JPH06327251A - Semiconductor converter - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the current imbalance between semiconductor elements with a large number of parallel elements. [Configuration] u, v, w at which currents can flow simultaneously during commutation
During the commutation period, the three-phase secondary leads 31u, 31v, and 31w are arranged side by side on a plane perpendicular to the longitudinal direction of the cooling conductor 5A, and the semiconductor element 4u is similarly attached to the surface of the cooling conductor 5A. Of the semiconductor element 4v, 4u3, 4u4 of the plurality of semiconductor elements 4u1, 4u2, 4u3, 4u4 flows in the direction perpendicular to the longitudinal direction of the cooling conductor 5A and flows in the semiconductor element 4v or 4w of the opposite phase. Are the same, the difference between the inductances of the respective semiconductor elements 4u1, 4u2, 4u3, 4u4 and the secondary lead 31uA connected thereto is small, and as a result, the current sharing between the respective semiconductor elements is unbalanced. The equilibrium becomes smaller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor conversion device such as a rectifier constructed by connecting a large number of semiconductor elements such as diodes in parallel, and more particularly to a structure for equalizing the current flowing through each semiconductor element. .

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram of a double star connection transformer rectifier as an example of a semiconductor converter. In this figure, the power of the three-phase AC power supply 1 is stepped down from a high voltage to a predetermined low voltage by a rectifier transformer 2 and supplied to a rectifier 4. The rectifier transformer 2 is provided with two secondary windings 22 and 23 of star connection, and a secondary lead 31 drawn from these (representing the six secondary leads in the figure).
Are respectively provided with semiconductor elements 4 (representing 6 semiconductor elements), and the positive electrodes of these are collectively connected to P
It is connected to terminal 5. The neutral points of the secondary windings 22 and 23 are connected to the N terminal 50 via the correlation reactor 3.

FIG. 6 is a partial elevational view of the double star connection transformer / rectifier of FIG. 5, and FIG. 7 is a partial side view of the same, mainly showing the upper portion of the rectifier transformer 2 provided with the semiconductor element 4. It is shown in FIG. In these figures, a cooling conductor 5 which is also a P terminal is provided along the left and right of FIG. 6, and the arrows shown on the right side show inflow and outflow of cooling water without reference numerals, and the cooling water is the cooling conductor. 5 enters a cooling pipe embedded in the reference numeral 5, passes through a semicircular cooling pipe shown on the left side, passes through the cooling pipe in the cooling conductor 5 again, and exits from the right side. During this time, the cooling water cools the cooling conductor 5, thereby cooling the semiconductor elements 4u, 4v, 4w and the semiconductor elements 4x, 4y, 4z attached to the opposite side of the cooling conductor 5 and not visible in FIG.

One surface of the semiconductor element 4u is attached to the tip of the secondary lead 31u drawn from the rectifier transformer 2, and the other surface is attached to the front surface of the cooling conductor 5.
In FIG. 5, the semiconductor device 4u indicated by the symbol of one device is shown.
Is actually four elements 4u1, 4u2, 4u3, 4u4
It consists of The number of elements is four, which is merely an example, and may be twenty in an actual device.

A semiconductor element 4v is provided next to the semiconductor element 4u.
Next to that, the semiconductor elements 4w are attached to the cooling conductor 5 in the same structure side by side in the longitudinal direction of the cooling conductor 5. The semiconductor elements 4x, 4y, 4z are also semiconductor elements 4u, 4
It is attached to the surface of the cooling conductor 5 opposite to v and 4w. The N terminal 50 of FIG. 5 is drawn out from the rectifier transformer 2 separately from the secondary lead 31 as shown in FIG. 7.

