Effect Of Winding Research Articles

Dynamic models of 3-phase alternators including saliency effects using PSpice for Windows

This paper presents the dynamic model of a 3-phase synchronous machine using the graphical user interface provided by the PSpice program environment. The machine model includes the effects of the damper winding and salient poles. The paper presents results of the dynamic behavior of a salient pole synchronous machine including voltage, current, torque, and power traces. The model is organized in a hierarchical structure and includes custom symbols for the machine several functional modules like reference frame transformation modules. The custom symbols have been created within the Schematics editor of the PSpice program group. Details of the implementation as well as the theoretical equations are presented. The model that is shown in this paper is working on the free evaluation version of the PSpice software, Release 6.2a.

Electrical stresses applied to stator insulation in low-voltage induction motors fed by PWM drives

The authors report experiments to identify real voltage stresses applied by pulse-width modulated (PWM) variable-speed drive on the stator insulation of a low-voltage induction motor. The idea that PWM drives impose very high stresses on machine parts, especially the insulating material, is widely accepted. Many theories and simulations have been carried out on the subject for nearly a decade, but too few experimental confirmations have been undertaken. The authors have processed a standard motor to access the copper wires inside the stator winding. Observation of real electrical stresses applied to insulation was performed thanks to these tapping points. The ground insulation is first identified putting in value the inductive effect of winding and the complexity of the three-phase voltage combination at the star point. Monitoring of the voltages applied to interturn insulation reveals much higher surges than expected. Finally, the impact of PWM drives on insulating material is discussed with reference to the resulting experimental data.

Experimental study on harmonics reduction effects of damper windings in a synchronous generator

AbstractWith the recent development of power electronics technology, thyristor‐controlled equipment has largely been introduced to the electric power system. These devices generate harmonics that cause voltage distortion and undesirable effects on the power system components. On the other hand, the damper windings of synchronous generators basically are designed to reduce harmonics as well as to damp out system oscillations. However, up to now, the effects of damper windings on harmonics have not been clarified fully in a quantitative way.In this paper, the results of experimental study on the harmonics reduction effect of damper windings have been presented. A specially designed 6‐kVA generator was connected to an infinite‐bus system to investigate the characteristics of damper windings. A new method to measure induced voltages between damper bars, damper bar currents and air‐gap flux densities in the tested generator was established. By comparing these measurements with and without the presence of damper windings, the effect of damper windings was quantified. Thus the reduction effects of the damper windings on slot ripples and harmonics caused by armature current mmf were investigated and were made clearer than before by the proposed method.

A new inverter control scheme for induction motor drives requiring wide speed range

A new control scheme to extend the speed range of a four-pole induction machine is investigated. A three-phase stator winding is used with each of two coil groups per phase being independent resulting in a six-coupled circuit, six-terminal stator winding. Two inverters supply the machine with the required regulated currents to obtain the effect of either four-pole or two-pole windings. Four-pole operation is proposed from zero speed until the end of its constant power region. Employing contactorless pole changing to obtain two-pole operation extends the constant power region resulting in a doubling of the speed range for approximately the same inverter/machine rating. The application is to electric vehicles.

Experimental Study on Harmonics Reduction Effects of Damper Windings in a Synchronous Generator.

With the recent development of power electronics technology, thyristor-controlled equipment has largely been introduced to the electric power system. These devices generate harmonics that cause voltage distortion and undesirable effects on the power system components. On the other hand, the damper windings of synchronous generators basically are designed to reduce harmonics as well as to damp out system oscillations. However, up to now, the effects of damper windings on harmonics have not been clarified fully in a quantitative way. In this paper, the results of experimental study on the harmonics reduction effect of damper windings have been presented. A specially designed 6-kVA generator was connected to an infinite-bus system to investigate the characteristics of damper windings. A new method to measure induced voltages between damper bars, damper bar currents and air-gap flux densities in the tested generator was established. By comparing these measurements with and without the presence of damper windings, the effect of damper windings was quantified. Thus the reduction effects of the damper windings on slot ripples and harmonics caused by armature current mmf were investigated and were made clearer than before by the proposed method.

