This thesis discusses a principle of continuous speed regulation of AC motors, which is based on frequency conversion, and describes an experimental three-phase converter built for speed test purposes. The converter accepts power from a three-phase 60 cps. source and control signals from an auxiliary three-phase square-wave generator whose fundamental output frequency can be varied between 70 and 570 cps. When the two three-phase inputs are of opposite sequence, fundamental output frequency can be varied between 10 and 510 cps. The converter is of the static switching type. It consists of three identical units, one in each phase. Each unit has four power transistors which are operated in the on-off mode. Control signals are fed to the base-emitter circuits through isolating transformers. A free-running multivibrator in the control unit determines the period of the square-wave signals. The signals are taken from three bistable circuits, triggered in proper sequence through a system of gates. Output voltages from the converter have a relatively high harmonic content. Higher harmonic currents forming zero-sequence systems can be suppressed entirely. Current harmonics of positive and negative sequences must in general be tolerated. A discussion is given on the performance of AC motors when powered by this type of converter. No-load speed tests on small induction motors confirm the, principle on which the experimental work has been based. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

With modern naval vessels headed in the direction of integrated power systems, new attention must be paid to efficiency of both power and space. However, modern designs for ship power systems often incorporate DC link converters, or synchroconverters, into their design. Not only does this add extra steps into the power conversion process, it also adds the DC link, which requires large capacitors and can aggravate problems experienced in a short circuit. Modern research for cycloconverters is showing that they have many advantages over the synchroconverter when used in a ship power system. However, cycloconverters also have downsides. One of these problems is the incorporation of harmonics into the supply current, distorting the generator output, as well as voltage harmonics at the output of the converter, which can cause problems at the various loads. Most disastrous of all, additions of subharmonics, or interharmonics which occur below the fundamental can appear. Subharmonics are nearly unfilterable and they can cause serious problems for any power system. This study specifically considers higher frequency inputs to see if these subharmonics can be mitigated in a cycloconverter system. / US Navy (USN) author.

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Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

M.Phil. (Electrical and Electronic Engineering) / There are two methods that can be used when power is converted from one frequency to another. One way uses a DC link as an intermediate stage and the other uses no intermediate stage. When no DC link exists, the conversion process is referred to as AC-AC conversion, (Cha, Enjeti & Ratanapanachote, 2004:2237). This method essentially chops the AC signal in a specific manner which yields an AC signal with a different frequency directly. Depending on how the AC signal is chopped, it would result in a varied number of wave shapes are constructed. The construction of these various wave shapes results in devices that can accomplish different tasks. One such device is called a unity displacement factor frequency converter (UDFFC). This research attempts to develop a model, to simulate and design a unity displacement factor frequency converter. The primary idea about this device is that the power factor or displacement factor is unity regardless of the load. There are three parts in the development of the UDFFC. The power circuit is an array or matrix of switches that link the three phase supply to the three phase load. The power circuit is interfaced to the control circuit which generates pulses that control the matrix of switches. The control circuit utilizes embedded control software that performs the control logic in a microcontroller. The development of the UDFFC has a potential to solve real power engineering problems, such as eliminating the DC link in a converter. This achieves the conversion of AC directly to AC in the absence of a DC link. The other major advantage is the variation of the output frequency to a desired value. The most important is that the displacement factor can be controlled as well.

M.Ing. / Photovoltaic (PV) systems are considered as renewable resources of energy that are utilized in the conversion of direct and diffuse solar radiation to electric power. These systems are considered as environmentally friendly energy resources as they reduce pollution. These systems’ produced power depends on the radiation of the sun as well as the temperature, the impedance of the load, and the unfitted parameters in PV systems. In this field, the PV systems and DC-DC converters will be explored in both configuration (the open loop and closed loop systems), whilst their implementation will be designed as a closed loop system. The success of the system depends on the algorithm of the maximum power point tracking that catches the maximum sunshine radiation amount to generate the maximum electrical power. This system simulation and hardware implementation will be done through the Proteus program and real components integration ...

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Thesis (M.A.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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