Roberto Di Stefano

An Online Method for Static Eccentricity Fault Detection in Axial Flux Machines

This paper investigates a novel online method for static eccentricity (SE) fault detection of single-stator-single-rotor axial flux permanent-magnet (AFPM) machines. The method allows for both estimating the SE factor and computing the minimum air-gap position. As direct flux measurements are expensive, the proposed method for fault detection is based on the measurement of the voltages of three search coils uniformly distributed in the air gap. Unlike the current spectrum-based fault detection methods on which the winding configuration has a considerable impact, the proposed method can be used for any type of AFPM machine independently on the winding layout. A simplified 2-D analytical approach is used. Moreover, a circuit-coupled 3-D finite-element method (FEM) was used to compute the induced voltages in the search coils and show the validity of the method through 20 eccentric scenarios. Moreover, an experimental setup was built to validate the analytical approach and to confirm the results achieved with the 3-D FEM. Several experimental measurements have been done. All measurements confirm the accuracy of the proposed method. It is also shown that the method yields accurate results under any load condition.

Design of a System-on-Chip PMSM Drive Sensorless Control

The Sliding-Mode Position and Speed Observer is a simple and well-known mechanical sensor-less solution for Permanent Magnet Synchronous Motors (PMSMs) that is inherently robust in the medium-high speed range. The paper proposes a Field Programmable Gate Array (FPGA) implementation of a simple observer exploiting the high computational power of the device aiming to improve the speed estimation behavior and to make a step towards a System on Programmable Chip (SOPC) sensor-less PMSM drive.

Traction Control for a PM Axial-Flux In-Wheel Motor

The traction control is a tool to increase stability and safety of vehicles and it has a greater performance potential in electrical vehicles than in ICV. Moreover, the traction control allows the EV to operate more efficiently preventing slippage in acceleration and permitting the use of high-efficiency low-drag tires. The presented approach can compete with the well-established techniques, but it offers a lighter tuning procedure. This paper presents an approach to the longitudinal control of a single wheel adopting a configuration based on an adherence estimator and a controller of the adherence gradient. The presented approach allows tracking of the value of the adherence derivative in a wide operating range without any knowledge of the road conditions. The work is based mainly on experimental tests. the test rig computes the vehicle dynamics in real-time and loads accordingly the drive under test. The controller was experimentally verified showing good behavior.

Feature Investigation of a T-LPMSM Following the Selection of Its Slot-Pole Combination

This paper investigates the no-load and the on-load behavior of a fractional-slot tubular-linear permanent magnet synchronous machine (T-LPMSM). The study is initiated by the selection of the machine slot-pole combination. To do so, a formulation of the air gap flux density, based on the solution of the magnetic potential vector equation in the air gap and in the PM regions, is derived. The electromagnetic model allows the prediction of the phase back electromotive forces (EMFs) and of the cogging force. The effect of the slot-pole combination on these features is then considered to the aim of the optimal selection of the slot per pole and per phase. A case study considering the optimized slot per pole and per phase number is treated where the analytically predicted no-load features are validated by finite element analysis (FEA). The investigation is extended to the on-load characteristic which is predicted by FEA and is validated by experiments.

An Axial Flux Permanent Magnet Machine with charged polymer stator core

This paper proposes an Axial Flux Permanent Magnet Machine with cast-injection charged-polymer stator core. The motor is for a washing machine direct-drive. The paper presents the design procedure, the stator production process and the experimental characterization of the prototype.

A comparative analysis of 4KW PSBs for welding machine

The paper deals about the study conducted to evaluate the reliability of H bridge topology, for a DC/DC converter with phase-shift modulation strategy, with three different power devices. The first one is based on 500 V 0.087? 46 A HEXFET/sup /spl trade// power MOSFETs, the second one adopts MDmesh/sup /spl trade// power MOSFETs with external Schottky and ultrafast diodes in order to shunt the reverse current and the third one is based on CoolMOS power MOSFETs integrating the diodes in the same package. Each of them is reviewed, prototyped and investigated. Experimental results show the technological limits of each solution and suggest their right application range.

DSP controlled soft-switching full-bridge DC-DC converter

The paper presents a DSP controlled isolated output DC-DC power converter, designed for applications where a particular output characteristic is required and the load could have strong nonlinear behavior. The use of a DSP, with a fixed point ALU, instead of a dedicated IC or custom mixed signals circuits improves the whole design with respect flexibility and independence from IC manufactures and distributors. Moreover the application dependent algorithms, coded in C language, can be easily tested, implemented and updated. This is the most important demand for this converter which must be useful in a wide range of applications were a specific output characteristic is one of the main requirements.

On the design of fractional slot T-LPMSMs: effect of the slot-pole combination

The paper deals with an approach aimed at the design of fractional-slot tubular-linear permanent magnet synchronous machines (T-LPMSMs) with emphasis on the effect of the slot-pole combination. Following the description of the T-LPMSM concept under study, the developed approach is initiated by a formulation of the air gap flux density, based on the resolution of the magnetic potential vector equation in the air gap and PM regions which enables the prediction of the cogging force and the phase back-EMFs. The effects of the slot-pole combination on these features is considered in the second part of the study which is achieved by the selection of an optimized slot per pole and per phase number that yields a high phase back-EMF amplitude and a low cogging force peak-to-peak value. A case study considering the optimized slot per pole and per phase number is treated where the analytically predicted results are validated by finite element analysis.

An online eccentricity fault detection method for Axial Flux machines

An eccentric air-gap creates an electromagnetic force between the rotor and the stator of electrical machines. This force is known as unbalanced magnetic pull (UMP). This force leads to further increase the eccentricity and may severely reduce the performance of the machine, producing acoustic noise, vibration, excessive wear of bearing, rotor and stator rubbing. This paper presents a universal online method for diagnosing eccentricity in Axial Flux Permanent Magnet (AFPM) Machine. It is based on measuring the induced voltages of three search coils positioned above the coils of three phases as a suitable criterion for fault detection. Using this number of search coils enables not only the Static Eccentricity Factor (SEF) but also the minimum air-gap position to be estimated. The Three-Dimensional Finite-element Method (3D-FEM) was used to accurately analyze the machine and to validate the method. This study indicates that the induced voltages of the search coils suggest an online method for indirectly measuring eccentricity during machine operation.

Pole Shape-Based Reduction of the Harmonic Content of the IPM T-LSM Air Gap Flux Density

This paper presents a sizing approach dedicated to the reduction of the harmonic content of the air gap flux density of interior permanent magnet tubular-linear synchronous machines (IPM T-LSMs) based on pole shaping. The study is initiated by a formulation of the air gap flux density of conventional IPM T-LSMs equipped with flat-shaped poles. In the second step, the established model is reformulated with emphasis on the pole shape variation characterized by two parameters: the pole air gap radial width and the pole head opening. Following its experimental validation, the resulting model is applied to the sizing of the pole shape in an attempt to reduce the harmonic content of the air gap flux density. The developed sizing procedure considers the effect of the above-defined parameters on the harmonic content of both the radial and axial components of the air gap flux density. The study is achieved by the selection of a set of parameters for which both radial and axial components of the air gap flux density exhibit their lowest spatial harmonic distortion.