveling direction of the vehicle100. This phenomenon may cause temperature differences in the electronic components11depending on their positions relative to the heat-receiving block13. The header portions14atherefore preferably extend in the flowing direction of the traveling wind A1, that is, in the X-axis direction. Because of the header portions14aextending in the X-axis direction, convection of the refrigerant in the liquid state diffuses and transfers heat from the electronic components11in the X-axis direction and thus reduces the temperature differences in the electronic components11.

The main surfaces of the individual fins15preferably extend in the flowing direction of the traveling wind A1, that is, in the X-axis direction. In this case, the traveling wind A1that has been introduced via the vents20acan smoothly flow along the fins15, leading to improvement of the cooling efficiency of the power conversion apparatus1. For example, in Embodiment 1, the main surfaces of the individual fins15extend in the X-axis direction, and the fins15are horizontally arranged while the vehicle100is horizontally oriented.

The ratio of the length in the Y-axis direction of at least any one of the fins15to a vehicle width W3, which is described below, of the vehicle100is preferably equal to or higher than a threshold value. The threshold value is determined depending on the cooling capacity required in the cooling device12, and is 0.5, for example. In Embodiment 1, the ratio of the length W2in the Y-axis direction of the fin15at a lower position in the vertical direction to the vehicle width W3of the vehicle100is equal to or higher than 0.5, as illustrated inFIG.4. Since the ratio of the length in the Y-axis direction of the fin15to the vehicle width W3of the vehicle100is defined to be equal to or higher than the threshold value, the fin15is allowed to have a larger size than that of a fin included in a cooling device mounted on a side surface of an existing power conversion apparatus installed under the floor of a railway vehicle. The fin15having a larger size can achieve more efficient heat transfer to the traveling wind A1. The power conversion apparatus1therefore has higher cooling efficiency than those of existing power conversion apparatuses.

In the case where the main surface of the fin15is designed to have the area identical to that of a fin included in a cooling device mounted on a side surface of an existing power conversion apparatus installed under the floor of a railway vehicle, the length in the X-axis direction of the fin15can be reduced by extending the length in the Y-axis direction of the fin15. A reduction in the length of the fin15in the X-axis direction, that is, in the flowing direction of the traveling wind A1leads to a decrease in the pressure loss, so that a larger amount of the traveling wind A1is allowed to flow between the fins15. This configuration can accordingly improve the cooling efficiency of the power conversion apparatus1including the fin15having the main surface area identical to that of an existing fin.

As described above, the power conversion apparatus1according to Embodiment 1 is installed on the roof100aof the vehicle100, and includes the heat pipes14extending in a direction away from the heat-receiving block13that closes the opening10aon the top in the vertical direction of the housing10, and the fins15fixed at the heat pipes14. The installation of the heat pipes14and the fins15on the roof100aof the vehicle100can achieve efficient transfer of heat generated in the electronic components11to the traveling wind A1. This configuration can therefore improve the cooling capacity of the power conversion apparatus1.

In the case of a small number of powered vehicles among coupled railway vehicles, in other words, in the case of a centralized train system, the powered vehicles include high-output motors. That is, a power conversion apparatus to feed electric power to each motor also has a higher output and thus emits a larger amount of heat. In an existing centralized train system, the power conversion apparatus is cooled by forcible wind supply from a blower. In contrast, in the power conversion apparatus1according to Embodiment 1, the electronic components11of the power conversion apparatus1can be cooled using the traveling wind A1without a component, such as fan or blower, even in a centralized train system.

Embodiment 2

The power conversion apparatus1may also be installed at a place other than the top end in the vertical direction of the roof100aof the vehicle100. The description of Embodiment 2 is directed to an exemplary power conversion apparatus1installed in an accommodator100bformed on the roof100aof the vehicle100. In Embodiment 2, the power conversion apparatus1and the accommodator100bto accommodate the power conversion apparatus1are described below focusing on an exemplary accommodator100bintegrated with the roof100a.

