EP2709124B1 - Transformator - Google Patents

Description

The invention relates to a transformer having the features of patent claim 1.

An example of a transformer is in the patent US-A-2010103585 described.

It is well known that transformers are used in electrical power distribution networks to couple power supplies of different voltage levels together. Such transformers are often designed as dry transformers in a consumer or near-generator voltage level and have, for example rated voltages in the range of 1 kV to 6kV on the low side and rated voltages in the range of 10kV to 30kV on the upper side, with corresponding power ratings in the range of, for example, 0.5 MVA to 10 MVA lie. But also in the field of wind turbines find such transformers application, in which case the rated power of a transformer depends on the performance of an associated wind turbine. Due to the high rated currents in the low voltage range, which may be for example a few 100A, the low-voltage windings are often designed wound from a strip conductor, the width of a strip conductor usually corresponds to the complete axial length of a respective transformer winding. Depending on the embodiment and requirements of the transformer, the number of undervoltage-side windings, for example, in the range of ten turns, in particular also in applications for wind turbines, where the generator generated voltage is correspondingly low and is set by the transformer to a higher operating level.

For control purposes, it is a known procedure, preferably the upper-voltage side (s) winding (s) of a transformer to provide a plurality of taps, which can be selected for example by means of a respective tap changer, so that the transmission ratio of the transformer is thus variable in a control range. An increased controllability is required in applications for wind turbines to ensure an adaptation of the transformer to the conditions resulting from different wind conditions boundary conditions.

The active part of a transformer has a closed iron circuit and at least one upper and lower voltage winding with integer, closed turns around the respective core leg. The induced voltage per closed conductor loop depends on the mains frequency, flux density and core cross section.

The disadvantage is, on the one hand, that a high-voltage side arranged tap changer is very complex to manufacture due to the high voltage stress and that the regulation of the voltage can be minimal in that voltage grading, which corresponds to the induced voltage of a complete turn. With voltage regulation, the minimum control level is therefore limited to the voltage difference between two turns. This is particularly disadvantageous in the aforementioned undervoltage band windings, because due to the relatively low total number of turns, for example in the range of ten, a fine control in the range of, for example, +/- 15% in, for example, 1.5% steps around the nominal ratio not possible.

Based on this prior art, it is an object of the invention to provide a transformer, which allows the voltage side in lower voltage steps on the voltage side, wherein a corresponding Tap changer is easier to manufacture due to the then lower voltage stress.

This object is achieved by a transformer of the aforementioned type. This is characterized in that the cross section of the core leg and / or a trained core yoke of the transformer core has at least two areas separated transversely from each other in a cross-sectional plane imagined transversely to their respective extension, and that at least a turn of the respective additional winding is guided through the opening

The basic idea of the invention is to reduce the induced voltage of a complete turn, which is intended for control purposes, by not enclosing the cross section of the complete core leg or of a core yoke of the transformer core, but only a part of the cross section. As a result, only part of the flow through the core limb or through the core yoke is encompassed and the tension induced in such a turn is correspondingly reduced. For this purpose, the invention provides that the core leg cross-section or the core yoke cross-section have at least two regions in a cross-sectional plane which is transversal to their respective extent, which are separated from one another by an opening. The extension is to be understood in the longitudinal direction of a respective leg or yoke section. The angle at which a breakthrough occurs within the cross-sectional plane is fundamentally insignificant; the production-related boundary conditions are decisive. This breakthrough makes it possible to pass one or more turns of the additional winding through, whereby the voltage swing of the respective turn is reduced. As a result, a finer gradation of the voltage of the auxiliary winding is achieved in an advantageous manner.

A breakthrough can be realized for example by means of a bore, which is guided by the core leg or the core yoke. In the case of a layered transformer core, a channel-like opening for a roundish conductor, for example, can also be created by means of corresponding recesses in a sheet-metal layer area. According to a further embodiment of the invention, the opening is designed as a gap, which extends along the core leg extends. Such a gap can be implemented particularly easily, depending on the transformer core type.

