1. A power conversion device comprising: a condenser; a plurality of semiconductor modules! a heat dissipation unit for cooling the plurality of the semiconductor modules collectively,' a bus bar connecting the condenser with the plurality of semiconductor modules; and a ventilation unit having cool wind blow,' wherein the plurality of semiconductor modules are arranged apart from the condenser and in a line in a longitudinal direction of the bus bar, and the cool wind blows in a direction from the condenser toward the plurality of semiconductor modules that are mounted.

2. The power conversion device as described in claim 1, wherein the heat dissipation unit comprises'• a heat receiving block disposed in contact with the plurality of semiconductor modules,' heat pipes fixed to the heat receiving block; and a fin joined to the heat pipes.

3. The power conversion device as described in claim 2, wherein the semiconductor modules include a first semiconductor module and a second semiconductor module, the first semiconductor module being closer to the condenser than the second semiconductor module is, the heat pipes include a first heat pipe to cool the first semiconductor module and a second heat pipe to cool the second semiconductor module, and a width of a first portion of the fin to which the first heat pipe is joined is larger than a width of a second portion of the fin to which the second heat pipe is joined.

4. The power conversion device as described in claim 2, wherein the semiconductor modules include a first semiconductor module and a second 14 semiconductor module, the first semiconductor module being closer to the condenser than the second semiconductor module is, the heat pipes include a first heat pipe to cool the first semiconductor module and a second heat pipe to cool the second semiconductor module, and a diameter of the first heat pipe is larger than a diameter of the second heat pipe.

5. The power conversion device as described in claim 2, wherein the semiconductor modules include a first semiconductor module and a second semiconductor module, the first semiconductor module being closer to the condenser than the second semiconductor module is, the heat pipes include a first heat pipe to cool the first semiconductor module and a second heat pipe to cool the second semiconductor module, and the first heat pipe has a smaller heat conduction resistance than the second heat pipe and is capable of transferring a larger amount of heat than the second heat pipe.

BACKGROUND OF THE INVENTION
1. Field of Invention
[0001] The present invention relates to a power conversion device.
2. Description of the related art
[0002] A power conversion device is a device to convert electrical power and
configured to convert any of AC and DC electrical power to the other or alter a
frequency of electrical power by controlling switching operation of semiconductor
elements included in the power conversion device such as Insulated Gate Bipolar
Transistor (IGBT). There is a loss generated by switching on and off these
semiconductor elements and having an electrical current flowing through these
semiconductor elements. If a temperature of the semiconductor element becomes
higher than a threshold operation temperature of the semiconductor device due to
heat from the loss, the semiconductor device is not capable of stopping the current
from flowing by its switching operation and the power conversion device could break
in the worst case. Therefore it is necessary to appropriately cool the power
conversion device while it is in operation.
[0003] There are plural semiconductor elements provided in a semiconductor
module installed in the power conversion device. The power conversion device
usually includes plural semiconductor modules which are connected in parallel with
each other. It is desirable to keep temperatures of the semiconductor modules equal
to each other when the temperatures of the semiconductor modules rise while the
power conversion device is in operation. If there is a variation in the raised
temperature between the semiconductor modules, a semiconductor module that is
heated to a higher temperature than the others cannot be used longer than the
others, which results in the power conversion device being less reliable.
[0004] As for cooling semiconductor modules included in the power conversion
device, JP2011-120358A discloses "a power conversion device" comprising plural
semiconductor modules each of which includes a switching device, a cooling device
for cooling the plural semiconductor devices, and a condenser connected with the
plural semiconductor devices, wherein one of the plural semiconductor modules that
3
dissipates less heat than the others has the switching device either having a lowest
gate resistance or base resistance, or having a lowest inductance on a current
passage between the switching device and the condenser and a highest gate voltage
or base voltage (See claim 1 of JP201M20358A).
SUMMARY OF THE INVENTION
[0005] The power conversion device (power conversion device) as described in
JP2011-120358A is intended to reduce the temperature variation among the
semiconductor modules by using a switching device with the lowest gate resistance
for one of the semiconductor modules that dissipates least heat and designing the
current passage between the one of the semiconductor modules and the condenser
to have the lowest inductance.
