A New Speed Control System for DC Motors Using GTO Converter and its Application to Elevators

A dc motor control system using a new GTO converter, is developed for an intermediate-speed elevator (2.5-m/s rated speed and 1000-kg load). Its features include 1) a main circuit control system composed of pulsewidth and phase controls, 2) a circuit to suppress the overvoltage which occurs when the GTO is turned off, 3) direct digital control which is composed of an acceleration control to compensate for lag time in the field current response and a self-correcting function to compensate for landing error. Application of the control system provided a higher power factor and smaller power consumption than a conventional control system.