NON-TRANSFORMATIONAL MATRIX ANALYSIS OF ELECTRICAL MACHINERY

ABSTRACT

The general theory of electrical machines based on space phasor representation of space waves is explained. Harmonics of both the winding distribution and air-gap irregularities are taken into account for any winding asymmetry. Complex winding factors, symmetrical components of instantaneous values, and the winding inductances referring to the air-gap field are obtained during derivation of equation without the use of transformations. All quantities involved are physically defined. The method represents a common basis for analysis and design.     

TRANSIENTS IN SUPERCONDUCTING ALTERNATORS WITH TORQUE COMPENSATING SHELLS

ABSTRACT

In this machine the torque is not transmitted mechanically to the field winding but by an asynchronous link. The field winding is free to rotate inside the driving shaft, which acts as the squirrel cage of an induction motor. In the steady state the field winding turns at synchronous speed and the driving shaft slightly faster. During a transient the shaft acts as an electromagnetic shell protecting the low temperature parts of the cryostat from high torques and the superconducting coil from varying magnetic fields. In this paper the steady-state running, the fault torques, the critical clearing time, the steady state stability, and the losses in cold metallic parts, are compared with those of a classical superconducting alternator.     

电力变压器绕组电气参数对绕组变形的全局灵敏度分析

目前已有利用变压器绕组电气参数检测绕组变形的方法,但对电气参数变化与绕组变形之间的联系的研究还不够深入。为此,提出一种分析绕组电气参数对不同种类变形的全局灵敏度方法。该方法首先采用响应面法,建立显式化的绕组电感电容参数响应面模型。然后基于蒙特卡罗的Sobol’全局灵敏度分析法计算各电气参数对不同变形种类的全局灵敏度,分析各电气参数反映不同类型绕组变形的灵敏度。进一步分析其变异系数,以比较不同电气参数针对同一类型绕组形变的灵敏度。以某型号变压器为例进行了分析,分析结果表明利用本方法可以揭示各电气参数与绕组变形种类的内在联系。依据结果可将灵敏度较高的参数信息引入变形判据,为基于电气参数的绕组变形检测提供了理论基础和新的思路。     

Rotor/Stator Internal Phase to Phase Fault Detection in Three-Phase Wound Rotor Induction Machines

Abstract

This paper presents a novel method based on Magnetic Equivalent Circuit (MEC) to model the wound rotor three-phase induction machine under healthy and faulty conditions. Different parameters of machine such as the number of poles, number of slots, winding configuration and dimension can be selected based on designed properties of a given machine. Internal phase to phase fault is also detected by stator current signature analysis in dq frame. Saturation effect is modeled by a tunable function as well as the core nonlinearity characteristic is considered. Finally, Finite Element Method (FEM) is used to evaluate the accuracy of the proposed MEC model. Short computational time of MEC method shows that this model is suitable for electrical machine modeling and analysis.     

POWER ELECTRONICS CONTROL OF RELUCTANCE SERIES MOTOR (RSM) FOR DIRECT AXLE TRACTION

ABSTRACT

Direct–axle traction may be achieved with high-specific torque (5–6 Nm/kg), low—loss electric motors. Given the rotor vibration in traction applications, a winding–less rotor would be preferable. The reluctance series motor (RSM( with electronic commutation having a rotor made of longitudinal laminations with insulations spacers is considered here for the scope. The power electronics for commutation of phases and speed control is proposed and tested on a laboratory model. The results are very encouraging but further performance/costs investigations are required before the RSM is established as a practical solution for direct-axle traction     

基于电压、电流不平衡度差值的干式变压器匝间短路故障识别方法

干式变压器绕组发生轻微匝间短路时,相电压、相电流等电气量变化甚微,不能作为表征匝间短路故障的敏感特征量,导致相应保护措施缺失,运行过程中设备烧毁事故时有发生。通过建立干式变压器“场-路”耦合仿真模型,利用实际试验和工程计算获取的状态参数,验证模型的准确性。通过建立和分析其绕组匝间短路故障数学模型,提取相电压、相电流不平衡度标幺值的差值,作为判断匝间短路故障的特征量。通过仿真分析不同工况下其绕组发生匝间短路故障时不同电气量的变化情况,论证了所提新故障特征量不仅能提前感知绕组匝间短路故障,而且能够克服固有的三相不对称及不平衡运行带来的影响,有效性、灵敏性兼顾,为实时监测干式变压器绕组匝间绝缘状态提供一种新方法。     

COMPACT PERMANENT-MAGNET MACHINES

ABSTRACT

The availability of new high-field permanent-magnet materials has created opportunities for novel topologies of electrical machines with advantageous characteristics such as high efficiency and good power/weight ratio. A disc-type arrangement, with slotless winding and axially-directed flux in the air gap, has particularly short axial length and is well suited for system integration as either generator or motor. Applications include auxiliary power units, electric vehicle drives and wind power generation.     

