Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/12—Contacts characterised by the manner in which co-operating contacts engage
  • H01H1/36—Contacts characterised by the manner in which co-operating contacts engage by sliding
  • H01H1/42—Knife-and-clip contacts
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
  • H01H9/0005—Tap change devices
  • H01H9/0016—Contact arrangements for tap changers

Definitions

• the present disclosure is related to a static contact unit, a contact system and a tap changer.
• Tap changers realize a mechanism in transformers which allows for variable turn ratios to be selected in distinct steps, for example. In view of movable and stationary electrically engaging contacts it is a challenge to provide a stable and reliable mechanism.
• a static contact unit for a tap changer comprises a contact body that is configured to be arranged statically with respect to a movable contact that is arranged at a moving shaft of the tap changer.
• the static contact unit further comprises two contact elements that are coupled to the contact body configured to establish an electrical contact to the movable contact of the moving shaft.
• the static contact unit further comprises a spring element that is coupled to both contact elements inbetween with respect to a longitudinal axis of the moving shaft configured to bias the contact elements so that, with respect to a state in which the tap changer is assembled, the contact elements are biased or pre-loaded simultaneously in direction towards each other in sections for making electrical contact at least.
• the respective static contact unit can form an upper, lower or middle electrical static contact of a contact system realizing a pre-selector of an on-load tap changer.
• the aforementioned moving shaft and the one or more movable contacts realize components of such a pre-selector interacting with the one or more static contact units. Accordingly, the components of the static contact unit and the components of the pre-selector are configured preferably in coordination with each other.
• the spring element is formed as a cylindrical coil torsion spring and comprises two spring arms at opposite ends which are coupled to a respective associated contact element.
• Each spring arm can comprise a respective hook at its end which is in contact with an associated outer surface of the respective contact element pulling or pushing the respective contact element towards the other one. Regardless of whether it is referred to as pulling or pushing, the spring force acts in the direction towards each other so that a reliable electrical contact with the movable contact can be established.
• the respective contact element comprises a spring arm recess at an outer surface configured in coordination with the associated spring arm or spring hook of the spring element so that the end portion of the respective spring arm is arranged inside the spring arm recess of the associated contact element. Due to such a configuration, the spring can be securely attached to the contact elements and is not bulky so that the outer surface of the contact elements is nearly flat.
• the contact body and/or the contact elements comprises one or more guiding and/or limiting elements which are configured to guide and/or limit a movement of the contact elements relative to the contact body.
• the contact body can comprise two limiters one forming a front wall element and the other one forming a back wall element with respect a longitudinal axis of the contact unit. With respect to a state in which the tap changer is assembled, the front wall element is arranged closer to the moving shaft than the back wall element.
• the static contact unit comprises an axle configured to support the spring element, wherein the axle extends through the spring element and an axle recess of the contact body and is fixed to the contact body by a retaining element.
• the axle supports the spring element and holds it in a given axial position.
• the axle is arranged closer to the aforementioned back wall element than to the front wall element. Such a configuration can contribute to a beneficial stability and force effect of the spring element and the contact elements.
• the contact elements each comprise a front side contact and a rear side contact with respect a longitudinal axis of the contact unit so that, with respect to a state in which the tap changer is assembled, the respective rear side contact is in contact with the contact body and the front side contact is configured to establish a respective electrical contact to a contact element of the movable contact of the moving shaft.
• the contact elements can realize parallel contact plates that are statically coupled to the contact body. Each parallel contact element extends in a direction towards the moving shaft to establish a respective electrical contact to a contact surface of the movable contact of the moving shaft when the tap changer is assembled.
• the contact elements are designed to establish the operational contact and set up electrical switching.
• the static contact unit comprises four contact elements that are coupled to the contact body configured to establish an electrical contact to the movable contact of the moving shaft, and two spring elements that are coupled to a respective pair of two contact elements inbetween, preferably above each other supported by an axle.
• the spring elements are both configured to bias the associated contact elements so that, with respect to a state in which the tap changer is assembled, the respective pair of contact elements are biased or pre-loaded simultaneously in direction towards each other in sections at least.
• a contact system for a tap changer comprises a linear moving shaft elongated predominantly along a longitudinal axis, and a knife contact unit that is configured axially movable along a longitudinal axis of the moving shaft.
• the contact system further comprises one or more embodiments of the static contact units described above, which are arranged statically relative to the knife contact unit in view of the contact body at least.
• the contact system can realize a pre-selector of a tap changer and enables secure and reliable electrical switching.
