Patent Publication Number: US-2021190552-A1

Title: Power conversion apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior PCT Patent Application No. PCT/JP2018/16736, filed on Apr. 25, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The embodiment of the present invention relates to a power conversion apparatus. 
     BACKGROUND ART 
     A power conversion apparatus that converts a large capacity of power may handle a high voltage or a large current of about 3,800 Vrms AC. In that case, a board structure is often adopted. Further, in the power conversion apparatus, it is necessary to reduce the inductance in order to suppress a surge voltage. In this case, input side AC bus bar, output bus bar, and DC bus bar need to be insulatively coated to form a close contact structure. Therefore, inside of the power conversion apparatus has a complicated bus bar structure. 
     Forced air cooling is generally used in such power conversion apparatus. Forced air cooling power conversion apparatus is generally installed indoors and is used in a defined ambient environment. In this case, it is undeniable that an arc flash may occur in the board due to unexpected deterioration of the surrounding environment. Here, a short circuit phenomenon due to arc discharge through air is referred to as arc flash. 
     As an explosion-proof device that has taken measures against arc flash, main components of the explosion-proof device are classified into a first case and a second case according to the explosion-proof specification level, and the explosion-proof device that has taken the explosion-proof measures accordingly, is disclosed (for example, See Patent Document 1). 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent document 1: Japanese Patent Publication No. 2009-103650 
       
    
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, in recent years, even in an inverter that configures the power conversion apparatus, when an unexpected arc flash occurs in the power conversion apparatus, a structure that does not release the high temperature gas or pressure wave accompanying it to the operation surface has come to be required. In this respect, the device described in Patent Document 1 does not disclose a method of appropriately releasing the internal pressure of the device when explosion trouble occurs. Therefore, in the case of explosion protection due to unexpected explosion trouble that is not in the explosion protection specifications or deterioration of the device, the device has a safety problem because it cannot release the pressure inside the device properly. 
     In addition, there is a demand from the user of the power conversion apparatus to reduce the installation area, and small-sized high-density mounting is applied. In this case, if an accident occurs in which an arc flash generates, the energy density due to the arc flash increases because of the size reduction, and there is a problem that parts in the device may be damaged. 
     Means for Solving the Problem 
     In order to achieve the above object, a power conversion apparatus according to claim  1  of the present invention comprises a first conductor portion, a second conductor portion, an openable/closable board door, a vent hole arranged in the board door, and a flapper section on a ceiling part, wherein, the first conductor portion, which is arranged at a place where arc flash is not desired to be generated, is subjected to a first processing for relaxing the surface electric field of the conductor as compared with the second conductor, the vent hole has a shutter part composed of a plurality of louvers consisting of a fixed part that makes a fulcrum composed of a plurality of metal plates, and a movable part, the plurality of louvers has the movable part arranged so as to overlap the fixed part of the other louver when the movable part of one louver rotates in the outer direction of the power conversion apparatus, and the plurality of louvers are configured to ensure air permeability from the outside to the inside of the power conversion apparatus when the movable part of the plurality of louvers rotates in the inner direction of the power conversion apparatus, and the flapper section includes, a window portion between the inside and the outside of the power conversion apparatus, a frame body arranged around the window portion, and two doors fixed to both ends of the frame body so as to be opened and closed in a double door shape toward the outside of the power conversion apparatus at the central portion of the window portion. 
     Effects of the Invention 
     According to the present invention, it is possible to suppress the occurrence of arc flash in a portion of the power conversion apparatus which is not desired to be generated, even under the condition that arc flash occurs. Further, it is possible to provide a power conversion apparatus capable of improving safety and reducing damage to the inside of the apparatus by releasing the pressure inside the apparatus to the outside by a flapper section arranged on the ceiling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are an outline views of a board composed of a plurality of board units constituting the power conversion apparatus according to the first embodiment.  FIG. 1A  is a plan view, and  FIG. 1B  is a front view. 
         FIGS. 2A, 2B and 2C  are side perspective views showing a state when an arc flash occurs in the board unit shown in  FIGS. 1A and 1B .  FIG. 2A  shows a state at the time when an arc flash generates.  FIG. 2B  shows a state in which louvers  32   a  and  32   b  of an explosion-proof shutter part  32  are closed due to the pressure increase in the board caused by the arc flash. 
         FIG. 2C  shows a state in which the flapper section  31  and the fan cover portion  33  are opened due to the pressure increase in the board caused by the explosion-proof shutter part  32  being closed in  FIG. 2B . 
