AU2020227108A1

AU2020227108A1 - Multi-secondary transformer

Info

Publication number: AU2020227108A1
Application number: AU2020227108A
Authority: AU
Inventors: Serge MERCIER-MARICAL; Diogo NASCIMENTO TELLES DE MORAES; Gianluca Ranalletta
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2019-09-06
Filing date: 2020-09-04
Publication date: 2021-03-25
Also published as: EP3790028A1; FR3100652A1

Abstract

Transformer having a magnetic core (41) having a central axis, a primary winding (11) and a plurality of secondary windings (1311 to 1312, 1321 to 1322), all of the windings being 5 concentric about the central axis of the magnetic core, characterized in that the plurality of secondary windings is distributed into at least one layer of windings (121, 122), the at least one layer of windings having a predetermined number of secondary windings positioned next to one another, each secondary winding having one and the same number of turns distributed over substantially the length of the magnetic core (41), the respective distances from the 0 secondary windings to the primary winding (11) being within a predetermined range. 1/2 30 100 2 FI.I 121 123 } 2 11 ~113 FIG. 2

Description

1/2

30

100 2

FI.I

121 123 } 2 11 ~113 FIG. 2

MULTI-SECONDARY TRANSFORMER

Priority

This application claims priority from French Application No 1909852 filed on 6 September 2019. The entire content of this priority application is hereby incorporated by reference.

Technical field

The present invention relates to the field of electrical transformers. It relates more particularly to electrical transformers having a primary circuit and a plurality of secondary circuits.

Such a transformer is applied in various fields of electrical distribution, for example in electrical distribution circuits including photovoltaic or wind-based electricity production.

Hereinafter, consideration is given by way of example to a transformer intended for an electric vehicle charging station.

Prior art

An electric vehicle charging station on the whole has a transformer with a high-voltage primary winding and at least one low-voltage secondary winding. The low-voltage secondary winding is connected to an electric vehicle charging point to which a user connects his vehicle in order to recharge the battery thereof.

An electric vehicle charging station generally has a plurality of charging points, for example six charging points. Each of the charging points is connected to the output of a low-voltage secondary winding. It is necessary for all of the charging points to have the same electrical characteristics, in particular one and the same short-circuit voltage and balanced ampere turns, regardless of the number of charging points that are used simultaneously.

It is possible to provide as many transformers as there are charging points in the charging station. This solution is however expensive.

Moreover, EP 2 546 335 describes a transformer having a magnetic core, a primary winding and secondary windings. The secondary windings are distributed by being separated from one another by intervals in the direction of a central axis of the magnetic core. Each secondary winding faces only part of the primary winding and of the magnetic core.

CN203085334 describes a transformer structure having a plurality of secondary windings connected in series. The distances from the secondary windings to the primary winding increase from one secondary winding to the next, and the voltages generated by the secondary windings also increase from one secondary winding to the next. This type of structure does not make it possible to deliver identical voltages via the secondary windings.

EP 0 097 367 describes a transformer of the type having a divided structure. It has a primary winding in two parts that correspond respectively to two divided secondary windings. This structure is similar to two transformers in parallel on one and the same core. If only one of the secondary windings is connected to a load, only the primary winding part corresponding thereto is activated, and the other primary winding and the other secondary winding are deactivated, thereby producing an imbalance in the leakage fluxes.

US 2006 0091988 describes a transformer having a primary winding and a plurality of secondary windings positioned in winding slots formed along a central core. The transformer has insulating walls. The primary winding and the secondary windings do not face one another and face only part of the central core.

None of these structures has secondary circuits that have the same electrical characteristics, in particular one and the same short-circuit voltage and balanced ampere-turns, regardless of the number of secondary circuits that are used simultaneously.

These structures are not suitable for applications that require these characteristics. In .o particular, they are not suitable for an electric vehicle charging station having a plurality of charging points, with a single transformer and whose charging points are able to operate independently of one another.

Disclosure of the invention

The invention aims to solve the problems from the prior art by providing a transformer having a magnetic core having a central axis, a primary winding and a plurality of secondary windings, all of the windings being concentric about the central axis of the magnetic core, characterized in that the plurality of secondary windings is distributed into at least one layer of windings, the at least one layer of windings having a predetermined number of secondary windings positioned next to one another, each secondary winding having one and the same number of turns distributed over substantially the length of the magnetic core, the respective distances from the secondary windings to the primary winding being within a predetermined range.

The invention proposes a transformer with a plurality of secondary circuits that have the same electrical characteristics, in particular one and the same short circuit voltage and balanced ampere-turns, regardless of the number of secondary circuits that are used simultaneously.

The short-circuit voltages or impedances of the secondary windings are substantially equal to one another.

The secondary windings all handle the same magnetic flux.