Of course, it is also possible to provide a correspondingly higher number of columns and thus also on cross-sectional areas. The subdivision can be arbitrary in principle to meet the requirements of controllability, z. B. 1/3, or 1/4. Specific voltage levels can also be realized by placing several turns around a part of the leg, for example 3 turns around 1/4 of the core leg cross section, 4 turns around 1/5 of the core leg cross section or 9 turns around 1/10 of the core leg cross section. If the windings are placed separately around a part of the core leg cross-section, the wiring can be used by the choice of the winding sense or the polarity of the (additional) winding in order to make it appear either additive or subtractive. This makes it possible to reduce the number of (additional) turns required for the voltage controllability.

This will be explained using the example of 4 (additional) turns to 1/5 of the core leg cross-section. Without polarity change results in an adjustable number of turns of: 1, = 1 1 + 1/5 = 1.2, 1 + 2/5 = 1.4, 1 + 3/5 = 1.6, 1 + 4/5 = 1.8, 2 = 2.

For a wider control range, it is advisable to use taps of turns of the additional winding, which enclose the entire core leg cross-section. Thus, the windings guided through a respective gap are ultimately used exclusively for the fine control stages.

With polarity change results in 2 (additional) turns by 1/5 of the core leg cross-section, taking into account a polarity change the following example: 1, = 1, 1 + 1/5 = 1.2, 1 + 2/5 = 1.4, 2 - 2/5 = 1.6, 2 - 1/5 = 1.8, 2 = 2.

However, it is also possible to provide at the same time (additional) windings which enclose different sized parts of the core leg cross section, e.g. 1/2 and 1/4. For example, the stress can be regulated in +/- 25% steps of the full turn tension by dividing the core leg cross-sectional area into three areas whose contents are 50%, 25% and 25% of the total cross-sectional area. This achieves +/- 25%, +/- 50% and +/- 75% full turn steps.

According to a particularly preferred embodiment of the transformer according to the invention, at least the additional winding is formed by a ribbon conductor, but ideally also the main winding. A ribbon cable is due to its high filling factor in a special way for a low-voltage transformer winding, where at relatively low rated voltages in the range of, for example, some 100V to over 1 kV is expected to correspondingly high currents, which may well exceed 1000 A. In addition, a ribbon conductor manufacturing technology is also particularly easy to guide through a gap according to the invention, which separates two core leg portions from each other. Typically, such a ribbon conductor has a width which corresponds to the total axial height of the respective winding, so that a conductor layer in each case comprises exactly one turn.

For safe electrical insulation of the guided through the gap winding conductor, it is inventively provided that this is surrounded at least in the region of the gap of an additional layer of an electrical insulation material. The gap is formed by the typically grounded transformer core and therefore isolation technology of particular importance, especially because - depending on the current interconnection of the auxiliary winding - in the guided through the gap winding (s) and the full nominal voltage can be applied. Optionally, however, it is also possible to surround the gap walls with an additional layer of insulating material.

According to a particularly preferred embodiment of the transformer according to the invention, the additional winding is provided with several accessing to different turns taps. Ideally, the auxiliary winding has a fine graduation region which is characterized by taps of turns of the additional winding guided through the respective gap of a core limb. These each have an induced voltage, which is lower than the induced voltage of the respective core leg completely comprehensive turn. In addition, a coarse graduation range can be provided, which is characterized by taps of the core legs in each case completely comprehensive turns. By appropriate series connection of the coarse and the fine grading range, a fine gradation can be achieved over a wide range.

According to a further inventive variant of the transformer switching means are provided to selectively connect the main winding with one of the taps of the auxiliary winding, so that the number of active turns of the electrically connected main and auxiliary winding is thus adaptable. Optionally, separate switching means are provided for coarse and fine grading range of the auxiliary winding.

According to a further embodiment of the transformer, the switching means comprise a tap changer and / or power electronic components. Tap changers have proved their worth for the selective selection and connection of taps of a transformer winding as a standard component. If required, power electronic components such as thyristors or IGBTs are also provided.

In principle, the invention can be applied to any type of transformer core, in particular to three-core cores, five-limbed cores or even a transformer with a triangular plan. These may for example be layered or wound. However, some special embodiments are to be presented in more detail below.

