KR20170031300A

KR20170031300A - Multi-level inverter

Info

Publication number: KR20170031300A
Application number: KR1020150128424A
Authority: KR
Inventors: 최윤석
Original assignee: 현대중공업 주식회사
Priority date: 2015-09-10
Filing date: 2015-09-10
Publication date: 2017-03-21

Abstract

The present invention relates to a multi-level inverter capable of minimizing a temperature rise, comprising: a transformer having a multi-winding transformer; an inverter unit having a plurality of power cells located above the transformer; And a plurality of connection conductors electrically connecting the cells, wherein the multi-winding transformer can be arranged such that the winding axis is parallel to the bottom surface.

Description

Multi-level inverter {MULTI-LEVEL INVERTER}

The present invention relates to a multilevel inverter capable of minimizing a temperature rise.

The multi-level inverter system consists of several power cells connected in series according to each phase. Each power cell has an independent single-phase inverter structure. By connecting several power cells, which are low-voltage low-power semiconductors, they are close to high voltage and sinusoidal So that the output can be obtained.

Generally, a multi-level inverter includes a plurality of power cell inverters and a multi-winding transformer having a plurality of secondary windings for supplying voltage to the power cell inverters.

However, the conventional multi-level inverter uses a conductor made of a cable or a metal to connect a plurality of power cell inverters to the secondary side of the multi-winding transformer. This causes a variation in the power input to the power cell inverter depending on the length of the cable or the metal conductor.

When the power source voltage of the power cell inverter is varied, an in-phase voltage unbalance is generated in the process of generating an output voltage by connecting a plurality of power cell inverters in series.

If such an imbalance is intensified, there is a problem that the input voltage between phases of the motor supplied with power from the multi-level inverter is unbalanced, so that the vibration and noise of the motor are increased or the insulation breakdown of the motor exceeds the insulation voltage of the motor. .

In addition, the conventional multi-level inverter draws air into the lower portion of the transformer to cool the space between the windings of the multi-winding transformer, and discharges the air to the upper portion. However, in this case, since the air flow of the air introduced from the outside must be changed in order to introduce air into the lower portion of the multi-winding transformer, there is a problem that the space between the windings can not be uniformly cooled.

Therefore, in the case of a winding having a small amount of air to be introduced, the temperature is higher than that of a winding having a large air inflow, so that burning due to heat generation can be caused. In addition, if the amount of cooling air is calculated based on a small number of windings to prevent such burning, the amount of the incoming air is more than necessary in the case of many windings, resulting in a loss of energy consumption of the cooling fan.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-level inverter capable of minimizing a connection length between a power cell and a multi-winding transformer.

Another object of the present invention is to provide a multi-level inverter capable of increasing cooling efficiency.

A multi-level inverter according to an embodiment of the present invention includes a transformer having a multi-winding transformer disposed therein, an inverter unit disposed at an upper portion of the transformer unit and having a plurality of power cells, an inverter unit electrically connecting the multi- Wherein the multi-winding transformer may be arranged such that the winding axis is parallel to the bottom surface.

The apparatus may further include a cooling unit disposed on a front surface or a rear surface of the transforming unit and configured to introduce air into the transforming unit or to discharge air inside the transforming unit to the outside.

In the present embodiment, the cooling unit can flow air in a direction parallel to the winding axis of the multi-winding transformer.

In the present embodiment, at least one of the primary coil and the secondary coil of the multi-winding transformer may be formed of aluminum.

In the present embodiment, the plurality of power cells may be stacked in layers on the upper portion of the transforming unit.

According to the embodiment of the present invention having such a configuration, the length of the connection conductor for electrically connecting the multi-winding transformer and the power cells can be minimized. Therefore, the impedance of the connecting conductor is reduced, the deviation of the voltage input to each power cell inverter is minimized, and the imbalance between the output voltages due to this can be minimized.

