Tap Changer Contact Unit With Opposed Contact Areas
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Solution Overview
Problem
Existing tap changers face challenges in achieving a compact design while maintaining balanced attraction and separating forces between contact fingers, and ensuring adequate cooling for high currents, as reducing contact finger length disrupts force balance and reduces cooling area.
Innovation Solution
The contact unit features elongated contact elements with contact areas positioned on opposite sides of a plane orthogonal to the contact ring's axis, allowing for a longer current path and balanced forces, and includes additional contact areas and a through hole to increase mechanical stability and attractive forces, while maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between fixed contacts and contact ring is reduced to achieve compact design, then the size of tap selector is reduced, but the length of contact fingers must be reduced which disrupts the balance between attraction forces and separating forces
Solution Approach 1:
The patent positions contact areas on opposite sides of a plane orthogonal to the longitudinal axis, transitioning from a single-plane arrangement to a three-dimensional configuration. This dimensional change allows the contact elements to maintain adequate length for force balance while reducing the radial distance between fixed contacts and contact ring, thus achieving compactness without sacrificing force balance stability.
Solution Approach 2:
The moving contact is divided into multiple contact elements with distinct first and second contact areas. This segmentation allows each contact element to be optimized independently - the first contact area maintains sufficient length for force balance while the second contact area positions on the opposite side enable compact overall design. The current path flows through multiple segmented contact areas rather than a single continuous element.
2Volume of moving object
If the length of contact fingers is reduced to achieve compact design, then the size of tap selector is reduced, but the cooling area of the moving contact becomes too small to handle high currents
Solution Approach 1:
By positioning contact areas on opposite sides of a plane orthogonal to the longitudinal axis, the patent extends the current path through three-dimensional space rather than along a single linear dimension. This allows the current to traverse a longer path through multiple contact areas (first contact area to second contact area) without increasing the overall radial size, thereby maintaining adequate cooling surface area while achieving compact external dimensions.
Solution Approach 2:
The current path is segmented into multiple contact areas rather than flowing through a single continuous contact finger. The current flows from the first contact area through the contact element to the second contact area on the opposite side, creating multiple heat dissipation zones along the current path. This segmentation allows the total cooling area to be distributed across multiple smaller contact regions, maintaining adequate thermal management in a compact design.
3Temperature
If the number of parallel contact fingers is increased to maintain cooling area, then the current handling capability is improved, but the space demand increases rather than decreases
Solution Approach 1:
Instead of adding more parallel contact fingers in the radial direction (increasing space demand), the patent utilizes the third dimension by positioning contact areas on opposite sides of a plane orthogonal to the longitudinal axis. This allows the current path to extend through the depth of the contact element rather than requiring additional parallel elements, maintaining cooling area without increasing the radial or axial footprint of the tap selector.
Solution Approach 2:
Each contact element serves multiple functions simultaneously: it provides mechanical connection, establishes electrical contact at two separate locations (first and second contact areas), and creates a extended current path for heat dissipation. This multi-functionality eliminates the need for additional dedicated cooling structures or parallel contact fingers, achieving thermal management within the compact contact element itself.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables a compact and stable contact unit that maintains balanced forces and adequate cooling for high currents, reducing the size of tap selectors and diverter switches without increasing the number of contact elements.
Implementation Method 1
The currents through the parallel contact fingers of the moving contact causes attraction forces between the contact fingers. Further, opposing currents in the contact areas generate separating forces.
Implementation Method 2
Each of the contact elements comprises a first contact area for providing electrical contact with the fixed contacts and a second contact area for providing electrical contact with the contact ring, and the moving contact is designed so that an electric path is formed between the first and second contact areas.
Data Source
Figure 1~3
Figure 4~6
AI summary
The present invention relates to a contact unit (1) for a tap changer comprising a contact ring (2) having a central axis (A1), a plurality of fixed contacts (4; 4a-b) arranged at a distance from the contact ring in different radial directions, and a moving contact (6) arranged rotatable about the central axis of the contact ring and adapted to electrically connect the fixed contacts one at a time with the contact ring. The moving contact comprises two elongated contact elements (8a-b). Each of the contact elements comprises a first contact area (14a-b) for providing electrical contact with the fixed contacts and a second contact area (16a-b) for providing electrical contact with the contact ring. The moving contact is designed so that an electric path is formed between the first and second contact area. The first contact area (14a-b) and the second contact area (16a-b) are positioned on opposite sides of a plane (P1) orthogonal to a longitudinal axis (A2) of the moving contact and including the central axis (A1) of the contact ring.