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EPE-PEMC 2008 - Topic: Electrical Machines and Actuators
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	A Model of Semiconductor Converter-Fed Asynchronous Machines Taking into Account Energy Losses and Thermal Processes   By M. Pronin	[View]   [Download]
Abstract: A model of a semiconductor converter-fed dual-stator windings induction machine of the adjustable-speed propulsion drive is built up by decomposing the system into sub-circuits with lumped parameters which are coupled together by means of dependent voltage/current sources. Measurements of frequency responses of the driving point impedance of the stator windings have shown a strong impact of the skin effect on machine parameters. In the proposed model, electric and magnetic skin effects are reproduced by means of RL-ladder networks incorporated into the stator and rotor sub-circuits. A thermal model is described in terms of average temperatures and heat flows in the body of an induction machine. The paper concludes by examining the electromechanical and thermal responses of the motor energized by voltage sources of different waveforms.
	Analysis of Short-Circuit Forces at the Top of the Low Voltage U-Type and I-Type Winding in a Power Transformer   By Leonardo Štrac	[View]   [Download]
Abstract: The aim of this study was to compare the shortcircuit forces in the U-type and I-type low voltage winding of a large power transformer. The comparison of forces calculated using 2D Rabin's method and 3D finite element method is conducted. The influence of the winding helix pitch on the winding forces calculated using 3D finite element method is also investigated.
	Analysis of VSI-DTC Fed 6-phase Synchronous Machines   By Ibrahim Abuishmais	[View]   [Download]
Abstract: High power drives with multiphase machine utilizes paralleled legs converters to realize required power. In addition to the reduced rating of the used semiconductor devices, higher redundancy level could be achieved. Being a relatively new technology for the combination of VSI-fed operation and salient pole synchronous machines, a through analysis is needed. This paper investigates 6-phase synchronous machines with emphasis on redundancy, fault conditions, the machine's behavior under non-sinusoidal voltage profiles and sensitivity of the design parameters. It is shown that new design thinking is required when considering converter-induced machine losses, especially those on the rotor surface. Redundancy study shows the possibility of operating the machine at half load when one supply system is totally or partially lost without exceeding machine's total losses. When studying fault scenarios, the worst case is found to be 4-phase short circuit (equivalent to 2-phase in a 3-phase machine) for the studied cases. Output from sinus supply voltage study was utilized to understand losses distribution inside the machine and establish an effective comparison with different voltage profiles. A study with square wave and DTC supplies shows higher losses in damper bar, when compared to sinus supply. Voltage profiles of two different DTC schemes are studied which show that with particular well-thought control strategies one can improve the machine losses specially those in the damper bars.
	Analytical Method of Calculation of the Current and Torque of a Reluctance Stepper Motor Using Fourier Complex Series   By Pavel Záskalický	[View]   [Download]
Abstract: Stepper motors are becoming to be very attractive transducers for conversion of an electric signal to a mechanical position. Due to its simple construction the reluctance machine is considered as a very reliable machine which practically not require any maintenance. The present paper proposes a mathematical analytical method of a calculus of a phase current and electromagnetic torque of the motor via complex Fourier series. Saturation effect of the machine is neglected. Speed of the motor is considered to be constant.
	Anisotropy Comparison of Reluctance and PM synchronous Machines for Low Speed Position Sensorless Applications   By H. W. de Kock	[View]   [Download]
Abstract: Position sensorless control of reluctance- and PM synchronous machines at zero and low speed is possible using high frequency voltage injection and proper demodulation. The so-called anisotropy position, which is tracked by the HF sensorless scheme, is different to the actual rotor position: the difference contains both offset and time-varying components, which may be explained by carefully considering the high frequency behaviour of the machine and the effect that fundamental excitation and rotor position has upon it. This paper gives insight into the HF behaviour of machines and serves as a practical guide for implementation of stable and robust position estimation at zero and low speed.