FIG. 8 is a waveform diagram showing current sharing of the semiconductor elements 4u1, 4u2, 4u3, 4u4 constituting the semiconductor element 4u. In this figure, the horizontal axis represents time and the vertical axis represents current value. Waveform 101 is waveform 10 of semiconductor element 4u1.
2 is the same as the waveforms 103 and 10 of the semiconductor element 4u2.
Reference numerals 4 are semiconductor elements 4u3 and 4u4, respectively.
The period T ₁ is a commutation period when the current rises after the u phase is ignited, T ₂ is a non-commutation period during that period, and the period T ₃ is a commutation period when the current falls.

Period T₁The first four waveforms 101-10
4 rises all at once, but the lower the number, the better the rise
The angle is large. Therefore, the commutation period T₁Reached between
Waveform 101 has the largest current value and waveform 104 has the largest
small. Period T₂When entering, mainly of each semiconductor element
Forward voltage-final value of current determined by current characteristics
To converge based on the time constant of each element.
Convert Next period T ₃Each current suddenly entered
And finally the current of each waveform becomes zero
The half-cycle flow of phases ends.

The rising angle of the waveform 101 in the period T ₁ is large because the inductance between the semiconductor element 4u1 and the secondary lead 31u1 provided with the semiconductor element 4u1 is small. As is well known, the current sharing in a parallel circuit is mainly determined by the inductance of the circuit for a current having a large temporal change such as high frequency, and if there is a difference in the inductance values, the current sharing becomes unbalanced.

As can be seen in FIG. 6, the semiconductor element 4u1 is half
Located on the side close to the conductor elements 4v and 4w, the semiconductor element 4u4
Is the farthest position on the contrary. Temporal in the commutation period
The current component that changes rapidly to
Since it flows, the commutation period T ₁Is between the u phase and the v phase
6 and the secondary lead 3u in the upward direction of FIG.
If an electric current flows, the lead 3v goes down in the opposite direction.
Current flows. In case of such current distribution
The smaller the lead, the smaller the inductance
It is known. From this, when commutating as described above
Current imbalance occurs.

[0010]

If there is a current imbalance between the semiconductor elements connected in parallel as described above, the semiconductor element having the largest shared current determines the total current capacity, resulting in the same current capacity. Even with the same number of parallel elements, the current capacity of the device decreases when the current imbalance ratio is high. Therefore, in order to obtain the required current capacity, it is necessary to increase the number of elements in parallel, resulting in a problem that the device costs up. Furthermore, in general, there is a relationship that the current imbalance rate increases as the number of parallels increases.
When the number of parallels is increased to secure the current capacity, the unbalance rate increases, and as the number of parallels increases, the current capacity does not increase and the number of parallels must be further increased. There is also a possibility.

An object of the present invention is to solve the above problem and to provide a semiconductor conversion device capable of effectively reducing the current imbalance between elements even if the number of parallel semiconductor elements is large.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a secondary side lead for each phase drawn from the secondary side of a transformer for a three-phase rectifier, and these secondary leads are provided. In a semiconductor conversion device provided with a plurality of semiconductor elements connected in parallel to one phase and provided with a cooling conductor that is attached to the same poles of these semiconductor elements of all phases and that also serves as a cooling and current collector for the semiconductor elements, Secondary leads of three phases, through which currents can flow at the same time during the commutation period, are drawn out side by side in a plane perpendicular to the longitudinal direction of the cooling conductor, and semiconductor elements attached to the secondary leads of the respective phases are cooled conductors. Of the cooling conductor is symmetrically arranged with respect to the longitudinal direction of the cooling conductor, and the cooling conductor has a square cross-sectional shape, and the three surfaces of the two side surfaces and the lower surface have three phases. semiconductor Shall each child is attached, also, the cross-sectional shape of the cooling conductor is equilateral triangle, and made respectively attached semiconductor elements of the three phases into three surfaces of its two sides and bottom.

