Power Conversion Device Leakage Current Suppression
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Solution Overview
Problem
Existing power conversion devices face challenges in suppressing leakage current, which can lead to machine deterioration and electrical shock, especially due to increased operating frequencies and parasitic capacitance, while conventional solutions often result in device upsizing or unintended increases in leakage current.
Innovation Solution
A power conversion device with a DC link filter circuit and LC filter circuit configuration, including Y-shaped capacitors and common mode choke coils, is implemented to reduce leakage current by creating a virtual neutral potential line and connecting common mode extraction circuits, which reduces impedance and effectively suppresses leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the impedance to common mode is increased by elongating the distance between ground potential and facing metal or inserting a high inductance common mode choke coil, then leakage current is suppressed, but the power conversion device becomes larger in size
Solution Approach 1:
The invention changes the electrical parameters of the existing device structure by connecting capacitors between the DC link and virtual neutral potential line, and inserting common mode coils in specific routes, thereby suppressing leakage current without physical expansion of the device
Solution Approach 2:
The invention introduces a virtual neutral potential line as an intermediary reference potential, and uses Y-shaped capacitors and common mode coils as mediator components to suppress leakage current while maintaining compact device structure
2Object-affected harmful factors
If a large-capacity capacitor is connected to ground potential to suppress electromagnetic noises at low frequency, then noise suppression is improved, but leakage current increases
Solution Approach 1:
Instead of connecting capacitors directly to ground potential, the invention uses Y-shaped capacitors connected between the DC link and a virtual neutral potential line as an intermediary, thereby suppressing electromagnetic noise without creating a direct leakage current path to ground
Solution Approach 2:
The invention segments the noise suppression function into specific routes: Y-shaped capacitors for electromagnetic noise suppression and common mode coils for leakage current suppression, allowing both functions to operate independently and effectively
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 achieves significant suppression of leakage current, with the maximum amplitude reduced to one-quarter of conventional configurations, while avoiding device upsizing and maintaining effective noise suppression.
Implementation Method 1
a first common mode coil inserted into a route from the first common mode current extraction circuit to a connection point of the Y-shaped capacitor in the DC link filter circuit; and a second common mode coil inserted into a route from the connection point of the Y-shaped capacitor to the second common mode current extraction circuit
Implementation Method 2
a DC link filter circuit that includes a Y-shaped capacitor connected between the DC link part and the virtual neutral potential line
Data Source
AI summary
A power conversion device includes: a first power conversion circuit that converts power inputted from outside and outputs the converted power to a second power conversion circuit connected to the first power conversion circuit via a DC link, which outputs the converted power to a load; smoothing capacitors provided in an output part of the first power conversion circuit and an input part of the second power conversion circuit; a first and second common mode current extraction circuits provided in an input part of the first power conversion and second power conversion circuits; and a virtual neutral potential line that connects the first and second common mode current extraction circuits; a DC link filter circuit that includes a Y-shaped capacitor connected between the DC link part and the virtual neutral potential line.