TRANSFORMER

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to transformers, particularly three-phase transformers. More specifically, embodiments of the present disclosure relate to dry-type transformers. In particular, embodiments of the present disclosure relate to the design of leg plates for a transformer and the design of the corresponding clamping structure, particularly the clamping structure being employed as lifting structure for lifting the transformer. BACKGROUND

[0002] Transformers are found wherever electricity is generated, transported and consumed - in power plants and substations, skyscrapers and shopping malls, ships and oil platforms, locomotives and railway lines, wind parks, solar power fields and datacenters. [0003] Dry -type transformers not only increase the reliability and safety of electrical systems; they can also yield significant savings during installation and operation.

[0004] If we have a closer look at the particularities of dry transformers, the most significant aspect is the fact that they are air or resin insulated and therefore do not foresee the presence of flammable liquids. This leads to considering the dry-type solution intrinsically safer than an oil-cooled one. [0005] Furthermore, the lack of need for oil-containment works, and the fact that dry-type transformers can be located indoors and close to the load, address also positively the reduction of installation costs.

[0006] By installing the transformers indoors, it is possible to tackle also security aspects, since transformers are not exposed to vandalism or attacks, and it is also possible to maintain secrecy of the amount of installed power.

[0007] Dry -type transformers are delivered as self-contained units and do not require fluid level checks, moisture presence verification or fluid topping prior to their installation. The commissioning procedures are brought to basics, allowing a swift completion of this operation.

[0008] Important benefit from adopting dry-type technology is the fact that transformers require little or no maintenance and that in case of need, they can be repaired on the spot with ease by service experts.

[0009] In the conventional transformer design the lifting load is transferred from the upper clamp to the vertical leg plate by means of bolts or by the direct contact between the vertical leg plate-end shape and the relevant seat on the upper/bottom clamps.

[0010] The reduction of costs and the improvement of the on-time delivery of custom built dry type transformers can be addressed through a deep standardization of the components. This process involves some modification of the transformers frame structure. These include the design of the upper/bottom clamps and of the vertical leg plates.

[0011] The vertical leg plates, together with the clamps, constitute the principal path for the lifting loads. The ability to withstand such loads must be verified and each modification to the design of these parts has to be validated. Stress hot spots applied in limited regions may act as a bottle neck for the entire framework, reducing as a consequence the overall structural performance of the system.

[0012] Accordingly, it has been found that the conventional transformer design, particularly the connection between the leg plates and the upper clamp is not optimal, particularly with respect to lifting load resistance.

[0013] Hence, in view of the above, there is a demand for improved transformers, leg plates and clamping or lifting structures with improved resistance to lifting loads.

SUMMARY [0014] In light of the above, a transformer, a leg plate for a transformer and a lifting structure for a transformer according to the independent claims are provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0015] According to an aspect of the present disclosure, a transformer, particularly a dry type transformer, is provided. The transformer includes a core frame including a top clamp structure, a bottom clamp structure, and two or more core legs connected with the top clamp structure and the bottom clamp structure. A coil assembly is provided around each of the two or more core legs. Each of the two or more core legs includes a leg plate with a thickness T. The leg plate has a leg plate top portion having a leg plate top head with a width WLH and a leg plate throat with a width WLT. WLH [mm] = (ai><T ² + a2 ^x T + a ₃ ) ± 15%, where ai = 1.56 [1/mm], a ₂ = -18.1 [mm/mm], and a ₃ = 105 [mm] WLT [mm] = (bi ^x T ² + b2 ^x T + b ₃ ) ± 13%, where bi = 2.37 [1/mm], b ₂ = -30.25 [mm/mm], and b ₃ = 110 [mm]. The leg plate top portion is arranged in a mating reception of the top clamp structure.

[0016] Accordingly, compared to the state of the art, a transformer with an improved design is provided. In particular, the transformer beneficially provides for better resistance to lifting loads resulting in an extension of the operational lifting weight limit. More specifically, embodiments of the transformer as described herein beneficially provide for an optimal design with respect to stability, overall weight, and safety factor. Further, the embodiments of the transformer as described herein beneficially provide for a reduction of stress peaks such that a more uniform distribution of stress in the material can be provided. Moreover, the stiffness at the connection between the leg plates and the top clamp structure can be increased.

