A Comparison of Induction Motor Starting Methods Being Powered by a Diesel-Generator Set

Starting induction motors on isolated or weak systems is a highly dynamic process that can cause motor and load damage as well as electrical network fluctuations. Mechanical damage is associated with the high starting current drawn by a ramping induction motor. In order to compensate the load increase, the voltage of the electrical system decreases. Different starting methods can be applied to the electrical system to reduce these and other starting method issues. The purpose of this thesis is to build accurate and usable simulation models that can aid the designer in making the choice of an appropriate motor starting method. The specific case addressed is the situation where a diesel-generator set is used as the electrical supplied source to the induction motor. The most commonly used starting methods equivalent models are simulated and compared to each other. The main contributions of this thesis is that motor dynamic impedance is continuously calculated and fed back to the generator model to simulate the coupling of the electrical system. The comparative analysis given by the simulations has shown reasonably similar characteristics to other comparative studies. The diesel-generator and induction motor simulations have shown good results, and can adequately demonstrate the dynamics for testing and comparing the starting methods. Further work is suggested to refine the equivalent impedance presented in this thesis.

Freio eletrodinamométrico usando um inversor de frequência e um motor de indução trifásico

Considering that the Brazilian energy source is based on hydroelectric power plants, every moment that it does not rain enough, we are likely to suffer power outage. Making the rational use of energy not only is wise, but also important for financial issues. The industrial sector is of great importance to Brazilian economic context, because it is one that creates more wealth and jobs. It should be noted that it is one of the sectors that consume more electricity. One of the most used equipment in industry is the three phase induction motor, which ends up providing significant waste of energy. For that reasons, studying three phase induction motors is important. One of the ways to evaluate the parameter of the three phase induction motor is using a dynamometer mechanic or electric. This work aims at further studies (and development) of electrodynamometer brake, a type of electrical dynamometer, that is the only one with reversible use. This means, it is possible to measure both the torque and the power transmitted by the electric motors, by the direct method and the indirect. Besides it allows greater stability in the imposition of charges, due to its nature of being able to regenerate the energy imparted by the engines being tested

Cognitive, Mood, and Electroencephalographic Effects of Noninvasive Cortical Stimulation With Weak Electrical Currents

Objectives: The use of noninvasive cortical electrical stimulation with weak currents has significantly increased in basic and clinical human studies. Initial, preliminary studies with this technique have shown encouraging results; however, the safety and tolerability of this method of brain stimulation have not been sufficiently explored yet. The purpose of our study was to assess the effects of direct current (DC) and alternating current (AC) stimulation at different intensities in order to measure their effects on cognition, mood, and electroencephalogram. Methods: Eighty-two healthy, right-handed subjects received active and sham stimulation in a randomized order. We conducted 164 ninety-minute sessions of electrical stimulation in 4 different protocols to assess safety of (1) anodal DC of the dorsolateral prefrontal cortex (DLPFC); (2) cathodal DC of the DLPFC; (3) intermittent anodal DC of the DLPFC and; (4) AC on the zygomatic process. We used weak currents of 1 to 2 mA (for DC experiments) or 0.1 to 0.2 mA (for AC experiment). Results: We found no significant changes in electroencephalogram, cognition, mood, and pain between groups and a low prevalence of mild adverse effects (0.11% and 0.08% in the active and sham stimulation groups, respectively), mainly, sleepiness and mild headache that were equally distributed between groups. Conclusions: Here, we show no neurophysiological or behavioral signs that transcranial DC stimulation or AC stimulation with weak currents induce deleterious changes when comparing active and sham groups. This study provides therefore additional information for researchers and ethics committees, adding important results to the safety pool of studies assessing the effects of cortical stimulation using weak electrical currents. Further studies in patients with neuropsychiatric disorders are warranted.

