EP4593053A1

EP4593053A1 - An on-load tap changer

Info

Publication number: EP4593053A1
Application number: EP24154117.6A
Authority: EP
Inventors: Jean Louis Gérard Mathae; Thomas Eriksson; Daniel FORSMAN; Stefan Hortlund; Magnus SVANBERG
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2024-01-26
Filing date: 2024-01-26
Publication date: 2025-07-30
Also published as: WO2025157680A1

Abstract

An on-load tap changer (OLTC) (1) comprising a housing, said housing comprising a housing body (4) having open end portions (6, 7) closed by a respective cover assembly (2, 3) attached to the housing body (4) by adhesive between the housing body (4) and a respective flange of each respective cover assembly (6, 7).

Description

TECHNICAL FIELD

The present invention relates to an on-load tap changer (OLTC) designed for use in moving working conditions, such as at sea.

BACKGROUND OF THE INVENTION

On-load tap changers (OLTCs) typically comprise a housing formed by a housing body having opposite open ends, each end being closed by a respective cover assembly attached to the housing body using any suitable fastening means, such as mechanical fasteners or threads. The housing body may be made from a rigid material, such as a fiber-reinforced plastic material. When the OLTC is exerted to accelerations, the fittings tend to wear at the respective junction between fitting and housing body, such that the risk of failure increases. For static installations this is not a problem, but when using the OLTC in moving applications, for example on a floating platform at sea, the problem tends to increase.
Accordingly, it is an object of the invention to make the OLTC more robust.

SUMMARY OF THE INVENTION

According to a first aspect, the object is achieved by an OLTC according to claim 1, with alternative embodiment defined in the dependent claims. The OLTC comprises a housing, said housing comprising a housing body extending along a longitudinal axis, said housing body comprising an inner cavity, a first open end portion and an opposite second open end portion. The housing further comprises a first cover assembly for closing the first open end portion, and a second cover assembly for closing the second open end portion.
The first cover assembly comprises a first flange member attached to the housing body at the first open end portion of the housing body with a first flange of the first flange member extending along the longitudinal axis either into the inner cavity along an inside surface of the housing body, or along an outer surface of the housing body. The first flange member is attached to the housing body by adhesive.
The second cover assembly comprises a second flange member attached to the housing body at the second open end portion of the housing body with a second flange of the second flange member extending along the longitudinal axis, either into the inner cavity along an inside surface of the housing body or along the outer surface of the housing body. The second flange member is attached to the housing body by adhesive.
The housing body is made of a fibre-composite material, and the first and second flange members are made of metal.
The fiber-composite housing body is robust and does not corrode when used at sea. A suitable material is fiberglass reinforced plastics, for example reinforced with epoxy or any other suitable resin.
The metal material of the first and second cover assemblies is easy to manufacture and provides similar material properties in all directions of applied force, and hence enables variations as to the requirements of each specific OLTC model produced by simply varying one or more members of the respective cover assembly.
The first and second flange members comprise a respective flange enabling increased surface area in an interface between the housing body and the respective flange member, which in turn enables a strong adhesive bond with reduces local stress on the bond. Also, the flange ensures correct relative positioning of the respective cover assembly with respect to the housing body both during manufacturing, i.e. as the adhesive sets or cures, and after assembly during transport and use of the OLTC. The separation of each cover member into a flange member and a cover member enables access to the inner space of the OLTC by removal of the cover member, and
The respective flange may be sized to press-fit with the housing body when attached to the housing body.
The press-fit adds friction between the housing body and the respective flange member, thereby enabling direct force transmission between the housing body and the respective flange member, without relying solely on force transfer through the adhesive. This makes the OLTC more robust. Also, the press-fit holds the flange member still with respect to the housing as the adhesive sets or cures, and after assembly during transport and use of the OLTC.
The press-fit may be such that press-fit is present at least within a temperature range of -40 to +100 degrees Centigrade.
Size of various components of the OLTC change size in response to temperature variations if they are made from materials with different thermal expansion coefficients. As such, the press-fit at a first temperature may not present when temperature rises or falls. By providing enough pre-fit, the press fit will be present throughout the whole intended temperature range of use of the OLTC, which in this case comprises the range of -40 to +100 degrees centigrade. Typically, a metal, such as steel, has a smaller thermal expansion coefficient than fibreglass reinforced plastic. For fibreglass reinforced plastic, the fibre layup or winding directions also affects the thermal expansion coefficient such that it varies in different directions.
At least one of said first and second flange members may comprise:

a central opening enabling access into the inner cavity of the housing body through the central opening, and
a respective cover member attachable to the respective flange member using mechanical fasteners, threaded connection or an adhesive, said cover member being adapted to cover the respective central opening.

