Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
Electrical and Computer Engineering
Demerdash, Nabeel A. O.
AC induction motor-drive systems are considered to be the backbone for numerous industrial processes as well as many other critical applications such as aerospace, medical equipment, thermal and nuclear power generation plants. This is in addition to various marine and land transportation systems. The wide-spread use of such motor-drive systems is mainly due to their reliability, high efficiency, controllability, and high power density. However, the utilization of such systems in numerous critical applications mandate extremely high levels of reliability and survivability. These applications were the main incentive to trigger numerous investigations in the areas of early fault diagnostics and reconfigurable fault-tolerant designs of such systems, such that a fault can be detected in an incipient stage in order to safely shutdown the system and avoid catastrophic failures, as well as minimize such systems' repair costs and downtimes. The other alternative was to isolate the fault and provide a reconfigurable arrangement that enables continued operation of such a motor-drive system with a tolerable/acceptable, though partially impaired performance. The main contribution of this dissertation is the conception and development of a new control strategy that allows Delta-connected induction motors to operate under a faulty two-phase open-Delta mode of operation with a resulting performance characterized by nearly balanced line currents and acceptable levels of torque pulsations in either the open-loop mode of operation, or the vector-controlled mode of operation. The main aim and accomplishment of this control strategy is to maintain a quality of performance of a two-phase open-Delta mode of operation of a faulty motor as close as possible to the quality of performance of such a motor under normal healthy three-phase Delta-connection. That is, one anticipates that such a procedure would be triggered after the process of isolating the faulty phase is accomplished successfully...