Starter-Generator Planetary Drive for Constant Speed and High Start Torque
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Solution Overview
Problem
Current turbomachine systems face inefficiencies and reliability issues due to the use of hydromechanical differential devices for speed control, which result in low overall efficiency, unreliability, and increased wear, particularly during starting phases where high torque is required, and the need for larger generators to handle starter mode torque without impacting generator size.
Innovation Solution
A turbomachine system incorporating a starter-generator with a planetary gear reducer and control means to modify the speed of electric machines, allowing for maximum torque delivery during starting phases without increasing generator size, and maintaining constant speed in generator mode, utilizing a purely electrical drive system that eliminates dissipative losses and integrates starter functionality within the existing generator framework.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a hydromechanical differential device is used for speed control, then constant speed adjustment of the generator is achieved, but overall efficiency decreases to around 80% due to internal leaks, friction, and dissipative losses
Solution Approach 1:
The patent replaces the hydromechanical differential device with a purely electrical speed control system using an electric machine (motor or generator) coupled to the generator shaft. This electrical system eliminates hydraulic fluid leaks, friction losses in hydraulic components, and dissipative losses in pressure regulators, thereby significantly improving overall efficiency while maintaining constant speed control capability.
2Force
If the generator size is increased to handle starter mode torque, then maximum torque during starting phases is sufficient, but the generator becomes larger and more cumbersome
Solution Approach 1:
The patent makes the generator capable of operating in multiple modes: generator mode for normal power production and starter mode for high-torque starting. By controlling the electric machine to operate in motor mode during starting phases, the system achieves high starting torque without requiring the generator to be oversized, as the torque is provided by the electric machine rather than the generator itself.
3Speed
If a fixed-displacement hydraulic motor is used for speed control, then pressure regulation is achieved, but head losses and dissipative losses increase
Solution Approach 1:
The patent eliminates the fixed-displacement hydraulic motor and associated pressure regulation system by using an electric machine for speed control. This substitution removes the sources of head losses in hydraulic passages and dissipative losses in pressure regulators, achieving speed control through electrical means with significantly lower energy losses.
4Speed
If a variable displacement hydraulic motor is used for speed control, then flow conservation is achieved, but internal leaks and friction reduce overall efficiency
Solution Approach 1:
The patent replaces the variable displacement hydraulic motor with an electric machine controlled by electronic means. This eliminates internal hydraulic leaks and friction losses associated with hydraulic piston mechanisms, achieving speed control through electrical actuation with superior efficiency.
5Adaptability or versatility
If the hydraulic system operates in a wide speed range, then reversible operation in two quadrants is achieved, but wear increases and reliability decreases
Solution Approach 1:
The patent replaces the hydraulic system with an electric machine that can operate in all four quadrants (motoring and generating in both forward and reverse directions) without the wear and reliability issues of hydraulic components. The electric machine's electronic control system provides seamless operation across the entire speed range without mechanical wear.
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 solution enables efficient and reliable operation by providing double the torque required during starting phases without increasing generator size, maintaining constant output speed, and optimizing power transfer between electric machines, thus enhancing the turbomachine's efficiency and reliability.
Implementation Method 1
a planetary gear reducer comprising three elements, a central sun gear, an outer crown and a planet carrier whose satellites mesh with said sun gear and said crown
Implementation Method 2
a first electric machine configured to transfer electric power to the second electric machine or to transform electrical power into mechanical power
Implementation Method 3
the starter-generator integrating the second electric machine being arranged to transfer electric power from one to the other
Data Source
Figure 1a~1b
Figure 2
Figure 3a~3b
AI summary
The invention relates to a turbomachine (10) comprising: - an electric machine (30), - a starter-generator (17) incorporating a second electric machine (40) configured to operate as a starter and a generator, the electric machine and the generator-starter being arranged to transfer electric power between them, - a planetary gear reduction device (50) comprising a first element coupled to an accessory relay housing (12), a second element coupled to the starter-generator (17), a third element rotated by the electric machine (30), - control means configured to modify the speed of rotation of the first electric machine (30) and the starter-generator (17) so as to provide the starter-generator (17) with a maximum torque in starter mode, and to modify the speed of rotation of the first electric machine (30) such that the starter-generator (17) is driven at a constant speed in generator mode.