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published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

by Lam Chun-wing. / Chinese title: / Bibliography: leaves 131-135 / Thesis (M.Phil.)--Chinese University of Hong Kong, 1983

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

A relatively new development in the electric machines field has been the written-pole technology, of which the latest product is the large single-phase electric motor, the single phase Written-Pole Motor (WPM). The WPM is a synchronous, permanent-magnet single-phase motor having a weak rotor cage for start-up which in addition exhibits significant hysteresis effects at speeds below or above true synchronism. The electrical configuration of the WPM places it in the capacitor-start capacitor-run category of single-phase motors, due to the large size and need for an approximation of a round rather than elliptic rotating magnetic field. This thesis presents the results of the research conducted by the author in the Motor Systems Resource Facility (MSRF) of the Electrical and Computer Engineering Department at Oregon State University. The thesis is structured into two main parts: Testing and Modeling. The tests conducted on the WPM were trying to independently verify manufacturer's claims with regards to efficiency, power factor, robustness, power-outage ride-through and furthermore to study the behaviour of the machine during voltage sags, overvoltages and undervoltages. Tests were conducting in order to develop a mathematical model from which the performance of the machine can be predicted. The modeling efforts were concentrated in the development of a comprehensive model which would include all three major aspects of the WPM, and the performance of the resulting model was compared with the sampled data. / Graduation date: 1999

The Brush less Doubly-Fed Machine (BDFM) has the potential to be a more cost effective replacement for conventional induction or synchronous machine drives. The BDFM has two stator windings: a power winding and a control winding. An electronic power converter of variable voltage and frequency is connected to the control winding and allows the speed of the machine to be adjusted synchronously. The power winding, by design, carries the majority of the current needed for operation, the control winding only a fraction of the current, thus enabling the converter rating to be as low as 25% of the rating of the machine depending on the speed range of operation. To date, only one specific stator pole-pair combination has been investigated, namely the 3/1 combination, where 3 and 1 refer to the power winding pole-pairs and the control winding pole-pair, respectively. Since the speed of the machine is dependent on the sum of the pole-pairs of the stator windings, a general pole numbered model is needed to evaluate the performance of such general machines with other pole-pair number machines. The BDFM describing system equations are transformed to the two axis (dq) rotor reference frame using a power invariant transformation. The analysis shows an additional term involving the common bar impedance which was not present in earlier analyses. The dynamic model is simplified to yield a steady state synchronous model. The synchronous frequency of analysis is investigated which results in two equivalent steady state models. The models developed can easily handle excitation of any frequency or sequence on the control winding without the use of an auxiliary model as used in previous analyses. The voltage forced model predictions match data taken for a 5 hp BDFM laboratory prototype, establishing the validity of the analysis. The model is used in illustrating the torque producing capabilities and unity power factor operation of the machine under a variety of inputs. Using the model, predictions are made on a different pole-pair combination machine (4/2 BDFM) for use as a 60 hp pump drive as an alternative to a 3/1 BDFM for the same application. / Graduation date: 1995