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This thesis describes the development and implementation of new solutions to the power quality problems associated with large unbalanced and non-linear loads. The thesis was undertaken in the context of the fine glass industry and the development work was carried out at three production plants belonging to a world leading fine glass producer. In the process of fine glass production, furnaces are used to melt the silica mix into a liquid of treacle consistency. These furnaces are generally enclosed, except for several small orifices about 50 mm in diameter, which are located around their perimeter. Through these openings, glass blowers draw a working portion of this treacle like substance, using a hollow tube. By the use of a blowing and moulding technique the desired product is shaped. The process of manufacture of fine glass products is presently undergoing change due to the introduction of process automation by the leading manufacturers. Robotic machines are now replacing glass-cutters and craft blowers. Fine glass producers traditionally used many small gas or oil fired furnaces in order to allow blowers sufficient access and work space. Robotic production involves different requirements and this has given rise to a radical redesign of furnace construction. Large furnaces are now being constructed, each one capable of meeting a major portion of the requirements of one major producer. These furnaces consist of a multi-channel layout, arranged in order to facilitate the various types of robotic connection required to produce a variety of products. Electricity is being used to achieve the critical temperature and viscosity necessary for good quality control. New electrical problems are being encountered in the area of electrical supply, operation and control. Among these are the issue of electrical phase balancing and the generation of harmonic distortion on the connected electrical network. These problems can be so serious as to cause the entire furnace system to be inherently unreliable in normal operation. The possibility of system failure is serious and the consequential damages could run into many millions of Euro. This thesis aims to address and solve some of these design problems. The thesis describes and compares two new and untried approaches to the balancing of large two-phase loads across three phases and shows how these have been designed and implemented. It also describes a new design method and computer programme for the construction of harmonic filters to solve the harmonic problems associated with this type of load.
O'Kelly, Hugh (Thesis), "Phase balancing and harmonic mitigation for large electrical loads" (2003). Masters. Paper 13.