Ribbed Bus Bar for AC Current with Segmented Cooling Gaps
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Solution Overview
Problem
The existing bus bars for conducting alternating current experience increased resistance and power losses due to the 'skin effect,' which becomes more pronounced at higher AC frequencies, leading to elevated temperatures and inefficiencies, especially in traction inverters and wireless charging systems.
Innovation Solution
A bus bar design featuring multiple parallel ribs with gaps between them for airflow, along with electrically conductive and insulating spacers for attachment and support, optimizing current distribution and reducing resistance and temperature through improved convective airflow and thermal radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a solid cross section bus bar is used to conduct AC current, then the current carrying capability is sufficient, but the AC resistance increases due to skin effect at high frequencies
Solution Approach 1:
The bus bar is divided into multiple parallel conductive strips or ribs separated by gaps, transforming the solid cross-section into a segmented structure. This segmentation reduces the skin effect by limiting current paths to thinner sections, thereby reducing AC resistance and power losses while maintaining adequate current carrying capability through the combined effect of multiple strips.
2Productivity
If the bus bar operates at high AC frequency, then the power transmission efficiency is improved, but the skin effect causes increased AC resistance and power losses
Solution Approach 1:
The bus bar is divided into multiple parallel conductive strips or ribs separated by gaps, transforming the solid cross-section into a segmented structure. This segmentation reduces the skin effect by limiting current paths to thinner sections, thereby reducing AC resistance and power losses while maintaining adequate current carrying capability through the combined effect of multiple strips.
3Loss of energy
If multiple parallel ribs with gaps are used to reduce AC resistance, then power losses are reduced, but the manufacturing complexity increases
Solution Approach 1:
The bus bar is divided into multiple parallel conductive strips or ribs separated by gaps, transforming the solid cross-section into a segmented structure. This segmentation reduces the skin effect by limiting current paths to thinner sections, thereby reducing AC resistance and power losses while maintaining adequate current carrying capability through the combined effect of multiple strips.
Solution Approach 2:
Multiple individual conductive strips are combined into a single integrated bus bar assembly that functions as one electrical component. The strips are positioned and secured together using insulating spacers and fastening mechanisms, creating a unified structure that provides both electrical functionality and mechanical stability while maintaining the beneficial segmented current paths.
4Speed
If the bus bar operates at high frequency AC, then the current density concentrates at the surface, but this causes increased AC resistance and temperature rise
Solution Approach 1:
The bus bar is divided into multiple parallel conductive strips or ribs separated by gaps, transforming the solid cross-section into a segmented structure. This segmentation reduces the skin effect by limiting current paths to thinner sections, thereby reducing AC resistance and power losses while maintaining adequate current carrying capability through the combined effect of multiple strips.
Solution Approach 2:
The gaps between the conductive strips, which initially appear as structural weaknesses, are utilized as beneficial cooling channels. These gaps allow air flow to pass through the bus bar assembly, providing passive convective cooling that removes heat generated by resistive losses and reduces operating temperature, thereby converting the structural segmentation into a thermal management advantage.
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 ribbed bus bar design reduces AC resistance and power losses, lowers operating temperatures, and provides a more efficient and compact solution with improved cooling, achieving performance comparable to on-board chargers.
Implementation Method 1
gaps between the strips allow air flow to take place. Thus losses are reduced and temperature is lowered both by reduced losses and by improved convective air flow
Implementation Method 2
temperature is lowered both by reduced losses and by improved convective air flow and thermal radiation
Implementation Method 3
In a bus bar for conducting an alternating current, the AC current tends to concentrate closer to the surface of the bus bar. That is, the current density is higher towards the outer surfaces of the bus bar and lower towards the center of the bus bar.
Data Source
AI summary
A bus bar for use in conducting an alternating current may comprise multiple substantially parallel ribs and an electrically conductive attachment feature. Each rib may include a first and second end. Each rib may be provided for conducting a substantially equal portion of the current. The ribs may be spaced apart to provide gaps therebetween for airflow through the gaps. The electrically conductive attachment feature may connect the first ends of the plurality of ribs, and may be provided for attaching the plurality of ribs to an electrical component. An electrically insulating spacer may be located between at least two of the ribs, contacting and providing physical support to those ribs.