DESCRIPTION
Title of Invention
POWER CONVERSION DEVICE
Technical Field
[0001 ] The present disclosure relates to a power conversion device including an
electronic component subjected to forced air cooling.
Background Art
[0002] A power conversion device that converts power acquired from an overhead
line to supply the converted power to a motor or an in-vehicle device is mounted on a
roof of or under a floor of an electric railroad vehicle. The power conversion device
contains a power converter that converts input power by switching operation of a
semiconductor element and outputs a desired alternating-current power. Since the
semiconductor element generates heat during the switching operation, the power
conversion device is provided with a plate-fin or pin-fin heatsink for releasing heat
transferred from the semiconductor element. In order to improve cooling efficiency, the
heatsink is arranged at a location where the heatsink is subjected to external air. The
semiconductor element included in the power converter and the electronic component
included in an output controller outputting a control signal to the power converter are
arranged inside a housing of the vehicle not to be subjected to the external air in order to
suppress or prevent malfunctions of the semiconductor element and the electronic
component due to dust or moisture. As described above, a location of each component
of the power conversion device arranged is determined in accordance with the necessity
of cooling and the necessities of dust prevention and water proof.
[0003] In a power conversion system for an AC-DC dual current electric railroad
vehicle disclosed in Patent Literature 1, a converter, an inverter, and a filter reactor that require forced air cooling and another component not requiring forced air cooling are

placed together in the same housing. In the power conversion system for an AC-DC dual current electric railroad vehicle, the converter, the invertor and the filter reactor are placed in a cooling air passage provided inside the housing and the another component not requiring forced air cooling is placed outside the cooling air passage. As in an underfloor device for a railroad vehicle disclosed in Patent Literature 2, the inside space of a housing of a power conversion device placed under a floor of a railroad vehicle is partitioned into a plurality of spaces by partition elements.
Citation List
Patent Literature
[0004] Patent Literature 1: Unexamined Japanese Patent Application Kokai
Publication No. 2005-001598
Patent Literature 2: Unexamined Japanese Patent Application Kokai Publication No. 2009-96460
Summary of Invention
Technical Problem
[0005] In the power conversion system for an AC-DC dual current electric railroad
vehicle disclosed in Patent Literature 1, the components to be subjected to forced air
cooling are sufficiently cooled however a situation may occur where another component
placed outside the cooling air passage is not sufficiently cooled. In the case where the
inside space of the housing is partitioned into the plurality of spaces as in the underfloor
device for a railroad vehicle disclosed in Patent Literature 2, rises in temperature in
partitioned spaces near the center of the housing may be greater than rises in temperature
in the other partitioned spaces. If a rise in temperature in a portion of the inside space of
the housing is larger than a rise in temperature in another portion of the inside space of
the housing, performances of the electronic components placed in the portion in which
the larger rise in temperature occurs may be adversely affected.
[0006] The present disclosure is made in order to solve the aforementioned

problems, and thus an objective of the present disclosure is to reduce a difference in rise in temperature in respective portions in a housing.
Solution to Problem
[0007] In order to achieve the above obj ective, a power conversion device of the
present disclosure including a power converter for converting an input power to output the converted power, a reactor connected to an input side of the power converter, and a controller for controlling an electronic component included in the power converter includes an open part, a first airtight part, and a second airtight part. External air that is air from outside of the power conversion device flows into the open part, and the reactor is placed in the open part. External air does not flow into the first airtight part adj acent to the open part, and the electronic component is placed in the first airtight part. External air does not flow into the second airtight part adjacent to the first airtight part, and the controller is placed in the second airtight part. The power conversion device includes: at least two ventilation holes that are formed in a partition wall between the first airtight part and the second airtight part; a circulation fan with which at least one of the two ventilation holes is provided; and a heatsink that is placed in a housing forming the first airtight part and that releases, to outside of the power conversion device, at least some of heat transferred from the electronic component placed in the first airtight part.
Advantageous Effects of Invention
[0008] The power conversion device according to the present disclosure has a
structure in which at least two ventilation holes are formed in the partition wall between the first airtight part and the second airtight part and the circulation fan is provided in at least one of the two ventilation holes, and thus the power conversion device of the present disclosure enables a reduction in difference between a rise in temperature in the first airtight part and a rise in temperature in the second airtight part.
Brief Description of Drawings
[0009] FIG. 1 is a perspective view of a housing for a power conversion device

