Soft-start Research Articles

Soft-Starting Method Analysis of Belt Conveyor

This paper introduces several methods of soft start of belt conveyor, Through the analysis of all kinds of soft start mode, the prospects of development of soft start device of belt conveyor, and through the comparison of several commonly used start speed curve, the reasonable start speed curve, pointed out the direction for the research of soft start device of belt conveyor.

A Remote and Sensorless Stator Winding Temperature Estimation Method for Thermal Protection for Induction Motor

Three-phase induction motors are the “workhorses” of industry; they are the most widely used electrical machine; because of its simple structure and high reliability. This paper proposes a new technique to model the stator winding of the induction motor in Matlab Simulink® software. This simulation of the induction motor would have the thermal behavior of its stator winding; to study the induction motor temperature estimation using motor parameter-based method. The modified model is used to validate a remote and Sensorless stator winding temperature estimation technique; therefore a thermal protection is obtained for soft-starter-connected to induction motors. The soft-starter is used to inject a DC signal in the induction motor terminal voltage and current. The stator winding resistance/temperature is estimated from DC signal injection by changing the gate drive signals of the Thyristor in the soft starter. The level of the injected DC signal is adjusted by the value of the delay angle. The accuracy of stator winding temperature estimation increased with the increase of DC signal level; however the pulsation of the output torque increased also. The thermal behavior is simulated utilizing a thermal resistor block from the Matlab Simscape™ software. It is used to replace the fixed resistor value of the induction motor model in the Matlab Simulink. The thermal monitoring scheme has been validated from the simulation results of a 7.5 kW induction motor under various loading conditions.

The Evaluation of Teaching Quality Based on Fuzzy Method

For the problems that the street running state and information was difficult to feedback and reasonable control, we apply the topology model to the street lighting management system, and complete the optimization control in this paper. Using the fuzzy control theory to handle the road signals, the intelligent lighting region controller integrates the thyristor chopper with the autotransformer technology, carries out the soft start and slow slope control to the street light, and realizes automatic voltage and energy saving. At finally, the system can realize the energy-saving control and intelligent, networked management of city street lamp.

Modeling and Simulation of Motor Discrete Variable Frequency Soft Starting Based on the Variable Reactance

The started motors are characterized by the low staring torque and large currents when the motors draw the heavy-loads. Therefore, a method of motor discrete variable frequency soft starting based on the variable reactance is presented in this paper [1,2]. According to the topological structure and working principle of motor discrete variable frequency soft starting based on the variable reactance, the simulation model of the system has been set up by the Matlab/Simulink tool. Simulation results show that the motor starters developed with this method have been successfully applied to the loads of the drive equipment in the kiln, coal grinding mill or the mine. It can improve the starting performance when the motors draw the heavy-loads., save energy, stabilize the voltage of the power supply network.

Comparison of Different Tapped Windings for Flux Adjustment in Induction Motors

In single-speed three-phase squirrel-cage induction motors with rated power above 3 kW, although the use of electronic soft-starters is increasing fast, the conventional star-delta starters are still the most used, requiring three contactors. In this paper, motor soft starting and/or magnetizing flux adjustment solutions based on two-flux-level, delta- and star-connected, tapped windings are proposed, providing an alternative to the conventional star/delta windings. The motor flux adjustment in the proposed tapped winding is based on the change of the winding factor and/or per-phase number of turns. The connection-mode change system for the proposed tapped windings requires only two contactors, and no extra cost is expected for the motor manufacturing or rewinding. For the proposed tapped winding arrangements, a theoretical analysis is made, and simulated and experimental results are presented. The presented solutions can be used to improve the part-load efficiency and power factor of fixed-speed variable-load motors, particularly if they operate long periods with load lower than 35%–45% and short periods with load close to 100%, and an automatic load-based winding connection-mode management system is used.

Effect of Three Light Curing Protocols and Load Cycling on Microleakage of Class V Composite Restorations

