JPS6091867A - Inverter - Google Patents

Abstract

PURPOSE:To prevent the variation in the current balance by folding a bus bar in a U-shape, and connecting power module group at one of the folded piece in parallel. CONSTITUTION:Bus bars 11a, 11b are folded in a U-shape. Power modules 2a, 2b and 2c are connected in parallel on the lower surfaces of one folding piece 12 of the bars 11a, 11b and the lower surface of the bar 11c. A printed board 14 is disposed on the upper surface side of the other folding piece 12 of the bars 11a, 11b and the upper surface side of the bus bar 11c. Further, the board 14 is secured to the modules 2a, 2b, 2c together with the bars 11a, 11b and 11c. Thus, the effect of stabilizing the current balance can be obtained by folding the bus bars.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an inverter that uses semiconductor elements to obtain an AC output, and particularly relates to an inverter assembly structure.

(Background of the Invention) FIG. 1 shows an example of the assembly structure of a conventional three-phase inverter, and mainly shows the assembly structure for one phase to simplify the explanation. (shown in the same figure), this inverter is
Three strip-shaped busbars 1a.

1bI3 and 1C, three power modules 2a, 2b and 2c connected in parallel with each bus bar 1a, 1b+jj and 1C, and each power module 2a, 2
b and 2o, and each phase of the AC output is taken out by a lead wire 4 (the other two are not shown).

Bus bars 1a, 1b and 1G are each provided with three large diameter holes 5 and three small diameter holes 6. Large diameter hole 5
are holes for screwing to the power modules 2a, 2b, and 2C, and small diameter holes are holes for screwing and fixing each lead wire of the snubber circuit 3.

The power modules 2a, 2b113, and 2o have guide grooves formed on the upper surface of the main body into which the bus bars 1a, 1b, and 1c are respectively fitted, and the terminal plates A,
Where B and C are respectively provided, a step G is provided with a screw hole for a screw inserted through the large diameter hole 5. In the illustrated example, the bus bar 18 and the lead wire 4 are tightened and fixed to the terminal plate A of the power module 2a with screws 7.

As shown in FIG. 2, each power module 2a,
2b and 2c are two power transistors Q connected in series.1. ．． 0.2, each terminal A.

B and C are connected to the terminal plates Δ, B and C, respectively. Note that a heat sink (not shown) is attached to the lower surface of the main body, and holes 8 for this purpose are provided at the four corners.

The snubber circuit 3 includes two snubber circuits 3a having the same circuit configuration.
and 3b are connected in series, and three lead terminals A-,
B' and C- are screwed into the small diameter holes 6 of the bus bars 18.1b# and 1G, respectively. That is, in the illustrated example, the lead terminals Δ-, B-, and C- are connected to the bus bar 18.
, 1b and 1C to the terminal plate A of the power module 2a.

B and C, respectively. Note that the snubber circuits 3 installed in the other power modules 2b and 2c (tI) have the same configuration, so a description thereof will be omitted.

The snubber circuit 3a or 3b, as shown in FIG.
This circuit consists of a resistor and a diode connected in parallel, and a capacitor connected in series.Both ends of the resistor and diode are connected to the emitter and collector of the transistor Q, and the circuit absorbs the surge voltage of Vcε. Therefore, in the snubber circuit 3, snubber circuits 3a and 3b having the same circuit configuration are connected in series to form one set.

The lead wire 4 is connected to the bus bar 1a and hence to the power module 2.
When fastening to a with the screw 7, the tip thereof is folded back into a U-shape and connected. This means that the current balance of power modules 2a, 2b and 2C connected in parallel is
This is to prevent collapse due to the wiring inductance of No. 4.

However, such a conventional inverter assembly structure has the following problems. First, the current balance is improved by connecting the lead wires back, but when this type of inverter is used in mobile equipment such as automobiles where vibration is unavoidable, the inductance of the folded portion due to vibration is As a result of fluctuations in
Difficult to maintain current balance.

In addition, the folding of the lead wire is performed in a plane perpendicular to the busbar, but this causes the distance between the lead wire and the bus bar to be large, and the distances of the three lead wires to be uneven, resulting in a current balance ratio. Not only does this worsen, but the vertical space also increases.

Further, since the snubber circuit is arranged in a plane for each power module, the space in the left and right direction increases.

Furthermore, since the snubber circuit is connected to the transistor of the power module via the bus bar, the connection path becomes long and the surge absorption efficiency is poor.

Finally, it is necessary to perform maintenance on a component-by-part basis, and it is very troublesome to locate and replace failed parts.

(Objective of the Invention) This invention has been made in view of the above circumstances, and its purpose is to provide a compact inverter that allows a snubber circuit to function effectively and prevents fluctuations in current balance. It is in.

(Structure of the Invention) In order to achieve the above object, the present invention provides a bus bar that is folded back in a U-shape and has an insulating spacer sandwiched between both folded pieces, and a bus bar that is connected in parallel with one folded piece of the bus bar. a printed circuit board disposed on the other folded side of the bus bar and on which a predetermined number of snubber circuits are mounted, and the predetermined number of snubber circuits and the power module group are connected to each other via the bus bar. It is characterized by a conductive screw fastening connection.

(Description of Embodiment) FIG. 4 is an exploded perspective view showing an embodiment of the inverter according to the present invention, and similarly to FIG. 1, one phase is shown.