         FIG. 3A  is an external view of the explosion-proof shutter part used for the front door of the board unit shown in  FIGS. 1A and 1B  or  FIGS. 2A, 2B and 2C .  FIG. 3B  and  FIG. 3C  are diagrams for explaining the operation when the arc flash occurs.  FIG. 3B  is a schematic side view for explaining the structure of the explosion-proof shutter part  32 , showing a state before an arc flash occurs.  FIG. 3C  is a schematic side view for explaining the structure of the explosion-proof shutter part  32 , and is a diagram showing a state in which the louvers  32   a  and  32   b  are closed due to arc flash generation and board pressure. 
         FIG. 4A  is an external view when the flapper section  31  arranged on the ceiling of the board unit  30  is closed.  FIG. 4B  is an external view when the flapper section  31  arranged on the ceiling of the board unit  30  is open.  FIG. 4C  is a side view of the door of the flapper section  31  when viewed from A 1 -A 2  in  FIG. 4A . 
         FIG. 5  is an external view of a fan cover portion  33  used on the ceiling of the board unit shown in  FIGS. 2A, 2B and 2C , and a diagram for explaining the operation when an arc flash occurs. 
         FIG. 6  is a diagram showing a case where an insulating plate  35  is arranged between a conductor in the board unit shown in  FIGS. 1A and 1B  and a front door. 
         FIG. 7  is an example of a test result of a change in in-board pressure when an arc flash is generated in the power conversion apparatus. 
     
    
    
     EMBODIMENT TO PRACTICE THE INVENTION 
     Hereinafter, embodiment of the present invention will be described with reference to the drawings. 
     Embodiment 1 
       FIGS. 1A and 1B  is an external view of a power conversion apparatus  100  in which a plurality of board units forming the power conversion apparatus according to the first embodiment are arranged in a row.  FIG. 1A  is a plan view of the power conversion apparatus  100 , and  FIG. 1B  is a front view of the power conversion apparatus  100 . Hereinafter, the components related to the arc flash countermeasure according to the present embodiment will be mainly described. 
     The illustrated power conversion apparatus  100  is an example of a case where it is configured by four board units  10 ,  20 ,  30 , and  40  (hereinafter referred to as board units  10  to  40  when the board units are not distinguished). Each board unit  10 - 40  has a rectangular parallelepiped shape, and has a front door that can be opened and closed is provided on the front side of each board unit  10 - 40  so that an operator can access the inside of each board unit  10 - 40 . Further, under the front door, explosion-proof shutter parts  12 ,  22 ,  32 , and  42  forming a vent are arranged. 
     Also, flapper sections  21 ,  31 , and  41  are arranged on the ceiling parts of the board units  20 ,  30 ,  40 , respectively. Fan cover portions  33  and  43  are further arranged on the ceiling parts of the board units  30  and  40 . 
       FIGS. 2A, 2B and 2C  are a side perspective view showing a state where the arc flash  37  occurs in the board shown in  FIGS. 1A and 1B . Here, a case where an arc flash occurs inside the board unit  30  will be mainly described. 
     A front door  36  is arranged on the front of the board unit  30 . An insulating plate  35  is arranged between the front door  36 , which is the operation surface, and the front side conductor  34   a  in the board. An upper conductor  34   b  is arranged near the flapper section  31 . Another upper conductor  34   c  is arranged below the fan cover portion  33 . Further, a semiconductor unit  38  and the like are stored in the board. 
       FIG. 2A  shows a state immediately after the arc flash  37  occurs inside the board unit  30 . 
       FIG. 2B  shows a state in which the arc flash  37  is generated inside the board unit  30  and the louvers  32   a  and  32   b  forming the explosion-proof shutter part  32  are closed due to the pressure inside the board (see  FIG. 3C ). The closing of the louvers  32   a  and  32   b  prevents the arc flash  37  from being emitted from the explosion-proof shutter part  32  toward the front door  36 . 
       FIG. 2C  shows a state in which the flapper section  31  and the fan cover portion  33  are opened due to the pressure increase in the board due to the closing of the explosion-proof shutter part  32  in  FIG. 2B . 
       FIG. 3  is an external view of the explosion-proof shutter part  32  used for the door of the board shown in  FIGS. 1A and 1B  or  FIGS. 2A, 2B and 2C , and a diagram for explaining the operation when the arc flash occurs. 
       FIG. 3A  is an external view of the explosion-proof shutter part  32 , and the drawing on the left side is an external view of the explosion-proof shutter part  32  as viewed from the outside of the board unit. 
