JP5205595B2 - Power converter and motor drive system - Google Patents

Description

  The present invention relates to the arrangement of power modules and capacitors arranged in an inverter.

A power module, which is a main component of a power conversion device such as an inverter, and has a configuration in which two power transistors are connected in series and a diode is connected in antiparallel to each of the power transistors, is also called a switching module or a semiconductor module. Therefore, it plays an important role in converting the direct current input from the power source into alternating current and outputting it. As an invention relating to the arrangement of the power module, there is conventionally known an invention such as that described in Patent Document 1, for example.
In the inverter device described in Patent Document 1, a power module is radially arranged around a DC input unit that is connected to a power source and includes positive and negative terminals. This power module is necessary for each AC phase, and at least as many power modules as the number of AC phases are required.
If the number of alternating current phases is three, the power conversion device includes three power modules. When these power modules convert direct current into alternating current, a high-frequency ripple current is generated with switching. A surge voltage is generated when the power module is turned off. For this reason, it is necessary to provide a capacitor that smoothes the ripple current and absorbs the surge voltage. In the inverter device described in the cited document 1, positive and negative electrodes integrally molded with an insulating layer interposed therebetween are arranged on the upper part of the power module, a capacitor is arranged on the upper part of the electrode, each power module, Each capacitor is connected with a low impedance, and a small space power converter is provided.
JP-A-7-245968

  However, the conventional inverter device still has problems as described below. In other words, even if these power modules and capacitors are connected with low impedance, the load on the capacitors themselves is not reduced and it does not contribute to downsizing of the capacitors themselves.

  In view of the above circumstances, the present invention proposes a power converter that can reduce the size of a capacitor while avoiding an increase in surge current to the power module.

For this purpose, the power converter according to the invention is as described in claim 1,
A power converter for converting a DC current into a polyphase AC current and supplying the same to a multiphase AC motor; a plurality of power modules for converting a DC current input from the DC terminal into a polyphase AC current and outputting the same to the AC terminal; The power of each phase is set so that the impedance of the capacitor disposed close to each power module, the power module in one phase, and the power module in the other phase is smaller than the impedance between the power module and the capacitor. And a bus bar that electrically connects modules and a plurality of capacitors.

  According to such a configuration of the present invention, the impedance of the interphase current path that electrically connects the power module provided in one phase and the power module provided in the other phase has the power module and Since it is configured to be smaller than the impedance of the in-phase current path that electrically connects the capacitor, it becomes possible to increase the cancellation of the ripple current between the phases, and as a result, the ripple current flowing through the capacitor can be reduced. Can do. Therefore, it is possible to reduce the size of the capacitor itself, and consequently, it is possible to reduce the size of the power converter. In addition, since the power module and the capacitor are disposed close to each power module, the surge current can be reduced in advance by connecting the capacitor to each power module with a low impedance, and the capacitor itself can be further reduced. It can be downsized.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 is a longitudinal sectional view of a multiphase AC motor provided with a power converter according to an embodiment of the present invention. The multiphase AC motor 12 is a well-known one that is operated by a plurality of phases of alternating current consisting of three or more phases. The multiphase AC motor 12 includes a motor case 13 that forms an outline of the multiphase AC motor 12, a cylindrical rotor 14 that is rotatably supported by the motor case 13, and a rotor 14 that surrounds the rotor 14. The hollow cylindrical stator 15 and the power conversion device 1 for supplying electric power to the stator.

  A plurality of stator cores 16 are arranged on the inner peripheral surface of the stator 15 at equal intervals in the circumferential direction. The base end of the stator iron core 16 is fixed to the inner peripheral surface of the stator 15, and the front end of the stator iron core 16 is directed to the outer peripheral surface of the rotor 14 through a slight gap 19. A conductive wire is wound around each stator core 16 to form a motor coil 17. And the conducting wire end of the motor coil 17 is connected to the power module of the power converter 1 disposed adjacent to the end face of the stator 15. The power conversion device 1 has an annular shape, and the rotation shaft 18 of the rotor 14 passes through the center thereof.

  The power converter 1 includes a plurality of power modules 2, 3, 4 and capacitors 5, 6, 7. Then, the power module and the capacitor are paired, and the pair is disposed for each phase. The power cable 20 electrically connects a storage battery (not shown) that supplies power to the multiphase AC motor 12 and the power conversion device 1. A direct current is supplied to the power modules 2, 3, 4 through the bus bar 8. As will be described later, the bus bar 8 electrically connects the power modules 2, 3, 4 to each other and electrically connects the paired power modules 2, 3, 4 and the capacitors 5, 6, 7.

  The power modules 2, 3, and 4 are made of semiconductor elements and perform a switching operation to convert direct current into multiphase alternating current. Capacitors 5, 6, and 7 reduce unnecessary current changes such as surge currents and ripple currents associated with the switching operation of the paired power modules 2, 3, and 4.

  The power conversion device 1 is also called an inverter, and receives power from a DC power source (not shown) such as a storage battery and outputs a multiphase AC current to the multiphase AC motor 12. This inverter is generally laid out (placed) at a position away from both the storage battery and the multiphase AC motor. In this embodiment, however, the power converter 1 is mounted on the motor case 17 of the multiphase AC motor 12 as shown in FIG. Direct attachment and integration. Such an inverter integrated motor 12 is referred to as an electromechanical integrated motor.

  FIG. 2 is a diagram illustrating a schematic configuration of the power conversion device 1 according to the present embodiment. This power conversion device 1 converts direct current into three-phase alternating current, and includes a U-phase power module 2, a V-phase power module 3, a W-phase power module 4, and independent capacitors 5 and 6 for each phase. , 7. As shown in FIG. 2, the capacitors 5, 6, 7 and the power modules 2, 3, 4 are arranged apart from each other compared to the distance between the power modules 2, 3, 4.

The power modules 2, 3, and 4 have the same structure, and two power transistors (not shown) such as switching elements IGBT, GTO thyristors, and MOSFETs are connected in series, and diodes are connected to these power transistors in antiparallel. This is a known semiconductor module. Each power module 2, 3, 4 includes a positive terminal (also referred to as a P terminal), a negative terminal (also referred to as an N terminal), and AC output terminals U, V, and W, respectively.
Bus bar 8 electrically connects the positive terminal of U-phase power module 2 and the positive terminal of V-phase power module 3. Bus bar 8 electrically connects the positive terminal of V-phase power module 3 and the positive terminal of W-phase power module 4. Bus bar 8 electrically connects the positive terminal of W-phase power module 4 and the positive terminal of U-phase power module 2. The bus bar 8 electrically connects the positive terminals of the power modules 2, 3, and 4 and the positive terminal of the DC voltage source 10 (not shown).

