Oscillatory torque caused by dead time in the current control of high power gearless mills

In modern high energy industrial processes, high power converters are one of the most important topics in terms of efficiency, energy savings and dynamic behaviour of all electrical drives. In our time, synchronous machines are used in many high power applications, like electric generation (hydroelectric and nuclear plants, etc) transportation (trains, cars, etc), and many more. In the mining industry multipulse cycloconverters are used to feed high power gearless SAG mills, which ones are a critical stage in the entire mining process. So the reliability of the electrical and mechanical behaviour of the drive it is fundamental. If the converter has an inadequate control or modulation technique the electric machine could be facing a great mechanical stress [13], which could damage it. The free circulating current configuration, used in many multipulse cycloconverter topologies, has a dead time implementation, where the output current it is very close to zero. This paper presents the electrical impact, in terms of the oscillatory torque, of this dead time in the current control of gearless SAG mills.