according to an embodiment of the present disclosure;
FIG. 2 is a drawing illustrating an example of a configuration of an electric railroad vehicle including the power conversion device according to the embodiment;
FIG. 3 is a cross-sectional view of the power conversion device according to the embodiment;
FIG. 4 is another cross-sectional view of the power conversion device according to the embodiment;
FIG. 5 is yet another cross-sectional view of the power conversion device according to the embodiment;
FIG. 6 is yet another cross-sectional view of the power conversion device according to the embodiment; and
FIG. 7 is yet another cross-sectional view of the power conversion device according to the embodiment.
Description of Embodiments
[0010] Embodiments of the present disclosure are described in detail hereinafter
with reference to drawings. Components that are the same or equivalent are assigned the same reference signs throughout the drawings.
[0011 ] FIG. 1 is a perspective view of a housing for a power conversion device
according to an embodiment of the present disclosure. The upper portion of a power conversion device 1 is omitted in FIG. 1. The inside space of a housing of the power conversion device 1 is partitioned by a partition wall, and the power conversion device 1 includes an open part 10 into which external air that is air outside of the power conversion device 1 flows, a first airtight part 20 into which no external air flows, the first airtight part 20 being adjacent to the open part 10, and a second airtight part 30 into which no external air flows, the second airtight part 30 being adjacent to the first airtight part 20. In the power conversion device 1 illustrated in FIG. 1, a direction along which the open part 10 and the first airtight part 20 align with each other matches a direction

along which the first airtight part 20 and the second airtight part 30 align with each other. The power conversion device 1 is mounted, for example, under a floor of an electric railroad vehicle.
[0012] The housing forming the open part 10 is provided with an inflow port 11
and a discharge port 12. In the example of FIG. 1, the inflow port 11 and the discharge
port 12 are formed in each of two sides of the housing facing each other in a direction
perpendicular to the direction along which the open part 10 and the first airtight part 20
align with each other. At least two ventilation holes 22 are formed in a partition wall 21
between the first airtight part 20 and the second airtight part 30. At least one of the
ventilation holes 22 is provided with a circulation fan that is described below in detail.
The housing forming the first airtight part 20, that is, an outer surface of the first airtight
part 20, is provided with a heatsink 23 to release to the external air at least some of heat
transferred from an electronic component placed in the first airtight part 20. In the
example of FIG. 1, the heatsink 23 is exposed to the open part 10. Although, in the
example illustrated in FIG. 1, a straight-fin heatsink is used as the heatsink 23, any type
of heatsink, such as a pin-fin heatsink, may be used as the heatsink 23. The heatsink 23
is formed on a substrate 24 and releases heat transferred from the electronic component
placed on the opposite surface of the substrate 24, that is, inside the first airtight part 20.
Although, in the example illustrated in FIG. 1, the heatsink 23 is exposed to the open part
10 through an opening area formed on the upper side of the housing above the first
airtight part 20, a location at which the heatsink 23 is placed is not limited to the location
of the heatsink 23 illustrated in FIG. 1. Although any aspect of the power conversion
device 1 may be freely defined, wind caused by movement of the vehicle can be taken
into the open part 10 by making a direction in which the inflow port 11 faces the
discharge port 12 match a traveling direction of the electric railroad vehicle in the case of
the power conversion device 1 illustrated in FIG. 1.
[0013] FIG. 2 is a drawing illustrating an example of a configuration of an electric

railroad vehicle including the power conversion device according to the embodiment.
The power conversion device 1 converts power acquired from an overhead line 101 via a
power collector 102 to supply power to a load device 103 such as an air conditioner or an
illuminating device, the load device 103 being connected to the output side of the power
conversion device 1. The power acquired from the overhead line 101 is inputted into a
power converter 40 via a switch 2 and an input reactor 3. The power converter 40
includes a primary circuit 50, a transformer 60, a secondary circuit 70, and a three-phase
inverter circuit 80. In an example illustrated in FIG. 2, switching elements 52, 53, 54
and 55 include in the primary circuit 50 as an inverter circuit and switching elements 82,
83, 84, 85, 86 and 87 that the three-phase inverter circuit 80 includes are insulated gate
bipolar transistors (IGBT) but any semiconductor element may be used.
[0014] The primary circuit 50 converts direct current power into high-frequency
single-phase alternating current power. In the example illustrated in FIG. 2, the primary circuit 50 has a full bridge circuit structure but may instead have a half bridge circuit structure or another structure. The transformer 60 is connected to the primary circuit 50 and the secondary circuit 70 and performs power conversion with the primary side insulated from the secondary side. The secondary circuit 70 rectifies a high-frequency alternating current (AC) voltage inputted from the transformer 60 into a direct current DC voltage and applies the DC voltage to a capacitor 81 included in the three-phase inverter circuit 80. A connection point between the switching elements 52 and 53 is connected to one end of a primary winding of the transformer 60 via a connection conductor, and a connection point between the switching elements 54 and 55 is connected to the other end of the primary winding of the transformer 60 via a connection conductor. One end of a secondary winding of the transformer 60 is connected to a connection point between diodes 71 and 72 via a connection conductor, and another end of the secondary winding of the transformer 60 is connected to a connection point between the diodes 73 and 74 via a connection conductor. In order to