According to a further variant of the transformer according to the invention, the transformer core is formed from a rectangular-like outer core ring disk and at least two rectangular-shaped inner core ring disks enclosed by the latter, wherein a respective gap is formed in the leg region between adjoining sections of the core ring disks. The basic structure of such a transformer core corresponds - apart from the respective columns - in principle, the construction of an Evans transformer core. The core ring discs are preferably made of each wound strip material. In addition to standard transformer sheet can be used for this example, amorphous strip material. Of course, however, a layering of the sheet-like core material is possible.

A further variant of the transformer according to the invention is characterized in that the transformer core is formed from three rectangular-shaped core ring disks arranged in a triangle, wherein a respective gap is formed in the leg region between adjoining sections of the core ring disks. Again, it is possible to wrap a core ring disc either from a band-like material or even to layer a sheet-like material.

According to a further embodiment of the transformer according to the invention, the transformer core is a toroidal core, by which the at least one core leg is formed. The entire toroidal core is then to be regarded as a bent transformer core leg, at least two toroidal core modules being provided to form the gap running along the toroidal core according to the invention.

According to a further embodiment of the transformer according to the invention, a further winding which is galvanically separated therefrom is arranged radially around the main winding. Here, the main winding is on the low side and the other winding is connected on the high side. By the ratio of the respective active upper and lower side windings to each other, the transmission ratio of the transformer is determined. This is carried out in accordance with a further embodiment, three-phase. This is particularly useful when used in an energy distribution network.

According to a further embodiment of the invention, the main winding arranged around a transformer core leg is electrically connected in series with an additional winding which is arranged around the same core leg. As a result, the phase position of the induced voltage in the additional winding of the phase position of the induced voltage in the main winding, or it is offset with appropriate interconnection with polarity change by 180 ° and in phase opposition. As a result, a longitudinal regulation of the voltage is achieved.

According to a further embodiment, the main winding arranged around a transformer core leg is electrically connected in series with an additional winding which is arranged around an adjacent transformer core leg. Thus, in a three-phase transformer, a phase shift of 120 ° or 240 ° results between the voltage induced in the main winding and the auxiliary winding. With a corresponding interconnection with polarity change, an oblique control with a 60 ° angle can be realized.

Further advantageous embodiment possibilities can be found in the further dependent claims.

Reference to the embodiments illustrated in the drawings, the invention, further embodiments and other advantages will be described in detail.

Fig. 1

einen exemplarischer Querschnitt eines ersten Kernschenkels,

Fig. 2

einen exemplarischer Querschnitt eines zweiten Kernschenkels,

Fig. 3

einen exemplarischen ersten Transformatorkern,

Fig. 4

einen exemplarischen zweiten Transformatorkern,

Fig. 5

einen exemplarischen Transformator sowie

Fig. 6

eine exemplarische Reihenschaltung von Haupt- und Zusatzwicklung.

Show it:

Fig. 1

an exemplary cross section of a first core leg,

Fig. 2

an exemplary cross section of a second core leg,

Fig. 3

an exemplary first transformer core,

Fig. 4

an exemplary second transformer core,

Fig. 5

an exemplary transformer as well

Fig. 6

an exemplary series connection of main and auxiliary winding.

Fig. 1 shows an exemplary cross section of a first core leg 10, which is formed by two similar core leg modules each having the same cross-sectional areas 12, 14, wherein between a gap 16 is formed, which separates the cross-sectional areas 12 and 14 from each other. Around the first cross-sectional area 12, which constitutes 50% of the total cross-sectional area of the core leg 10, two exemplary windings 18, 20 of a ribbon conductor are arranged, which are guided through the gap 16 and form part of an exemplary additional winding. Accordingly, since each of the two windings embraces only 50% of the total core leg cross-section, the voltage induced during operation in a respective winding is only 50% of the voltage of a conductor which encompasses the entire core leg cross-section. In this way, a finer voltage gradation of the taps is realized, which are identified by the reference numerals 22 and 24. These are intended to be connected to a tap changer, not shown, which in turn is connected to a main winding, not shown.

Fig. 2 shows an exemplary cross section of a second core leg 30, which is formed by two core leg modules, the cross-sectional areas 32 and 34 are divided approximately in the ratio 1: 3. The first cross-sectional region 32, which makes up about 25% of the total core leg cross-sectional area, is encompassed by a first winding 38 of an additional winding guided through a gap 36, a second winding 40 of the additional winding embracing the entire core leg cross-section. Accordingly, the magnitude of the voltage induced in operation in the first winding 38 is 25% of the voltage induced in operation in the second winding 40. In this way, a finer voltage gradation of the taps is realized which are indicated by the reference numerals 42 and 44. These are intended to be connected to a tap changer, not shown, which in turn is connected to a main winding, not shown.

