Evaluation of the magnetization direction effects on ferrite PM brushless fractional machines

Permanent magnets are frequently adopted in small brushless machines for automotive applications. Normally anisotropic ferrites, but some research on bonded magnets is being carried on. Several types of magnetization can be proposed, involving different levels of complexity in the magnetization process. In the paper a comparison between parallel and radial magnetization is described, taking into account on one side the major complexity of the radial process and on the other the small power derating of the paralle

PM fractional machines adopting bonded magnets: effect of different magnetizations on the energetic performance

The adoption of Permanent Magnets in small brushless machines for automotive applications is becoming frequent. Some research on bonded magnets is being carried on to substitute the ferrites. In the paper the parallel and radial magnetizations are considered: the different process complexity levels are analyzed and the effects on the iron losses and the energetic performances are evaluated by means of a simulation analysis and its experimental validatio

Energy-efficient motors

The use of a copper-squirrel cage in induction motors has been analyzed testing a prototype rated 1.1 kW and comparing the performances with a twin machine with an aluminum cage. The comparison has been made using torque, efficiency, starting torque, and starting current. For the considered machine size, the obtained results show that the simple substitution of the aluminum with copper can improve the efficiency of no more than 1.5% at rated load. Taking into account the copper market cost trend, the use of copper cage increases the break-even time due to the higher cost of copper rotor respect to the aluminum one. For this reason, the discussion about the use of copper cage can be still considered ope

BONDING OF CERAMICS: AN ANALYSIS OF THE TORSION HOURGLASS SPECIMEN

There is a recent and growing interest in joining ceramic parts due to their increased use in several fields such as next-generation nuclear plants, aeronautic engine parts and aerospace components. For high temperature applications, glass-ceramics are used as an “adhesive” for ceramic parts, this generates the need for test methods suitable to assess their bond strength. Unfortunately, the various test procedures currently used lead to different results. One recent test is based on torsion of hourglass shaped joined ceramics, originated from a modification of the ASTM F734-95 standard, with the aim of obtaining failure under a pure shear state in the bondline subjected to torsion. However, results obtained from different versions of the hourglass geometry show differences which are still difficult to compare. Moreover, due to the brittle nature of the materials and especially when the adhesive strength is comparable to that of the substrates, the failure is not confined in the bond and propagates also in the substrates. In this case, the results are still of arguable application for design purposes. The aim of this paper is to give an insight on torsion of hourglass-shaped joined ceramics and on the interpretation of the obtained results, by means of detailed analytical and numerical studies of the stress distribution in the specimen, and taking into account the brittle nature of the materials. The main findings are: i) the stress state in the bondline is not singular; ii) a non negligible stress concentration arises out of the bondline

Impact-based flash-flood forecasting system: Sensitivity to high resolution numerical weather prediction systems and soil moisture

In recent years, continuous improvements have been made in weather forecasting and flood prediction with great benefit from Early Warning Systems (EWSs). Despite the continuous quest for innovation from the scientific and user communities, EWSs remain based mostly on hazard forecast, and the information on possible consequences and potential impacts is generally missing. In this work, a methodology for quantitative real-time impact assessment for flash floods is presented. The methodology uses a multi-model ensemble approach and considers soil moisture uncertainty. Moreover, the flood forecasting chain, which normally provides only the discharge probability of exceeding a given threshold, is extended to include a fully 2D hydraulic model and a damage estimation model to quantitatively assess impacts in terms of economic losses and the people involved. The procedure was tested on recent flood events occurring in Genoa in northwestern Italy. This paper discusses the potential challenges and opportunities offered by this approach in the decision-making workflow in an operational context

Quantitative Flood Forecasting on Small- and Medium-Sized Basins: A Probabilistic Approach for Operational Purposes

