OLTC Contact System With Cam Rollers to Reduce Wear and Torque
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Solution Overview
Problem
Existing on-load tap changer (OLTC) contact systems experience significant wear and torque issues due to friction forces during switching operations, affecting the performance of vacuum interrupters.
Innovation Solution
A contact system with a movable contact that uses a cam portion to open jaws via rollers, reducing mechanical friction and torque by employing materials with higher hardness and a rolling interaction, ensuring minimal contact between the cam portion and fixed contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the movable contact uses sliding friction to engage with fixed contacts, then the contact system can be simple in structure, but significant wear occurs on contact surfaces
Solution Approach 1:
The patent introduces a cam portion as an intermediary element between the movable contact and the fixed contacts. This cam portion transforms the direct sliding friction contact into a rolling contact mechanism, where the cam surface interacts with the fixed contact surfaces through rolling motion rather than sliding, thereby reducing wear on the contact surfaces while maintaining the simplicity of the overall contact system structure.
2Ease of operation
If the movable contact slides between fixed contacts with friction, then the switching operation can be straightforward, but unwanted torque is generated on the main shaft
Solution Approach 1:
The cam portion serves as a mediator that converts the sliding friction force into rolling friction force. This transformation reduces the magnitude of the friction force that translates into torque on the main shaft, while the cam mechanism itself guides the movable contact through the switching operation, maintaining ease of operation with reduced unwanted torque effects.
3Reliability
If the movable contact establishes electrical contact directly with fixed contacts, then the electrical connection can be reliable, but mechanical wear increases during switching
Solution Approach 1:
The cam portion acts as a wear-reducing intermediary that facilitates the establishment of electrical contact between the movable contact and fixed contacts. During the switching operation, the cam surface rolls against the fixed contact surfaces, enabling reliable electrical connection while minimizing direct sliding friction and material wear at the contact interfaces.
Solution Approach 2:
The patent replaces the traditional sliding friction mechanical contact mechanism with a rolling contact mechanism using the cam portion. This substitution maintains the reliability of electrical contact establishment while significantly reducing mechanical wear on the contact surfaces by eliminating the sliding friction component.
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
Reduces wear on contact surfaces and minimizes torque on the shaft, enhancing the operational efficiency and longevity of the OLTC system.
Implementation Method 1
the movable contact comprises a cam portion (12) configured to move between the two rollers (11a, 11b) for opening the jaws (5a, 5b) in a switching operation
Implementation Method 2
due to the rolling interaction of the rollers with the cam portion, rolling friction forces occur, which reduces a torque on the movable contact
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A contact system (1) for an on-load tap changer (30) comprises a movable contact (2) configured to switch between several fixed contacts (3, 4) in a switching operation, wherein the movable contact (2) comprises a contact portion (6) for establishing an electrical contact with one of the fixed contacts (3, 4) in an operating position, wherein each of the fixed contacts (3, 4) comprises two jaws (5a, 5b) configured for clamping the movable contact (2), wherein each of the fixed contacts (3, 4) comprises two rollers (11a, 11b), wherein the movable contact (2) comprises a cam portion (12) configured to move between the two rollers (11a, 11b) for opening the jaws (5a, 5b) in a switching operation.