Fig. 3 shows an exemplary first transformer core 50 in a sectional view. A rectangular-like outer core ring disk 52, for example, with a width of 2m and a height of 1.5m, encloses two also rectangular-like inner core ring disks 54, 56, so that a transformer core with three core legs 64 is formed, each core leg 64 in turn is formed from two adjacent leg portions of respective core ring discs. Between the leg portions, a respective gap 58 is formed, which is provided so that one or more winding conductors of a radially inwardly arranged around the respective core leg and not shown additional winding are passed through this. Such a gap 58 can be realized very simply in that the sum of the outer widths of the inner core ring disks is smaller than the inner width of the outer core ring disk encompassing them. Kernringscheiben can be made for example of wound strip material or even from layered sheet metal.

Fig. 4 shows an exemplary second transformer core 70 in a sectional view top view. Three rectangular-like core ring disks 72, 74, 76 are disposed adjacent in an equilateral triangle with adjacent leg portions forming a respective core leg 78, 80 with a respective gap 82 therebetween. Around one of the two leg portions of a core leg 78, 80 and through an intermediate gap is passed an exemplary first turn 84 of an auxiliary winding which encompasses 50% of the cross sectional area of the corresponding core leg and into which a correspondingly reduced voltage is induced during operation. A second exemplary turn 86 of the auxiliary winding encompasses the entire cross-sectional area of the same core leg. The additional winding is connectable by means of the terminals 88, 90, for example, with a tap changer, not shown, a main winding, not shown.

Fig. 5 shows an exemplary transformer 100, which is designed as a toroidal transformer. The ring-like transformer core has a ring-like radially outer first part 102 and a ring-like radially inner part 104, wherein a gap is formed therebetween. Of course, it is also possible to form the transformer core not exactly circular, but also, for example, polygonal. Two exemplary main windings 106a, b and two exemplary auxiliary windings 108a, b are provided along the ring-like extension of the transformer core and encompassing it, which are connected to a low-side winding, as not shown. The additional windings 108a, b encompass only a portion of the core cross-section and it is induced during operation, a correspondingly lower voltage per turn. In combination with corresponding taps and with, for example, a tap changer results in a fine-level control option of the low-voltage winding. Also arranged on the ring core are two further galvanically isolated windings 107a, b, which are connected to a high-voltage winding.

Fig. 6 1 shows an exemplary series connection of a main winding 112 and an additional winding 114 to a low-side winding with respective terminals 120, 122. The auxiliary winding has a plurality of taps 116, wherein between adjacent taps in each case a winding guided according to the invention through a gap of an associated transformer core not shown, which encompasses, for example, in each case 1/6 of a respective core leg cross-section. A tap changer 118 is provided to make electrical contact with a respectively selected tap 116 and to make a series connection of main winding 112 to the corresponding part of the auxiliary winding 114.

LIST OF REFERENCE NUMBERS

10

exemplary cross section of a first core leg

12

first region of the cross section of the first core limb

14

second region of the cross section of the first core limb

16

first gap

18

first turn of the additional winding around the first core leg

20

second turn of the additional winding around the first core leg

22

first tapping of the additional winding around the first core leg

24

second tapping of the additional winding around first core legs

30

exemplary cross section of a second core leg

32

first region of the cross section of the second core limb

34

second region of the cross section of the second core leg

36

second gap

38

first turn of the additional winding around the second core leg

40

second turn of the additional winding around the second core leg

42

first tapping of the additional winding around the second core leg

44

second tap of the additional winding around the second core leg

50

exemplary first transformer core

52

outer core ring disk

54

first inner core ring disk

56

second inner core ring disk

58

third gap

60

fourth gap

62

hollow cylinder-like winding area

64

third core leg

70

exemplary second transformer core

72

first core ring disk

74

second core ring disk

76

third core ring disk

78

fourth core thigh

80

fifth core leg

82

fifth gap

84

first turn of the auxiliary winding

86

second winding of additional winding

88

first connection of additional winding

90

second connection of additional winding

100

exemplary transformer

102

first part of the transformer core

104

second part of the transformer core

106a, b

main winding

107a, b

galvanically separated further winding

108a, b

auxiliary winding

110

exemplary series connection of main and auxiliary winding

112

main winding

114

auxiliary winding

116

taps

118

step switch

120

first connection

122

second connection

Claims (14)

