Browsing by Author "Sathyan, Sabin"

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Acoustic noise computation of electrical motors using the boundary element method
(2020-01-03) Sathyan, Sabin; Aydin, Ugur; Belahcen, Anouar
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper presents a numerical method and computational results for acoustic noise of electromagnetic origin generated by an induction motor. The computation of noise incorporates three levels of numerical calculation steps, combining both the finite element method and boundary element method. The role of magnetic forces in the production of acoustic noise is established in the paper by showing the magneto-mechanical and vibro-acoustic pathway of energy. The conversion of electrical energy into acoustic energy in an electrical motor through electromagnetic, mechanical, or acoustic platforms is illustrated through numerical computations of magnetic forces, mechanical deformation, and acoustic noise. The magnetic forces were computed through 2D electromagnetic finite element simulation, and the deformation of the stator due to these forces was calculated using 3D structural finite element simulation. Finally, boundary element-based computation was employed to calculate the sound pressure and sound power level in decibels. The use of the boundary element method instead of the finite element method in acoustic computation reduces the computational cost because, unlike finite element analysis, the boundary element approach does not require heavy meshing to model the air surrounding the motor.
Influence of magnetic forces and magnetostriction on the vibration behavior of an induction motor
(2019-01-01) Sathyan, Sabin; Aydin, Ugur; Lehikoinen, Antti; Belahcen, Anouar; Vaimann, Toomas; Kataja, Juhani
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper presents the vibration analysis and results of an induction motor through two kinds of magneto-mechanical coupling methods. The computation results are validated by comparing them with the vibration measurements of the motor. The role of both the magnetic forces and magnetostriction are examined and distinguished based on their contribution to the vibration behavior of the machine. It was found that the pole pair number of an induction machine can affect the way the vibrations caused by magnetostriction and magnetic forces either add up or oppose each other.
Investigation of the causes behind the vibrations of a high-speed solid-rotor induction motor
(2019-12-22) Sathyan, Sabin; Belahcen, Anouar; Lehikoinen, Antti; Aydin, Ugur; Boxberg, Fredrik
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper analyzes the causes of vibrations in a solid-rotor induction motor (SRIM) through electromagnetic Finite Element (FE) simulations and laboratory measurements. The computed results are compared with vibration measurements, and the electromagnetic causes of vibrations were discovered, including the fault related reasons. The machine under investigation is a 300 kW, 60 000 rpm, three-phase SRIM. The FE simulations are carried out in an open source FE library implemented in Matlab. Both magnetic forces and magnetostriction deformations are accounted for in the simulations. This magneto-mechanical coupling is implemented using a free-energy-based model. The harmonic analysis of the vibrations revealed that, the supply frequency components, the magnetic forces and the magnetostriction contribute to the electromagnetic causes of vibration, while there is a significant amount of vibration produced due to the rotor eccentricity in the motor.
Magneto-vibro-acoustic Computational Techniques for Electrical Machines
(2020) Sathyan, Sabin
School of Electrical Engineering | Doctoral dissertation (article-based)
This thesis investigates the electromagnetic, magnetomechanical and vibro-acoustic interactions in an electrical machine, and proposes numerical computational tools and experimental techniques for modeling these phenomena in electrical motors. In an electrical motor, the supplied electrical energy goes through different physical domains in the form of magnetic, mechanical, acoustic and thermal energy. In this thesis, computational methods for magnetic forces, magnetostriction, mechanical deformations, vibrations, and finally the acoustic sound produced by electrical motors are successfully implemented. The study starts with the analysis of magnetic forces in ferromagnetic materials and electrical motors by crafting finite element methods for computing these forces and validating them with experiments. From there, the investigations proceed to structural mechanics zone, where the effects of magnetic forces and magnetostriction on the deformations and vibrations of electrical steel sheets and the stator core of electrical motors are studied using numerical methods and experimental justifications. The causes of vibrations in two induction motors were examined with computational and experimental methodologies. The generation of acoustic noise due to mechanical vibrations is modeled using a numerical method that is based on a combination of the finite-element and boundary-element methods. The results and findings in the thesis from numerical and experimental studies provide efficient tools for analyzing and computing various quantities pertaining to the behavior of ferromagnetic materials and electrical motors. These methods can be applied in practical facets such as the design and condition-monitoring stages of electrical motors. This thesis has succeeded in addressing different domains of energy conversions and their effects in electrical machines by developing reliable and proficient computational tools and experimental methods in the realms of magnetics, mechanics and acoustics.
A New Paired Associative Stimulation Protocol with High-Frequency Peripheral Component and High-Intensity 20 Hz Repetitive Transcranial Magnetic Stimulation - A Pilot Study
(2021-11-01) Sathyan, Sabin; Tolmacheva, Aleksandra; Tugin, Sergei; Mäkelä, Jyrki P.; Shulga, Anastasia; Lioumis, Pantelis
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Paired associative stimulation (PAS) is a stimulation technique combining transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS) that can induce plastic changes in the human motor system. A PAS protocol consisting of a high-intensity single TMS pulse given at 100% of stimulator output (SO) and high-frequency 100-Hz PNS train, or “the high-PAS” was designed to promote corticomotoneuronal synapses. Such PAS, applied as a long-term intervention, has demonstrated therapeutic efficacy in spinal cord injury (SCI) patients. Adding a second TMS pulse, however, rendered this protocol inhibitory. The current study sought for more effective PAS parameters. Here, we added a third TMS pulse, i.e., a 20-Hz rTMS (three pulses at 96% SO) combined with high-frequency PNS (six pulses at 100 Hz). We examined the ability of the proposed stimulation paradigm to induce the potentiation of motor-evoked potentials (MEPs) in five human subjects and described the safety and tolerability of the new protocol in these subjects. In this study, rTMS alone was used as a control. In addition, we compared the efficacy of the new protocol in five subjects with two PAS protocols consisting of PNS trains of six pulses at 100 Hz combined with (a) single 100% SO TMS pulses (high-PAS) and (b) a 20-Hz rTMS at a lower intensity (three pulses at 120% RMT). The MEPs were measured immediately after, and 30 and 60 min after the stimulation. Although at 0 and 30 min there was no significant difference in the induced MEP potentiation between the new PAS protocol and the rTMS control, the MEP potentiation remained significantly higher at 60 min after the new PAS than after rTMS alone. At 60 min, the new protocol was also more effective than the two other PAS protocols. The new protocol caused strong involuntary twitches in three subjects and, therefore, its further characterization is needed before introducing it for clinical research. Additionally, its mechanism plausibly differs from PAS with high-frequency PNS that has been used in SCI patients.
Synchronous Reluctance Motor for Household Applications
(2013-05-20) Sathyan, Sabin
Sähkötekniikan korkeakoulu | Master's thesis
This thesis has been done in the Electromechanics group of Department of Electrical Engineering, Aalto University as part of the motor design and electromechanics research. The project is centered on the design of synchronous reluctance motors and study on how this motor can be used for household applications. The design and simulation were carried out by using extensive finite element analysis with FCSMEK developed in the Helsinki University of Technology. The purpose was to create a motor with cheaper cost and having good performance parameters. The main concentration in the work was on the design part, especially the rotor design, as minute design elements have considerable effect on the performance of the motor. The optimization process of the rotor design has given results on the effect of some geometrical parameters in the motor design technology. A 300 W motor is designed and a thermal model was prepared using Lumped Thermal Networking method. The motor has good efficiency and low losses with good torque characteristics. A study on the comparison of the synchronous reluctance motor with induction motor has been done in order to justify the performance of the motor and the feasibility of using this type of motor for household applications.