[0013]

In the structure of the present invention, the secondary leads of the three phases through which currents can simultaneously flow during the commutation period are arranged side by side in a plane perpendicular to the longitudinal direction of the cooling conductor, and the secondary leads of the respective phases are arranged. By arranging and mounting the semiconductor elements attached to the leads on the surface of the cooling conductor symmetrically with respect to the longitudinal direction of the cooling conductor, a rapid current that changes with time during commutation is perpendicular to the longitudinal direction of the cooling conductor. Since the currents flow between the phases in the same direction, the current flow paths of the respective semiconductor elements are the same, the difference in the commutation inductance between the respective semiconductor elements is small, and as a result, the imbalance in current sharing is small. Further, it is possible to make the cross-sectional shape of the cooling conductor square or equilateral triangle to secure three surfaces on which the semiconductor elements of the three phases are respectively mounted.

[0014]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a partial elevation view of a double star connection transformer rectifier showing an embodiment of the present invention, and FIG. 2 is a partial side view of the same.
The same components as those in FIGS. 6 and 7 are designated by common reference numerals, and detailed description thereof will be omitted. In these drawings, the secondary leads 31uA, 31vA and 31wA are drawn out from the rectifier transformer 2 in a state of being arranged side by side on the paper surface of FIG. 2, and are directly subjected to the cooling conductor 5A via the semiconductor elements 4u, 4v and 4w.
Mounted on.

The cooling conductor 5A has a square cross-sectional shape, and the semiconductor elements 4u, 4v, and
4w is attached, and along with this, the secondary leads 31 to which the semiconductor element 4 is attached are appropriately routed around these tips. The semiconductor device 4 shown in FIG.
Since the semiconductor element 4v is hidden by the secondary lead 31uA and invisible with respect to u and the secondary lead 31uA, its position is shown by a dotted line. The secondary lead 31vA has the same structure as the secondary lead 31yA in FIG. The semiconductor element 4w and the secondary lead 31wA are the semiconductor element 4u and the secondary lead 31uA.
On the other side of. That is, the three phase semiconductor elements 4 of u, v, and w and the secondary lead 31A are arranged at the same position in the longitudinal direction of the cooling conductor 5A. The same applies to the three phases x, y, and z. As described with reference to FIG. 5, the current components having a rapid temporal change during commutation of the semiconductor elements 4u, 4v, 4w flow in opposite directions. Therefore, as described above, by disposing the secondary lead 31 and the semiconductor element 4, the aforementioned current component flows in the direction perpendicular to the longitudinal direction of the cooling conductor 5A, and the four semiconductor elements 4u1 and 4u.
2, 4u3, 4u4 and the other four semiconductor elements 4v1,
4v2, 4v3 or semiconductor elements 4w1, 4w2, 4w
The currents flowing between 3 and 4w4 are parallel, and the paths have the same length. As a result, the difference in the commutation inductance between the respective semiconductor elements 4 becomes smaller and the current imbalance rate becomes smaller than in the case of the conventional configuration. Semiconductor element 4
The same applies to x, 4y, and 4z.

The cross-sectional shape of the cooling conductor 5A is a square, which is shown in FIG. 2 as semiconductor elements 4x, 4y, 4z.
This is because the sides required for mounting have the same length. In the cooling conductor 5 of FIG. 7, the thickness dimension, which is the dimension in the left-right direction of the figure, may be a small value determined from the current value, whereas in the cooling conductor 5A of FIG. 2, the width dimension and the thickness dimension are at least the semiconductor element 4. Since it is necessary to make it the size necessary for mounting, and in that case it often exceeds the required cross-sectional area of the cooling conductor, shorten the side length as much as possible to reduce the cross-sectional area and save material. However, if you do so, it will inevitably become a square as shown.

