VARIABLE FREQUENCY DRIVE OF GRAIN MACHINE CONVEYOR WITH IMPROVED QUALITY INDICATORS

Purpose. The article explored options for control systems for the electric drive of grain-metal machine conveyor to stabilize the speed of conveyor belt when the load changes. Methodology. A control system is proposed that implements the principles of subordinate regulation and is supplemented by compensatory feedbacks in the control channels of active and reactive energy. The calculation of the regulators and the modeling of the system operation have been completed. The analysis of the obtained characteristics showed that the synthesized system is characterized by good quality indicators. However, the characteristics were obtained for the case of known parameters of an asynchronous machine and adjusting the regulators for these parameters. Studies have shown that for the proposed structure, the most significant is the incorrect determination of the inductive reactances of the stator and rotor of asynchronous machine. So, when the inductance de- viates by 30%, significant fluctuations occur in the subordinate regulation system. Complex solution to the problem of providing low sensitivity to parametric and coordinate disturbances and an increase in dynamic and static accuracy can be obtained in a class of systems, that are stable with an unlimited increase in the gain, as a solution to the problem of ana- lytical design of optimal regulators based on the modified symmetry principle. The regulators of the reactive energy transmission channel with series-parallel correction, which are modified PID structures, have been synthesized. Regulators with sequential correction with PID and PIDD2 structures are synthesized for the active energy transmission channel. Results. Analysis of the obtained results of characteristics showed, that the optimal control system is characterized by better quality indicators in comparison with the classical system of subordinate regulation and practically insensitive to changes in the parameters of the electric drive. Originality. The results of mathematical modeling confirmed the possi- bility of using control systems synthesized as a solution to the problem of analytical design of optimal controllers based on the modified symmetry principle, to improve the quality indicators of the AC electric drive of the grain thrower con- veyor. Practical value. The use of the proposed optimal control system will provide the possibility of stabilizing the speed of the conveyor belt of the grain thrower, which will reduce the percentage of injured and damaged grain. References 16. Figures 14.