JPH08149795A - Semiconductor power converter - Google Patents

Abstract

PURPOSE: To reduce the stray inductance of a main circuit conductor and to suppress surge voltage caused by the action of a switching element in an inverter and the stray inductance of main circuit conductor. CONSTITUTION: The power converter comprises a smoothing circuit section for converting AC power from an AC power supply through a converter into DC power having significant pulsation and converting the pulsating DC power through a smoothing capacitor 2 into DC power, and an inverter comprising a plurality of semiconductor switch elements 21-26 for converting the smoothed DC power into AC power, wherein the smoothing circuit section is connected electrically with the plurality of semiconductor switch elements 21-26. The power converter further comprises a main circuit conductor wherein waving main circuit conductors on the positive and negative electrode sides are arranged substantially in parallel through a predetermined insulation gap and integrated by means of an insulation coating material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter using a power semiconductor element for high-power and high-speed switching, and more particularly to a semiconductor power converter for reducing stray inductance of a main circuit conductor.

[0002]

2. Description of the Related Art Due to the social need for energy saving, power semiconductor elements tend to have large capacity, low loss, and high speed, and high-performance and highly-efficient power conversion has become possible. On the other hand, to realize a high-speed switching frequency and a high-efficiency power conversion device using a high-speed switching element, the main circuit inductance and the fast current change rate (di / d)
It is necessary to take measures to protect the power conversion device from an excessive surge voltage generated by t).

A small capacity converter does not pose a problem because of its low current density, but a large capacity converter requires the reduction of the stray inductance of the main circuit. Generally, the following measures are taken in consideration of a method of suppressing surge overvoltage with a voltage-type converter, or the fact that a current having a higher rate of change is concentrated and flows on the conductor surface.

1) Minimize the main circuit wiring length. 2) Use a wiring structure (or a close contact bus) that cancels the change in magnetic flux. 3) Increase the surface area of the bus to avoid current concentration due to the skin effect.

4) Reduce di / dt. 5) Absorb in the snubber circuit. Originally, a high-speed switching element has a large di / dt, and the countermeasure item 4) above is not appropriate against the original purpose of use of the element, and the countermeasure 5) causes the loss in the snubber circuit to increase It is not a good idea because it causes a drop in efficiency. However, the problems 4) and 5) are inevitably solved if the measures 1) and 2) can be realized.

Here, the principle of generation of surge overvoltage due to the stray inductance of the power supply conductors (positive side power supply conductor, negative side power supply conductor) in the conventional voltage type converter will be described with reference to FIGS. FIG. 12 shows the main circuit configuration of only one phase of the upper and lower arms of the conventional voltage type converter (the voltage type converter of FIG. 15). In FIG. 12, 1 is a DC input power source, 2 is a smoothing capacitor, 3 is a smoothing capacitor 2, and a positive side main circuit conductor (positive side power supply conductor) up to the switch element Q1 of the upper arm 5 is a smoothing line. Capacitor 2 and the switch element Q2 of the lower arm 6 to the negative side main circuit conductor (negative side power supply conductor), 5 is the upper arm having the positive side switch element Q1 and the diode D1, 6 is the negative side switch element Q2 and the diode D2 And a lower arm 7 having an AC output terminal derived from a connection point between the upper arm 5 and the lower arm 6. Lsa is the stray inductance of the positive side main circuit conductor 3, and Lsb is the stray inductance of the negative side main circuit conductor 4.

In FIG. 12, surge overvoltage occurs at the following times. That is, the current ID of the inductive load (not shown) connected to the AC output terminal 7 [FIG.
(B)] is flowing in the diode D1 of the upper arm 5, when Q2 is turned on, Ic (collector current) of Q2 increases at the rise of dic / dt [Fig.
(B)], the current exceeds the load current. This excess current is the recovery current of the diode D1 of the upper arm 5, and it rapidly decreases after the recovery current reaches its peak. With the recovery current at this time, the surge overvoltage VON of the formula (1) is generated when Q1 is turned on [Fig. 13 (c)].

VON = −L · dir / dt (1) where ir: recovery current of diode D1 L: main circuit stray inductance (Lsa + Lsb) Further, when Q2 is turned off, dic / dt [FIG. 14]
In (a)], the surge overvoltage VOFF of the formula (2) is generated [Fig. 14 (b)].