Objective: Different methods have been suggested to overcome the polymerization shrinkage of composite restorations. Changing the light curing protocol to improve polymerization by using new light curing units is among these methods. The new devices are more efficient, portable and durable and produce less heat. This study aimed to assess the marginal microleakage of class V composite restorations subjected to three different light curing protocols and mechanical cycles.Methods: This was an in-vitro experimental study. Class V cavities measuring 2x3x1.5 mm were prepared on the buccal and lingual surfaces of 90 extracted human premolar teeth 1.5 mm above and below the cement enamel junction (CEJ). The samples were selected using convenience sampling and divided into 9 experimental groups of 10 each by using the Table of Random Numbers to control for the bias. The cavities were restored with packable composite resin along with Tetric-N- Bond and cured using three light curing protocols of conventional (680 mW/cm2 for 30s), soft-start (380 mW/cm2 for 10s followed by 680 mW/cm2 for 20s) and pulse (680 mW/cm2 for 30s,1s interval and 1s of lighting). The teeth were then subjected to mechanical cycles of 0, 500,000 and 1,000,000 and immersed in 2% Fuchsin for 24h. The teeth were then sectioned in half from the middle of the restoration buccolingually and the degree of microleakage was evaluated under a stereomicroscope (Zeiss, Germany) with 40X magnification. Data were analyzed using the Kruskal Wallis and the Mann-Whitney tests.Results: Despite the structural differences between the enamel and dentin margins, no significant difference was found in the degree of microleakage between the enamel (occlusal wall, p>0.05) and dentin (gingival wall, p>0.05) margins among the understudy groups.Conclusion: The degree of marginal microleakage in soft-start (SS) polymerization was not significantly different from that in conventional and pulse polymerizations of class V composite restorations

Photoinitiator concentration and modulated photoactivation: influence on polymerization characteristics of experimental composites

Abstract This study determined the influence of photoinitiator concentration on polymerization characteristics of experimental composites photoactivated by different methods. Composites based on BisGMA/TEGDMA and 65% of filler were prepared with the concentration of camphorquinone/amine C1-0.5%, C2-1%, C3-1.5%, and photocured using 4 methods: High-intensity (HI), Low-intensity (LI), Soft-start (SS) and Pulse-delay (PD). Were determined the degree of conversion (DC), depth of cure (DCure) and crosslink density (CLD). Data were submitted to ANOVA and Tukey’s test (p < 0.05). DC and DCure revealed that there were no differences among the photoactivation methods. C3 and C2 showed higher DC than C1. The CLD evaluation revealed considerable differences among the photoactivation methods. Photoinitiator concentration is a determinant factor in the polymerization characteristics of composites. Composite with low photoinitiator concentration show decreased DC and DCure, when compared with the composites with higher concentrations. Photoactivation methods had no effect on the DC and DCure. However, photoactivation methods showed differences when CLD was tested for composites with higher concentration of photoinitiators.

Analysis of the Soft-Start Circuit of the High Voltage Power Supply Based on PSM Technology

The power supply based on pulse step modulation technology has been widely used as the high-voltage power supply (HVPS) for additional heating systems. The topology contains numbers of converters and multisecondary transformers. For the magnetizing inrush of the transformer and charging current of the converters connecting with the secondary windings of transformer, the power up of the power supply system is quite complex. There are resistor branches series with the transformer and each converter is used to limit the inrush current. A lot of resister branches and parallel contactors in the converter modules are required, and as a result the dissipation and electromagnetic interference inside the module are serious. In this paper, the soft-start circuit is simplified to only one resistor branch. The precharge circuits of the converters, which are connected to the secondary, are diverted from the inside of the modules to the primary winding of transformer. Since the multisecondary transformer powers up at the same time as converters, the capacitors in all converters will limit the ramp up rate of the transformer voltage, and the magnetic inrush current can be ignored. To analyze the characters of the precharge branches, all converters can be equaled as parallel during the soft-start process. The equivalent circuit, a series RLC circuit, is proposed in this paper. A 1.2-kV power supply, contains 12 converters, with soft start has been built up in laboratory. Simulation and experiment results are shown to verify the theoretical analysis. A new soft-start circuit of 100-kV HVPS system was designed.

A Kind of Discrete Variable Frequency Heavy-Load Soft Start System

A kind of discrete variable frequency heavy-load soft start system was designed in order to realize heavy-load soft starting of motor. It consisted of variable reactance converter, discrete variable frequency converter and controller. The system structure was described in detail and the principle of discrete variable frequency heavy-load soft starting was analyzed. Also the model of the system was made and simulation of the system was done. The simulation results proved that the system can not only start motor smoothly, but also increase the motor start torque greatly, thus heavy load soft-starting of motor can be realized perfectly. In addition, the experiment of the system was done. The experiment results proved that the simulation was correct and the designed discrete variable frequency heavy-load soft start system can realize heavy-load soft start of motor. DOI : http://dx.doi.org/10.11591/telkomnika.v12i4.4930

Design of Asynchronous Motor Soft Starting and Saving Energy Control Based on PLC