As illustrated inFIG.5, the roof100aof the vehicle100is provided with the accommodator100b, which is a recess having a top opening in the vertical direction. In detail, the top surface in the vertical direction of the accommodator100bis open while the vehicle100is horizontally oriented. The accommodator100baccommodates the housing10of the power conversion apparatus1. In detail, the bottom of the housing10is fixed on the bottom of the accommodator100b. The components of the power conversion apparatus1and the mechanism for cooling the electronic components11are identical to those in Embodiment 1.

The structure of the power conversion apparatus1for cooling the electronic components11using the traveling wind A1is described in detail below.

The top end in the vertical direction of at least any one of the heat pipes14is located higher than the top end in the vertical direction of the roof100awhile the vehicle100is horizontally oriented. As illustrated inFIGS.6and7, the top ends in the vertical direction of the individual heat pipes14are located higher than the top end in the vertical direction of the roof100ain Embodiment 2. The traveling wind A1can thus come into contact with these heat pipes14regardless of the installation of the power conversion apparatus1in the accommodator100b, and can thereby cool the electronic components11.

In addition, at least any one of the fins15is located higher than the top end in the vertical direction of the roof100awhile the vehicle100is horizontally oriented. As illustrated inFIGS.6and7, the individual fins15are located higher than the top end in the vertical direction of the roof100ain Embodiment 2. The traveling wind A1can thus come into contact with these fins15regardless of the installation of the power conversion apparatus1in the accommodator100b, and can thereby cool the electronic components11.

As described above, the power conversion apparatus1according to Embodiment 2 is installed in the accommodator100bformed on the roof100aof the vehicle100but still can cool the electronic components11. In an exemplary case of the vehicle100having a large size relative to the vehicle gauge, the accommodator100bon the roof100acan allow the power conversion apparatus1to be installed on the roof100aand cool the electronic components11.

Embodiment 3

The description of Embodiment 3 is directed to a power conversion apparatus including wind guiding members21in order to introduce the traveling wind A1more effectively into the cover20.

As illustrated inFIG.8, the power conversion apparatus1includes the wind guiding members21disposed adjacent to the respective outer surfaces of the housing10intersecting the traveling direction of the vehicle100, that is, the X-axis direction. The wind guiding members21guide the traveling wind A1to the cooling device12. In detail, the wind guiding members21guide the traveling wind A1to flow via the vents20aon the cover20to the heat pipes14and the fins15. In Embodiment 3, two wind guiding members21are arranged in the X-axis direction on both sides of the housing10.

The shape of the wind guiding members21is described in detail below. As illustrated inFIG.9, the wind guiding members21each have a shape of a tube having a through hole extending in the X-axis direction and lacking a part of the side surface.FIG.9is a sectional view taken along the line C-C ofFIG.8. In detail, the wind guiding member21has a shape of a square tube lacking one of the side surfaces. The wind guiding member21is mounted on the roof100asuch that the missing side surface of the tube faces the roof100a. InFIG.9, the missing side surface of the tubular wind guiding member21is mounted on the bottom of the accommodator100bformed on the roof100a. The wind guiding members21mounted on the roof100aas described above define an air passage21aagainst the roof100ato guide the traveling wind A1to the cooling device12. In detail, the wind guiding members21define the air passage21aextending in the X-axis direction in order to guide the traveling wind A1via the vents20aon the cover20to the heat pipes14and the fins15.

The end face of the air passage21adefined by the wind guiding members21adjacent to the housing10preferably has a smaller area than that of the end face of the air passage21adistant from the housing10. This configuration can efficiently guide the traveling wind A1flowing along the roof100a, to the heat pipes14and the fins15.

As described above, the power conversion apparatus1according to Embodiment 3 is provided with the wind guiding members21and can thereby efficiently guide the traveling wind A1to the cooling device12.