	Bearing Damage Analysis by Calculation of Capacitive Coupling Between Inner and Outer Races of a Ball Bearing   By Jafar Adabi	[View]   [Download]
Abstract: bearing damage in modern inverter-fed AC drive systems is more common than in motors working with 50 or 60 Hz power supply. Fast switching transients and common mode voltage generated by a PWM inverter cause unwanted shaft voltage and resultant bearing currents. Parasitic capacitive coupling creates a path to discharge current in rotors and bearings. In order to analyze bearing current discharges and their effect on bearing damage under different conditions, calculation of the capacitive coupling between the outer and inner races is needed. During motor operation, the distances between the balls and races may change the capacitance values. Due to changing of the thickness and spatial distribution of the lubricating grease, this capacitance does not have a constant value and is known to change with speed and load. Thus, the resultant electric field between the races and balls varies with motor speed. The lubricating grease in the ball bearing cannot withstand high voltages and a short circuit through the lubricated grease can occur. At low speeds, because of gravity, balls and shaft voltage may shift down and the system (ball positions and shaft) will be asymmetric. In this study, two different asymmetric cases (asymmetric ball position, asymmetric shaft position) are analyzed and the results are compared with the symmetric case. The objective of this paper is to calculate the capacitive coupling and electric fields between the outer and inner races and the balls at different motor speeds in symmetrical and asymmetrical shaft and balls positions. The analysis is carried out using finite element simulations to determine the conditions which will increase the probability of high rates of bearing failure due to current discharges through the balls and races.
	Broken Rotor Bar Impact on the Closed Loop and Sensorless Control of Induction Machine   By Piotr Kołodziejek	[View]   [Download]
Abstract: This paper presents analysis of closed loop and sensorless control of induction machine with broken rotor bar for on-line diagnostics purposes. Closed loop control system synthesis of induction motor is based on symmetrical model of the machine. In case of induction machine operation with broken rotor bars, rotor speed pulsation is compensated by the control system. Simulation of Multiscalar Control with the fault machine shows that decoupling variables can be used as detection signals. Analysis of speed observer frequency response in open loop operation gives information about disturbance impact on estimation error. Further analysis indicates that machine asymmetry can affect stability of sensorless control system with speed observer.
	Condition Monitoring for Mechanical Faults in Fully Integrated Servo Drive Systems   By Jesus Arellano-Padilla	[View]   [Download]
Abstract: A modified motor current signature analysis (MCSA) approach to monitor the performance of a servo drive system using only one set of current transducers at the input side of the rectifier is proposed. The paper introduces a mathematical analysis to determine how the harmonic frequencies related to a fault propagate from the motor to the input inverter, and includes the effect of the DC Link components. Experimental results are presented for a Permanent Magnet servo drive system with faulty bearings to validate the proposed scheme.
	Coupled Magnetic Circuit Method and Permeance Network Method Modeling of Stator Faults in Induction Machines   By Amin Mahyob	[View]   [Download]
Abstract: The aim of this paper is to present and compare two modeling methods of the inter-turn short circuit fault in the stator winding of a cage induction machine. The first method is a Coupled Magnetic Circuit Method (CMCM) and the second method is a Permeance Network Method (PNM) which allows taking into account the saturation effect on the fault signature. The simulation results show that by proper modeling of induction machine it is possible to detect the effect of inter-turn short circuit faults on the machine line currents. The effect of saturation on the machine line current signature is discussed. The detailed equations describing the performance of the machine in the two cases of modeling under inter-turns short circuit faults are presented. Simulation results are compared for both healthy and faulty cases
	Direct Thrust Controlled Linear Induction Motor Including End Effect   By Berrin Susluoglu	[View]   [Download]
Abstract: As a special feature, the linear induction motor (LIM) has an end effect phenomena causing weakening in airgap flux also in thrust. In this paper, direct thrust control of linear induction motors is improved by considering the end effect in flux and thrust estimator part based on the mathematical model of LIM. To show the effectiveness of the improved system, simulation results are presented using commercially available software package Matlab/Simulink.
