Telescopic Switch Curved Contact Fingers
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Solution Overview
Problem
Existing telescopic disconnect switches in isolated phase bus ducts require frequent maintenance due to limited operational cycles, as they typically need servicing after about 500 operations, which is not sufficient to meet current market demands for increased reliability and efficiency.
Innovation Solution
The design features first and second fixed conductors with circumferentially positioned contact fingers, a telescopic conductor with a concave arc-shaped contact surface, and a second contact finger surface portion that engages a groove, increasing the contact surface area and reducing contact resistance, thereby enhancing current capacity and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flat contact surface portions are used on contact fingers, then the switch can operate between open and closed positions, but the number of operational cycles is limited to about 500 operations before maintenance is required
Solution Approach 1:
The contact surface tip portion is formed with a concave arc shape having a radius slightly greater than the radius of the fixed conductor's outside contact wall surface. This curved geometry enables wiping electrical contact that conforms to the cylindrical surface of the fixed conductor, increasing contact surface area and improving current capacity while reducing contact resistance and enhancing operational reliability beyond 500 cycles
2Quantity of substance
If point contact engagement is used between contact fingers and conductors, then the switch structure is simple, but the surface area making electrical contact is limited, resulting in higher contact resistance and reduced current capacity
Solution Approach 1:
The concave arc shaped contact surface tip portion with radius R2 slightly greater than R1 creates a line contact rather than point contact with the fixed conductor. This curved geometry increases the effective contact surface area, reducing contact resistance and enhancing current capacity without significantly complicating the contact finger structure
3Reliability
If the contact surface area is increased to reduce contact resistance, then current capacity improves, but the contact finger structure becomes more complex
Solution Approach 1:
The concave arc shaped contact surface tip portion is formed by simple radial cutting of the contact finger material. This geometric feature increases contact surface area and improves current capacity while maintaining relatively simple manufacturing processes and structural integrity
Solution Approach 2:
The radius of the concave arc (R2) is specifically designed to be slightly greater than the radius of the fixed conductor's outside contact wall surface (R1). This parameter relationship ensures optimal wiping contact that maximizes electrical contact area and current capacity while maintaining structural simplicity
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 design increases the number of operational cycles between maintenance, improving current capacity and reducing temperature rise, resulting in a higher amperage rating and extended mechanical wear capacity compared to traditional flat contact surface switches.
Implementation Method 1
the first contact surface tip portion overlying in wiping electrical contact one of the first outside contact wall surface portions of the telescopic conductor when in the closed position
Data Source
Figure 1
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AI summary
A high voltage, high current telescopic disconnect switch (10) suitable for use in isolated phase bus duct has two fixed conductors (14, 16) and a movable telescopic conductor coaxially disposed within the first fixed conductor (14) and movable to a closed position bridging the first and second fixed conductors (14, 16). A plurality of contact fingers (26) are mounted to the fixed conductors (14, 16) and have contact surfaces (42) that extend into engagement with the telescopic conductor (22) to make electrical contact between the fixed conductors (14, 16) through the telescopic conductor (22) when in a closed position. The contact surface of each of the fingers (26) comprises a first tip portion (38) that extends beyond the fixed conductor and has a first radius that is slightly greater than the radius of the telescopic conductor (22) so that the first tip portion (38) presents an arcuate width that overlies in wiping electrical contact the telescopic conductor (22) when in the closed position.