Differential Gear Power Train for Variable-Speed Starting Under Load
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Solution Overview
Problem
Existing drive train systems face challenges in achieving efficient, variable-speed operation and starting under load, particularly when synchronizing electrical machines with the network, as they often require complex and inefficient solutions like frequency converters or differential drives that limit torque delivery and speed range.
Innovation Solution
A drive train system utilizing a differential gear with a planetary gear stage and a differential drive connected to both the drive machine and the network, allowing for three operational phases: initial acceleration of the differential drive, synchronization with the network, and subsequent operation in differential mode to achieve a wide speed range and maximum torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a frequency converter is used to achieve variable-speed operation from zero speed, then the speed range is improved, but the cost and efficiency are worsened due to significant losses and high expense
Solution Approach 1:
The speed control range is segmented into two distinct operational modes: a first speed range (0-50% of synchronous speed) achieved through differential drive in series connection, and a second speed range (above 50%) achieved through direct differential drive connection. This segmentation allows each mode to operate optimally without the continuous energy losses of a frequency converter across the entire range.
Solution Approach 2:
The patent replaces the electronic frequency converter system with a mechanical differential drive system. The differential drive uses mechanical gear stages with different gear ratios to achieve variable speed operation, substituting electronic power conversion with mechanical transmission to eliminate converter losses.
2Loss of energy
If a differential drive is used to achieve variable-speed operation, then the cost and efficiency are improved, but the speed range is worsened due to limited torque delivery at low speeds
Solution Approach 1:
The system dynamically switches between two differential drive configurations: a first differential drive with a first gear ratio for low-speed operation (0-50% synchronous speed), and a second differential drive with a second gear ratio for high-speed operation (above 50% synchronous speed). This dynamic reconfiguration allows the system to maintain optimal torque delivery across the entire speed range.
Solution Approach 2:
The differential drive system is designed with multi-functionality to serve dual purposes: it can operate in series connection with the synchronous machine for sub-synchronous speeds, and in direct connection for super-synchronous speeds. This universal design eliminates the need for separate drive systems for different speed ranges.
3Quantity of substance
If the differential drive size is reduced to 20% of total system output, then the cost is improved, but the torque delivery is worsened due to insufficient torque for acceleration
Solution Approach 1:
The patent introduces a mechanical intermediary system consisting of two gear stages with different gear ratios. The first gear stage amplifies torque for low-speed acceleration, while the second gear stage provides appropriate gear ratio for high-speed operation. This intermediary mechanical system allows a small differential drive (20% of total output) to deliver sufficient torque across the entire operating 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 enables efficient variable-speed operation and starting under load, allowing for a large working speed range while minimizing system loads and eliminating the need for complex power electronics, thus improving efficiency and reducing costs.
Implementation Method 1
a differential gear with a planetary gear stage
Data Source
Figure 1
Figure 2~2a
Figure 3
AI summary
The invention relates to a power train comprising a drive shaft (2) of a working machine (1, 38), a drive machine (4, 42) and a differential gear (3, 7 to 9, 40) with three drives or power take-offs, wherein one power take-off can be connected to the drive shaft (2), a first drive can be connected to the drive machine (4, 42) and a second drive can be connected to the differential gear (5). One drive can be connected simultaneously to the other drive or to the power take-off.