[0017] According to another aspect of the present disclosure, a leg plate for a transformer is provided. The leg plate has a leg plate thickness T. Further, the leg plate has a leg plate top portion including a leg plate top head with a width WLH and a leg plate throat with a width WLT. WLH [mm] = (ai><T ² + a2 ^x T + a3) ± 15%, where ai = 1.56 [1/mm], a ₂ = -18.1 [mm/mm], and a ₃ = 105 [mm] WLT [mm] = (bi ^x T ² + b2 ^x T + b ₃ ) ± 13%, where bi = 2.37 [1/mm], b ₂ = -30.25 [mm/mm], and b ₃ = 110 [mm]

[0018] Accordingly, compared to the state of the art, a leg plate with an improved design of the leg plate top portion is provided. In particular, the leg plate top portion of the leg plate as described herein beneficially provide for the possibility to be connected to mating, correspondingly shaped receptions of a top clamp structure, such that a connection of the leg plates to the top clamp structure, e.g. configured as lifting structure, with higher resistance to lifting loads can be provided.. Further, the embodiments of the leg plate as described herein beneficially provide for a reduction of stress peaks such that a more uniform distribution of stress in the material can be provided, particularly in the leg plate top portion.

[0019] According to a further aspect of the present disclosure, a lifting structure for a transformer is provided. The lifting structure includes a clamp structure and two or more lifting receptions. The clamp structure includes two or more receptions each configured for receiving a leg plate top portion of a leg plate having a thickness T. The two or more receptions have a first width Wirfor receiving a leg plate top head. Additionally, the two or more receptions have a second width WRr for receiving a leg plate throat. WRH [mm] = (ai><T ² + a2 ^x T + a3)± 15%, where ai = 1.56 [1/mm], a ₂ = -18.1 [mm/mm], and a ₃ = 105 [mm] W _RT [mm] = (bi ^x T ² + b2 ^x T + b ₃ ) ± 13%, where bi = 2.37 [1/mm], b ₂ = -

30.25 [mm/mm], and b ₃ = 110 [mm]

[0020] Accordingly, compared to the state of the art, a lifting structure with an improved design of the receptions for leg plate top portions is provided. In particular, the receptions for the leg plate top portions beneficially provide for the possibility to be connected to mating, correspondingly shaped leg plate top portions of a leg plate, such that a connection of the leg plates to the lifting structure with higher resistance to lifting loads can be provided.. Further, the embodiments of the leg plate as described herein beneficially provide for a reduction of stress peaks such that a more uniform distribution of stress in the material can be provided, particularly in the leg plate top portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

Fig. 1 shows a schematic view of a transformer according to embodiments described herein;

Fig. 2a shows a schematic view of a leg plate top portion of a leg plate according to embodiments described herein; Fig. 2b is a side view of the leg plate top portion shown in Fig. 2a for illustrating thickness of the leg plate;

Fig. 3a shows a schematic view of a lifting structure according to embodiments described herein; and Fig. 3b shows a schematic view of a lifting structure according to further embodiments described herein with an alternative configuration of the lifting reception.

DETAILED DESCRIPTION OF EMBODIMENTS

[0022] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations.

[0023] Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment can apply to a corresponding part or aspect in another embodiment as well.

[0024] With exemplary reference to Figs. 1, 2a, 2b, 3a and 3b, a transformer 10, a leg plate 20, and a lifting structure 30 according to embodiments of the present disclosure are described. In particular, the transformer 10 can be a dry type transformer [0025] According to embodiments, which can be combined with other embodiments described herein, the transformer includes a core frame 15 including a top clamp structure 16, a bottom clamp structure 17, and two or more core legs connected with the top clamp structure 16 and the bottom clamp structure 17, as exemplarily shown in Fig. 1. Fig. 1 shows an exemplary embodiment with three core legs, namely a first core leg 11, a second core leg 12, and a third core leg 13. As exemplarily shown in Fig. 1, a coil assembly 14 is provided around each of the two or more core legs. Accordingly, the transformer 10 can be a three-phase transformer.

