Design Of Electromagnetic Pulse Simulator And Its Sterilization Effect Of Rhizoctorzia Solani

In recent years, the interdisciplinary subject of high power impulse technology in the agricultural bio-engineering have attracted much attention. Basing on reserved capacitance EMP generator, the high-voltage EMP simulator system was established combining of high-voltage technology with power impulse technology. According to related studies at home and abroad in present, the work characteristics of EMP simulator system was systematically researched using the methods of theoretical analysis combining with experiments, and influential factors and influential laws on the output pulse have been analyzed in detail, design schemes of the EMP simulator system was proved correctly and feasibly. The EMP sterilization of Rhizoctorzia solani was also researched. The completed work and achieved results are generalized as follows:1. The basic theory of the double exponential pulse’s generation, translation and measurement was analysed. Conclusions were give basing on the discussion of the discharge mechanism and process of gas spark switch:discharge stability was better as electric field of the switch was uniform; the discharge delay and dispersion of breakdown voltage of gas spark switch was smaller under continuous voltage compared to impulse voltage; Gas type, density, humidity and atmospheric pressure all had an effect on the discharge characteristic. Structure and transmission characteristics of the TEM cell were analysed and laws of higher-order modes was given. Performance of the resistive voltage divider was analysed and some improvements were recommended. Sources of error in the measurement process were analysed and the corresponding solutions were proposed.2. The high-voltage DC source based on phase-shifted ZVS full-bridge DC/DC converter for experiments was also designed in this paper aiming at the limitation of the traditional power which were large size, low-fidelity and poor stability. The main circuit was composed by input rectifier filter circuit, full-bridge DC/DC converter circuit, high-frequency transformer and the times rectifier circuit; A digital control system containing was designed in which a DSP IC (TMS320F2812) was used as the core. Output of the DC source could reach 30 kV and 2 mA.3. A switch discharge simulation method using nonlinear switch-lap resistor basing on Matlab/Simulink instead of linear or fixed value one was put forward, aiming at the limitation of the former simulation methods, which often cause big errors. A simulating model using Simulink was established. Using this model, simulations with different load, switch inductance and switch capacitance were done to get their time domain discharge characteristics. Simulation result showed that rise time of the output pulse was determined by system inductance when fall time was determined by system capacitance which was in accordance with the theory.4. The work characteristics of EMP source were studied. Its static characteristics were measured by the measurement system composed of resistor divider and oscilloscope. The working voltage and output pulse’s stabilization of the EMP source under different pressure were studied and analyzed. The research results showed that the pulse source static voltage varied with the pressure increased linearly, while the output pulse amplitude increased; Rise time and amplitude stability of the output pulse under high pressure increased was better; Fall time of the output pulse increased 10 ns when an energy storage capacitor added 100 pF. hi the same way, trigger characteristics of the EMP source were measured, recorded and analyzed. The research results showed that a negative pulse triggered more widely than a positive pulse under the same conditions; Rise time of the output pulse triggered by a negative pulse was shorter than a positive pulse.5. Calculations of TEM Cell section impedances were done basing on finite element method and the specific structure of TEM Cell was designed. Simulation and analysis of the TEM cell properties were done using finite integration theory, the simulation results showed that its electric field distributed uniformly and its impedance matched with transmission cable well. A TEM cell sample was made combining the simulation results and its impedance and withstand voltage were tested. Test results showed that its highest withstand voltage was 25 kV and its standing-wave ratio kept within 1.5 which met the experiment desire.6. The EMP pasteurization on Rhizoctorzia solani was experimented and the principle of EMP pasteurization was discussed. In high-voltage pulse electric field, Rhizoctorzia solani cell membranes were disrupted, reunion and wastage caused the cell death. The experiments showed that EMP pasteurization effect could be enhanced by extending the work time when the pulse amplitude was less than a critical value; when the amplitude was greater than the critical value, the main influence factor of EMP pasteurization was the EMP amplitude while it was not very meaningful to extend the work time.Through the research in this project, the theory system of EMP simulation will be further improved, which will provide theoretical basis and technical support for design. This research has important theoretical significance and practical value to improve the EMP simulator performance and promote the application in civil fields.