EVSE Overcurrent Protection Circuit with Current Limiting
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Solution Overview
Problem
Electric vehicle charging systems face challenges with excessive current flow, leading to potential ground faults and nuisance tripping, which can disrupt charging processes and require users to locate and actuate primary overcurrent protection devices, causing unnecessary de-energization of other loads.
Innovation Solution
An electric vehicle supply circuit with an overcurrent protection feature that includes a controller and current sensor to monitor and control the flow of power, preventing excessive current and providing a user interface for setting current limits, thereby preventing overcurrent protection device tripping and allowing for automatic testing and alarm activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overcurrent protection devices are installed on branch circuits to prevent excessive current flow, then safety is improved, but other loads on the same branch circuit are unnecessarily de-energized when overcurrent occurs
Solution Approach 1:
The patent divides the overcurrent protection function into two independent parts: (1) a remote overcurrent protection device on the branch circuit for safety, and (2) a local EVSE overcurrent limitation feature that proactively limits charging current. This segmentation ensures that the remote device never trips because the local feature prevents excessive current before it reaches the branch circuit, thus maintaining safety while avoiding disruption to other loads.
Solution Approach 2:
The EVSE implements preliminary overcurrent limitation by proactively monitoring and controlling the charging current to prevent it from exceeding safe levels. This preliminary action occurs before any overcurrent condition can develop, eliminating the need for reactive tripping of branch circuit protection devices and ensuring continuous operation of other loads.
2Productivity
If EVSE limits charging current proactively to prevent overcurrent protection device tripping, then operational continuity is improved, but the complexity of the EVSE control system increases
Solution Approach 1:
The EVSE's controller is designed to perform multiple functions: it manages normal charging operations, monitors current levels, and implements overcurrent limitation using the same hardware and control logic. This multi-functionality avoids the need for separate dedicated overcurrent protection circuitry, thereby limiting the increase in system complexity while achieving proactive current management.
Solution Approach 2:
The system uses feedback from the charging current measurement to dynamically adjust the charging rate. The controller continuously monitors the current and compares it against predetermined thresholds, then adjusts the power delivery accordingly. This closed-loop feedback mechanism enables intelligent current management without requiring overly complex control systems.
3Reliability
If EVSE implements automatic overcurrent testing and alarm activation, then reliability is improved, but device complexity increases
Solution Approach 1:
The EVSE performs automatic self-testing of its overcurrent protection functionality at predetermined intervals without requiring external intervention or complex test equipment. The system uses its own operational components to verify that overcurrent limitation is working correctly, and automatically activates alarms if faults are detected. This self-service approach enhances reliability while minimizing added complexity.
Data Source
AI summary
An EVSE system includes an electric vehicle supply circuit having overcurrent protection circuit to prevent excessive current from flowing to the electric vehicle. A current limit may be set by a manufacturer of the EVSE, by a user of the EVSE, by an electric utility, by the EVSE itself in response to a control pilot signal, etc. The current limit may be set to prevent tripping an overcurrent protection device on a branch circuit for the EVSE, to accommodate one or more parameters of an electric vehicle charging facility, etc. The overcurrent protection feature may be integrated into a controller for the electric vehicle supply circuit, or it may be operate independently of the controller.