A brushless doubly-fed machine (BDFM) is a single-frame, self-cascaded induction machine capable of operating in both the induction and the synchronous modes. This thesis presents some important advances concerning dynamic modeling, simulation and analysis of the BDFM. Initially, a two-axis model and its associated parameters are developed and calculated. The development of the model is not subject to the commonly made assumption that the BDFM is electromagnetically equivalent to two wound rotor induction motors in cascade connection. Instead, the model is derived from a rigorous mathematical transformation of a detailed machine design model. This novel approach emphasizes not only the analysis of the machine performance in both dynamic and steady state conditions, but also the design aspects of the machine by correlating the machine performance with the actual machine parameters computed from machine geometry. Using the two-axis model, simulation of the machine dynamic performance in all conceivable modes of operation is carried out and the results are compared with test data available with good correlation. Steady state models, under certain assumptions, are derived based on the two-axis model. For the synchronous mode, motoring operation, a solution technique is developed and utilized to perform steady state performance analysis of the BDFM. Finally, stability analysis of the machine is examined using the linearized version of the two-axis model. Since the linearized two-axis model of the BDFM is time-varying, commonly used eigenvalue analysis techniques cannot be employed directly to investigate the stability characteristics of the machine. However, since the system matrix is a periodic function of time, the theory of Floquet is introduced so that the original linear time-varying system of equations are transformed into a set of equivalent system of equations with a constant system matrix. Eigenvalue analysis is then applied to analyze the stability of the BDFM system over a wide speed range. Predictions by the eigenvalue analysis are correlated with test data. The study concludes that the proposed two-axis model is a good representation of the BDFM for dynamics, steady state, stability investigations of the machine and further development of control strategies for the proposed BDFM system for adjustable speed drive and variable speed generation applications. / Graduation date: 1991

This thesis focuses on compact brushless DC fan motor, drive circuit structure of motor is proposed, several functions such as output low current limit circuit and low rotation speed limit are added in order to increase robustness of drive circuit. Besides, speed feedback controller is used to solve several problems such as high frequency full speed exciting noise and high power dissipation which occurs in open loop rotation speed control circuit.With regard to BLDC fan motors generally use Hall sensor to detect rotor position, this research proposes sensorless control technology for the purpose of reducing circuit cost and motor size.

This thesis focues on the realization of small size brushless DC fan motor driving circuit, adding the protection circuit of commutation to H bridge, in addition, the function of low current limiter, and slow rotation speed limiter are also implemented to the more stable rotation. With regard to the strategy of rotation speed control, we use speed feedback controller to slove noise problem which occurs in high frequency full speed excited and adopt thermistor accompanied with the voltage divided circuit to achieve speed control with temperature. Finally, for the sake of reducing the cost and shrinking the size of system, the design of sensorless mode is proposed and the rotation speed control system is realized under sensorless mode.

Electric propulsion has been studied for a long time. Most of the electrically propelled vehicles that have been developed however have been ground vehicles. Recent research by NASA has promoted the development of electric aircraft. Most aircraft are currently powered by heavy gas turbine engines that require fueling. The development of electric motors to replace gas turbines would be a big step towards accomplishing more efficient aircraft propulsion. The primary objective of this research extends previous work by developing a high power density motor for aircraft propulsion. This design is novel because it does not require a dynamometer to provide the torque to drive the vehicle. Equally important for successful testing of the motor was the design and development of a spin pit interface that was used as a containment vessel during testing. The research led to a designed, fabricated, assembled, modeled, and tested motor. Voltages, currents and power outputs of the motor were measured and used to determine the motor’s efficiency. The gaps between the motor’s magnets were related to the current and power it produced, and modifications were made based on this relation. The vibrations of the motor were also studied and MATLAB codes were written and used to reduce these vibrations. Significant among the objectives was monitoring the temperatures of the motor’s stators due to their close association with the rotating parts. The windage and friction losses between the stators and the magnets provided a challenging hurdle in the research. These windage and friction losses were predicted, analyzed and measured, and modifications were made to reduce them. Finally, results were compiled, tabulated, and analyzed. Results obtained before and after the modifications were compared, and these comparisons were used to assess the necessity and effectiveness of the modifications. The efficiency of the motor was found to be 82.9% and the power density was evaluated as 33.1 W/lb based on a rotor weight of 497 lb. It was concluded that the litz wire used in the motor has high, frequency related impedances that could be reduced but not eliminated.

Thesis (M.S.) in Electrical Engineering--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaf 49).

