Aircraft Permanent Magnet Generator Fault Decoupling

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Solution Overview

Problem

Permanent magnet generators in aircraft continue to create a moving magnetic field even during short circuits, leading to potential overheating and the need for heavy brakes or clutches to manage rotation.

Innovation Solution

An electrified aircraft system that includes a permanent magnet machine, an inverter, and a controller. The controller directs the inverter to induce a preselected torque transient in the shaft, exciting it at a predetermined failure frequency to cause shaft failure, thereby mechanically decoupling the rotor from the engine and preventing overheating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If permanent magnet generators are used for onboard electrical energy generation, then efficiency and power needs are improved, but the system cannot be switched off and continues to create moving magnetic field during short circuits leading to overheating

Engineering Contradiction:

Improveelectrical energy generation efficiencyVSAvoidoverheating during short circuit

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the rotor from the permanent magnet generator and mechanically decouples it from the engine using a clutch mechanism. This separation removes the source of the harmful moving magnetic field during short circuits, allowing the stator to be protected from overheating while the rotor can be independently controlled or removed from the system.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a clutch as an intermediary mechanism between the engine and the permanent magnet generator rotor. This clutch acts as a controllable coupling that can engage or disengage the rotor from the engine, providing a means to stop the rotor's rotation and eliminate the moving magnetic field during fault conditions without affecting the overall generator structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If heavy brakes or clutches are added to manage rotation during short circuit, then overheating is prevented, but device complexity and weight increase

Engineering Contradiction:

Improveoverheating preventionVSAvoidbrake or clutch mechanism

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces the traditional mechanical brake system with an electromechanical clutch controlled by the power converter. Instead of using friction-based brakes to stop the rotor, the system uses electronic control to disengage the clutch, which mechanically decouples the rotor from the engine. This substitution reduces mechanical complexity while maintaining the ability to prevent overheating.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If heavy brakes or clutches are added to manage rotation during short circuit, then overheating is prevented, but weight increases

Engineering Contradiction:

Improveoverheating preventionVSAvoidbrake or clutch mechanism

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent makes the power converter serve multiple functions: it acts as both the standard power electronic converter for controlling the permanent magnet generator during normal operation and as the control mechanism for the clutch that prevents overheating during short circuits. This multi-functionality eliminates the need for separate brake systems, reducing overall system weight while maintaining safety capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The system effectively prevents the generation of undesired power profiles and avoids overheating by mechanically decoupling the rotor from the engine upon detection of a fault, without the need for heavy brakes or clutches.

Implementation Method 1

The controller may be configured to direct the inverter to induce a preselected torque transient in the shaft to excite the shaft at the predetermined failure frequency

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The permanent magnet machine may include a stator and a rotor configured to rotate relative to the stator to move a plurality of permanent magnets past a plurality of coils

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS12328086B2Aircraft with engine-driven permanent magnet generator

Publication Date: 2025.06.10 ROLLS ROYCE CORP

AI summary

An aircraft includes an internal combustion engine and an electrical power system. The electrical power system includes a permanent magnet machine and an inverter coupled to the permanent magnet machine. The permanent magnet machine includes a stator and a rotor configured to rotate relative to the stator.