The two wind guiding members21arranged in the X-axis direction on both sides of the housing10can efficiently guide the traveling wind A1to the cooling device12in both cases of the vehicle100running toward the positive side in the X-axis direction and the vehicle100running toward the negative side in the X-axis direction.

The above-described embodiments may be combined with each other, and some of the components in the embodiments may be modified or omitted as appropriate.

For example, the power conversion apparatus1according to Embodiment 1 may include two wind guiding members21arranged in the X-axis direction on both sides of the housing10. In other words, the wind guiding members21may be mounted on the top end in the vertical direction of the roof100awhile the vehicle100is horizontally oriented.

The electric power fed to the power conversion apparatus1is not necessarily DC power. For example, the power conversion apparatus1may also be a converter to convert AC power into DC power. Also, the electric power fed from the power conversion apparatus1to the load is not necessarily three-phase AC power. For example, the power conversion apparatus1may also feed DC power to the load, which is a DC motor.

The motor M1is not necessarily the three-phase induction motor and may also be a synchronous motor or DC motor, for example. The power conversion apparatus1is not necessarily the self-cooled power conversion apparatus to feed electric power to the motor M1. Another example of the load to be fed with electric power from the power conversion apparatus1is any electric equipment, such as lighting equipment or air conditioner, which consumes electric power.

The power conversion apparatus1may be installed on not only the railway vehicle but also any moving body, such as trolleybus or tram, which accompanies the traveling wind A1.

The housing10may have any shape provided that the housing10can accommodate the electronic components11therein and can be installed on the roof100a. For example, the top surface in the vertical direction of the housing10may be inclined from the horizontal plane while the vehicle100is horizontally oriented. In an exemplary case where the traveling direction of a vehicle is constant, the housing10preferably has the top surface declining toward the front side in the traveling direction of the vehicle. This configuration can more efficiently bring the traveling wind A1into contact with the heat pipes14and the fins15.

The heat-receiving block13may be made of a single plate member or a combination of multiple plate members. The heat-receiving block13made of a single plate member can simplify the process of fabricating the power conversion apparatus1and increase the air tightness of the housing10.

The heat pipes14may have any shape provided that circulation of the refrigerant accommodated in the heat pipes14can cool the electronic components11. For example, a power conversion apparatus2illustrated inFIG.10includes heat pipes22bent into an L-shape. A part of each of the heat pipes22extends in the X-axis direction and another part extends in the Z-axis direction. The power conversion apparatus2may also be installed in the accommodator100bformed on the roof100a, as in Embodiment 2.

For another example, the heat pipe14may have a U-shape or ring shape. The section of the heat pipe14orthogonal to its extending direction does not necessarily have a circular shape and may also have a flattened shape. In detail, the section of each of the header portion14aand the branch portion14borthogonal to each extending direction may have a circular or flattened shape. The flattened shape indicates a shape formed by narrowing the width of a part of the circular shape than the original width and encompasses elliptical, streamline, and elongated circular shapes. The elongated circular shape indicates a shape defined by two circles having the same diameter and the straight lines connecting the contours of the circles with each other.

For another example, the heat pipes14may be in communication with the respective grooves formed in the heat-receiving block13. In this case, each of the heat pipes14have a shape of a tube with a closed end.

The number of heat pipes14described above is a mere example and may be arbitrarily varied. Furthermore, the number of header portions14aand the number of branch portions14bfixed at each of the header portions14adescribed above are mere examples and may be arbitrarily varied.

The positions of the top ends in the vertical direction of the heat pipes14may be mutually different as in the above-described embodiments or identical to each other.

The number of fins15described above is a mere example and may be arbitrarily varied.

The lengths in the Y-axis direction of the fins15may be mutually different as in the above-described embodiments or identical to each other.

The shape of the fins15described above is a mere example and may be arbitrarily modified. For example, the fin15may be made of a flat-plate member as in the above-described embodiments or a bent-plate member.