VOFF = −L · dic / dt (2) However, ic: collector current L: main circuit stray inductance (Lsa + Lsb) From equations (1) and (2), it is generated when Q2 is turned on and Q2 is turned off. Which surge overvoltage VON, VOFF
Also, the stray inductances Lsa and Lsb of the main circuit are involved,
It can be seen that the main circuit conductors 3 and 4 from the smoothing capacitor 2 to the switch elements Q1 and Q2 need to be minimized.

FIGS. 15 to 19 are diagrams for explaining the configuration of the main circuit conductors 3 and 4 included in the conventional power converter. FIG. 15 is a reverse diagram in which an IGBT (insulated gate bipolar transistor) is used as a switch element. It is a main circuit connection diagram of a converter. 16 to 17 are views for explaining the main circuit conductors 3 and 4 of the first conventional power conversion device.
6 is a plan view of the inverse converter and the main circuit conductors 3 and 4 of FIG. 15, and FIG. 17 is a side view as seen in the direction of arrow XX in FIG.

The positive-side main circuit conductor 3 is an L-shaped conductor in cross section, and is placed on one terminal of the smoothing capacitor 2 and the collector terminals of the switch elements 8, 9 and 10, and this is fixed by a fixing screw 13. , 14 are closely connected. Similarly, the negative-side main circuit conductor 4 is an L-shaped conductor in cross section, and is connected to the other terminal of the smoothing capacitor 2 and the switch elements 15 and 1.
It is placed on top of collector terminals 6 and 17, and these are tightly connected by fixing screws 18 and 19. In the figure, 1
Reference numeral 1 is an AC output terminal, and 12 is a cooler.

This is an example in which the surface areas of the positive electrode side main circuit conductor 3 and the negative electrode side main circuit conductor 4 connected to each terminal (each electrode) portion are increased by the above configuration. FIG. 18 shows a conventional second
Smoothing capacitor 2 and switch element 8 of the power converter of
20 is a plan view of a structural example in which the main circuit conductors 3 and 4 of each electrode between 10 and 10 are configured by plate-shaped conductors having a large surface area, and FIG. 19 is a side view of FIG. 18 viewed in the direction of arrow XX. . Reference numeral 11 is an AC output terminal, and 12 is a cooler.

In all of the converter structures shown in FIGS. 16 to 19, the magnetic fluxes of the generated magnetic fields, which are generated by the currents flowing in opposite directions to each other and which are arranged in close contact with each other, are canceled, the conductor impedance is lowered, and the surge overvoltage is reduced. It was intended to be suppressed.

The relationship between the arrangement of conductors and the inductance is described in the POWER CONVERSION / JUNE1991 PROCEEDINGS section above.
No. p143. According to this, when the two conductors are arranged in parallel with each other, the theoretical limit inductance can be made zero when the installation interval of both conductors is a and the conductor width is b (a / b = 0).

However, in reality, it is impossible to set a / b = 0, and a surge overvoltage occurs, and although not shown in the main circuit connection diagram of FIG. 15, in order to protect the switch element from the surge overvoltage, , The switch elements 8, 9 and 10 and the main circuit conductors 3 and 4 are in contact with each other, and a DC snubber is attached between the collector and the emitter of each switch element.

Generally, in a large power converter, the shape of the switch element inevitably lengthens the main circuit conductor and increases the inductance. If switching is performed with a switch element having a high di / dt, a large surge overvoltage occurs and the switch It is absorbed using a DC snubber circuit or a separate snubber within a range that falls within the safe operation area of the device. This absorbed energy is extremely large and is radiated as heat in the present devices. Also, of course, the snubber structure becomes large due to the large amount of energy. Since the heat generated in the snubber circuit is processed in the form of mere release of heat, it causes a decrease in inverter efficiency.

In order to increase snubber loss caused by the main circuit conductors 3 and 4, suppress surge overvoltage and improve converter efficiency or device reliability, a reliable low inductance of the main circuit conductor is required. Need to be converted.

[0018]

As described above, in the circuit where stray inductance exists in the main circuit conductors 3 and 4, d
When switching with a switching element with high i / dt,
During turn-on and turn-off of the device, the stray inductance of the main circuit is steep during the recovery time of the flywheel diode built in the device or attached, and an extremely large surge overvoltage occurs.

