Soft-start Research Articles

Load-Bearing Capacity Investigation of Friction Pairs in Hydro-Viscous Drive Based on Fractal Contact Theory

Abstract Hydro-viscous drive has gained extensive application in fans, pumps, belt conveyors, and scraper conveyors for step-less speed regulating, soft starting, and overload protection. In the mixed friction stage, the state of contact and load-bearing capacity are always changing with the pressure of control oil. In order to predict the load-bearing capacity of friction pairs, a description of the frictional and hydrodynamic lubrication states was first made. Oil film’s pressure distribution and load-bearing capacity were analyzed with the average flow model. The fractal contact model of the asperity surface was proposed for simulating mutual contact state and contact load between the asperities. The influences of fractal parameters on the contact performance of friction pairs were conducted. Eventually, test rig of load-bearing capacity was established. As indicated by the experiment, asperity contact area and load-bearing capacity of the asperity contact increase slowly at first and then rapidly with reduced film thickness ratio. Correspondingly, oil film load-bearing capacity progressively reduces. Due to the reduction of film thickness ratio, friction pairs’ load-bearing capacity increases gradually. The load-bearing capacity of friction pairs is affected by the fractal dimension and scale factor. Results of the experiment well conform to the theoretical values, which illustrates that friction pairs’ load-bearing capacity can be accurately predicted and computed using the average flow model and M-B fractal contact model. The calculation offers a theoretical reference to the survey about friction and torque properties of the hydro-viscous drive.

Research on Intelligent Control System of High Power Soft Starter Based on Discrete Frequency Conversion Technology

Thyristor soft starter can effectively solve the three-phase asynchronous motor starting current problem, but its reduced starting current is achieved by reducing the output voltage and inevitably reducing the motor starting torque, it is difficult to use for heavy start of the occasion. A kind of soft starter based on discrete frequency conversion method is designed for the problem that the starting torque is small, the starting current is large, and the overloading cannot start. Based on the analysis of the working principle of the thyristor soft starter, this paper makes a deep research on the soft start control mode and realization method of the discrete frequency conversion without changing the main circuit structure of the original thyristor soft starter. Firstly, the soft starter hardware based on the three-phase anti-parallel thyristor main circuit and the current effective value is calculated by using high-speed A/D. Then, the soft start control strategy based on discrete frequency conversion is analyzed, with a 3kW/380V three-phase asynchronous motor for the test motor, respectively, the motor started a different way to simulate and test.

Technical and economic aspects of the use of soft starters for asynchronous electric drives

The paper presents data on the results of computer-aided mathematical modeling and experimental studies of transient processes accompanying the start of asynchronous electric drives in order to search for the methods that enable the adjustment of a soft starter to achieve minimum oscillation amplitude of the electric motor dynamic momentum in terms of the current characteristic. The indicators of smoothness, applicable to some types of electric drives of turbine mechanisms, are revealed. It is found that the correlation between the maximum value of the starting current of the electric motor and the maximum amplitude of the momentum fluctuation, as well as between the starting time and the maximum amplitude of the momentum fluctuation, is insignificant. The most informative indicator, providing the function of adaptive self-tuning of the soft starter and maximum technical and economic efficiency of its use, is the oscillation of the dynamic momentum during the start-up. It is established that the amplitude of the dynamic momentum fluctuation can be judged by the displacement of the motor housing during start-up, which will require the modernization of the electric drive. The necessity of additionally calculating the implicit components of costs in terms of the costs of entrepreneurial risk when assessing the economic effect from the modernization of asynchronous electric drives using a soft starter is substantiated.

