On the theory of main flux saturation in smooth airgap electrical machines

Contents The physical foundation of the theory of the smooth airgap machine with main flux saturation taken into account is carefully examined with special reference to the justification of the simplifying assumptions commonly used when the transient equations are established. An experiment showing the nature of the magnetic interaction between coils in quadrature is demonstrated. Measured and computed results are compared.

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Über die Theorie der Sättigung des magnetischen Hauptflusses in Zylinderläufermaschinen

Übersicht Die physikalischen Voraussetzungen und die notwendigen Vereinfachungen in der Theorie der Zylinderläufermaschine bei veränderlicher Sättigung des magnetischen Hauptflusses sind genau formuliert und präzisiert. Es wird ein Experiment beschrieben, das die Messung der induktiven Kopplung zwischen zwei Spulen erlaubt, deren Achsen senkrecht zueinander stehen. Die durch Messung genauen Resultate werden mit den numerisch berechneten Ergebnissen verglichen.

     

Medium frequency shaft voltages in large frequency converter driven electrical machines

The operation of large electrical machines like turbo-generators with ratings of several hundred MVAs by static frequency converters can cause shaft voltages of several hundred volts. The shaft voltages consist of peaks with a time constant of some μs. They occur mainly during the rectifier switching at the grid-linked section of the converter. The voltages are the result of a coupled capacitive and inductive phenomenon. The root cause of these voltages is shown and a machine model of turbo generators for several 10 kHz is developed taking parasitic capacities and eddy currents into account. It is not sufficient to limit the model just to the generator. It is the combination of transformator, cables, frequency converter and generator, which allow for such high voltages. Comparisons with measurements on a 300 MVA generator are made to verify the model. A high level of agreement between measurement and calculation is reached for this recently discovered capacitive inductive shaft voltage phenomenon. Especially the high power class of the equipment involved reveals the underlying physics fairly clearly, but enforces a deep investigation and high predictability of the right counter measures in order to avoid substantial risk exposures.     

Comparative study of 3-D flux electrical machines with soft magnetic composite cores

This paper compares two types of three-dimensional (3-D) flux electrical machines with soft magnetic composite (SMC) cores, namely, claw-pole and transverse-flux machines. 3-D electromagnetic field analysis is conducted for the computation of some important parameters and optimization of the machine structures. An equivalent electric circuit is derived to calculate the machine performance. The analysis methods are validated by experimental results of a single-phase claw-pole permanent-magnet machine with an SMC core. Useful conclusions are drawn from the evaluation and comparison of two machines with SMC cores.     

An automated system for frequency response analysis with application to an undergraduate laboratory of electrical machines

This paper describes a LabVIEW-based automated system to carry out frequency response tests in electrical machines. The system is being used by undergraduate students in the laboratory of electrical machines, where they can experiment with the application of frequency response analysis and the characterization of mathematical models. An advantage of the system is its friendly user interface to a laboratory experiment. The system avoids the risky utilization of oscilloscopes for data acquisition and shortens the time taken to analyze the measured data. The Automated System for Frequency Analysis (ASFFA) can carry out tests within a bandwidth of 0.001-900 Hz. In addition, the ASFFA can estimate the transfer function parameters based on one- or two-port network theory. Design details of the interface, system structure, frequency response tests, electrical machine modeling, and signal processing are presented. Finally, ASFFA is applied to synchronous, induction, and direct-current machines.     

畸变磁通作用下变压器铁心模型损耗的实验研究与模拟分析

对畸变磁通条件下产品级变压器铁心模型的损耗进行了实验研究,考察了谐波相位差变化对铁心损耗的影响。给出了一种能够考虑畸变磁通条件下铁心损耗的工程计算方法,该方法可有效地考虑局部磁滞回环对铁心损耗的影响。结合MagNet电磁分析软件,计算了产品级变压器铁心模型的铁心损耗,通过对比实验结果证明了方法的有效性。     

Sensorless flux position estimation at low and zero frequency by measuring zero-sequence current in delta-connected cage induction machines

This paper considers the estimation of both flux and rotor position in delta-connected cage induction machines operating at low and zero frequencies. It is shown that the variation of leakage inductance due to either saturation or rotor slotting can be tracked by measuring the derivative of the zero-sequence current in response to the application of appropriate voltage test vectors. The method requires access to the machine phase windings but needs only a single extra sensor, in the form of a nonintegrating Rogowski Coil, which measures directly the zero-sequence current derivative. In this paper, experimental results are presented for the tracking of flux position.     

