Dynamic analysis of the frequency-controlled starting of a belt conveyor

Abstract

The purpose of the study was to assess the influence of the shape and duration of frequency-controlled starting on the dynamic and energy indicators of the belt conveyor. To achieve this goal, a complex mathematical model of the electromechanical conveyor system was used, which integrates differential equations of longitudinal motion of the consolidated concentrated masses of the mechanical part and equations of electrodynamic processes of an asynchronous electric drive in a fixed coordinate system (alpha-beta axes). In the framework of a numerical computer experiment in the MATLAB/Simulink environment, two forms of the trajectory of increasing the frequency of the motor stator supply voltage were studied in detail – S-shaped and linear – with a total duration of the start-up transition process of 0.5, 1, 2, 3, and 4 s. It was established that the use of frequency-controlled starting significantly reduces undesirable load indicators compared to direct-on-line uncontrolled starting of equipment under a blockage. For a smooth S-shaped profile with a duration of 2 s, the coefficient of maximum torque in the elastic coupling decreases from 2.02 to 1.07 (by 47.0%), the coefficient of maximum electromagnetic torque of the motor – from 4.20 to 1.18 (by 71.9%), and the coefficient of maximum longitudinal force in the belt – from 2.84 to 1.20 (by 57.7%). For a linear characteristic with a similar duration of 2 s, the corresponding peak decreases are 38.1%, 72.9%, and 56.0%. It was mathematically shown that the S-shaped profile of increasing frequency provides significantly better consistency between limiting instantaneous peak loads and maintaining moderate root-mean-square (RMS) values of dynamic and energy parameters of the system. The most balanced and rational mode in the studied range of factors is an S-shaped start lasting 2 s, which simultaneously minimises shock loads in the coupling, drive, and belt without excessive thermal increase in the acceleration duration. The results obtained can be used in the design and engineering configuration of industrial frequency converters of belt conveyors to improve their overall energy efficiency, durability of expensive belts, and operational reliability of the entire electromechanical drive