Application and Evaluation of Commutation Performance with an Exceptional Armature Winding Form for Small Universal Motors.

Small-sized, AC series commutator motors (universal motors) are used very much in small appliances such as vacuum cleaners and hand tools, because they offer advantages of high speed and low cost. In particular, motors for vacuum cleaners are being designed with smaller size, but higher speed and increased output power. Therefore, it is desirable to improve commutation performance, because it influences the brush lifetime.In this paper, a method to improve commutation performance of the motors is described. It is an exceptional armature winding form in which the turn number of the backward coil is less than that of the forward coil in the same slots. The commutation sequence determines which is the backward coil and which is the forward one. The configuration and operation of the exceptional armature winding form for universal motors are detailed. A factor to relate the commutation performance using the magnetic field and the commutation analyses is also described. The design theory is built up with respect to the exceptional armature winding form and usefulness of the method is verified for predicting brush lifetime with actual motors. The effect of the armature winding to improvement the brush lifetime is confirmed experimentally.

Damper windings in synchronous machines fed by a current-source inverter

The mathematical model of an inverter-fed synchronous machine which permits detailed analysis of the behaviour of the damper winding is described. The effects of the damper winding on the steady-state characteristics of the inverter-fed synchronous-machine, especially on the torque ripple and commutation behaviour, are examined. It is shown that the damper winding has relatively little effect on the torque and overload capability.

Design of universal variable-structure controller for dynamic stabilisation of power systems

A study on the application of variable-structure control techniques for improving power system dynamic stability is presented. The basic concepts and design criteria of variable structure control are briefly discussed. The procedure of designing a variable-structure controller for a synchronous machine connected to infinite busbar using a simple linear model obtained by linearising nonlinear characteristics of the system is explained. The effect of variation of machine output power, transmission line reactance and infinite bus voltage on the design of the controller is investigated. A controller algorithm that guarantees proper operation irrespective of machine output power, transmission line reactance and infinite bus voltage is discussed. The performance of the controller is verified using a more elaborate synchronous machine model in which the effect of damper windings is treated. The results of the simulation studies show that with the proposed controller the stability of the power system is improved significantly.

Effects of rotor eccentricity and parallel windings on induction machine behavior: a study using finite element analysis

Rotor eccentricity and the effect of parallel windings in an induction motor are investigated by means of a transient finite element model. Magnetic flux density and force distribution harmonics generated by the model are presented for the cases of static and dynamic rotor eccentricity, with various combinations of series and parallel stator winding connections. These results are compared with those obtained from a centered rotor case. Examples of the action of parallel-connected windings to reduce the effects of rotor eccentricity are given. The effect of circulating current between various combinations of parallel windings in an eccentric rotor induction machine is shown to reduce the unbalanced magnetic pull and to significantly reduce or eliminate other vibration-producing magnetic force harmonics generated by the eccentricity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Phase co-ordinate model for analysis of isolated power systems

A computational procedure employing a phase co-ordinate reference frame has been used to study the transient behaviour of a group of induction motors when they become isolated from a large power system and fed from a standby generator. The model applied enhances flexibility in studying symmetrical and asymmetrical operating conditions, and shows how phase co-ordinate models can be used for detailed studies while retaining the physical configuration of the system. The model is easily adapted to investigate different system variables, e.g. current in each phase, node voltages, torque and speed recovery, generator field current, internal machine EMF and the effect of damper windings. These enable more accurate system behaviour to be predicted, and hence better system design and performance can be achieved.