  The bus bar 8 is plate-shaped, the front surface connects the positive terminals of the power modules 2, 3 and 4 and the positive terminal of the DC voltage source, the back surface connects these negative terminals, and an insulating layer between both surfaces. It is a three-layer structure interposing. Thereby, the bus bar 8 electrically connects the negative terminal of the U-phase power module 2 and the negative terminal of the V-phase power module 3. The bus bar 8 electrically connects the negative terminal of the V-phase power module 3 and the negative terminal of the W-phase power module 4. Bus bar 8 electrically connects the negative terminal of W-phase power module 4 and the negative terminal of U-phase power module 2. The bus bar 8 electrically connects the negative terminals of the power modules 2, 3, and 4 to the negative terminal of the DC voltage source 10 (not shown). The positive terminals and the negative terminals of the power modules 2, 3, and 4 are electrically insulated.

  As described above, the bus bar 8 includes a power module phase current path for electrically connecting the U / V phase power modules 2 and 3, and between the power module phases for electrically connecting the V / W phase power modules 3 and 4. A current path is provided, and a power module inter-phase current path for electrically connecting the W / U phase power modules 4 and 2 is provided. Thereby, the bus bar 8 constitutes a power module inter-phase current path that electrically connects the positive terminal or the negative terminal of the power module in one phase and the positive terminal or the negative terminal of the power module in another phase.

  Furthermore, the bus bar 8 electrically connects the positive terminal of the U-phase power module 2 and the positive terminal of the capacitor 5. Bus bar 8 electrically connects the positive terminal of V-phase power module 3 and the positive terminal of capacitor 6. Bus bar 8 electrically connects the positive terminal of W-phase power module 4 and the positive terminal of capacitor 7.

  Similarly, the bus bar 8 electrically connects the negative terminal of the U-phase power module 2 and the negative terminal of the capacitor 5. Bus bar 8 electrically connects the negative terminal of V-phase power module 3 and the negative terminal of capacitor 6. Bus bar 8 electrically connects the negative terminal of W-phase power module 4 and the negative terminal of capacitor 7. Note that the positive terminal and the negative terminal are electrically insulated. In this way, the power module 2 and the capacitor 5 are arranged in the U phase of the power converter 1 as a pair. Further, the power module 3 and the capacitor 6 are arranged in the V phase of the power converter 1 as a pair. Further, the power module 4 and the capacitor 7 are arranged in the W phase of the power conversion device 1 as a pair.

  Thus, the bus bar 8 has an in-phase current path for electrically connecting the U-phase power module 2 and the capacitor 5, and an in-phase current path for electrically connecting the V-phase power module 3 and the capacitor 6. , An in-phase current path for electrically connecting the W-phase power module 4 and the capacitor 7 is provided. As a result, the bus bar 8 forms an in-phase current path that electrically connects the power modules 2, 3, 4 and the capacitors 5, 6, 7 in each of the U-phase, V-phase, and W-phase.

  As described above, the bus bar 8 is obtained by previously combining a plurality of current paths by shape processing. Specifically, cable-like conductors are gathered together in an appropriate length, thin plate-like conductors are punched into appropriate shapes and bonded together under insulation, and other conductor materials are appropriately shaped, etc. The bus bar 8 is manufactured by the following. The impedance of the current path between the power modules is proportional to the distance between the power modules 2, 3, and 4, and is affected by the shape of the bus bar 8. Further, the impedance of the U-phase current path in the U phase is proportional to the distance in the capacitor phase between the power module 2 and the capacitor 5 and is also affected by the shape of the bus bar 8. The same applies to the V phase and the W phase.

  Here, the relationship between the ripple current and the surge current related to the power conversion device of this embodiment will be described with reference to FIGS. 3 and 4 are diagrams schematically showing the relationship between the ripple current and the surge current in the present invention.

  Describing along the configuration of the three-phase inverter schematically shown in FIG. 3, the power between the U-phase power module UM, the V-phase power module VM and the W-phase power module WM and the capacitors C1, C2 and C3 A ripple current and a surge current generated by the switching operation of the modules UM, VM and WM flow.

  At this time, the ripple current generated from each of the power modules UM, VM and WM is indicated by the arrow R1 extending in the horizontal direction in FIG. 3 if the power modules UM, VM and WM are electrically connected by the bus bar. As described above, ripple current cancellation occurs between the three phases. Then, the remaining ripple current that is not canceled flows in the capacitors C1, C2, and C3 as shown by an arrow R2 in the vertical direction of the drawing in FIG. Therefore, the capacitors C1, C2, and C3 need only have a small capacity corresponding to the remaining ripple current that is not canceled.

Canceling more ripple current between the three phases and reducing the ripple current flowing in the capacitors C1, C2, and C3 contributes to a reduction in the capacitance and size reduction of the capacitors C1, C2, and C3, and in turn reduces the size of the inverter device. Can be achieved.
In order to cancel the ripple current, it is necessary to increase the current flowing from the power module to the power module as compared to the current flowing from the power module to the capacitor. That is, the power modules may be connected with a low impedance, and the power module and the capacitor may be connected with a higher impedance.

On the other hand, when the power module and the capacitor are connected with high impedance, the surge current accompanying the surge voltage becomes high as shown in FIG. In other words, since the surge voltage flowing into the capacitor becomes higher according to the impedance, it is necessary to make the capacitor large.
That is, unnecessarily increasing the impedance between the power module and the capacitor in order to cancel the ripple current leads to an increase in the size of the capacitor.

  The effect of the above-described increase in the size of the capacitor becomes significant when the power modules are grouped into units and the capacitors are grouped into units, and these power module units and capacitor units are installed separately. A general capacitor increases the capacity by connecting a plurality of capacitors in parallel, but if the impedance to the power module is not evenly arranged between the capacitors connected in parallel, the impedance with the power module is small. The load is concentrated on the capacitor, and the life of the capacitor is shortened. Therefore, it is necessary to adjust the overall impedance according to the capacitor having the highest impedance, and the impedance tends to increase.