Imperceptible electrical noise attenuates isometric plantar flexion force fluctuations with correlated reductions in postural sway

Optimal levels of noise stimulation have been shown to enhance the detection and transmission of neural signals thereby improving the performance of sensory and motor systems. The first series of experiments in the present study aimed to investigate whether subsensory electrical noise stimulation applied over the triceps surae (TS) in seated subjects decreases torque variability during a force-matching task of isometric plantar flexion and whether the same electrical noise stimulation decreases postural sway during quiet stance. Correlation tests were applied to investigate whether the noise-induced postural sway decrease is linearly predicted by the noise-induced torque variability decrease. A second series of experiments was conducted to investigate whether there are differences in torque variability between conditions in which the subsensory electrical noise is applied only to the TS, only to the tibialis anterior (TA) and to both TS and TA, during the force-matching task with seated subjects. Noise stimulation applied over the TS muscles caused a significant reduction in force variability during the maintained isometric force paradigm and also decreased postural oscillations during quiet stance. Moreover, there was a significant correlation between the reduction in force fluctuation and the decrease in postural sway with the electrical noise stimulation. This last result indicates that changes in plantar flexion force variability in response to a given subsensory random stimulation of the TS may provide an estimate of the variations in postural sway caused by the same subsensory stimulation of the TS. We suggest that the decreases in force variability and postural sway found here are due to stochastic resonance that causes an improved transmission of proprioceptive information. In the second series of experiments, the reduction in force variability found when noise was applied to the TA muscle alone did not reach statistical significance, suggesting that TS proprioception gives a better feedback to reduce force fluctuation in isometric plantar flexion conditions.

Comparison between the C5 or C6-Cz electrode assembly and C3 or C4-Cz assembly for transcranial electric motor activation of muscular response of the contralateral facial nerve

We used an assembly of electrodes C3 and C4-Cz in order to activate the motor cortical area of the corticobulbar tract to elucidate the motor-evoked potential of the contralateral mentalis muscle. We compared this setup to that of an assembly with electrodes C5 or C6-Cz using a train of electrical pulses and a single electrical pulse. This analysis was made in 23 consecutive patients who underwent several varied surgeries and were prospectively operated on at Santa Paula Hospital between January and June 2011. The results showed that the assembly with C5 or C6-Cz produced a multisynaptic motor-evoked potential in the contralateral mentalis muscle in 86.9 % of the patients, whereas 82.6 % of patients stimulated at points C3 or C4-Cz presented the same response. However, both assemblies showed similar behavior with the use of a single electrical pulse for peripheral contralateral nerve stimulation. We concluded that the C5 or C6-Cz assembly was similar to C3 or C4-Cz in obtaining a multisynaptic response in the contralateral mentalis muscle, although it required less intensive stimulation than the C3 or C4- Cz assembly.

Bat-Inspired Optimization Approach for the Brushless DC Wheel Motor Problem

This paper presents a metaheuristic algorithm inspired in evolutionary computation and swarm intelligence concepts and fundamentals of echolocation of micro bats. The aim is to optimize the mono and multiobjective optimization problems related to the brushless DC wheel motor problems, which has 5 design parameters and 6 constraints for the mono-objective problem and 2 objectives, 5 design parameters, and 5 constraints for multiobjective version. Furthermore, results are compared with other optimization approaches proposed in the recent literature, showing the feasibility of this newly introduced technique to high nonlinear problems in electromagnetics.

Motor cortex stimulation inhibits thalamic sensory neurons and enhances activity of PAG neurons: Possible pathways for antinociception

Motor cortex stimulation is generally suggested as a therapy for patients with chronic and refractory neuropathic pain. However, the mechanisms underlying its analgesic effects are still unknown. In a previous study, we demonstrated that cortical stimulation increases the nociceptive threshold of naive conscious rats with opioid participation. In the present study, we investigated the neurocircuitry involved during the antinociception induced by transdural stimulation of motor cortex in naive rats considering that little is known about the relation between motor cortex and analgesia. The neuronal activation patterns were evaluated in the thalamic nuclei and midbrain periaqueductal gray. Neuronal inactivation in response to motor cortex stimulation was detected in thalamic sites both in terms of immunolabeling (Zif268/Fos) and in the neuronal firing rates in ventral posterolateral nuclei and centromedian-parafascicular thalamic complex. This effect was particularly visible for neurons responsive to nociceptive peripheral stimulation. Furthermore, motor cortex stimulation enhanced neuronal firing rate and Fos immunoreactivity in the ipsilateral periaqueductal gray. We have also observed a decreased Zif268, delta-aminobutyric acid (GABA), and glutamic acid decarboxylase expression within the same region, suggesting an inhibition of GABAergic interneurons of the midbrain periaqueductal gray, consequently activating neurons responsible for the descending pain inhibitory control system. Taken together, the present findings suggest that inhibition of thalamic sensory neurons and disinhibition of the neurons in periaqueductal gray are at least in part responsible for the motor cortex stimulation-induced antinociception. (C) 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Speed Neuro-fuzzy Estimator Applied To Sensorless Induction Motor Control

