Transformer assembly with medium frequency transformers

Patent metadata

Field	Value
Publication number	US-11480602-B2
Application number	US-202016925999-A
Country	US
Kind code	B2
Filing date	Jul 10, 2020
Priority date	Jul 16, 2019
Publication date	Oct 25, 2022
Grant date	Oct 25, 2022

Abstract

Transformer assembly including a first transformer stage having a plurality of first-stage transformer cells; and a second transformer stage. An input of the second transformer stage is connected to an output of the first transformer stage. A lightning impulse breakdown voltage of a transformer cell of the second stage is at least double of a lightning impulse breakdown voltage of transformer cells of the first stage.

First claim

The invention claimed is:

1. A transformer assembly comprising:
a first transformer stage having a plurality of first-stage transformer cells, each of the first-stage transformer cells comprising a converter and a medium frequency transformer connected in series to each other, wherein the respective inputs of each of the plurality of first-stage transformer cells are connected in series and the respective outputs of each of the plurality first-stage transformer cells are connected in parallel to form the output of the first transformer stage; and
a second transformer stage comprising at least one second-stage transformer cell, the second-stage transformer cell comprising a medium frequency transformer and a converter connected in series to each other, wherein
a lightning impulse breakdown voltage of the at least one second-stage transformer cell is at least double of a lightning impulse breakdown voltage of one of the first-stage transformer cells, wherein the lightning impulse breakdown voltage is the peak voltage of a lightning impulse between an input and an output of the respective transformer cell, at which the respective transformer cell breaks down during a lightning impulse test, and wherein
an input of the second transformer stage is connected to the output of the first transformer stage.

2. The transformer assembly according to claim 1 , wherein the at least one second-stage transformer cell is a plurality of second-stage transformer cells connected in parallel to each other.

3. The transformer assembly according to claim 1 , wherein the transformation ratio of the first transformer stage is more than the transformation ratio of the second transformer stage.

4. The transformer assembly according to claim 1 , wherein the transformation ratio of the second transformer stage is between 1.0 and 10.0.

5. The transformer assembly according to claim 1 , wherein a winding of the medium frequency transformer of the at least one second-stage transformer cell has an additional solid or liquid insulation compared to the plurality of first-stage transformer cells.

6. The transformer assembly according to claim 1 , wherein the number of first-stage transformer cells of the first transformer stage is larger than the number of the at least one second-stage transformer cell of the second transformer stage, preferably by a factor of at least 2, and particularly preferably by a factor of at least 4.

7. The transformer assembly according to claim 1 , wherein the medium frequency transformer of the at least one second-stage transformer cell includes at least one bushing designed for withstanding a lightning impulse.

8. The transformer assembly according to claim 1 , wherein the medium frequency transformers of any one of the plurality of first-stage transformer cells has at most half the mass of the medium frequency transformer of any one of the at least one second-stage transformer cell.

9. The transformer assembly according to claim 1 , wherein respective outputs of the plurality of first-stage transformer cells are connected to the output of the first transformer stage and thereby to the input of the second transformer stage.

10. The transformer assembly according to claim 1 , having a higher-voltage input terminal at the input of the first transformer stage, and a lower-voltage output terminal at the output of the second transformer stage.

11. The transformer assembly according to claim 1 , wherein the converter of the at least one second-stage transformer cell is one of an AC-to-DC converter or an AC-to-AC converter.

12. The transformer assembly according to claim 1 , wherein an input of the transformer assembly is connected to a surge arrester.

13. The transformer assembly according to claim 1 , wherein the input of each of the medium frequency transformers of the plurality of first-stage transformer cells is connected to a surge arrester.

14. A solid state transformer having a transformer assembly, including:
a first transformer stage having a plurality of first-stage transformer cells, each of the first-stage transformer cells comprising a converter and a medium frequency transformer connected in series to each other, wherein the respective inputs of each of the plurality of first-stage transformer cells are connected in series and the respective outputs of each of the plurality first-stage transformer cells are connected in parallel to form the output of the first transformer stage; and
a second transformer stage comprising at least one second-stage transformer cell, the second-stage transformer cell comprising a medium frequency transformer and a converter connected in series to each other, wherein
a lightning impulse breakdown voltage of the at least one second-stage transformer cell is at least double of a lightning impulse breakdown voltage of one of the first-stage transformer cells, wherein the lightning impulse breakdown voltage is the peak voltage of a lightning impulse between an input and an output of the respective transformer cell, at which the respective transformer cell breaks down during a lightning impulse test, and wherein
an input of the second transformer stage is connected to the output of the first transformer stage.

15. The transformer assembly according to claim 14 , wherein the at least one second-stage transformer cell is a plurality of second-stage transformer cells connected in parallel to each other.

16. The transformer assembly according to claim 14 , wherein the transformation ratio of the first transformer stage is more than the transformation ratio of the second transformer stage.

17. The transformer assembly according to claim 14 , wherein the transformation ratio of the second transformer stage is between 1.0 and 10.0.

18. The transformer assembly according to claim 14 , wherein a winding of the medium frequency transformer of the at least one second-stage transformer cell has an additional solid or liquid insulation compared to the plurality of first-stage transformer cells.

Assignees

• Abb Schweiz Ag

Inventors

• Drofenik Uwe
• Gradinger Thomas
• Canales Francisco

Classifications

• H02M5/00 Primary

  Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases · CPC title

• H02M5/225

  comprising two stages of AC-AC conversion, e.g. having a high frequency intermediate link · CPC title

• H01F38/16 Primary

  Cascade transformers, e.g. for use with extra high tension · CPC title

• H02M1/0067

  Converter structures employing plural converter units, other than for parallel operation of the units on a single load · CPC title

• G01R31/62

  Testing of transformers · CPC title