Differential Gear Drive Train for High-Torque Variable-Speed Startup
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Solution Overview
Problem
Existing drive systems, particularly those using three-phase machines, face inefficiencies and high costs due to the need for oversized machines to deliver torque from standstill, leading to high electrical losses and strain on the network during startup, and limited speed range capabilities in differential mode.
Innovation Solution
A drive train system incorporating a differential gear with three inputs and outputs, connected to both a drive machine and a differential drive, where the differential drive compensates for speed differences, allowing variable-speed operation while maintaining constant drive machine speed, and using a rectifier instead of an inverter for increased efficiency and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If three-phase machines are designed to deliver full torque from standstill, then starting torque is sufficient, but the machines become oversized and electrical losses increase
Solution Approach 1:
The drive system is segmented into two independent drive machines: a first drive machine connected directly to the grid for providing constant speed operation, and a second drive machine connected through a differential gear for providing variable speed operation and torque assistance during startup. This segmentation allows each drive machine to be optimized for its specific function, preventing the need for an oversized single machine.
Solution Approach 2:
The patent combines two drive machines through a differential gear mechanism to create a hybrid drive system. The first drive machine (grid-connected) and second drive machine (variable speed) work together, with the differential gear merging their outputs to drive the working machine. This merging allows torque superposition during startup while maintaining efficient operation during normal running.
2Adaptability or versatility
If a frequency converter is used to enable variable-speed operation, then speed control is improved, but costs and complexity increase significantly
Solution Approach 1:
The differential gear acts as a mechanical intermediary between the two drive machines, enabling variable-speed operation without requiring a frequency converter. By mechanically combining the outputs of the grid-connected drive machine and the variable-speed drive machine, the system achieves speed variation while avoiding complex power electronic control systems.
3Adaptability or versatility
If the differential drive is oversized to handle full power, then variable-speed range is improved, but the system becomes more expensive and less efficient
Solution Approach 1:
The second drive machine connected to the differential gear is designed to provide only partial power assistance rather than full power. During startup, it provides torque boost, and during variable-speed operation, it provides speed control assistance, but the primary driving force comes from the grid-connected first drive machine. This partial action approach allows the differential drive to be smaller and more efficient.
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
Enables efficient variable-speed operation with reduced electrical losses and lower starting currents, allowing for higher torque delivery from zero speed without straining the network, while maintaining a smaller, more cost-effective differential drive system.
Implementation Method 1
an electric drive machine connected to a power grid, operable as a motor and generator
Implementation Method 2
Replacing the inverter typically used for an electric differential drive with a rectifier is advantageous because it is usually more efficient than an inverter
Data Source
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AI summary
Disclosed is a method for operating a drive train having a drive shaft (2), an electric prime mover (4) connected to an electrical grid (12), and a differential gearing (3) having a total of three input and output elements, an output element being connected to the drive shaft (2), one input element to the prime mover (4) and a second input element to a differential drive (5). According to said method the differential drive (5) is motor-operated only, whereas the prime mover (4) is motor- or generator-operated, the differential drive (5) being coupled to the electrical grid (12) by way of a rectifier (19).