A constant power, load independent microwave source

Gerber, J. W. (Johann Wessel) (2002-12)

Thesis (MScEng)--University of Stellenbosch, 2002.

Thesis

ENGLISH ABSTRACT: In the past few years, a need for consulting on microwave heating has surfaced. Since most specialised microwave components are imported, this adds a hefty price tag in developing the infrastructure for such consultation. This thesis looks at the design oflow cost alternatives for use in the laboratory. A microwave source output with variable output power is often required for consultation. The calculation of product costs may also be simplified if the available microwave power is constant despite load changes. The magnetron as a load was first investigated and a high voltage SMPS was then designed to control the output of the magnetron according to operator / consulting requirements. To ensure adequate feedback of system output and load matching, a dual directional coupler has been designed and implemented. Since the amount of microwave power required has a direct impact on the initial capital expenditure, costs need to be kept low by optimising the system. An impedance matching unit was designed to match the magnetron with the load, saving energy and reducing system costs. Through automation, the system will strive for the optimum load condition without operator intervention.

AFRIKAANSE OPSOMMING: Die afgelope paar jaar het 'n behoefte ontstaan aan konsultasiewerk op die gebied van mikrogolfverhitting. Aangesien gespesialiseerde komponente meestal ingevoer word, bemoeilik die koste daarvan die ontwikkeling van die nodige infrastruktuur vir konsultasie. Hierdie tesis kyk na die ontwerp van goedkoper alternatiewe vir laboratoriumgebruik. 'n Mikrogolf bron met 'n verstelbare kraglewering is dikwels nodig tydens konsultasiewerk. Produk kosteberekinge kan ook vereenvoudig word indien die mikrogolf kraglewering konstant bly, ongeag produk veranderinge. Die magnetron as GS las is eers ondersoek waarna 'n hoogspanning geskakeldekragbron ontwerp is om die uittree van die magnetron te verstel volgens operateur- / konsultasievereistes. 'n Dubbele direksionele koppelaar is ontwerp en by die laboratorium opstelling gevoeg om voldoende terugvoer van die kraglewering en impedansie aanpassing te verseker. Die hoeveelheid mikrogolf drywing wat benodig word, het 'n direkte impak op die aanvanklike kapitale uitgawe vir die stelsel. 'n Optimale stelsel is dus noodsaaklik om kostes te bespaar. 'n Impedansie-aanpassingsnetwerk is ontwerp om die magnetron en las by mekaar aan te pas om sodoende energie en kostes te bespaar. Deur outomatisering streef die stelsel na optimale werkverrigting sonder enige ingryping deur die operateur.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/52626
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