  In order to avoid the influence of the increase in the size of the capacitor due to the high impedance described above, it is desirable to disperse the capacitors and arrange them in the vicinity of the power module. That is, since the surge current and ripple current generated from the power module are basically equal for each module, the total capacity does not change even if the capacitors are dispersed. In addition, since the impedance can be set appropriately small for each capacitor, as a result, the current flowing through the capacitor is reduced, and the total capacity is reduced compared to the case where the capacitors are united together.

  In other words, in this embodiment, by disposing a capacitor for each power module, in order to make the path from each power module to the capacitor uniform, it is unnecessary to lengthen the distance between the power module and the capacitor, or the life of each capacitor varies. Will not occur.

  In the present embodiment, the shape of the bus bar 8 shown in FIG. 2 is processed so that the impedance of the power module inter-phase current path described above is smaller than the impedance of the intra-phase current path.

  That is, when attention is paid to the U-phase power module 2, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the U-phase power module 2 and the positive and negative terminals of the V-phase power module 3 is expressed as U-phase. A connection position of these terminals is provided at a position that is smaller than the impedance of the in-phase current path 9 that electrically connects the positive electrode / negative electrode terminal of the power module 2 and the positive electrode / negative electrode terminal of the capacitor 5. In addition, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the U-phase power module 2 and the positive and negative terminals of the W-phase power module 4 with the positive and negative terminals of the U-phase power module 2 Connection positions of these terminals are provided at positions where the impedance is smaller than the impedance of the in-phase current path 9 that electrically connects the positive and negative terminals of the capacitor 5.

  According to the present embodiment, since the impedance of the current path between the power modules is smaller than the impedance of the current path in the phase, it becomes possible to increase the cancellation of the ripple current between the UV phase and the UW phase. The flowing ripple current can be reduced. Therefore, the capacitor 5 can be reduced in size, and the power converter 1 can be reduced in size. In addition, by disposing the capacitors 5, 6, and 7 as described above, it is not necessary to unnecessarily increase the distance between the power module 2 and the capacitor 5 in the U phase, and the surge current to the power module 2 is increased. Can be avoided.

  Alternatively, when focusing on the V-phase power module 3, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the V-phase power module 3 and the positive and negative terminals of the U-phase power module 2 is expressed as V-phase. The impedance is made smaller than the impedance of the in-phase current path 10 that electrically connects the positive and negative terminals of the power module 3 and the positive and negative terminals of the capacitor 6. In addition, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the V-phase power module 3 and the positive and negative terminals of the W-phase power module 4 with the positive and negative terminals of the V-phase power module 3 The impedance is made smaller than the impedance of the in-phase current path 10 that electrically connects the positive and negative terminals of the capacitor 6.

According to the present embodiment, since the impedance of the current path between the power modules is smaller than the impedance of the current path in the phase, it becomes possible to increase the cancellation of the ripple current between the VU phase and the VW phase. The flowing ripple current can be reduced. Therefore, the capacitor 6 can be reduced in size, and the power converter 1 can be reduced in size. In addition, it is not necessary to increase the distance between the power module 3 and the capacitor 6 in the V phase, and an increase in surge current to the power module 3 can be avoided.

  Alternatively, when focusing on the W-phase power module 4, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the W-phase power module 4 and the positive and negative terminals of the U-phase power module 2 is expressed as W-phase. The impedance is made smaller than the impedance of the in-phase current path 11 that electrically connects the positive and negative terminals of the power module 4 and the positive and negative terminals of the capacitor 7. In addition, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the W-phase power module 4 and the positive and negative terminals of the V-phase power module 3 and the positive and negative terminals of the W-phase power module 4 The impedance is made smaller than the impedance of the in-phase current path 11 that electrically connects the positive and negative terminals of the capacitor 7.

  According to the present embodiment, since the impedance of the current path between the power modules is smaller than the impedance of the current path in the phase, it becomes possible to increase the cancellation of the ripple current between the WU phase and between the WV phases. The flowing ripple current can be reduced. Therefore, the capacitor 7 can be reduced in size, and the power converter 1 can be reduced in size. Further, by disposing the capacitors 5, 6, and 7 as described above, it becomes unnecessary to increase the distance between the power module 4 and the capacitor 7 in the W phase, and the surge current to the power module 4 increases. Can be avoided.

Preferably, when focusing on each of the power modules 2, 3, and 4 as described above, the terminal of the power module in one phase focused and the terminal of the power module in the other phase are electrically connected The impedance of the current path between the power modules to be used is the impedance of the current path in the phase electrically connecting the terminal of the power module and the terminal of the capacitor in the one phase and the internal impedance of the capacitor in the one phase. It is made smaller than the total impedance.
The U phase will be described as a representative. The impedance of the current path between the power modules that electrically connects the positive and negative terminals of the U phase power module 2 and the positive and negative terminals of the V phase power module 3 is represented by the in-phase current path 9. And the total impedance of the internal impedance of the capacitor 5 in the U phase. Moreover, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the U-phase power module 2 and the positive and negative terminals of the W-phase power module 4 is the impedance of the intra-phase current path 9 and the U-phase. It is set smaller than the total impedance with the internal impedance of the capacitor 5.

  Thus, by reducing the total impedance including the internal impedance of the capacitor 5, it is not necessary to set the impedance of the in-phase current path 9 by the bus bar 8 unnecessarily high, and the surge voltage can be reduced. Therefore, the capacitor 5 can be further reduced in size, and further reduction in the size of the power conversion device 1 can be realized.

  More preferably, the impedance of the U-phase current path 9, the impedance of the V-phase current path 10, and the impedance of the W-phase current path 11 are made equal to each other, so that The impedance of the current path is the same in all phases. As a result, fluctuations in the surge voltage are prevented, life variations of the capacitors 5, 6 and 7 are avoided, and stable power conversion is enabled.

  More preferably, the impedance of the current path between the power modules that electrically connects the positive and negative terminals of the U-phase power module 2 and the positive and negative terminals of the V-phase power module 3 and the positive and negative electrodes of the V-phase power module 3 The impedance of the power module inter-phase current path that electrically connects the terminal and the positive and negative terminals of the W-phase power module 4, and the positive and negative terminals of the W-phase power module 4 and the positive and negative terminals of the U-phase power module 2 In order to reduce the impedance of the current path between the power modules that electrically connect the power modules, the power module terminals are arranged on a virtual circle represented by a two-dot chain line in FIG.

  As described above, when setting the impedance of the in-phase current path to be larger than the impedance of the power module inter-phase current path, or simply setting the impedance of the in-phase current path to be larger, the surge current and ripple The current increases and the burden on the capacitor increases.

