RAT Generator Load Shedding Circuit for Stall Prevention

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Solution Overview

Problem

RAM air turbines (RATs) face challenges during startup due to significant torque loads from in-rush currents, which can cause the generator to stall if the torque exceeds the airflow torque, necessitating a controlled load shedding and staggered power application to ensure proper deployment and operation.

Innovation Solution

The Emergency Integrated Control Center (EICC) monitors primary power and anticipates losses, disabling power to essential and emergency loads until the RAT generator reaches a stable threshold, then staggers the power distribution to prevent detrimental start-up, using relay circuits and time delays to manage the loading and ensure the generator can handle in-rush currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If all essential and emergency loads are connected to the RAT generator during startup, then the generator can immediately supply full power, but the significant torque loads from in-rush currents can cause the generator to stall

Engineering Contradiction:

Improvepower supply capabilityVSAvoidgenerator startup reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The system performs preliminary actions by disconnecting all essential and emergency loads from the RAT generator before startup, then gradually reconnecting them in a controlled sequence after the generator is running. This preliminary disconnection prevents in-rush currents during startup, and the subsequent staged reconnection ensures reliable power transition without stalling the generator.

Inventive Principle:

Principle #10Preliminary action

2Use of energy by moving object

If the RAT generator is deployed into the airstream, then emergency power is generated, but the mechanical energy from airflow must overcome the electrical torque loads to prevent stalling

Engineering Contradiction:

Improvemechanical energy conversionVSAvoidtorque load from in-rush currents

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The harmful torque loads from in-rush currents are extracted or removed from the system during startup by disconnecting the essential and emergency loads. This allows the RAT generator to convert mechanical energy from airflow without being burdened by excessive electrical torque demands that would cause stalling.

Inventive Principle:

Principle #2Taking out (Extraction)

3Productivity

If power is immediately applied to essential and emergency loads upon RAT deployment, then full emergency power is available, but the generator may stall due to excessive loading

Engineering Contradiction:

Improveemergency power availabilityVSAvoidgenerator operation stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The power application process is segmented into distinct stages: first connecting only the essential load to the RAT generator, then after a time delay ensuring stable operation, connecting the emergency loads. This segmentation prevents excessive simultaneous loading while ensuring eventual full emergency power availability.

Inventive Principle:

Principle #1Segmentation

4Reliability

If the system uses controlled load shedding and staggered power application, then generator stalling is prevented, but the power distribution to loads is delayed and managed complexly

Engineering Contradiction:

Improvegenerator startup successVSAvoidpower management system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The Emergency Integrated Control Center (EICC) acts as an intermediary that automatically manages the complex load shedding and staggered power application sequences. This centralized control mediator handles the timing, connection, and disconnection of loads, preventing generator stalling while reducing the operational complexity burden on other system components.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 prevents generator stalling by controlling the load shedding and power application, ensuring the RAT generator can start up correctly and handle the electrical demands of essential and emergency loads, thereby ensuring reliable emergency power generation.

Implementation Method 1

A RAT includes a turbine that can be selectively placed into the airstream of a moving aircraft to utilize mechanical energy necessary to drive the generator. Electric energy developed by the RAT generator is distributed to one or more electric loads.

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9083201B2Load shedding circuit for RAM air turbines

Publication Date: 2015.07.14 HAMILTON SUNDSTRAND CORP

AI summary

A power generation/distribution system includes a RAM air turbine (RAT) generator and an emergency integrated control center (EICC) that selectively applies either primary power provided by a primary power source or emergency power developed by the RAT generator to an alternating current essential bus (AC ESS bus) for distribution to one or more essential loads. The EICC monitors the primary power and in response to a loss of primary power selectively disables the supply of power from the AC ESS bus to the essential loads and manages subsequent loading of the RAT generator by the essential loads.