J3 in the same figure, this inverter includes busbars 11a and 11b folded back into a U-shape and a plate-shaped busbar 11.
0, the aforementioned power modules 2a, 2bllI3 and 2 which are connected in parallel by the lower surface of the folded piece 12 of one of the busbars 11a, 11b and the lower surface of the busbar 11c.
C. It is composed of a printed circuit board 14 disposed on the upper surface side of the other folded piece 13 of the bus bar 11811b and on the upper surface side of the bus bar 110.

The reason why the bus bar 11c is not formed in a folded manner is as follows. In this embodiment, power modules 2a, 2
The connection form of the two power transistors b and 2c is as shown in FIG. 2, with the terminal plate C serving as the collector line. This is because it is known that the folding effect of the bus bar does not affect the current balance regarding this collector line.

The other folded piece 13 of the bus bars 11a, 11b and the bus bar 11C are provided with a hole 14 for connecting a lead wire (not shown) and a hole 16 into which a conductive screw 15 is inserted. And bus bar 11a,
An insulating spacer 17 is sandwiched between both broken ice pieces 12 and 13 of 11b.

In this embodiment, the insulating spacer 17 is formed into a hollow cylindrical shape, and is arranged coaxially with the hole 16 and is inserted through the conductive screw 15. etc., to prevent it from falling off.

The printed circuit board 14 has the above-mentioned snubber circuit 3a on the top surface.
A predetermined number of (3b) (one of which is shown) is formed, and the portions corresponding to the lead terminals /M, B' and C' are patterned as shown by diagonal lines. A hole 19 is provided in the pattern area 18 .

A conductive screw 15 is inserted through the hole 19 and connected to the collector and emitter of the power transistors of power modules 2a, 2b# and 2C. In addition,
The pattern region 118 has a relatively large area and has a function of efficiently dissipating heat generated by the resistance of the snubber circuit. In order to prevent the screws 15 from coming into contact with the holes 16 when the printed circuit board 14 is fixed to the power modules 2a, 2b, and 2C together with the busbars 11a, 11b, and 110 using the screws 15, the insulating members 20.2
18 and 23 are provided.

The insulating member 20 is made of, for example, a hive tube, and has a screw 1.
5 and is inserted into the hole 16.

Among the insulating members 21 and 23, the insulating material 21 is connected to the busbars 118 and 11 by nuts etc. that protrude from the lower surface of the printed circuit board 14.
It is the /jth thing that should not come into contact with b, and is not necessary if there is no protruding object such as a corner 1- on the bottom surface of the printed circuit board. Further, since the bus bar 110 is not formed by folding back, the insulating member 23 is used to adjust the height accordingly, thereby preventing unnecessary distortion from occurring in the printed circuit board 14.

J3, power modules 2a, 21) There are screws 24 on the bottom of the main body of J7 and 2C, as in the case shown in Figure 1.
With this, a heat sink (not shown) is fixed.

(Effects of the Invention) As explained in detail above, in the inverter according to the present invention, the bus bar is folded into a U-shape, a power module group is connected in parallel with one of the folded pieces, and the power module group is connected in parallel with the other folded piece. A board on which the snubber circuit is mounted is arranged, and the snubber circuit and the power module group are fastened and connected via a bus bar using conductive screws, and a predetermined distance is reliably maintained between both folded pieces of the bus bar with an insulating spacer. Ru. - Therefore, the following excellent effects can be obtained. First, the current balance is obtained by folding the busbar, and the inductance is prevented from changing due to vibration by the insulating spacer, so that a stable current balance can be obtained.

Furthermore, since the broken ice pieces on both sides of the bus bar are spaced relatively narrowly and are uniform in three phases, the current balance rate is improved.

Furthermore, since a predetermined number of snubber circuits are mounted on printed circuit boards and connected directly to the power module group using conductive screws, the connection distance is extremely short, and the function of the snubber circuit is effectively demonstrated.

Finally, as a result of mounting the snubber circuit on the printed circuit board, the power module groups can be spaced closer together, thereby reducing lateral space. moreover,
Since there is no lead line as in the conventional case, the space in the vertical direction can be reduced, and the inverter can be made compact. Furthermore, since maintenance can be performed on a board-by-board basis, work efficiency is further improved.

[Brief explanation of the drawing]

Figure 1 is an exploded perspective view of a conventional three-phase inverter;
The figure is a schematic circuit diagram showing the connection form of power transistors included in each power module, Figure 3 is a schematic circuit diagram showing the connection form of a snubber circuit, and Figure 4 is an exploded view showing an inverter according to an embodiment of the present invention. FIG. 2a, 21+ and 2C...power module 3a (
3b)・・・・・・・・・・・・・・・・・・・・・
...Snubber circuits 11a, 11b and 11c-7st
＜ -12,13・・・・・・・・・・・・・・・
......Folding piece 14...
・・・・・・・・・・・・・・・・・・・・・・・・
・Printed circuit board 15・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・Conductive spacer 17・・・・・・・・・・・・・・・・・・Insulating spacer 18...・・・・・・・・・・・・・・・Patterns A, B and C・・・Terminal board patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] (1) A bus bar that is folded back in a U-shape and has an insulating spacer sandwiched between both folded pieces, a power module aY that is connected in parallel with one folded piece of the bus bar, and the other folded side of the bus bar. and a printed circuit board on which a predetermined number of snubber circuits are mounted, and the predetermined number of snubber circuits and the power module group are fastened and connected by conductive screws via the bus bar. Features of the inverter.