Adjustable magnetic gear

A mathematical interpretation of a combined electromechanical device possessing the properties of a synchronous machine connected to a frequency converter and of a magnetic gear with a variable reduction factor is considered. The stator winding of the synchronous machine is concentrated (tooth winding), and its spatial period covers the full number of teeth z. An expression for the frequency response of the magnetomotive force (MMF) of the tooth winding was obtained. In the variant under consideration (z = 36), the fundamental harmonic of the magnetic field, which sets the number of stator pole pairs, is v = p = 17. The MMF of the magnets of the internal rotor is represented as a Fourier series. Formulas are given making it possible to calculate the magnetic fields in two air gaps of the magnetic gear caused by the stator current and magnets of a high-speed rotor (using the method of specific magnetic conductivity). The electromagnetic torques of the gear shafts are calculated by the stretch method. The electromagnetic torque caused by the stator winding is determined on the basis of the instantaneous values of the EMF of rotation and transformation of each winding coil without using the winding coefficients. A differential equation system for calculating the transient processes in three channels of a wind-power plant is obtained: in two mechanical channels and in one electrical channel. A closed system with a PID controller is proposed making it possible to stabilize the rotational speed of the electric generator of a wind-power plant with a variable wind speed.     

The influence of synthesis temperature on structure properties of SrTiO3 ferroelectric films

Abstract

The results of structure investigations of SrTiO₃ films depending on synthesis temperature are presented and electrical characteristics of 4-electrode planar capacitors based on prepared films are investigated. Finally, the technological conditions of high structure quality SrTiO₃ films preparation are determined. SrTiO₃ films prepared under these conditions possess electrical characteristics sufficient for room temperature MW applications in a wide frequency range., Keywords: RF magnetron sputtering, SrTiO₃     

无机复合绝缘扁绕组线的高温环境老化性能研究

对自主研制的耐高温无机复合绝缘扁绕组线的常规性能和高温老化性能进行研究,初步探索高温对无机复合绝缘扁绕组线性能的影响。经测试,扁绕组线的无机复合绝缘材料热失重较小。在600℃温度下老化,无机复合绝缘扁绕组线的击穿电压和绝缘电阻随老化时间的增加先降低,后趋于稳定;导体电阻最终增加率为0.30%。试验结果表明,无机复合绝缘扁绕组线在高温老化后具有较好的耐热和电气稳定性。     

SPLIT-WINDING STARTING OF A SINGLE-PHASE INDUCTION MOTOR

Abstract

Results of investigation of starting a single-phase induction motor having a single stator winding and using normal stator and rotor punchings are presented in this paper. Theoretical and experimental studies show that the motor requires less copper for its stator winding compared to a split-phase motor and the overall starting performance is very satisfactory.     

A NOVEL MODEL FOR SINGLE-FRAME CASCADED INDUCTION MACHINE HAVING A MULTICIRCUIT ROTOR WINDING

ABSTRACT

This paper presents a new steady-state circuit model for a Single-Frame Cascaded Induction Machine (SFCIM) having a multicircuit single-layer bar rotor winding. The rotor winding, which consists of a large number of mostly mutually coupled circuits is complex. An impedance matrix containing parameters which can be calculated relatively simply, is used to represent the coupling of the rotor winding to stator windings. Theoretical results obtained using this model are presented, together with experimental results.     

CALCULATION OF THE LOCKED ROTOR CURRENTS AND TORQUE IN INDUCTION MACHINES

ABSTRACT

The analysis of certain end-winding vibration problems requires an accurate knowledge of the transient currents in an induction motor during the early part of the start-up period where the time rates of change of current are the highest. This paper details the derivation of expressions for the winding currents assuming that the machine remains at rest during the period of interest. Under these conditions, the currents are shown to contain three time dependent components, one of which is oscillatory, the remaining two being damped exponentials. The rates of decay of the exponential components are particularly important to some aspects of the vibration problem and they are shown to be dependent on the winding resistances and inductances and also upon the degree of coupling between stator and rotor.     

