Planetary Differential Drive Train for Starting Pumps 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 large and inefficient frequency converters or complex differential drives that limit torque delivery and speed range.
Innovation Solution
A drive train system utilizing a simple planetary gear stage with a differential drive connected to both the drive machine and the work machine, allowing for three operational phases: initial acceleration of the differential drive, connection of the prime mover to the network, and subsequent operation in differential mode for maximum torque delivery, enabling a wide working speed range without complex power electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a frequency converter is used to enable variable-speed operation from zero speed, then variable-speed operation is achieved, but the system becomes expensive and experiences significant efficiency losses
Solution Approach 1:
The patent segments the speed control function into two parts: the frequency converter handles only the differential drive (small portion), while the prime mover operates at constant speed directly connected to the grid. This segmentation allows variable-speed operation without requiring a large frequency converter, thereby reducing energy losses and costs.
Solution Approach 2:
The differential gear stage acts as an intermediary mechanical element that combines the constant-speed output from the prime mover with the variable-speed output from the differential drive to produce the final variable-speed output to the driven machine. This mechanical intermediary enables variable-speed operation without relying solely on electronic conversion.
2Loss of energy
If a differential drive is used as a cost-effective alternative to frequency converters, then efficiency is improved, but the speed range is limited and low speeds cannot be achieved
Solution Approach 1:
The patent merges two drive sources: the prime mover (providing constant speed) and the differential drive (providing variable speed). By combining these two drives through the differential gear stage, the system achieves a wide speed range including very low speeds, while maintaining high efficiency since only the differential drive operates in variable-speed mode.
3Speed
If the gear ratio of the differential gear is set to 1 to enable the differential drive to accelerate the prime mover, then the differential drive can bring the prime mover to synchronous speed, but the differential drive and frequency converter become significantly smaller and can only deliver small torque
Solution Approach 1:
The patent changes the gear ratio parameter of the differential gear from 1 to a value greater than 1. This parameter change allows the differential drive to deliver higher torque to the driven machine while the prime mover accelerates to synchronous speed, resolving the contradiction between acceleration capability and torque delivery.
4Speed
If a braking device is used to accelerate the drive motor into a high-torque speed range, then the driven machine can be started from zero speed, but the braking device becomes complex and the speed range is limited to 50%-100% of working speed
Solution Approach 1:
The patent replaces the complex braking device with a simpler differential gear mechanism. The differential gear naturally provides the necessary torque multiplication and speed control without requiring active braking, thereby reducing device complexity and expanding the achievable speed 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 allows for efficient variable-speed operation and starting under load, achieving a large working speed range with reduced system complexity and energy losses, while enabling direct connection to the network without significant external countertorque, thus improving the overall efficiency and cost-effectiveness of the drive train system.
Implementation Method 1
The core of a differential system is a differential gear, which in a simple design can be a simple planetary gear stage with three inputs and outputs
Data Source
Figure 1
Figure 2~2a
Figure 3
AI summary
To start a drive train with a drive shaft (2) of a working machine (1), with a drive machine (4, 42) and with a differential gear (3, 7 to 9, 40) with three inputs or outputs, wherein one output can be connected to the drive shaft (2), a first input to the drive machine (4, 42) and a second input to a differential drive (5), the drive machine (4, 42) is started from a speed of zero or near zero, while the differential drive (5) is simultaneously connected to the first and the second drive.