[0006] However, if such plural semiconductor modules as have various
switching devices which differ in the gate resistance from one another are used, as
is the case with the power conversion device (power conversion device) described for
in JP2011-120358A, the number of components increases. As a result, productivity
lowers and it is more difficult to maintenance such power conversion devices. In
addition, if the loop inductance between the condenser and one of the semiconductor
modules that dissipate least heat is made lowest, a loss while an electrical current
is flowing becomes higher although a loss due to the voltage jumping up on
switching decreases. Therefore, the total loss could be larger for some frequencies.
[0007] The objective of the present invention is to provide a power conversion
device in which the temperature variation among the plural semiconductor modules
is reduced.
[0008] In order to achieve the objective, the power conversion device of the
present invention comprises a condenser, a plurality of semiconductor modules, a
heat dissipation unit for cooling the plurality of the semiconductor modules
collectively, a bus bar connecting the condenser with the plurality of semiconductor
modules and a ventilation unit having cool wind blow, wherein the plurality of
semiconductor modules are arranged apart from the condenser and in a line in a
longitudinal direction of the bus bar, and the cool wind blows in a direction from the
condenser toward the plurality of semiconductor module that are mounted.
4
[0009] The power conversion device according to the present invention is
capable of reducing the temperature variation among the plural semiconductor
module.
BRIEF DESCRIPTION OF THE DRAWING
[0010] Fig.l is a circuit diagram showing an example of a power conversion
device according to the first embodiment.
Fig.2 is a perspective view of a power conversion unit according to the
first embodiment.
Fig.3 is an exploded perspective view of a bus bar used for the power
conversion unit.
Fig.4 is a perspective view of a power conversion unit according to the
second embodiment.
Fig.5 is a perspective view of a power conversion unit according to the
third embodiment.
DETALED DESCRIPTION OF THE THE INVENTION
[0011] Hereinafter, embodiments to practice the present invention are
explained in detail with reference to appropriate figures that are attached.
Identical signs used among plural figures indicate a component commonly used and
a duplicate explanation for the component is omitted.
[0012]
A power conversion device S according to the first embodiment is
explained with reference to Fig.l. Fig.l is a circuit diagram showing an example of
a power conversion device according to the first embodiment. An inverter having a
function of converting a DC current to a three-phase current, which corresponds to
an example of the power conversion device S, is to be explained.
[0013] The power conversion device S for a conversion device is equipped with a
TJ-phase power conversion unit 100U, a V-phase conversion unit 100V, a W-phase
control unit 100W, a control unit (not shown) to control switching operation of a
semiconductor element (IGBT) of each of the power conversion units 100U, 100V,
100W and a ventilating unit (not shown) to cool each of the power conversion units
5
100U, lOOV, lOOW. Since the U-phase power conversion unit 100U, the V-phase
conversion unit 100V and the W-phase control unit lOOW have similar structures to
one another, a power conversion unit 100 used in the description below indicates
any of the U-phase power conversion unit 100U, the V-phase conversion unit 100V
and the W-phase control unit 100W unless distinction is made among them.
[0014] The power conversion unit 100 comprises semiconductor modules 101,
102 and condensers 121, 122, all of which are connected in parallel with one another.
Each of these semiconductor modules 101, 102 and condensers 121, 122 has one end
connected with a P-wire for the DC current and the other end connected with an Nwire
for the DC current. Current capacity is increased with the semiconductor
modules connected in parallel.
