Medium-Frequency Transformer Dry Core Tank Design
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Solution Overview
Problem
Liquid- or gel-insulated medium frequency transformers with dry cores face challenges in avoiding high loop currents and electrical breakdown due to the induction of electric fields in the tank, which is exacerbated by the use of dielectric materials that do not effectively distribute electric fields, leading to potential corona discharge and breakdown.
Innovation Solution
A transformer tank with a weakly-conductive layer comprising fibers embedded in an impregnating material, providing a specific resistance range that minimizes induced eddy currents and maintains the electric field within the insulating liquid or gel, thereby preventing corona discharge and breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the tank is made from dielectric material to avoid induction of high currents, then the induction of currents in the tank is avoided, but the electric field distribution is poor leading to corona discharge and breakdown
Solution Approach 1:
The tank wall is constructed as a composite structure with an inner layer of dielectric material (for insulation) and an outer layer of weakly-conductive material (for electric field distribution). This composite design combines the advantages of both materials: the dielectric layer prevents current induction while the weakly-conductive layer ensures proper electric field distribution, preventing corona discharge and electrical breakdown.
2Strength
If the tank is made from metallic material to provide structural strength, then the mechanical strength is improved, but high loop currents are induced in the tank
Solution Approach 1:
The tank employs a composite wall structure where the inner dielectric layer prevents current induction by breaking the conductive path, while the outer weakly-conductive layer provides controlled conductivity for electric field management. This composite approach maintains structural strength while eliminating harmful loop currents.
3Reliability
If the tank wall is made from highly conductive material to dissipate electric field, then the electric field distribution is improved, but induced eddy currents increase causing losses
Solution Approach 1:
The tank wall uses material with specifically optimized weak conductivity (intermediate conductivity between dielectric and conductor). This parameter optimization allows sufficient electric field distribution capability while limiting eddy current formation, achieving a balance between field control and energy loss minimization.
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
The weakly-conductive tank design effectively reduces the occurrence of corona discharge and electrical breakdown, maintaining the electric field within the insulating medium and minimizing losses from induced currents, while avoiding the use of expensive and heavy materials.
Implementation Method 1
the induction of high loop currents in the tank, the tank must not form a loop of high electric conductivity around the core
Implementation Method 2
maintains the electric field within the insulating liquid or gel, thereby preventing corona discharge and breakdown
Data Source
AI summary
A transformer is provided, which includes a tank having an enclosed volume with an insulating material, the tank including at least one channel extending through the tank, wherein the interior of the at least one channel is separated from the enclosed volume of the tank by a channel wall. A transformer core is provided outside of the enclosed volume, including at least one core leg extending through the tank via the at least one channel. At least one coil is located inside the enclosed volume, the coil being wound about the at least one channel, the tank has an inner wall or outer wall including a weakly-conductive layer, which includes fibers embedded in an impregnating material.