     The drawing on the right side is an external view of the explosion-proof shutter part  32  as viewed from the inside of the board unit. 
       FIG. 3B  is a schematic side view for explaining the structure of the explosion-proof shutter part  32 , and is a diagram showing a state before the arc flash occurs. 
     The explosion-proof shutter part  32  is composed of a plurality of movable louvers  32   a  and a plurality of movable louvers  32   b  in a frame body  32   c  made of metal. In this embodiment, the movable louvers  32   a  and  32   b  are each composed of five movable louvers made of metal. 
     The movable louver  32   a  is composed of a fixed portion  32   a   1  and a movable portion  32   a   2 , which are formed by bending a substantially rectangular thin plate-shaped metal in parallel with the long side, and is bent so that the movable portion  32   a   2  is larger than the fixed portion  32   a   1 . Here, the thin plate-shaped metal is, for example, a metal plate having a thickness of about 1 mm. 
     The movable louver  32   a  is fixed and attached to the frame body  32   c  with the fixed portion  32   a   1  so that the movable portion  32   a   2  is located above the fixed portion  32   a   1 . In the movable louver  32   a , the movable portion  32   a   2  is bent and attached to the board unit side, and the movable portion  32   a   2  can be moved in a direction in which the movable portion  32   a   2  and the fixed portion  32   a   1  are in a single plane, namely, that can be moved in the direction of outside the board. 
     The movable louver  32   a  has a movable portion  32   a   2  that is bent and attached to the board unit side. At the bent portion, the movable portion  32   a   2  is movable in a direction in which the movable portion  32   a   2  and the fixed portion  32   a   1  form a single plane, that is, to the board outside direction. In the explosion-proof shutter part  32 , a part of the lower end of the fixed part  32   a   1  of the one louver  32   a  is arranged so as to overlap a part of its upper end of the other louver  32   a   2  when the movable part  32   a   2  arranged below the louver  32   a  is moved in the outboard direction. 
     The movable louver  32   b  is composed of a fixed portion  32   b   1  and a movable portion  32   b   2 , which is formed by bending a substantially rectangular plate-shaped metal in parallel with the long side, and is bent so that the movable portion  32   b   2  is larger than the fixed portion  32   b   1 . 
     The movable louver  32   b  is fixed and attached to the frame body  32   c  with the fixed portion  32   a   1  such that the movable portion  32   a   2  is located below the fixed portion  32   b   1 . 
     In the movable louver  32   b , the movable portion  32   b   2  is bent and attached to the board unit side, and the movable louver  32   b  is movable in a direction in which the bent portion and the fixed portion  32   b   1  are in a single plane, that is, to the board outside direction. In the explosion-proof shutter part  32 , a part of the lower end of the fixed part  32   b   1  of one louver  32   b  is arranged so as to overlap a part of upper end of the movable part  32   b   2  of the other louver  32   b  when the movable part  32   b   2  arranged below the louver  32   b  is moved to the outside of the board. 
     In this embodiment, the movable louver  32   a  and the movable louver  32   b  are configured to have a double structure, the movable louver  32   a  is arranged outside the board, and the movable louver  32   b  is arranged inside the board. 
     Before the arc flash occurs, since the air inside the board is discharged from the ceiling side by the operation of the exhaust fan on the ceiling of the board unit (not shown), the movable part  32   a   2  of the louver  32   a  and the movable part  32   b   2  of the louver  32   b  are held in a bent state toward the inside of the board. Therefore, a gap is formed between one movable louver  32   a  and other movable louver  32   a , and between one movable louver  32   b  and other movable louver  32   b  that that is overlapped each other, respectively. As a result, air permeability between the inside of the explosion-proof shutter part  32  and the outside of the explosion-proof shutter part  32  is ensured. In the illustrated example, the wind flows from the outside to the inside of the explosion-proof shutter part in the direction indicated by the arrow. 
       FIG. 3C  is a schematic side view for explaining the structure of the explosion-proof shutter part  32 , and is a diagram showing a state in which an arc flash occurs and the louvers  32   a  and  32   b  are closed by the pressure inside the board. When an arc flash occurs and the internal pressure of the board becomes higher than the external pressure, the movable portion  32   a   2  of the movable louver  32   a  and the movable portion  32   b   2  of the movable louver  32   b  are bent outside the board around the fixed portions  32   a   1  and  32   b   1 . As a result, in the explosion-proof shutter part  32 , a part of the lower end of the fixed part  32   a   1  of one louver  32   a  overlaps a part of the upper end of the movable part  32   a   2  of one louver  32   a  arranged below the other louver  32   a . Similarly, in the explosion-proof shutter part  32 , a part of the lower end of the movable part  32   b   2  of one louver  32   b  overlaps a part of the upper end of the fixed part  32   b   1  of one louver  32   b  arranged below the other louver  32   b.    