Therefore, it is desirable that the impedance of the intra-phase current path is made larger than that of the power module inter-phase current path by reducing the impedance of the power module inter-phase current path.
At this time, for example, in FIG. 4 in the power module inter-phase current path, the inter-phase current path can be set short between the adjacent power modules, but the U-phase power module UM and the W-phase power module WM Between, the current path between phases becomes relatively long, and the impedance is large.

  Therefore, as shown in FIG. 2, the distance between the terminals of the U-phase power module UM and the W-phase power module WM can be shortened by arranging the positive terminal of the power module on a virtual circle represented by a two-dot chain line. As a result, the impedance of the in-phase current path can be designed to be small.

  Further, in FIG. 2, the positive terminals and the negative terminals of the power modules 5, 6 and 7 are provided adjacent to each other. This is because, when considering the power module interphase current path, both the positive terminal and the negative terminal form a power module interphase current path, so in view of the design requirements of the power module interphase current path of the positive terminal or the negative terminal, This is because when the power module inter-phase current path with the minimum impedance is used, the other terminal inevitably needs to be arranged in the vicinity of one terminal.

  Therefore, in this embodiment, the positive electrode terminal and the negative electrode terminal are collectively provided on one end surface of the power module, and the one end surface of the power module is directed to the virtual circular inner diameter side shown in FIG.

  In order to make the impedance of the current path between the power modules the same for all phases, preferably, as shown in FIG. 2, all of the positive terminals of the positive terminals or the negative terminals of the power modules 2, 3, and 4 are connected. It is placed on a virtual circle represented by a dotted line. Alternatively, although not shown, all of the negative terminals 2, 3, and 4 are arranged on a virtual circle.

  In FIG. 2, it is needless to say that all the positive terminals may be arranged on one virtual circle, and all the negative terminals may be arranged on one virtual circle.

FIG. 5: is a figure which shows schematic structure about the power converter device which becomes the 2nd Example of this invention, (a) shows the top view of the power converter device 21. FIG. (B) shows the expansion | deployment side view when the power converter device 21 is cut | disconnected by the site | part shown with a dashed-dotted line in (a), and it sees in the direction of the arrow. Since the basic configuration of this embodiment is the same as that of the above-described one embodiment, the same members will be denoted by the same reference numerals and description thereof will be omitted, and different configurations will be described.
On the cooler 22, three power modules 2, 3, and 4 are arranged in the circumferential direction. That is, these 2, 3, and 4 are arranged on a common virtual circle. Then, a PN terminal is provided at the end of the power module 2, 3, 4 on the inner side of the virtual circle inner diameter. Furthermore, capacitors 5, 6, and 7 are arranged so as to correspond to these power modules 2, 3, and 4. Each terminal provided on each of these power modules 2, 3 and 4 indicated by P · N in FIG. 5A and each terminal of the capacitors 5, 6 and 7 is a disk-shaped bus bar 8 indicated by a dotted line. Are electrically connected. In this embodiment, all of the positive electrode terminal and the negative electrode terminal are arranged at equal intervals in the circumferential direction on a virtual circle represented by a two-dot chain line.

  As shown in FIG. 5, a positive terminal and a negative terminal are provided at one end of the modules 2, 3, and 4 main body. These terminals are arranged on a virtual circle represented by a two-dot chain line. Then, the other end portions 2T, 3T, and 4T of the modules 2, 3, and 4 main bodies that are not provided with terminals are arranged outside the virtual circle represented by a two-dot chain line. Thereby, the distance between terminals between different phases is shortened, and the impedance of the current path between the power modules can be reduced.

  FIG. 6: is a figure which shows schematic structure about the power converter device which becomes the 3rd Example of this invention, (a) shows the top view of the power converter device 31. FIG. (B) shows the side view when the power converter device 31 is seen in the direction of the arrow shown with a dashed-dotted line in (a). Since the basic configuration of this embodiment is also the same as that of the above-described embodiment, the same members will be denoted by the same reference numerals, description thereof will be omitted, and different configurations will be described. In this embodiment, all the positive terminals are arranged in a circumferential direction on a virtual circle represented by a two-dot chain line. Further, all the negative terminals are arranged in the circumferential direction on a virtual circle represented by a two-dot chain line.

  The embodiment shown in FIG. 6 will be described in comparison with the embodiment shown in FIG. 5 described above. In the embodiment shown in FIG. 6B, the positive terminal and the negative terminal of one power module 2 are arranged. The power module 2 is placed on the cooler 22 in such a posture that the connecting virtual line is perpendicular to the virtual circle shown in FIG. The same applies to the other power modules 3 and 4. Thereby, the distance between terminals between different phases becomes shorter and the impedance of the current path between power modules can be made smaller.

  FIG. 7: is a figure which shows schematic structure about the power converter device which becomes the 4th Example of this invention, (a) shows the top view of the power converter device 41. FIG. (B) shows the side view when the power converter device 41 is seen in the direction of the arrow shown by a dashed-dotted line in (a). Since the basic configuration of this embodiment is also the same as that of the above-described embodiment, the same members will be denoted by the same reference numerals, description thereof will be omitted, and different configurations will be described. 7A and 7B specifically show the configuration of the bus bar 8. That is, the bus bar 8 includes a thin plate-shaped bus bar 8P for connecting the positive terminals provided in the power modules 2, 3, 4 and the capacitors 5, 6, 7 respectively, and a thin plate-shaped bus bar 8N for connecting the negative terminals. , Bonded together under insulation.

  As shown in FIG. 7, the positive and negative terminals of the power modules 2, 3, 4 are arranged at the center of the power converter 41. On the other hand, the positive and negative terminals of the capacitors 5, 6 and 7 are arranged at the outer edge of the power converter 41. The distance between the terminals of the power modules 2, 3, 4 is made shorter than the distance from the terminals of these power modules 2, 3, 4 to the terminals of the capacitors 5, 6, 7. Thereby, the impedance of the power module inter-phase current path can be made smaller than the impedance of the intra-phase current path.

