EVSE Power Contact Weld Detection Using IMD Voltage Patterns
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Solution Overview
Problem
Existing electric vehicle charging systems face challenges in accurately detecting the welded condition of power contacts in high voltage DC contactors or relays (OGC) due to unreliable or missing auxiliary switch feedback, leading to safety hazards and downtime, particularly in systems with multiple DC outlets and shared power converter groups.
Innovation Solution
A software-based method using voltage pattern recognition through insulation monitoring devices (IMD) to detect welded power contacts in OGCs, employing predefined threshold comparisons and software algorithms to analyze voltage patterns without relying on auxiliary switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auxiliary switches are used to detect power contact state, then contact state monitoring is enabled, but reliability deteriorates due to unreliable or missing feedback
Solution Approach 1:
The patent introduces an intermediary detection mechanism using insulation monitoring device (IMD) voltage pattern analysis as a mediator between the power contacts and the control system. Instead of directly relying on faulty auxiliary switch feedback, the system uses voltage patterns measured by the IMD to indirectly detect the actual state of power contacts, thereby resolving the unreliability of direct auxiliary switch monitoring
Solution Approach 2:
The patent replaces the mechanical auxiliary switch system with an electrical measurement system. Instead of using mechanical switches that provide unreliable feedback, the system uses electrical voltage pattern measurement through the IMD to detect power contact states, substituting a more reliable electrical detection method for the faulty mechanical feedback system
2Measurement precision
If voltage pattern recognition method is implemented, then detection accuracy is improved, but device complexity increases due to software algorithms and threshold comparisons
Solution Approach 1:
The patent makes the insulation monitoring device (IMD) multi-functional by enabling it to perform both its traditional insulation monitoring function and the new power contact welded condition detection function. The same voltage measurement capability of the IMD is utilized for dual purposes, eliminating the need for separate dedicated detection hardware and reducing overall system complexity despite the sophisticated detection algorithm
Solution Approach 2:
The patent changes the parameter being measured from simple auxiliary switch position feedback to continuous voltage pattern parameters. By monitoring voltage magnitude and temporal patterns instead of discrete switch states, the system achieves higher detection accuracy. The software analyzes voltage parameters over time to distinguish between normal open contacts and welded contacts, transforming a binary detection problem into a continuous parameter analysis
3Reliability
If continuous monitoring is performed, then safety is improved, but energy consumption increases due to constant voltage pattern analysis
Solution Approach 1:
The patent achieves continuous monitoring of power contact conditions by utilizing the ongoing voltage measurements already being performed by the insulation monitoring device (IMD) during normal charging operations. The voltage pattern analysis is performed continuously on existing measurement data without requiring additional active sensing or extra energy-consuming monitoring cycles, thereby maintaining safety while minimizing additional energy consumption
Data Source
AI summary
A method and a system for determining a welded condition of power contacts in an Outgoing Coil within an Electric Vehicle Supply Equipment is provided. The method includes initiating a condition verification process based on a set of predefined conditions. Upon completion of the condition verification process, a voltage pattern recognition process is executed to generate a voltage pattern by superimposing voltage pulses onto a power circuit of the EVSE. The method further includes capturing an outlet voltage influenced by the voltage pulses superimposed on the power circuit. The method further includes determining a welding status of the power contacts based on the captured outlet voltage. The method further includes controlling an operational state of an associated charging outlet of the EVSE based on the determined welding status of the power contacts corresponding thereto.