Theoretical and experimental study of vibrational behaviour of laminated stators of electrical machines

An accurate determination of the resonant frequencies and vibrational characteristics of a stator is essential in the design of quiet electrical machines. This paper presents both a fundamental theoretical and an experimental study of the vibrational behaviour of long and short laminated stators of electrical machines. The paper describes briefly the method of analysis, based on the three-dimensional theory of elasticity, for free vibrations of stators with encased construction. To prove the general validity of the analysis and to study the effect of windings, frame, and impregnation upon the resonant frequencies and vibrational behaviour of the stators of electrical machines, extensive experimental investigations were conducted on a number of stator models which include a solid model, long laminated, and short laminated models with and without windings, frame and impregnation. The paper compares the experimental and analytical results for some of these models which prove the general validity of the analysis. Finally, the paper also includes the important findings of these extensive investigations.

Structure-activity relationships of (+)-CC-1065 analogues in the inhibition of helicase-catalyzed unwinding of duplex DNA.

(+)-CC-1065 is a potent antitumor antibiotic produced by Streptomyces zelensis. Previous studies have shown that the potent cytotoxic and antitumor activities of (+)-CC-1065 are due to the ability of this compound to covalently modify DNA. (+)-CC-1065 reacts with duplex DNA to form a (N3-adenine)-DNA adduct which lies in the minor groove of DNA overlapping with a five base-pair region. As a consequence of covalent modification with (+)-CC-1065, the helix bends into the minor groove and also undergoes winding and stiffening. In the studies described here, we have constructed templates for helicase-catalyzed unwinding of DNA that contain site-directed (+)-CC-1065 and analogue DNA adducts. Using these templates we have shown that (+)-CC-1065 and select synthetic analogues, which have different levels of cytotoxicity, all produce a significant inhibition of unwinding of a 3'-tailed oligomer duplex by helicase II when the displaced strand is covalently modified. However, the extent of helicase II inhibition is much more significant for (+)-CC-1065 and an analogue which also produced DNA winding when the winding effects are transmitted in the opposite direction to the helicase unwinding activity. This observed pattern of inhibition of helicase-catalyzed unwinding of drug-modified templates was the same for a 3'-T-tail, for different duplex region sequences, and with the Escherichia coli rep protein. Unexpectedly, the gel mobility of the displaced drug-modified single strand was dependent on the species of drug attached to the DNA. Last, strand displacement by helicase II coupled to primer extension by E. coli DNA polymerase I showed the same pattern of inhibition when the lagging strand was covalently modified. In addition, the presence of helicase II on single-stranded regions of templates caused the premature termination of primer extension by DNA polymerase. These results are discussed from the perspective that (+)-CC-1065 and its analogues have different effects on DNA structure, and these resulting structural changes in DNA molecules are related to the different in vivo biological consequences caused by these drug molecules.

A Study on Prototype Vehicle Model of Magnetically Levitated System by LIM.

Many magnetically levitated systems are applied in semiconductor factories to avoid the dusts. The proposed magnetically levitated system in this paper consists of a linear induction motor (LIM) as a guide way and a vehicle. The system is a kind of attraction type levitation system by alternating current. Both the driving force and the levitation force are obtained by the magnetic force of LIM. In this paper, the levitation characteristics at three phase excitation and at equivalent slipping state are discussed experimentally. The results show that the vehicle can be levitated without any contact to the guide way. Moreover, as a prototype vehicle model, the vehicle with a storage battery and charging circuit is proposed. The battery can be charged by the transformer effect of secondary winding. As a result, it is clarified that the vehicle can be levitated stably even in the charging state. Finally the change of levitation characteristics by horizontal displacement is discussed with looking into the affect of slots.

The effect of windings, frame and impregnation upon the resonant frequencies and vibrational behavior of an electrical machine stator

In order to design a quiet electrical machine, an accurate determination of the resonant frequencies and vibrational characteristics of the stator is essential. This paper presents both a fundamental theoretical and experimental study which is designed to explore the manner in which the values of the resonant frequencies and vibrational behavior of a stator are affected by the presence of the windings, frame, and impregnation. Following a brief description of the method of analysis for the free vibrations of stators of encased construction, which is an energy method based on the theory of elasticity, details of the various models are given. It is found that the effects of both the windings and the frame are in general predictable and beneficial in so far as they tend to suppress the magnitude of the resonant amplitudes. Impregnation, however, has the opposite effect on these amplitudes but is found to play a desirable role in so far as it helps to eliminate unwanted parasitic resonances from the frequency spectrum.

