Tubular Earthing Switch Contacts for High-Current Copper Reduction
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Solution Overview
Problem
Conventional earthing switches require large amounts of copper material, leading to high costs and unsatisfactory performance due to their shape and assembly methods, which result in inefficient current carrying capacity and increased risk of skin effect.
Innovation Solution
The earthing switch employs tubular blades with flattened ends and contact fingers arranged on a copper tube, allowing for better current carrying capacity and earthing performance with reduced copper usage, along with elastic members and a cushion to enhance contact stability and reduce bounce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional copper contacts with traditional shapes and assembly methods are used, then sufficient current carrying capacity can be achieved, but the amount of copper material required increases leading to high costs
Solution Approach 1:
The movable contact is divided into a tubular blade component and separate contact fingers. The tubular blade provides the main current carrying path while the contact fingers make contact with the fixed contact. This segmentation allows optimization of each component's function and reduces total copper usage.
Solution Approach 2:
The tubular blade has a flattened first end where it connects to the operating mechanism, providing localized reinforcement exactly where mechanical strength is needed for rotation and contact making/breaking, while the rest of the tubular blade maintains a circular cross-section for efficient current carrying.
2Reliability
If traditional copper contacts are used, then earthing performance can be maintained, but the shape and assembly methods result in inefficient current carrying capacity and increased risk of skin effect
Solution Approach 1:
The tubular blade has a circular cross-section along most of its length, which is more efficient for current carrying than flat copper bars. The curved/tubular shape reduces skin effect compared to flat contacts while maintaining sufficient mechanical strength through the flattened end section.
3Ease of manufacture
If contact fingers are fixed to the tubular blade without reinforcement, then assembly is simpler, but the second end of the tubular blade may deform when contact fingers are riveted
Solution Approach 1:
A pressure bar is inserted into the tubular blade before the contact fingers are riveted to it. This preliminary action reinforces the tubular blade structure in advance, preventing deformation during the riveting process while keeping the overall assembly process relatively simple.
Data Source
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AI summary
Embodiments of the present disclosure provide a earthing switch for a switchgear. The earthing switch comprises a plurality of fixed contacts arranged in a plurality of phases of the switchgear; and a plurality of movable contacts operable to rotate by an operating mechanism of the switchgear so that the movable contacts can be coupled to or decoupled from the respective fixed contacts, wherein each of the movable contacts comprises a tubular blade mounted on the operating mechanism, a first end of the tubular blade being flattened. By using the tubular blade as a movable blade, the earthing switch can withstand a large current with less copper material being used due to a better current carrying capacity of the tubular blade. Furthermore, the first end of tubular blade where the tubular blade is mounted on the operating mechanism is flattened, which gives the tubular blade a higher flexural strength and tensile strength. Moreover, the tubular blade can be made in a cost efficient way.