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In this paper, we propose a dynamic model of the electrical transformer suitable for the numerical prediction of the inrush currents due to the arbitrary initial excitation of a transformer after a switch-OFF. In particular, the proposed model can be helpful to control strategies to avoid a transient current overshoot, based on the prediction of the residual magnetic flux.

Muon triggering and offline muon identification are fundamental requirements for the LHCb experiment, which will begin to take data at the start-up of the LHC machine. The identification of muon particles and an estimate of the transverse momentum ( Δ p T / p T ∼ 20 % ) in the near-beam area of the first muon station is achieved by a set of 12 double triple-GEM detectors which covers an area of about 0.6 m 2 . Since b-quark production is peaked in the forward direction, GEM detectors will trigger about 20% of muons from B-particle decays. In this paper the results of the detector quality checks on anode and cathode panels planarity, GEM foil HV test, chamber gas leak and gain uniformity are presented. The performance of a chamber, composed of two triple-GEM detectors logically OR-ed, has been measured in a recent test beam at the SPS, with particle bunches with a time structure of 25 ns similar to the LHC running conditions. In this test the final front-end electronics and the final LHCb DAQ have been used. This result demonstrates that the detector can achieve the required performances (efficiency larger than 96%) at a detector gain of 4000, thus ensuring a long detector lifetime in the harsh LHCb environment.

This paper deals with a particular magnetic nondestructive technique applied to the control of the position of the steel blades in rotating parts of turbines and engines. The working principle is based on a bridge of four identical magneto-resistive sensors. One sensor is placed near the blades, and the change in magnetic field produced by a permanent magnet and deviated by the change in position of the blade is detected by the sensor bridge. The position of the sensor is indicated, via dedicated FEM simulations, in order to have high sensitivity to the position change and high output signal. The accuracy and effectiveness of the proposed method are shown by experimental tests carried out in our laboratories. In particular, the tests indicate that the proposed magnetic nondestructive technique can be used in an almost large velocity range, and for quite different values of blade tip. The method seems also promising for the detection of blade vibrations.

In this paper, using suitable three-dimensional finite element method (FEM) approaches, either in frequency or in time domain, we will analyze the real magnetic behavior of a commercial Epstein machine, prescribed as standard magnetic measurement system. The analysis of magnetic field and eddy currents explains some facts that can affect the accuracy of Epstein frames as measuring systems for the magnetic characterization of laminated Si-Fe steels. The same FEM approaches shall be applied here to outline and define quantitatively some advantages in accuracy can be obtained using single sheet testers instead of Epstein frames.

This paper presents an experimental analysis of the rotational power losses of the magnetic materials of transformers, motors and actuators used in avionic environment. A large frequency range is investigated using a suitable experimental test frame developed to measure the power losses for a circular magnetization. The results about different silicon iron alloys with different textures and thickness are considered and compared.

In this paper we discuss the electro-thermal behavior of solid armatures in railguns. This discussion is based on a review of results obtained by a theory that takes into account the three-dimensional nature of melting and vaporizing of the contact surface between rail and armature. This theory is numerically treated by an integral approach based on a suitable decomposition of rails and armature in hexahedrons, bricks and filamentary elements. After a recall of the main points of this theory and the related numerical technique, this review paper describes the principal features about the current flow, the heat production and exchange, the presence of liquid and vapor phases at the contact face of the armature, derived by this theory. In particular the shape of the melt front and the critical transition velocity predicted are in agreement with the experimental observations.

In this paper an approach to the numerical analysis of the electromagnetic interference (EMI) radiated by metallic grids, like Faraday cages, hit by a lightning stroke is proposed. This approach is based on a hybrid differential-integral mathematical formulation in which a finite-difference time-domain scheme is used to evaluate the current density distribution inside the conductors, while the Kirchhoff's integral expressions are used for the computation of the transient electric and magnetic fields generated by the current flow into the grid. The introduction of a suitable scalar potential defined on the surface of the conductor allows to determine a complete set of boundary conditions for the problem of the magnetic diffusion of the current into the conductor and to reduce the region to be numerically treated by the differential formulation to the only conducting materials. Examples of application of the method to the numerical analysis of the EMI radiated by a Faraday cage struck by lightning are given.

This work deals with some energy properties of a vector thermal aftereffect model, recently presented. The model can compute magnetization and magnetic losses using an extension in 2-D of a Preisach-type approach. Some properties of the model are presented and discussed. An experimental validation is also included.

In this paper we present a single disk tester (SDT) developed for vector hysteresis measurements of magnetic steels. The measurement system deals with a stator of a 3-phase induction motor and some suitable magnetic field and magnetic induction probes. Numerical calculations based to a FEM approach in time domain and experimental tests are shown in order to describe both accuracy and efficiency of this measurement system.

The production of the triple-GEM detectors for the innermost region of the first muon station of the LHCb experiment has started in February 2006, and is foreseen to be completed by the end of July. The final design of the detector and the construction procedure and tools, as well as the quality controls are defined. The performances of each detector, composed by two triple-GEM chambers equipped with dedicated CARDIAC-GEM front-end electronics, are studied with a cosmic ray telescope. The cosmic ray telescope has been set up including all the final off-detector components.

The coupled problem of the three-dimensional diffusion of current and heat in railguns with a solid armature is formulated by means of a circuital approach. Rails and projectile are divided in a high number of small-size parallelepipeds, so that temperature and current density may be imagined uniform in every parallelepiped. By integrating Ohm's law over each parallelepiped an equivalent R-L electrical network is obtained, whose resistive and inductive parameters are evaluated by means of explicit analytical expressions, possible in the case of discretization in parallelepipeds. The voltage fall in the boundary layers between rail and moving armature are taken into account by means of suitable driven generators. The position of the projectile is deduced by the application of the virtual displacement principle, where the discretization in parallelepipeds allows one to express the Lorentz's force again by means of explicit analytical relations. The nonlinear differential equations system so obtained fully simulates the behaviour of a solid armature railgun, and is solved in time, updating at each time-step the coefficients variable with current density, temperature, and projectile displacement. >