Ring Capacitor Busbar Layout for Low-Inductance Inverter Connection
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Solution Overview
Problem
Ring capacitors in power electronics devices, particularly in vehicle drive power inverter devices, experience high inductance due to the spacing of connection tabs, leading to switching overvoltages and potential malfunctions when connected to semiconductor switches.
Innovation Solution
A capacitor arrangement with busbars aligned axially within the capacitor's cavity, connecting multiple capacitor windings in parallel to reduce inductance, and featuring a capacitor holder with thermal expansion compensation to enhance reliability and reduce parasitic inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If terminal lugs are distributed along the circumference of the ring capacitor, then the capacitor can be connected to semiconductor switches, but the spacing between terminal lugs increases the inductance of the capacitor
Solution Approach 1:
The patent transitions from a two-dimensional circumferential distribution of terminal lugs to a three-dimensional arrangement where busbars are positioned axially within the capacitor's interior space. This dimensional change allows the busbars to overlap in the axial direction, creating shorter and more direct electrical connection paths that reduce inductance while maintaining connectivity to semiconductor switches.
Solution Approach 2:
The patent places the busbars inside the interior space of the ring capacitor, nesting the connection elements within the capacitor structure itself. This nesting allows the busbars to be positioned optimally for low-inductance connections without increasing the external footprint of the capacitor, and enables direct connection to terminal lugs through the capacitor's interior.
2Adaptability or versatility
If terminal lugs are spaced apart to allow connections, then the capacitor can be connected to external circuits, but the connection areas increase the inductance leading to switching overvoltages
Solution Approach 1:
The patent uses axial positioning of busbars within the capacitor's interior space to create shorter connection paths. By overlapping busbars in the axial direction and connecting them to terminal lugs through the interior, the connection length is minimized, which reduces inductance and consequently reduces switching overvoltages while maintaining full connection capability.
Solution Approach 2:
The busbars act as intermediary elements between the terminal lugs and external circuits. By introducing these intermediate connection elements positioned within the capacitor's interior space, the patent creates optimized connection paths that reduce inductance and mitigate switching overvoltages while maintaining adaptability to external circuit connections.
3Device complexity
If conventional ring capacitors are used with distributed terminal lugs, then the capacitor structure is simple, but the high inductance causes malfunctions or failures in power electronic devices
Solution Approach 1:
The patent nests busbars within the interior space of the ring capacitor, creating a compact integrated structure. This nesting approach maintains the simplicity of the overall capacitor structure while internally optimizing the connection geometry to reduce inductance and improve reliability of power electronics devices.
Solution Approach 2:
The patent introduces axial positioning of busbars within the capacitor's interior space, adding a third dimension to the connection geometry. This dimensional change enables shorter connection paths and reduced inductance without significantly increasing the external complexity or footprint of the capacitor structure.
Data Source
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AI summary
The invention relates to a capacitor assembly (KA), comprising: - a capacitor (KD), which extends at least partly around a space (HR), the capacitor (KD) having first, positive-voltage-side power terminals (SA1) and second, negative-voltage-side power terminals SA2); - a first bus bar (S1), which is electrically connected to the first power terminals (SA1); - a second bus bar (S2), which is electrically connected to the second power terminals (SA2); wherein the first bus bar and the second bus bar extend parallel or obliquely to an end of the space (HR). The invention further relates to a vehicle drive power-electronics device having a capacitor assembly (KA) of this type.