A new behavioural model for performance evaluation of common mode chokes

A galvanically isolated three-phase AC/AC converter with a high-frequency AC-link has been analyzed from an EMC point of view. This is a special configuration because of a large number of switches, a high frequency transformer, and a fourwire output. The essential coupling paths are identified. Corresponding suppression remedies are given. The results, before and after measures, have been presented to demonstrate the improvement in EMC. Keywords: AC/AC converter; electromagnetic interference; galvanically isolate

Shielding Effectiveness Measurements using a Reverberation Chamber

Shielding effectiveness measurements have been performed using a reverberation chamber. The reverberation chamber methodology as we1l as the measurement setup is described and some results are given. Samples include glass reinforced plastic panels, aluminum panels with many holes, wire mesh, among others. The reverberation chamber setup gives very repeatable measurement results

Immersed Tunnels in Subarctic Conditions

The thesis aims to find the changes in design and execution to immersed tunnels in subarctic regions. The Orlovsky Tunnel in St. Petersburg serves as a case study. The Orlovsky tunnel is a 1600 m tunnel in a rapid flowing river. the ice regime of the Neva River is characterized by frazil ice, which causes hanging ice jams and anchor ice. Together with changes in the flow velocity profile in the frozen period, a more robust tunnel protection is required. Thermal expansion of ice, drift ice, and drag on an ice cover require a sloped embankment to reduce shear, which in turn increases the surcharge on the tunnel. Rubber gaskets such as the Gina and Omega profiles are researches and suggestions are given for rubber composition, and its effect on fatigue, watertightness, strength, and transport requirements. Thermal loading of the tunnel was also analyzed. It was concluded that the plastic hinge capacity of the corners was sufficient to resist the temperature differential in the outer sections of the tunnel. Cracking of the inner walls require extra horizontal reinforcement. Large temperature fluctuations may require alternate types of expansion joints or smaller tunnel elements. A probabilistic planning was finally performed to quantify the risk of non-completion in a single ice-free construction period. For this a Monte Carlo simulation was utilized. This had implication on the number of tunnel elements, foundation, the construction dock location, and so forth. Emergency measures, such as a frazil collector and ice boom are recommended in the case of early frost.Hydraulic StructuresHydraulic EngineeringCivil Engineering and Geoscience

Ethernet susceptibility to electric fast transients

The effect of Electric Fast Transients (EFT) phenomena in an Ethernet interface set-up is investigated in order to get more insight in coupling and interference mechanisms, robustness and susceptibility levels of a typical Ethernet installation on board of a naval vessel. It is shown that already a small EFT pulse is capable of disturbing or disrupting Ethernet communication at protocol level, which makes this not just a matter of signal integrity. It seems that the protocol is not designed to handle EFT phenomena in an efficient way. We focused on the quality of the interface, i.e. cables, connectors and feed-thoughs. While affordable high quality cable is readily available, it is more difficult to find low cost and robust connectors without a large variability in performance for EMC, but to decouple data handling electronics from disturbing transients is of paramount importance for interference free data communication. As expected, screened cables help to mitigate the interference, but only when the screens are properly connected on both sides

Effectiveness of cable transits, and how it is easily void

Large installations use different shielded, or EMC, zones to separate regions, such as in the integrated mast onboard naval vessels. Multiple cable transits are being used as a standard decoupling measure between the zones. Cables shields are connected in the cable transits with the objective to shortcircuit cable sheath currents to the wall. Measurements have been performed to check the quality of the installation. The test procedure and some measurement results are described. It is shown that the effectiveness of a cable transit can be completely nullified if a single cable is not treated properly

Immersed tunnel design in subarctic rivers

The demand for tunnels crossing waterways in urban areas is expanding into colder regions, with immersed tunnels an increasingly competitive alternative for waterway crossings. Recent examples of new immersed tunnels affected by cold weather include the Bjørvika, Söderstrum, and Marieholm tunnels in Norway and Sweden. This article aims to describe the practical and technical issues related to applying the immersed tunnel construction method to colder regions for them to stay competitive.An initial distinction can be made between tunnels crossing large water bodies and tunnels crossing rivers based on the differences in their ice regimes. For example, one of the main ice related issues for immersed tunnels crossing seas and lakes is ice pile-up, which results in heavy loading of the approaches and mechanical scour of the seabed. This is an issue which is relatively well documented and has been taken into account in projects like the Øresund tunnel. The ice regime of a river is quite different, where issues for immersed tunnels have thus far gone undocumented. Subarctic issues typical in river ice regimes may include ice jams, anchor ice, surges, water level drops, and thermal expansion of ice, as well as unfavorable material behavior.Hydraulic Structures and Flood Ris

Design of complex naval installations and the limitations of equipment standards

This paper focuses on cost effective integration of commercially available equipment and infrastructure into a military maritime environment assuring performance, robustness, safety and continuity. The rationale behind settled standards is put in todays perspective and an assessment of the possible EM interactions of equipment in a military environment is made. It is shown that the strict use of military equipment standards is a pitfall in procurement that makes naval shipbuilding unnecessarily expensive and might give a false presumption of low risk for EMC. Some investigated aspects of the effects of a military naval environment on civil COTS equipment show that a careful design with properly engineered mitigation measures can be an alternative for the hardening and compliance requiring for all integrated equipment

Estimation of the probability distributions for cable coupling using unscented transforms

This work presents the use of unscented transforms (UT) for the description of statistical uncertainty in electromagnetic coupling between cables. UT greatly reduce the computational burden for the statistical analysis of nonlinear problems compared with more traditional approaches such as the Monte Carlo technique. Coupling between cables has a nonlinear parameter dependence and has a high variability due to the variability in the cable braid manufacture and the highly variable nature of cable layout. Therefore, cable coupling can only be defined within statistical limits. First, it is shown that by analyzing the resonances the important features of maximum coupling and the point of maximum coupling can be characterized. It is then demonstrated how UT can be used to efficiently identify the parameters which contribute significantly to the uncertainty in cable coupling and then to provide a measure of the probability distribution for the multivariate problem

Cable crosstalk and separation rules in complex installations

Cable separation rules to prevent crosstalk between different cable categories are in use for over five decades. The rules have been developed in the analogue era and when equipment was not fulfilling any, or maybe some, electromagnetic interference standard. This has changed but the rules are still in use. The technical rationale is unknown, so simulations and measurements have been performed to understand and interpret crosstalk between various cables, to develop ingredients for a general model that includes sources, coupling and victims. The goal is to eventually find ways to simplify, harmonise and improve these rules