摘要
Abstract
Pulsed electric fields(PEF)sterilization technology has the advantages of low energy consumption,short sterilization time,high efficiency,and low processing temperature.The high-voltage pulsed electric field acts on the biofilm of the cell to form a transmembrane voltage.When the trans-mode voltage exceeds a certain critical value,cells rupture and ultimately die completely.The sterilization technology has a small temperature rise and can maximize the retention of food nutrition and flavor taste.This non-thermal sterilization technology has received extensive attention.At present,the bipolar pulse power supply solves the tailing phenomenon in the sterilization of liquid food by means of discharge circuit and controlling the conduction time of solid state switch,but the tailing phenomenon still exists,which will cause the temperature of the treated liquid to rise,damage food nutrition,affect taste,and lead to the abnormal discharge of the treated liquid.
A new topology structure based on Marx circuit is proposed.This topology reduces the number of semiconductor switches used.A discharge circuit for residual charges of diverse loads is designed.The working process of the new topology circuit is introduced in detail.Combined with the control of the conduction sequence of the semiconductor switch in the bipolar pulse circuit,the output of the bipolar square wave pulse is realized.The feasibility analysis of the three-stage bipolar square wave pulse circuit is carried out by using OrCAD simulation software.It is verified by simulation that the output waveform of the power supply is still a square wave under the resistance-capacitance load,which realizes the steepening of the bipolar square wave pulse waveform.At the same time,it is verified that the circuit has clamping function.The experimental prototype of a three-stage bipolar square wave pulse power supply is designed and built.The performance index of the pulse power supply prototype and the selection of the main components are given.The solid-state switch uses ABB's 5SNE0800E330100 module containing an anti-parallel diode and a separate diode module.The module can make the power supply structure more compact,reduce the inductance component of the circuit,and improve the rising edge of the bipolar square wave pulse.The test results show that the bipolar pulse power supply achieves a high-voltage pulse output of±6 kV and 50～500 Hz.The output pulse width is 2～20 μs.The rising edge and falling edge of the positive and negative pulses are within 300 ns.By designing a circuit to discharge the load in a timely manner,the pulse tail is significantly steepened,and it has good load adaptability.
A bipolar square wave pulse power supply sterilization experimental platform was established.The high voltage pulse sterilization system platform is mainly composed of bipolar square wave pulse power supply,liquid device to be treated,water pump,degassing treatment room,sterilization treatment room,liquid device after treatment,temperature control device and measuring device.Taking the bacteria naturally existing in raw egg white as an example,the sterilization experiment was carried out to study the sterilization effect under different amplitude,frequency and pulse width of high voltage pulse power supply output.The results show that increasing the voltage amplitude,frequency and width of bipolar square wave pulse output can enhance the sterilization effect of liquid food,and the increase of pulse voltage amplitude can improve the sterilization effect more significantly.However,the increase of pulse voltage amplitude,frequency and pulse width will lead to the temperature rise of liquid food and lead to abnormal discharge.Therefore,it is necessary to adjust three parameters reasonably to control the temperature rise of liquid food in order to achieve better sterilization effect.关键词
高压脉冲电场/脉冲灭菌/双极性方波/Marx电路Key words
High voltage pulse electric field/pulse sterilization/bipolar square wave/Marx circuit分类
信息技术与安全科学
