Ground-Switched EMC Capacitors in Isolated DC Voltage Converters
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Solution Overview
Problem
Electrically driven vehicles face radio-frequency interference issues due to the coupling of high-frequency signals into vehicle metal structures, which are hazardous and violate electromagnetic compatibility (EMC) requirements, especially when capacitors used for interference suppression store significant energy that can be hazardous to humans.
Innovation Solution
A voltage converter design that uses a switching element to disconnect the capacitor from the vehicle ground, allowing safer handling and reducing the hazard potential by only allowing access to the capacitor's poles when unauthorized access is detected, and utilizing high-capacitance capacitors for improved interference suppression without compromising safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitor remains connected to the DC voltage grid after disconnection from ground, then energy is still stored and hazardous, but disconnecting the capacitor from ground prevents access to the stored energy
Solution Approach 1:
The patent implements preliminary disconnection of capacitors from ground before the vehicle enters a state where human contact is possible (stationary mode or charging mode). This preliminary action ensures that even if the DC voltage grid remains energized, the capacitors cannot discharge through the ground path, preventing electric shock hazards in advance
Solution Approach 2:
The patent introduces a ground connection as an intermediary safety mechanism. By controlling the connection between capacitors and ground rather than directly controlling capacitor charge/discharge, the system uses the ground path as a mediator to safely manage energy release, preventing direct human exposure to hazardous voltages
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 reduces the hazard potential of stored energy, enables the use of high-capacitance capacitors for better interference suppression, and ensures safety during vehicle operation and charging, while maintaining compliance with EMC requirements.
Implementation Method 1
there are legal specifications regarding the maximum amount of energy that may be stored capacitively in the DC voltage grid
Implementation Method 2
The connection between the capacitor and the ground terminal is routed via at least one switching element
Data Source
AI summary
The arrangement relates to a voltage transformer for transformation between a direct voltage at a direct voltage gate and a single-phase or multi-phase alternating voltage at an alternating voltage gate by temporal clocking of an electronic switching unit, via which each phase of the alternating voltage gate can be connected either to a positive pole or to a negative pole of the direct voltage gate. The positive pole and/or the negative pole of the direct voltage gate is connected via at least one capacitor to a ground connection. The ground connection can be connected to an external ground, and the connection between the capacitor and the ground connection is guided via at least one switch element. The arrangement also relates to a motor vehicle having the electric powertrain. A diagnosis arrangement includes a voltage source and monitors the state and function of a switching element.