Transformer Winding Fusible Section Overcurrent Protection
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Solution Overview
Problem
The increased efficiency requirements for medium voltage/low voltage transformers, driven by regulations like EU N°548/2014 and standards such as EN 50588, lead to reduced ohmic resistance and current density in windings, causing fuses to malfunction during insulation faults, resulting in overheating and potential transformer bursting or fire.
Innovation Solution
Incorporating fusible sections within the medium voltage windings made of conductors with increased linear resistance, such as varnished aluminum, to promote local heating and short-circuiting in the event of abnormal currents, ensuring timely fault detection and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the ohmic resistance of windings is reduced to improve efficiency, then energy efficiency is improved, but the fuse malfunction risk increases due to insufficient current for proper operation
Solution Approach 1:
The patent applies local quality by introducing fusible sections with specifically engineered properties at critical locations within the winding, rather than changing the entire winding's characteristics. These local sections have higher linear resistance and lower melting point, creating localized weak points that preferentially fail under abnormal current conditions, thereby resolving the contradiction between low overall resistance and reliable protection.
Solution Approach 2:
The patent changes physical parameters by modifying the linear resistance and material composition of specific sections within the winding. The fusible sections have deliberately altered parameters (higher resistance, lower melting point) compared to the main winding conductor, enabling them to respond to abnormal current conditions and trigger protection mechanisms while the overall winding maintains low ohmic losses for efficiency.
2Loss of energy
If the current density in conductors is reduced to improve efficiency, then energy efficiency is improved, but the fault detection capability deteriorates because abnormal currents do not reach sufficient levels to trigger fuses
Solution Approach 1:
The patent introduces localized fusible sections with distinct properties within the winding structure. These sections have higher linear resistance and lower melting point compared to the main conductor, creating localized zones that preferentially heat up and fail under abnormal current conditions, thereby enabling reliable fault detection even when overall current density is reduced for efficiency.
Solution Approach 2:
The patent segments the winding into functional zones: the main winding conductor optimized for low losses and the embedded fusible sections optimized for protection. This segmentation allows each part to perform its specialized function - the main conductor maintains efficiency while the fusible sections provide sensitive fault detection through their deliberately engineered higher resistance and lower melting characteristics.
3Reliability
If fusible sections with increased linear resistance are added to promote local heating, then protection reliability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the protection function directly into the winding structure by integrating fusible sections within the conductor itself, rather than adding separate external protection devices. This merging combines the current-carrying function and the protection function into a single integrated structure, reducing overall device complexity while improving protection reliability.
Solution Approach 2:
The fusible sections provide self-service protection by automatically responding to abnormal current conditions through localized heating and failure. The sections are self-actuating - they detect overcurrent conditions through their higher linear resistance, generate the necessary thermal response, and trigger protection without requiring external sensors or control systems, thereby simplifying the overall device architecture.
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 solution enhances the reliability of protection devices by ensuring that abnormal currents lead to a short-circuit of a significant portion of the winding, triggering the fuse and preventing overheating and potential transformer failure, thus mitigating the risks of bursting or fire.
Implementation Method 1
at least one fusible section, made with a conductor whose characteristics induce a linear resistance increased with respect to the linear resistance of the conductor of the rest of the winding, so as to cause destructive local heating
Data Source
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AI summary
The invention relates to a single-phase or polyphase electrical device, comprising for each phase at least one electrical winding consisting of a winding of several turns of an electrical conductor, characterized in that this winding includes at least one fusible section (25), made with a conductor whose characteristics induce a linear resistance increased compared to the rest of the winding (21), so as to cause destructive local heating and promote a short circuit in this section (25) in the event of a sustained passage of an abnormal current in the winding.