A system intended to detect, classify, and track radioactive sources in moving vehicle traffic is under development at Lawrence Livermore National Laboratory (LLNL). This system will fuse information from a network of sensor suites to provide real time tracking of the location of vehicles emitting gamma and/or neutron radiation. This work examined aspects of the source terms of interest and applicable gamma detection technologies for passive detection of emitted gamma radiation. The severe restriction placed on the length of count due to motion of the source is presented. Legitimate gamma sources expected in traffic are discussed. The requirement to accurately classify and discriminate against these "nuisance" sources and cost restraints dictate the choice of NaI(Tl) detectors for this application. The development of a capability to automatically analyze short duration, low signal-to-noise NaI(Tl) spectra collected from vehicles passing a large, stationary detector is reported. The analysis must reliably discriminate between sources commonly transported in motor vehicles and alert on the presence of sources of interest. A library of NaI(Tl) spectra for 33 gamma emitting sources was generated with MCNP4B Monte Carlo modeling. These simulated spectra were used as parent distributions, from which multiple realizations of short duration spectra were sampled. Principal component analysis (PCA) of this data set yielded eigenvectors that enable the conversion of unknown spectra into principal component space (PCS). An algorithm using least squares fitting of the positions of library sources in PCS as basis functions, capable of identifying library nuclides in unidentified spectra, is reported. Analysis results for experimental spectra are compared against those achieved using simulated spectra. A valuable characteristic of this method is its ability to identify sources despite unknown shielding geometries. The successful identification of radionuclides and false identification rates found were excellent for the signal levels involved. For many of the sources, identification performance against experimental spectra was somewhat poorer than found using simulated spectra. The results demonstrate that the PCA-based algorithm is capable of high success rates in identifying sources in short duration, low signal-to-noise NaI(Tl) spectra. / Graduation date: 2001

Adjustable Speed Drive (ASD) systems are widely used in industry to effectively improve process efficiency and control. Typically, an ASD system consists of a motor with its speed controlled by a power electronics converter via varying the amplitude and frequency of the input voltage. However, several abnormal insulation failures of random wound motors in ASD applications have been reported. These failures were related to voltage transients caused by inverters employing fast insulated Gate Bipolar Transistors (IGBTs) combined with long cables that connect motors to inverters. This thesis further analyzes the distribution of voltage waveforms generated by a pulse-width modulated (PWM) inverter at the motor terminals and windings. Experimental work was performed at the Motor Systems and Resource Facility (MSRF) at Oregon State University on a specially made 5hp induction motor with taps from the first and second coil and from the first four and last two turns in every phase. Tests were performed with long and short cables and results are compared. A simple simulation model was created in PSpice and used to predict maximum voltage transients across coils and turns. The validation of the model is demonstrated by its capability to predict most of the experimental results. / Graduation date: 2000

An AC/AC converter has been designed and implemented for the purpose of providing a modular drive system with a Brushless Doubly-Fed Machine (BDFM.) This converter is to be used in laboratory testing and also as part of a demonstration system in the field. All hardware needed to start and run the BDFM is now consolidated into a single NEMA standard frame electrical equipment box. This allows easy transportation and setup of the drive system, and will enable the BDFM drive system to be directly compared with existing induction machine based drive systems. Converter subsystem overviews in the body of the text and comprehensive schematics in the appendices of this thesis describe all circuitry included in the drive system. Sufficient construction detail is given to allow for duplication of this converter by qualified technical personnel. While not tailored for mass production, this converter may provide a starting point for a commercially viable design. / Graduation date: 1998

The Motor Systems Resource Facility (MSRF) at Oregon State University presently conducts a variety of steady state tests on Motors and Generators, with ratings of upto 300Hp.(225kW), using a dynamometer. The dynamometer consists of an induction motor fed by a power electronic converter. A control computer uses a serial link, to send the desired steady state values of speed or torque to the converter. The objective of the work of this thesis was the conversion of the existing control interface, to one that could support programmable dynamic operation. Some of the capabilities that the resulting system has acquired, include the ability to simulate a general, predefined torque or speed profile, from a generalised polynomial function, a sine wave of torque or speed added to a constant offset, and a general purpose mode which allows the user to specify an atypical profile. The conversion to dynamic operation, permits the study and laboratory simulation of dynamic effects like the Sub-Synchronous Resonance phenomenon observed in turbine- generator sets attached to the power grid, the effect of "tower shadow" on wind power generation, time-varying load profiles, testing of machines under real world operating situations etc. Several tests were performed to ensure that the actual speed/torque profiles obtained from the machine, corresponded to the reference profiles specified in each case. Measured performance of specific examples is given. / Graduation date: 1999