prevent the connection conductors from generating heat, thin-plate shaped copper conductors or litz wires are used as the connection conductors.
[0015] The three-phase inverter circuit 80 performs power conversion to output a
three-phase AC voltage having a desired frequency and desired magnitude. A controller 4 controls: a switching operation of the switch 2; and switching operations of the switching elements 52, 53, 54, 55, 82, 83, 84, 85, 86, and 87. A circulation fan controller 8 controls a circulation fan 25 such that the circulation fan 25 runs during operation of the power conversion device 1. Power is supplied to the controller 4, the circulation fan controller 8, and the circulation fan 25 from an internal power source that the power conversion device 1 includes.
[0016] A reactor 5 that includes alternating-current reactors placed for the
respective phases, a capacitor 6 that includes alternating-current capacitors connected to lines of the respective phases, a cooling blower 7, and the load device 103 are connected to the output side of the power converter 40. The reactor 5 and the capacitor 6 constitute a smoothing filter circuit and the smoothing filter circuit smooths a waveform of a pulsed voltage outputted by the three-phase inverter circuit 80, thereby obtaining sine wave alternating current.
[0017] Placement of the respective components of the power conversion device 1 in
the housing of the power conversion device 1 illustrated in FIG. 1 is described below. FIGS. 3 and 4 are cross-sectional views of the power conversion device according to the embodiment. FIG. 3 is a cross-sectional view of the power conversion device 1 along A-A line illustrated in FIG. 1 and FIG. 4 is a cross-sectional view of the power conversion device 1 along B-B line illustrated in FIG. 3. High-frequency large AC currents flow through the primary circuit 50, the transformer 60, the secondary circuit 70, and the three phase inverter circuit 80 that are included in the power converter 40. Therefore, the primary circuit 50, the transformer 60, the secondary circuit 70, and the three-phase inverter circuit 80 release more heat than the other components. Therefore,

the primary circuit 50, the transformer 60, the secondary circuit 70, and the three-phase inverter circuit 80 are placed in the first airtight part 20 in which heat generated in the housing is released from the housing and the heatsink 23.
[0018] Since the switch 2, the controller 4, the capacitator 6, and the circulation fan
controller 8 release less heat than the above components included in the power converter 40 and may fail to operate properly due to dust and moisture, the switch 2, the controller 4, the capacitator section 6, and the circulation fan controller 8 are placed in the second airtight part 30. The input reactors 3 and the alternating-current reactors included in the reactor 5 are made by winding conductive material such as copper or aluminum into a coil shape. Since the resistance of the conductors of the input reactor 3 and the reactor 5 causes a large loss during operation of the power conversion device 1, the input reactor 3 and the reactor 5 have to be forcefully cooled with air. Therefore, the input reactor 3 and the reactor 5 are placed in the open part 10. The cooling blower 7 is placed in the open part 10 such that the cooling blower 7 blows air from the inflow port 11 to the discharge port 12.
[0019] The connection conductor connecting the switch 2 to the input reactor 3 and
the connection conductor connecting the reactor 5 to the capacitor 6 are inserted into
holes (not illustrated in the drawings) formed in the partition wall between the open part
10 and the first airtight part 20 and in the partition wall 21 between the first airtight part
20 and the second airtight part 30. The connection conductor connecting the input
reactor 3 to the power converter 40 and the connection conductor connecting the reactor 5
to the power converter 40 are inserted into holes (omitted in the drawings) formed in the
partition wall between the open part 10 and the first airtight part 20.
[0020] The heat generation amount of the components placed in the first airtight
part 20 is different from the heat generation amount of the components placed in the second airtight part 30. As the first airtight part 20 differs from the second airtight part 30 in volume and in surface area, an amount of heat released from the first airtight part 20