Improved Power Quality Transformerless Single-Stage Bridgeless Converter Based Charger for Light Electric Vehicles

In this article, a bridgeless switched inductor Cuk (BSIC) converter based charger is presented to provide the low-cost and reduced-size charging solution for the light electric vehicles, i.e., LEVs, with enhanced performances at the supply side. Generally, the chargers of LEVs such as E-Rickshaws, E-Bike, and E-Cycle, are equipped with an additional converter to charge the batteries at low voltages (24–72 V). The switched inductor configuration improves the step-down dc voltage gain of the charger with only one stage and also improves the reliability at such low voltages. It is noteworthy that the cost associated with the sensors along with the size of the magnetic components is considerably reduced by operating the charger in discontinuous current mode condition. Moreover, the high-gain transformerless configuration further improves the cost, size, and efficiency of the charger. The effectiveness of the charger is tested on a laboratory prototype, for an 850 W rating with 220 V, 50 Hz nominal supply voltage conditions. The steady state and dynamic behaviors of the charger are analyzed under different operating conditions. Moreover, the behaviors of the charger during the initialization of charging process are analyzed for ensuring the soft starting of the charger. A basic comparison of the presented charger configuration with existing LEVs chargers is presented to highlight its advantages over the existing one.

Research of Motor Soft Start by High Voltage Motor Drive Inverter

The over-current phenomenon of direct starting of high voltage and high power motor is serious bad for the safety of motor. We are usually using motor soft start method when we need to start a motor. There are some motor soft start methods, they can somehow reduce the starting over-current, but they are still having some defects except motor drive inverter. Motor drive inverter can not only realize the purpose of energy saving, but also is an ideal soft start device. We can see a lot of papers about control method research of motor drive inverter, but no paper research on motor soft start by motor drive inverter [1]. This paper focuses on research of motor soft start by motor drive inverter. The optimal frequency range of soft start is obtained through theoretical analysis. The simulation results verify the correctness and feasibility of the theoretical analysis.

Energy saving and application of frequency converters and soft start devices

The questions of the use of frequency converters and soft starters on pumping equipment are considered. The advantages of using frequency converters and soft starters are indicated. Particular attention is paid to the theoretical issues of the use of frequency converters and soft starters. The corresponding graphs of dependence are given. The approximate cost of implementations is indicated.

Recognition method of AC series arc fault characteristics under complicated harmonic conditions

Due to the power quality problems and the use of some nonlinear loads such as soft starters, rectifiers, and frequency converters, the circuit current will contain complicated harmonic components, which may affect the identification accuracy of arc fault. Aiming at the interferences of power supply harmonics and nonlinear load noise, a kind of recognition method based on kernel principal component analysis (KPCA) and firefly algorithm optimized support vector machine (FA-SVM) was proposed. KPCA was used to separate the harmonics and load noise interferences in the voltage and current signals. Kurtosis and skewness of the fifth and sixth principal components were used as arc fault features. The FA-SVM was designed to recognize arc fault. The arc fault experiments were carried out under complicated harmonic conditions. The effectiveness of the presented method was verified by experiments.

Research of ship deck mechanisms electric drives start by the help of soft starters

Research of ship deck mechanisms electric drives start by the help of soft starters

Technique for rational placement of printing unit elements of soft start device

Technique for rational placement of printing unit elements of soft start device

The Necessity of Application of Frequency Electric Drives for Irrigation Systems

The article substantiates the possibility of using frequency drives in agricultural production, shows promising areas of their application, shows the positive qualities of frequency drives, which make it possible to confidently compete with gear drives that are widespread in agriculture. It is indicated that the use of a frequency electric drive can reduce the current and mechanical loads due to soft start. Due to the additional control inputs of the frequency converter, it is possible to synchronize the processes on the load or set the change factors for some values depending on others. For example, to establish the dependence of the speed of the irrigation pumping system on the pressure in the system. The process will be optimized because as the load on the pump increases, the flow will increase. Recommendations are given on the choice of the power of the frequency converter, taking into account the rated currents and voltage of the converter and the motor. Recommendations are given on the choice of the power of the frequency converter, taking into account the rated currents and voltage of the converter and the motor. The advantages of starting and braking electric drives with frequency regulation are shown.