[0015] Each of the semiconductor modules has a circuit configuration in which a
couple of hybrid IGBTs (semiconductor device) each having, for example, a fast
recovery diode (FRD) are connected in series. Accordingly, the semiconductor
module 101 has an upper side IGBT with a collector terminal connected with the Pwire
(at Pi) and a lower side IGBT with an emitter terminal connected with the Nwire
(at Nl). Both an emitter terminal of the upper side IGBT and a collector
terminal of the lower side IGBT are connected with an AC-wire (ACl). Similarly,
the semiconductor module 102 has an upper side IGBT with a collector terminal
connected with the P-wire (at P2) and a lower side IGBT with an emitter terminal
connected with the N-wire (at N2). Both an emitter terminal of the upper side
IGBT and a collector terminal of the lower side IGBT are connected with an ACwire
(at AC2). Both the AC-wire (through ACl) of the semiconductor module 101
and the AC-wire (through AC2) of the semiconductor module 102 are connected
with the AC-wire (AC) of the power conversion unit 100.
[0016] The control unit (not shown) is configured to control the switching
operation of the semiconductor elements (IGBT) of the semiconductor modules 101,
102 included in each of the power conversion units 100 (100U, 100V, 100W).
Accordingly the control means controls a gate voltage of IGBT. With this control,
the power conversion device S is able to function as a conversion device to convert
the DC current to the three-phase current.
[0017]
6
A structure of the power conversion unit 100 of the power conversion
device S according to the first embodiment is further explained with reference to
Fig.2 and Fig.3. Fig.2 is a perspective view of a power conversion unit 100
according to the first embodiment. Fig.3 is an exploded perspective view of a bus
bar 140 used for the power conversion unit 100.
[0018] As shown in Fig.2, the power conversion unit 100 comprises
semiconductor modules 101, 102, heat receiving blocks 103, 104, heat pipes 105 to
108, a fin 109, condensers 121, 122 and a bus bar 140. An arrow sign represented
by a sign 150 indicates a direction in which cooling wind supplied by the cooling
ventilation means (not shown) blows.
[0019] There are a couple of semiconductor modules 101,102 assembled into the
power conversion device 100. Each of these semiconductor modules 101, 102 is of a
two face cooling type and has heat dissipation faces on both sides. Heat receiving
block s 103, 104 are disposed in contact with the heat dissipation faces of the couple
of semiconductor modules and heat generated in the semiconductor modules 101,
102 is transferred to the heat dissipation blocks 103, 104.
[0020] The heat receiving block 103 is disposed in contact with one of the heat
dissipation faces of the semiconductor module 101 and one of the heat dissipation
faces of the semiconductor module 102. There are four heat pipes 105 to 108
embedded in the heat dissipation block 103. There is a fin 109 that is fixed onto the
heat pipes 105 to 108 and configured to dissipate heat to ambient air. Similarly the
heat receiving block 104 is disposed in contact with the other of the heat dissipation
faces of the semiconductor module 101 and the other of the heat dissipation faces of
the semiconductor module 102. There are four heat pipes that are fixed onto the
semiconductor module 102 and configured to dissipate heat into ambient air.
[0021] The semiconductor module 101 has a terminal 111 connected with the
bus bar 140. Similarly the semiconductor module 102 has a terminal 112 connected
with the bus bar 140. In addition, the condenser 121 has a terminal 131 connected
with the bus bar 140. Similarly the condenser 122 has terminal 132 connected with
the bus bar 140.
[0022] As shown in Fig.3, the bus bar 140 includes a P-wire bus bar 140P, an Nwire
bus bar 140N and an AC-wire bus bar 140AC. Adjacent bus bars are insulated
with an insulation material or the like.
7
[0023] The P-wire bus bar 140P has a connection portion 14IP with which one
of the terminals of the condenser 121, a connection portion 142P with which one of
the terminals of the condenser 122, a connection portion PI with which the first
terminal (collector terminal of the upper IGBT in Fig.l) of the semiconductor
module 101 and a connection portion P2 with which the first terminal (collector
terminal of upper IGBT in Fig.l) of the semiconductor module 102 is connected.
[0024] The N-wire bus bar 140N has a connection portion 141N with which the
other of the terminals of the condenser 121 is connected, a connection portion 142N
with which one of the terminals of the condenser 122 is connected, a connection
portion Nl with which the second terminal (emitter terminal of lower IGBT in
Fig.l) of the semiconductor module 101 is connected, and a connection portion N2
with which the second terminal (emitter terminal of the lower IGBT in Fig.l) of the
semiconductor module 102 is connected.
