Hybrid Gearbox With Motor-Generator Ratio Control for Train Drives
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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 components like clutches to manage speed variations and start-up loads, particularly when using fixed transmission ratios or single-shaft gas turbines, leading to sub-optimal CAPEX and OPEX, as well as potential torsional interactions and power peak requirements.
Innovation Solution
A layshaft gear arrangement with a speed ratio motor-generator unit and a power balance motor-generator unit, allowing for continuous variable torque control and efficient power management, enabling no-load start-ups and synchronization of driven equipment speed with the driver, and optimizing power sources like gas turbines, electric motors, and diesel engines for transient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed transmission ratio gearbox is used, then the system structure is simple, but the driven equipment speed cannot be varied and requires complex power sources
Solution Approach 1:
The patent applies a variable ratio gearbox that can dynamically adjust the transmission ratio between input and output shafts. The gearbox includes a first gear set with fixed ratio and a second gear set with variable ratio, allowing the system to transition from simple fixed-ratio operation to adaptive variable-ratio operation based on operational requirements.
2Adaptability or versatility
If a variable frequency drive electric motor is used to vary speed, then the driven equipment speed can be changed, but the system becomes complex with large frequency converters
Solution Approach 1:
The patent replaces the electrical VFD system with a mechanically-based variable ratio gearbox. The variable ratio mechanism uses mechanical components (gears, sun wheels, planet wheels, carriers) to achieve speed variation without requiring large frequency converters, thereby reducing electrical system complexity while maintaining speed adaptability.
3Adaptability or versatility
If a variable gear ratio epicyclic gearbox is used, then the driven equipment speed can be varied continuously, but the device complexity increases
Solution Approach 1:
The patent segments the variable ratio gearbox into two independent gear sets: a first gear set with fixed transmission ratio and a second gear set with variable transmission ratio. This segmentation allows each gear set to be optimized independently and simplifies the overall control mechanism, as the variable ratio can be achieved through a simpler second gear set rather than a complex full epicyclic arrangement.
4Device complexity
If a single-shaft gas turbine is used with fixed speed ratio transmission, then the system is simple, but the gas turbine cannot start up due to load resistance
Solution Approach 1:
The patent uses a variable ratio gearbox that can dynamically adjust the transmission ratio during start-up. During gas turbine start-up, the gearbox provides a high ratio to reduce load resistance on the turbine. Once the turbine is running, the ratio can be changed to match operational requirements, enabling both simple single-shaft turbine design and successful start-up operation.
5Adaptability or versatility
If an electric motor with VFD is used, then the driven equipment speed can be varied, but sub-synchronous torsional interactions occur
Solution Approach 1:
The patent replaces the VFD electric motor system with a mechanically-based variable ratio gearbox driven by a constant speed prime mover. This mechanical approach to speed variation avoids the electrical frequency conversions that cause sub-synchronous torsional interactions, thereby eliminating the harmful torsional vibrations while maintaining the ability to vary driven equipment speed.
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 compact, flexible, and efficient power transmission, reducing costs and energy losses, allowing for maximum efficiency of power sources, minimizing CO2 production, and enabling energy storage and spinning reserve capabilities.
Implementation Method 1
a motor-generator unit (MGU), which acts as a continuous controlled variable torque system (CCVT)... By changing the star carrier speed, the gear input/output speed ratio can be continuously changed
Implementation Method 2
The gearbox can be of different types, and in particular, it can fixed or variable gear ratio type... an input shaft, which the power source is connected to, an output shaft, connected to the load L, and a gearbox to change the transmission ratio
Data Source
AI summary
A hybrid gearbox for a mechanical driven equipment in a train system is disclosed. The hybrid gearbox is connected between a power source and a load, to be driven. The hybrid gearbox includes a layshaft gear, capable of adjusting the transmission ratio between the power source and the load and a motor-generator unit, configured to adjust the transmission speed ratio arranged.