Abstract:
A power conversion device capable of reducing a temperature variation between a plurality of semiconductor modules is provided. The power conversion device comprises condensers  121, 122 , a plurality of semiconductor modules  101, 102 , heat dissipation units  103  to  109 , a bus bar  140  connecting the condensers  121, 122  with the plurality of the semiconductor modules  101, 102 , and a ventilation unit having cool wind blow. The power conversion module has features that the plurality of semiconductor modules  101, 102  are arranged apart from the condensers  121, 122  and in a line in a longitudinal direction of the bus bar  140  and that the cool wind  150  blows in a direction from the condensers  121, 122  toward the plurality of semiconductor modules  101, 102  that are mounted.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2014-137411 filed on Jul. 3, 2014, the entire specification, claims and drawings of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a power conversion device. 
     2. Description of the Related Art 
     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. 
     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. 
     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 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 JP2011-120358A). 
     SUMMARY OF THE INVENTION 
     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. 
     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. 
     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. 
     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. 
     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 
         FIG. 1  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. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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. 
     First Embodiment 
     Power Conversion Device 
     A power conversion device S according to the first embodiment is explained with reference to  FIG. 1 .  FIG. 1  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. 
     The power conversion device S for a conversion device is equipped with a U-phase power conversion unit  100 U, a V-phase conversion unit  100 V, a W-phase control unit  100 W, a control unit (not shown) to control switching operation of a semiconductor element (IGBT) of each of the power conversion units  100 U,  100 V,  100 W and a ventilating unit (not shown) to cool each of the power conversion units  100 U,  100 V,  100 W. Since the U-phase power conversion unit  100 U, the V-phase conversion unit  100 V and the W-phase control unit  100 W 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  100 U, the V-phase conversion unit  100 V and the W-phase control unit  100 W unless distinction is made among them. 
     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 N-wire for the DC current. Current capacity is increased with the semiconductor modules connected in parallel. 
     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 P-wire (at P 1 ) and a lower side IGBT with an emitter terminal connected with the N-wire (at N 1 ). Both an emitter terminal of the upper side IGBT and a collector terminal of the lower side IGBT are connected with an AC-wire (AC 1 ). Similarly, the semiconductor module  102  has an upper side IGBT with a collector terminal connected with the P-wire (at P 2 ) and a lower side IGBT with an emitter terminal connected with the N-wire (at N 2 ). Both an emitter terminal of the upper side IGBT and a collector terminal of the lower side IGBT are connected with an AC-wire (at AC 2 ). Both the AC-wire (through AC 1 ) of the semiconductor module  101  and the AC-wire (through AC 2 ) of the semiconductor module  102  are connected with the AC-wire (AC) of the power conversion unit  100 . 
     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  ( 100 U,  100 V,  100 W). 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. 
     &lt;Power Conversion Unit  100 &gt; 
     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 . 
     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. 
     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 . 
     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. 
     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 . 
     As shown in  FIG. 3 , the bus bar  140  includes a P-wire bus bar  140 P, an N-wire bus bar  140 N and an AC-wire bus bar  140 AC. Adjacent bus bars are insulated with an insulation material or the like. 
     The P-wire bus bar  140 P has a connection portion  141 P with which one of the terminals of the condenser  121 , a connection portion  142 P with which one of the terminals of the condenser  122 , a connection portion P 1  with which the first terminal (collector terminal of the upper IGBT in  FIG. 1 ) of the semiconductor module  101  and a connection portion P 2  with which the first terminal (collector terminal of upper IGBT in  FIG. 1 ) of the semiconductor module  102  is connected. 
     The N-wire bus bar  140 N has a connection portion  141 N with which the other of the terminals of the condenser  121  is connected, a connection portion  142 N with which one of the terminals of the condenser  122  is connected, a connection portion N 1  with which the second terminal (emitter terminal of lower IGBT in  FIG. 1 ) of the semiconductor module  101  is connected, and a connection portion N 2  with which the second terminal (emitter terminal of the lower IGBT in  FIG. 1 ) of the semiconductor module  102  is connected. 
     The AC-wire bus bar  140 AC has a connection portion AC 1  with which the third terminal (emitter terminal of upper IGBT and collector terminal of lower IGBT in  FIG. 1 ) of the semiconductor module  101  is connected and a connection portion AC 2  with which the third terminal (emitter terminal of upper IGBT and collector terminal of lower IGBT in  FIG. 1 ) of the semiconductor module  102  is connected. 
     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 P 1  of the semiconductor module  101  to the connection portions  141 P,  142 P of the condensers  121 ,  122  are shorter than distances from the connection portion P 2  of the semiconductor module  102  to the connection portions  141 P,  142 P of the condensers  121 ,  122 . Similarly, distances from the connection portion N 1  of the semiconductor module  101  to the connection portions  141 N,  142 N of the condensers  121 ,  122  are shorter than distances from the connection portion N 2  of the semiconductor module  102  to the connection portions  141 N,  142 N of the condensers  121 ,  122 . 
     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  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 . 
     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 . 
     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 . 
     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 . 
     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 . 
     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) 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. 
     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. 
     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 . 
     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. 
     Second Embodiment 
     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  100 A (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. 
     &lt;Power Conversion Unit  100 A&gt; 
     A configuration of a power conversion unit  100 A 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  100 A according to the second embodiment. 
     As is shown in  FIG. 4 , the power conversion unit  100 A 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  100 A 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. 
     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. 
     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  100 A. 
     Third Embodiment 
     Next, the power conversion device S of the third embodiment is explained. The power conversion device S of the third 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 third embodiment has a power conversion unit  100 B (as illustrated in  FIG. 5  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 third embodiment and not explained. 
     &lt;Power Conversion Unit  100 B&gt; 
     A configuration of a power conversion unit  100 B 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  100 B according to the third embodiment. 
     As is shown in  FIG. 5 , the power conversion unit  100 B 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  100 B 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. 
     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). 
     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  100 B. 
     &lt;Modification&gt; 
     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. 
     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. 
     Although there are a couple of condensers included in the power conversion unit  100  ( 100 A,  100 B) 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 equal to 3. In addition, the power conversion unit  100  ( 100 A,  100 B) 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. 
     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. 1 . 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. 
     The heat pipes  305 ,  306  of the power conversion unit  100 B 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.