	Dynamic Simulation of PM Motor Drive System Based on Reluctance Network Analysis   By Kenji Nakamura and Osamu Ichinokura	[View]   [Download]
Abstract: This paper presents a method for dynamic simulation of a permanent magnet (PM) motor including its drive circuit based on reluctance network analysis (RNA). The RNA, which is based on the magnetic circuit method, has some advantages for simulating electric motors as follow: simple analytical model, high calculation accuracy, and easy to combine with external electric circuits, motion and thermal dynamics. First, the basis of the magnetic circuit method is described briefly. Next, a case study of dynamic simulation of a PM motor drive system is presented. The validity of the proposed method is proved by comparison with experimental results.
	Explosion Protected Electrical Drives - Risk Assessment and Technical Diagnostics   By Ivica Gavranić	[View]   [Download]
Abstract: In this paper the application of motors in plants at risk of explosive atmospheres, and the special requirements of such applications from the standpoint of explosion protection are considered. The application of motors with type of protection increased safety, marked as "EEx e", with and without associated safety systems, are analyzed for zone 2. Risk assessment of such applications, based on the requirements of ATEX Directive, is the main part of this paper. There is a specific example which illustrates the results of selection and application of motors with type of protection "EEx e" without the application of additional safety systems, which is the traditional approach. Possible application, in special cases, of the mentioned motor with the application of additional safety systems, which is the new approach, is also analyzed. The concept of the new approach is used in cases where diagnostic methods have determined that the basic explosion protection of an "EEx e" motor has been undermined. To establish the actual condition of a rotor squirrel cage, a diagnostic method based on the spectrum analysis of the stator current is used. This diagnostic test can ascertain the deteriorated condition of the rotor cage which directly affects its explosion protection. Damage to the rotor cage can be a serious source of ignition of explosive atmospheres.
	Feed-Forward Compensation of Load and Parameter Variations of Electric Drive   By Alon Kuperman, Yoram Horen, Saad Tapuchi and Uri Suissa	[View]   [Download]
Abstract: The paper presents a method to compensate effects caused by slow varying loads and plant parameters drift as well as by detuned controller using a simple yet robust algorithm in voltage controlled electric drives. In case of known variations an analytical expression of pre-computed feed-forward compensation voltage is derived, while in presence of unknown disturbances the control algorithm uses a simple Luenberger observer fed by data from a low cost encoder to estimate the feedforward voltage command reflecting the deviation of the model from its nominal value. It is shown that the feed-forward command reflects parameter changes as well as load torque and slow varying actuator and measurement noises. Simulation and experimental results are given to describe the control algorithm performance and limitations.
	Generalized Model for a Class of Switched Reluctance Motors   By Constantin Pavlitov	[View]   [Download]
Abstract: The paper deals with the problems of identification of a class of Switched Reluctance Motors (SRM). A generalized mathematical description of different SRMs with central geometrical symmetry of active poles is suggested. Convenient simulation cellular model of the motor is presented here that is of extreme importance in order to build up a proper SRM drive. The identification of Switched Reluctance Motors is rather sophisticated task due to the fact that the stator inductance depends on both position of the rotor and the stator current. The problem is further complicated due to the influence of the air gap and the highly nonlinear characteristic of the magnetic circuit. The mathematical model of the SRM is of a high order and is described by partial differential equations. In order to avoid this complex mathematical description, artificial neural network substitutions are utilized. They simplify the process of identification and make it easy - using Matlab Simulink. A suggestion for future work is also made in the paper.
	Identification of Mathematical Model Induction Motor's Parameters with Using Evolutionary Algorithm and Multiple Criteria of Quality   By Hudy Wiktor	[View]   [Download]
Abstract: In this paper identification's method of mathematical model induction motor's parameters was shown. This identification is based on evolutionary algorithm. The criterion, which is the functional of four quality indexes, was applied. This criterion was calculated by finding a common one from four quality indexes, which is the functional of absolute value of four quality indexes product. The identification was calculated by finding the minimum of last functional. Four factors of product were the difference between values of dynamic characteristics and characteristics at present calculated on the basis of individuals. Mathematical model parameters of induction motor were values of individuals' parameters. On the basis of calculated parameters' values characteristics generated were compared with experimental characteristics. The identification was made with using Tamel Sg90L-6 induction motor.
