Composite Safety Capacitor Layout for Stable Inverter Impedance Measurement
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Solution Overview
Problem
Existing inverter devices suffer from unstable impedance measurement due to high leakage current and impedance drift caused by single-type safety capacitors, affecting precision and reliability.
Innovation Solution
Inverter devices are configured with safety capacitors comprising a first and second sub-capacitor, where each sub-capacitor is a different type, such as a multi-layer ceramic capacitor and a film capacitor, connected in parallel or series, to reduce leakage current and impedance drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-type safety capacitor (e.g., multi-layer ceramic capacitor or film capacitor) is used, then the inverter device can be manufactured with simpler structure and lower cost, but the capacitor leakage current is high causing impedance drift and unstable measurement voltage
Solution Approach 1:
The patent combines multiple types of capacitors (multi-layer ceramic capacitor and film capacitor) into a single safety capacitor assembly. This merging approach allows the system to benefit from the low leakage current characteristics of film capacitors while maintaining the compact size and high-frequency performance of ceramic capacitors, thereby stabilizing impedance measurement without significantly increasing structural complexity
Solution Approach 2:
The safety capacitor is constructed using composite material principles by integrating different capacitor technologies (ceramic and film) into a unified structure. This composite approach leverages the complementary strengths of each capacitor type to achieve both low leakage current and stable impedance characteristics, resolving the contradiction between measurement precision and device complexity
2Object-affected harmful factors
If high capacitance safety capacitors are used to suppress common-mode interference, then the interference suppression capability is improved, but the leakage current increases causing impedance drift during measurement
Solution Approach 1:
The patent optimizes the capacitance parameters of the composite safety capacitor by carefully selecting the capacitance values of both the ceramic and film capacitor components. This parameter optimization allows the system to achieve adequate common-mode interference suppression while maintaining low leakage current, preventing impedance drift during measurement processes
3Measurement precision
If the safety capacitor impedance is reduced to improve measurement voltage stability, then the measurement precision is improved, but the leakage current increases causing safety issues
Solution Approach 1:
By merging ceramic and film capacitors in the safety capacitor assembly, the system achieves a balanced electrical characteristic where the equivalent impedance is optimized for measurement stability while the combined leakage current remains low due to the dominant low-leakage film capacitor component
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 stabilizes capacitor voltage, improving the precision and reliability of impedance measurement while maintaining effective DC to AC inversion.
Implementation Method 1
each of the first safety capacitor and the second safety capacitor is formed of a first sub-capacitor and a second sub-capacitor
Data Source
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AI summary
An inverter device, an electric power assembly system and a vehicle are disclosed. The inverter device is configured to invert input DC and output single-phase AC, and the inverter device includes: safety capacitors, including a first safety capacitor arranged between a live wire output end and a ground wire of the single-phase AC, and a second safety capacitor arranged between a neutral wire output end and the ground wire of the single-phase AC, the first safety capacitor being identical to the second safety capacitor; wherein each of the first safety capacitor and the second safety capacitor is formed of a first sub-capacitor and a second sub-capacitor.