EVSE Cable Short Circuit Detection and Contactor Protection
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Solution Overview
Problem
Electric Vehicle Supply Equipment (EVSE) relay or contactor contacts are prone to welding due to short circuits, which renders the EVSE inoperable until maintenance is performed, and existing solutions do not effectively prevent such welding during charging cable misuse.
Innovation Solution
Incorporating an impedance measuring circuit and control electronics in the EVSE to detect short circuits in the charging cable before main power contactors are closed, preventing power delivery and alerting users to potential faults, thereby protecting the contacts from welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impedance measurement is performed before contactor closure, then contact welding is prevented, but device complexity increases due to additional measurement circuitry
Solution Approach 1:
The patent performs impedance measurements on the charging cable before the contactor closes to prevent short circuits. By conducting the measurement in advance (before power is applied), the system identifies faulty cables and prevents contact welding, thereby improving reliability without requiring continuous monitoring during operation.
Solution Approach 2:
The patent introduces an impedance measurement circuit as an intermediary component between the power source and the contactor. This measurement circuit acts as a mediator that assesses cable integrity before allowing power flow, preventing harmful short circuits from reaching the contactor and causing welding.
2Reliability
If continuous monitoring is implemented, then fault detection is improved, but energy consumption increases
Solution Approach 1:
The patent performs impedance measurements periodically or at specific intervals rather than continuously. The measurement is conducted before contactor closure and can be repeated at defined intervals, providing adequate fault detection while minimizing energy consumption by keeping the measurement circuit inactive during normal operation.
3Adaptability or versatility
If cable length is increased to accommodate different vehicles, then adaptability is improved, but susceptibility to damage increases
Solution Approach 1:
The patent applies preliminary anti-action by measuring cable impedance before power is applied. This pre-check identifies cables that have been damaged (such as from bending, dropping, or running over), preventing the use of compromised cables. The measurement creates a preventive barrier against the harmful effects of cable damage before they can affect the contactor or EVSE.
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
Prevents contact welding by detecting short circuits in the charging cable before power is applied, ensuring the EVSE remains operational and reducing the need for immediate maintenance by alerting users and recording maintenance history.
Implementation Method 1
An impedance measuring circuit and control electronics are included in the EVSE to measure the resistance between the cable conductors before the cable is connected to an EV
Data Source
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AI summary
A method detects a shorted charging cable of an electric vehicle charging station. A charging cable of the electric vehicle charging station is determined to not be connected to an electric vehicle. An impedance test may then be performed between conductors of the charging cable while not connected to an electric vehicle. A contactor between a source of electrical power and the conductors is prevented from closing, in response to detecting a short between the conductors, and a warning signal is output. The impedance test is disabled in response to receiving a signal indicating that the charging cable has become connected to an electric vehicle, so as to not interfere with normal charging. In this manner, by detecting a short circuit in the charging cable before the contactors are closed, the contactor's contacts are prevented from becoming welded closed by a short circuit in the charging cable.