	Induction Motor Parameters Identification using Genetic Algorithms for Varying Flux Levels   By Konstantinos Kampisios	[View]   [Download]
Abstract: This paper describes a novel approach for identifying induction motor electrical parameters in function of flux levels based on experimental transient measurements from a vector controlled Induction Motor (I.M.) drive and using an off line Genetic Algorithm (GA) routine with a linear machine model. The evaluation of the electrical motor parameters is achieved by minimizing the error between experimental and simulation model responses. An accurate and fast estimation of the electrical motor parameters is performed by running a number of optimizations using experimental tests taken under different operating conditions (flux level). Results are verified through a comparison of speed, torque and line current responses between the experimental IM drive and a Matlab - Simulink model.
	Influence of Saturation Effects in a Transverse Flux Machine   By M. Siatkowski and B. Orlik	[View]   [Download]
Abstract: In this paper the torque density of Transverse Flux Machines is investigated against the flux density inside the active parts with analytical calculations and FEM simulations. Especially saturation effects, which reduce the flux linkage with the coil, and core losses, are considered for both, the flux concentrating setup and the surface mounted magnets topology. The calculations are verified by measurements on an existing prototype. Finally new design guidelines are developed for the construction of TFMs with regard to the magnetic circuit.
	Modelling of Electrical Machines Using the Modelica Bond-Graph Library   By Mieczyslaw Ronkowski	[View]   [Download]
Abstract: The paper presents the bond graphs approach to modelling electrical machines for controlled electromechanical systems applications. The bond graph models of electrical machines are based on the models of ideal couplings: transformer and electromechanical couplings, respectively. Using the couplings models as building blocks the models of electrical machines (brushed and brushless dc machines with permanent magnets, and synchronous machine) have been developed in terms of bond graphs. The models have been elaborated using the Modelica Bond-Graph Library and the DYMOLA package.
	Neural Network Based Fault Detection of PMSM Stator Winding Short Under Load Fluctuation   By J. Quiroga	[View]   [Download]
Abstract: A negative sequence analysis coupled with a neural network based approach is applied to fault detection of a single phase winding short in a PMSM. A multilayer network provides a near term current prediction as input to the fault detection system. The fault detection is performed using the negative sequence analysis of the residuals (difference between the actual and predicted values of currents). The negative sequence component of the residuals provides the detection of the fault and a measurement of the level of severity of the winding short. The method is validated using a 15 hp PMSM experimental setup.
	Optimal Rotor Flux Shape for Multi-phase Permanent Magnet Synchronous Motors   By Roberto Zanasi	[View]   [Download]
Abstract: In the paper the Power-Oriented Graphs (POG) technique is used for modeling m-phase permanent magnet synchronous motors and a study on the optimal rotor flux is given. The POG model shows the "power" internal structure of the considered electrical motor: the electric part interacts with the mechanical part by means of a "connection" block which neither stores nor dissipates energy. The dynamic model of the motor is as general as possible and it considers an arbitrary odd number of phases. The rotor flux is analyzed, in particular in order to minimize the currents needed for the torque generation, and its optimal shape is given. The model is finally implemented in Matlab/Simulink and the presented simulation results validate the machine model and the rotor flux choice.
	Performance Improvement of Direct Torque Controlled Interior Permanent Magnet Synchronous Motor Drive by Considering Magnetic Saturation   By Behrooz Majidi, Jafar Milimonfared and Kaveh Malekian	[View]   [Download]
Abstract: The influence of magnetic saturation on the maximum torque per ampere strategy in constant torque region and field weakening strategy in constant power region for a direct torque controlled interior permanent magnet synchronous motor drive are discussed in this paper. In other words, by considering magnetic saturation, all optimal strategies and motor-inverter limitations are derived in the T -|ψs| plane to apply in the direct torque control method. These strategies that take magnetic saturation into account and determine the optimal torque and flux commands are derived and implemented in direct torque control method. Simulation results on a prototype interior permanent magnet motor are included to validate the usefulness of the work.
