Grounded DC Source Assembly for Inverter EMI Suppression
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Solution Overview
Problem
Existing power inverter systems in electric and hybrid electric vehicles generate stray AC currents, leading to undesirable electromagnetic interference (EMI) radiation due to inherent capacitance and inductance in components, which is exacerbated by the separation of power inverter chassis and DC sources, increasing fabrication complexity and cost.
Innovation Solution
Integrating a DC source assembly with capacitors directly coupled between the vehicle ground and the positive and negative DC source terminals within a housing grounded to the vehicle chassis, providing a low impedance pathway for common mode currents to reduce EMI radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If filtering capacitors are located away from the power modules and IGBT devices, then the chassis and DC source can be separated for easier assembly, but the loop area increases and EMI radiation is enhanced
Solution Approach 1:
The patent merges the filtering capacitors with the DC source assembly by providing capacitors that are electrically coupled to the DC source terminals and physically integrated into the DC source housing. This combining of filtering function with the power source eliminates the need for separate capacitor mounting locations, thereby reducing loop area and EMI radiation while maintaining assembly ease.
2Object-generated harmful factors
If filtering capacitors are integrated within the DC source assembly near the common mode current source, then EMI radiation is reduced, but fabrication complexity and cost increase
Solution Approach 1:
The DC source assembly is designed to serve multiple functions: it provides power storage, electrical connection, and electromagnetic filtering. The housing serves both as a structural enclosure and as a mounting structure for the capacitors. This multi-functionality reduces the need for additional dedicated filtering components and simplifies the overall fabrication process.
Solution Approach 2:
The DC source assembly integrates its own filtering capability through capacitors that are electrically coupled to its terminals and housed within its structure. This self-service approach eliminates the need for separate filtering systems and reduces overall system complexity while effectively reducing EMI radiation at its source.
3Object-generated harmful factors
If filtering capacitors are connected to busbar and chassis surfaces, then EMI filtering is provided, but connection reliability is challenging and cost increases
Solution Approach 1:
The filtering capacitors are integrated into the DC source assembly with electrical connections made at the DC source terminals rather than requiring separate connections to busbars and chassis surfaces. This merging of electrical connection points improves reliability by reducing the number of connection interfaces while maintaining effective EMI filtering.
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 significantly decreases the current loop area and associated EMI radiation, simplifying fabrication and reducing electromagnetic interference, while maintaining cost-effectiveness by utilizing capacitors closer to the source of common mode currents.
Implementation Method 1
a first capacitor having a first electrode electrically coupled to the conductive member and a second electrode electrically coupled to the first terminal and a second capacitor having a first electrode electrically coupled to the conductive member, and having a second electrode electrically coupled to the second terminal
Data Source
AI summary
Embodiments of DC source assemblies of power inverter systems of the type suitable for deployment in a vehicle having an electrically grounded chassis are provided. An embodiment of a DC source assembly comprises a housing, a DC source disposed within the housing, a first terminal, and a second terminal. The DC source also comprises a first capacitor having a first electrode electrically coupled to the housing, and a second electrode electrically coupled to the first terminal. The DC source assembly further comprises a second capacitor having a first electrode electrically coupled to the housing, and a second electrode electrically coupled to the second terminal.