Modeling of the controlled dc-drives without current and speed feedback

This paper present simulation results of controlled dc-machines fed by thyristor single phase line-commutated converters in discontinuous current mode, without using a current and speed feedback signals. The required controller comprises open-loop speed control and a inner current control with observer. Current observer calculates the average of discontinuous current, dependent on two binary values: generated firing angle and measured current flow angle. First part addresses the control system and his structure. Second part is a detail description of mathematical model of the presented control system implemented in SIMULINK. At the end of the paper simulation results are shown, which verifies possibility of implementing this very economical control concept.