This work proposes the development of an Adaptive Neuro-fuzzy Inference System (ANFIS) estimator applied to speed control in a three-phase induction motor sensorless drive. Usually, ANFIS is used to replace the traditional PI controller in induction motor drives. The evaluation of the estimation capability of the ANFIS in a sensorless drive is one of the contributions of this work. The ANFIS speed estimator is validated in a magnetizing flux oriented control scheme, consisting in one more contribution. As an open-loop estimator, it is applied to moderate performance drives and it is not the proposal of this work to solve the low and zero speed estimation problems. Simulations to evaluate the performance of the estimator considering the vector drive system were done from the Matlab/Simulink(R) software. To determine the benefits of the proposed model, a practical system was implemented using a voltage source inverter (VSI) to drive the motor and the vector control including the ANFIS estimator, which is carried out by the Real Time Toolbox from Matlab/Simulink(R) software and a data acquisition card from National Instruments.

Induction Motor Diagnosis in Variable Speed Drives

Several diagnostic techniques are presented for the detection of electrical fault in induction motor variable speed drives. These techinques are developed taking into account the impact of the control system on machine variables and non stationary operating conditions.

Models for the Study of Cortical Activity During Cognitive ans Motor Tasks

This thesis is mainly devoted to show how EEG data and related phenomena can be reproduced and analyzed using mathematical models of neural masses (NMM). The aim is to describe some of these phenomena, to show in which ways the design of the models architecture is influenced by such phenomena, point out the difficulties of tuning the dozens of parameters of the models in order to reproduce the activity recorded with EEG systems during different kinds of experiments, and suggest some strategies to cope with these problems. In particular the chapters are organized as follows: chapter I gives a brief overview of the aims and issues addressed in the thesis; in chapter II the main characteristics of the cortical column, of the EEG signal and of the neural mass models will be presented, in order to show the relationships that hold between these entities; chapter III describes a study in which a NMM from the literature has been used to assess brain connectivity changes in tetraplegic patients; in chapter IV a modified version of the NMM is presented, which has been developed to overcomes some of the previous version’s intrinsic limitations; chapter V describes a study in which the new NMM has been used to reproduce the electrical activity evoked in the cortex by the transcranial magnetic stimulation (TMS); chapter VI presents some preliminary results obtained in the simulation of the neural rhythms associated with memory recall; finally, some general conclusions are drawn in chapter VII.

Motor control system in Parkinson’s disease: a modeling approach

Parkinson’s disease is a neurodegenerative disorder due to the death of the dopaminergic neurons of the substantia nigra of the basal ganglia. The process that leads to these neural alterations is still unknown. Parkinson’s disease affects most of all the motor sphere, with a wide array of impairment such as bradykinesia, akinesia, tremor, postural instability and singular phenomena such as freezing of gait. Moreover, in the last few years the fact that the degeneration in the basal ganglia circuitry induces not only motor but also cognitive alterations, not necessarily implicating dementia, and that dopamine loss induces also further implications due to dopamine-driven synaptic plasticity got more attention. At the present moment, no neuroprotective treatment is available, and even if dopamine-replacement therapies as well as electrical deep brain stimulation are able to improve the life conditions of the patients, they often present side effects on the long term, and cannot recover the neural loss, which instead continues to advance. In the present thesis both motor and cognitive aspects of Parkinson’s disease and basal ganglia circuitry were investigated, at first focusing on Parkinson’s disease sensory and balance issues by means of a new instrumented method based on inertial sensor to provide further information about postural control and postural strategies used to attain balance, then applying this newly developed approach to assess balance control in mild and severe patients, both ON and OFF levodopa replacement. Given the inability of levodopa to recover balance issues and the new physiological findings than underline the importance in Parkinson’s disease of non-dopaminergic neurotransmitters, it was therefore developed an original computational model focusing on acetylcholine, the most promising neurotransmitter according to physiology, and its role in synaptic plasticity. The rationale of this thesis is that a multidisciplinary approach could gain insight into Parkinson’s disease features still unresolved.