A 300 hp motor and generator testing facility is being completed at Oregon State University. The testing center is the largest independent testing facility west of the Mississippi River. This regional resource center will incorporate state-of-the-art features that set it apart from other testing facilities. An induction machine with a modem regenerative power electronic converter is being used as the dynamometer. This regenerative dynamometer system significantly reduces the amount of power necessary for testing, allows for extremely flexible computer controlled testing, and is able to test adjustable speed machine systems from 100-4000 r/min. The dynamometer system is able to fully test both motors and generators of 240 hp from no-load to 125% rated load. A virtual instrumentation system provides tremendous flexibility and measures instantaneous, rms, and spectral signal values. Because the system is designed for testing over a wide speed range, it is necessary that all dynamometer losses are isolated and tabulated for the entire speed range. Initial fixed speed testing was performed on a 60 hp induction motor and standard report formats were generated for this and future test center use. The results were compared to the manufacturer's original testing data. To demonstrate the ability to test generators by using the dynamometer as a prime mover, a set of tests were also performed on a synchronous machine in accordance with IEEE standards. / Graduation date: 1996

By combining new robot control systems with piezoelectric motors and micromechanics, we propose creating micromechanical systems which are small, cheap and completely autonomous. We have fabricated small - a few millimeters in diameter - piezoelectric motors using ferroelectric thin films and consisting of two pieces: a stator and a rotor. The stationary stator includes a piezoelectric film in which we induce bending in the form of a traveling wave. Anything which sits atop the stator is propelled by the wave. A small glass lens placed upon the stator becomes the spinning rotor. Using thin films of PZT on silicon nitride memebranes, various types of actuator structures have been fabricated.

Thesis (Ph.D. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.

The exceptional feature of the brushless doubly-fed machine is the lack of need for frequent replacement of brushes. The inherent instability of this machine has to be overcome for its application in adjustable speed drives and variable speed generation systems. Specific objectives were: to study the characteristics of the machine pertinent to its application in adjustable speed drives and variable speed generation systems, to develop a stabilizer depending on the nature of the instability. The brushless doubly-fed machine was found to be unstable over much of the useful operating range. A digital feedback control was implemented using a combination of hardware and software elements/to stabilize the machine. The feedback system was a band pass filter. The software was developed with a processing time fast enough to match the speed of response required by the stabilizer to overcome the unstable oscillations. The performance of the machine was compared with and without the stabilizer to test its effectiveness. Stable operation was achieved over the entire operating region. / Graduation date: 1991

The Brushless Doubly-Fed Machine (BDFM) has recently become an important research topic in the field of variable-speed AC drives. In recent studies, the BDFM has shown significant potential for improving the reliability and performance of AC drive systems, as well as reducing total system cost. While the BDFM offers several advantages over existing AC drives in steady-state operation, it suffers from dynamic instabilities and slow response times, and a feedback control system is necessary. The mathematics of the BDFM are much more complicated than those of a singly-fed machine, and thus traditional control methods can't be applied. In this thesis, a control method known as "Direct Torque Control" has been adapted from that of a singly-fed induction machine and successfully applied to the BDFM. The thesis begins by discussing the background of the BDFM, its open-loop operating characteristics, and some of the control considerations. The reduced-order system differential equations are introduced, and it is noted that they are coupled and nonlinear. Furthermore, all state variables are time-varying (but periodic), even in steady-state operation. In the controller development, it is found that a linear relationship exists between the desired torque/flux-level change and the d-q voltages to be applied to the control winding of the machine via the power-electronic converter. This linear relationship, together with a one-step-ahead predictor to compensate for computational delay, is successfully used to control the speed and efficiency of the machine, for a wide range of speeds and load torques. Numerous open- vs. closed-loop simulations are compared and summarized, and it is found that the performance of the BDFM is greatly improved in the closed-loop, with faster response and reduced oscillation. Further simulations investigating the robustness of the controller are summarized, and it is found that the controller is reasonably insensitive to errors in most of the the static machine parameters. Hardware implementation is briefly discussed but is not complete; laboratory results are not yet available but should be soon. Future controller considerations are then discussed; included among the recommendations are an on-line parameter estimator for use in adaptive control, and a controller for generator applications of the BDFM. / Graduation date: 1993

The loads on the electrical systems of automobiles are projected to increase significantly in the near future. This will result in a requirement for improved efficiency over the present-day car alternators. An alternative scheme proposed at Oregon State University employs a Brushless Doubly-Fed Machine (BDFM) as an alternator. This thesis begins with a study and characterization of the existing car alternator system. The configuration of the proposed scheme is discussed. In the proposed configuration, the power winding of the machine generates the bulk of the power and the control winding provides the excitation. The power winding feeds a power rectifier, which in turn charges the battery in an automobile. The control winding is supplied through an inverter. Issues related to inverter and rectifier design are discussed. A 3-phase pulse width modulated inverter and a bridge rectifier were developed and tested for performance. A PSPICE simulation model for the rectifier was developed and results are compared with laboratory tests. A Voltage Regulator Circuit (VRC) and an Efficiency Maximizer Unit (EMU) for the system are designed and developed. A prototype alternator system is tested and the principle of efficiency maximization is verified. Finally. the comparative performance of the the existing and the proposed system is discussed and some recommendations for further improvements in the prototype system are made. / Graduation date: 1992