Behavior of a drive system consisting of two DC motors with elastic shafts driving the Yankee drying cylinder of a tissue paper machine

In this paper the behavior of elastic shafts in a drive system consisting of two D.C. motors driving the Yankee drying cylinder of a tissue paper machine is investigated. The motors are fed by two 6-pulse thyristor converters connected to the same power transformer. The master motor has a tachogenerator to measure the speed of the system. Control logic is proposed to control the torque of the two DC motors. The control can be achieved in such a way that the two motors contribute the same amount to the total load in the case that the DC motors are identical, or contribute partly to the total load and proportionally to their nominal torques in the case that the two motors are not identical. The adjustment of the acceleration time and the parameters of the PI controllers is investigated in order to keep the maximum armature current below the limit of maximum permissible current and to achieve an optimum speed response of the system. The use of different elastic shafts (different stiffness) connected between DC motors and gearbox is investigated. The shaft of the Yankee drying cylinder is so thick that it can be considered as a stiff shaft without elasticity. The analysis of the system is realized using the SIMULINK software. Characteristic simulation results are presented.