[0026] As exemplarily shown in Fig. 1, each of the two or more core legs include a leg plate 20 with a thickness T (indicated in Fig. 2b). The leg plate 20 has a leg plate top portion 20T having a leg plate top head 21 with a width WLH and a leg plate throat 22 with a width WLT, as shown in Fig. 2a. The width WLH of the leg plate top head 21 configured according to the equation WLH [mm] = (ai><T ² + a2 ^x T + a ₃ ) ± 15%, where ai = 1.56 [1/mm], a ₂ = -18.1 [mm/mm], and a ₃ = 105 [mm]. The width WLT of the leg plate throat 22 is configured according to the equation wherein WLT [mm] = (bi ^x T ² + b2 ^x T + b ₃ ) ± 13%, where bi = 2.37 [1/mm], b ₂ = -30.25 [mm/mm], and b ₃ = 110 [mm]. As exemplarily shown in Fig. 1, the leg plate top portion 20T is arranged in a mating reception 18 of the top clamp structure 16.

[0027] With exemplary reference to Fig. 2a, according to embodiments, which can be combined with other embodiments described herein, the leg plate top portion 20T includes a first inclined section 212 with a first wedge angle ai = 60°±15° between the leg plate top head 21 and the leg plate throat 22.

[0028] According to embodiments, which can be combined with other embodiments described herein, the leg plate top portion 20T includes a second inclined section 223 with a second wedge angle 012= 60°±15° between the leg plate throat 22 and a leg plate main body 23, as exemplarily shown in Fig. 2a. A first wedge angle on and/or a second wedge angle on as described herein beneficially generates a horizontal force component acting on the top clamp structure with improved force balance. [0029] With exemplary reference to Fig. 2a, according to embodiments, which can be combined with other embodiments described herein, the leg plate 20 is symmetric with respect to a symmetry plane 24 extending in longitudinal direction of the leg plate 20.

[0030] According to embodiments, which can be combined with other embodiments described herein, the width WL of the leg plate main body 23 is equal to the width WLH of the leg plate top head 21, as exemplarily shown in Fig. 2a.

[0031] With exemplary reference to Fig. 2a, according to embodiments, which can be combined with other embodiments described herein, the top clamp structure 16 of the transformer includes two or more lifting receptions 34 configured for receiving a lifting tool, particularly a lifting hook.

[0032] With exemplarily reference to Figs. 2a and 2b, a leg plate 20 for a transformer 10 according to the present disclosure is described. According to embodiments, which can be combined with other embodiments described herein, the leg plate 20 has a leg plate thickness T, as exemplarily shown in Fig. 2b. As shown in Fig. 2a, the leg plate 20 has a leg plate top portion 20T including a leg plate top head 21 with a width WLH and a leg plate throat 22 with a width WLT. The width WLH of the leg plate top head 21 is configured according to the equation WLH [mm] = (ai><T ² + a2 ^x T + a ₃ ) ± 15%, where ai = 1.56 [1/mm], a ₂ = -18.1 [mm/mm], and a ₃ = 105 [mm]. The width WLT of the leg plate throat is configured according to the equation WLT [mm] = (bi ^x T ² + b2 ^x T + b ₃ ) ± 13%, where bi = 2.37 [1/mm], b ₂ = -30.25 [mm/mm], and b ₃ = 110 [mm]

[0033] With exemplary reference to Fig. 2a, according to embodiments, which can be combined with other embodiments described herein, the leg plate top portion 20T includes a first inclined section 212 having a first wedge angle ai = 60°±15° between the leg plate top head 21 and the leg plate throat 22. Additionally or alternatively, the leg plate top portion 20T includes a second inclined section 223 having a second wedge angle 012 60°±15° between the leg plate throat 22 and a leg plate main body 23. A first wedge angle on and/or a second wedge angle on as described herein beneficially generates a horizontal force component acting on the top clamp structure with improved force balance.

[0034] According to embodiments, which can be combined with other embodiments described herein, the leg plate 20 is symmetric with respect to a symmetry plane 24 extending in longitudinal direction of the leg plate 20, as exemplarily shown in Fig. 2a. [0035] With exemplary reference to Fig. 2a, according to embodiments, which can be combined with other embodiments described herein, a width WL of the leg plate main body 23 is equal to the width WLH of the leg plate top head 21.