ANALYSIS OF THE M/N WINDING ASYNCHRONOUS MACHINE WITH SPACE HARMONICS USING SYMMETRICAL COMPONENTS

ABSTRACT

This paper is concerned with the analysis of the asynchronous. machines with m symmetrical stator windings and a rotor of cage type which consists of n symmetrically distributed bars. The analysis is performed in the presence of space harmonics. Considering the relation between any sequence of symmetrical components related to unbalanced voltage supply, the possibly established space harmonics can be assigned. The m/n wielding machine voltage equations are presented in phase coordinate form in order to apply a transformation by symmetrical components. Sufficient conditions are presented in order to express these equations in the form of linear differential equations with constant coefficients. The suggested method is able to include large numbers of space harmonics. The transformation with the help of symmetrical components here will divide the complete set into n separate subsets when it is applied to the rotor quantities. The equivalent symmetrical component model of the m/n winding machine will make the stator/rotor space harmonics interactions more understandable.

It is also possible to discuss the problem of obtaining linear voltage differential equations by simpler method.     

A NEW PHILOSOPHY FOR SPEED-CHANGE INDUCTION MOTORS

ABSTRACT

A new concept termed ‘phase shift modification’ for the design of two-speed single-winding three-phase induction motors is discussed. Designs are classified based on the chosen phase-spread on the initial and final pole scales. A method for improving the layer factor on the final-pole connection without affecting the winding factor for the initial pole connection is also presented. Although the concept is illustrated with respect to a 8/10 pole-combination it is equally applicable to any other pole-ratio.     

低压轴向双分裂变压器半穿越状态下绕组电流及温升计算

利用Magnet软件以及经典理论公式,分别对半穿越运行状态下高压绕组上、下两个支路的电流进行了计算,利用TranCalc软件对该工况下绕组温升进行了计算,并与试验数据进行了对比。     

水轮发电机定子绕组不对称支路电磁参数计算模型

为了探讨水轮发电机定子绕组不对称支路参数的计算问题,根据交流电机多回路理论,建立了绕组不对称支路参数计算的数学模型,给出了应用有限元方法计算绕组不对称支路参数的通用方法。通过对样机计算表明,该方法可用于任意线圈组合的电磁参数计算,且计算结果准确;绕组各支路电磁参数的不一致完全体现了各支路不对称程度,不对称支路间的环流损耗随绕组不对称度的增大呈指数关系增长;采用有限元方法进行不对称绕组支路电磁参数的计算,为支路不对称绕组的设计提供了依据,同时也为发电机绕组故障分析打下了良好的理论基础     

绕组分布对永磁伺服电机电磁场与温度场影响的研究

永磁伺服电机采用不同的绕组分布形式对电机的电磁场和温度场均会产生一定的影响,文章以一台8极10 k W的永磁伺服电机为例,建立不同绕组分布的永磁伺服电机模型,对比分析电机不同绕组分布对电磁场和温度场的影响。首先,采用时步有限元计算方法对永磁伺服电机谐波磁场变化进行分析,基于傅里叶谐波分解理论给出电机内各次谐波的变化情况。然后,结合电机转矩脉动系数的分析对不同绕组分布下的永磁电机转矩脉动进行研究,给出电机转矩波动随绕组分布形式的变化规律;其次对电机各损耗的变化规律进行分析,并揭示电机内谐波磁场对电机损耗的影响机理。在损耗研究的基础之上,进一步对不同绕组分布下的永磁伺服电机绕组温度与永磁体温度进行分析,给出不同绕组分布下的温度变化规律。最后,结合有限元计算结果及相关实验验证计算分析的准确性,并进一步揭示双层绕组分布在永磁伺服电机提高电机综合性能方面的作用。     

变压器用绕组温控仪原理及应用

目前,对变压器绕组温度的测量主要是通过热模拟测量方法,绕组温度袁在油温表的基础上配备一台电流匹配器和电热元件,通过温度叠加来反映变压器绕组温度。这种测温方法具有简单、适用的特点。就绕组温控仪及其配套匹配器的入网检定和温度控制节点的整定进行了讨论,对绕组温控仪的实际使用有一定指导意义。