Led lamp driver modelling

Currently, there is an increase in the use and production of energy-saving lamps of various types – fluorescent and LED ones. However, it has been found that the use of technologies that have proven themselves in the creation of luminescent sources for LED light sources is ineffective. The use of traditional secondary optics for LED luminaires makes it difficult to create an effective heat sink from LEDs, while the durability of LEDs significantly depends on the heat sink. Another important issue when designing LED luminaires is choosing the right driver. The power consumption of LEDs from the primary network depends on the efficiency of the driver used. The choice of the type of driver also determines the amount of heat that should be removed from its elements. A significant factor influencing the choice of a driver is also the possibility of its operation in conjunction with a voltage regulator – a dimmer, in order to control the illumination. It is also necessary to take into account the IEC recommendations that require manufacturers to use active power factor correctors for devices with switching power supplies and / or electronic ballast with a power of 20 watts or more. Therefore, there is a task of developing a highly efficient driver for use in LED luminaires. In the process of reviewing modern drivers, a driver based on the LT3799 microcircuit from Linear Technology was selected for further research, which is distinguished by high efficiency, working with a large number of produced LEDs, has a built-in active power factor corrector, and allows the use of dimmers. The inclusion of the driver chip recommended by the manufacturer was applied, with the addition of noise suppressing components. The galvanic isolation of the power supply circuits of the LED matrix is provided. Next, the analysis of the characteristics of the selected circuit design solution is carried out using computer simulation. LTSpice EDA was chosen as a modeling tool, which is distinguished by its versatility, ease of use and high reliability of results in comparison with similar software products. The modes of operation are analyzed depending on the requirements for the pulsation of the emitting matrix, the operation of the power factor corrector, and the suppression of interference into the industrial network from the operation of the source is estimated. Various options for the development of the circuitry implementation of the driver based on the LT3799 microcircuit and the operating modes of the most heavily loaded elements are analyzed: an inductor, a key transistor, a damper circuit, a diode in the power supply circuit of an LED matrix. Optimal values of circuit components and parameters of winding elements were selected. It is shown that due to the operation of the power factor corrector, the shape of the current consumption from a sinusoidal voltage source is also almost sinusoidal, which leads to an almost active nature of the load. The modes of operation of the LED matrix for the nominal supply voltage and for the reduced one (with a dimmer) are considered. Methods of implementation of a soft start of an LED matrix are described. Based on the results of the work, conclusions are drawn that summarize the expediency of using the developed driver for an LED device based on the LT3799 microcircuit.

Analysis of electric drive systems for performance of driving and starting under load

Purpose. Perform an analysis of existing automated control systems of the electric drive and methods of forming the starting torque to determine the compliance of the selected system and method to the requirements for trouble-free mode of start and start of the technological mechanism in difficult conditions or breakaway and start under load..
 Methodology. Comparison of energy performance and capabilities of control systems and methods for the formation of starting torque, mathematical calculations, analysis of the properties of systems and methods in accordance with the requirements of technological operations during the start.
 Findings. To obtain the results of the analysis of the current methods of starting induction motors, autotransformer start was considered, which can significantly reduce the starting current, and also connect a capacitor with a reactance to reduce the current and increase the starting torque; the use of soft start with amplitude-phase control allows you to reduce the starting current and reached the absence of its impulses. The vector-pulse method of controlling the converting device increases the starting torque in the absence of an increase in starting current, such advantages have a quasi-frequency starting mode, but the application is limited by special technological equipment. Thyristor voltage regulator using the phase control method, despite its widespread use in control systems, has a low value of the starting torque. To carry out starting in difficult conditions, according to the results of the analysis of existing systems of controlled starting, it was found that a rational electric drive system for hoisting-and-transport mechanisms is a frequency-controlled electric drive system according to the "frequency converter - asynchronous motor" (FC - IM) scheme.
 Originality. For the first time it is proposed to improve the existing control systems of hoisting and transport mechanisms that perform start-up in difficult conditions when using the modes of movement to form the starting torque that exceeds the passport value by 3-4 times. Increasing energy efficiency based on increasing their efficiency, information content and data reliability. For the first time, the reasons for the shortcomings of existing control systems during start-up under load in modern production are analyzed.
 Practical value. The choice of a rational electric drive system for lifting and transport mechanisms is substantiated when starting in difficult conditions, which will provide maximum efforts in the transmission of a technological mechanism with permissible current and thermal overloads of asynchronous machines.