	Review of Electrical Machine in Downhole Applications and the Advantages   By Anyuan Chen, Ravindra. B. Ummaneni, Robert Nilssen and Arne Nysveen	[View]   [Download]
Abstract: To enable safe, economical and environmentally acceptable solutions for improving oil and gas recovery from mature fields and for exploitation of deep and ultra-deep offshore reservoirs, new downhole technologies are required. Electrification of downhole applications has proven to be promising. This paper presents electrical machine in currently available or emerging downhole applications and their advantages. Permanent magnet machines are the trend for downhole applications.
	Study of the Sudden Symmetrical Short-Circuit Using the Mathematical Models of the Synchronous Machine and the Numerical Methods   By Petropol Serb Gabriela	[View]   [Download]
Abstract: In the last decade, the field of Fault Detection and Diagnosis in the electric motor manufacturing industry, are becoming more important. The methods used to study the fault detection and diagnoses are based on an explicit mathematical model of the system under test. This article presents, in detail, a method for the study and the simulation of a symmetrical short-circuit of a synchronous machine. It will be calculate and plot the variation of the current of a phase in time, by using the software of Matlab. So, the paper is a theoretical approach on the fault detection and simulation.
	The Effect of Subharmonics on Induction Machine Heating   By Piotr Gnacinski	[View]   [Download]
Abstract: One of the most rarely discussed power quality disturbances are subharmonics - voltage components of frequency less than the fundamental one. They may appear in both land and in ship power systems. This work deals with the influence of voltage subharmonics on temperature-rise distribution in an induction cage machine. The results of experimental investigations are presented for a totally-enclosed, four poles 3-kW induction machine with built-in thermocouples.
	The Model of the Squirrel Cage AC Motor Including Rotor Slot Harmonics   By Eleonora Darie	[View]   [Download]
Abstract: The model of the squirrel cage AC Motor is based on multiple coupled circuits and takes into account the geometry and winding layout of the machine. All inductances are derived by means of the winding function approach and are integrated with the decomposition into their Fourier series. An important issue in such effort is the modeling of the induction motor including rotor slot harmonics (RSH) under symmetrical and asymmetrical conditions, with minimum computational complexity.
	Thermal Effect of Short-Circuit Current in Low Power Induction Motors   By Leoš Beran	[View]   [Download]
Abstract: Diagnostic of reliability of induction motors (IM) is very important for industry. The article deals with the analyse of short-circuit currents in stator winding of low power induction motors which can strongly affected reliability of IMs. The occurrence of short-circuit arises when some parts of the insulation system of a stator winding breakdown. The stator winding loses a part of active coil and its inductivity decreases. The short-circuit current warms up the surrounding stator winding with its heat effect at point of the short-circuited stator winding. Theoretical part describes two models to simulate different short-circuits that can occur in the stator winding. The first model is a single-phase linear model and the second is a numerical model in SymPowerSystems Toolbox of Matlab software. Chapter III analyses thermal activity on separate parts of the stator winding. Thermal effects were verified on a set up model that consists of a specially designed experimental motor (EM) with the temperature monitoring in slots of the stator.
	Use of an AC Self-Excited Switched Reluctance Generator as a Battery Charger   By Abelardo Martínez	[View]   [Download]
Abstract: We analyzed an AC self-excited switched reluctance generator used as a battery charger, using a second- order nonlinear oscillator model. Generator capacity can be maintained under variable rotor speed by adapting the external capacitance. The AC voltage generated is rectified and adapted with a DC-DC converter to battery voltage. To keep the flux machine under control, the rectified bus voltage should be changed according to oscillating frequency, following a constant voltage/frequency ratio. The simplicity of the system makes it an adequate wind generator for battery charging in isolated locations.