FIG. 3 is a partial elevational view of a double star connection transformer rectifier showing another embodiment of the present invention, and FIG. 4 is a partial side view of the same, showing the same components as those in FIGS. 1 and 2. A common code is attached and detailed explanation is omitted. The feature of these FIG. 3 and FIG. 4 is that the cross-sectional shape of the cooling conductor 5B is an equilateral triangle. If the cooling conductor 5A of FIG. 2 has the same side length, the cooling conductor 5B of FIG. 4 naturally has a smaller cross-sectional area, thus saving material and making it lighter. The secondary lead 31B also has an appropriate routing shape according to the shape of the cooling conductor 5B. In addition, the reason why one side of the equilateral triangle is brought down is that the secondary lead 31B is most rational in this case.

[0018]

As described above, according to the present invention, the secondary leads of three phases in which currents can simultaneously flow during the commutation period are arranged side by side on a plane perpendicular to the longitudinal direction of the cooling conductor, and the semiconductor element is elongated. Due to the symmetrical arrangement in the direction, the current component with a large temporal change during the commutation period flows in the direction perpendicular to the longitudinal direction of the cooling conductor and flows between the phases, and the current of each of the plurality of semiconductor elements is different. Are the same, the difference in the inductance between the respective semiconductor elements and the secondary lead is small, and as a result, the imbalance in current sharing between the respective semiconductor elements is small. This means that the current value of the semiconductor element with the largest current sharing becomes smaller, and as a result, the number of parallel semiconductor elements can be reduced to secure the same current capacity, which leads to a reduction in the cost of the semiconductor conversion device. The effect is that compactness can be realized. Also, make the cross-sectional shape of the cooling conductor square,
The effect described above can be appropriately realized by forming three equilateral triangles and securing three surfaces for mounting the semiconductor elements of the three phases.

[Brief description of drawings]

FIG. 1 is a partial elevation view of a double star connection transformer rectifier showing an embodiment of the present invention.

FIG. 2 is a partial side view of FIG.

FIG. 3 is a partial elevation view of a double star connection transformer / rectifier showing another embodiment of the present invention.

FIG. 4 is a partial side view of FIG.

FIG. 5 is a circuit diagram of a double star connection transformer rectifier as an example of a semiconductor converter.

FIG. 6 is a partial elevation view of a conventional double star connection transformer rectifier.

7 is a partial side view of FIG.

FIG. 8 is a waveform diagram showing current sharing of a semiconductor element.

[Explanation of symbols]

 2 Transformer for three-phase rectifier 22 Secondary winding 31 Secondary lead 31uA, 31vA, 31wA, Secondary lead 31xA, 31yA, 31zA, Secondary lead 31uB, 31vB, 31wB Secondary lead 31xB, 31yB, 31zB Secondary lead 4 semiconductor element 4u semiconductor element 4u, 4v, 4A semiconductor element 4x, 4y, 4z semiconductor element 4u1, 4u2, 4u3, 4u4 semiconductor element 5A cooling conductor 5B cooling conductor

Claims (3)

[Claims] 1. A secondary lead for each phase drawn from a secondary winding of a rectifier transformer, a plurality of semiconductor elements provided on these secondary leads and connected in parallel to one phase, and a plurality of phases. In the semiconductor conversion device equipped with the same pole of these semiconductor elements and having a cooling conductor that also serves as a cooling and current collector for the semiconductor elements, the secondary leads of the three phases in which currents can simultaneously flow during the commutation period are cooled. The semiconductor elements attached to the secondary leads of the respective phases arranged side by side in a plane perpendicular to the longitudinal direction of the conductor and arranged symmetrically with respect to the longitudinal direction of the cooling conductor and mounted on the surface of the cooling conductor. A semiconductor conversion device characterized by: 2. The semiconductor device according to claim 1, wherein the cooling conductor has a square cross-sectional shape, and semiconductor elements of three phases are attached to three surfaces of two side surfaces and a lower surface of the cooling conductor. Converter. 3. The semiconductor according to claim 1, wherein the cooling conductor has an equilateral triangular cross-sectional shape, and the semiconductor elements of three phases are attached to the three surfaces of the two side surfaces and the lower surface, respectively. Converter.