Starter-Generator Gear Train for Constant Speed and High Starting Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current turbomachine systems face inefficiencies and reliability issues due to hydromechanical differential devices, which have low overall efficiency, are prone to wear, and require complex electromagnetic braking systems for starting, leading to size and cluttering problems when trying to provide high starting torque without impacting the generator's size.
Innovation Solution
A turbomachine system incorporating an epicyclic reduction gear train and dual electric machines that allow for adjustable speed and torque distribution, enabling the starter-generator to operate at constant speed and provide twice the torque in starter mode without increasing the generator's size, using an epicyclic reduction gear train and dual electric machines for efficient power transfer and redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a hydromechanical differential device is used to control generator speed, then constant speed operation is achieved, but overall efficiency drops to around 80% due to internal leaks, friction, and pressure losses
Solution Approach 1:
The patent replaces the hydromechanical differential device with an epicyclic gear train combined with two electric machines. This substitution eliminates hydraulic fluid, pressure controllers, and variable displacement motors, thereby removing the sources of internal leaks, friction losses, and pressure drops that limited efficiency to 80%. The electric machines provide precise speed control without the energy losses inherent in hydraulic systems.
Solution Approach 2:
The invention changes the control parameter from hydraulic pressure and flow rate to electrical parameters (voltage, current, frequency) that can be controlled more efficiently. The control system adjusts the speed of the first electric machine and the electrical parameters of the second electric machine to maintain constant generator speed while minimizing energy losses, achieving efficiencies above 80%.
2Force
If the generator size is increased to provide high starting torque, then maximum torque is doubled, but the generator becomes larger and causes cluttering problems
Solution Approach 1:
The patent segments the torque provision function into two separate electric machines working in conjunction with the epicyclic gear train. The first electric machine handles speed control, while the second electric machine provides the additional torque multiplication needed for starting. This segmentation allows the generator itself to remain compact while still achieving high starting torque through the coordinated action of the two electric machines and gear train.
Solution Approach 2:
The epicyclic gear train acts as an intermediary mechanical element between the two electric machines and the generator. It provides torque multiplication and speed transformation, allowing the system to deliver high starting torque without requiring the generator to be physically larger. The gear train mediates the power flow, enabling compact generator design while maintaining high torque capability during starting.
3Speed
If a fixed displacement hydraulic motor is used for speed control, then constant speed is maintained, but pressure losses occur at the hydraulic device and dissipative losses occur at the pressure controller
Solution Approach 1:
The patent replaces the fixed displacement hydraulic motor and pressure controller with an electric machine controlled by an electronic control system. This substitution eliminates hydraulic pressure losses and dissipative losses in pressure controllers. The electric machine provides smooth, efficient speed control through electrical parameter adjustment without the energy waste associated with hydraulic throttling and pressure regulation.
4Adaptability or versatility
If the turbomachine operates in both motor and generator modes, then versatility is improved, but efficiency drops below 80% due to wide speed range operation
Solution Approach 1:
The patent implements true multi-functionality by using two electric machines that can independently operate in motor or generator mode. The first electric machine controls speed, while the second electric machine handles torque and power transfer. This universal design allows efficient operation in both motor and generator modes across the entire speed range, maintaining high efficiency regardless of operating quadrant because each electric machine operates within its optimal efficiency range.
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 eliminates dissipative losses, ensures reliable operation with reduced component count, and allows for high-torque starting without increasing the generator's size or adding components, maintaining constant output speed and optimizing efficiency across both motor and generator modes.
Implementation Method 1
an epicyclic reduction gear train comprising three elements, a central planetary gear, an external ring gear and a planet carrier whose planet gears mesh with the planetary gear and the ring gear
Data Source
AI summary
A turbomachine has an electric machine, and a starter-generator incorporating a second electric machine configured to operate as a starter and a generator. The electric machine and the generator-starter are arranged to transfer electric power between them. A planetary gear reduction device has a first element coupled to an accessory relay housing, a second element coupled to the starter-generator, a third element rotated by the electric machine, control means configured to modify the speed of rotation of the first electric machine and the starter-generator so as to provide the starter-generator with a maximum torque in starter mode. The planetary gear reduction device also modifies the speed of rotation of the first electric machine such that the starter-generator is driven at a constant speed in generator mode.