Energy Store Safety Switch Timing for Reversible Overcurrent
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Solution Overview
Problem
Existing safety switches in electrical energy storage systems, such as those in electric vehicles, are oversized and costly due to their need to handle high currents, leading to unnecessary tripping and potential false fault detection when currents exceed the maximum rated level, limiting their reversibility and operational flexibility.
Innovation Solution
A method where a safety switch is activated only when the current through the electrical line falls below a predefinable threshold value, allowing for a smaller and more cost-effective design, with the option to estimate exceedance time using past events or a neural network to ensure timely activation and prevent false tripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the safety switch is dimensioned to handle high short-circuit currents, then the safety switch can reliably activate even during short circuits, but the safety switch becomes large, costly, and cannot be used for reversible trips below maximum current
Solution Approach 1:
A control unit is introduced as an intermediary between the current-carrying line and the safety switch. The control unit monitors current via a current sensor and intelligently determines when to activate the safety switch, replacing the direct mechanical connection approach. This mediator enables precise control logic that distinguishes between reversible overcurrent conditions and irreversible fault conditions.
Solution Approach 2:
The control unit performs preliminary assessment of current conditions before activating the safety switch. It evaluates whether the overcurrent is temporary and reversible or permanent and requires shutdown. This preliminary action prevents unnecessary trips and allows the safety switch to be properly sized for actual fault conditions rather than worst-case scenarios.
2Device complexity
If the safety switch is designed for maximum current below short-circuit current, then the safety switch is smaller and more cost-effective, but the safety switch trips even during temporary high current draws that are not actual faults
Solution Approach 1:
The safety switch activation threshold is made dynamic rather than fixed. The control unit adjusts the trip threshold based on real-time current conditions, vehicle operating state, and thermal models. This dynamic approach allows the system to tolerate temporary high currents during normal operation while maintaining protection against actual faults.
Solution Approach 2:
The system changes the parameter of trip threshold based on operating conditions. Different current thresholds are applied depending on whether the vehicle is accelerating, decelerating, or in normal operation. This parameter adaptation prevents false trips during high-power demands while maintaining safety during actual fault conditions.
3Reliability
If the safety switch activates at any current above maximum rating, then safety is ensured, but the electrical energy store is incorrectly considered faulty and operational flexibility is lost
Solution Approach 1:
The control unit continuously monitors current, temperature, and operating conditions to provide feedback for intelligent trip decisions. This feedback loop enables the system to distinguish between temporary overcurrent during normal operation and sustained overcurrent indicating actual faults. The feedback mechanism allows reversible trips to be avoided while maintaining safety.
Solution Approach 2:
The control unit performs preliminary assessment of current conditions before activating the safety switch. It evaluates whether the overcurrent is temporary and reversible or permanent and requires shutdown. This preliminary action prevents unnecessary trips and allows the safety switch to be properly sized for actual fault conditions rather than worst-case scenarios.
Data Source
AI summary
The invention relates to a method for operating an electrical energy store, comprising a storage cell for storing electrical energy and a control unit, wherein a safety switch is provided which is designed to interrupt an electrical line of the electrical energy store, wherein a current flowing through the electrical line is detected and an actuation of the safety switch only occurs if the current is below a predefinable threshold value.