     As a result, as shown in the figure, the two louvers  32   a  and  32   b  are arranged in a parallel state to prevent the arc or pressure due to the arc flash generated in the board from being released from the inside of the louvers  32   a  and  32   b  to the outside. The same operations are applied to the louvers of the explosion-proof shutter parts  12 ,  22 , and  42  arranged in the other board units  10 ,  20 , and  40 , respectively. 
     With such a structure, it becomes difficult to blow out the arc, high temperature gas, pressure wave, etc. due to the arc flash generated in the power conversion apparatus from the front of the power conversion apparatus. 
     In the embodiment shown in  FIG. 3 , the explosion-proof shutter part  32  is composed of the double shutter of the louver  32   a  and the louver  32   b , but only one louver  32   a  or the louver  32   b  may be used. Further, in the embodiment, one metal plate is bent to form the louvers  32   a  and  32   b , but it may be configured that the fixed portions  32   a   1  and  32   b   1  are formed by round rod-shaped shafts, and the plate-shaped movable portions  32   a   2  and  32   b   2  are formed on the fixed portions  32   a   1  and  32   b   1  so that they can rotate around each axis of the shafts. 
       FIG. 4  is an external view of the flapper section  31  installed on the ceiling of the board unit shown in  FIGS. 1A and 1B  and a diagram for explaining the operation when an arc flash occurs. Here, the flapper section  31  arranged on the ceiling of the board unit  30  will be mainly described, but even if the flapper sections arranged on the ceilings of other board units have different shapes, arrangement positions, etc., their functions and operations are basically same. 
       FIG. 4A  is an external view when the flapper section  31  arranged on the ceiling of the board unit  30  is closed. The normal state is the state shown in  FIG. 4A .  FIG. 4B  is an external view when the flapper section  31  arranged on the ceiling of the board unit  30  is open. 
     The flapper section  31  has a window portion  31   c , a frame body  31   d  arranged around the window portion  31   c , and two doors  31   a  and  31   b  fixed to both ends of the frame body  31   d  by hinges  31   e  and  31   f.    
     Since the doors  31   a  and  31   b  are for opening and closing the window  31   c , a door having a size necessary for opening and closing the window  31   c  is required. In this embodiment, the doors  31   a  and  31   b  are fixed to the frame body  31   d  by hinges  31   e  and  31   f , respectively, so that the doors  31   a  and  31   b  can be opened and closed like a double door in the central portion of the window  31   c . Further, the material of the doors  31   a  and  31   b  of the present embodiment is made of sheet metal having a thickness of 1.6 mm, and the tip portions of the two doors are arranged so that they overlap in the central part of the window portions  31   c  when the two doors  31   a  and  31   b  are closed. 
     Further, both side portions of the door are bent inward in an L-shape and are configured to come into contact with a frame body  31   d  surrounding the window portion  31   c , and a predetermined airtightness is kept when the doors  31   a  and  31   b  are closed. The predetermined airtightness is a level of airtightness that does not hinder the required intake of air from the explosion-proof shutter parts  12 ,  22 ,  32 , and  42  when the exhaust fan of the board unit (not shown) is operating.  FIG. 4C  is a side view of the door of the flapper section  31  when viewed from A 1 -A 2  in  FIG. 4A . The tip portion of the door  31   a  of the present embodiment is arranged so as to overlap the tip portion of the door  31   b.    
     When the arc flash occurs, the flapper section  31  can release the doors  31   a  and  31   b  as shown in  FIG. 4B  due to the pressure increase in the board, and release the expanded air in the board unit. 
       FIG. 5  is an external view of the fan cover portion  33  arranged on the ceiling of the board unit shown in  FIGS. 2A, 2B and 2C  and a diagram for explaining the operation when an arc flash occurs. Here, the fan cover portion  33  arranged on the ceiling of the board unit  30  will be mainly described. 
     The fan cover portion  33  is configured to have a frame body  33   a  and a door  33   b.    
     The frame body  33   a  according to the present embodiment is configured in a box shape, and an exhaust fan (not shown) is housed inside the frame body  33   a . There is a space between the frame body  33   a  and the door  33   b.    
