Fabrice Morganti

Non Invasive Sensors for Monitoring the Efficiency of AC Electrical Rotating Machines

This paper presents a non invasive method for estimating the energy efficiency of induction motors used in industrial applications. This method is innovative because it is only based on the measurement of the external field emitted by the motor. The paper describes the sensors used, how they should be placed around the machine in order to decouple the external field components generated by both the air gap flux and the winding end-windings. The study emphasizes the influence of the eddy currents flowing in the yoke frame on the sensor position. A method to estimate the torque from the external field use is proposed. The measurements are transmitted by a wireless module (Zig-Bee) and they are centralized and stored on a PC computer.

Dependence of the contact resistance on the design of stranded conductors.

During the manufacturing process multi-strand conductors are subject to compressive force and rotation moments. The current distribution in the multi-strand conductors is not uniform and is controlled by the transverse resistivity. This is mainly determined by the contact resistance at the strand crossovers and inter-strand contact resistance. The surface layer properties, and in particular the crystalline structure and degree of oxidation, are key parameters in determining the transverse resistivity. The experimental set-ups made it possible to find the dependence of contact resistivity as a function of continuous working stresses and cable design. A study based on measurements and numerical simulation is made to identify the contact resistivity functions.

3D electro-mechanical modeling of conductor after stranding and compacting process simulation

In this paper we propose a new method using finite elements modelling to predict the impact of stranding and compacting process on a conductor electrical resistance. The experimental work has highlighted the complexity of physical phenomenon within the conductor caused by elastic and plastic deformations and inters-strands electrical contact resistance. In reality, electrical performance of a conductor depends on the nature of the material and its metallurgical state, on the me- chanical pressure and electrical conductance of inter-strands contact areas. For these reasons, mechanical models have been developed in Abacus software to study different parameters involved in the stranding and compacting process to determine the actual conductor shape, strands actual deformations, residual stresses and contact pressure, etc. The deformed geometries were exported to COMSOL Multi-physics software using ECAD IMPORT module. DC simulations were, then, performed to analyze the electrical resistance of the conductor. Finally, the results obtained by simulation have been compared to the measurements to determine the accuracy of the models.

Non-invasive detection of winding short-circuit faults in salient-pole synchronous machine

This study presents an analytical and experimental method for detecting internal turn-to-turn short circuits both in the rotor or in the stator in Salient-pole Synchronous Generator Machines (SSGM) connected to local power grid. Two main measurements are proposed to confirm or discard these electric faults: External Magnetic Flux Density (EMFD) and External Housing Vibrations (EHV). In the event of a short-circuit winding fault, a correlation between EMFD and EHV is confirmed. Furthermore, the electric power injection dependency is introduced in order to establish the validity range of this method. In this study, only non-invasive and on-line equipment are required to diagnose the SSGM. A diagnostic tool has been developed to show the viability of an operative wireless monitoring system in an industrial environment.

Using ARDUINO development platform in the diagnosis of AC electrical machines

Low cost electronic platforms based on Atmel microcontroller, as Arduino platform, are used in many applications and in several fields. Indeed, their characteristics in terms of inputs, outputs, CPU and RAM make possible to develop rapid smart-systems for measurement avoiding additional components. CPU and RAM performance allows analyzing complex numerical signals. The aim of this paper is to show some boarddevelopments (ARDUINO UNO, M0 and DUE) coupled with specific sensors for electrical rotating machine applications in industrial environment.

Impact of supply voltage variations on external magnetic field emitted by induction machines

Purpose This paper aims to study the influence of supply voltage variations on the external magnetic field emitted by grid-powered induction machines (IMs). Design/methodology/approach Two models are developed in the paper to analyse, for different supply voltage values, the influence of the variations of the magnetizing voltage for which there is a link with the tangential component of the external flux. The first is an analytical model based on the IM single-phase-equivalent circuit with variable magnetizing reactance to take into account the saturation of the magnetic circuit. The second is a numerical finite element simulation to model the same phenomenon. Results of both models are analysed with experimental measures of the external flux. Findings The study shows that the amplitude of the external field strongly depends on supply voltage values. Research limitations/implications The investigation is mainly focused on the tangential component of the external magnetic field which is of high importance concerning the applicability of non-invasive methods of diagnosis, as electromagnetic torque estimation developed by the authors or internal fault determination. Originality/value The originality of the paper concerns the characterization of the external flux with the supply voltage for IMs. It is shown that the magnetic circuit radiates external flux differently with the load and with the supply voltage.

AC Variable-Speed Drives and Noise of Magnetic Origin: A Strategy to Control the PWM Switching Effects

The presented developments concern the definition of a method to characterize simply the pulse width-modulated (PWM) switching three-phase harmonic systems. This characterization, which makes it possible to control the components generated by the switching anticipating the negative effects possibly generated, is exploited in the context of reducing the noise of magnetic origin that can affect the operating of AC variable speed drives.