Fused Shaft Decoupling for Faulted Aircraft PM Generators

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Solution Overview

Problem

Permanent magnet generators in aircrafts face challenges in managing rotation during short circuits or faults, leading to potential overheating and system instability, as existing solutions like heavy brakes or clutches are not refined or lightweight enough.

Innovation Solution

The implementation of a shaft with a non-conductive material body and an embedded fuse, where the electric control unit introduces an electric current to heat the fuse, causing the shaft to fail and mechanically decouple the rotor from the engine, thereby preventing undesired electrical energy and heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If heavy brakes or clutches are used to manage rotation during short circuit, then rotation control is achieved, but system weight increases

Engineering Contradiction:

Improverotation control during faultVSAvoidsystem weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent extracts the weight burden from the system by eliminating the need for heavy brakes or clutches. Instead, it uses the existing shaft structure with an embedded fuse that can be selectively activated to disconnect the rotor, achieving rotation control without adding heavy mechanical components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical braking or clutching system with an electro-thermal activation system. By passing current through the fuse to heat and melt the shaft body, the system achieves mechanical disconnection through thermal effects rather than mechanical forces, significantly reducing system weight.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If the permanent magnet generator continues to rotate during short circuit, then the magnetic field continues to generate electrical energy, but overheating and system damage occur

Engineering Contradiction:

Improveelectrical energy generationVSAvoidoverheating and damage

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary anti-action by providing a pre-configured fuse in the shaft that can be activated before severe overheating or damage occurs. When a fault is detected, the fuse is heated to melt the shaft body, proactively stopping rotation and preventing the harmful effects of continued energy generation during short circuit.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent converts the harmful effect of electrical current (which causes overheating) into a beneficial control mechanism. By deliberately passing current through the fuse to melt the shaft, the system uses electrical energy to achieve safe disconnection, turning a potential harm into a useful protective action.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution effectively manages rotation and prevents overheating during faults by ensuring the rotor is decoupled from the engine, thus safeguarding the system from damage and maintaining operational safety.

Implementation Method 1

The fuse may be configured to generate heat when an electric current is passed through the fuse

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The electric control unit may introduce the electric current through the fuse to cause the fuse to heat the shaft body above a transition temperature of the electrically non-conductive material of the shaft body

Methodology Applied

Scientific EffectPhase transition: Phase Change

Data Source

PatentUS12244184B2Systems and methods for intentionally breaking shafts of compromised electric machines with electro-thermal activation

Publication Date: 2025.03.04 ROLLS ROYCE CORP

AI summary

An aircraft includes an engine and an electric power system. The electric power system includes a permanent magnet machine. The permanent magnet machine includes a stator and a rotor configured to rotate relative to the stator.