  FIG. 8 is an enlarged longitudinal sectional view showing a connection portion with a terminal in the bus bar 8 shown in FIG. 7B. As shown in FIG. 8, a bus bar 8 is provided above the power module 2. A positive terminal bus bar 8P is disposed on the lower surface of the bus bar 8, and a negative terminal bus bar 8N is disposed on the upper surface of the bus bar 8. Then, an insulating layer 8I is interposed between the two 8P and 8N, and these 8P, 8N and 8I are bonded together to produce a plate-like bus bar 8. However, the bus bar 8N is shaped to be one level lower as shown in FIG. 8 at the position where the negative electrode terminal is attached, and to be at the same height as the bus bar 8P. For this reason, a notch 8K is provided at a location where the negative electrode terminal is attached in the bus bar 8P as shown in FIG. A hole 8H is provided in a portion of the bus bar 8P where the positive electrode terminal is attached, and a hole 8H is provided in a portion of the bus bar 8N where the negative electrode terminal is attached. Then, the positive terminal is inserted into the hole 8H of the bus bar 8P and fastened with a bolt or the like. A negative terminal is inserted into the hole 8H of the bus bar 8N and fastened with a bolt or the like.

  FIG. 9: is a figure which shows schematic structure about the power converter device which becomes the 5th Example of this invention, (a) shows the top view of the power converter device 51. FIG. (B) shows the side view when the power converter device 51 is seen in the direction of the arrow shown with a dashed-dotted line in (a). Since the basic configuration of this embodiment is also the same as that of the above-described embodiment, the same members will be denoted by the same reference numerals, description thereof will be omitted, and different configurations will be described. The bus bar 8 shown in FIGS. 9A and 9B has a circular shape. In addition, about the shape of the location which attaches the terminal of power module 2,3,4 and the capacitor | condenser 5,6,7 to the bus bar 8, FIG. 8 mentioned above is used.

  FIG. 10: is a figure which shows schematic structure about the power converter device which becomes the 6th Example of this invention, (a) shows the top view of the power converter device 61. As shown in FIG. (B) shows the side view when the power converter device 61 is seen in the direction of the arrow shown with a dashed-dotted line in (a). Since the basic configuration of this embodiment is also the same as that of the above-described embodiment, the same members will be denoted by the same reference numerals, description thereof will be omitted, and different configurations will be described. The bus bars 8 shown in FIGS. 10A and 10B are also circular. Further, all of the positive terminals and the negative terminals of the power modules 2, 3, 4 are arranged on the virtual circle A indicated by a two-dot chain line at equal intervals in the circumferential direction. Thereby, the impedance of the current path between power modules can be made the same for all phases.

  Further, all of the positive terminals and the negative terminals of the capacitors 5, 6, and 7 are arranged on the virtual circle B indicated by a two-dot chain line at equal intervals in the circumferential direction. Thereby, the impedance of the in-phase current path in all phases can be made the same.

  Further, by configuring the bus bar 8 so as to be point-symmetric with respect to the center point of the circular power converter 61, the impedance of the power module inter-phase current path and the intra-phase current path can be made the same in all phases. It becomes possible.

  As shown in FIG. 10A, the diameter of the virtual circle A is made smaller than half the diameter of the second virtual circle B (more precisely, the distance between the virtual circle A and the virtual circle B). Thereby, the impedance of the power module inter-phase current path can be made smaller than the impedance of the intra-phase current path.

  In addition, about the shape of the location which attaches the terminal of power module 2,3,4 and the capacitor | condenser 5,6,7 to the bus bar 8 of the Example shown in FIG. 10, FIG. 8 mentioned above is used.

  FIG. 11 is a diagram showing a schematic configuration of a power converter according to a seventh embodiment of the present invention. Since the basic configuration of this embodiment is also common to the above-described embodiment and can have the above-described functions, the same members are denoted by the same reference numerals, the description thereof is omitted, and different configurations are provided. explain. In this power conversion device 71, the capacitor in the embodiment of FIG. 10 described above is divided into a plurality of parts, and the capacitor 5A, the capacitor 5B, the capacitor 5C, and the capacitor 5D are connected to the U-phase power module 2. Capacitor 6A, capacitor 6B, capacitor 6C and capacitor 6D are connected to V-phase power module 3. Capacitor 7A, capacitor 7B, capacitor 7C and capacitor 7D are connected to V-phase power module 3. These capacitors 5A to 7D are all the same.

  The group 5A, 5B, 5C, and 5D related to the capacitor 5 will be described as a representative. These 5A, 5B, 5C, and 5D may be connected in parallel, connected in series, or combined in parallel and connected in series. May be.

  The impedance of the U-V phase power module interphase current path described above is smaller than the impedance of the in-phase current path that electrically connects the groups 5A, 5B, 5C, and 5D related to the capacitor 5 and the U phase power module 2. Further, the impedance of the above-described U / W-phase power module inter-phase current path is also smaller than the impedance of the intra-phase current path that electrically connects the groups 5A, 5B, 5C, and 5D related to the capacitor 5 to the U-phase power module 2. .

  12 and 13 are perspective views showing the actual configuration of the power converter according to the embodiment of the present invention. The power conversion device 81 according to this embodiment is an annular body and can output nine-phase polyphase alternating current, and nine power modules U1, V1, W1, U2, V2, W2, U3, V3, W3. And nine capacitors 83, an annular substrate 84, and a bus bar 8. A rotor rotation shaft (not shown) passes through the hole 85 provided in the center of the substrate 84. As shown in FIG. 12, nine capacitors 83 are arranged in the circumferential direction around the hole 85 and on one surface of the substrate 84. Nine power modules U1, V1, W1, U1, V2, W2, U3, V3, W3 are rotated clockwise on the other surface of the substrate 84 around the hole 85 as shown in FIG. Arrange.

A control terminal 86 extending from the power modules U1, V1, W1, U2, V2, W2, U3, V3, W3 penetrates the substrate 84 from the other surface and protrudes to one surface. The control terminal 86 receives a control command from a motor controller (not shown) and controls ON / OFF of the switching element of the power module. Each of the power modules U1, V1, W1, U2, V2, W2, U3, V3, and W3 includes a drive circuit 88, and generates a driving voltage for the switching element based on the control command received by the control terminal 86. In addition, a current sensor or the like is provided to detect a passing current of a coil connected to an AC terminal 89 (described later).
Each of the power modules U1, V1, W1, U2, V2, W2, U3, V3, and W3 includes an AC terminal 89, and is electrically connected to a motor coil of a multiphase AC motor (not shown). Then, multi-phase alternating current is output to each motor coil from each power module U1, V1, W1, U2, V2, W2, U3, V3, W3.
That is, when the power conversion device of the present embodiment is applied to the motor-integrated motor as shown in FIG. 1, if the motor is arranged so as to sandwich the power module, the power conversion device 81 and the motor coil of the multiphase AC motor are arranged. Therefore, the impedance between the motor coil and the power module can be minimized.

