Pulsed Electric Field treatment of packaged food

Food manufacturers are looking for new preservation techniques that don’t influence the fresh-like characteristics of products. Non-thermal pasteurisation of food with Pulsed Electric Fields (often referred to as PEF) is an emerging technology, where the change of the food is less than with thermal pasteurisation. With this method, pasteurisation is realised by electroporation of bacterial membranes, which prolong the shelf-life of the product. Existing PEF treatment is based on the application of the electric field prior to packaging. To avoid re-contamination of the product during packaging, it is packed aseptically (i.e. sterile). The goal of this research is to determine whether it is technologically possible to generate enough electric field in already packaged food products. This will make aseptic packaging machines superfluous. During this research it has been proved that it is possible to generate sufficient electric field in already packaged products and to reduce the initial amount of bacteria with 99.9999%. For the realisation of this technique, which is called PEF in-pack, an electrically-conductive plastic packaging material is used. To reduce the required electrical power during treatment, the technique can only applied on relatively small deformable packages up to 200 ml. To show how this technique can be introduced into existing food production lines, product cases have been worked out. Portion packs for liquid food and pharmaceuticals, for example, are possible product applications.ESEElectrical Engineering, Mathematics and Computer Scienc

Auto-resonant Control of the H-Bridge Resonant Converter for Inductive Power Transfer Applications

In inductive power transfer applications that use resonant compensation networks, the commonly employed H-bridge inverter should be kept operating in soft-switching to ensure high power efficiency and low irradiated electromagnetic noise. To achieve so, the zero-crossing detection circuit for the resonant current or voltage must be fast and accurate in any operating condition. This paper researches the concept of an auto-resonant control for the typical H-bridge resonant converter used in wireless charging systems. In the method proposed here, the reference levels for the zero-crossing detection of the inverter's current are automatically adapted depending on the slope of the current itself at the zero-crossing. In this way, it is possible to compensate for the circuit delay even in the presence of parameters' variation and to ensure that the soft-switching is always maintained. The functionality of this control method is proven first mathematically, and then with circuit simulations. The core steps for the implementation are described with the support of functional blocks. Finally, the system start-up strategy is explained, which uses an auxiliary timed oscillator to modulate the inverter with a fixed 50% duty cycle at a higher frequency than the nominal. This guarantees that the start-up is in the inductive region and, thus, the zero-voltage switching turn-on. Once the detection circuits sense the current flow, the oscillator is automatically disabled, and the nominal power transfer starts.Virtual/online event due to COVID-19DC systems, Energy conversion & Storag

Combined ZVS-ZCS topology for high-current direct current hybrid switches: Design aspects and first measurements

Electrical Engineering, Mathematics and Computer Scienc