Modification of Cockcroft–Walton-Based High-Voltage Multipliers with 220 V and 50 Hz Input for Non-Thermal Food Processing Apparatus

Anurak Jaiwanglok,Krit Smerpitak,Amphawan Julsereewong,Kei Eguchi

doi:10.3390/su12166330

Abstract

A design of high-voltage multipliers to generate underwater shockwaves is one of the most important factors for successfully providing non-thermal food processing in a cost-effective manner. To be capable of fully utilizing the Cockcroft–Walton-based high-voltage multipliers for underwater shockwave generation, this paper presents a topological modification of three interesting design approaches in bipolar structure for 220 V and 50 Hz AC input to generate more than 3.5 kV DC output within short time periods. In addition to Cockcroft–Walton multipliers (CWMs), the first modified scheme employs a positive full-wave rectifier (FWR) and positive voltage multiplier block (VMB), the second modified scheme employs positive/negative half-wave rectifiers (HWRs), and the last modified scheme employs a switched-capacitor AC-AC converter. To comparatively analyze their performances, the digitally controlled operations of the modified realization schemes as well as their electrical characteristic estimation based on a four-terminal equivalent model are described in detail. The effectiveness of three modified circuit configurations and the correctness of the given theoretical analysis are verified through SPICE (Simulation Program with Integrated Circuit Emphasis) simulation results. The formulas achieved from theoretical estimation are particularly useful when designing the proposed high-voltage multipliers (HVMs) because good agreement between the theoretical and simulation results can be achieved.

Highlights

It is widely accepted that underwater shockwaves produced by high electric discharge can be effectively used for non-thermal food processing with minimal impact on nutritional properties and at low costs because several benefits, such as short processing time and low energy consumption, can be achieved [1,2,3,4,5]
The goal of this paper is to propose a topological modification of three interesting design techniques for realizing bipolar high-voltage multipliers (HVMs) with 220 V and 50 Hz input to produce the DC output between 3.5 and 4.0 kV, which is suitable to generate underwater shockwaves for non-thermal food processing apparatus
To demonstrate the effectiveness of three proposed HVMs as well as the correctness of the given theoretical analysis, the modified schemes of Figure 1a–c were simulated with the SPICE program

Summary

Introduction

It is widely accepted that underwater shockwaves produced by high electric discharge can be effectively used for non-thermal food processing with minimal impact on nutritional properties and at low costs because several benefits, such as short processing time and low energy consumption, can be achieved [1,2,3,4,5]. A typical non-thermal food processing system using underwater shockwaves consists of a high-voltage generator, big capacitor, high-voltage switch, and pressure vessel [10,12]. The big capacitor acts as a discharging circuit to produce a spark between two electrodes, which are placed in water stored inside the pressure vessel. The high-voltage switch is employed to control the charging/discharging status by connecting/disconnecting the big capacitor to/from the HVM. The output voltage of the HVM is charged to the big capacitor when turning off the high-voltage switch. In the case of turning on the high-voltage switch, the electric charge stored in the big capacitor is discharged from two electrodes to generate the shockwave in the pressure vessel. The target food is processed by the mechanism of spall fracture [6] or spalling destruction [13]

Objectives

Results

Conclusion