[0025] The AC-wire bus bar 140AC has a connection portion ACl with which
the third terminal (emitter terminal of upper IGBT and collector terminal of lower
IGBT in Fig.l) of the semiconductor module 101 is connected and a connection
portion AC2 with which the third terminal (emitter terminal of upper IGBT and
collector terminal of lower IGBT in Fig.l) of the semiconductor module 102 is
connected.
[0026] As shown in Fig.2 and Fig. 3, the semiconductor modules 101, 102 and
the condensers 121, 122 are arranged in a line. Accordingly, as is seen in Fig.3,
distances from the connection portion PI of the semiconductor module 101 to the
connection portions 141P, 142P of the condensers 121, 122 are shorter than
distances from the connection portion P2 of the semiconductor module 102 to the
connection portions 141P, 142P of the condensers 121, 122. Similarly, distances
from the connection portion Nl of the semiconductor module 101 to the connection
portions 141N, 142N of the condensers 121, 122 are shorter than distances from the
connection portion N2 of the semiconductor module 102 to the connection portions
141N, 142Nofthe condensers 121, 122.
[0027] As is described, the semiconductor module 101 is closer to the condensers
121, 122 than the semiconductor module 102 and an inductance and a resistance
through the bus bar 140 are smaller for the semiconductor module 101.
Accordingly, a larger electrical current flows through the semiconductor module 101
8
than through the semiconductor module 102 while the power conversion device S
(power conversion unit 100) is in operation. As a result, a generated loss
(corresponding to a generated heat) of the semiconductor module 101 is larger than
a generated loss (corresponding to a generated heat) of the semiconductor module
102. Therefore, there is a variation in the generated heat between the
semiconductor modules 101, 102.
[0028] In order to reduce the temperature variation between the semiconductor
modules 101, 102 that results from the variation in the generated heat between the
semiconductor modules 101, 102, the power conversion device S (power conversion
unit 100) utilizes common heat receiving blocks 103, 104 disposed onto the couple of
the semiconductor modules 101, 102.
[0029] As the above mentioned structure is used, heat generated from the
semiconductor module 101 is transmitted to the semiconductor module 102 through
the heat receiving blocks 103, 104. As a result, the heat generated from the
semiconductor module 101 can be transmitted to the fin 109 not only through the
heat pipes 105, 106 disposed on the side of the semiconductor module 101, but also
through the heat pipes 107, 108 disposed on the side of the semiconductor module
102.
[0030] In addition, as is seen in the power conversion device S (power
conversion unit 100) illustrated in Fig.2, cooling wind blows in a direction 150 that
corresponds to a direction from a lower side toward an upper side in Fig.2.
Accordingly, the cooling wind blows from the condensers 121, 122 toward the
semiconductor modules 101, 102. In the other words, the cooling wind blows from
the semiconductor module 101 that is disposed nearer to the condensers 121, 122
toward the semiconductor module 102 that is disposed farther from the condensers
121, 122.
[0031] According to this structure, the semiconductor module 101 is more
efficiently cooled because the heat pipes 105, 106 to cool the semiconductor module
101 are arranged on the upwind side of the heat pipe 107, 108 to cool the
semiconductor module 102.
[0032] As has been mentioned, the power conversion device S (power conversion
unit 100) has the semiconductor modules 101, 102 and the condensers 121, 122
arranged in a line and there is a variation in the generated loss (generated heat)
9
between the semiconductor modules 101, 102. However, since the semiconductor
module 101 can be cooled more efficiently than the semiconductor module 102, the
temperature variation between the semiconductor modules 101, 102 is reduced.
Accordingly, the power conversion device S (power conversion unit 100) is more
reliable.
[0033] Moreover, identical semiconductor modules to each other can be used for
the semiconductor modules 101, 102 in the power conversion device S (power
conversion unit 100) according to the first embodiment. As a result, it is not
necessary to use semiconductor modules whose gate resistance differs from each
other, as is the case with JP2011-120358A, and it is possible to prevent the number
of components used for a power conversion device S from increasing and improve
easiness for production and maintenance.
