Pre-Selector Actuating Device With Variable Velocity Profile
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Solution Overview
Problem
The existing pre-selector actuating devices for tap changers in transformers do not optimize the movement pattern of the pre-selector arm, which requires varying velocities and forces at different phases of the movement, leading to suboptimal performance in overcoming static friction, capacitive breaking, and contact engagement.
Innovation Solution
A pre-selector actuating device with a movement transmission mechanism that includes two abutment units and a cam surface, allowing for distinct velocity phases: a high force initial period to overcome static friction, a high velocity intermediate period for quick capacitive breaking, and a low velocity end period to prevent bouncing, achieved through the cooperation of rollers and cam sections with different radii and shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant speed and force is used to actuate the pre-selector arm, then the actuation mechanism is simple, but the performance is suboptimal in overcoming static friction, capacitive breaking, and contact engagement
Solution Approach 1:
The patent applies dynamics by transitioning from constant speed/force actuation to a variable speed profile with three distinct phases (initial period with acceleration, intermediate period with constant high speed, end period with deceleration). This dynamic approach optimizes performance at each phase: overcoming static friction initially, achieving quick capacitive breaking in the intermediate phase, and preventing bouncing during contact engagement, while maintaining acceptable mechanism complexity through a structured transmission design.
2Loss of time
If high velocity is used during the entire pre-selector stroke, then capacitive breaking time is reduced, but the risk of bouncing upon contact increases
Solution Approach 1:
The patent implements periodic action by dividing the pre-selector stroke into three distinct velocity phases. The intermediate period maintains high constant velocity to minimize capacitive breaking time, while the end period introduces deceleration to reduce impact velocity and prevent bouncing. This periodic velocity modulation resolves the contradiction by applying high speed only when needed for capacitive breaking, then reducing speed for stable contact engagement.
3Force
If high force is applied throughout the entire movement, then static friction is effectively overcome, but unnecessary energy is consumed during low-demand phases
Solution Approach 1:
The patent applies segmentation by dividing the actuation process into three distinct phases with different force requirements. The initial period applies high force to overcome static friction between contacts, while the intermediate and end periods use reduced force levels appropriate for their respective functions. This segmented approach eliminates unnecessary energy consumption during low-demand phases while ensuring sufficient force is applied when needed to break static friction.
Data Source
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AI summary
The invention relates to a pre-selector actuating device for a pre-selector in a tap changer of a transformer. The device includes a drive input means (11) arranged to make an input movement stroke of a predetermined length. Further it includes a pre-selector arm (51) arranged to make a pre-selector stroke from a first contact to a second contact. There is a movement transmission mechanism connected to the drive input means (11) and to the pre-selector arm (51). According to the invention, the movement transmission mechanism is arranged to convert the input movement stroke such that the pre-selector stroke obtains a movement pattern having an initial period of relatively slow movement, an intermediate period of relatively fast movement and an end period of relatively slow movement. The invention also relates to a tap changer having such a device and to a transformer provided with such a tap changer.