  A passage through which a coolant flows is provided inside the substrate 84. The refrigerant enters from the inlet 84I shown in FIG. 12, flows through the substrate 84, and exits from the outlet 84O. Thereby, the power converter 81 is cooled. According to the present embodiment, since the power modules U1 to W3 and the capacitor 83 are arranged with the substrate 84 having a cooling function interposed therebetween, the cooling efficiency can be improved. Moreover, the power converter 81 can be cooled using the axial space of the electromechanical motor.

  By providing a positive terminal P and a negative terminal N at the inner diameter end of the power modules U <b> 1 to W <b> 3, these terminals P and N are arranged in the vicinity of the hole 85. The terminals P and N of the power modules U <b> 1 to W <b> 3 are electrically connected to the hole 85 by a bus bar 8 having substantially the same diameter. The bus bar 8 has a plate shape in which the upper surface 8N and the lower surface 8P are bonded to each other via the insulating layer 8I as shown in FIG. 8, and a hole for the motor rotating shaft to penetrate through the center as shown in FIG. It is an annular shape with And the connection part 8C is extended from the annular | circular outer edge of the bus bar 8 to an outer diameter direction. The connecting portion 8C is electrically connected to a DC power source (not shown). A plurality of tongue pieces 8T are extended from the bus bar 8 in the circumferential direction in a direction perpendicular to the plane including the ring. In a state where the annular bus bar 8 is disposed close to the power modules U1 to W3 and attached to the power module terminals, these tongue pieces 8T pass through the holes 85 of the substrate 84, and the tips of the tongue pieces 8T are connected to the capacitor terminals. Connect electrically. Of course, the lower surface 8P of the bus bar 8 is electrically connected to the power module positive terminal and the capacitor positive terminal, and the upper surface 8N of the bus bar 8 is naturally connected to the power module negative terminal and the capacitor negative terminal.

  In the present embodiment, the positive and negative terminals of the power modules U1 to W3 are electrically connected to the capacitor terminals by the annular bus bar 8 serving as the interphase current path, so that the distance between the power modules is shortened to reduce the interphase current path. Impedance can be reduced. And since the tongue piece 8T which becomes the current path in the phase extends from the annular bus bar 8 and is electrically connected to the capacitor terminal, the distance between the power modules U1 to W3 and the capacitor 83 is increased. The impedance of the inner current path can be made larger than that of the interphase current path. In addition, since the bus bar 8 is configured by the annular shape and the tongue piece portion 8T in this way, the design of the impedance of the power converter 81 is facilitated.

  According to the present embodiment, the ripple current can be canceled by reducing the impedance of the interphase current path between adjacent power modules, for example, between U1 and V1 or between V1 and W1. Moreover, it becomes possible to cancel the ripple current between W1 and U1 by canceling the ripple current between W1 and U2, and between U1 and W3, and the interphase distance can be defined only between adjacent power modules. it can. As a result, the impedance of the interphase current path can be remarkably reduced as compared with a power conversion device including three power modules.

  Further, when the impedance of the interphase current path is made extremely small by using nine phases as described above, the balance of the impedance of the bus bar 8 is broken by a slight manufacturing error, and there is a concern that the load of the capacitor 83 may vary. Therefore, the above-described tongue piece 8T may be formed separately from the annular bus bar 8 instead of being integrally formed, and the separate bus bar 87 may be installed between the power module terminal and the capacitor terminal. In this case, the separate bus bar 87 becomes an in-phase current path. By using the separate bus bar 87, the life variation of the capacitor 83 can be suppressed.

  In addition, since the power conversion device 81 of this embodiment includes a plurality of power modules U1 to W3 and a capacitor 83, it is easy to form an annular body by arranging them in the circumferential direction. The motor 81 can be passed through the device 81. Therefore, the power conversion device 81 of this embodiment is suitable for an electromechanical integrated motor.

  In addition, the power converter device 81 of a present Example is not restricted to 9 phases. For example, the power converter outputs three-phase alternating current, and includes nine power modules U1 to W3 obtained by multiplying the number of phases 3 by, for example, a predetermined integer 3, and these power modules U1 to W3 are the same number 3 as the predetermined integer 3. Group into groups. That is, the U1-W1 group, the U2-W2 group, and the U3-W3 group are grouped. And you may arrange | position the power module put together into 1 group, 2 groups, and 3 groups in the circumferential direction as shown in FIG. The multiphase AC motor to which the power converter 81 is attached includes the same number of motor coils as the power modules U <b> 1 to W <b> 3, and both are electrically connected by an AC terminal 86.

  According to such a configuration, the impedance between the motor coil and the power module can be minimized. Further, it is possible to balance the internal impedance of the motor-electric integrated motor. As a result, the load on the capacitor 83 can be further reduced and the variation can be eliminated to reduce the size of the capacitor 83.

  Similarly, in the power converter illustrated in FIGS. 12 and 13, the power converter can be applied as a power converter that outputs multiphase alternating current such as three-phase or six-phase by appropriately selecting the number of power modules.

  By the way, in the above-described power converters 1, 21, 31, 41, 51, 61, 71, 81 of the present embodiment, the U phase that is one of the plurality of phases will be described as a representative. The impedance of the power module inter-phase current path that electrically connects the terminal of the module 2 and the terminals of the power modules 3 and 4 in the other V and W phases is within the one phase. Since it is configured to be smaller than the impedance of the in-phase current path that electrically connects the terminals, it is possible to increase the cancellation of the ripple current between the phases and to reduce the ripple current flowing through the capacitor. Therefore, it is possible to reduce the size of the capacitor, and thus it is possible to reduce the size of the power converter. In addition, it is not necessary to increase the distance between the power module and the capacitor in each phase, and an increase in surge current to the power module can be avoided.

  Further, in the power converters 1, 21, 31, 41, 51, 61, 71, 81, the impedance of the current path between the power modules is such that the impedance of the current path in one phase and the inside of the capacitor in one phase. By configuring the impedance to be smaller than the total impedance with the impedance, it is possible to further enjoy the effect that the above-described capacitor can be reduced in size.

  Moreover, in the power converters 41, 61, 71, 81, since the impedance of the in-phase current path in each phase is configured to be the same in all phases, the surge voltage of each power module 2, 3, 4 is made equal. And enables stable power conversion.

  Moreover, in the power converters 21, 41, 61, 71, 81, since the impedance of the current path between the power modules is configured to be the same for all phases, the ripple current cancellation is prevented from fluctuating, Enables stable power conversion.