In addition, since the multi-winding transformer is disposed on the floor and the cooling air flows in the horizontal direction, the cooling efficiency can be improved. In addition, as the cooling efficiency becomes higher, there is an advantage that not only copper but also aluminum having a larger heat generation than copper can be used as the material of the winding.

1 is a perspective view schematically showing a multi-level inverter according to an embodiment of the present invention;
Fig. 2 and Fig. 3 are exploded perspective views of Fig. 1; Fig.
4 is a sectional view taken along the line AA in Fig.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. In addition, the shape and size of elements in the figures may be exaggerated for clarity.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view schematically showing a multi-level inverter according to an embodiment of the present invention, and FIGS. 2 and 3 are exploded perspective views of FIG.

4 is a cross-sectional view taken along line AA of FIG.

1 to 4, a multi-level inverter 100 according to the present embodiment includes an enclosure 90, a transformer 10 and an inverter 20 disposed inside or outside the enclosure 90, And a cooling unit 50.

The transformer 10 includes a multi-winding transformer 11 that receives a main power and supplies power to the inverter 20.

The multi-winding transformer 11 according to the present embodiment includes an iron core 12 and a plurality of windings 13 wound around the iron core 12. The multi- The winding 13 may also include a primary winding having a number of turns proportional to the main voltage and a secondary winding having a number of turns proportional to the voltage of the power cell 21 .

The primary windings of the multi-winding transformer 11 may have a three-phase wired configuration, for example, a turn number proportional to main voltages AC 3300V, AC 4160V, AC 6600V, AC 11000V, and AC 13800V.

The secondary side winding includes a plurality of windings having a phase difference with respect to the primary side winding 13 and the structure of the secondary side winding can be determined according to the number of the power cells 21 of the inverter unit 20. [

The windings of the multi-winding transformer 11 may be formed of a copper material. However, in the case of this embodiment, the cooling efficiency of the multi-winding transformer 11 can be increased through the cooling unit 50 described later. In this case, it is also possible to form a winding with an aluminum material having a relatively large heat generation. Thus minimizing the manufacturing cost.

The multi-winding transformer 11 according to the present embodiment is disposed on the floor. More specifically, the winding axis, which is the center of the coil-shaped winding 13, is arranged so as to be parallel to the bottom surface or the horizontal surface.

Accordingly, the multi-winding transformer 11 is arranged in a form having a larger width than the thickness (or height).

Also, the space between the windings 13 of the multi-winding transformer 11 is used as a passage through which the air flows. As the multi-winding transformer 11 is arranged in a lying-down form, .

Therefore, the air passage according to the present embodiment may be configured such that air is introduced into the front surface of the transforming unit 10 and then discharged to the rear surface of the transforming unit 10, or may be introduced to the rear surface and discharged to the front surface. 4, the cooling unit 50 to be described later may be disposed on the front surface of the transforming unit 10, and the air holes 55 may be disposed on the rear surface thereof. However, the present invention is not limited thereto, and it is possible to arrange them at positions opposite to each other.

The inverter unit 20 is disposed above the transformer 10.

The inverter unit 20 includes a plurality of power cells 21 that receive a plurality of AC power from the transformer 10, that is, the multi-winding transformer 11, convert the DC power to DC, and then convert the DC power to AC.

The power cell 21 is an independent single-phase inverter. The inverter unit 20 connects several power cells 21, which are low-voltage low-power semiconductors, so as to obtain a high-voltage and a sinusoidal output.

The plurality of power cells 21 are connected in series to each phase so as to output a voltage to the three-phase motor, which is a load of the multi-level inverter 100.

A plurality of power cells 21 according to the present embodiment can be stacked and arranged. For example, the power cells 21 may be arranged so that a plurality of the power cells 21 are arranged longitudinally and laterally above the transforming unit 10. [

In addition, since the power cell 21 according to the present embodiment can be formed to have a length corresponding to the length of the multi-winding transformer 11, the power cell 21 can be formed in a wider area than in the prior art. Therefore, a larger number of low-voltage low-power semiconductors than the conventional one can be disposed in one power cell 21, and a higher output can be supplied through one power cell 21. [

The connecting conductor 30 may be formed of a conductor wire or a conductor plate and electrically connects the multi-winding transformer 11 and the power cells 21. [

In this embodiment, the power cells 21 are connected in series to each phase. Thus, the connection conductors 30 can increase in proportion to a multiple of the number of series connections of the power cells 21.

