Laminated Bus Bar Design for Power Conversion Apparatus
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Solution Overview
Problem
The challenge is to reduce heat generation in bus bars connecting power semiconductor and smoothing capacitor modules while minimizing parasitic inductance, which hinders effective heat transfer and downsizing of power conversion apparatus for hybrid and electric vehicles.
Innovation Solution
The solution involves a power conversion apparatus design with laminated bus bars and insulation to reduce inductance and heat generation, where the bus bars are configured to cancel magnetic fields and use insulation to manage thermal stress, allowing for efficient heat transfer and compact module design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat generation in bus bar is reduced by increasing the distance between modules, then heat transfer between modules is suppressed, but parasitic inductance in bus bar increases notably
Solution Approach 1:
The bus bar structure transitions from a conventional single-plane configuration to a three-dimensional laminated structure with multiple layers stacked in the vertical dimension. This dimensional change allows the bus bar to achieve both low inductance (through close proximity of current paths in different layers) and reduced heat generation (through optimized current distribution and increased surface area for heat dissipation), effectively resolving the contradiction between these two parameters.
Solution Approach 2:
The bus bar employs a composite structure consisting of multiple conductive layers (first and second bus bars) with insulating material positioned between them. This composite configuration enables the system to simultaneously achieve low parasitic inductance through the laminated conductive paths and reduced heat generation through the insulating material that manages thermal stress and heat distribution, thus resolving the technical contradiction.
2Productivity
If modularization is implemented for power semiconductor module and smoothing capacitor module, then assembling productivity is improved and downsizing is achieved, but heat transfer between modules is reduced
Solution Approach 1:
The power conversion apparatus is divided into distinct modular units (power semiconductor module and smoothing capacitor module) that can be independently manufactured and assembled, improving productivity. The laminated bus bar structure bridges these modules, providing efficient thermal coupling that compensates for the thermal isolation effect of modularization, thus resolving the contradiction between productivity improvement and heat transfer reduction.
Solution Approach 2:
The laminated bus bar structure acts as an intermediary element between the power semiconductor module and the smoothing capacitor module. It not only provides electrical connection but also serves as a thermal pathway that facilitates heat transfer between modules, thereby resolving the contradiction where modularization improves productivity but reduces heat transfer efficiency.
3Volume of stationary object
If downsizing is pursued for power conversion apparatus, then effect of heat transfer between modules is reduced, but it is required to lower heat generation of each module
Solution Approach 1:
The laminated bus bar structure utilizes the vertical dimension by stacking multiple conductive layers, which increases the effective surface area for heat dissipation without increasing the horizontal footprint. This allows the apparatus to be downsized while maintaining or even improving heat generation characteristics, as the multi-layer configuration provides enhanced thermal management within a compact volume.
Solution Approach 2:
The composite structure of laminated conductive layers with insulating material between them enables efficient heat management in a compact form. The insulating material manages thermal stress and directs heat flow, while the conductive layers provide multiple pathways for heat dissipation, allowing downsizing without compromising heat generation control.
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 suppresses heat transfer between modules, enabling the downsizing of power conversion apparatus while maintaining low parasitic inductance, thus improving productivity and efficiency.
Implementation Method 1
the bus bars are configured to cancel magnetic fields
Implementation Method 2
use insulation to manage thermal stress
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
The power conversion apparatus includes an inverter circuit which converts a DC current into an AC current and have a U-phase, V-phase, and w-phase power semiconductor modules, and a capacitor module for smoothing the DC current. Each of the power semiconductor modules is configured separately and connected to a first bus bar. The capacitor module includes a case for containing a capacitor cell, a sealing material for sealing the capacitor cell, and a second bus bar which is connected to the capacitor cell in the sealing material and a portion of which protrudes from a surface of the sealing material. The first bus bar is configured with a first positive side bus bar, a first negative side bus bar, and a first insulation member arranged between the first positive side bus bar and the first negative side bus bar. The first bus bar includes a first to third terminals to which the U-phase, V-phase, and W-phase power semiconductor modules are connected, respectively, and a fourth terminal connected to a terminal of the second bus bar protruding from a surface of the sealing material of the second bus bar.