Bus Bar Stray Capacitance for Radiation Noise Reduction
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Solution Overview
Problem
Conventional methods for preventing radiation noise in high-voltage cables used in hybrid and electric vehicles are inadequate and require alternative solutions as they rely on shield wires that may need replacement.
Innovation Solution
An electrically conductive path device utilizing two or three bus bars with a capacitance portion between facing surfaces to create stray capacitance, along with impedance matching portions, to prevent radiation noise by redirecting voltage changes and matching impedance, thereby reducing the likelihood of standing waves and noise emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If shield wires with braids are used to prevent radiation noise, then radiation noise is prevented, but the device complexity and cost increase
Solution Approach 1:
The invention extracts the essential function of noise prevention from the complex shield wire structure and implements it through a simplified bus bar configuration with controlled stray capacitance, eliminating the need for braids and grounding wires while maintaining the radiation noise prevention effect
Solution Approach 2:
The invention changes the electrical parameters by controlling the stray capacitance between bus bars through specific geometric configurations (spacing, surface area, length), thereby achieving noise cancellation without requiring additional shielding components
2Object-affected harmful factors
If shield wires with braids are used to prevent radiation noise, then radiation noise is prevented, but the manufacturing cost increases
Solution Approach 1:
The invention removes the expensive braid and grounding wire components from the noise prevention system, retaining only the essential bus bar structure with controlled stray capacitance, thereby significantly reducing manufacturing cost while maintaining noise prevention effectiveness
Solution Approach 2:
The invention uses simple, inexpensive bus bars with controlled geometric parameters instead of expensive shielded cables, achieving the same noise prevention function at a lower cost
3Device complexity
If bus bars with capacitance portion are used, then radiation noise is prevented and structure is simplified, but impedance matching becomes critical
Solution Approach 1:
The invention addresses impedance matching by carefully controlling geometric parameters of the bus bars (spacing, surface area, length) to achieve the desired stray capacitance value, thereby ensuring proper impedance matching while maintaining structural simplicity
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
The solution effectively cancels out radiation noise, prevents insulation breakdown, and maintains optimal impedance matching, offering a cost-effective and simple structure for noise reduction in electric vehicles.
Implementation Method 1
a capacitance portion for creating stray capacitance, wherein the capacitance portion is formed between facing portions of the bus bars
Implementation Method 2
by forming the impedance matching portions, output impedance of the inverter can be matched with input impedance of the motor
Data Source
AI summary
There is provided an electrically conductive path device which can prevent radiation noise. An electrically conductive path device includes three bus bars electrically connecting a motor unit to an inverter unit, capacitance portions creating stray capacitance and an insulator. In terms of the electrically conductive path device, switching operation of a semiconductor switch located inside an inverter of the inverter unit creates change in voltage which is transmitted to the bus bar corresponding to a path from the inverter to the motor. At that time, the change in voltage is not transmitted further to the motor but is transmitted to the bus bar corresponding to a path from the motor to the inverter via the capacitance portion formed between the facing portions, i.e. via the stray capacitance.