Real-Time Power Quality Measurements From a Conventional AC Dragline

A typical mining facility uses excavation machines like shovels, draglines, etc., for removing overburden and ores during the mining process. These machines are characterized by cyclic loads consisting of high peak power demands as well as regeneration phases. The peak power demand is often as high as 1.6 times the average demand. This kind of a load leads to voltage fluctuations, harmonics, power factor issues, etc., at the main substation. This paper shows that superior results are now achievable with Siemens AC mining drive control system for draglines. By utilizing staggered pulsewidth modulation pulsing and operating the drive with leading power factor, the voltage fluctuation and line-side harmonics are regulated. The data presented in this paper are from an actual operational ac dragline that is now under production.