is different from an amount of heat released from the second airtight part 30. As a result,
such a difference between the first air tight part 20 and the second airtight part 30 causes
a difference between the first airtight part 20 and the second airtight part 30 in amount of
rise in temperature. At least one of at least two ventilation holes 22 formed in the
partition wall 21 between the first airtight part 20 and the second airtight part 30 is
provided with the circulation fan 25. The circulation fan controller 8 operates the
circulation fan 25 in accordance with a required quantity of airflow blown by the
circulation fan 25 that is previously calculated based on estimate values of amounts of
change in temperature in the first airtight part 20 and the second airtight part 30. When
the circulation fan 25 runs, air in the first airtight part 20 moves to the second airtight part
30, the same amount of air moves from the second airtight part 30 to the first airtight part
20, thereby circulating air between the first airtight part 20 and the second airtight part 30.
The air circulation in the first airtight part 20 and the second airtight part 30 that is
generated by the circulation fan 25 enables reduction of a difference between the first
airtight part 20 and the second airtight part 30 in amount of rise in temperature.
[0021] In the case where a switching frequency of the primary circuit 50 is about 20
kHz and the electronic components of the power conversion device 1 mounted on an electric railroad vehicle are placed in the first airtight part 20 and the second airtight part 30 as illustrated in FIGS. 3 and 4, an amount of heat released to the first airtight part 20 is about 500 W, whereas an amount of heat generation in the second airtight part 30 is about 100 W. That is to say, a rise in temperature in the first airtight part 20 is greater than a rise in temperature in the second airtight part 30. Air circulation between the first airtight part 20 and the second airtight part 30 generated by operation of the circulation fan 25 enables suppression or prevention of a rise in temperature in the first airtight part 20. A required quantity of airflow blown by the circulation fan 25 is calculated based on estimate values of heat resistance temperatures of and amounts of change in temperature of the electronic components placed in the first airtight part 20 and the

second airtight part 30. The estimate values of amounts of change in temperature can be calculated from estimate values of the amounts of heat generation and the estimate values of the amounts of heat released.
[0022] Since the second airtight part 30 is not provided with a heatsink, heat
generated in the housing is released from the housing. Insufficient release of heat from
the housing may cause a temperature rise in the second airtight part 30 that is greater than
a temperature rise in the first airtight part 20. Even in that case, air circulation between
the first airtight part 20 and the second airtight part 30 generated by operation of the
circulation fan 25 enables suppression or prevention of a temperature rise in the second
airtight part 30. Operation of the circulation fan 25 enables reduction in a difference
between temperature rises in the first airtight part 20 and the second airtight part 30.
[0023] In the case where the switching frequency of the primary circuit 50 is about
20 kHz, currents of about several hundred amperes having a frequency of about 20 kHz flow through the connection conductor between the primary circuit 50 and the transformer 60 and through the connection conductor between the secondary circuit 70 and the transformer 60, thereby causing the connection conductors to generate large amounts of heat. As illustrated in FIGS. 3 and 4, the primary circuit 50, the transformer 60 and the secondary circuit 70 are placed in the first airtight part 20 and connection conductors short in length are used as the connection conductor between the primary circuit 50 and the transformer 60 and as the connection conductor between the secondary circuit 70 and the transformer 60 thereby enabling reduction in amounts of heat generated by the connection conductors because of the skin effect.
[0024] Although the circulation fan 25 is operated based on a previously calculated
required amount of airflow in the above example, the circulation fan 25 may be operated based on a temperature difference between the first airtight part 20 and the second airtight part 30. The circulation fan controller 8 acquires measurement values of temperature from temperature sensors with which the first airtight part 20 and the second airtight part

