S. Di Fraia

Analysis of the Dynamic Behavior of a Linear Induction Type Catapult

The electromagnetic launcher, widely studied as electromagnetic gun, may also be used as a catapult for electromagnetic acceleration of aircrafts to replace steam catapult. These launchers can be realized utilizing a synchronous or asynchronous type of linear accelerator. In this paper, the second realization, which is the use of an asynchronous type of linear accelerator, is considered. Thus, a system consisting of a fixed part, realized with several sections and a moving part that brings the sled supporting the object to launch, is proposed. Each section contains a three-phase winding fed by different frequencies. The goal of this paper is to investigate moving part braking strategies once the mass has been launched. It is proposed that a method of electromagnetic braking can possibly allow the recovery of the kinetic energy.

Parallelogram-shaped hysteresis loops for describing the energetic magnetic behavior of hysteretic media

The characterization of the energetic magnetic behavior of hysteretic materials and the determination of the surface impedances are proposed. A numerical model in time domain is adopted for the calculations. The use of parallelogram-shaped hysteresis loops allows for simplifying the numerical formulation and for reducing the computation time with respect to more accurate models. Equivalent major loops have been defined starting from the measured ones. Comparison with the modified scalar Preisach model is presented and discussed.

Stable FDITD formulation for electromagnetic field diffusion in soft magnetic materials

In this paper, a stable finite difference discretization is defined for problems of electromagnetic field diffusion in nonlinear hysteretic media. More precisely, the numerical formulation consists of a Crank-Nicolson-like algorithm applied to a space-centered finite difference scheme for nonuniform point distribution. Following the von Neumann analysis, the unconditional stability of this implicit two-level/three-point scheme is established. Moreover, the good behavior of this formulation has been numerically verified for very critical soft material like ferrites and irons.

Analysis of shielding performance in nonlinear media

In this paper, the shielding performance of a nonlinear magnetic material with hysteresis at extremely low frequency has been investigated. A one-dimensional in space finite-difference implicit time-domain algorithm has been implemented on the geometry of a shield with axial-symmetry. A scalar Preisach model has been adopted for taking into account the multistable point behavior of the medium and an online strategy for the Preisach function implementation has been used. Simulation results are here presented and discussed.

Implementation of the modified Preisach scalar model in the finite difference–time-domain numerical modeling

Abstract In this paper, we present a numerical procedure capable of analyzing dynamic hysteresis in axial-symmetric problems. The procedure is based on the implementation of the modified scalar Preisach model (MSPM) in a finite difference–time-domain algorithm. The identification of the Preisach function in the MSPM is obtained through experimental measurements of the virgin curve and of the major loop. Simulations have been performed on systems operating at extremely low frequency under the hypothesis of negligible effects related to the displacement current and assuming as input source the magnetic field value at the one surface of the cylindrical domain under analysis.

Shielding effectiveness measurements for ferromagnetic shields

This paper proposes a new way to measure the shielding effectiveness of ferromagnetic shields. The procedure combines an experimental characterization of the shielding material and numerical simulations. In a first case, magnetic hysteresis is reduced to a series of equivalent B -H linear relations through an optimization procedure that is applied to a measured set of symmetric minor loops, and an equivalent multilayer linear medium is defined through a subsequent iterative procedure. In a second case, magnetic hysteresis is reduced to a simple B-H nonlinear relation, obtaining an equivalent nonlinear shield. In both cases, the obtained results are compared with the direct measurements of the shielding effectiveness at different operating frequencies, showing good agreement and the validity of the proposed method. A comparison and a discussion on the harmonic content of the attenuated field for the investigated shield geometry are reported. The same analysis is carried out for a basic diffusion problem, comparing the results with those obtained by the use of a Preisach model.

Design of Multistage Linear Induction Motor used as electromagnetic catapult

In this paper the authors describe an analytical procedure for preliminary design of Multistage Linear Induction Motor (MLIM) operating as heavy mass electromagnetic catapult. Through the use of the sheet current method we derive the thermal, mechanical and electrical modeling. The implemented methodology enables to individuate and optimize the main parameters of the system and in particular the number of barrel sections. The main steps of the procedure are clearly explained and discussed throughout the paper. Finally, we show the main quantities of interest calculated for a designed prototype.

Characterization of EM Emission During the Operation of Solid and Plasma Armature Rail Launchers

We present the results of an experimental analysis aimed at investigating the electromagnetic (EM) emission during rail launcher operation. In order to obtain such data, an experimental setup was assembled in a shielded semi-anechoic chamber, consisting of a pulsed power source-unit, a power coaxial cable and a rail launcher prototype. Several experiments were performed for different operating conditions and results were repeatable. Finally, we provide a qualitative modeling of some sources of electromagnetic transients and we discuss basic aspects driving the EM emission phenomena in railgun systems.

Modeling and analysis of a Multistage Linear Induction Motor fed by a permanent magnet flywheel motor-generator

In the present paper the authors analyze the dynamic behavior of a Multistage Linear Induction Motor (MLIM) fed by means of a suitable back-to-back converter supplied through a flywheel energy source. The MLIM is used as a heavy mass launcher. The final velocity is several tens of m/s. Regenerative braking mode is also studied, as well as the shuttle recovering phase. The dynamic mathematical model of the whole system (flywheel-converter-MLIM) has been implemented in the Simulink® environment. Several simulations have been carried out and main results are discussed.

Design of Plasma Launcher With Gyro Stabilized Launch Mass

This paper considers the design of a plasma electromagnetic launcher aimed at determining the gyroscopic stabilization of the launch mass. The basic idea is to provide the rotation to the projectile during its acceleration inside the bore by means of a rotating magnetic field. In order to create the rotating field, a three-phase winding coil system is adopted. The design procedure of the main elements (the rails, the coil system, and the projectile) of the electromagnetic device is described in detail. The results obtained for the specific case of a launch mass of about 8 kg with outgoing velocity of 2 km/s are reported and discussed