Laboratory Tests of a Speed Control System for Roadheader Cutting Heads

The paper presents selected results of the laboratory tests of the speed control system for the R-130 roadheader with an inverter-fed cutting heads drive. The results recorded for the variable speed system have been compared with the measurement obtained for the network supplied drive. There have been noticed some oscillations after rapid current overloads. They are due to the operation of the internal current controller of the PWM-inverter, The oscillations are fast decaying - so they prove the results of initial system stability checking. Generally, the automatic speed control, tracking the optimum speed level calculating by supervisory speed adjuster makes possible to better utilize the motor power throughout the whole cutting time. The better operating conditions of the motor cause increase in the whole system power efficiency (even in spite of additional losses in the inverter circuit) Additionally the sped control reduces dynamical overloads. This fact can have a positive influence on the whole system reliability. The speed control subsystem is a part of the whole control system which contains also close-loop boom angular position and velocity control circuits.