EVSE Outlet Contact Weld Detection via IMD Voltage Pulses
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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 risks and downtime, especially 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 identify abnormal 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 replaces the mechanical auxiliary switch system with an electronic detection method using the insulation monitoring device. Instead of relying on mechanical auxiliary switches to detect power contact state, the system uses the IMD to measure impedance changes in the power circuit that occur when contacts are welded, thereby eliminating the reliability issues of mechanical feedback systems.
Solution Approach 2:
The patent introduces the insulation monitoring device as an intermediary to detect power contact state. The IMD measures the impedance of the power circuit, and changes in impedance indicate whether contacts are welded or functioning normally. This intermediary measurement approach provides reliable detection without depending on auxiliary switch feedback.
2Measurement precision
If software-based voltage pattern recognition is implemented, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the insulation monitoring device multi-functional by enabling it to perform both its original insulation monitoring function and the new power contact welded detection function. The same hardware resource (IMD) is used for dual purposes, avoiding the need for additional dedicated detection hardware and thus limiting the increase in device complexity.
Solution Approach 2:
The system uses its own existing operational voltage pulses and the natural electrical characteristics of the power circuit to perform welded detection. The IMD continuously monitors the circuit during normal operation, and the detection algorithm analyzes voltage patterns that already exist in the system, eliminating the need for separate test equipment or additional system components.
3Productivity
If multiple DC outlets with shared power converters are used, then system efficiency improves, but safety risks increase due to undetected welded contacts
Solution Approach 1:
The patent implements a feedback mechanism where the insulation monitoring device continuously monitors the power circuit impedance and provides real-time information about contact status to the control system. When welded contacts are detected through impedance changes, the system can immediately respond by isolating the affected outlet, providing continuous safety monitoring in multi-outlet configurations.
Solution Approach 2:
The system performs welded detection during the cable check phase, which occurs before power delivery begins. This preliminary detection identifies potential welded contact issues before they can cause safety hazards during active charging, allowing the system to prevent unsafe operation from the outset.
Data Source
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AI summary
Disclosed is a method (600) and a system for determining a welded condition of power contacts (110, 112) in an Outgoing Coil (OGC) within an Electric Vehicle Supply Equipment (EVSE) (102). The method (600) comprises 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 comprises capturing an outlet voltage influenced by the voltage pulses superimposed on the power circuit. The method further comprises determining a welding status of the power contacts based on the captured outlet voltage. The method further comprises controlling an operational state of an associated charging outlet of the EVSE based on the determined welding status of the power contacts corresponding thereto.