• the contact system can be implemented in an on-load tap changer with a space-saving design due to the static contact units, in particular in combination with cylindrical coil torsion spring elements.
• the contact comprises an embodiment of the static contact unit as described above, features and characteristics of the static contact unit are also disclosed with respect to the contact system and vice versa.
• the contact system comprises three static contact units according to an embodiment as described above.
• a first static contact unit is configured to form an upper or positive contact
• a second static contact unit is configured to form a lower or negative contact
• a third static contact unit is configured to form a middle or ground contact between the first and the second contact with respect to the longitudinal axis of the moving shaft.
• the knife contact unit comprises a plurality of movable contacts coupled to the moving shaft configured to establish electrical contact to one or more of the static contact units for electrical switching.
• the knife contact unit comprises at least one movable contact with two contact wing elements, wherein the two wing elements forming a funnel-shaped movable contact and are geometrically formed in coordination with the contact elements of the static contact units.
• the associated wing element is arranged between and in contact with both contact elements of the respective contact unit. Due to such a configuration a very reliable and secure electrical contact between the static contact unit and the movable contact can be established for electrical switching.
• the contact elements of the respective contact units and the wing elements of the movable knife contact unit can comprise edges and/or corners with a chamfer or rounding configured to establish a respective secure electrical contact. Such a configuration enables low-resistance, low-wear contacting.
• a tap changer comprises an embodiment of the contact system described above forming a pre-selector of the tap changer, and a selector with one or more contact devices for electrical switching coupled to the pre-selector.
• the tap changer comprises an embodiment of the contact system and the static contact unit as described above, features and characteristics of the contact system and/or the static contact unit are also disclosed with respect to the tap changer and vice versa.
• the described embodiments for the static contact unit, the contact system and the tap changer each allow for a compact electrical contact design providing contact force in an electrical contact pair by means of a spring element, preferably realized as a cylindrical coil torsion spring.
• the described static contact unit enables to counteract such unwanted effects.
• the static contact unit allows for a compact electrical contact system with tension and compression spring elements. It beneficially enables to keep required insolation distances and it needs little space in a corresponding transformer tank assembly and contributes to less production and assembling time and reduced costs.
• Figures 1 to 3 illustrate an embodiment of a contact system 30 realizing a pre-selector for a tap changer in different views.
• Figure 1 shows a perspective view.
• Figure 2 shows a side view with partial cross section.
• Figure 3 shows a top or bottom view along a longitudinal axis L1.
• the contact system 30 comprises three static contact units 20 (see also Figs. 4 to 5 ).
• the contact system 30 comprises a linear moving shaft 1 elongated predominantly along a longitudinal axis L1 and a knife contact unit 2 that is configured axially movable along the longitudinal axis L1 of the moving shaft 1.
• the three static contact units 20 are arranged above each other and statically relative to the knife contact unit 2.
• a first static contact unit 21 is configured to form an upper contact unit
• a second static contact unit 22 is configured to form a lower contact unit
• a third static contact unit 23 is configured to form a middle contact unit between the first and the second contact unit 21, 22 with respect to the longitudinal axis L1 of the moving shaft 1 (see Fig. 2 ).
• the first contact unit 21 can realize a contact with positive potential
• the second contact unit 22 a contact with negative potential
• the third contact unit 23 can form a ground contact with zero potential.
• the static contact units 21, 22, 23 each comprise four contact elements 5 forming two respective parallel contact pairs above each other with respect to the longitudinal axis L1.
• the contact elements 5 each are coupled to an associated contact body 4 of the corresponding static contact unit 20 configured to establish an electrical contact to a respective cam or movable contact 3 of a knife contact unit 2 arranged at the moving shaft 1.
• the knife contact unit 2 comprises a movable contact 3 with two contact wing elements 11.
• the wing elements 11 comprise a respective inner and outer contact surfaces configured to make electrical contact to front portions of the contact elements 5 of the respective static contact unit 20 (see Fig. 3 ).
• the wing elements 11 form a funnel-shaped contact element 3 that is geometrically formed in coordination with parallel contact elements 5 of the static contact units 20.
• FIG. 4 and 5 show in a perspective illustration a respective disassembled view of the static contact unit 20.
• the figures 4 and 5 are equal with respect to their illustration but comprise different reference signs in part for sake of clarity.
• the respective contact unit 20 further comprise two spring elements 6 formed as cylindrical coil tension springs which are coupled to an associated pair of contact elements 5 inbetween.
• the spring elements 6 are configured to bias the contact elements 5 so that the contact elements 5 are pre-loaded simultaneously in direction towards each other at the front portion at least to establish an electrical contact securely and reliably with an associated wing element 11 of the movable contact 3 (see Fig. 3 ).
• Each spring element 6 comprises two spring arms 7 at opposite ends which are coupled to a respective associated contact element 5.