It is naturally difficult to reduce such a steep overvoltage by reducing the stray inductance with a simple flat conductor arrangement structure. The present invention has been made on the basis of the above points, and has a relatively simple structure, reduces the inductance of the main circuit conductor, and suppresses surge overvoltage caused by high di / dt of the switching element and stray inductance of the main circuit conductor. An object of the present invention is to provide a high-efficiency and high-performance semiconductor power conversion device that suppresses the generation of the snubber loss and realizes the reduction of the snubber loss and the miniaturization.

[0020]

In order to achieve the above object, the invention according to claim 1 converts the AC power of an AC power supply into a DC power with large pulsation by a forward converter, and converts the converted pulsation. A smoothing circuit unit that converts a large DC power into a smaller DC in a smoothing circuit unit configured by a capacitor, and a DC power with small pulsation obtained by the smoothing circuit,
In a power conversion device for converting into AC power by an inverse converter composed of a plurality of semiconductor switching elements, the smoothing circuit section and the semiconductor switching elements of the inverse converter are electrically connected, each of which: A main circuit conductor formed by correlating the positive electrode side main circuit conductor and the negative electrode side main circuit conductor, which are formed in a corrugated shape and are arranged substantially parallel to each other so as to maintain a predetermined insulation distance from each other, by an insulating coating material. It is a semiconductor power converter.

In order to achieve the above object, the invention according to claim 2 is the semiconductor power conversion device according to claim 1, wherein the main circuit conductor is substantially the same as the outer surface of the inverse converter to which the main circuit conductor is attached. It is a semiconductor power conversion device characterized by having dimensions.

In order to achieve the above-mentioned object, the invention according to claim 3 converts the AC power of the AC power supply into DC power with large pulsation by a forward converter, and converts the converted DC power with large pulsation into a capacitor or the like. The smoothing circuit unit configured to convert into a smaller direct current, and the DC power with small pulsation obtained by the smoothing circuit is converted into AC power by an inverse converter composed of a plurality of semiconductor switch elements. In the power conversion device, the smoothing circuit section and the semiconductor switching element of the inverse converter are electrically connected, each having a plurality of semicircular cross-section projections, and both A semiconductor power converter including a main circuit conductor formed by integrating a positive side main circuit conductor and a negative side main circuit conductor, which are arranged substantially parallel to each other so as to maintain a predetermined insulation distance, by an insulating coating material. It is a device.

In order to achieve the above object, the invention according to claim 4 is to convert the AC power of the AC power supply into DC power with large pulsation by a forward converter, and convert the converted DC power with large pulsation into a capacitor or the like. The smoothing circuit unit configured to convert into a smaller direct current, and the DC power with small pulsation obtained by the smoothing circuit is converted into AC power by an inverse converter composed of a plurality of semiconductor switch elements. In the power converter, the smoothing circuit section and the semiconductor switch element of the inverse converter are electrically connected, each main circuit conductor piece having a plurality of corrugated conductive plates coated with an insulating coating material. A semiconductor power conversion device comprising a main circuit conductor in which a positive side main circuit conductor and a negative side main circuit conductor formed by stacking are laminated substantially parallel to each other.

[0024]

According to the invention according to claim 1 or 2, the smoothing circuit portion and the semiconductor switch element of the inverse converter are electrically connected, and each is formed in a wave shape. Moreover, since the main circuit conductor is formed by integrating the positive side main circuit conductor and the negative side main circuit conductor, which are arranged substantially parallel to each other so as to maintain a predetermined insulation distance from each other, with an insulating coating material, Various operational effects can be obtained. That is, since magnetic fluxes generated by currents flowing in different directions in the positive-side main circuit conductor and the negative-side main circuit conductor cancel each other out, stray inductance of the positive-side main circuit conductor and the negative-side main circuit conductor is reduced. In addition, by substantially increasing the width of the conductor with respect to the conductor installation interval with the corrugated conductor, the switching operation of the inverse converter composed of the switch element and the positive side main circuit conductor and the negative side main circuit conductor Surge overvoltage caused by stray inductance can be suppressed.

According to the invention corresponding to claim 3, the smoothing circuit portion and the semiconductor switch element of the inverse converter are electrically connected to each other, and each of the plurality of protrusions has a semicircular cross section. And a main circuit conductor formed by integrating a positive-side main circuit conductor and a negative-side main circuit conductor, which are arranged substantially parallel to each other so as to maintain a predetermined insulation distance from each other, by an insulating coating material. The same effects as those of claim 1 or claim 2 can be obtained.