     The door  33   b  is rotatably fixed to one end of the frame body  33   a  by a hinge  33   c . The door  33   b  is normally in the state shown in  FIG. 5 , and the exhaust gas of the exhaust fan is discharged to the outside of the board unit from the space between the frame body  33   a  and the door  33   b.    
     When an arc flash occurs, the door  33   b  can rotate in the direction of arrow B in the drawing due to the pressure increase in the board. By rotating the door  33   b , the area of the opening of the exhaust fan portion increases, and the pressure increase in the board can be suppressed. 
       FIG. 6  is a detailed explanatory view of the case where the insulating plate  35  is arranged between the conductor  34   a  near the front surface of the board shown in  FIGS. 2A, 2B, and 2C  and the metal front door  36  of the board unit  30 . A large current flows in the arc flash. Therefore, to prevent dielectric breakdown in places where people do not want to generate an arc flash, such as parts that may come close to the power conversion apparatus during operation, for example, near the front door in the board, the sharp end of the conductor end is removed, and the conductor is rounded to make the electric field relatively weaker than other parts (first end processing). 
     On the other hand, in order to prevent the arc flash from occurring in an unintended place, a relatively safe place is set even if an arc flash occurs. For example, the electric field of the conductor is strengthened relative to other parts so that dielectric breakdown can be easily occurred near the pressure release opening at the top of the board when an overvoltage occurs. Therefore, the shape of a part of the upper part of the board is processed into a sharp state (second processing). 
     In this embodiment, in order to prevent dielectric breakdown from the conductor  34   a  on the front surface of the board to the front door  36 , or to prevent dielectric breakdown between the conductors, the first tip processing to make a rounded portion for removing a sharp end portion of the conductor  34   a  is provided. The insulating plate  35  is arranged between the conductor  34   a  and the front door  36  in order to secure the further insulating property while performing the first tip processing. In addition, the conductor  34   b  near the flapper section  31  on the upper part of the board and the conductor  34   c  near the fan cover portion  33  are subjected to the second processing in which a part is sharpened. 
     By performing such processing, when the conductors  34   a ,  34   b , and  34   c  have the same potential, the surface electric field of the conductor  34   a  becomes weaker than that of the conductors  34   b  and  34   c . Therefore, since the probability of dielectric breakdown at the portion of the conductor  34   a  is lower than the probability at the portions of the conductors  34   b  and  34   c , the occurrence probability of arc flash at the portion of the conductor  34   a  can be reduced. 
     The insulating plate  35  arranged between the conductor  34   a  and the front door  36  is arranged at a position close to the conductor  34   a  side (see  FIGS. 2A, 2B, and 2C ). 
     With such a configuration, if an overvoltage occurs in the power conversion apparatus  100  for some reason, the probability that an arc flash will occur in the conductor  34   a  will be lower than the probability that it will occur in the conductor  34   b  or the conductor  34   c . Further, since the flapper section  31  and the fan cover portion  33  are present in the vicinity of the conductors  34   b  and  34   c , it is possible to reduce the influence on the person near the front door  36  of the board unit  30  when an arc flash occurs. Because the pressure wave generated by opening the doors  31   a  and  31   b  and the fan cover portion  33  is discharged from the upper portion of the board unit  30  to the outside. 
       FIG. 7  shows an example of a test result of changes in the board pressure when an arc flash is generated in the power conversion apparatus in the embodiment of the power conversion apparatus according to the present invention. The vertical axis is the pressure difference between the outside and inside of the board, and the horizontal axis is the time axis. 
     As shown in  FIG. 7 , it is shown that the rise of the pressure inside the board is suppressed by the effect of the flapper section and the fan cover portion that can release pressure on the upper part of the board. 
     While certain embodiment have been described, the embodiment has been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiment described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiment described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     As described above, according to the present invention, it is possible to provide the power conversion apparatus that can prevent the high temperature gas and the pressure wave due to the arc flash generated in the board from being emitted to the operation surface and to reduce the damage to the components in the board. 
     EXPLANATION OF SYMBOLS 
     
         
           100  power conversion apparatus (board) 
           10 ,  20 ,  30 ,  40  board unit 
           12 ,  22 ,  32 ,  42  explosion-proof shutter part 
           31 ,  41  flapper section 
           31   a ,  31   b  doors 
           31   c  window portion, 
           31   d  frame body 
           32   a ,  32   b  movable louver 
           33 ,  43  fan cover portion 
           33   a  frame body 
           33   b  door 
           33   c  hinge 
           34  conductor 
           35  insulating plate 
           36  housing 
           37  arc flash