| Traditional thermal sterilization technology is easy to realize,high safety,and widely used in industry,but in the process of thermal sterilization will destroy food nutrition and change the original flavor of food itself.With the improvement of people’s material level,people have higher requirements for food nutrition and flavor on the basis of food safety.High voltage pulsed electric field sterilization technology is a non-thermal sterilization technology,because of its short sterilization time,high efficiency,small collateral damage to food and other advantages,has been widely concerned,has a huge market value.However,there are great differences in the structure of different kinds of microorganisms,and it is difficult to determine the load under the action of pulsed electric field.At present,the output waveform of the high-power high-voltage pulse power supply used in the laboratory is mostly exponential attenuation wave.Even if the high-voltage pulse power supply can transmit square wave,the pulse voltage is difficult to drop rapidly under capacitive load,and the normal output of square wave will affect the sterilization effect.In order to meet the requirements of different sterilization experiments,this paper developed a high power high voltage pulse power supply with adjustable voltage amplitude,frequency and pulse width,which can normally transmit square wave under various loads,and carried out sterilization experiments on bovine colostrum.This paper first summarizes the development and research status of high voltage pulse electric field sterilization,expounds the factors affecting the effect of pulse electric field sterilization,analyzes the types of common pulse power supply,summarizes its advantages and disadvantages,and determines the design of pulse power supply based on Marx circuit structure.Based on the analysis of the discharge characteristics and performance of Marx circuit,a half-bridge Marx circuit is proposed to improve the classical Marx circuit and take it as the main circuit of the pulse source.Through the comparison of the commonly used solid-state switches,combined with the needs of this paper to choose IGBT as a switching device.According to the needs of the pulse sterilization experiment,the performance index of the pulse source is proposed,and the parameters of the components in the circuit are calculated and selected.The main circuit structure is simulated and analyzed,and the output parameters and multi-load adaptability are verified.The driving circuit,isolation circuit and control circuit are designed.The pulse power supply can output square wave pulses with amplitude of 0～10k V,pulse width of0～20μs and pulse frequency of 0～1k Hz.The maximum output current can reach800 A,and it has good over current protection function and multi-load adaptability,which can meet the requirements of different pulse sterilization experiments.The effect of electric field intensity,pulse repetition frequency and pulse width on sterilization of colostrum was analyzed.The results show that increasing electric field intensity,pulse frequency and pulse width can enhance the sterilization effect,but electric field intensity has a more significant effect on the sterilization effect. |
