Fabrizio Marignetti

Design of Axial Flux PM Synchronous Machines Through 3-D Coupled Electromagnetic Thermal and Fluid-Dynamical Finite-Element Analysis

This paper investigates the thermal behavior of axial flux synchronous permanent-magnet machines (AFSPMMs) through a 3-D thermal-magnetic finite-element analysis (FEA). This paper offers a systematic approach to magnetothermal FEA. The considered axial flux machine is wound on a soft magnetic compound core. The computation of thermal field is performed via a coupled thermal and fluid-dynamical model based on FEA, where the thermal sources are obtained from a DC current flow model and a magnetostatic model. This paper includes an overview of the finite-element method (FEM) model implementation. Simulation results are presented, and, to validate the model, the simulated surface temperature rise of the motor parts is compared by experimental data.

A Tubular-Generator Drive For Wave Energy Conversion

This paper illustrates the operation of a tubular-machine drive as a linear generator for a heave-buoy wave energy conversion. Linear generators, which are adopted in marine power plants, offer the advantage of generating without introducing any conversion crank gear or hydraulic system. The use of a tubular-machine topology allows the electromagnetic thrust density to be improved. This paper briefly summarizes the principles of marine wave buoy interaction and reports the design analysis and control of a permanent-magnet (PM) synchronous tubular linear machine based on a scaled generator prototype and on a rotating simulation test bench

Multiphysics Approach to Numerical Modeling of a Permanent-Magnet Tubular Linear Motor

This paper presents a multiphysics modeling through finite-element (FE) coupled electromagnetic and thermal field analysis of a permanent-magnet tubular linear motor (PMTLM). Two-dimensional axial-symmetric FE steady-state and transient solutions are first obtained for the magnetic-flux-density distribution, cogging force, thrust, and losses of the PMTLM prototype. The FE magnetic field results are then used for the 3-D FE thermal simulation to get the PMTLM temperature distribution. This paper proves that the multiphysics numerical field analysis is a viable tool for the design and performance optimization of PMTLMs. The accuracy of the proposed study has been assessed through prior analytical and experimental results. Regarding the design aspects, some peculiarities in the thermal behavior of PMTLMs are emphasized. Generally, thermal models being not ready to develop, experimental and analytical solutions remain a preferred choice.

Electromagnetic Analysis of Axial-Flux Permanent Magnet Synchronous Machines With Fractional Windings With Experimental Validation

Axial-flux permanent magnet (PM) synchronous machines are suitable for direct drive applications. Axial-flux PM synchronous machines with fractional windings provide high power density, low torque ripple, and sinusoidal phase voltages, but suffer from high rotor losses due to stator field harmonics and slotting. This paper formulates an electromagnetic model based on the polar coordinate representation of the air-gap magnetic field. No-load and load tests are carried out on a soft-magnetic-composite stator axial-flux machine to validate the model. Rotor losses represent the largest loss figure in this machine. Most rotor losses are due to slotting harmonics.

Effect of Inclined Static Eccentricity Fault in Single Stator-Single Rotor Axial Flux Permanent Magnet Machines

This paper studies the effects of static eccentricity on axial flux permanent-magnet machines (AFPMMs) using three-dimensional finite-element analysis (3-D FEA). Use of numerical modeling makes it possible to precisely study the eccentricity in these types of machines. The accuracy of the FEM model is validated using experimental measurement. To the best awareness of the authors, effects of static eccentricity in AFPMMs have not been studied before. Hence, a new definition for the static eccentricity factor (SEF) is presented and it is shown that the occurrence of static eccentricity is very high in these types of machines. A motor with different degrees of rotor eccentricity is simulated and the flux density distribution in the air gap and the total axial force between rotor and stator is obtained. In addition, unbalanced magnetic force (UMF) is calculated and it is mentioned that a steady torque is created by the forces. This study indicates that static eccentricity has noticeable effects on motor characteristics and can deteriorate the motor performances.

Analytical and Multiphysics Approach to the Optimal Design of a 10-MW DFIG for Direct-Drive Wind Turbines

This work deals with a 10-MW doubly fed induction generator (DFIG) for direct-drive operation of wind turbines with a reduced-size converter. The work includes a lumped parameter design, an optimization procedure, a finite-element analysis (FEA), and an electrical performance assessment. A monetary cost was assumed as a cost function, and an approximation of the construction cost as a function of the axial length was obtained. The found solutions were checked by FEA in order to assure the mechanical feasibility. Further verifications were developed to allow a conclusive performance evaluation. The optimization improved the cost of the proposed DFIG, including materials, losses, and converter, making it slightly cheaper than an available permanent-magnet synchronous generator.

Thermal Analysis of an Axial Flux Permanent-Magnet Synchronous Machine

The paper presents a thermal analysis of an axial flux synchronous permanent-magnet machine (AFSPM) with a core of soft magnetic composite (SMC) material. We obtained the temperature distribution by using a coupled thermal and fluid dynamic finite-element model. The study considers two 2-D approaches and compares their results to experimental tests.

A System-on-Chip Sensorless Control for a Permanent-Magnet Synchronous Motor

This paper investigates a system-on-programmable-chip permanent-magnet synchronous-motor drive speed and position sensorless control. The proposed approach exploits two field-programmable gate-array capabilities, namely, the fast computation and the hosting of long finite-impulse response filters. Such filters allow an accurate reconstruction of the position signal by means of phase compensation and lead to an improved speed estimation based on the zero-crossing detection of the commutation signals. This paper presents the design flow and confirms the feasibility of the approach by means of hardware-in-the-loop simulations and experimental tests.

Assessment of Fuel Cell Performance Under Different Air Stoichiometries and Fuel Composition

The behavior of fuel cells (FCs) at steady state and during transients is an important factor both for control tuning and for performance assessment. In the technical literature, few papers deal systematically with FC characterization. In this paper, the performance characterization of a proton exchange membrane (PEM) FC is carried out using an experimental analysis. The experimental activity has been conducted in a test station, properly designed and able to test PEM FC stacks in the range of 500-2000 W. The laboratory test facility is equipped with a National Instruments CompactDAQ real-time data acquisition and control system running a LabVIEW software. The bench commands two mass flow controllers, regulating both fuel flow and air flow which are commanded via two Recommended Standard 232 ports. The temperature of the FC is regulated via a fan operated by a brushless motor drive. An electronic load is connected to the FC terminals. The main operating parameters, such as the air stoichiometric ratio and fuel composition, have been varied and measured, and their influence on the PEM FC behavior has been investigated under both steady-state and transient conditions.

Modeling and Control of a Zero-Current-Switching DC/AC Current-Source Inverter

Choosing a dc/ac converter is mainly a compromise among three major issues, namely: 1) efficiency; 2) waveform quality; and 3) cost. This paper considers a zero-current-switching (ZCS) current-source inverter (CSI) as a viable choice for many applications. It features low conduction and switching losses, inherent output filtering, capability of withstanding short circuits, and the opportunity to use thyristors. Despite these promising characteristics, this inverter exhibits a nonlinear relationship between the modulation index and the output current. Moreover, the resonant modes that are generated by the load-filter interaction must be damped. Since the previous aspects require a proper control law, a model of the system is very useful for defining and tuning a control structure. Thus, after providing a functional overview of the ZCS dc/ac CSI, this paper formulates a large-signal model and then derives and simplifies the averaged one. Numerical data are used to validate the models that are obtained. An active damping control for a motor drive is defined and tuned by means of the simplified averaged model, and its effectiveness is numerically validated. Experimental results conclude this paper.