Multi phase system for metal disc induction heating: modelling and RMS current control

This paper presents a multi phase induction system modelling for a metal disc heating and further industrial applications such as hot strip mill. An original architecture, with three concentric inductors supplied by three resonant current inverters leads to a reduced element system, without any coupling transformers, phase loop, mobile screens or mobile magnetic cores as it could be found in classical solutions. A simulation model is built, based on simplified equivalent models of electric and thermal phenomena. It takes into account data extracted from Flux2D® finite element software, concerning the energy transfer between the inductor currents and the piece to be heated. It is implemented in a versatile software PSim, initially dedicated to power electronic. An optimization procedure calculates the optimal supply currents in the inverters in order to obtain a desired power density profile in the work piece. The paper deals with The simulated and experimental results are compared in open-loop and closed loop. The paper ends with a current control method which sets RMS inductor currents in continuous and digital conditions

To develop an efficient variable speed compressor motor system

This research presents a proposed new method of improving the energy efficiency of a Variable Speed Drive (VSD) for induction motors. The principles of VSD are reviewed with emphasis on the efficiency and power losses associated with the operation of the variable speed compressor motor drive, particularly at low speed operation.The efficiency of induction motor when operated at rated speed and load torque is high. However at low load operation, application of the induction motor at rated flux will cause the iron losses to increase excessively, hence its efficiency will reduce dramatically. To improve this efficiency, it is essential to obtain the flux level that minimizes the total motor losses. This technique is known as an efficiency or energy optimization control method. In practice, typical of the compressor load does not require high dynamic response, therefore improvement of the efficiency optimization control that is proposed in this research is based on scalar control model.In this research, development of a new neural network controller for efficiency optimization control is proposed. The controller is designed to generate both voltage and frequency reference signals imultaneously. To achieve a robust controller from variation of motor parameters, a real-time or on-line learning algorithm based on a second order optimization Levenberg-Marquardt is employed. The simulation of the proposed controller for variable speed compressor is presented. The results obtained clearly show that the efficiency at low speed is significant increased. Besides that the speed of the motor can be maintained. Furthermore, the controller is also robust to the motor parameters variation. The simulation results are also verified by experiment

Soft-started Induction Motor Modeling and Heating Issues for Different Starting Profiles Using a Flux Linkage ABC Frame of Reference

In order to mitigate the adverse effects of starting torque transients and high inrush currents in induction motors, a popular method is to use electronically controlled soft-starting voltages utilizing series-connected silicon-controlled rectifiers (SCRs). Investigation of semioptimum soft-starting voltage profiles was implemented using a flux linkage ABC frame of reference model of a soft-started three-phase induction motor. A state-space model of the soft-starter thyristor switching sequence for the motor and load was developed and implemented in a time-domain simulation to examine winding heating and shaft stress issues for different starting profiles. Simulation results of line starts and soft starts were compared with measured data through which validation of the model was established. In this paper, different induction machine soft-start profiles are shown, and comparisons of starting times, torque profiles, and heating losses are made. Discussion of these results and conclusions as to the near-optimum types of profiles are delineated based on peak torque, starting times, and winding heating criteri

Investigation of the Heating Processes and Temperature Field of the Frequency-controlled Asynchronous Engine Based on Mathematical Models

The study of the temperature field of the engine for non-stationary modes is done. A numerical simulation of a non-stationary thermal process using dynamic EHD, the characteristic of the rate of rise of temperatures is done. An increase in the temperature of individual parts in the idle interval, when the power of heat release is significantly reduced, is established, and the reverse of the heat flow through the air gap is established. It is shown that the EHD method, in contrast to the FEM, is self-sufficient, which determines its practical value. In various parts of the speed control range in the implementation of various laws of regulation. At the same time, the main electrical, magnetic and additional losses associated with the fundamental voltage harmonics (FVH), and mechanical losses, as well as additional electrical and magnetic losses associated with the higher voltage harmonics, change. When using serial asynchronous engines as frequency-controlled. Permissible under the conditions of heating power is significantly reduced by the power of serial engines. Depending on the synchronous speed, the reduction is from 10 % to 20 %. Given the additional overheating due to higher voltage harmonics, as well as the deterioration of the cooling conditions when adjusting the rotational speed "down" from the nominal, it seems very relevant

