Aircraft Constant Frequency Generator Power Factor Optimization

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Solution Overview

Problem

Aircraft electrical systems face challenges in producing constant frequency AC power without incurring weight and cost penalties associated with hydromechanical transmissions or requiring constant speed operation of auxiliary power units, and existing constant frequency generators with exciter generators are large and heavy, contributing to overall weight and cost.

Innovation Solution

A constant frequency generator system comprising a prime mover, an exciter generator, a main generator, and one or more capacitors electrically coupled to the main generator rotor to alter the power factor, allowing for the production of constant frequency AC power from a variable speed prime mover, thereby optimizing the size and weight of the exciter generator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If an exciter generator is used to supply AC power to a main generator rotor in a constant frequency generator, then constant frequency AC power can be produced from a variable speed engine, but the exciter generator becomes large and heavy, contributing substantially to overall weight and cost

Engineering Contradiction:

Improveconstant frequency power production from variable speed engineVSAvoidexciter generator weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The patent changes the electrical parameters of the main generator rotor by introducing capacitors to alter the power factor. This parameter change allows the rotor to operate efficiently with reduced reactive power requirements, enabling a smaller, lighter exciter generator while maintaining constant frequency power production capability from a variable speed engine.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If hydromechanical transmission is used between engine and generator to maintain constant generator speed, then constant frequency power can be produced, but the system incurs weight and cost penalties

Engineering Contradiction:

Improveconstant frequency power productionVSAvoidhydromechanical transmission complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical transmission system with an electrical solution. Instead of using hydromechanical transmission to maintain constant generator speed, the system uses a variable speed prime mover coupled with a main generator whose rotor power factor is modified by capacitors. This substitution eliminates the need for complex mechanical transmission components while achieving constant frequency power production.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Quantity of substance

If the main generator rotor operates with low power factor, then less reactive power is required from the exciter generator, but the exciter generator size and weight cannot be reduced without affecting power production capability

Engineering Contradiction:

Improvereactive power requirementVSAvoidexciter generator weight

Core Design Contradiction:

Quantity of substanceVSWeight of moving object

Solution Approach 1:

The patent introduces capacitors as an intermediary element between the power source and the main generator rotor. These capacitors provide reactive power compensation locally, acting as a mediator that reduces the reactive power burden on the exciter generator. This allows the exciter generator to be smaller and lighter while maintaining the necessary power production capability.

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

The system effectively provides constant frequency AC power to aircraft electrical systems, reducing the weight and cost of exciter generators by improving the power factor of the main generator rotor, enabling operation with a variable speed prime mover and minimizing the size and weight of the exciter generator.

Implementation Method 1

one or more capacitors electrically coupled to the main generator rotor to increase a power factor of the main generator rotor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

an exciter generator rotatably coupled to the prime mover; a main generator rotatably coupled to the prime mover, the main generator having a main generator rotor electrically coupled to the exciter generator to receive AC power from the exciter generator

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9450527B2Controlled frequency generator with optimized power factor

Publication Date: 2016.09.20 HONEYWELL INTERNATIONAL INC

AI summary

Apparatus for generating and supplying electrical power to AC loads on an aircraft may include a prime mover, an exciter generator rotatably coupled to the prime mover and a main generator with a main generator rotor electrically coupled to the exciter generator to receive AC power from the exciter generator. One or more capacitors may be electrically coupled to the main generator rotor to increase a power factor of the main generator rotor.