Efficiency Optimization for Phase Controlled Multi-source Microwave Oven

A solid-state microwave generators system is considered as an alternative to the magnetron, in order to inject electromagnetic energy into the cavity of a microwave oven for domestic use. Over current devices, the use of solid state technology allows to control the frequency and phase of the electromagnetic field generated. Considering a simplified cavity with 2 solid state sources, the influence of the electrical parameters on the maximum efficiency obtainable in the process of microwave heating is investigated. By varying the frequency, different values of optimal phases and different values of maximum efficiency are obtainable. Moreover, the procedure is repeated varying the position of one source port and the influence of geometry on the system is evaluated. The results demonstrate that the ability to control the electrical quantities of a microwave heating process, makes it possible to obtain better results in terms of energy efficiency over the current poorly controllable systems. INTRODUCTION Nowadays microwave ovens for household use and industrial installations at 2.45GHz frequency band use magnetrons as a high power sources of microwave energy. Those bulky and old-fashioned devices are characterized by a limited efficiency of energy conversion from power supply to microwaves. They are also difficult to control, which leads to mismatch losses due to significant changes in reflection characteristics of the resonant cavity caused by large variations of load parameters (permittivity, loss tangent) as a function of its temperature. New semiconductor technologies allow us for building innovative high power microwave sources. They exhibit great advantages over magnetrons like a precise frequency, phase and output power level control ability. The microwave field can easily be manipulated within an empty oven cavity using phased array control techniques, but when food is introduced in the cavity, the situation becomes complex due to many variables related to the load (position, type, weight, shape, dielectric constant). The main goal of the work is to investigate on the control of phase shift and frequency, in order to introduce important innovations with regards to the energy transfer during a microwave heating process for household applications. Afterwards, the influence of the mutual waveguide position has been investigated: a matrix of simulations has been carried out to assess if there are any particularly promising solutions with regard to the optimal transfer of energy from the source to the load. A fixed load position has been assumed, without turntable