• Each spring arm 7 comprises a spring hook 8 at its end which are in contact with an outer surface 19 of the respective associated contact element 5 pulling or pushing the respective contact element 5 towards the other one.
• the contact body 4 can be formed from one-piece and may comprise a cross-shape with two levels for the two pair of contact elements 5.
• the contact body 4 comprises four guidance channels 18 for the four contact elements 5 (see Fig. 5 ).
• the contact body 4 further comprises limiting element which are configured to limit and/or guide a movement of the contact elements 5 relative to the contact body 4.
• the contact body 4 With respect to a longitudinal axis L2 of the static contact unit 20 (see Fig. 3 ), the contact body 4 comprises a front wall element 9, a back wall element 10 and a limiter recess 16 acting as limiting and/or support or guiding elements.
• the front wall element 9 is arranged closer to the moving shaft 1 than the back wall element 10.
• the contact elements 5 comprise a respective limiter 15 arranged inside the limiter recess 16 of the contact body 4.
• the front wall element 9 limits a movement of the contact element 5 in direction towards the moving shaft 1.
• the back wall element 10 limits a movement of the spring element 6 in direction away from the moving shaft 1.
• the static contact unit 20 further comprises an axle 12 which supports the spring elements 6.
• the axle 12 extends through the spring elements and through an axle recess 17 of the contact body 4 (see Fig. 4 ).
• the axle 12 is fixed to the contact body 4 by retaining rings 13 arranged at opposite sides of the contact body 4 in a respective ring recess 14.
• the axle 12 is preferably arranged closer to the back wall element 10 than to the front wall element 9 (see Fig. 3 ).
• the contact elements 5 each comprise a front side contact and a rear side contact with respect the longitudinal axis L2 of the contact unit 20 so that the respective rear side contact is in contact with the contact body 4 and the front side contact is configured to establish a respective electrical contact to the associated wing element 11 of the movable contact 3 of the moving shaft 1.
• the described contact system 30 can realize a compact electrical contact system for an on-load tap changer with the three static contacts (e.g. +, 0, -) situated in vertical direction.
• the knife contact element unit 2 forms a contact bridge in a current-carrying chain, which is fixed to the movable or moving shaft 1.
• the moving shaft 1 can be moved along the longitudinal axis L1 in vertical direction from (+) to (-) position and back.
• the first, second and third static contact units 21-23 are mounted and situated in vertical direction. Alternatively, the design can be arranged horizontally as well.
• Respective two pairs of parallel contact elements 5 are mounted in the guiding channels 18 in every static contact unit 20 and create a contact bridge between the contact bodies 4 and contact surfaces of the wing elements 11 on the movable knife contact 3.
• the respective limiter 15 can be formed in the middle of each of the contact elements 5 and is configured to prevent their movement in front direction to the front wall 9 of each contact body 4. The movement in back direction is prevented by the back wall 10 situated of the back side on the contact holders 4.
• a respective cylindrical coil torsion spring element 6 is mounted between the parallel electrical contact pair 5.
• Each of the two arms 7 of the spring element 6 simultaneously presses the corresponding contact element 5 of the contact pair by means of its corresponding tail or hook 8 formed at the end of the spring arms 7.
• the hooks 8 of the spring arms 7 are situated on this way that is reduced the sliding between the hooks 8 and the parallel contact elements 5.
• the outer surface 19 of the respective contact element 5 can comprise a groove or slot to avoid an unwanted sliding of the hook 8.
• the supporting axle 12 passes inside the respective coils of the spring elements 6 and is fixed to the contact body 4 by means of the two retaining ring elements 13 which keep the spring elements 6 in the correct position.
• the two arms 7 of the corresponding spring element 6 are rotating around the supporting axle 12 during connecting and disconnecting of the pair of parallel contact elements 5 to the knife contact element 3.
• the supporting axle 12 is situated closer to the back stationary contact points at the back wall 14 than to the front wall 9.
• the axle 12 can be arranged in a middle between the front wall 9 and the back wall 10 or closer to the front wall 9 than to the back wall 10.
• the hook 8 is arranged in a middle of the outer surface 19 of the respective contact element 5 but can alternatively arranged closer to a back end in direction to the back wall 10 along the longitudinal axis L2 or closer to a front end in direction to the front wall 9 along the longitudinal axis L2.
• Such a modification can be considered by forming the spring arms 7 shorter or longer, respectively and depending on specifications regarding stability and force effect, for example.
• the described embodiments of the static contact units 20-23 and the contact system 30 each allow for a smaller distance between the pair of contact elements 5, in particular at the same level, thus beneficially affecting electrodynamic forces.
• the torsion springs elements 6 are located inside the contact unit 20 and there are no protruding springs or parts at the outside, which leads to a better distribution of the electromagnetic field and allows reducing the dielectric distances and reducing the dimensions of the static contact unit 20.
• the torsion spring elements 6 can be advantageously formed symmetric and provide a relatively constant spring force over their operating range and allow for uniform contact force under geometric and manufacturing deviations.

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• Elimination Of Static Electricity (AREA)

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Citations (3)

• 2024
  • 2024-05-14 EP EP24175759.0A patent/EP4651165A1/de active Pending
• 2025
  • 2025-04-30 WO PCT/EP2025/061847 patent/WO2025237684A1/en active Pending

Patent Citations (3)

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