Emulating bearing faults : a novel approach

The relation between evolving mechanical faults in rotating electrical machines and their reflection in the machines’ electrical parameters still requires a lot of research. This implies serious obstructions in the evolution of e.g. Motor Current Signature Analysis as a complete and reliable condition monitoring technology. This paper presents the translation of common bearing faults into specific rotor-stator movements using finite element modeling. Subsequently, a novel method to elucidate the complex relation between rotor movements and the electrical parameters of an induction machine using an experimental test setup is described, dimensioned and simulated. Replacing one of the induction machine’s bearings with an Active Magnetic Bearing will give the opportunity to create specific rotor movements and consequently evaluate different programmable mechanical faults and their reflection in the stator current and/or voltage with high relevance and reproducibility

Influence of equivalent circuit resistances on operating parameters on three-phase induction motors with powers up to 50 kw

This work shows the results obtained from studying the influence of equivalent circuit resistances on three-phase induction motors. The stator resistance, rotor resistance, and iron losses resistance affect the different motor operating variables (output power, current, speed, power factor, starting ratios, and maximum torque). These influences have been quantified, paying particular attention to the losses affected and their impact on efficiency. The study carried out does not apply optimization techniques. It evaluates the different influences of the equivalent circuit’s different resistances on its operation by evaluating applicable constructive modifications concerning available motors. The work has been limited to three-phase induction motors up to 50 kW and low voltage, with the nominal powers of the selected motors being 0.25 kW, 1.5 kW, 7.5 kW, 22 kW, and 45 kW. The tools used to carry out the study are analyzing the equivalent circuit and the simulation of the electromagnetic structure using a finite-element program. The variations proposed in each resistance for all the motors studied is not purely theoretical, as it is based on applying feasible constructive modifications, appropriately analyzed and simulated. These modifications are the variation of the conductor diameter in the stator coils, the change of the section of the rotor cage, and the selection of different ferromagnetic steel types. © 2021 by the authors. Licensee MDPI, Basel, SwitzerlandPeer ReviewedPostprint (published version

Impact of Heat Pump Load on Distribution Networks

© The Institution of Engineering and Technology 2014. Heat pumps can provide domestic heating at a cost that is competitive with oil heating in particular. If the electricity supply contains a significant amount of renewable generation, a move from fossil fuel heating to heat pumps can reduce greenhouse gas emissions. The inherent thermal storage of heat pump installations can also provide the electricity supplier with valuable flexibility. The increase in heat pump installations in the UK and Europe in the last few years poses a challenge for low-voltage networks, because of the use of induction motors to drive the pump compressors. The induction motor load tends to depress voltage, especially on starting. The study includes experimental results, dynamic load modelling, comparison of experimental results and simulation results for various levels of heat pump deployment. The simulations are based on a generic test network designed to capture the main characteristics of UK distribution system practice. The simulations employ DIgSlILENT Power Factory to facilitate dynamic simulations that focus on starting current, voltage variations, active power, reactive power and switching transients

A study of saturated induction motor starting performance

The use of induction motors in modern industry become increasingly high. Induction motor starting phenomenon has an important impact on the industrial loads and dynamics of the power system. Induction motor consumes tremendous amount of reactive power during starting, resulting in considerable drop in the terminal voltage. The starting current of the motor increases six to seven times of the rated current and starting time extends. This voltage depression during the starting transient period affects the starting and acceleration torque of the motor, as it is a function of the voltage. In this research work, starting performance of induction motor is investigated and analyzed comprehensively. To minimize the terminal voltage drop of the motor during starting, reactive power compensation is required. Static VAR compensator (SVC) and shunt capacitors are used as a source of reactive power for both 50 hp and 500 hp motors. By employing SVC and shunt capacitors, significant improvement in the terminal voltage is achieved with less starting time for different loading conditions. The saturation takes place in almost all induction electrical machines and induction motors are no exceptions. Transient saturated induction motor (50 hp) model is developed to investigate the effect of main flux saturation on the starting performance for different loading conditions