1. Transformer, comprising a transformer core (50, 70) having at least one core limb (10, 30, 64, 78, 80, 102 + 104) and a main winding (106a,b, 112), which is arranged around the respective core limb (10, 30, 64, 78, 80, 102 + 104) in a hollow-cylinder-like winding region (62), and an auxiliary winding (108a,b, 114), which is arranged close to the core and is electrically connected to said main winding,
   characterized in that
   the cross section of the core limb (10, 30, 64, 78, 80, 102 + 104) and/or of a core yoke formed of the transformer core (50, 70) has at least two regions (12, 14, 32, 34) separated by an aperture in a cross-sectional plane which is imaginary transverse to the respective extent of said core limb and said core yoke, and in that at least one turn (18, 20, 38, 40, 84, 86) of the respective auxiliary winding (108a,b, 114) is passed through the aperture.
2. Transformer according to Claim 1, characterized in that the aperture is a gap which extends along the core limb (10, 30, 64, 78, 80, 102 + 104).
3. Transformer according to Claim 2, characterized in that at least the auxiliary winding (108a,b, 114) is formed by a flat ribbon conductor.
4. Transformer according to Claim 3, characterized in that the flat ribbon conductor is surrounded, at least in the region of the aperture (16, 36, 58, 60, 82), by an additional layer consisting of an electrical insulation material.
5. Transformer according to one of the preceding claims, characterized in that the auxiliary winding (108a,b, 114) is provided with a plurality of taps (22, 24, 42, 44, 116) on different turns (18, 20, 38, 40, 84, 86) of the auxiliary winding (108a,b, 114).
6. Transformer according to Claim 4, characterized in that switching means are provided in order to connect the main winding optionally to one of the taps (22, 24, 42, 44, 116), with the result that the number of active turns of the main winding (106a,b, 112) and auxiliary winding (108a,b, 114), which are electrically connected, can be adapted thereto.
7. Transformer according to Claim 6, characterized in that the switching means comprise an on-load tap changer (118) and/or power electronics components.
8. Transformer according to one of the preceding claims, characterized in that the transformer core (50, 70) is formed from a rectangle-like outer core ring disc (52) and at least two rectangle-like inner core ring discs (54, 56) surrounded thereby, wherein a respective gap (16, 36, 58, 60, 82) is formed in the limb region between adjoining sections of the core ring discs (52, 54, 56).
9. Transformer according to one of Claims 1 to 7, characterized in that the transformer core (50, 70) is formed from three rectangle-like core ring discs (72, 74, 76) arranged in a triangle, wherein a respective gap (16, 36, 58, 60, 82) is formed in the limb region between adjoining sections of the core ring discs (72, 74, 76).
10. Transformer according to one of Claims 1 to 7, characterized in that the transformer core (50, 70) is a toroidal core, by means of which the at least one core limb (10, 30, 64, 78, 80, 102 + 104) is formed.
11. Transformer according to one of the preceding claims, characterized in that a galvanically isolated further winding (107a,b) is arranged radially around the main winding (106a,b, 112).
12. Transformer according to Claim 11, characterized in that said transformer has a three-phase embodiment.
13. Transformer according to Claim 12, characterized in that the main winding (106a,b, 112), which is arranged around a transformer core limb (10, 30, 64, 78, 80), is connected electrically in series with an auxiliary winding (108a,b, 114), which is arranged around the same core limb (10, 30, 64, 78, 80, 102 + 104).
14. Transformer according to Claim 12, characterized in that the main winding (106, 112), which is arranged around a transformer core limb (10, 30, 64, 78, 80, 102 + 104), is connected electrically in series with an auxiliary winding (106a,b, 114), which is arranged around an adjacent transformer core limb (10, 30, 64, 78, 80, 102 + 104).

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