RETRACTED: Intelligent control for new topological structure of Z-Source inverter based on ARM

Due to the defects of Z-source inverter topology, an intelligent method to control topological structure of Z-source inverter based on ARM was put forward. Firstly, the double Z-source networks were connected in series, and then new topology structure of the series double Z-source inverter was designed. The steady-state working principle of the new topology structure was analyzed. Based on the steady-state working principle, ArmCortex-m3 processor and digital single-cycle control strategy were used to control the straight-through duty ratio, so that the soft start control and the intelligent control of Z-source inverter topology were realized. Simulation results show that the ratio between capacitor voltage and input voltage is low when the straight-through duty ratio is small. When the command value of DC-link voltage is 50 V, its command voltage value can be accurately tracked. Therefore, the proposed method has high control performance.

A Proposed ANN-Based Acceleration Control Scheme for Soft Starting Induction Motor

In this article, a new soft starting control scheme based on an artificial neural network (ANN) is presented for a three-phase induction motor (IM) drive system. The main task of the control scheme is to keep the accelerating torque constant at a level based on the value of reference acceleration. This is accomplished by the proper choice of the firing angles of thyristors in the soft starter. Using the ANN approach, the complexity of the online determination of the thyristors firing angles is resolved. The IM torque-speed characteristic curves are firstly used to train the ANN model. Secondly, the IM- soft starter system is modeled using MATLAB/SIMULINK. To prove the effectiveness of the proposed ANN-based acceleration control scheme, different reference accelerations and loading conditions are applied and investigated. Finally, a laboratory prototype of 3 kW soft starter is implemented. The proposed control scheme is executed in a real-time environment using a digital signal processor (Model: TMS320F28335). The simulation and real-time results significantly confirm that the proposed controller can efficiently reduce the IM starting current and torque pulsations. This in turn ensures a smooth acceleration of the IM during the starting process. Moreover, the proposed control scheme has the superiority over several soft starting control schemes since it has a simple control circuit configuration, less required sensors, and low computational burden of the control algorithm.

FPGA Based Speed Control of Three-Phase Induction Motor Using Stator Voltage Regulator(dEPT.e)

In this paper a digital speed control strategy for three-phase induction motor is implemented. This strategy depends on varying the stator voltage to control the speed of the induction motor. The system consists of six bidirectional switches. The digital control strategy uses saw-tooth waveform with (wice the supply frequency as a control signal to be compared with triangular waveform as a carrier signal. The voltage output from a voltage regulator can be controlled by varying the voltage level of saw-tooth waveform The control strategy provides also soft starting for the induction motor, The soft starting is implemented by starting the motor in low value of modulation index and increasing it gradually during the starting period. The simulation of the system is carried out by a PSIM computer program. The control strategy is implemented by using FPGA. A detailed digital design of the control system has been introduced in detail. The simulation results have been compared with the experimental results from laboratory prototypes. The simulation and experimental results show stable operation for a wide range of speed control. The levels of harmonics in the supply and motor currents and power factor have been evaluated for different operating conditions.

A Novel Two-phase Soft Starter Used for Three-phase Asynchronous Motors

Background: Traditional thyristor-based three-phase soft starters of induction motor often suffer from high starting current and heavy harmonics. Moreover, both the trigger pulse generation and driving circuit design are usually complicated. Methods: To address these issues, we propose a novel soft starter structure using fully controlled IGBTs in this paper. Compared to approaches of traditional design, this structure only uses twophase as the input, and each phase is controlled by a power module that is composed of one IGBT and four diodes. Results: Consequently, both driving circuit and control design are greatly simplified due to the requirement of fewer controlled power semiconductor switches, which leads to the reduction of the total cost. Conclusion: Both Matlab/Simulink simulation results and experimental results on a prototype demonstrate that the proposed soft starter can achieve better performances than traditional thyristorbased soft starters for Starting Current (RMS) and harmonics.

RESEARCH OF DYNAMIC AND ENERGY PROCESSES OF BELT CONVEYORS UNDER CONTROL WITH SOFT STARTER

In the article an approach to improvement of the belt conveyor performance at the stage of its srart-up has been developed. It was achieved by developing a mathematical model of the conveyor movement under control from the soft starter (the work takes into account the equation of the dynamics of the movement of the mechanical part of the conveyor and the equations of the asynchronous electric drive, which is supplied by the soft starter). The parameters of the soft starter have been determined, which have the strong impact on the dynamic and energy performance of the conveyor. By carrying out numerical experiments, a data array was obtained that connects the settings of the soft starter (the duration of the supply voltage rise and the initial drive supply voltage) with the values of the estimated dynamic and energy performance of the conveyor. Estimates reflected RMS and maximum values. The analysis made it possible to obtain rational values of the optional parameters of the soft starter, at which the dynamic loads and energy losses significantly decreased.

