High-speed single-phase permanent magnet brushless DC motor.

Due to high efficiency, high power density and low cost, single-phase permanent magnet brushless DC motor has increasingly been used in industrial and domestic applications. This thesis focuses on the design and analysis of high-speed, single-phase, conventional and flux-switching permanent magnet brush less DC motors. This thesis presents a comparative study of conventional three-phase and single-phase permanent magnet brush less DC motors, which operate at 45,OOOrpm with I.lkW output power for the pump application, in terms of their machine design, drive system and electromagnetic performance. It is found that the single-phase permanent magnet brush less DC motor has a relatively lower drive system cost without significantly compromising the electromagnetic performance. Further, significant rotor eddy current loss exists in both motors. Hence, the analytical models are developed to predict the rotor eddy current loss which is resulted from the armature reaction field. By comparing with the 2D finite element method (FEM) predicted results, good agreement is obtained over the full speed range if the eddy current reaction field is taken into account. FEM is further employed to investigate open-circuit, armature and on-load rotor eddy current losses of the permanent magnet brushless DC motors. Particular emphasis is placed on the single-phase motor having an eccentric airgap with consideration for degree of airgap eccentricity, excitation current waveform, magnet segmentation, thickness and electrical conductivity of the retaining sleeve. The single-phase flux switching permanent magnet motor, which operates at 100,000rpm with 1.2kW output power for the automotive electrical turbo-charger application, is also investigated. Its operational principle is introduced and winding topologies are investigated. In addition, the chamfered rotor pole is optimised to improve the starting capability. In order to investigate the influence of significant end leakage-flux, a 3D lumped circuit magnetic model is developed to predict the back-EMF and the inductance and validated through experiment. This model is also employed to optimise the rotor pole width for increasing the motor power density and to investigate the relationship between the magnet dimensions and the motor end effect. Finally, the dynamic simulation models are developed to predict the dynamic electromagnetic performance and experimentally validated for a three-phase and a single-phase permanent magnet brush less DC motor, and a single-phase flux switching permanent magnet motor

A very high speed switched reluctance generator

The thesis investigates a high speed switched reluctance (SR) generator suitable for applications such as aerospace and turbo-charged ground vehicles. The generator is two-phase with 16-8 stator-rotor poles. The stator is 70 mm OD by 25 mm core length made of soft ferrite. The rotor comprises 30 pm laminations of amorphous alloy chosen for its mechanical strength. The rotor of the generator was mounted on the protruding shaft of an air turbine and extensive tests were performed at a variety of speeds and supply voltages. The generator is shown to be capable of delivering around 280 Watts to a resistive load at 60,000 rpm, and 60 volts, with an estimated efficiency of around 77%. The thesis describes in detail the electromagnetic and mechanical construction of the generator and presents a comprehensive survey of operating waveforms and performance measurements. The design utilises a simple magnetic model for the SR generator based on a quasi-linear flux-current characteristics which are shown to provide a very useful tool for performance prediction

Dovetail rotor poles in synchronous permanent magnet and reluctance machines

Robust synchronous permanent magnet and reluctance machine designs are developed. In the designs, the rotor structure is simple and strong and the leakage flux is relatively small. For the new design solution, a dovetail form-blocked rotor structure, specific analyzing principles are also developed. The dovetail designs are shown to be good solutions with their lower leakage flux and at least the same strength against centrifugal forces as the conventional rotor solutions. The compared conventional solutions considered have inseparable rotor sheets in which the parts of the rotor are kept still by using bridges between them. In the dovetail rotor, the forms of the rotor parts keep them together and no bridges between them are needed for support. The simplicity of the dovetail solution has also been kept the same or better. In addition, the manufacturing method is the same for both solutions. The dovetail design can also be used for saving the magnetic material of permanent magnet synchronous machines because it has a smaller leakage flux than the conventional V-shaped designs with supporting bridges. The problem of how to compare the dovetail designs to the conventional ones is considered in depth. The strength of the dovetail structure has to be defined in a different way than in the conventional design with supporting bridges. In bridge-fixed design, the strength of the bridges is critical for rotor durability but in the dovetail design wider areas of the rotor affect the strength of the rotor. However, the basic electrical properties could be defined with the same method. Additional methods for defining the electrical properties of dovetail designs are also considered. One method is that the load angle can be defined only from the forms of phase currents in delta-connected synchronous machines and phase voltage and current in star-connected synchronous machines. The load angles defined are successfully used to find a good model for the test results. The other method is to view the normalized local torque density in the air gap as a function of time. In this work, several dovetail synchronous reluctance and permanent magnet machines are designed, manufactured, tested, and analyzed. The design, manufacturing, testing, and analysis methods are defined and developed especially for dovetail designs

Torque pulsations minimization in PM synchronous motor drive

Master'sMASTER OF ENGINEERIN