In the above-described embodiments, the fins15each of which is made of a single plate member are arranged in the Z-axis direction. The shape of the fins15described above is a mere example and the fins15may each be made of multiple plate members. For example, as illustrated inFIG.11andFIG.12, which is a sectional view taken along the line D-D ofFIG.11, the cooling device12included in a power conversion apparatus3includes multiple fins23. Each of the fins23is made of flat-plate members23aand23b.

The fins15may be made of the identical member, or at least any one of the fins15may be made of a member different from that of the other fins15. In the case where at least any one of the fins15is made of a member different from that of the other fins15, at least any one of the fins15has a thermal conductivity different from that of the other fins15. In this case, the fin15at an upper position in the vertical direction preferably has a higher thermal conductivity than that of the fin15at a lower position in the vertical direction. For example, the fin15at an upper position in the vertical direction may be made of copper while the fin15at a lower position in the vertical direction may be made of aluminum.

The fin15at an upper position in the vertical direction can readily come into contact with the traveling wind A1regardless of other equipment around the power conversion apparatus1. That is, the cooling efficiency of the power conversion apparatus1can be improved by increasing the thermal conductivity of the fin15at the upper position in the vertical direction.

The cover20may have any shape provided that the cover20is disposed over the cooling device12and can introduce the traveling wind A1into the cover20. For example, the cover20may have a curved top surface in the vertical direction. For another example, the cover20may have a flat top surface in the vertical direction. The cover20preferably has a shape that maximizes the internal space within the vehicle gauge.

The wind guiding members21do not necessarily have a shape of a square tube lacking one of the side surfaces and may also have any shape provided that the wind members21can guide the traveling wind A1to the cooling device12. For example, the wind guiding members21may have a hollow cylindrical shape lacking a part of the side surface. For another example, the wind guiding member21may have a shape of a tube the side surfaces of which are partially fixed on the roof100aand which has a polygonal section.

The wind guiding members21may be disposed apart from the housing10and the cover20as illustrated in the embodiments, or may be disposed in contact with at least either of the housing10and the cover20.

Any number of wind guiding members21may be provided. In an exemplary case where the traveling direction of a vehicle is constant, a single wind guiding member21may be provided on the front of the vehicle in the traveling direction.

The switching elements33ato33fmay include a wide bandgap semiconductor. The wide bandgap semiconductor contains a silicon carbide, gallium nitride martial, or diamond, for example.

The plane of the opening of the accommodator100bmay be in parallel to the horizontal plane while the vehicle100is horizontally oriented as in Embodiment 2, or inclined from the horizontal plane while the vehicle100is horizontally oriented. The accommodator100bmay be independent from the roof100a. For example, as illustrated inFIG.13, the accommodator100bmay be replaced with a pair of on-roof covers100cthat face each other in the width direction. The main surfaces of the on-roof covers100cface each other in the width direction. The on-roof covers100cmay each be a plate member having a flat main surface or a plate member having a curved main surface.

Each of the power conversion apparatuses1to3may further include a sealing member that surrounds the opening10aand is in contact with the housing10and the heat-receiving block13. The sealing member can improve the air tightness of the housing10.

The foregoing describes some example embodiments for explanatory purposes. Although the foregoing discussion has presented specific embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. This detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined only by the included claims, along with the full range of equivalents to which such claims are entitled.

REFERENCE SIGNS LIST

1,2,3Power conversion apparatus10Housing10aOpening11Electronic component12Cooling device13Heat-receiving block13aFirst main surface13bSecond main surface14,22Heat pipe14aHeader portion14bBranch portion15,23Fin20Cover20aVent21Wind guiding member21aAir passage23a,23bFlat-plate member31a,31bPrimary terminal32Power converter33a,33b,33c,33d,33e,33fSwitching element40Unit100Vehicle100aRoof100bAccommodator100cOn-roof coverA1Traveling windFC1Filter capacitorM1MotorW1, W2LengthW3Vehicle width