Concentric Tubular Bushing for Transformer Heat Management
Solution Overview
Problem
High-current transformer bushings face challenges in managing heat losses due to the skin effect, which leads to high current density and heat generation, particularly when routing electrical conductors through transformer tank housings, necessitating expensive materials and cooling solutions.
Innovation Solution
A high-current transformer bushing design featuring two concentric tubular partial conductors with a radial crossover and twisted connecting conductor pairs, ensuring even current distribution and reduced heat generation by utilizing transformer oil for cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single thick-walled tubular conductor is used to carry high current, then the current conduction capability is improved, but the skin effect causes excessive heat generation and current density concentration at the outer surface
Solution Approach 1:
The single thick-walled tubular conductor is divided into two separate thin-walled tubular conductors. Each conductor carries a portion of the total current, and their combined cross-sectional area provides equivalent or superior current conduction capability. This segmentation eliminates the skin effect problem because the current distributes more evenly across the thinner walls of each tube.
Solution Approach 2:
One tubular conductor is positioned inside the other, creating a nested configuration. The inner conductor has a smaller diameter and is surrounded by the outer conductor. This nested arrangement allows both conductors to be closely coupled while maintaining their individual current paths, effectively utilizing space and reducing overall dimensions.
2Loss of energy
If two tubular conductors are used to distribute current and reduce heat loss, then heat generation is reduced, but the device complexity and spatial requirements increase
Solution Approach 1:
The nested configuration of one conductor inside the other minimizes the overall spatial footprint while accommodating both conductors. This eliminates the need for separate routing paths and reduces the complexity of conductor arrangement compared to parallel placement.
Solution Approach 2:
The two conductors are electrically connected at their ends through twisted connecting conductor pairs, merging them into a single functional current path. This connection method simplifies the overall structure by integrating the conductors into a unified assembly rather than treating them as separate components.
3Volume of moving object
If the conductor wall thickness is reduced to fit through the transformer housing, then the space requirements are improved, but the current density increases and heat generation worsens
Solution Approach 1:
Instead of using one thick-walled conductor that would be too large for the housing, the conductor is segmented into two thin-walled conductors. Each individual conductor has sufficient current-carrying capacity for its assigned current portion, and together they provide the total required current conduction capability while fitting through the housing.
Solution Approach 2:
The solution transitions from a single-dimension approach (one thick conductor) to a two-dimension approach (multiple thin conductors arranged in space). By utilizing the radial dimension to nest conductors and the axial dimension for their arrangement, the design achieves compact dimensions suitable for housing passage while maintaining adequate current conduction capability through the combined cross-sectional area of multiple conductors.
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 design effectively distributes current evenly between the partial conductors, minimizing heat generation and allowing for a compact, efficient, and cost-effective solution to manage heat losses within the transformer bushing.
Implementation Method 1
cooling the conductor with transformer oil
Implementation Method 2
cooling the conductor with transformer oil
Implementation Method 3
the current through such a supply line pushes through the skin effect to the outer area of the conductor
Implementation Method 4
an alternating current flowing through a conductor generates eddy currents inside the conductor that oppose the generator current
Implementation Method 5
the magnetic field induced by the alternating current induces stronger eddy currents inside the conductor than at the edge
Implementation Method 6
the crossing has twisted connecting conductor pairs between inner and outer sections in the axial direction
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
The bushing (18) has a fixing unit (32) designed as a twin conductor flange for fixing at a power station transformer, and an electrical conductor (30) for bushing through a transformer tank housing. An electrical insulator (26) is guided around the electrical conductor. The electrical conductor has two tubular partial leads (42, 44) that are arranged concentrically and guided into one other. One of the leads exhibits inner sections (48, 50) within the other partial lead, and outer sections (46, 52) outside the other partial lead along a flow path by radial crossings.