[0036] With exemplary reference to Figs. 3a and 3b, lifting structure 30 for a transformer according to the present disclosure is described. According to embodiments, which can be combined with other embodiments described herein, the lifting structure 30 includes a clamp structure 35 and two or more lifting receptions 34. For example, the two or more lifting receptions 34 can be configured as lifting lugs or eye bolts as exemplary shown in Fig. 3a. Alternatively, the two or more lifting receptions 34 can be integrated in the clamp structure 25, for instance as integrated holes as exemplary shown in Fig. 3b. However, it is to be understood, that the clamp structure 35 may be provided with any other suitable lifting construction not explicitly shown in the figures. [0037] As exemplarily shown in Figs. 3a and 3b, the clamp structure 35 includes two or more receptions each configured for receiving a leg plate top portion 20T of a leg plate 20 having a thickness T. In particular, Figs. 3 a and 3b show an example having three receptions, namely a first reception 31, a second reception 32 and a third reception 33. The two or more receptions 31, 32, 33 have a first width WRH for receiving a leg plate top head 21 and a second width WRT for receiving a leg plate throat 22. The first width WRH is configured according to the equation WRH [mm] = (ai><T ² + a2 ^x T + a ₃ ) ± 15%, where ai = 1.56 [1/mm], a2 = -18.1 [mm/mm], and a ₃ = 105 [mm]. The second width WRT is configured according to the equation WRT [mm] = (bi ^x T ² + b2 ^x T + b ₃ ) ± 13%, where bi = 2.37 [1/mm], l½ = -30.25 [mm/mm], and b3 = 110 [mm]. In this regard, it is to be understood that a fit tolerance is provided between the two or more receptions 31, 32, 33 and the respective leg plate top portion 20T.

[0038] With exemplary reference to Figs, 3a and 3b, according to embodiments, which can be combined with other embodiments described herein, the two or more receptions 31, 32, 33 include a first transition portion 311 which is inclined by a first angle bi = 60°±15° with respect to a central axis 36 of each two or more receptions 31, 32, 33. Additionally or alternatively, the two or more receptions 31, 32, 33 include a second transition portion 312 which is inclined by a second angle b2 = 60°±15° with respect to the central axis 36 of each two or more receptions 31, 32, 33. As shown in Figs. 3a and 3b, the first transition portion 311 is from the first width WR to the second width WRT and the second transition is from the second width WRT to the first width WR.

[0039] A first angle bi of the first transition portion and/or a second angle b2 of the second transition portion as described herein beneficially provides for receiving a horizontal force components from the leg plates such that an improved force balance can be provided.

[0040] According to embodiments, which can be combined with other embodiments described herein, each of the two or more receptions 31, 32, 33 is symmetric with respect to a plane extending along the respective central axis 36 of the respective two or more receptions 31, 32, 33. [0041] Accordingly, in view of the above, it is to be understood that embodiments described herein beneficially provide for provide for an optimal design with respect to stability, overall weight, and safety factor.

[0042] In particular, embodiments described herein beneficially provide for better resistance to lifting loads resulting in an extension of the operational lifting weight limit. Further, embodiments described herein beneficially provide for reducing or even avoiding stress peaks, particularly at the connections between leg plates and the top clamp structure. For instance, a wedge-shaped design as described herein provides for a reduction of stress peaks such that a more uniform stress distribution and a higher safety margin for a given weight can be provided. Accordingly, performance of the entire core frame can be enhanced.

[0043] While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope is determined by the claims that follow.

REFERENCE NUMBERS

10 transformer

11 first core leg

12 second core leg

13 third core leg

14 coil assembly

15 core frame

16 top clamp structure

17 bottom clamp structure

18 mating reception of top clamp structure for leg plate top portion

20 leg plate

20T leg plate top portion 20B leg plate bottom

21 leg plate top head

212 first inclined section between leg plate top head and leg plate throat

22 leg plate throat

223 second inclined section between leg plate throat and leg plate main body

23 leg plate main body

24 symmetry plane

30 lifting structure

31 first reception

311 first transition portion

312 second transition portion

32 second reception

33 third reception

34 lifting reception (lifting lug / eye bolt/ integrated hole in top clamp structure)

35 clamp structure

36 central axis of reception ai first wedge angle

(*2 second wedge angle W _L width of leg plate W _LT width of leg plate throat W _LH width of leg plate top head T thickness of leg plate

W _RH first width of reception for leg plate top head

W _RT second width of reception for leg plate throat