The central opening enabled electrical components of the OLTC to be moved into and out of the OLTC, such as for service of repair, and the cover member, which may include some of the electrical components, may be attached to the flange member to close the respective central opening to thereby close the housing before use of the OLTC.
The at least one cover member may be attached to the flange member using mechanical fasteners, and a sealing member or sealant may be provided between the flange member and the cover member for providing a gas tight seal between the flange member and the respective cover member.
Mechanical fasteners provide a simple and robust means for holding the cover member to the flange member. The sealing member or sealant may be provided to protect inner components of the OLTC.
The mechanical fasteners may be removable fasteners, such as screws.
The removability of the fasteners enables easier service and repair of the OLTC.
The adhesive may be an epoxy adhesive.
Epoxy is a strong adhesive which adheres well to both metal and fibreglass reinforced plastic.
The first and second flange may be provided with one or more recesses facing the housing body or provided with one or more structured surface portions facing the housing body, wherein the adhesive is applied at said one or more recesses or structured surface portions.
The uneven surface structure provided by the recesses or structured surface portions provide an increased adhesion surface area for the adhesive and thus improves strength of the adhesive bond between the housing body and the respective flange member.
The housing body may be cylindrical.
The cylindrical housing is strong and deforms uniformly upon expansion and contraction due to temperature changes, and thus provides for a more reliable bond between the housing body and each respective flange member.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a cross-sectional side view of relevant components of a first embodiment of an OLTC, in cross-section A-A indicated in fig. 5. The first and second cover assemblies comprise components schematically shown using dashed lines (not illustrated in other figures).
Fig. 2 shows a top perspective view of the OLTC also shown in fig. 1, however without showing the first cover assembly and the second cover assembly.
Fig. 3 shows a side view of the OLTC also shown in fig. 2.
Fig. 4 shows a bottom perspective view of the OLTC also shown in figs. 2 and 3.
Fig. 5 shows a top view of the OLTC also shown in figs. 2, 3 and 4.
Fig. 6 shows an enlarged view of detail B indicated in fig. 1.
Fig. 7 shows an enlarged view of detail C indicated in fig. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the invention will hereinafter be described with reference to the appended drawings.
As shown in fig 1, an on-load tap changer (OLTC) 1 according to a first embodiment comprises a housing, said housing comprising a housing body 4 extending along a longitudinal axis L. The housing body 4 comprises an inner cavity 5, a first open end portion 6 and an opposite second open end portion 7. The housing further comprises a first cover assembly 2 for closing the first open end portion 6, and a second cover assembly 3 for closing the second open end portion 7.
Components of the cover assemblies are schematically shown using dashed lines and the cover assemblies comprise further details not relevant to the present invention, thus not illustrated.
The first cover assembly 2 comprises a first flange member 8 attached to the housing body 4 at the first open end portion 6 of the housing body 4 with a first flange 10 of the first flange member 8 extending along the longitudinal axis L either into the inner cavity 5 along an inside surface of the housing body 4, or along an outer surface of the housing body 4. The first flange member 8 is attached to the housing body 4 by adhesive.
The second cover assembly 3 comprises a second flange member 9 attached to the housing body 4 at the second open end portion 7 of the housing body 4 with a second flange 11 of the second flange member 9 extending along the longitudinal axis L, either into the inner cavity 5 along an inside surface of the housing body 4 or along the outer surface of the housing body 4. The second flange member 9 is attached to the housing body 4 by adhesive.
Also, the housing body 4 is made of a fibre-composite material, such as fibreglass reinforced plastic. In other embodiment, other fibres than glass fibres may be used instead. Also, any suitable matrix material may be used, such as polyester, vinyl ester or epoxy.
The first 8 and second 9 flange members are made of metal, such as stainless steel or any other suitable metal.
Each respective flange 10, 11 is sized to press-fit with the housing body 4 when attached to the housing body 4. In other embodiments, the press-fit may alternatively be omitted.
The press-fit is preferably such that press-fit is present at least within a temperature range of -40 to +100 degrees Centigrade.
At assembly of the OLTC the housing body and the respective first or second flange member may be heated or cooled, as appropriate, to different temperatures to enable temporarily reduced mechanical interference, thus enabling easier assembly.
In this embodiment, both of the first 8 and second 9 flange members comprise a respective central opening enabling access into the inner cavity 5 of the housing body 4 through the central opening. Also, a respective cover member 12 is attachable to the respective flange member using mechanical fasteners, threaded connection or an adhesive, said cover member 12 being adapted to cover the respective central opening.
In other embodiments, only one of the first 8 and second 9 flange members may comprise a central opening, since one opening is enough to enable access into the inner cavity.
The at least one cover member 12 is attached to the flange member using mechanical fasteners, and wherein a sealing member or sealant is provided between the flange member and the cover member 12 for providing a gas tight seal between the flange member and the respective cover member 12.
the mechanical fasteners are removable fasteners, such as screws, but may in other embodiments alternatively be replaced by any other suitable non-removable mechanical fastener, such as rivets.
The adhesive is an epoxy adhesive but may in other embodiments alternatively be any other suitable adhesive.
The first 10 and second 11 flange may be provided with one or more recesses facing the housing body 4 or provided with one or more structured surface portions facing the housing body 4, wherein the adhesive is applied at said one or more recesses or structured surface portions.
In this embodiment, the housing body 4 is cylindrical but in other embodiments, any other suitable shape may be used instead.

