Development and evaluation of multi-stage phase-controlled converter for magnetron driver

As clean and high energy efficient, the microwave drying system has gained popularity for a wide variety of food preservation and processing of bio-commodities. The main advantage is the acceleration of the drying process which is quite limited comparing to conventional hot air drying system. However, during microwave drying process, pressure and temperature will increase continuously and this might cause undesired side effects such as degradation and physical damages. In order to eliminate the mentioned problems and enhance higher performance of control system flexibility, in this paper, a design of multi-stage phase-controlled converter for microwave drying system is proposed. The objective of this multi-stage power control is to track the drying characteristics under microwave drying process at different power level depending on the stage of drying cycle period. This control approach is achieved by controlling the triggering events at appropriate phase angle of TRIAC based on predefined power profiles. By varying the pulse width, the average power output of the magnetron can be controlled. As the focus of this paper, the hardware design and component selections are discussed. The system flowchart and control algorithm based on microcontroller Arduino Mega 2560 are also presented in details. Experimental results of the proposed multi-stage phased-control converter are investigated and discussed.