Thesis. 1978. Ocean E.--Massachusetts Institute of Technology. Dept. of Ocean Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ocean E.

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This thesis presents a study on core loss calculations in rotating electrical machines. The basic concepts concerning magnetic moments, ferromagnetism, magnetic domains and magnetic hysteresis are introduced. The three-term models for alternating and rotational core losses in electrical steel sheets are presented. Several core loss measurement techniques are reviewed and an experiment is carried out to measure the total core losses in an electrical sheet steel sample under alternating and rotational magnetic fields of various frequencies and amplitudes. The coefficients in the loss models for alternating and rotational core losses are obtained through curve fitting process. The theory of electromagnetic fields is presented through the Maxwell equations and field scalar equations. A detailed review on core loss models for rotating electrical machines is presented. A rotational core loss model is adopted to calculate the core losses in a PM motor. The total core loss in the PM motor is obtained by summing the element losses using a MATLAB program. An experiment is conducted to measure the total core loss in the PM motor. The calculated total core loss in the PM motor is compared with the experimental results. The calculated total core losses are about 19% lower than the tested results. Various possible causes for this discrepancy are discussed / Master of Engineering (Hons)

Many high performance drive applications require wide Constant Power Speed Range (CPSR) for efficient use of energy. The examples of such applications are the starter alternator system of automobiles proposed for the 42V PowerNet, traction in the hybrid/electric vehicle, wind power generator etc. The Permanent Magnet (PM) machine is the natural choice of such niche applications because of their higher efficiency and compact size. However, the Surface Permanent Magnet (SPM) machine with sine distributed winding and radially-laminated Interior Permanent Magnet (IPM) machine with conventional structure has very limited or zero flux-weakening capability. The flux-weakening capability of the SPM machine can be improved by using concentrated, fractional-slot stator but here well-known advantages of the sine distributed winding are needed to be compromised. In the IPM machine, fluxweakening was improved using axial lamination and more than two magnet layers per pole. However, the construction of such IPM machine is complicated and expensive. This thesis presents design and analysis of a new type of the Interior Permanent Magnet (IPM) machine that have a very wide Constant Power Speed Range (CPSR) without compromising simplicity of construction and advantages of the distribution winding. In the new IPM machine, the magnet poles were segmented in the radially direction and the iron bridges between magnet segments provide for additional paths of flux-canalization to give the rotor an inherent capability of fluxweakening. Consequently, a very wide constant power speed range can be achieved in such machines. The proposed IPM machine of this work was referred as the Segmented IPM machine. The thesis focuses on the optimization of the Segmented IPM machine in a 42V environment of the automobile. First, for the conceptual evaluation a 4 pole, 550W Segmented Magnet IPM machine was optimized using finite element analysis. The parameters were calculated for prediction of the steady-state and transient performances. The torque- and power-speed capability were estimated using time-step, circuit-coupled finite element analysis. The cogging torque and variation of iron loss with frequency were also investigated during the design process. A prototype machine was constructed on the basis of the optimized design. The steady-state and transient performances of the prototype machine were measured and compared with the predicted results for experimental verification. The measured performance analysis was found to match very well with the predicted results. The measured torque- and power-speed capability of the Segmented IPM machine was also compared to those of a conventional, non-segmented IPM machine of similar rating and size. The thesis also presents the optimized design of a 6kW, 12 pole Segmented Magnet IPM machine for application in the Integrated Starter Alternator (ISA) of the electric/hybrid vehicle. It can be concluded from the predicted steady-state analysis of the 6 kW, 12 pole Segmented Magnet IPM machine that it should be able to satisfy most of the required criteria of an ISA with appropriate design optimization.

"October 2002" / Bibliography: p. 219-228. / xi, 229 p. : ill. (some col.), plates (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Proposes a robust indirect position sensing technique implemented in real time using a DSP based motor controller. This is based on a rotor position estimation using the measured phase voltages and currents of the motor. An incremental algorithm is used to estimate the flux linkage increments, which eliminates the integration involved in the flux linkage estimation. This feature provides a wider operating speed range and robustness. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 2002

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

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