Abstract The forecast of rainfall-driven floods is one of the main themes of analysis in hydrometeorology and a critical issue for civil protection systems. This work describes a complete hydrometeorological forecast system for small- and medium-sized basins and has been designed for operational applications. In this case, because of the size of the target catchments and to properly account for uncertainty sources in the prediction chain, the authors apply a probabilistic framework. This approach allows for delivering a prediction of streamflow that is valuable for decision makers and that uses as input quantitative precipitation forecasts (QPF) issued by a regional center that is in charge of hydrometeorological predictions in the Liguria region of Italy. This kind of forecast is derived from different meteorological models and from the experience of meteorologists. Single-catchment and multicatchment approaches have been operationally implemented and studied. The hydrometeorological forecasting chain has been applied to a series of case studies with encouraging results. The implemented system makes effective use of the quantitative information content of rainfall forecasts issued by expert meteorologists for flood-alert purposes

Effect of the Insulating Layer on the Properties of SMC Inductors

In inductor applications, different soft magnetic materials are used depending on the frequency range. Owing to powder metallurgy technology and to the increase in the implementation of innovative multifunctional materials, it is possible to find an alternative to the traditional magnetic materials of the inductance application sector. This study concerns a deep analysis related to soft magnetic composite materials. The insulating layer's effect is investigated to explore the applicability of such materials to the inductor sector. Four coatings systems are selected and two types of samples are prepared in the shape of a toroid and a rod, which are tested in different operating conditions. The rod inductors are also compared with a traditional one, based on soft ferrite materials. This work aims to integrate data coming from different measuring devices: the useful small-signal measurements of an RLC meter are completed by large-cycle data measured through a hysteresigraph. Different parameters are considered for the investigation: magnetic permeability (maximum and initial), iron losses at different induction peak values, and inductor quality factor are the most important. The obtained results prove that each analysis type is not fully reliable without the other in determining the coatings' effects on the SMC inductors' performance. In the end, it is demonstrated that SMC inductances can be successfully applied in a particular frequency range

The role of media in community resilience: Hindsight bias in media narratives after the 2014 Genoa flood

Aim: A massive flood due to exceptional rainfalls devastated the town of Genoa on 9 October2014. Media reports focused on the disaster, its causes and the political accountabilities. Reading facts after the event is commonly biased by the hindsight perspective and the aim of the paper is to investigate the amount and the potential effects of hindsight bias in terms of citizens risk perception and community resilience.Method:We performed a qualitative analysis of the narratives in the national and local news reports during the aftermath to investigate occurrences of a blaming attitude and cognitive biases. Results: The results showed a considerable amount of sentences that were focused on blaming the forecasters, the Civil Protection System, and the local administration. Many narratives were affected by hindsight bias and described the events as simple and linear chain reactions. This led to counterfactual biases, assuming that a simple intervention on a single factor could have prevented the tragic outcome. Conclusion: We claim that the biased nature of the media narratives could affect the citizens\u2019 risk perception and their attitude towards the institutions, increasing their exposure to future flood-related threats. We propose the appropriate language would generate correct cognitive frames and, therefore, safer behaviou

Innovative SMC Insulation Technique Applied to Axial Flux Machine Prototypes

The paper describes in detail the realization of an axial flux machine prototype adopting an innovative Soft Magnetic Composite (SMC) material. The novel technique here presented regards a Layer-by-Layer deposition adopted to insulate pure iron powder grains previously selected. The obtained material is then used to prepare the machine's stator parts. The activity steps are detailed: from the powder preparation to the molding phase, the consequent milling for the final shape, and the consequent magnetic, energetic and mechanical characterization. The prototype design and assembly imply the realization of the stator with the adopted innovative material, and the Authors also realized the preparation of the rotor equipped with bonded magnets. The preliminary experimental results are presented at the end, and considering the machine to be the first trial with the presented material, the efficiency of 77% should be viewed as a promising result for the future development of the activity

Aluminium alloy addition effects on the behaviour of soft magnetic materials at low frequencies

The present paper focused on the effects of aluminium alloy addition on the behaviour of soft magnetic materials at low frequencies. The microstructure investigation reveals that for materials with high aluminium contents, the pores are oriented near or surrounding the aluminium particles. The microstructure investigation reveals that for materials with high aluminium contents, the pores are oriented near or surrounding the aluminium particles, as well as after heat treatment shows coarse-grained structure with a minimum number of inclusions within the grains and at the grain boundaries. Results show that the magnetic properties are dependent on the structural state of the investigated material. Magnetic properties increased with decreasing density due to the enhanced densification by means of applied pressing pressure and promote porosity reduction during heat treatment