Virgiliu Fireteanu

Magneto‐thermal‐motion coupling in transverse flux heating

Purpose – This paper aims to deal with the 3D finite element analysis of metallic sheets heating in translating motion through the air gap of an inductor of transverse flux type.Design/methodology/approach – This study presents two finite element based motion coupling techniques used to analyze the transient temperature field of moving metallic sheets heated by induction.Findings – The numerical results obtained by the two different magneto‐thermal – translating motion coupling techniques proposed in this paper are in good agreement with each other being validated also by experimental measurements.Practical implications – The proposed numerical techniques can be used for the design and optimization of transverse flux induction heating systems.Originality/value – An original solution to improve the transversal thermal profile of the metallic sheet based on the magnetic shielding is proposed and analyzed. The numerical results of the thermal field are validated by experimental measurements.

Diagnosis of induction motor rotor faults based on finite element evaluation of voltage harmonics of coil sensors

The paper deals with the finite element evaluation of the electromagnetic field associated with the induction motors operation and with the diagnosis of rotor faults based on the time and space dependent magnetic field outside the motor. The effects of one squirrel cage broken bar and of rotor eccentricity on the electromagnetic torque and force and on the external magnetic field are presented. Solutions for on-line or off-line faults diagnosis based on the output voltage of coil sensors placed in the motor neighbourhoud are analysed.

Numerical simulations of continuous induction heating of magnetic billets and sheets

The relative motion between the inductor and the work‐piece to be heated, the magnetic non‐linearity and the dependence of physical properties on temperature are considered in the numerical simulations of continuous transverse flux induction heating of metallic sheets and scanning type induction heating of billets. Using the translating air‐gap technique, the transient and the steady state electromagnetic and thermal fields are evaluated.

Eddy currents in thin plates modelled as surface regions

This paper analyses the conditions for which the results of eddy currents computation in thin regions modelled by surface regions are concordant with those obtained using volume finite elements. The concepts of geometrically thin or thick region, electromagnetically thin or thick region, 2D or 3D problem, transverse or longitudinal flux problem are used to characterise the limits of the surface model. The computation of eddy currents in sheets heated in transverse flux inductors and of the eddy current losses in metallic casing of an induction furnace highlights the surface finite element applicability.

Finite element analysis and diagnosis of the one broken bar fault in the squirrel cage induction motors

The paper deals with the finite element analysis of the electromagnetic field in a medium power squirrel cage induction motor and with the diagnosis of a rotor fault based on the time and space dependent magnetic field outside the motor. The effects of the one broken bar fault on the electromagnetic torque, on the rotor-stator interaction force and on the external magnetic field are evaluated. The harmonics of the output voltage of a coil sensor are determined for the motor without and with magnetic steel encasing, thick enough with respect the diffusion of the main traveling electromagnetic field of the motor. The influence of the motor load on the fault diagnosis efficiency based on the output voltage harmonics is analyzed.

Transient magnetic — Translating motion finite element model of the Annular Linear Induction Pump

In the context of replacing the mechanical pumps with high flowrate Annular Linear Induction Pumps (ALIP) for the Generation IV of nuclear plants in France, the paper constitutes a study of startup, steady state operation and dynamic behavior of a double sided ALIP in bloc pumping assumption, based on finite element transient magnetic - translation motion coupling models. Using a model of pump load proportional with the square of the flowrate, the Electromagnetic Pressure - Flowrate characteristic was determined and considered further in expressing what a stable pump operating state represents. Data regarding the highest admissible jump load are given. The dependence on flowrate of pumping efficiency is presented and provides with a view regarding the maximum capabilities of such devices of converting electrical energy into motion.

Transverse flux induction heating: comparison between numerical models and experimental validation

This paper presents two numerical methods, which will be able to predict the temperature distribution in the thin moving conducting sheet, which is caused by the eddy‐current losses in transverse flux inductive heating devices (TFIH). The first method is based on a finite element calculation, while the second one is based on a circuit approach. The main aim of this paper is the validation of the circuit model by comparison with the more accurate and sophisticate finite element model. In addition, the results of both numerical models have also been compared with those obtained by experimental measurements.

From the 2D to 3D finite element analysis of the broken bar fault in the squirrel-cage induction motors

This paper reflects the evolution from the 2D to the 3D finite element analysis of the squirrel-cage induction motors related to the evaluation on the influence of the broken bar fault and the investigation of methods for the efficient fault detection. Based on the scalar 3D formulation of the electromagnetic field and through the step by step in time domain finite element solution, the time dependence and harmonics of the electromagnetic torque, rotor unbalanced force, stator currents and of the magnetic flux density in points outside the motor are computed. Important harmonics of the stator currents and of the magnetic field outside the motor with respect the efficiency of fault detection are identified.

Finite element models of the transient heating of squirrel-cage rotor during induction motors startup

This paper presents finite element models for the study of heating of the squirrel-cage rotor of the induction machines during motor startup. The transient magnetic and the magnetoharmonic models of the induction machine are used in the studies of squirrel cage adiabatic heating and magnetothermal rotor heating. The multiphysics model, which rigorously reflects the transient heating of the rotor, is a coupling between the transient magnetic model of the induction machine and the thermal transient model of the rotor heating.

Electromagnetic pumping of molten salts

This paper investigates the possibility to control through electromagnetic pumping the molten salts flow in high temperature heat transfer applications. Based on finite element models there were evaluated and compared parameters of multi-phase induction pumps with cylindrical, annular or flat pumping channels and of conduction pumps with ac or quasi-dc electric power supply.