Microwave power control strategies on the drying process I. Development and evaluation of new microwave drying system Original Research Article

A phase-controlled electrical power regulator was developed and connected in series with the original cycle-controlled power regulator of an existing domestic microwave oven. The microwave oven was further modified such that combined microwave and convectional drying can be accommodated. The system performance was evaluated which included calibration of the maximum microwave output power, determination of the microwave distribution in the cavity, establishment of the relations between the output power and the input voltage for the phase-controlled power regulator. It was observed that phase-controlled power regulator could be successfully used for quasi-continuous (fast-switching) power regulation with the maximization of power efficiency. The degradation of output microwave power was recorded and the non-uniform distribution of microwave field in the cavity was also verified.