Calculation of iron loss in rotating machines by direct consideration of eddy currents in electrical steel sheets

A method for calculation of iron loss in rotating machines is proposed. The calculation employs the finite element method while taking into consideration the eddy currents in electrical steel sheets. First, the electromagnetic field distribution and iron loss of several types of electrical steel sheets are calculated by the proposed method, formulated as a one‐dimensional model. The results are compared with those of experiments and the conventional method in order to verify the validity of the proposed method. The influence of the skin effect and magnetic saturation in the electrical steel sheets on the iron loss characteristics is also investigated. Next, the proposed method formulated as a three‐dimensional model is applied to several types of rotating machines. It is shown that the skin effect is significant in the case of high‐frequency harmonic fields and that direct consideration of eddy currents by the finite element method is indispensable in such cases. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 69–80, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21053     

High-response flux control of direct-field-oriented induction motorwith high efficiency taking core loss into account

Stator core loss has significant adverse effects when an induction motor is controlled by the conventional field-oriented method. Therefore, taking core loss into account should make it possible to control the torque very precisely. In this paper, a direct-field-oriented induction motor with a deadbeat rotor flux controller was developed. The method ensures maximum efficiency in the steady state without degradation of the dynamic response. Simulation and experimental results have demonstrated that this method has higher efficiency and good speed response without any degradation in the transient characteristics     

The improvement of the electrical insulation of high voltage electrical machines

Comparative parameters are presented for the electrical insulation systems of high voltage electric machines. Composite insulation materials produced by different manufacturers are studied. The influence of the structure and composition of electrical insulation materials on the main operation parameters (electric strength, dielectric losses, the mechanical characteristics, and resistance to thermal cycling) of the insulation systems of electric machines is shown.     

正弦与非正弦激励下高频变压器磁心损耗计算与验证

提高正弦和非正弦激励下的磁心损耗模型的计算精度,对高频变压器的设计与研究有重要意义.本文首先在经典正弦损耗分离模型的基础上引入涡流和剩余损耗修正系数,推导出在方波与三角波电压激励下修正的损耗分离计算模型,并通过实验室搭建的磁特性测量系统测量出非晶与纳米晶磁心的损耗数据.其次,依据损耗系数随磁通变化的特性,提出一种改进的损耗分离模型的方法,与经典模型相比有更高的准确性,并得出非正弦激励下改进的计算模型.最后,对比分析方波与三角波电压激励下的计算结果与测量值,验证了本文提出的改进损耗分离模型的有效性与可行性.     

Effect of mechanical stress on different core loss components along orthogonal directions in electrical steels

Electrical Engineering - The paper deals with the characterization and modelling of the mechanical stress dependency of magnetic losses along two orthogonal directions in non-oriented electrical...     

高频磁损测试平台正弦激励源设计

为了获得磁芯在不同频率和磁通密度下的正弦激励损耗,高频磁损测试平台系统应能够可靠有效地调节激励波形频率和幅值。研究基于直接数字合成技术AD9834芯片产生所需频率的正弦信号,并通过与DAC芯片AD5620结合调制正弦信号源的幅值,单片机可通过SPI三线串口对信号源进行实时调节。实验结果表明,该系统可以得到幅值、频率连续可调的正弦波,输出频率范围宽,稳定性好,可以为高频磁芯损耗测试平台提供可靠的正弦信号源。     

Calculation of the flux density and the unbalanced pull in two pole induction machines

Contents In this paper, the relationship between the homopolar flux generated by a statically eccentric rotor and the unbalanced magnetic pull in two-pole induction motors is considered. We will show that due to this kind of eccentricity, a homopolar flux is generated having the supply frequency, yielding a vibrational component of the unbalanced magnetic pull with the double supply frequency.

