EV Power System Isolation Resistance Measurement
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Solution Overview
Problem
Existing methods for measuring isolation resistance between a high voltage DC system and a vehicle chassis in electric vehicles are inadequate as they cannot distinguish between potential current paths from the positive and negative nodes to the chassis, making it difficult to diagnose reductions in isolation resistance.
Innovation Solution
A power management system that periodically measures the isolation resistance separately for the positive and negative nodes of the power system, using a processing circuitry and switches to determine if either resistance falls below a threshold, allowing for precise diagnosis of any reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to measure isolation resistance, then the measurement process is simple, but the measurement precision is insufficient because they cannot distinguish between current paths from positive and negative nodes
Solution Approach 1:
The patent segments the isolation resistance measurement into two separate measurements: one for the positive node to chassis path and another for the negative node to chassis path. This is achieved by using switches to isolate each node individually during measurement, allowing precise identification of which node has reduced isolation resistance without requiring complex additional hardware beyond the existing measurement system.
2Measurement precision
If separate measurements for positive and negative nodes are implemented, then the diagnosis accuracy improves, but the measurement time increases
Solution Approach 1:
The patent implements periodic measurement cycles where switches alternately connect the measurement circuit to the positive node and then to the negative node. This periodic switching allows both nodes to be measured in sequence during a single diagnostic cycle, achieving accurate identification of isolation resistance issues while minimizing total measurement time through efficient time-multiplexed operation.
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
Enables accurate and easy diagnosis of isolation resistance reductions, ensuring the electrical isolation between the power system and chassis remains effective, thereby preventing unwanted current flow.
Implementation Method 1
determining an insulation resistance of the battery with respect to the ground reference
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
This disclosure describes techniques for separately determining isolation resistances from nodes of a power system (12) of an electric vehicle, EV, to a chassis (18) of the EV. Processing circuitry (22) may determine a first isolation resistance between a first node of the power system (12) in the EV and a chassis (18) of the EV, determine a second isolation resistance between a second node of the power system (12) in the EV and the chassis (18) of the EV, determine that the first isolation resistance or the second isolation resistance is less than a threshold resistance, and output information based on the determination that the first isolation resistance or the second isolation resistance is less than the threshold resistance.