[0034] Furthermore the cooling wind blows in the direction 150 from the side of
the condensers 121, 122 toward the side of the semiconductor modules 101, 102,
which enables the cooling wind heated by generated heat by the semiconductor
modules 101, 102 to be prevented from heating the condensers 121, 122.
[0035] In addition, since the semiconductor modules 101, 102 and the
condensers 121, 122 are arranged in a line in the power conversion unit 100 of the
power conversion device S according to the first embodiment, as shown in Fig.2, it is
possible to make the power conversion device S thinner, which contributes to
making the size of the power conversion device S smaller.
[0036]
Next, the power conversion device S of the second embodiment is
explained. The power conversion device S of the second embodiment is different
from the power conversion device S of the first embodiment in the configuration of
the power conversion unit 100. More specifically, the power conversion device S of
the second embodiment has a power conversion unit 100A (as illustrated in Fig.4
below) with which the power conversion unit 100 (as shown in Fig. 1 and Fig.2) is
replaced in the power conversion device S of the first embodiment. The other
elements are common between the power conversion devices S of the first
embodiment and the second embodiment and not explained.
[0037]
10
A configuration of a power conversion unit 100A used for the power
conversion device (inverter) S of the second embodiment is explained with reference
to Fig.4. Fig.4 is a perspective view of a power conversion unit 100A according to
the second embodiment.
[0038] As is shown in Fig.4, the power conversion unit 100A includes
semiconductor modules 101, 102, heat receiving blocks 103, 104, heat pipes 105 to
108, a fin 209, condensers 121, 122 and a bus bar 140. It is understood that the
power conversion unit 100A of the second embodiment has the fin 209 whose shape
is different from that of the fin 109 (as shown in Fig.2) of the power conversion unit
100 of the first embodiment.
[0039] The fin 209 is joined to both the heat pipes 105, 106 which are configured
to cool the semiconductor module 101 that generates more heat loss (generated
heat) than the semiconductor module 102 and the heat pipes 107, 108 which are
configured to cool the semiconductor module 102 that generates less heat loss. The
fin 209 is configured to have a portion that is relatively closer to the heat pipes 105,
106 and has a larger width and the other portion that is relatively closer to heat
pipes 107, 108 and has a smaller width.
[0040] Since the semiconductor module 101 can be cooled more efficiently than
the semiconductor module 102 with the fin 209 used, this fin 209 has an effect of
reducing the temperature difference between the semiconductor module 101, 102,
which contributes to improving the reliability of the power conversion unit S with
the power conversion unit 100A.
[0041]
11
A configuration of a power conversion unit 100B used for the power
conversion device (inverter) S of the third embodiment is explained with reference
to Fig.5. Fig.5 is a perspective view of a power conversion unit 100B according to
the third embodiment.
[0043] As is shown in Fig.5, the power conversion unit 100B includes
semiconductor modules 101, 102, heat receiving blocks 103, 104, heat pipes 305, 306,
heat pipes 107, 108, a fin 109, condensers 121, 122 and a bus bar 140. It is
understood that the power conversion unit 100B has the heat pipes 305, 306 that
are different from the heat pipes 105, 106 (as shown in Fig.2) of the power
conversion unit 100 of the first embodiment.
[0044] The heat pipes 305, 306 are configured to cool the semiconductor module
101 that generates more heat loss (generated heat) have a larger diameter than
that of the heat pipes 107, 108 that generates less heat loss (generated heat).
[0045] Since the semiconductor module 101 can be cooled more efficiently than
the semiconductor module 102 with the heat pipes 305, 306 used, these heat pipes
305, 306 have an effect of reducing the temperature difference between the
semiconductor module 101, 102, which contributes to improving the reliability of
the power conversion unit S with the power conversion unit 100B.
[0046]
The power conversion devices S according to the present embodiments
(first to third embodiments) is not be limited to configurations as have been
explained above and there should be various modifications of the embodiments
above explained which are within the scope of the present invention.