Balancing risks of injury and disturbance to marine mammals when pile driving at offshore windfarms

Abstract1. Offshore windfarms require construction procedures that minimize impacts on protected marine mammals. Uncertainty over the efficacy of existing guidelines for mitigating near‐field injury when pile‐driving recently resulted in the development of alternative measures, which integrated the routine deployment of acoustic deterrent devices (ADD) into engineering installation procedures without prior monitoring by marine mammal observers.2. We conducted research around the installation of jacket foundations at the UK's first deep‐water offshore windfarm to address data gaps identified by regulators when consenting this new approach. Specifically, we aimed to (a) measure the relationship between noise levels and hammer energy to inform assessments of near‐field injury zones and (b) assess the efficacy of ADDs to disperse harbour porpoises from these zones.3. Distance from piling vessel had the biggest influence on received noise levels but, unexpectedly, received levels at any given distance were highest at low hammer energies. Modelling highlighted that this was because noise from pin pile installations was dominated by the strong negative relationship with pile penetration depth with only a weak positive relationship with hammer energy.4. Acoustic detections of porpoises along a gradient of ADD exposure decreased in the 3‐h following a 15‐min ADD playback, with a 50% probability of response within 21.7 km. The minimum time to the first porpoise detection after playbacks was > 2 h for sites within 1 km of the playback.5. Our data suggest that the current regulatory focus on maximum hammer energies needs review, and future assessments of noise exposure should also consider foundation type. Despite higher piling noise levels than predicted, responses to ADD playback suggest mitigation was sufficiently conservative. Conversely, strong responses of porpoises to ADDs resulted in far‐field disturbance beyond that required to mitigate injury. We recommend that risks to marine mammals can be further minimized by (1) optimizing ADD source signals and/or deployment schedules to minimize broad‐scale disturbance; (2) minimizing initial hammer energies when received noise levels were highest; (3) extending the initial phase of soft start with minimum hammer energies and low blow rates.

A Novel DC-DC Converter Based Closed Loop Control of BLDC Motor for SPV fed Water Pumping System

This Paper Presents Novel DC-DC Converter Based Closed Loop Control of BLDC Motor for SPV fed Water Pumping System Solar Photovoltaic (SPV) Array fed Water pumping System Utilizing Buck-boost DC-DC Converter in order to extract the maximum available power from Solar system. Solar energy has the greatest availability compared to other energy sources. For such solar PV systems, maximum power point tracking control is preferred for efficient operation. This concept is dealing with INC method which is one of the MPPT methods. This study deals with a buck–boost converter controlled solar photovoltaic (SPV) array fed water pumping in order to achieve the maximum efficiency of an SPV array and the soft starting of a permanent magnet brushless DC (BLDC) motor. The current sensors normally used for speed control of BLDC motor are completely eliminated. The speed of BLDC motor is controlled through the variable DC-link voltage of a voltage-source inverter (VSI). The VSI is operated by fundamental frequency switching, avoiding the losses due to high-frequency switching, in order to enhance the efficiency of the proposed system.

High‐order high‐performance LCLCL DC/DC converter based on harmonic optimisation

This work presents a new type of high-order LCLCL resonant DC/DC converter. The converter in this study can properly inject the third harmonic for energy transmission through optimal configuration and parameter design of the resonant tank, which can not only achieve a wider voltage regulation range but also provide an easy method for soft start and overcurrent protection. In this study, both switches can realise soft switching, and due to the injection of the third harmonic, the loss of the secondary rectifier diode is reduced. This article describes the working principle of the LCLCL converter and provides the parameter design principle and small-signal modelling method. In the laboratory, a 400 W prototype with 400 V input and 24 V output is built to verify the correctness of the theoretical analysis.