A design for a novel tubular high-precision direct-drive brushless linear motor has been developed. The novelty of the design lies in the orientation of the magnets in the mover. In conventional linear motors the magnets of the armature are arranged such that the attractive poles are adjacent throughout, in an NS-NS-NS orientation, where N denotes the north pole and S denotes the south pole of the magnet. In the new design, the magnets in the moving part are oriented in an NS-NS-SN-SN orientation. This change in orientation yields greater magnetic field intensity near the like-pole region. The magnets of the mover are encased within a brass tube, which slides through a three-phase array of current-carrying coils. As the coils are powered, they induce a force on the permanent magnets according to the Lorentz force equation. The primary advantages of the motor are its compact nature, fast, precise positioning due to its low-mass moving part, direct actuation, extended travel range, and ability to extend beyond its base. The linear motor is used in conjunction with a position sensor, power amplifiers, and a controller to form a complete solution for positioning and actuation requirements. Controllers were developed for two applications, with a lead-lag as the backbone of each. For the first application, the principal requirements are for fast rise and settling times. For the second application, the primary requirement is for near-zero overshoot. With the controller for application 1, the motor has a rise time of 55 ms, a settling time of 600 ms, and 65% overshoot. With the controller for application 2 implemented, the motor has a rise time of 1 s, a settling time of 2.5 s, and 0.2% overshoot. The maximum force capability of the motor is measured to be 26.4 N. The positioning resolution is 35 ?m. This thesis discusses the motor's physical design, construction, implementation, testing, and tuning. It includes specifications of the components of the motor and other necessary equipment, desired and actual motor performance, and the primary limitations on the precision of the system.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 240-266). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 151-164). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references.

Aujourd’hui, la conception de moteurs électriques est stratégique dans l’activité industrielle.La poussée des véhicules électriques avec la recherche de fortes efficacités pour des raisons d’autonomie stimule cette activité. Ce travail de thèse entre dans un même contexte avec une contrainte de coût très importante liée au développement de produit dans le domaine du grand public.Cette thèse est une contribution à la conception de machines électriques dans un contexte industriel. Elle intègre les coûts et les contraintes d’un industriel avec la prise en compte du processus d’industrialisation du moteur ainsi que les variations des coûts de matières premières. Une plateforme d’éco-conception de moteur sera présentée intégrant différentes topologies.La première partie de ce mémoire présente un bref état de l’art sur les machines synchrones à aimants permanents (MSAP) qui permet de faire le choix des topologies pertinentes.Les contraintes industrielles sont considérées avec la présentation d’un modèle industriel sur les coûts liés à la fabrication des moteurs et un modèle économique sur les fluctuations des coûts des matières premières.Dans une seconde partie, ces topologies seront optimisées à l’aide des algorithmes génétiques pour une application dans le domaine de la ventilation. Cette étude a mis en avant l’écart entre la topologie MSAP en surface avec la ferrite et la MSAP insérés avec du néodyme du point de vue économique et performance. À la suite de cette comparaison, une nouvelle topologie correspondant à un mélange des deux types d’aimants dans le rotor est introduite pour s’orienter sur une configuration à concentration de flux.Des mesures expérimentales valident les résultats présentés dans cette thèse sur les topologies MSAP en surface et MSAP insérés, la topologie à concentration de flux sera prototypée ultérieurement. / Nowadays, design of electric motors is strategic in industrial activity. The thrust of electric vehicles stimulates this activity. Indeed, high efficiencies are needed to seek autonomy.The same constraints apply in the consumer product industry along with a very significant cost concern.This thesis is a contribution to the design of electrical machines in an industrial context.An eco-design platform will be presented. It integrates the costs and the constraints of an industrialist: the process of mass production and raw materials cost variations.The first part of this paper presents a brief state of the art on BLDC motors. Relevant topologies are selected for the platform. Two new models are proposed in this work. The first one is an industrial model taking into account costs related to mass production. The second one is an economic model which considers raw material cost fluctuations.In a second part, surface permanent magnet (SPM) and the inserted permanent magnet (IPM) topologies will be optimized using genetic algorithms. An application in the ventilation field is chosen to compare these topologies. This study highlighted the gap between both topologies concerning cost and performance. As a result of this comparison, a flux concentration topology is presented. A mixture of two types of magnets in the rotor allow to reach a technico economic compromise.Experimental measurements validate the results presented in this thesis on SPM and IPM topologies. The flux concentration topology will be prototyped in future works.