Differential Gear Drive Startup Using Auxiliary Speed Superposition
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Solution Overview
Problem
Existing drive systems for work machines requiring variably adjustable speeds are complex and expensive, and there is a need to prevent excessive inrush current during startup to avoid grid disruptions or overheating.
Innovation Solution
A drive arrangement with a differential gear, two drive units, and an auxiliary transmission stage, utilizing a self-switching shifting element to safely ramp up to nominal speed, eliminating the need for complex control units by using mechanical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a non-speed-adjustable drive unit is connected directly to the power grid, then the drive unit can start immediately, but excessive inrush current is generated causing grid disruptions or overheating
Solution Approach 1:
The auxiliary drive unit is activated before the main drive unit to pre-rotate the drive shaft to a safe operating speed. This preliminary action ensures that when the main drive unit is connected to the power grid, the motor does not experience excessive inrush current because the rotor is already moving at a speed closer to synchronous speed, reducing the current spike.
Solution Approach 2:
The auxiliary drive unit acts as an intermediary between the power grid and the main drive unit. It provides a controlled startup mechanism that gradually brings the system to operating speed, mediating the harmful inrush current effect by decoupling the direct connection between the power grid and the stationary motor rotor.
2Adaptability or versatility
If electric motors with frequency converters are used to drive work machines at variable speed, then variable speed control is achieved, but the system becomes complex and expensive
Solution Approach 1:
The drive system is segmented into two independent drive units: a main drive unit for primary power delivery and an auxiliary drive unit for speed control and startup assistance. This segmentation allows variable speed control without requiring a complex frequency converter on the main motor, as the auxiliary unit provides the necessary speed modulation.
Solution Approach 2:
The auxiliary drive unit serves multiple functions: it provides variable speed control during operation, enables safe startup by pre-rotating the drive shaft, and can assist during load changes. This multi-functionality eliminates the need for separate startup devices and frequency converters, reducing overall system complexity.
3Adaptability or versatility
If a gearbox with hydraulically or electrically driven superposition branch is used for variable transmission ratio, then variable speed is achieved, but the system becomes complex and expensive
Solution Approach 1:
The patent replaces complex mechanical variable transmission ratio gearboxes with a simpler system using two electric drive units. The variable speed control function previously requiring intricate mechanical gear systems is achieved through electronic control of the auxiliary drive unit's speed, which is superimposed on the main drive unit's constant speed output.
4Power
If medium-voltage frequency converters are used due to high power requirements, then high power variable speed control is achieved, but cost and complexity increase significantly
Solution Approach 1:
The high power drive system is segmented into a main drive unit operating at constant speed and an auxiliary drive unit providing variable speed control. This segmentation allows the auxiliary unit to use a simpler, lower-power frequency converter or speed control mechanism, while the main unit can be a straightforward high-power motor, avoiding the need for a single complex medium-voltage frequency converter.
Data Source
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AI summary
Drive arrangement of a working machine (4) to be driven at a variably adjustable speed, with a differential gear (1), with a first drive unit (2) coupled to a first element of the differential gear (1), with a working machine (4) coupled to a second element of the differential gear (1), with a second drive unit (3) coupled to a third element of the differential gear (1), the speed of which can be superimposed on a speed dependent on the speed of the first drive unit (2), wherein the first drive unit (2) or the second drive unit (2) can be driven at a variably adjustable speed.The drive arrangement has an auxiliary gear stage (12) and a switching element (13) that interacts with the auxiliary gear stage (12), wherein when the switching element (13) is closed the auxiliary gear stage (12) is load-transmitting and the speeds of the first drive unit (2) and the second drive unit (3) are coupled depending on at least one gear ratio of the auxiliary gear stage (12), and wherein when the switching element (13) is open the auxiliary gear stage (12) is load-free and the speeds of the first drive unit (2) and the second drive unit (3) are decoupled.