Effect of ketamine on the limb withdrawal reflex evoked by transcutaneous electrical stimulation in ponies anaesthetised with isoflurane

The purpose of this study was to evaluate the anti-nociceptive activity of ketamine and isoflurane in horses using a limb withdrawal reflex (WR) model. Single and repeated stimulations were applied to the digital nerve of the left forelimb in ponies anaesthetised with isoflurane before, during and after intravenous administration of racemic ketamine. Surface electromyographic activity was recorded from the deltoid muscle. Higher stimulation intensity was required to evoke a reflex during ketamine administration. Furthermore, the amplitudes of response to stimulations were significantly and dose-dependently depressed and a flattening of the stimulus-response curves was observed. The reflex activity recovered partially once the ketamine infusion finished. The results demonstrated that the limb WR can be used to quantify the temporal effect of ketamine on the sensory-motor processing in ponies anaesthetised with isoflurane.

Properties of low-threshold motor axons in the human median nerve

This study investigated the excitability and accommodative properties of low-threshold human motor axons to test whether these motor axons have greater expression of the persistent Na(+) conductance, I(NaP). Computer-controlled threshold tracking was used to study 22 single motor units and the data were compared with compound motor potentials of various amplitudes recorded in the same experimental session. Detailed comparisons were made between the single units and compound potentials that were 40% or 5% of maximal amplitude, the former because this is the compound potential size used in most threshold tracking studies of axonal excitability, the latter because this is the compound potential most likely to be composed entirely of motor axons with low thresholds to electrical recruitment. Measurements were made of the strength-duration relationship, threshold electrotonus, current-voltage relationship, recovery cycle and latent addition. The findings did not support a difference in I(NaP). Instead they pointed to greater activity of the hyperpolarization-activated inwardly rectifying current (I(h)) as the basis for low threshold to electrical recruitment in human motor axons. Computer modelling confirmed this finding, with a doubling of the hyperpolarization-activated conductance proving the best single parameter adjustment to fit the experimental data. We suggest that the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel(s) expressed on human motor axons may be active at rest and contribute to resting membrane potential.

The effects of isoflurane minimum alveolar concentration on withdrawal reflex activity evoked by repeated transcutaneous electrical stimulation in ponies

The aim of this study was to quantify the effects of isoflurane at approximately the minimum alveolar concentration (peri-MAC) on the temporal summation (TS) of reflex activity in ponies. TS was evoked by repeated electrical stimulations applied at 5 Hz for 2 s on the digital nerve of the left forelimb of seven ponies. Surface electromyographic activity was recorded from the deltoid and common digital extensor muscles. TS thresholds and amplitude of response to stimulations of increasing intensities were assessed during anaesthesia at 0.85, 0.95 and 1.05 times the individual MAC, and after anaesthesia in standing animals. Under isoflurane anaesthesia, TS thresholds increased significantly in a concentration-dependent fashion and at each isoflurane MAC, the responses increased significantly for increasing stimulation intensities. A concentration-dependent depression of evoked reflexes with a reduction in the slopes of the stimulus-response function was observed for both muscles. The results demonstrated that with this model it is possible to describe and quantify the effects of anaesthetics on spinal sensory-motor processing in ponies.

Subcortical electrostimulation to identify network subserving motor control

Objectives: Recent anatomical-functional studies have transformed our understanding of cerebral motor control away from a hierarchical structure and toward parallel and interconnected specialized circuits. Subcortical electrical stimulation during awake surgery provides a unique opportunity to identify white matter tracts involved in motor control. For the first time, this study reports the findings on motor modulatory responses evoked by subcortical stimulation and investigates the cortico-subcortical connectivity of cerebral motor control. Experimental design: Twenty-one selected patients were operated while awake for frontal, insular, and parietal diffuse low-grade gliomas. Subcortical electrostimulation mapping was used to search for interference with voluntary movements. The corresponding stimulation sites were localized on brain schemas using the anterior and posterior commissures method. Principal observations: Subcortical negative motor responses were evoked in 20/21 patients, whereas acceleration of voluntary movements and positive motor responses were observed in three and five patients, respectively. The majority of the stimulation sites were detected rostral of the corticospinal tract near the vertical anterior-commissural line, and additional sites were seen in the frontal and parietal white matter. Conclusions: The diverse interferences with motor function resulting in inhibition and acceleration imply a modulatory influence of the detected fiber network. The subcortical stimulation sites were distributed veil-like, anterior to the primary motor fibers, suggesting descending pathways originating from premotor areas known for negative motor response characteristics. Further stimulation sites in the parietal white matter as well as in the anterior arm of the internal capsule indicate a large-scale fronto-parietal motor control network. Hum Brain Mapp, 2012. © 2012 Wiley Periodicals, Inc.