In use, the OLTC is typically provided on a floating platform for use at sea.

Table of reference numerals

1	OLTC
2	first cover assembly
3	second cover assembly
4	housing body
5	inner cavity
6	first open end portion
7	second open end portion
8	first flange member
9	second flange member
10	first flange
11	second flange
12	cover members
13	sealing member

Claims

An on-load tap changer (OLTC) (1) comprising a housing, said housing comprising a housing body (4) extending along a longitudinal axis (L), said housing body (4) comprising an inner cavity (5), a first open end portion (6) and an opposite second open end portion (7),
said housing further comprising a first cover assembly (2) for closing the first open end portion (6), and a second cover assembly (3) for closing the second open end portion (7),

said first cover assembly (2) comprising a first flange member (8) attached to the housing body (4) at the first open end portion (6) of the housing body (4) with a first flange (10) of the first flange member (8) extending along the longitudinal axis (L) either into the inner cavity (5) along an inside surface of the housing body (4), or along an outer surface of the housing body (4),

said first flange member (8) being attached to the housing body (4) by adhesive,

said second cover assembly (3) comprising a second flange member (9) attached to the housing body (4) at the second open end portion (7) of the housing body (4) with a second flange (11) of the second flange member (9) extending along the longitudinal axis (L), either into the inner cavity (5) along an inside surface of the housing body (4) or along the outer surface of the housing body (4),

said second flange member (9) being attached to the housing body (4) by adhesive,

said housing body (4) being made of a fibre-composite material, and

said first (8) and second (9) flange members being made of metal.
An on-load tap changer (1) according to claim 1, wherein the respective flange (10, 11) is sized to press-fit with the housing body (4) when attached to the housing body (4).
An on-load tap changer (1) according to claim 2, wherein the press-fit is such that press-fit is present at least within a temperature range of -40 to + 100 degrees Centigrade.
An on-load tap changer (1) according to any one of the preceding claims, wherein at least one of said first (8) and second (9) flange members comprises:
a central opening enabling access into the inner cavity (5) of the housing body (4) through the central opening, and

a respective cover member (12) attachable to the respective flange member using mechanical fasteners, threaded connection or an adhesive, said cover member (12) being adapted to cover the respective central opening.
An on-load tap changer (1) according to claim 4, wherein the at least one cover member (12) is attached to the flange member using mechanical fasteners, and wherein a sealing member or sealant (13) is provided between the flange member and the cover member (12) for providing a gas tight seal between the flange member and the respective cover member (12).
An on-load tap changer (1) according to claim 5, wherein the mechanical fasteners are removable fasteners, such as screws.
An on-load tap changer (1) according to any one of the preceding claims, wherein the adhesive is an epoxy adhesive.
An on-load tap changer (1) according to any one of the preceding claims, wherein the first (10) and second (11) flange is provided with one or more recesses facing the housing body (4) or provided with one or more structured surface portions facing the housing body (4), wherein the adhesive is applied at said one or more recesses or structured surface portions.
An on-load tap changer (1) according to any one of the preceding claims wherein the housing body (4) is cylindrical.