Hybrid Gearbox Ratio Control to Decouple Load During Train Start-Up
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Solution Overview
Problem
Current train systems face inefficiencies and increased costs due to the need for complex power sources and additional equipment to manage variable speed ratios and start-up loads, particularly when using fixed transmission ratios and single-shaft gas turbines, which lead to sub-synchronous torsional interactions and higher operational expenses.
Innovation Solution
A method utilizing a hybrid gearbox with a layshaft gear arrangement and motor-generator units to control the star carrier speed, allowing for continuous adjustment of transmission speed ratios and enabling no-load start-ups, synchronization of driven equipment speed, and efficient operation of power sources like gas turbines and electric motors, while minimizing CO2 production and building spinning reserves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed transmission ratio gearbox is used with a single-shaft gas turbine, then the system structure is simple, but the gas turbine cannot start-up without bearing load resistance
Solution Approach 1:
The patent applies a variable transmission ratio gearbox that can dynamically adjust its gear ratio during operation. During start-up, the gearbox provides a high transmission ratio to reduce load resistance on the gas turbine, enabling successful start-up. After start-up, the transmission ratio can be varied to optimize performance under different operating conditions, thus resolving the contradiction between simple structure and start-up capability.
Solution Approach 2:
The patent changes the transmission ratio parameter from fixed to variable. By using a gearbox with continuously variable transmission ratio, the system can adapt the transmission ratio according to operational requirements - using high ratio during start-up to minimize load on the gas turbine, and adjusting to appropriate ratios during normal operation, thereby enabling single-shaft gas turbines to start-up successfully while maintaining operational flexibility.
2Speed
If a variable frequency drive electric motor is used to change rotational speed, then the speed can be varied, but the system complexity increases due to large frequency converters
Solution Approach 1:
The patent replaces the electrical variable frequency drive system with a mechanical variable transmission ratio gearbox. Instead of using complex electrical converters to control motor speed, the system uses a mechanically controlled gearbox with variable transmission ratio to achieve speed variation. This substitution reduces electrical system complexity while maintaining the ability to vary rotational speed according to operational needs.
3Speed
If an electric motor with VFD is used, then speed control is achieved, but sub-synchronous torsional interactions occur and CAPEX and OPEX are not optimized
Solution Approach 1:
The patent replaces the electric motor with VFD system with a mechanical variable transmission ratio gearbox system. This substitution eliminates the sub-synchronous torsional interactions that occur with VFD-controlled electric motors, as the mechanical gearbox provides smooth, continuous speed variation without the electrical frequency conversions that cause torsional vibrations. The system achieves speed control while avoiding the harmful torsional interactions and optimizes both CAPEX and OPEX.
4Adaptability or versatility
If a variable gear ratio epicyclic gearbox is used, then design flexibility increases, but the gearbox structure becomes more complex
Solution Approach 1:
The patent employs a variable transmission ratio gearbox with epicyclic gear mechanisms that can dynamically adjust the transmission ratio. The epicyclic gearbox structure provides inherent design flexibility through its multiple gear elements (sun gear, planet gears, ring gear) that can be configured in various arrangements. By controlling the relative speeds of these elements, the system achieves continuous variable transmission ratio while utilizing the compact and efficient epicyclic gear structure, balancing design flexibility with structural complexity.
Data Source
AI summary
A method of operating a train system for driving a mechanical driven equipment is disclosed. The train system comprises a hybrid gearbox connected between a power source and a load to be driven. The hybrid gearbox includes a lay shaft gear, which transmission ratio between the power source and the load and a motor-generator unit can be adjusted, to adjust the transmission speed ratio, arranged to balance the power generated by the power source and transmitted to the load.