Abstract: A control system for energizing a direct current (DC) motor with alternating current (AC) power includes a first voltage sensor for a peak voltage of AC power; a second voltage sensor for a counter electromotive force (EMF) of the motor; a current sensor for an armature current of the motor; a digital processor having a first current controller responding to sensed armature current and a current reference, a cooperating second current controller responding to sensed peak voltage, sensed counter EMF and the current reference signal, and a gating circuit responding to the controllers; and a thyristor converter circuit sequentially gating portions of half cycles of AC power to the motor in response to firing signals from the gating circuit. The controllers may control a gate angle of the firing signals, the control system may include a third voltage sensor for a terminal voltage of the motor, and the armature current may have discontinuous and continuous waveforms.

Abstract: A control system for one or more dc motors in which thyristor power modules selectively gate portions of half cycles of ac voltage to the motor field and armature windings, has digitally implemented parallel inner control loops for the armature which each generate an intermediate control signal to which proportional plus derivative control action has been applied. Logic selects the intermediate control signal which phases back firing pulses for the thyristor power modules the most for application to a common digital integrator which produces a control signal having proportional plus integral control action. The voltage across each of the thyristors is monitored and used to detect continuous and discontinuous current operation for adjusting integrator gain.