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Die Ermittlung der Induktionsverteilung und der Radialkräfte in zweipoligen Asynchronmaschinen

Übersicht In der vorliegenden Arbeit wird auf die Verknüpfung der Unipolarflüsse mit den Radialkräften bei 2poligen Drehstromasynchronmaschinen näher eingegangen. Es wird nachgewiesen, daß sich bei statisch exzentrischer Verlagerung des Läufers in zweipoligen Drehstromasynchronmaschinen netzfrequente Unipolarflüsse ausbilden können, die Rüttelkräfte von doppelter Netzfrequenz zur Folge haben.

     

ELMEC software system for the design and investigation of electrical machines

An implementation in the ELMEC software system is presented for the method for computing the electromagnetic field in an electrical machine, which relies on the precision numerical simulation of electrodynamical processes. The basic simulation principles are stated, along with the structural features of the ELMEC software system, the use of which allows essentially improving the quality of design and optimization in the development of electrical machines.     

The application of space-vector theory to the analysis of electrical machines with space harmonics

Contents In the present paper the space vector method is described for the analysis of uniform air-gap three-phase and two-phase machines, taking into account the effects of m.m.f. space harmonics.The space vector equations are established in a natural and also in an arbitrary reference frame. It is shown that the various harmonic models can obtained without performing matrix transformations. The relationship between matrix and space vector forms is discussed. The models derived are suitable for both steady-state and transient analysis. Methods of derivation of harmonic transformations are also presented.

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Die Anwendung der Raumzeigertheorie zur Analyse elektrischer Maschinen mit räumlichen Obserwellen

Übersicht In der vorliegenden Arbeit wird die Methode der Raumzeiger zur Darstellung räumlicher Oberwellen in elektrischen Maschinen betractet. Die allgemeinen räumlichen Vektorgleichungen werden in einem natürlichen bzw. in einem beliebigen Koordinatensystem beschrieben. Es wird gezeigt, daß die verschiedenen harmonischen Modelle ohne Matrizenoperationen erhalten werden können. Die Beziehungen zwischen den Matrizen- und Raumzeiger-schreibweisen werden untersucht. Die Darstellungen der Maschine sind für die Analyse stationärer und nichtstationärer Vorgänge anwendbar. Schließlich wird die Ableitung harmonische Transformationen berücksichtigt.

     

Research on correlation between flux distribution and flux control characteristics of ferrite orthogonal core

This paper considers the flux distribution in ferrite orthogonal cores. To understand the operation of an FOC, the flux distribution must be known. We classify the flux components into four parts according to the flux pattern by using a flux distribution diagram. The flux control characteristics can be obtained by considering the component fluxes. The result of the analysis is a better understanding of the role of the component fluxes in improving the performance of the flux control characteristics.     

Representation of skew in time-stepped two-dimensionalfinite-element models of electrical machines

The authors outline a technique which enables two-dimensional finite-element analysis to be applied to skewed machines. It involves representing the continuous skewing in a series of discrete steps. Each step may be modeled in two dimensions. The model has been applied to a salient-pole synchronous generator and to a cage induction motor. It is shown that the model is successful in removing phantom slot-ripples from the current and voltage waveforms     

变频器控制在流量调节中的应用

在标准校表系统中,为了通过上位机与变频器的通信达到实时控制管道中流量的目的,结合ABB变频器的特点,在Modbus协议的基础上,给出了利用Visual Basic(VB)中的MSComm控件实现计算机与变频器串行通信的方法。该系统简单、实用,对类似的由其他类型变频器与上位机组成的控制系统的通信实现有一定的参考价值,并在实际的标准表法校表装置上得到了成功的应用,取得了满意的效果。同时也因为对变频器的控制从手动变成了上位机智能控制,给工业现场带来了方便。