同期機のオペレーショナルインピーダンス新決定法を用いた制動巻線乱調防止効果の検討

同期機のオペレーショナルインピーダンス新決定法を用いた制動巻線乱調防止効果の検討

Synchronous machine block diagram analysis with fast dynamics

Reduced order modelling techniques are employed to incorporate the dynamic effects of a q-axis damper winding in a lower-order synchronous machine model. Using timescale analysis of the two-axis model, it is shown that the DeMello-Concordia model is an approximation of the former under special conditions. An improved version of this model is derived which accounts for the damping provided by the amortisseur winding.

Torque Angle Loop Analysis of Synchronous Machines

This paper reports the dynamic stability analysis of a single machine infinite bus system through torque angle loop analysis and forms an extension of the work on Block diagrams and torque angle loop analysis of synchronous machines reported by I. Nagy [3]. It aims to incorporate in the machine model, the damper windings (one on each axis) and to compare the dynamic behaviour of the system with and without damper windings. The effect of using different stabilizing signals (viz. active power and speed deviations) on the dynamic performance is analysed and the significant effect of damper windings on the dynamic behaviour of the system is highlighted.

Particle interactions in flowing suspensions

For a fully destabilized suspension of non-Brownian praticles in laminar tube flow, the extent of orthokinetic flocculation can be calculated by classical Smoluchowski theory, using the average shear rate G and the average residence time t . It can be shown very simply that the dimensionless quantity Gt (and hence the degree of flocculation) depends only on the tube dimension and not on the flow rate. However, calculations based on this approach predict far more flocculation than is observed experimentally. There are two major reasons for the discrepancy: 1) the Smoluchowski treatment of orthokinetic flocculation neglects hydrodynamic interaction between particles, which can be introduced by a semi-empirical method due to van de Ven and Mason and this step leads collision efficiencies which are considerably less than unity and depend both on shear rate and on interparticle forces; 2) the shear rate is not uniform in the tube but varies from zero at the tube axis to a maximum value at the wall. Since the major contribution to the flow comes from regions close to the tube axis, where the shear rate is low, the simple averaging procedure considerably overestimates the degree of flocculation. From experimental measurements on the degree of flocculation of dispersions achieved by laminar flow through narrow tubes at different flow rates it is possible to draw semi-quantitative conclusions concerning particle interaction and the strength of flocs. The effect of helical winding of the tube is briefly considered and shown to give more flocculation than in a straight tube. Some experimental results for latex particles destabilized by cationic polymers flowing through straight and coiled tubes are mentioned.

Generic structural mechanics aspects of fusion magnet systems

Structural mechanics requirements for future large superconducting fusion magnets are assessed. Current structural analysis methods and standards do not yet appear sufficient for a complete evaluation of such systems, under all potential operating and accident conditions. Recommendations are made for development of needed structural methods and specialized standards for fusion magnets. These include, among others, better composite structural methods with various failure criteria for metallic, as well as non-metallic materials, coupled thermal-electrical—structural codes, incorporating winding and fabrication effects, and use of probablistic methods for life prediction. In order to help meet program goals for fusion commericialization, it is recommended that such work be initiated relatively soon.

Speed Control of a Single-Frame Cascade Induction Motor with Slip-Power Pump Back

This paper describes an analytical and experimental study of a self-cascade single-frame brushless induction motor, using a rectifier- inverter to control speed by slip-power pump back to the line. Steady- state analyses of asynchronous and synchronous performance and test results of a special machine wound for the study are presented. The effect of machine parameters, windings, and construction is discussed. The performance and rating of the brushless cascade machine are found to be equivalent to the slip-ring induction motor or wound-field synchronous machine built into the same frame.