For Asynchronous motor starting current impact is large, efficiency of running at light load is low. An energy-saving controller was designed with the PLC (Programmable Controller) as the core. It could realize the soft start and the energy saving control of motor when motor light run. The experimental results showed that: the energy-saving controller had the characteristics of stable starting, flexible parameter adjustment, energy saving effect obviously when motor light run. DOI : http://dx.doi.org/10.11591/telkomnika.v12i3.4540 Full Text: PDF

Study on Delay Synchronizing Rectification Control Method of Bi-Directional DC-DC Converter for Photovoltaic System

A novel photovoltaic (PV) system is proposed, which exhibits the advantages of better protection and more efficient control on charge/discharge of the battery. Furthermore, it can realize power management of the system. The key point of power management is how to control the bi-directional converter effectively. Considering traditional soft start strategy would be ineffective for bi-directional converter in the double sources application for the possibility of damaging the power device, a new soft start control method named delay synchronizing rectification control method is proposed. A 500W prototype converter is built to verify the theoretical analysis and the control method.

Based on PLC Control of Double Constant Pressure No Tower Water Supply System Design

In view of the traditional double motor constant pressure water supply system without tower in the operation process of the problem of short service life, the design of a new type of dual voltage no tower water supply control system. The control system uses PLC, soft starter and frequency converter technology, the soft starter can make the motor to realize soft start and soft stop, no impact on the motor, can extend the service life of the motor, avoid pumping station "door" damage, reduce repair costs and repair work. The running results show that, after the reformation of water supply system can save more than 21% energy, but also improve the quality and reliability of the water supply.

Optimal planning of soft starter for large drain motor based on simulated annealing method

AbstractThis paper proposes the optimal planning of soft starter characteristics for a large drain motor based on simulated annealing (SA). First, the planning of the soft starter characteristics is formulated as an optimization problem with minimal motor starting time; then, the constraints of the motor starting energy, power quality requirements, and minimal cost of transmission line are constructed. The system framework of an actual case in Taiwan is used as the basis of this study with simulation. Before and after the installation of three sets of soft starters, measuring instruments are used in the field to investigate the changes of current and voltage during the motor starting, thus establishing the database of current swell and voltage sag. The searching algorithm based on the SA method is developed by the program MATLAB, such that the soft starter can regulate the minimal motor starting time and meet the above‐mentioned constraints. According to the model of the system circuit and the characteristic parameters constructed by an actual case, the simulation results verify the superiority of the proposed SA method. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

High Torque Low Current Starter System for Synchronous Motor

High Torque Low Current (HTLC) Starter is the new innovative motor soft starter system. This is a motor starting method for high inertia loads using a low voltage drive with input and output transformers to control motor torque and limit current when starting a medium/high voltage motor. The HTLC is a solution to motor starting problems where Direct on Line (DOL) or “Across the Line” starting is not feasible due to high in-rush current causing problems on the distribution system or where a reduced voltage starter cannot provide enough torque to achieve breakaway and accelerate the motor to full speed. The main features of HTLC starter system are reduction of starting inrush current from 600% to 10% and over 60% breakaway torque available during starting, significantly less costly than a fully rated VFD and multiple motors can be started from a single HTLC. This innovative motor soft starter system used in BPCL-Kochi Refinery for starting of 6MW Synchronous motor.

Evaluation of the Influence of Three Types of Light Curing Systems On Temperature Rise, Depth of Cure and Degree of Conversion of Three Resin Based Composites (An In vitro study)

Aim of study: The purpose of this study was to evaluate the effect of Quartz tungsten halogen, Light emitted diode & soft start light curing units on temperature rise, depth of cure & degree of conversion of different types of dental composites (Spectrum, Esthet X & Z250). Methodology: Thirty sound, single–rooted human bicuspids extracted for orthodontic purpose were used to measure the temperature rise inside the pulp chamber by using a needle probe, connected to thermocouple thermometer through the apical foramen. Ninety specimens of dental composites (Spectrum, Esthet X & Z250) were prepared by using special mold to determine the depth of cure of different light curing modes (Quartz tungsten halogen, Light emitted diode & soft start) by using the scraping method described by ISO standard for polymer –based filling restorative & luting materials. For the assessment of the degree of conversion, eighteen samples of dental composites were tested by the Fourier – transformed infrared spectrometry according to the standard baseline technique of Rueggeberg et al., 1990. Result and Conclusion: QTH light curing showed the highest temperature rise value, while the soft start gave the lowest values. Soft start light curing revealed the highest depth of cure values, while the QTH showed the lowest values among three curing modes. There were overall statistical significant differences in the depth of cure values among groups of different curing systems & types of dental composites. Soft start light curing system showed the highest degree of conversion and QTH had the lowest values. Esthet X dental composite gave the highest results of the degree of conversion while Z250 showed the lowest values.

