Drive Train Starting with Auxiliary Drive Torque Support
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Solution Overview
Problem
Existing drive train systems that start with a direct-on-line-start for electric machines operating at constant rotational speed impose high loads on the supply network, leading to over-dimensioning and inefficiencies, which increase investment costs and reduce operational efficiency.
Innovation Solution
A method that involves starting the main drive with direct-on-line-start and simultaneously or sequentially starting the auxiliary drive with variable rotational speed, using a converter to influence the speed modulation gearbox, allowing the main drive to operate at reduced torque and rotational speed, thereby reducing the load on the supply network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the main drive is started by direct-on-line-start with direct coupling to the supply network, then the starting process is simple and fast, but the supply network is subjected to high load and voltage dips
Solution Approach 1:
The auxiliary drive is started before or simultaneously with the main drive to preliminarily accelerate the working machine. This preliminary action reduces the torque requirement during main drive starting, thereby reducing the load on the supply network while maintaining fast starting performance
Solution Approach 2:
The starting process is segmented into two phases: first the auxiliary drive accelerates the working machine to a preliminary rotational speed, then the main drive is engaged. This segmentation divides the total acceleration task, reducing the peak load on the supply network during main drive starting
2Reliability
If the supply network or main drive is over-dimensioned to handle direct-on-line-start loads, then the supply network can handle the starting load, but investment costs increase and efficiency in rated operation decreases
Solution Approach 1:
The auxiliary drive provides dynamic support during the starting phase only, allowing the main drive and supply network to be sized for rated operation rather than peak starting loads. This dynamic assistance enables cost-effective dimensioning while maintaining reliability during starting
Solution Approach 2:
The auxiliary drive performs partial acceleration work during starting, exceeding what would be needed in steady-state operation. This partial action during starting reduces the peak torque requirement, allowing the main drive to be sized for rated operation rather than starting conditions
3Power
If the auxiliary drive is operated motorically in reverse mode parallel to the main drive, then the working machine reaches a lower rotational speed with reduced torque, but the control complexity increases
Solution Approach 1:
The speed modulation gearbox with fixed mechanical transmission ratio acts as an intermediary between the two drives and the working machine. This intermediary enables the auxiliary drive to operate in reverse mode while maintaining simple control, as the gearbox handles the speed and torque modulation mechanically
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 approach enables safe and efficient starting of the drive train at a lower rotational speed than rated, reducing the required dimensioning of the main drive and supply network, thus minimizing investment costs and improving efficiency.
Implementation Method 1
a main drive (11) designed as an electric machine that can be operated with a constant rotational speed, an auxiliary drive (12) designed as an electric machine that can be operated with a variable rotational speed
Data Source
AI summary
A method for operating a drive train, having a main and, an auxiliary drive and a speed modulation gearbox with a fixed mechanical transmission ratio between the two drives, for starting and towing a drive train to a defined set rotational speed. The main drive is started via a direct-on-line-start with direct coupling to a supply network. The auxiliary drive is started simultaneously with at a time before or at a time after the main drive. For towing the drive train to the defined set rotational speed, which corresponds to a defined percentage of a rated rotational speed of the drive train, the main drive is operated motorically in forward mode at least at times and accelerated to its rated rotational speed, wherein parallel to this the auxiliary drive is operated motorically in reverse mode at least at times.