Thermal Modelling and Analysis of A 10HP Induction Machine Using the Lumped Parameter Approach

The essence of this research work is to develop a thermal model for an induction machine that will enable the prediction of temperature in different parts of the machine. This is very important first to the manufacturer or designer of an induction machine because with these predictions one can decide on the insulation class limits the machine belongs to. Also modern trends in the construction of machines is moving in the direction of making machines with reduced weights, costs and increased efficiency. In order to achieve this, the thermal analysis becomes very crucial in deciding on what types of insulators and other materials that would be used to make these machines. In industries, the knowledge of the thermal limits of machines if well utilized increases the life span of the machines and reduces downtime; thereby increasing production and profit. Specifically, this paper (i) predicted the temperature limits of the induction machine and its components, (ii) developed an accurate thermal model for an induction machine, (iii) predicted the temperature in different parts of the induction machine using the thermal model and software program and lastly (iv) investigated how the machine symmetry is affected by the nodal configuration

Study of the Thermal Behavior of a Three-phase Induction Motor under Fault Conditions

Electric motors play an important role in the industry, because nowadays almost everything in the industry works with the auxiliary of them, either for low or high power ratings. It is possible to divide the electric motors in induction motors and synchronous motors, however the most used in the industry are the induction motors. So, it is very important to monitor its behavior throughout the time. Due to their working conditions, which sometimes can be very adverse, the motor losses can increase the inner machine temperature causing degradation of the materials which will lead to serious faults. Most severe faults may lead to a machine breakdown and interruption of the industrial production inflicting severe financial loss. The main goal of this dissertation is to create a computational model of a three-phase squirrel cage induction motor to study and analyze its thermal behavior under healthy and faulty conditions. This will be made through the finite elements method (FEM), where Flux2D 12.1 (Cedrat) software will be used. Initially the computational modeling will focus on the electromagnetic study, in order to calculate the motor losses. After that, those values will be inserted in the thermal simulation to better understand the thermal behavior of the motor. The experimental tests will be carried out with the aid of five temperature sensors (PT100), where the acquisition of the experimental data will be done through a software developed in LabView programming language. As well as that, the results obtained experimentally will be compared with those obtained computationally. However, only the results of two sensors can be compared, since two of them are placed throughout the three-dimensional perspective of the motor and one is placed inner of the motor frame, which will not be defined in the simulation.Os motores elétricos desempenham um papel bastante importante na indústria, pois hoje em dia quase tudo na indústria funciona com o auxílio destes, seja em reduzidas ou elevadas potências. É possível dividir os motores elétricos em motores de indução e motores síncronos, no entanto os mais utilizados na indústria são os de indução, sendo então bastante importante monitorizar o seu comportamento ao longo do tempo. Devido às suas condições de funcionamento, que por vezes são bastante adversas, as perdas do motor podem aumentar causando a degradação dos materiais e levando a falhas graves, que podem prejudicar toda a produção de uma indústria, infligindo graves perdas financeiras O objetivo principal desta dissertação é criar um modelo computacional de um motor de indução trifásico de rotor em gaiola de esquilo para estudar e analisar o seu comportamento térmico, tanto sob condições normais como de avaria. Este trabalho será desenvolvido através do método de elementos finitos (FEM), sendo assim utilizado o software Flux2D 12.1 (Cedrat). Inicialmente a modelação computacional focar-se-á no estudo eletromagnético, de forma a calcularem-se as perdas do motor. Posteriormente, esses valores serão inseridos na simulação térmica, de forma a compreender-se melhor o comportamento térmico do motor. Os ensaios experimentais terão o auxílio de cinco sensores de temperatura (PT100) onde a aquisição dos dados experimentais é efetuada através de um software desenvolvido na linguagem de programação LabView. Posteriormente, os resultados obtidos experimentalmente serão comparados com os resultados obtidos computacionalmente. Porém, apenas os resultados de dois dos sensores podem ser comparados, pois existem dois sensores ao longo da perspetiva tridimensional do motor e um que está situado na periferia interna da carcaça, a qual não será definida na simulação