  Further, in the power conversion devices 21, 41, 61, 71, 81, as shown in FIGS. 5, 7, 10, and 11, a plurality of power modules 2, 3, and 4 are arranged in the circumferential direction. That is, these 2, 3, and 4 are arranged on a common virtual circle. Then, a P · N terminal is provided at a portion of the power module 2, 3, 4 on the inner side of the virtual circle inner diameter. Thereby, the distance between the terminals of the power modules 2, 3, 4 and the distance of the power modules 2, 4 can be shortened to obtain the above-described function of reducing the impedance of the current path between the power modules. .

  Further, in the power converters 21, 41, 61, 71, 81, both the P and N terminals are provided on the inner diameter side end of the virtual circle representing the arrangement of the power modules. Thereby, the distance between the terminals of the power modules 2, 3, 4 can be further shortened.

  In the power conversion device 1 and the like, since all of the positive terminals or the negative terminals of the power modules 2, 3, 4 are arranged on a common virtual circle, the power modules 2, 3, 4 are arranged. The distance between the terminals can be shortened, and the impedance of the current path between the power modules can be reduced.

  Further, by arranging all of one of the positive electrode terminal and the negative electrode terminal on the virtual circle at equal intervals in the circumferential direction in the power conversion device 1 or the like, the impedance of the power module inter-phase current path in each phase can be set to all phases. Can be approximately equal.

Further, in the power conversion devices 21, 31 and the like, the terminals arranged on the virtual circle are connected to the module 2,
Since the other end of the module body is disposed outside the virtual circle, the terminal distance between the power modules 2, 3 and 4 can be further shortened.

  Further, in the power conversion device 31, the power module is arranged in such a posture that a virtual line connecting the positive electrode terminal and the negative electrode terminal in one power module is perpendicular to the virtual circle. The terminal distance between 2, 3, 4 can be further shortened.

  In the power conversion device 61 and the like, since all of the positive terminal and the negative terminal of the power module are arranged on the common virtual circle B at equal intervals in the circumferential direction, the impedance of the current path between the power modules is set to all phases. And the design of the electric circuit including the power converter becomes easy.

In the power converters 41, 51, 61, 71, the distance between the terminals of the power modules 2, 3, 4 is shorter than the distance from the power module terminal to the capacitor terminal electrically connected to the terminal. In the power converter 81, the distance between the terminals of the power modules U1 to W3 is shorter than the distance from the power module terminal to the terminal of the capacitor 83 that is substantially equal to the length of the tongue piece 8T.
Thereby, the impedance of the power module inter-phase current path can be made smaller than the impedance of the intra-phase current path.

  Further, in the power conversion device 61 and the like, all of the positive terminals and the negative terminals of the capacitors 5, 6, and 7 are arranged on the common virtual circle B at equal intervals in the circumferential direction, and the virtual circle B and the virtual circle A are concentric. Therefore, the ripple current can be evenly distributed to the capacitors 5, 6, and 7.

In the power converter 61 and the like, since the diameter of the virtual circle A is smaller than half of the diameter of the virtual circle B (more precisely, the distance between the virtual circle A and the virtual circle B), The impedance can be made smaller than the impedance of the in-phase current path.

  Further, in the electromechanical integrated motor provided with the power conversion device 81, the power conversion device 81 is an annular body centering on the motor rotation shaft as shown in FIG. 13, and a plurality of power modules U1 are arranged in the circumferential direction of the annular body. ~ W3 is arranged. Thereby, in the case of a 9-phase multi-phase AC power converter, the impedance of the interphase current path can be significantly reduced as compared with the 3-phase AC power converter. Further, the rotor rotation shaft can be passed through the hole 85 of the power conversion device 81, which is suitable for an electromechanically integrated motor.

Further, in the electromechanical integrated motor including the power conversion device 81, the power conversion device 81 includes nine power modules obtained by multiplying the number of phases of the multiphase alternating current (for example, three phases) by a predetermined integer (for example, 3). Nine power modules may be grouped into three sets equal to the predetermined integer 3. In other words, the power conversion device 81 is a three-phase AC power conversion device in which U1 to U3 groups, V1 to V3 groups, W1 to W3 groups, and power modules U1 to W3 arranged for each group are arranged in the circumferential direction. It may be.
Thereby, the impedance of the current path between phases can be defined by the distance for three phases. That is, when the power modules U1, V1, W1, U2, V2, W2, U3, V3, and W3 are arranged in the clockwise direction when viewed from the axial direction, the phase between U1-V1, the phase between V1-W1, and the phase between W1-U1. It is possible to cancel ripple current. Moreover, ripple current cancellation of W1-U1 (the farthest relationship) is actually possible between the phases W1-U2 and U1-W3, so the interphase distance can be defined only between adjacent power modules. . Therefore, the impedance of the interphase current path can be remarkably reduced as compared with a three-phase AC power conversion device including three power modules.
Further, in the case of a polyphase AC motor having nine motor coils, the AC terminals 86 of the power modules U1 to W3 can be directly connected to the motor coils, so that the impedance between the motor coils and the power modules can be reduced. Can be minimized.

  Further, in the electromechanical integrated motor including the power conversion device 81, as shown in FIG. 13, a plurality of power modules U1 to W3 and a bus bar 8 serving as an interphase current path are arranged on one surface of the plate-like substrate 84. 12, since a plurality of capacitors 83 are arranged on the other surface, extending the tongue piece 8T from the bus bar 8 toward the capacitor 83 reduces the impedance of the interphase current path, The impedance of the current path can be increased.

  In addition, in the electro-mechanical integrated motor including the power conversion device 81, the power modules U1 to W3 are replaced with the bus bar 8 serving as the in-phase current path, separately from the bus bar 8 serving as the inter-phase current path, instead of the tongue piece 8T. Further, it may be installed between the capacitors 83. As a result, it is possible to eliminate variations in loads and lifetimes of the plurality of capacitors 83.

  In the electromechanical integrated motor including the power conversion device 81, a passage through which the refrigerant flows is formed in the plate substrate 84, and the refrigerant flows from the inlet 84I to the outlet 84O of the passage. The power modules U1 to W3 and the capacitor 83 respectively arranged on both surfaces can be efficiently cooled, and the cooling efficiency is improved.