According to a fourth aspect of the present invention, the smoothing circuit portion and the semiconductor switch element of the inverse converter are electrically connected to each other, and each of the plurality of corrugated conductive plates is provided with an insulating coating. Since the positive-side main circuit conductor and the negative-side main circuit conductor, which are formed by laminating the main circuit conductor pieces coated with a material, are provided substantially parallel to each other, the stray inductance of the main circuit conductor and The so-called skin effect in which the current is concentrated on the surface of the main circuit conductor by the high-frequency current due to the fast switching operation of the switch element can prevent the increase of the conductor resistance and also reduce the inductance.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. Here, an inverter will be described as an example of the semiconductor power conversion device, but the present invention is not limited to this. (First Embodiment) FIGS. 1 to 4 are views for explaining a first embodiment of the present invention. FIG. 1 is a plan view of a semiconductor power converter, and FIG. FIG. 3 is a side view seen in the direction of the arrow, FIG. 3 is a plan view showing the main circuit conductor of FIG. 1, and FIG. 4 is a side view seen in the direction of the arrow YY of FIG. 12 to 19 shown in the prior art in FIGS. 1 to 4.
The same elements as are indicated by the same symbols.

In this embodiment, in the circuit shown in FIG.
The positive-side main circuit conductor 3 and the negative-side main circuit conductor 4 that electrically connect between the smoothing capacitor 2 and the semiconductor switch elements 8 to 10 and 16 to 18 forming the inverse converter are connected as follows. The circuit conductor 30 is configured. That is, the main circuit conductor 30 is a positive electrode side main circuit conductor 34 in which two strip-shaped conductors are formed in a corrugated shape (bellows shape) and are arranged substantially parallel to each other so as to maintain a predetermined insulation distance a therebetween.
And the negative side main circuit conductor 35 with an insulating coating material 33
, And a plurality of mounting seats 36 for electrically connecting (contact-fixing) to a terminal described later are fixed to each other at a predetermined interval.

At one end of the main circuit conductor 30 having such a structure, mounting seats 36 are fixed to the terminals of the DC power source 1 and the smoothing capacitor 2 by screws 31, respectively, and the other end of the main circuit conductor 30 is an inverse converter. The semiconductor switch elements 21, 22, 23 and 24, 25, 26 (see FIG.
(Corresponding to semiconductor switch elements 8 to 10 and 16 to 18 of 5)
A mounting seat 36 is fixed to each of the terminals by a screw 32.

In FIGS. 1 to 4, 20 is a heat sink and 27 to 29 are output conductors for load output. In the main circuit conductor 30 of the first embodiment described above, the quotient of a (conductor spacing in FIG. 4) / b (conductor width in FIG. 4) can be reduced to zero or smaller than that of the conventional flat parallel conductor. . This is because the term of the conductor width b becomes large because of the wavy shape.

As a result, the stray inductance of the conductor is reduced as compared with the conventional flat parallel conductor, and the surge overvoltage can be suppressed. Conductor 3 placed in close contact
Since the currents flowing in the respective Nos. 4 and 35 are in opposite directions, the change in magnetic flux caused by this current is canceled out, and this also acts in the direction of reducing the stray inductance.

Since the stray inductance is reduced and the surge overvoltage is suppressed, the loss of the DC snubber or the individual snubber of the switch element is reduced, and the snubber can be downsized, and the device can be downsized. You can In addition, by integrating the pair of power supply conductors with the coating material, the number of assembling steps can be reduced.

(Second Embodiment) FIGS. 5 to 6 are views for explaining the second embodiment, FIG. 5 is a plan view of a semiconductor power converter, and FIG. It is the side view seen in the arrow direction.

In the first embodiment described above, the overall shape of the main circuit conductor is band-shaped, but in the present embodiment, the overall shape is a flat plate having substantially the same size as the outer surface of the inverse converter to which the main circuit conductor is attached. The other points are the same as those in the first embodiment.

Specifically, the main circuit conductor is formed by coating a corrugated positive side main circuit conductor 38 and a corrugated negative side main circuit conductor 39 with an insulating coating 37 at a predetermined interval.

In the main circuit conductor having such a structure, the negative electrode fixing screw 40, the positive electrode fixing screw 41, the positive electrode fixing screw 42, and the negative electrode fixing screw 43 constitute the DC power source 1, the smoothing capacitor 2, and the inverse converter. It is fixed to each terminal of the switch element. In addition, 44 is a cooler.