According to one preferred feature, the at least one layer of secondary windings, in the direction of the central axis of the magnetic core, has a stack of turns of the secondary windings, alternating and in a repeating pattern.

According to one preferred feature, the respective distances from the secondary windings to the primary winding are substantially equal.

According to one preferred feature, the transformer according to the invention is used in an electric vehicle charging station.

The invention also relates to an electric vehicle charging station having a transformer as described above.

By virtue of the invention, it is possible to design an electric vehicle charging station having a plurality of charging points, for example six, with a single transformer. Each of the charging points is connected to a secondary winding of the transformer. The secondary windings of the transformer are able to operate independently of one another and are insulated from one another.

The charging points are thus able to be used independently of one another.

The invention also relates to a method for producing a transformer having a magnetic core having a central axis, a primary winding and a plurality of secondary windings, all of the windings being concentric about the central axis of the magnetic core, characterized in that it comprises steps of distributing the plurality of secondary windings into at least one layer of windings, of forming the at least one layer of windings such that it has one and the same number of secondary windings positioned next to one another, and of forming each secondary winding such that it has one and the same number of turns distributed over substantially the length of the magnetic core, and such that the respective distances from the secondary windings to the primary winding are within a predetermined range.

The method has advantages analogous to those presented above.

Brief description of the drawings

Other features and advantages will become apparent upon reading the following description of one preferred embodiment, given by way of non-limiting example, described with reference to the figures, in which:

[Fig. 1] shows a transformer for an electric vehicle charging station according to one embodiment of the invention,

[Fig. 2] shows a sectional view of the transformer for an electric vehicle charging station according to one embodiment of the invention,

[Fig. 3] shows a schematic sectional view of the transformer for an electric vehicle charging station according to one embodiment of the invention,

[Fig. 4] shows a method for producing the transformer for an electric vehicle charging station as shown in the previous figures, according to one embodiment of the invention.

Identical, similar or equivalent parts in the various figures bear the same reference numerals so as to make it easier to switch from one figure to another.

The various parts shown in the figures are not necessarily shown to a uniform scale so as to make the figures more legible.

Detailed description of the invention

As explained above, consideration is given by way of example to a transformer for an electric vehicle charging station. Only elements useful to understanding the invention will be described. In particular, the electric vehicle charging station is not described in its entirety.

Of course, the transformer according to the invention is able to be used for other applications.

According to one preferred embodiment shown in Figure 1, a transformer for an electric vehicle charging station according to the invention is a three-phase transformer 100.

The transformer 1 thus has three phases 1, 2 and 3 that may be seen as three coupled single phase transformers. The three phases 1, 2 and 3 have a similar architecture and have similar elements. Thus, as described hereinafter, each of the phases of the transformer has a primary winding and secondary windings about a common magnetic core 40.

The magnetic core 40 has three parallel and aligned columns (not visible in Figure 1) around which the three phases 1, 2 and 3 of the transformer are respectively formed. The three parallel columns form the three cores of the phases 1, 2 and 3. The three parallel columns are connected to one another at their ends by two connecting branches that are parallel to one another and perpendicular to the three parallel branches. Only the upper connecting branch 44 is visible in Figure 1.

Each of the phases of the transformer has a plurality 10, 20 and 30 of output terminals of the secondary windings. In the example that is shown, each phase has six output terminals. The output terminals of the secondary windings are connected respectively to electric vehicle charging points that are independent of one another.

Consideration is given hereinafter to one of the single-phase transformers.

With reference to Figure 2, the magnetic core 41 of the single-phase transformer 1 is one of the columns of the magnetic core 40. The magnetic core 41 has a central axis.

The primary winding 11 is positioned concentrically about the central axis of the magnetic core 41.

The secondary windings are positioned concentrically about the central axis of the magnetic core 41, between the magnetic core 41 and the primary winding 11. The secondary windings are distributed into at least one layer. It is possible to distribute the secondary windings over a plurality of layers that are distributed orthogonally to the central axis of the magnetic core 41. The number of layers depends on the number of secondary windings that are desired. Specifically, one and the same layer may have only a maximum number of secondary windings.

The embodiment that is shown has two layers 121 and 122.

If the number of layers is greater than or equal to 2, all of the layers of secondary windings have one and the same number X of windings, where X is an integer greater than 2. The number of windings is equal to three in the example that is shown. The layer 121 thus has the windings 1311 to 1313 and the layer 122 has the windings 1321 to 1323. In total, the single-phase transformer 1 has 6 secondary windings.

The radial distance between the layers of secondary windings is as small as possible. Thus, the distance from each secondary winding to the primary winding is within a predetermined distance range. The distance from each secondary winding to the primary winding is advantageously between 20 mm (millimetres) and 150 mm, or even between 30 mm and 100 mm, or even between 45 mm and 80 mm, in particular for a nominal voltage of the primary winding equal to 20 kV (kilovolts).

