On-Load Tap Changer Switch With Sequential Arcing Contacts
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Solution Overview
Problem
On-load tap-changers experience increased contact wear due to arcing during high current and voltage operations, leading to potential faults and malfunctions.
Innovation Solution
A switch design with a contact unit comprising a moving contact and two arcing contacts, where the second arcing contact assumes and leaves the first position before and after the first arcing contact, respectively, during the switching process, reducing arc duration and wear through a multi-stage commutation process, and utilizing different conductive materials and geometric shapes to manage wear uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single arcing contact is used for switching, then the switching operation is simple, but the arc duration is long causing increased contact wear
Solution Approach 1:
The single arcing contact is segmented into two separate arcing contacts (first and second arcing contacts) that operate in sequence. This segmentation allows the arc duration to be divided into two shorter intervals, reducing the total wear on each individual contact while maintaining the overall switching function.
Solution Approach 2:
The switching operation employs periodic action through the sequential operation of two arcing contacts. The first arcing contact operates during an initial arc period, then the second arcing contact operates during a subsequent arc period. This periodic alternation reduces the cumulative arc exposure time for each contact, thereby reducing wear and improving reliability.
2Reliability
If the second arcing contact operates simultaneously with the first, then the switching is faster, but the arc intensity increases causing more wear
Solution Approach 1:
The switching process is divided into periodic phases where the first arcing contact operates during an initial period and the second arcing contact operates during a subsequent period. This temporal separation maintains switching speed while reducing arc intensity at any given moment, preserving contact material.
Solution Approach 2:
The second arcing contact acts as an intermediary that takes over the switching function after the first arcing contact has completed its portion of the operation. This intermediary approach allows the switching process to continue without interruption while distributing the arc exposure and reducing intensity on each individual contact.
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
The multi-stage commutation design shortens arc duration and reduces contact wear, enhancing the switch's reliability and longevity under high load conditions.
Implementation Method 1
This regularly produces arcs at the switching contacts, which melt or burn small amounts of the contact material and thus lead to contact wear
Data Source
AI summary
An on-load tap-changer of a tap-changing transformer has a switch. The switch has: a take-off contact; a primary fixed contact; and a contact unit. The contact unit has a moving contact, a first arcing contact and a second arcing contact. These contacts are pivotable about a pivot axis during a switchover process such that the contacts assume a first position, in which they make contact with the take-off contact and the primary fixed contact, and a second position, in which they are separated from the take-off contact and the primary fixed contact. The second arcing contact assumes the first position before the first arcing contact when switching over from the second position to the first position and leaves the first position after the first arcing contact when switching over from the first position to the second position.