Voltage Foldback Circuit Auto-Restart After Overload

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Solution Overview

Problem

Conventional voltage foldback circuits fail to automatically restart after detecting an overload condition without requiring complete disconnection of the load, necessitating load removal for normal operation resumption.

Innovation Solution

Incorporating a switch and timer mechanism into the foldback circuit to monitor and reset the circuit automatically upon the cessation of an overload condition, allowing normal operation to resume without load disconnection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional voltage foldback circuit is used to protect against overload conditions, then circuit protection is provided, but the circuit cannot automatically restart after overload without complete load disconnection

Engineering Contradiction:
Improvecircuit protectionVSAvoidautomatic restart capability
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent implements a feedback mechanism where the foldback circuit continuously monitors the load current and automatically restarts when the overload condition is resolved. The circuit uses a latch mechanism that detects when current returns to normal levels and triggers automatic reclosure, eliminating the need for manual load disconnection while maintaining protection reliability.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The foldback circuit is designed to self-reset automatically when overload conditions cease. The circuit monitors its own state and performs the restart function without external intervention, making the system self-service capable. This includes automatic detection of normal current levels and initiation of the restart sequence.

Inventive Principle:
Principle #25Self-service

2Reliability

If load disconnection is required to resume normal operation after overload, then protection is maintained, but operational continuity is interrupted

Engineering Contradiction:
Improveprotection maintenanceVSAvoidoperational continuity
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent employs dynamic control of the circuit breaker latch mechanism. Instead of requiring static load disconnection, the system dynamically responds to changing current conditions, automatically transitioning from protected state back to normal operation when safe conditions are detected, thus maintaining both protection and continuity.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The foldback circuit maintains continuous protection monitoring while enabling automatic restart, ensuring the useful action of circuit protection continues uninterrupted. The system seamlessly transitions between protected and normal states without requiring load disconnection, maintaining operational continuity while preserving protection functionality.

Inventive Principle:
Principle #20Continuity of useful action

3Device complexity

If a simple foldback circuit is used, then device complexity is minimized, but automatic restart functionality is lost

Engineering Contradiction:
Improvecircuit structureVSAvoidautomatic restart function
Core Design Contradiction:
Device complexityVSExtent of automation

Solution Approach 1:

The patent merges the automatic restart functionality with the existing foldback protection circuit by integrating a latch mechanism and control logic into the same device. This combination adds automation capability while minimizing the increase in overall device complexity, as the restart function shares components and control pathways with the protection function.

Inventive Principle:
Principle #5Merging (Combining)

Data Source

PatentEP3418850B1Automatically restarting a voltage foldback circuit
Publication Date: 2025.10.29 HAMILTON SUNDSTRAND CORP
  • EP3418850B1 patent drawingFigure 1
  • EP3418850B1 patent drawingFigure 2
  • EP3418850B1 patent drawingFigure 3

AI summary

Embodiments include techniques for automatically restarting a voltage foldback circuit, the techniques include operating a circuit, and detecting a condition of the circuit. The techniques also include performing a foldback operation based at least in part on the condition of the circuit, subsequently detecting the condition of the circuit. The techniques include initiating a timer of the circuit based at least in part on the subsequent detection of the circuit, and returning the circuit to normal operation based on the timer.