Thesis MTech(Electrical Engineering))--Cape Peninsula University of Technology, 2006 / Reluctance Synchronous Machines (RSM) have, due to their rotor geometry, an inherently high torque ripple. This torque ripple is defined as the deviation of the minimum and maximum torque from the average value. It is unwanted as it indicates uneven pull on the rotor causing deformation of it and hence different air-gaps along the rotor circumference as well as acoustic noise. In applications such as power steering, robotics and radar positioning systems where high precision movement is vital, oscillating torque will lead to the malfunction of these devices and therefore suppressed the use and development of RSMs. Unlike the Induction machine (IM), the RSM has no copper losses in the rotor, which reduces the operating temperature significantly. With the development of electronic drives the quality of the output torque could be improved by means of accurate current- and flux space phasor control methods with much success and made the RSM a possible replacement for the IM. However, reducing torque ripple by means of purely geometrical changes is still a challenge to the machine designer. This thesis will focus on the reduction of torque ripple while leaving the average torque relatively unchanged by changing the rotor geometry. The rotor changes will take place by means of flux barriers and cut-outs while the stator has either semi-closed slots or magnetic wedges. In this work rotor structures with equal harmonic magnitudes but their angles 1800 apart. will be combined to form one machine and identify how torque harmonics respond. The change in average torque and power factor will be evaluated with all geometrical changes made to these machines throughout this work.

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This report describes the speed characteristic and various methods of speed control of DC shunt (separately excited) motors, especially for application in electrical vehicles. The basic behavior of the DC motor is discussed, along with traditional and modern techniques of speed control. As an example, a speed controller for a shunt motor (built and tested by the author) is discussed. Two types of speed controllers for electric cars are discussed, and the performance results for an experimental electric car are presented. Finally, a design for a 24 HP car motor controller using both armature and field control was simulated on a smaller scale in the laboratory.

In review, the author is struck with a feeling of the relative insignificance of his findings. Other sources of information seem to have a wealth of ideas, a scope far beyond the present investigation, and a variety of means to approach the subject. Upon further consideration, however, and a realization of the comparative expenditures of time, energy, and thought given to the subject, much familiarity has been gained with the general problem, with the factors involved, and their relative importance. Some interesting experiments have been watched, and the groundwork has been laid for more. In this light, the original purpose has been accomplished. / Master of Science

A microcomputer-based data acquisition and control system was designed for the diagnostic monitoring and control of high-speed electric motors. The system was utilized in high-speed bearing life-testing, using an electric motor as a test vehicle. Bearing vibration and outer race temperature were continuously monitored for each ball bearing in the motor. In addition, the stator winding and motor casing temperature were monitored. The monitoring system was successful in detecting an unbalance in the rotor caused by the loss of a small piece of balancing putty. The motor was shut down before any further damage occurred. In a separate test, excessive clearance between a bearing outer race and the motor caused high vibration readings. The motor was monitored until the condition began to deteriorate and the bearing outer race began to spin significantly. Again, the monitoring system powered down the motor before any significant damage occurred. The speed of the motor tested is controlled by a PWM (pulse width modulation) technique. The resulting voltage and current waveforms are asymmetrical and contain high frequency components. Special circuitry was designed and constructed to interface sensors for measuring the voltage and current inputs to a spectrum analyzer. Using frequency and order analysis techniques, the real and reactive power inputs to the three·phase motor were measured. / Master of Science

It can definitely be stated that the results of the experiments show that almost no appreciable adverse effects on the test motor result from six phase rectifier operation, The efficiency was unaffected by rectifier operation, The temperature rise with rectifier operation was roughly within 5°C of that obtained with DC generator input, The commutation was not adversely affected when using the rectifier, These statements apply even when the rectifier is operated at half voltage, a condition giving very much more ripple than the full voltage ripple. / Master of Science

Call number: LD2668 .T4 1960 C42

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

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