Abstract: In a drive system for a grinding mill the load torque plus frictional torque may increase considerably as a loaded mill is inched from its rest position and will suddenly decrease when the load tumbles or cascades. The applied torque or driving torque must increase at a corresponding rate and should also decrease when the load cascades. If the applied torque exceeds by a significant amount the load torque plus frictional torque, a destructive hammering will occur in the gear train and this will be generally proportional to the excess of applied torque for a synchronous motor drive. The drive system has a DC source which is commutated by a commutating device to provide a low frequency stepped alternating voltage to the stator windings of the synchronous motors of the drive system for inching. The output of the DC source has an alternating current component which varies as the difference between the applied torque and the load torque plus frictional torque.

Abstract: This disclosure relates to a parallel speed regulator system for a plurality of d.c. motors operated on a common bus having a single armature electrical supply. The speed control, current limiting, and field current controllers for each motor are arranged in parallel and connected to a resistor-diode switching network to provide a switching order of priority: (1) maximum and minimum field current controllers (2) armature current limit controllers and (3) speed controller. This parallel speed regulator system provides all the inherent advantages of the multiloop controller arrangement together with automatic adjustments which are a function of the instantaneous motor operating point, so that the dynamic response of the motor remains the same regardless of perturbations in the operating points.

Abstract: A d.c. motor control system includes a pair of armature windings mounted on a single rotor or on a pair of mechanically coupled rotors, and a field winding or windings. The system includes switch means operable to effect a change in the electrical connections of the armature windings to a pair of electrical supply terminals and means for effecting variations of the current flowing in the field winding or windings.