EV Power Supply Relay Stress Distribution Control
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Solution Overview
Problem
The existing power supply systems in electric vehicles face issues with relay lifespan due to arc occurrence when relays are closed at different timings, leading to premature wear and reduced reliability.
Innovation Solution
A power supply system with a control device that pre-charges a capacitor and closes the positive and negative electrode-side relays at different timings, adjusting the sequence based on stress indexes to evenly distribute stress and prevent uneven wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the positive electrode-side relay and negative electrode-side relay are closed at different timings to suppress inrush current, then the inrush current is reduced, but arcs occur in the relays which shortens their lifespan
Solution Approach 1:
The control device pre-charges the capacitor before closing the relays to reduce voltage difference and inrush current. This preliminary action prepares the system in advance to mitigate the harmful effects of relay closing while maintaining the benefit of reduced inrush current.
Solution Approach 2:
The control device dynamically adjusts the closing timing sequence of the relays based on real-time voltage conditions and stress indexes. By making the closing timing adaptive rather than fixed, the system optimizes both inrush current suppression and relay lifespan extension under varying operating conditions.
2Use of energy by moving object
If the relays are closed at different timings, then inrush current is suppressed, but stress accumulates unevenly in one relay which reduces reliability
Solution Approach 1:
The control device monitors stress indexes of both relays and uses this feedback information to adjust the closing sequence. When one relay accumulates excessive stress, the system switches to an alternating closing pattern to distribute stress more evenly, thereby maintaining reliability while continuing to suppress inrush current.
Solution Approach 2:
The control device changes the operating parameters (closing timing sequence) based on stress accumulation levels. By dynamically switching between different closing sequences (fixed sequence vs. alternating sequence), the system optimizes both inrush current suppression and stress distribution uniformity.
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
This configuration effectively extends the lifespan of the relays by evenly distributing stress during closing and opening operations, enhancing the system's reliability and longevity.
Implementation Method 1
a power control unit that includes a capacitor and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay
Implementation Method 2
a positive electrode-side relay, a negative electrode-side relay and a power control unit that includes a capacitor
Data Source
AI summary
A power supply system includes a power storage device, a positive electrode-side relay, a negative electrode-side relay, a power control unit that includes a capacitor configured to be pre-charged in response to a system start request and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay, and a control device programmed to close the positive electrode-side relay and the negative electrode-side relay at different timings always or under a predetermined condition in response to the system start request and programmed to change a sequence of closing the positive electrode-side relay and the negative electrode-side relay in accordance with a predetermined restriction. This configuration effectively extends the lives of the positive electrode-side relay and the negative electrode-side relay.