[0047] Although the power conversion device S of the present embodiment is
assumed to be a converter in the embodiments above described, the power
conversion device S of the present embodiment should not be limited to the inverter
and can be applied to any type of the power conversion device that controls
switching operation of semiconductor elements and alters a frequency of power or
converts any of AC and DC power to the other.
[0048] Although there are a couple of condensers included in the power
conversion unit 100 (100A, 100B) of the power conversion device S of the present
embodiments as has been described, the number of the condensers to be included in
the power conversion unit 100 is not limited to 2 and may be one or more than or
12
equal to 3. In addition, the power conversion unit 100 (100A, 100B) of the power
conversion device S includes a couple of semiconductor modules as has been
described. However the number of the semiconductor modules should not be
limited to 2 and may be more than or equal to 3.
[0049] Furthermore, each of the semiconductor modules 101, 102 is described as
being a semiconductor module of a two face cooling type that has a heat dissipation
face on each of its two faces, is not be limited to this type and may be of a one face
cooling type. Moreover, each of the semiconductor modules 101, 102 is described as
having a couple of hybrid IGBTs each having FRD which are connected in series as
shown in Fig.l. However, the semiconductor modules 101, 102 are not limited to
what is described above and may be any type of a semiconductor module having
semiconductor devices of which switching operation is controlled.
[0050] The heat pipes 305, 306 of the power conversion unit 100B of the power
conversion device S according to the third embodiment are described as having a
larger diameter than that of the heat pipes 107, 108 and not limited to this type.
For example, the heat pipes 305, 306 may be made of a different material from a
material of which the heat pipes 107, 108 are made of, the different material
making a heat resistance smaller to increase an amount of transferred heat from
the heat pipes 305, 306. The refrigerant used for the heat pipes 305, 307 may be a
different one from that used for the heat pipes 107, 108 in order to transfer a larger
amount of heat through the heat pipes 305, 307. These configurations have the
same effect as the power conversion device S according to the third embodiment.

We claim:
1. A power conversion device comprising:
a condenser;
a plurality of semiconductor modules!
a heat dissipation unit for cooling the plurality of the semiconductor
modules collectively,'
a bus bar connecting the condenser with the plurality of semiconductor
modules; and
a ventilation unit having cool wind blow,'
wherein the plurality of semiconductor modules are arranged apart from
the condenser and in a line in a longitudinal direction of the bus bar, and the cool
wind blows in a direction from the condenser toward the plurality of semiconductor
modules that are mounted.
2. The power conversion device as described in claim 1, wherein the heat
dissipation unit comprises'•
a heat receiving block disposed in contact with the plurality of
semiconductor modules,'
heat pipes fixed to the heat receiving block; and
a fin joined to the heat pipes.
3. The power conversion device as described in claim 2, wherein the
semiconductor modules include a first semiconductor module and a second
semiconductor module, the first semiconductor module being closer to the condenser
than the second semiconductor module is, the heat pipes include a first heat pipe to
cool the first semiconductor module and a second heat pipe to cool the second
semiconductor module, and a width of a first portion of the fin to which the first
heat pipe is joined is larger than a width of a second portion of the fin to which the
second heat pipe is joined.
4. The power conversion device as described in claim 2, wherein the
semiconductor modules include a first semiconductor module and a second
14
semiconductor module, the first semiconductor module being closer to the condenser
than the second semiconductor module is, the heat pipes include a first heat pipe to
cool the first semiconductor module and a second heat pipe to cool the second
semiconductor module, and a diameter of the first heat pipe is larger than a
diameter of the second heat pipe.
5. The power conversion device as described in claim 2, wherein the
semiconductor modules include a first semiconductor module and a second
semiconductor module, the first semiconductor module being closer to the condenser
than the second semiconductor module is, the heat pipes include a first heat pipe to
cool the first semiconductor module and a second heat pipe to cool the second
semiconductor module, and the first heat pipe has a smaller heat conduction
resistance than the second heat pipe and is capable of transferring a larger amount
of heat than the second heat pipe.