The second embodiment described above can also obtain the same effects as the first embodiment described above. (Third Embodiment) FIGS. 7 to 8 show a third embodiment of the present invention, FIG. 7 is a plan view of a main circuit conductor, and FIG. 8 is a view of FIG. 7 viewed in the direction of arrow XX. FIG.

The main circuit conductor comprises a positive side main circuit conductor 45, a negative side main circuit conductor 46 and an insulating coating 33,
Each of the positive electrode side main circuit conductor 45 and the negative electrode side main circuit conductor 46 is a strip-shaped conductor formed with a large number of projections 50 each having a substantially semicircular cross section, and the two are substantially parallel to each other so as to maintain a predetermined insulation interval therebetween. The main circuit conductor 45 on the positive electrode side in the arranged state,
The negative side main circuit conductor 46 is integrated by the insulating coating material 33.

The third embodiment described above can also obtain the same operational effects as the first embodiment described above. (Fourth Embodiment) FIGS. 9 to 11 show a fourth embodiment of the present invention. FIG. 9 is a plan view of a main circuit conductor.
0 is a side view of FIG. 9 as seen in the direction of arrow XX, and FIG.
FIG. 1 is a diagram for explaining the stray inductance and stray capacitance of the main circuit conductor.

The main circuit conductor is composed of the positive side main circuit conductor 47,
The negative side main circuit conductor 48 and the insulating coating 33 are formed. The positive side main circuit conductor 47 is formed by laminating a plurality of corrugated thin plate conductors coated with an insulating coating, and the negative side main circuit conductor 48 is a corrugated thin plate conductor. A plurality of positive electrode side main circuit conductors 47 and negative electrode side main circuit conductors 48, which are obtained by stacking a plurality of layers coated with an insulating coating material, are used.
Are arranged in parallel with each other at a predetermined interval, and the whole is coated with an insulating coating material 33.

According to the fourth embodiment described above, the stray inductance of the main circuit conductors 47 and 48 and the switching element 2
With high frequency current due to fast switching operation of 1-26,
Due to the so-called skin effect in which the current concentrates on the surfaces of the main circuit conductors 47, 48, it is possible to prevent an increase in conductor resistance and also to reduce the inductance.

Further, since the main circuit conductors 47 and 48 having a structure in which a plurality of conductors are respectively insulation-coated and laminated on each other are further insulation-coated, in addition to the above-mentioned effect of low inductance, when high-speed switching or surge occurs. It is possible to prevent an increase phenomenon of the conductor resistance due to the skin effect of the generated high frequency current. Furthermore, by using the laminated conductors, it is possible to suppress an increase in conductor resistance due to high-frequency current due to high-speed switching or the like, and to reduce the imbalance of the output current of each phase.

Here, the stray inductance and stray capacitance from the smoothing capacitor to the switch element conductor of the main circuit conductor of the fourth embodiment can be shown as shown in FIG. In FIG. 11, Lp1 to Lpn are stray inductances of the positive side main circuit conductor, Ln1 to Lnn are stray inductances of the negative side main circuit conductor, and Cs1 to Csn are stray capacitances generated between the conductors due to the close arrangement of the main circuit conductors. is there. Such a ladder circuit is similar to a noise filter and is used when lowering the circuit impedance and preventing the occurrence of surge overvoltage.

[0044]

According to the present invention, although the structure is relatively simple, the inductance of the main circuit conductor is reduced, and surge overvoltage caused by high di / dt of the switching element and stray inductance of the main circuit conductor is prevented. It is possible to provide a highly efficient and high-performance semiconductor power conversion device by suppressing the snubber loss and reducing the snubber loss.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of a semiconductor power conversion device of the present invention.

FIG. 2 is a side view seen in the direction of the arrow Y-Y in FIG.

3 is a plan view showing only the main circuit conductor of FIG. 1. FIG.

FIG. 4 is a side view seen in the direction of the arrow Y-Y in FIG.

FIG. 5 is a plan view showing a second embodiment of the semiconductor power conversion device of the present invention.

FIG. 6 is a side view of FIG. 5 as seen in the direction YY.

FIG. 7 is a plan view showing a third embodiment of the semiconductor power conversion device of the present invention.

FIG. 8 is a side view of FIG. 7 viewed in the direction of arrow XX.

FIG. 9 is a plan view showing a fourth embodiment of the semiconductor power conversion device of the present invention.

