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When approaching the design of a multipole magnet, such as a dipole, quadrupole, sextupole, and so on, it is highly advantageous to initiate the process by establishing the fundamental parameters. These parameters include conductor size, current density, inner and outer radius of the iron yoke, and more. This preliminary dimensioning enables the acquisition of the necessary specifications for the design. Within this report, analytical expressions for the magnetic field, Lorentz forces, and stored energy of multipole magnets with the cos(nθ) and sector coil configurations, both with and without the presence of an iron yoke, are derived. These derivations are based on the vector potential of a current line.

A novel and sustainability-oriented approach to the design of large-aperture iron-dominated magnets is proposed, focusing on its application to charged particle momentum detection in high-energy experimental physics. As compared to classical design techniques, a broader number of goals and constraints is taken into account, considering jointly the detection performance, the minimization of both the electrical power and magnet size, and the electromagnetic efficiency. A case study is considered for the detector magnet of a specific experiment, where the optimal design is pursued with semi-analytical tools, duly introducing the main quantities’ scaling laws in analytical form and successively validating the results with 3D numerical tools. A solution at higher energy efficiency is obtained, as compared to a more traditional design point of view. The proposed methodology can be fruitfully employed also in the design of magnets with a reduced ecological footprint in a number of other industrial and medical applications.

Experimental results and theoretical studies call for Reversed Field Experiment (RFX) machine and power supply improvements to allow studies that go beyond those of a conventional Reversed Field Pinch (RFP) with passively stabilized turbulent MHD dynamo. The RFX experiment, in operation at Padua (Italy) since 1992, is the most important RFP machine in the world. The RFP magnetic configuration is actively studied in Europe, USA and Japan for its perspectives in reach the fusion conditions at low magnetic field and for the particular scientific interest of plasmas in this configuration. The new paths on the MHD mode studies and control, opened by recent results in RFX and other RFP machines, are introduced. Then the goals and the design lines of the technical modifications of RFX, mainly addressed to actively interact with the MHD modes through the control of the plasma magnetic boundary are reported. The main modifications introduced are related with the improvement the first wall, the addition of 192 saddle coils around the shell and to increase the operational flexibility of the toroidal field circuit power supply.

This paper proposes an observer-based volts-per-hertz (V/Hz) control method for synchronous motors. The method is applicable to any synchronous motor type, from permanent-magnet (PM) motors to synchronous reluctance motors (SyRMs). The method consists of a state-feedback control law and a state observer, both of which are designed to be inherently sensorless. The gains can be selected using simple closed-form expressions, resulting in a locally stable and passive system in the whole feasible operating range. Unstable regions and heuristic tuning of conventional V/Hz control are thus avoided. Compared to sensorless field-oriented control, neither speed controller nor separate field-weakening method is needed, the full inverter voltage can be utilized, and the sensitivity to parameter errors is reduced. For the majority of industrial drive applications, the dynamic performance of the proposed method is adequate. Peer reviewed

Frustration of magnetic systems which is caused by competing interactions is the driving force of several unusual phenomena such as plateaus and jumps of the magnetization curve as well as of unusual energy spectra with for instance many singlet levels below the first triplet state. The antiferromagnetic cuboctahedron can serve as a paradigmatic example of certain frustrated anti ferromagnets. In addition it has the advantage that its complete energy spectrum can be obtained up to individual spin quantum numbers of s=3/2 (16777216 states). (C) 2008 Elsevier Ltd. All rights reserved.

Reconnection events in high current reversed field pinch plasmas are often associated to the partial or total transitions from a helical topology with conserved flux surfaces to a configuration characterized by a chaotic magnetic field. The electron temperature dynamic together with the magnetic energy reconstructions are used to evaluate the energy balance during these events and to quantify the associated dissipated power and released energy. A fraction of the energy released during reconnection events is involved in ion heating, as estimated by the energy distribution function of neutral atoms, a rather interesting feature in a reactorial perspective.

Reconnection events in high current reversed field pinch plasmas are often associated to the partial or total transitions from a helical topology with conserved flux surfaces to a configuration characterized by a chaotic magnetic field. The electron temperature dynamic together with the magnetic energy reconstructions are used to evaluate the energy balance during these events and to quantify the associated dissipated power and released energy. A fraction of the energy released during reconnection events is involved in ion heating, as estimated by the energy distribution function of neutral atoms, a rather interesting feature in a reactorial perspective.

The paper presents a novel configuration of an axial hybrid magnetic bearing (AHMB) for the suspension of steel flywheels applied in power-intensive energy storage systems. The combination of a permanent magnet (PM) with excited coil enables one to reduce the power consumption, to limit the system volume, and to apply an effective control in the presence of several types of disturbances. The electromagnetic design of the AHMB parts is carried out by parametric finite element analyses with the purpose to optimize the force performances as well as the winding inductance affecting the electrical supply rating and control capability. Such investigation considers both the temperature dependence of the PM properties and the magnetic saturation effects. The electrical parameters and the force characteristics are then implemented in a control scheme, reproducing the electromechanical behavior of the AHMB-flywheel system. The parameter tuning of the controllers is executed by a Matlab/Simulink code, examining the instantaneous profiles of both the air-gap length and the winding ampere-turns. The results of different dynamic tests are presented, evidencing the smooth air-gap changes and the optimized coil utilization, which are desirable features for a safe and efficient flywheel energy storage.

This paper describes the modeling of startup circuits in battery-less micropower energy harvesting systems and investigates the use of bond wire micromagnetics. The analysis focuses on step-up Meissner oscillators based on magnetic core transformers operating with input voltages down to approximate to 100 mV, e.g., from thermoelectric generators. As a key point, this paper examines the effect of core losses and leakage inductances on the startup requirements obtained with the classical Barkhausen criterion, and demonstrates the minimum transconductance for oscillations to occur. For validation purposes, a step-up oscillator IC is fabricated in a STMicroelectronics 0.32 mu m technology, and connected to two bond wire microtransformers, respectively, with a 1:38 MnZn ferrite core and with a 1:52 ferromagnetic low-temperature co-fired ceramic (LTCC) core. Coherently with the proposed model, experimental measurements show a minimum startup voltage of 228 mV for the MnZn ferrite core and of 104 mV for the LTCC core.