  The above description is merely an example of the present invention, and the present invention can be variously modified without departing from the spirit of the present invention. The present invention is not limited to the above-described three-phase alternating current embodiment, and can be applied to embodiments including a plurality of phases such as six phases and nine phases. Since the power conversion device of the present invention is an electromechanically integrated motor, the power modules 2, 3, 4 and the coil 104 are arranged close to each other, that is, the power modules 2, 3, 4 and the coil 104 are low impedance. So that the surge voltage can be reduced. The application of the power conversion device of the present invention is not limited to the electromechanical integrated type.

It is a longitudinal cross-sectional view of the electromechanical integrated motor provided with the power converter device which becomes one Example of this invention. It is explanatory drawing which shows schematic structure about the power converter device of the Example. It is explanatory drawing which shows typically the relationship between a ripple current and a surge current. It is explanatory drawing which shows typically the relationship between a ripple current and a surge current. It is explanatory drawing which shows schematic structure about the power converter device which becomes the 2nd Example of this invention. It is explanatory drawing which shows schematic structure about the power converter device which becomes the 3rd Example of this invention. It is explanatory drawing which shows schematic structure about the power converter device which becomes the 4th Example of this invention, (a) is the top view, (b) is the side view. It is a side view which expands and shows the attachment location of the bus bar and a terminal in the Example. It is explanatory drawing which shows schematic structure about the power converter device which becomes 5th Example of this invention, (a) is the top view, (b) is the side view. It is explanatory drawing which shows schematic structure about the power converter device which becomes the 6th Example of this invention, (a) is the top view, (b) is the side view. It is explanatory drawing which shows schematic structure about the power converter device which becomes the 7th Example of this invention. It is a perspective view which shows the state which looked at the substance structure of the power converter device which becomes the 8th Example of this invention from one side. It is a perspective view which shows the state which looked at the power converter device which becomes the Example from the other.

Explanation of symbols

1, 21, 31, 41, 51, 61, 71, 81 Power converter 2 U-phase power module 3 V-phase power module 4 W-phase power module 5 U-phase capacitor 6 V-phase capacitor 7 W-phase capacitor 8 Bus bar 12 Multiphase AC motor

Claims (21)

In a power converter that converts a direct current into a multiphase alternating current and supplies it to a multiphase alternating current motor,
A plurality of power modules that convert a direct current input from the direct current terminal into a polyphase alternating current and output to the alternating current terminal; and
Capacitors placed close to each power module,
A bus bar that electrically connects each phase power module and a plurality of capacitors so that the impedance between the power module in one phase and the power module in the other phase is smaller than the impedance between the power module and the capacitor. A power conversion device comprising:   2. The power converter according to claim 1, wherein the power module and the capacitor are connected so that the impedance between the power module and the capacitor in one phase is the same as the impedance between the power module and the capacitor in the other phase. . To make the impedance of power modules the same,
The power conversion apparatus according to claim 1, wherein the power modules are arranged at equal distances on a virtual circle.   The power converter according to claim 3, wherein the power module is provided with a DC terminal on an inner diameter side of the virtual circle. The power module includes a positive terminal of a direct current terminal, a negative terminal of a direct current terminal,
The power converter according to claim 4, wherein both the positive terminal and the negative terminal of the DC terminal are disposed on the inner diameter side of the virtual circle. The power module is
6. The power converter according to claim 5, wherein at least one of the positive terminal and the negative terminal of the DC terminal is arranged on a common virtual circle. The power module is
The power converter according to claim 6, wherein both of the positive terminal and the negative terminal of the DC terminal are arranged on a first virtual circle that is common.   The power converter according to claim 7, wherein the power module is arranged such that a virtual line connecting a positive terminal and a negative terminal of the DC terminal is perpendicular to a plane including the virtual circle. The capacitor includes a positive terminal and a negative terminal,
The power converter according to any one of claims 5 to 7, wherein both the positive terminal and the negative terminal are arranged on a common second virtual circle.   The power converter according to claim 9, wherein a plurality of capacitors are arranged on the second virtual circle at equal intervals in the circumferential direction.   The capacitor is on a second virtual circle such that the second virtual circle is concentric with the first virtual circle, and the radius of the second virtual circle is doubled relative to the first virtual circle. The power conversion device according to claim 9 or 10, wherein the power conversion device is arranged. The power converter has an annular plate,
The power module is disposed on one surface of the annular plate;
The power converter according to claim 1, wherein the capacitor is disposed on the other surface of the annular plate. The plurality of power modules are arranged radially on one surface of the annular plate with the DC terminals directed toward the center of the annular plate,
13. The power conversion device according to claim 12, wherein the plurality of capacitors are arranged radially on the other surface of the annular plate with direct-current terminals directed toward the center of the annular plate.   The power converter according to claim 13, wherein the bus bar is a ring-shaped bus bar that connects DC terminals of a plurality of power modules.   15. The power conversion according to claim 14, wherein the bus bar includes a plurality of tabs extending from the vicinity of the DC terminals of the plurality of power modules to the other surface of the annular plate, and the capacitor DC terminals are connected to the tabs. apparatus.   The power converter according to any one of claims 12 to 15, wherein the annular plate includes a passage through which the refrigerant passes. The impedance between the power module and the capacitor is
The power converter according to any one of claims 1 to 16, wherein the power converter is a sum of a current path between the power module and the capacitor and an internal impedance inside the capacitor. In a motor drive system consisting of a power converter for converting DC current into multiphase AC current and a multiphase AC motor,
A cylindrical motor housing, a plurality of stators arranged along the inner periphery of the cylindrical motor housing, a stator having coils, a rotor rotatably supported by the motor housing, and power conversion disposed at one end of the motor housing Having a device,
The power converter includes a plurality of power modules that convert a direct current input from a direct current terminal into a multiphase alternating current and output to the alternating current terminal, a capacitor that is disposed close to each power module, and a single phase. A bus bar that electrically connects each phase power module and a plurality of capacitors so that an impedance between the power module and a power module in another phase is smaller than an impedance between the power module and the capacitor. A motor drive system characterized by   19. The motor according to claim 18, wherein the power converter has an annular plate, the power module is disposed on one surface of the annular plate, and the capacitor is disposed on the other surface of the annular plate. Driving system.   The power converter according to claim 19, wherein the annular plate has a motor rotation shaft.   The stator includes a number of power modules obtained by multiplying the number of phases of polyphase alternating current by a predetermined integer, and the power modules are equal in number to the stators, and the capacitors are equal in number to the power modules. The power converter according to any one of claims 18 to 20.

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