Element Unit Bus Bar Stray Inductance Reduction
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Solution Overview
Problem
In power control units, the increased stray inductance due to the self-inductance of bus bars connected to semiconductor modules leads to higher surge voltages and switching losses, particularly when the positive and negative electrode bus bars are drawn out from orthogonal semiconductor elements.
Innovation Solution
The element unit design includes a high side arm and low side arm element with conductors that face each other while spaced apart, with input/output conductors extending between them, reducing stray inductance through mutual magnetic flux offsetting and restraining conductor length, and allowing for efficient electrical connection and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the positive electrode side bus bar and the negative electrode side bus bar are drawn out from positions away from each other in the arrangement direction, then the electrical connection is simplified, but the total stray inductance of the series circuit increases due to self-inductance of each bus bar
Solution Approach 1:
The patent transitions from a one-dimensional linear arrangement of bus bars to a three-dimensional configuration where bus bars are stacked in the thickness direction. This dimensional change allows the positive and negative electrode bus bars to be positioned closer together spatially, reducing self-inductance while maintaining simplified electrical connection topology.
Solution Approach 2:
The patent implements a nested arrangement where the first bus bar and second bus bar are stacked in the thickness direction, with the third bus bar extending in the arrangement direction and connecting to both. This nesting configuration reduces the overall current loop area and minimizes stray inductance while preserving manufacturing simplicity.
2Loss of energy
If the bus bars are positioned close together to reduce stray inductance, then switching losses are reduced, but thermal interference between components increases
Solution Approach 1:
The patent segments the bus bar structure into multiple independent components (first bus bar, second bus bar, third bus bar) with distinct functional roles. This segmentation allows optimized positioning for electrical performance while maintaining thermal separation through the layered configuration in the thickness direction.
Solution Approach 2:
By utilizing the thickness direction for bus bar stacking, the patent achieves close proximity for electrical connection (reducing switching losses) while maintaining spatial separation in the planar direction (reducing thermal interference). This dimensional strategy decouples electrical and thermal considerations.
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 reduces stray inductance, minimizing surge voltages and switching losses, while also suppressing thermal interference and improving cooling performance by maintaining a compact form factor and reducing thermal resistance.
Implementation Method 1
reduces stray inductance through mutual magnetic flux offsetting
Data Source
AI summary
There is provided an element unit including high side arm and low side arm transistors, a conductor set formed by disposing a positive bus bar and a negative bus bar to face each other while spaced apart in a Z axis direction, and a first bus bar. The first bus bar extends in the Z axis direction between a first insulating substrate and a second insulating substrate and is electrically connected to copper plates of the first insulating substrate and the second insulating substrate.