Electric Work Vehicle Battery Ground Fault Detection by Contactor Sequencing
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Solution Overview
Problem
Current methods for detecting ground faults in electric work vehicles require multiple isolation monitors, which are expensive and inefficient, and often lead to interference, necessitating a more cost-effective and efficient way to identify and isolate faulty battery packs within an aggregated battery system.
Innovation Solution
A method and apparatus that utilize a single isolation monitor and a circuit with contactors to sequence the connection of each battery pack, allowing the isolation monitor to determine which pack is faulty and disconnect it, thereby isolating the faulty pack without the need for multiple monitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple isolation monitors are installed in each battery pack to identify ground faults, then ground fault detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The system segments the battery pack testing process into sequential phases using contactors to isolate and test individual battery packs or groups one at a time, rather than requiring simultaneous monitoring of all packs. This temporal segmentation allows a single isolation monitor to achieve the same diagnostic capability that would otherwise require multiple monitors operating in parallel.
Solution Approach 2:
The system performs preliminary actions by opening contactors to disconnect battery packs from the main circuit before testing, and sequences their reconnection one at a time. This preliminary isolation prepares the system for accurate ground fault detection by eliminating interference from other battery packs, allowing a single monitor to effectively test each pack individually.
2Measurement precision
If multiple isolation monitors are installed in each battery pack to identify ground faults, then ground fault detection accuracy is improved, but cost increases
Solution Approach 1:
A single isolation monitor is designed to perform multiple functions by sequentially testing different battery packs through controlled circuit reconfiguration. The monitor serves as a universal testing device that can identify ground faults in any battery pack within the aggregated battery system, replacing the need for dedicated monitors in each individual pack.
Solution Approach 2:
The system implements periodic action by cycling through battery packs in a sequences manner, with the single isolation monitor periodically testing each pack in turn. This periodic testing approach maintains detection accuracy comparable to continuous simultaneous monitoring while significantly reducing the number of monitors required.
3Speed
If multiple isolation monitors operate simultaneously to detect ground faults, then detection speed is improved, but interference occurs reducing reliability
Solution Approach 1:
Contactors serve as intermediary devices that control the connection between battery packs and the isolation monitor. By acting as intermediaries, they enable the single monitor to access each battery pack sequentially without electrical interference, maintaining detection reliability while achieving rapid fault identification through automated sequencing.
Data Source
AI summary
A method of performing a ground fault test on a plurality of battery packs of an aggregated battery of an electric work vehicle. A circuit is configured to connect the aggregated battery to an isolation monitor. A plurality of contactors are configured to facilitate connection to the circuit and disconnection from the circuit of each of the plurality of battery packs. If the isolation monitor detects existence of a ground fault, the user of the electric work vehicle is notified of the existence of the ground fault. The plurality of contactors are opened. The closure of the plurality of contactors is sequenced to include each of the plurality of battery packs in the circuit with the isolation monitor in turn. The isolation monitor is used to determine whether the battery pack that is included in the circuit is a faulty battery pack. The faulty battery pack is disconnected.