On the other hand, the impedance of the connection conductor 30 increases in proportion to the length, and a difference in input voltage between the power cells 21 and the input voltages of the power cells 21 may occur due to the difference in impedance depending on the length difference have.

As described above, since the inverter unit 20 according to the present embodiment is disposed above the transformer 10, the distance between the multi-winding transformer 11 and the power cell 21 can be minimized compared with the conventional case .

Therefore, the length of the coupling conductor 30 connecting the multi-winding transformer 11 and the power cell 21 can be minimized, and the impedance generated in the coupling conductor 30 can be reduced.

4, the cooling unit 50 is disposed on the front surface or the rear surface of the transforming unit 10 and supplies air to the inside of the transforming unit 10 or discharges the air inside the transforming unit 10 to the outside . At this time, the air supplied by the cooling unit 50 flows into the interior of the multi-winding transformer 11 along the horizontal direction (arrow), and then flows along the horizontal direction through the air hole 55 to the inside of the transforming unit 10 And is discharged to the outside.

To this end, the cooling section 50 may include an air supply device such as a cooling fan.

Since the cooling section 50 is formed uniformly in the direction parallel to the winding axis, the flow of the air inside and outside the transformer 11 can be increased.

In the multilevel inverter according to the present embodiment having the above configuration, since the multi-winding transformer is disposed under the power cells, the length of the connection conductor for electrically connecting the multi-winding transformer and the power cells can be minimized. Therefore, the impedance of the connecting conductor is reduced, the deviation of the voltage input to each power cell inverter is minimized, and the imbalance between the output voltages due to this can be minimized.

In addition, when the variation of the voltage is minimized by minimizing the length of the connecting conductor, the waveform distortion of the multi-winding transformer can be reduced and the vibration and noise of the motor due to the unbalanced phase of the voltage input to the motor And it is possible to lower the possibility that the insulation of the winding is broken due to the insulation voltage of the motor being exceeded.

It is also possible to reduce the heat generation of the conductor due to the increase of the impedance of the connection conductor and to prevent the increase of the inrush current due to the increase of the impedance or the increase of the capacitance between the parallel connection conductors.

In addition, the multi-level inverter 100 according to the present embodiment can improve the cooling efficiency by horizontally arranging the multi-winding transformer. Also, even if the number of windings of the multi-winding transformer is increased, the influence of the increased winding load on the other winding can be minimized, so that the number of windings of the secondary winding portion can be increased.

In addition, as the cooling efficiency becomes higher, there is an advantage that not only copper but also aluminum having a larger heat generation than copper can be used as the material of the secondary winding.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

100: Multi-level inverter 90: Enclosure
10: transformer 11: multi-winding transformer
20: inverter section 21: power cell
30: connection conductor
50:
55: air hole

Claims

A transformer having a multi-winding transformer disposed therein;
An inverter unit located at an upper portion of the transforming unit and having a plurality of power cells;
A plurality of connection conductors electrically connecting the multi-winding transformer and the power cells;
/ RTI >
Wherein the multi-winding transformer is arranged such that the winding axis is parallel to the bottom surface.

The method according to claim 1,
Further comprising a cooling unit disposed on a front surface or a rear surface of the transforming unit and configured to introduce air into the transforming unit or to discharge air inside the transforming unit to the outside.

The refrigerator according to claim 2,
And the air flows in a direction parallel to the winding axis of the multi-winding transformer.

The multi-winding transformer according to claim 1,
Wherein at least one of the primary coil and the secondary coil is formed of an aluminum material.

2. The power cell of claim 1,
And a plurality of layers are stacked and arranged on an upper portion of the transforming unit.