Motor soft starters in electric drives used in mining machinery

This paper analyzes the selection of the type of a starter for electric drives with high-voltage synchronous motors depending on the nature of the change in the load torque of the mechanism, the amount of driving synchronous motors to be started up (single motor or successive start of several motors), and the technological regime requirements, as well as the parameters of the synchronous motor. Single-line schemes of implementing the soft starters of driving high-voltage synchronous motors of large grinding machines and axial mine fans for main and auxiliary ventilation are given.

Motor Drive Control Based on Microcontroller and PID

This paper describes the incremental PID control algorithm and the basic principles of motor soft start, and introduced STM32F103RB8 basic performance microcontroller, combined with incremental PID control advantages, and gives MCU in motor soft start process control application. Practice shows that the incremental PID applications, simplifying the control ideas to improve the performance of the current loop control, limiting the starting current, smooth start-up speed, and achieved good results motor start.

Transient Stability Analysis during an Improved Coupling Procedure for an Induction Generator Based Wind Generation System to the Grid

For fixed speed wind turbines, the connection of its squirrel cage induction generator (SCIG) to the grid leads to inrush current which can reach an average of 2 p.u. up to 2.5 p.u. in higher wind speed even by using a soft starter. We propose in this paper a new soft starting of squirrel cage induction generator based wind turbine connected to the grid. Our strategy overcomes such transient instability problems and pinpoints rapidly synchronous speed regardless the wind speed acting on pitch angle. The proposed strategy ensures at least 50% reduction of inrush current and 18% gain of WTG starting time. A state model of the system is given including the wind turbine model and the SCIG model in the synchronous reference frame. Simulation results are analysed and compared to the classic coupling procedure.

Marginal seal of direct composite veneers

Introduction. Advance in new nano-composite materials and adhesive systems has provided stronger bond with hard dental tissue as well as possibility for minimal cavity preparation. The aim of this study was to evaluate, using dye method, marginal seal of direct composite veneers placed on intact and abraded anterior teeth and polymerized with classical and soft start light curing technique. Material and Methods. The study was conducted on 40 extracted human anterior teeth. They were extracted for periodontal reasons and divided into two groups: intact teeth (20) and abraded teeth (20). 10 teeth in each group were polymerized with classical and soft start technique. Dye penetration was measured using stereo loupes with micrometer scale and six times magnification. Results. Linear dye penetration on the gingival wall when direct composite veneers were placed in intact teeth and polymerized with classical technique was 2.50 ?m, while on the incisal wall it was 0.5 ?m. Linear dye penetration on the gingival wall in intact teeth polymerized with soft start technique was 2.25 ?m, while on the incisal wall it was 2.0 ?m. Average dye penetration of direct composite veneers in abraded teeth polymerized with classical technique on the gingival wall was 3.0 ?m while on the incisal wall it was 1.25 ?m. Linear dye penetration in abraded teeth polymerized with soft start technique was greater on the gingival wall (3.50 ?m) than on the incisal wall (3.25 ?m). Conclusion. Smaller microcrack was observed on the incisal wall than on the gingival wall in all teeth regardless of the technique of polymerization used. The least dye penetration was observed in the group of intact teeth polymerized with classical technique of polymerization.

Comparative Evaluation of the Effects of Light Intensities and Curing Cycles of QTH, and LED Lights on Microleakage of Class V Composite Restorations.

The purpose of this study was to evaluate the effects of light intensity and curing cycles of QTH and LED lights on the microleakage of Class V composite restorations. Eighty freshly extracted human maxillary premolars were used for this study. Standardized Class V cavities were prepared and they were restored with microhybrid resin composite. According to the curing protocol, the teeth were then divided into 4 groups (n=20): QTH curing (standard and soft start modes), and LED (standard and soft start modes) irradiations. Microleakage was evaluated by immersion of the samples in 50% silver nitrate solution. The samples were then sectioned, evaluated under a stereomicroscope, and scored for microleakage. The results of the present in-vitro study showed mean dye leakage scores of 1.9, 1.2, 1.45 and 0.90 for Group I (QTH-Standard mode), Group II (QTH-Soft Start mode), Group III (LED-Standard mode) and Group IV (LED-Soft Start mode) respectively. It was thus concluded that the soft start polymerization showed a highly significant difference as compared to the standard curing modes of QTH and LED lights, respectively.