Thesis (PhD)--University of South Australia, 1999

[Truncated Abstract] This thesis describes investigations carried out in the development of a wind powered generation system suitable for interconnection with a power grid ... The simplicity and flexibility exhibited by the induction machines in providing electromechanical energy conversion make it the most favoured choice for wind-powered systems operated in parallel with an existing powers system. Although not as common as the ‘squirrel cage’ induction machine, the slip-ring type has several attractive features in providing constant-frequency ac power when driven from a varaible-speed source such as a wind turbine. The fundamental energy conversion properties of the induction machine system are studied in order to determine the suitability of these systems for constant-frequency variable-speed electric power generation. Two distinct control policies are formulated: (i) optimising power from the wind when the generator is connected to an ‘infinite’ bus bar and, (ii), scheduling a constant output power irrespective of fluctuations in wind speed when the generator is operated in parallel with a ‘weak grid’.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--Ohio University, August, 1999. / Title from PDF t.p.

Thesis (Ph. D.)--University of Hong Kong, 1991.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.)--McMaster University, 2001 / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Recent failures of large induction machines due to rotor bar breaks have become a major industrial concern in South Africa. These failures have occurred while applying current condition monitoring methods. This would imply that current theories are either inadequate or badly implemented. This thesis investigates two currently used condition monitoring strategies which focus on monitoring the stator current and axial vibration to detect bar breaks as well as a third method which involves putting destructive shaft voltages to good use and using this signal to diagnose rotor defects. This document begins by familiarizing the reader with two conventional approaches which involve monitoring the stator current and the axial vibration to detect rotor bar breaks. Thereafter the origins of shaft voltage are discussed and its use as a condition monitoring tool is first theoretically derived and then validated by finite element simulations. A thorough discussion of the measurement equipment required is presented and ultimately the performance of these three methods is tested by means of a laboratory measurement as well as two on-site measurements. The results from these measurements suggest that when making proper use of both conventional condition monitoring methods, these methods have a 50% success rate in the detection of rotor bar breaks. The alternative method investigated, which involves monitoring the shaft voltage, has a 75% success rate in the detection of rotor bar breaks. This highlights the use of shaft voltage as a condition monitoring tool. / Dr. S. R. Holm Prof. W. A. Cronje