Generally speaking, the distance from each secondary winding to the primary winding is such that the value of the short-circuit voltage of each secondary winding with respect to the primary winding remains within a predetermined range. The short-circuit voltage value of a secondary winding is equal to the short-circuit voltage value of the primary winding divided by the number of secondary windings. The short-circuit voltage value of each secondary winding is advantageously greater than 1%, or even greater than 2%, or even greater than 5% of the nominal power of the transformer (taking into account a possible overload).

Given that the secondary windings are all substantially at the same distance from the primary winding, all of the secondary windings have substantially equal respective short-circuit voltages.

Each secondary winding is formed by a conductor whose turns are wound in a helix with a .o constant radius and distributed regularly over a length substantially equal to the length of the magnetic core 41. All of the secondary windings have the same number of turns distributed over the same length. All of the secondary windings cover substantially the length of the magnetic core 41, thereby allowing the ampere-turns to be balanced.

A layer, in the direction of the central axis of the magnetic core 41, has a stack of turns of the conductors forming it, alternately and in a repeating pattern.

According to one variant, the conductors of each layer are produced using CTC (continuously transposed cable) technology. In this case, a conductor is formed of a set of sub-conductors that are insulated from one another, for example with a flat or rectangular cross section, and arranged side by side. This type of conductor makes it possible to reduce electrical losses, in particular eddy current losses.

Figure 3 illustrates the alternation of the turns of the two layers in the described example. The layers are situated between the magnetic core 41 and the primary winding 11.

The layer 121 has the windings 1311 to 1313. The windings 1311 to 1313 respectively consist of conductors C1 to C3. The layer 121 has the repeating pattern C1-C2-C3 in a direction parallel to the central axis of the magnetic core 41.

Similarly, the layer 122 has the windings 1321 to 1323. The windings 1321 to 1323 respectively consist of conductors C4 to C6. The layer 122 has the repeating pattern C4-C5-C6 in a direction parallel to the central axis of the magnetic core 41.

Figure 4 shows the method for producing the transformer as described above, according to one embodiment of the invention.

As explained above, the transformer has a magnetic core having a central axis, a high-voltage primary winding and a plurality of low-voltage secondary windings. The method relates more particularly to the formation of the secondary windings.

The method comprises a step El of distributing the plurality of secondary windings into at least one layer of windings. The number of layers is chosen on the basis of the number of secondary windings that are desired.

Step El is followed by a step E2 of forming each layer such that it has one and the same number of secondary windings positioned next to one another. If the number of layers is greater than or equal to 2, the layers are within a predetermined distance range from the primary winding, and are preferably substantially at the same distance from the primary winding.

Step E2 is followed by a step E3 of forming each secondary winding such that it has one and the same number of turns distributed over substantially the length of the magnetic core. The turns of the secondary windings of one and the same layer are formed and stacked in a regular pattern in a direction parallel to the central axis of the core.

By way of example, the power range of the transformer according to the invention is from 400 kVA to 5 MVA, the voltage level of the primary circuit may range up to 36 kV and the voltage level of each secondary circuit may range up to 1 kV.

It will be understood that the term "comprise" and any of its derivatives (eg comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present disclosure restricted with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the various embodiments disclosed are capable of numerous rearrangements, modifications and substitutions without departing from the scope as set forth and defined by the following claims.

Claims

Claims

[Claim 1] Transformer having a magnetic core having a central axis, a primary winding and a plurality of secondary windings, all of the windings being concentric about the central axis of the magnetic core, characterized in that the plurality of secondary windings is distributed into at least one layer of windings, the at least one layer of windings having a predetermined number of secondary windings positioned next to one another, each secondary winding having one and the same number of turns distributed over substantially the length of the magnetic core, the respective distances from the secondary windings to the primary winding being within a predetermined range.
[Claim 2] Transformer according to Claim 1, wherein the at least one layer of secondary windings, in the direction of the central axis of the magnetic core, has a stack of turns of the secondary windings, alternating and in a repeating pattern.
[Claim 3] Transformer according to Claim 1 or 2, wherein the respective distances from the secondary windings to the primary winding are substantially equal.
[Claim 4] Transformer according to any one of Claims 1 to 3, used in an electric vehicle charging station.
[Claim 5] Electric vehicle charging station having a transformer according to any one of Claims 1 to 4.
[Claim 6] Method for producing a transformer having a magnetic core having a central axis, a primary winding and a plurality of secondary windings, all of the windings being concentric about the central axis of the magnetic core, characterized in that it comprises steps of distributing the plurality of secondary windings into at least one layer of windings, of forming the at least one layer of windings such that it has one and the same number of secondary windings positioned next to one another, and of forming each secondary winding such that it has one and the same number of turns distributed over substantially the length of the magnetic core, and such that the respective distances from the secondary windings to the primary winding are within a predetermined range.