Parallel Sub-Bar Bus Bar Layout for Transformer AC Loss Reduction
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Solution Overview
Problem
Low-voltage DC-DC converters in eco-friendly vehicles experience significant AC loss due to high currents flowing through small-turn windings, leading to inefficiencies and increased costs, particularly in bus bars used in transformers.
Innovation Solution
A bus bar structure comprising multiple sub-bars arranged horizontally and connected in parallel, with varying widths to match resistances and impedances, minimizing AC loss while maintaining a core size and reducing manufacturing costs through an optimized design method that calculates sub-bar dimensions to achieve balanced current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bus bar with small number of turns is used in low-voltage high-current transformer, then the transformer structure is simplified and manufacturing cost is reduced, but AC loss increases significantly
Solution Approach 1:
The bus bar is divided into multiple sub-bars (first sub-bar, second sub-bar, third sub-bar, etc.) arranged in parallel. Each sub-bar carries a portion of the total current, and by optimizing their individual dimensions and arrangements, the AC loss is reduced while maintaining the simplified bus bar structure without requiring expensive Litz wires.
Solution Approach 2:
Different sub-bars are designed with different width dimensions adapted to their specific positions and current carrying requirements. The width of each sub-bar is optimized based on its location within the transformer core window, allowing local optimization of current distribution and AC loss reduction while maintaining overall structural simplicity.
2Ease of manufacture
If the width of sub-bars is made uniform, then manufacturing is simplified, but current distribution becomes uneven leading to increased AC loss
Solution Approach 1:
The sub-bars are designed with asymmetric width dimensions where each sub-bar has a different width optimized for its specific position and current carrying requirements. This asymmetric design ensures optimal current distribution across all sub-bars, minimizing AC loss while the widths are carefully controlled to remain within manufacturing tolerances for cost-effective production.
3Loss of energy
If more sub-bars are added to reduce AC loss, then AC loss decreases, but device complexity and manufacturing cost increase
Solution Approach 1:
Instead of using an excessive number of sub-bars which would increase complexity, the invention uses a optimized number of sub-bars (typically 3-5) with carefully designed dimensions. This partial action approach achieves sufficient AC loss reduction without over-complicating the bus bar structure, maintaining manufacturing feasibility.
Solution Approach 2:
The invention optimizes parameters such as the number of sub-bars, their width dimensions, and spacing to achieve the best balance between AC loss reduction and structural simplicity. By carefully selecting and adjusting these parameters, the bus bar structure achieves effective AC loss minimization while maintaining manageable complexity for mass production.
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 solution effectively minimizes AC loss, maintains uniform heat dissipation, and reduces the need for expensive Litz wires, enabling mass production of bus bars with improved efficiency and cost-effectiveness.
Implementation Method 1
conduction loss may occur in a winding due to a current, and is broadly classified as DC loss and AC loss
Implementation Method 2
the AC current flows through only a surface of the winding, and a depth from the surface of the winding to which a current may flow may vary according to a frequency
Data Source
AI summary
An aspect of the present disclosure provides a bus bar as a winding in a core of a transformer includes multiple sub-bars arranged horizontally and connected in parallel so as to minimize an AC current in the transformer, and the sub-bars have different widths and thus resistances or impedances with respect to a current flowing through the sub-bars are the same. Another aspect of the present disclosure provides a method of designing a bus bar for resistance or impedance matching between multiple sub-bars included in the bus bar to share a current to minimize an AC current in the transformer. Another aspect of the present disclosure provides a transformer, for a DC-DC converter for use in a vehicle, which is manufactured by the method of designing a bus bar.