Investigation of dynamic loads of a large conveyor system
Within the scope of the research project GrobaDyn, funded by the AiF and carried out by the IBH (Institute for Mining and Metallurgical Machinery Science, one of the two predecessor institutes of the IMR, again predecessor institute of the AMT), the method of co-simulation for the holistic illustration of a large strip mining plant in a simulation model was successfully applied for the first time. The aim of this project was to develop an electromechanical simulation model which reproduces all components of a large belt plant from the drive motor to the conveyor belt in a simulation model and thus makes the interactions between the individual assemblies computably comprehensible.
Large belt conveyors, which transport overburden and coal in opencast mining, are currently operated with speed-constant asynchronous slip-ring motors (n=1000 min-1). During acceleration from standstill, electrical resistors are switched in various stages, whereby changes from one resistor package to the next cause torque jumps in the drive train. These propagate wave-like through the conveyor belt from the head to the rear of the large conveyor system and can lead to slip states there. In order to avoid these undesirable effects, open pit operators plan to use variable-speed drives in the future with which the operating speed of the systems can be variably adapted to the respective conveyor mass flow. This allows constant loading profiles to be achieved on the conveyor belt even with small mass flow rates through slower operation, while at the same time saving energy.
The team used the co-simulation method to completely map a drive station including the electric motor, drive train and conveyor belt in order to carry out electrical and mechanical simulations in parallel. The electrical simulation model was mapped in the Matlab/Simulink® software environment, the mechanical drive train in the ITI-Sim® simulation software. With the help of measurement data from operational measurements at a selected reference plant, the IMR was able to verify the electrical and mechanical simulation model and calculate the influences of electrical faults such as three-phase and two-phase faults on the mechanical components of a large strip plant with the aid of co-simulation. Based on the results of the research project, it becomes clear that it makes sense to map the complete electromechanical system when electrical faults occur. The influences of these errors have in part considerable effects on the mechanical drive train in the form of strong torque oscillations.
Through numerical simulation, we were able to demonstrate the effectiveness of various measures and components, such as additional couplings or vibration dampers, to optimize the resonance behavior. A tabular overview of the critical speed ranges for all possible drive train combinations of the large conveyor systems of the project partner RWE Power AG offers the possibility to optimize the planning of the conveyor systems with regard to the usable speed ranges and the available drive train components in the future. The goals of the AIF-funded research project "GrobaDyn - Verified electromechanical simulation of the dynamic behaviour of drives in large conveyor systems" have therefore also been successfully achieved by the project team.