FIG. 10 is a side view of FIG. 9 viewed in the direction of the arrow YY.

11 is a conceptual diagram showing stray inductance and stray capacitance of the power supply conductor of FIG.

FIG. 12 is a main circuit connection diagram of upper and lower arm configurations for illustrating the principle of surge overvoltage generation in the conventional voltage type converter.

FIG. 13 is a surge overvoltage waveform diagram at the time of turning on the switch element of FIG. 12;

FIG. 14 is a surge overvoltage waveform diagram when the switch element of FIG. 12 is turned off.

FIG. 15 is a main circuit connection diagram showing an example of a conventional semiconductor power conversion device.

16 is a plan view of the semiconductor power conversion device of FIG.

FIG. 17 is a side view of FIG. 16 seen in the direction of arrow XX.

FIG. 18 is a main circuit connection diagram showing another example of the conventional semiconductor power conversion device.

FIG. 19 is a side view of FIG. 18 viewed in the direction of arrow XX.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Smoothing capacitor, 3 ... Positive side main circuit conductor (positive side power supply conductor), 4 ... Negative side main circuit conductor (negative side power supply conductor), 5 ... Positive side switch element, 6 ... Negative side switch element, 7 ... AC output terminal, 8 ... U phase switch element, 9 ... V phase switch element, 10 ... W phase switch element, 11 ... AC output terminal, 12, 44 ... Cooler, 20 ...
Heat sink, 21-26 ... Switch element, 27-29
... Output conductor, 30 ... Insulation coating material, 31, 32 ...
Screws, 33, 37 ... Insulating coating, 34, 39, 4
5, 47 ... Positive side main circuit conductor, 35, 38, 46, 48
... Negative electrode side main circuit conductor, 36, 49 ... Mounting seat, 40, 43
… Negative electrode fixing screws, 41, 42… Positive electrode fixing screws, Lp1 to L
pn: Stray inductance of the positive side main circuit conductor, Ln1 to L
nn ... Stray inductance of the negative side main circuit conductor, Cs1 to C
sn ... stray capacitance.

Claims (4)

[Claims] 1. A smoothing device for converting AC power of an AC power supply into DC power with large pulsation by a forward converter, and converting the converted DC power with large pulsation into smaller DC in a smoothing circuit section composed of a capacitor or the like. A circuit unit and a power converter that converts direct-current power with small pulsation obtained by the smoothing circuit into alternating-current power by an inverse converter composed of a plurality of semiconductor switch elements, wherein the smoothing circuit unit and the inverse converter For electrically connecting the semiconductor switch elements, each of which is formed in a wavy shape, and which are arranged substantially parallel to each other so as to maintain a predetermined insulation distance from each other. A semiconductor power conversion device comprising a main circuit conductor formed by integrating side main circuit conductors with an insulating coating material. 2. The semiconductor power conversion device according to claim 1, wherein the main circuit conductor has substantially the same size as an outer surface of the inverse converter to which the main circuit conductor is attached. 3. A smoothing for converting AC power of an AC power supply into DC power with large pulsation by a forward converter, and converting the converted DC power with large pulsation into smaller DC in a smoothing circuit section composed of a capacitor or the like. A circuit unit and a power converter that converts DC power with small pulsation obtained by the smoothing circuit into AC power by an inverse converter composed of a plurality of semiconductor switch elements, wherein the smoothing circuit unit and the inverse converter For electrically connecting the semiconductor switch elements, each having a plurality of semi-circular protrusions in cross section, and arranged substantially parallel to each other so as to maintain a predetermined insulation distance from each other. A semiconductor power conversion device comprising a main circuit conductor in which a positive side main circuit conductor and a negative side main circuit conductor are integrated by an insulating coating material. 4. A smoothing device for converting AC power of an AC power supply into DC power with large pulsation by a forward converter, and converting the converted DC power with large pulsation into smaller DC in a smoothing circuit section composed of a capacitor or the like. A circuit unit and a power converter that converts DC power with small pulsation obtained by the smoothing circuit into AC power by an inverse converter composed of a plurality of semiconductor switch elements, wherein the smoothing circuit unit and the inverse converter For electrically connecting the semiconductor switching elements of the above, each of which is formed by laminating main circuit conductor pieces, each of which is formed by coating a plurality of corrugated conductive plates with an insulating coating material. A semiconductor power conversion device comprising a main circuit conductor in which circuit conductors are arranged substantially parallel to each other.