Power Control of a Domestic Microwave Oven

Microwave ovens are widely used for research purposes, many times incorrectly. Understanding how the microwave power is controlled will give the researcher insight into the experimental results obtained. Microwave power resolution and system time response are the main figures of merit for evaluating the quality of a microwave power controller. A 700 Watt domestic microwave oven was modified using a TRIAC to control the magnetron input power. The resulting microwave output power measurements were used to evaluate the initial system. Further modifications were made with the intention to improve the identified figures of merit. Combining desired characteristics from existing magnetron power control strategies allowed the design of a custom power controller suited for rooibos tea sterilization. The system shows improvement in response time and power resolution, while transformer losses are also taken into account. This paper will focus on the hardware changes made and the motivation behind the changes. Therefore, illustrating how a domestic microwave oven can be modified to suit various research applications.