Power Module-Capacitor Busbar Layout for Low-Inductance Conversion
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Solution Overview
Problem
Existing power conversion devices face issues of increased cost, size, and losses due to high path inductance and heat generation, necessitating expensive semiconductor elements and cooling mechanisms, which are exacerbated by the use of film capacitors with low capacitance per unit volume and busbars forming parallel flat-plates.
Innovation Solution
The power conversion device employs a configuration where power modules are opposed to the side surfaces of capacitor elements, with busbars having opposed plate-shape portions to evenly distribute current, reducing self-inductance and path inductance, allowing for the use of less expensive semiconductor elements and eliminating the need for additional cooling structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If film capacitors are used as smoothing capacitors, then high rated voltage and excellent durability are achieved, but low capacitance per unit volume results in increased device size
Solution Approach 1:
The patent combines multiple capacitor elements into a single integrated smoothing capacitor assembly, reducing the overall device volume while maintaining the necessary capacitance. The busbar structure integrates the connection function with the cooling function, merging multiple components into fewer elements.
Solution Approach 2:
The patent arranges capacitor elements and busbars in a three-dimensional configuration where busbars are positioned between capacitor elements rather than only on the outer surfaces. This spatial optimization reduces the device footprint while maintaining electrical connectivity and heat dissipation pathways.
2Reliability
If conventional busbar arrangements are used, then connection is achieved, but high path inductance causes surge voltage to exceed semiconductor element withstand voltage
Solution Approach 1:
The patent employs asymmetric busbar configurations where busbars of different polarities are arranged in opposition to each other between capacitor elements. This asymmetric arrangement creates opposing magnetic fields that reduce mutual inductance and path inductance, protecting semiconductor elements from surge voltage without requiring overly complex symmetric structures.
Solution Approach 2:
The patent converts the potentially harmful inductive effects into beneficial opposing magnetic fields by arranging positive and negative busbars in opposition. The magnetic fields generated by current flow in opposite directions through adjacent busbars cancel each other out, reducing overall path inductance and protecting semiconductor elements.
3Reliability
If path inductance is decreased by conventional methods, then surge voltage is reduced, but device size and cost increase due to expensive materials and additional cooling mechanisms
Solution Approach 1:
The patent merges the electrical connection function and thermal management function into a single integrated busbar structure. The busbars serve dual purposes: providing low-inductance electrical connectivity and acting as heat sinks for cooling capacitor elements, thereby reducing device size while maintaining reliability.
Solution Approach 2:
The busbars are designed with multi-functionality, serving as both electrical conductors with optimized inductance characteristics and as thermal management components. This universal design reduces the need for separate cooling mechanisms and expensive materials, downsizing the overall device while protecting semiconductor elements.
4Ease of operation
If busbars are disposed between adjacent capacitor elements to form parallel flat-plates, then path inductance is decreased, but heat transmission to capacitor elements occurs and machining cost increases
Solution Approach 1:
The patent converts the potentially harmful heat transmission from busbars to capacitor elements into a beneficial cooling effect. By positioning busbars in direct thermal contact with capacitor elements, the busbars act as heat sinks that draw heat away from the capacitor elements, reducing their operating temperature while maintaining the low inductance configuration.
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 configuration results in a smaller, cost-effective power conversion device with reduced losses and no additional cooling requirements, enabling high-speed operation using wide bandgap semiconductors and film capacitors.
Implementation Method 1
one or each of the first busbar and the second busbar has, as a connection member connecting the power module and a corresponding one of the first electrode or the second electrode to each other, an opposed plate-shape portion opposed only to an opposed portion of the side surface of the element body portion opposed to the power module
Data Source
AI summary
The power conversion device includes: a power module; a plurality of capacitor elements each having an element body portion, a first electrode, and a second electrode; a first busbar connecting the first electrode and the power module; and a second busbar connecting the second electrode and the power module. The power module is disposed so as to be opposed to a side surface of the element body portion of only one of the capacitor elements. One or each of the first busbar and the second busbar has, as a connection member connecting the power module and a corresponding one of the first electrode or the second electrode to each other, an opposed plate-shape portion opposed only to an opposed portion of the side surface of the element body portion opposed to the power module.