30 are provided, calculates a required amount of airflow blown by the circulation fan 25
in accordance with a temperature difference between the first airtight part 20 and the
second airtight part 30, and regulates an amount of airflow blown by the circulation fan
25 in accordance with the calculated required amount of air flow. The circulation fan
controller 8 may detect the magnitude of currents flowing through the connection
conductors in the first airtight part 20 and the magnitude of currents flowing through the
connection conductors in the second airtight part 30, calculate a required amount of
airflow blown by the circulation fan 25 in accordance with a difference between the
detection values, and regulate an amount of airflow blown by the circulation fan 25 in
accordance with the calculated required amount of airflow.
[0025] As described above, the power conversion device 1 according to the
embodiment has the structure in which: at least two ventilation holes 22 are formed in the
partition wall 21 between the first airtight part 20 and the second airtight part 30; and at
least one of the two ventilation holes 22 is provided with the circulation fan 25. Thus,
the power conversion device 1 enables reduction in a difference between temperature
rises in the first airtight part 20 and in the second airtight part 30. The reduction in the
differences between temperature rises of the components in the housing results in
suppression or prevention of generation of an excessively high temperature in the more
heat-susceptible electronic components, improvement in a reliability of the power
conversion device 1, and prolongation of the life of the power conversion device 1.
[0026] Embodiments of the present disclosure are not limited to the above
embodiment. A structure for the power converter 40 is not limited to the structure illustrated in FIG. 2, and the power converter 40 may be a power conversion circuit that includes a capacitor and a switching element without having a transformer, a direct-current-to-direct-current converter (DC-DC converter), or a chopper circuit. There is no need for the power conversion device 1 to include the cooling blower 7 and each component of the power conversion device 1 may be cooled by a wind caused by

movement of the electric railroad vehicle. The power conversion device 1 may be
placed on a roof of the electric railroad vehicle instead of placing the power conversion
device 1 under a floor of the electric railroad vehicle. The number of airtight parts
formed in the present disclosure is not limited to two, and the power conversion device 1
may include three or more airtight parts. In that case, at least two ventilation holes are
formed in a partition wall between each pair of airtight parts adjacent to each other.
[0027] A structure for the power conversion device 1 is not limited to the above
structure. FIGS. 5, 6 and 7 are cross-sectional views of the power conversion device according to the embodiment. In the power conversion device 1 illustrated in FIG. 5, the heatsink 23 is exposed to the outside of the power conversion device 1. In the power conversion device 1 illustrated in FIG. 6, a direction along which the open part 10 aligns with the first airtight part 20 is perpendicular to a direction along which the first airtight part 20 aligns with the second airtight part 30. In the power conversion device 1 illustrated in FIG. 7, the inflow ports 11 and the discharge ports 12 are formed in two side portions among portions of the housing forming the open part 10, the two lateral side portions being adjacent to each other.
[0028] 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
[0029] 1 Power conversion device
2 Switch

3 Input reactor
4 Controller
5 Reactor
6 Capacitor
7 Cooling blower
8 Circulation fan controller

10 Open part
11 Inflow port
12 Discharge port
22 Ventilation hole
20 First airtight part
21 Partition wall

23 Heatsink
24 Substrate
25 Circulation fan
30 Second airtight part
40 Power converter
50 Primary circuit
51,81 Capacitator
52, 53, 54, 55, 82, 83, 84, 85, 86, 87 Switching element
60 Transformer
70 Secondary circuit
71, 72, 73, 74 Diode
80 Three-phase inverter circuit
101 Overhead line
102 Power collector
103 Load device

We Claim:
1. A power conversion device that includes a power converter for converting
an input power to output the converted power, a reactor connected to an input side of the
power converter, and a controller for controlling an electronic component included in the
power converter, the power conversion device comprising:
an open part containing the reactor and allowing inflow of external air into the open part, the external air being air from outside of the power conversion device;
a first airtight part adjacent to the open part, the first airtight part containing the electronic component and being sealed to be free from inflow of the external air into the first airtight part; and
a second airtight part adjacent to the first airtight part, the second airtight part containing the controller and being sealed to be free from inflow of the external air into the second airtight part, wherein
at least two ventilation holes are formed in a partition wall between the first airtight part and the second airtight part,
the power conversion device comprises:
a circulation fan that is provided in at least one of the ventilation holes; and a heatsink that is placed in a housing forming the first airtight part and that releases to outside of the power conversion device, at least some of heat transferred from the electronic component placed in the first airtight part.
2. The power conversion device according to claim 1, further comprising:
a circulation fan controller to cause the circulation fan to operate in accordance
with a required amount of airflow blown by the circulation fan, the required amount of airflow being previously calculated based on estimate values of amounts of change in temperature in the first airtight part and the second airtight part.

3. The power conversion device according to claim 1, further comprising:
a circulation fan controller to regulate an amount of airflow blown by the
circulation fan in accordance with a temperature difference between the first airtight part and the second airtight part.
4. The power conversion device according to claim 1, wherein
the housing forming the open part is provided with an inflow port and an discharge port and
the power conversion device further comprises a cooling blower that is placed in the open part and that blows air such that the air flows from the inflow port to the discharge port.