Draw-out Current Limiting Fuse for Transformer Replacement
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Solution Overview
Problem
Current current-limiting fuses in liquid-filled distribution transformers are difficult to replace in the field due to hardwired connections and the need to drain dielectric fluid, while canister fuses are limited in high-voltage applications and prone to arcing and contamination.
Innovation Solution
A draw-out fuse design featuring a sacrificial element within an insulative sheath, with contact blades extending outwardly and contact clips allowing selective linear displacement, enabling in-field replacement without draining dielectric fluid and minimizing exposure to contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional current-limiting fuses are used in liquid-filled distribution transformers, then the fuses provide reliable current protection, but the fuses are difficult to replace in the field requiring draining of dielectric fluid and transformer disconnection
Solution Approach 1:
The fuse assembly is segmented into a replaceable fuse unit (containing the fuse element and contact blades) and a stationary mounting structure (tank flange with aperture and guide openings). This segmentation allows the fuse unit to be independently removed and replaced without affecting the transformer tank or requiring draining of dielectric fluid, while maintaining reliable electrical connection through the contact blades that engage with the mounting structure.
Solution Approach 2:
The fuse unit is extracted as a separate, removable component from the transformer system. The fuse element and contact blades are taken out as an integrated unit that can be easily removed through the aperture in the tank flange, eliminating the need to disconnect the transformer or drain dielectric fluid for fuse replacement.
2Ease of operation
If canister fuses are used to allow in-field replacement, then fuse replacement becomes easier, but the fuses are susceptible to arcing in high voltage applications and contamination
Solution Approach 1:
The fuse element is enclosed within a dielectric fluid-filled environment within the transformer tank. The dielectric fluid provides an inert, arc-quenching atmosphere that prevents arcing during fuse operation and replacement. This eliminates the arcing susceptibility of air-mounted canister fuses while maintaining easy in-field replacement capability.
Solution Approach 2:
The fuse unit incorporates an insulative sheath that encases the fuse element and provides electrical insulation. This sheath protects the fuse element from contamination while allowing the fuse to be easily inserted and removed through the aperture in the tank flange, combining protection with ease of replacement.
3Stability of the object's composition
If hardwired connections are used inside the transformer tank, then electrical connections are stable, but fuse replacement requires transformer disconnection and moving to a repair shop
Solution Approach 1:
The electrical connection system transitions from static hardwired connections to a dynamic, removable connection system. The contact blades on the fuse unit engage with corresponding contacts in the tank flange mounting structure, providing stable electrical connection during operation while allowing easy disengagement for fuse replacement. This dynamic connection maintains electrical stability when connected but enables simple field replacement.
4Ease of operation
If the fuse element is exposed for easy replacement, then replacement is simpler, but the fuse element is susceptible to contamination and arcing
Solution Approach 1:
An insulative sheath encases the fuse element, providing protection from contamination and arc quenching while allowing the entire fuse unit to be easily inserted and removed through the aperture in the tank flange. The sheath maintains electrical insulation and protects the fuse element during handling and replacement operations.
Solution Approach 2:
The dielectric fluid acts as an intermediary between the fuse element and the external environment. It provides arc quenching, electrical insulation, and contamination protection while allowing the fuse unit to be easily replaced through the aperture. The dielectric fluid mediates between the need for exposed contacts and the need for protection.
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
Facilitates easy replacement of current-limiting fuses in high-voltage applications without draining dielectric fluid, reducing arcing risks and contamination, and maintaining electrical integrity.
Implementation Method 1
The fuse element can include a sacrificial element that melts in response to overcurrent and opens at least a portion of a circuit that extends across the draw-out fuse
Implementation Method 2
Liquid-filled distribution transformers, including, for example, ANSI market distribution transformers, often use current-limiting fuses that are positioned under a dielectric fluid, such as, for example, oil
Data Source
AI summary
A current-limiting fuse for an electronic apparatus, such as, for example, a transformer. The fuse can be withdrawable under a liquid insulating medium, such as oil, and is capable of being replaceable in the field. The fuse can include a fuse element that is encased within an electrically insulative sheath. Additionally, a plurality of contact blades can extend from a lower portion of the fuse and be securely engaged with contact clips that are in electrical communication with one or more components of the electronic apparatus. The contact blades can be positioned within a dielectric insulating medium while a reminder of the fuse between the contact blades and the enclosure can be positioned within an air gap. Further, the contact blades can accommodate seating of the fuse within the enclosure and/or an associated canister.