Walter G. Koellner

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Mining draglines have been powered by multiple motor-generator (M-G) sets for nearly one century and have been one of the last hold outs of this aged technology. A new technology with all alternating current (AC) static drives using insulated gate bipolar transistors (IGBT) and gearless synchronous ring motors has been developed to increase productivity and(More)
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(More)
The primary operating objective of mines is to optimize the cost per ton of material moved to remain profitable. In other words, this means moving the highest possible payload per hour while minimizing operating costs over the lifetime of the machines. Draglines remain a popular choice among other excavation machines because of their high productivity and(More)
This paper proposes the utilization of ultracapacitor as additional energy storage device in high power AC mining converters. A critical requirement for these converters is to be able to maintain a robust DC link under all operating conditions. However, due to lower switching frequencies of the IGBT devices, the bandwidth of the controllers is limited. As a(More)
In this paper, detailed modeling and control of the active front end (AFE) of AC drive mining applications specifically the shovel systems are presented. Through a nonlinear transformation and power balance fact, a linear model of the converter is developed which makes the controller independent of the operating points. Due to the low switching frequency(More)
After breathing a mix of 10% CO2 and 90% O2 or hyperbaric O2 (2 bar absolute) an appreciable rise of pO2 can be demonstrated by D.C. polarography in the scala tympani of the guinea pig chochlea. When test animals are made to breathe 100% pure O2 at normal pressure the rise of pO2 is significantly less pronounced. The observations made in these animal(More)
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