Date of Award

Spring 2003

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Electrical and Computer Engineering

First Advisor

Demerdash, Nabeel A.O.

Second Advisor

Brown, Ronald H.

Third Advisor

Yaz, Edwin E.


The effects of space harmonics arising from the topological geometries of the magnetic circuits and the continuously revolving magnetic saturation patterns within the magnetic circuits, as well as the machine winding layouts on torque and performance quality of polyphase ac and brushless de machines (AC&BDCMs) are studied. This study also includes the synergisms, which take place between these space harmonics and the time harmonics generated by the controller (drive) circuit electronic switching effects for the case studies of brushless de machines (BDCMs). Meanwhile, the effects of advanced phase current switching (advanced commutation or flux weakening) as well as pulse width modulation on torque quality and other performance aspects of BDCMs and their associated power conditioners are investigated and discussed. This work is accomplished through the development of PSpice-based electric machinery models, which fully include the circuit switching topology of the controllers (drives) for motors and electronically rectified loads for generators. The PSpice-based circuit models take into account the full impact of the space harmonics present in the machine phase windings' self and mutual inductances. This is done through inclusions of these space harmonic effects into the formulation of the state-space models and the resulting equivalent circuits of the AC&BDCMs by expressing the inductances in Fourier series form. Previous investigators that used PSpice for simulation of machine-drive systems relied heavily on DQO-type machine models which inherently neglect the space harmonics higher than the fundamental, and ABC models that did not involve space harmonics higher than those introduced by the fundamental components of flux and/or magnetomotive forces (mmfs). This is not the case in the present work because the ABC frame of reference formulations developed here include the full impact of the space harmonics present in these polyphase AC&BDCMs. This approach also eliminates the complications of mathematical transformation associated with DQO models, which precludes harmonics higher than the fundamental component in mmfs and airgap flux density waveforms. Accordingly, this neglects many important effects of space harmonics on current and voltage waveform as well as time-domain torque profiles. In addition, this model's natural ABC frame of reference readily enables one to compare the simulation and test results on any machine-power conditioner system. The case studies of AC&BDCMs under investigation include a 1.2-hp and a 15- hp BDCM, as well as a 14.3 kVA modified Lundell alternator (MLA). The inductance data needed for the PSpice simulations were obtained from previous detailed two dimensional and three dimensional finite element magnetic field analysis which had already been carried out by previous investigators. Finally, the validity and soundness of this PSpice modeling technique is verified by comparing the simulation results with the oscillograms of the test results obtained in previous investigation.



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