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Abstract
Top electrode voltage of a radio frequency (RF) heating system is an important parameter to accurately determine final sample temperatures using computer simulation. The purpose of this study was to establish the correlation between the top electrode voltage obtained by analytical method or simulation and the measured electrical currents. A measuring circuit was designed and developed to directly measure the top electrode voltage in the 27 MHz 6 kW RF unit together with the anode current read from the RF generator. The top electrode voltage was experimentally determined with 3 kg soybeans under five electrode gaps using computer simulation based on the matched temperature profiles in three layers, and analytical methods based on the heating rates measured by infrared camera, fiber optic sensors and thermocouples. Results showed that the electrode voltage decreased with increasing electrode gap or decreasing heating rate. The correlation between the electrode voltage estimated by temperature distributions from three-layer thermal imaging and the electrical currents both from the anode reading and direct measurement was the best one among the estimation methods and could be used for future computer simulations.
Acknowledgements
This study was conducted in College of Mechanical and Electronic Engineering, Northwest A&F University. This research was supported by research grants from PhD Programs Foundation of Ministry of Education of China (20120204110022) and General Program of National Natural Science Foundation in China (No. 31371853). We thank Rongjun Yan, Long Chen, Kun Wang, Bo Ling, Rui Li and Lixia Hou for their helps on data collections and suggestions to improve measurements.