Microprocessor Control of Position or Speed of an SCR DC Motor Drive

In silicon-controlled rectifier (SCR) dc motor drive control, it is desirable for a microprocessor to perform both the control law computations and the logical functions of SCR firing. However, because of their limited real-time capabilities, present-day microprocessors cannot accommodate excessively lengthy control algorithms. This paper presents a method, suitable for microprocessor implementation, of controlling the position or speed of an SCR dc motor drive which uses a half-wave single-phase supply. The state-space equations of the system are first obtained. The derivation of a simple control law is given next, followed by the stability and error analysis of the controller. Finally, it is shown from simulation experiments that the scheme is effective in controlling a 3-hp dc motor.