铜阻变化法测量电动机绕组温升准确性的探讨

间接洲量电动机绕组温升是指分别测量绕组冷热态铜阻,从而推算出绕组温升.由于不能即时测量热态铜阻,因此,随着测量时间的滞后会影响测量的准确性.本文着重探讨测试转子绕组的温升时如何保证测量结果的准确性.通过对串激电机的测试实例分析,介绍两种不同的测试方法,分析两种方法的优缺点和可靠性.     

三相异步电动机热试验直接负载法与叠频法的比对

电流经过三相异步电动机定子绕组时,不仅会产生旋转磁场带动转子转动,而且也会产生热量,使定子绕组发热,在电动机运行达到稳定时,这部分热量与环境温度的差值便是电动机的温升。温升是电机性能考核中的重要指标。根据国家标准GB/T 1032—2012 《三相异步电动机试验方法》,温升可按热试验方法测得。其中,热试验的方法分为直接负载法和间接法。通过试验对比直接负载法跟间接法中定子叠频法中的现象,记录试验数据,并对差异进行了分析。     

小李学异步电动机(二) 第一章 异步电动机的结构与原理

1.3异步电动机的工作原理1.3.1异步电动机的旋转原理(1)转子得到电流提起异步电动机的工作原理,小李显得很有信心,他拿出了事先画好的图,说:"旋转磁动势被静止着的转子绕组切割,转子绕组中将产生感应电动势,又因为转子绕组是自成回路的,所以同时产生了感应电流,如图1-18a所示。感应电动势和电流的方向由右手定则来判定,     

绕组温升测量系统设计

本文介绍了绕组温升测量的方法,就如何设计带电绕组温升测量系统进行了探讨,并给出了一个具体设计方案.     

基于神经网络的电动机温升智能保护设计

本文调查了国内外电动机各种保护方法和各类保护装置的研究发展状况,结合实际情况,提出了一种通过人工神经网络预测电机绕组温升的方案,由PC机通过RS485总线实时读取下位机采集的电机运行参数,进行温升预测,并将预测结果传输回下位机,从而实现了对电动机长期稳定负载运行的过载保护。     

简析电阻法测量变压器绕组温升

变压器温升测试已成为对各类电气产品的安全考核必不可少的项目,尤其是医用电气设备,而电阻法在测量变压器绕组温升的试验中有着深远的意义。本文以一次比对试验为例,介绍了采用电阻法测量变压器绕组温升的具体试验步骤和注意事项。     

充电与发电及其设备

0622791高速电机的设计特点及相关技术研究[刊,中]/王凤翔//沈阳工业大学学报．—2006,28(3)．—258-264(C)简要介绍了高速电动机和发电机的结构类型、设计特点、关键技术及研究现状。以高速永磁电机为例,重点阐述了高速转子的电磁与结构设计、转子强度与刚度分析、永磁体的保护方法、定子铁心与绕组的结构设计与电磁性能计算、高频与高速附加损耗计算、温升计算与冷却散热方式。此外还简要介绍了高速磁悬浮轴承的结构原理与控制方法、高速发电机和电动机的     

铜包铝线绕组温升测量K值的计算方法

针对目前广泛使用的铜包铝线绕组,在温升测量和计算时K值不统一的现状,提出了一种按照体积比的加权平均计算方法,可准确计算出绕组导体温升,对其他复合材料绕组的K值计算也有一定的借鉴意义.     

变压器绕组温升测试及数据处理方法

该文详述了采用电阻法测量变压器绕组温升的方法及过程,并对断电瞬时电阻值R2的求得,对比了曲线拟合计算方法和MATLAB编程方法.经对比可得,MATLAB编程方法更为简单、便捷、准确,为变压器绕组温升测量的数据处理,提供了另一种可行的途径.     

绕组温升测量方法研究

本文介绍家用电器中的绕组温升测量的一般方法，提出认真研究的重要性。     

A Study of Influence of Configurations of the Windings on the Performance of Single Phase Induction Motor with Capacitor Start

The single phase induction motors needs two stator windings to produce rotating magnetic field : one main winding and the other auxiliary winding. The aim of the auxiliary winding is to create the rotating electromagnetic field when the machine is started-up and is afterwards turned off, generally through the centrifugal switch coupled together with the shaft of the machine rotor. The main purpose of this document is to evaluate the influence that the two windings have on the external characteristics of the single phase induction motor . For this purpose , two different kinds of windings were carried out and simulated, with the proposal to obtain some benefits. The main winding and the auxiliary winding were prepared and mounted on a prototype. The simulation was done via software based FEM , to make the extraction and results analysis possible. This results are shown at the end this document.     

A novel Variable-Reluctance Resolver proposal and its performance analysis under healthy and eccentric cases

A Variable-Reluctance resolver (VR-Resolver) with a novel structure is proposed in this paper as an absolute position sensor, where two possible structures are analyzed. The signals and excitation windings are located on the stator. Hence the slip rings are eliminated in the rotor. The rotor is considered by slot/teeth configuration so the rotor is shaped in a simple variable reluctance structure with a low sensitivity to the manufacturing tolerance. The excitation winding is wound in toroidal configuration that leads to having a smaller fill factor as well as turns can be considered for the windings. Maximum position error (MPE) is evaluated for the proposed resolvers in both healthy and eccentric cases. Therefore, the resolvers performance and their sensitivity to the eccentricity fault are evaluated. A flexible Magnetic Equivalent Circuit (MEC) with adjustable accuracy is used for modeling thanks to its capability and shorter processing time compared to the Finite-Element Method (FEM), where different cases are analyzed by a unique MEC model. Finally, comparison between the MEC and FEM-based results as well as experimental tests are presented to show effeteness of the proposed resolver as an accurate absolute position sensor for industries applications.     

Active and reactive power control for doubly-fed wound rotorinduction generator

A power control system for a doubly fed wound rotor induction generator has been developed. This power control system applies a control method using a rotating reference frame fixed on the gap flux of the generator, and can control active and reactive power independently and stably. The characteristics of the control system have been proved by experiment. Harmonic currents fed to the rotor windings are transmitted to the stator winding changing its frequency. The transmitting characteristics of the harmonic currents have been analyzed and verified by experiments     

Winding distribution effects on induction motor rotor fault diagnosis

The sidebands around stator currents harmonics as a potential tool for supporting the diagnosis of rotor faults in induction motors are analyzed in this paper. The presence of broken bars introduces high frequency components in the machine currents spectrum in addition to the characteristic sidebands around the fundamental component. These additional components are due to the interaction between, rotor asymmetry and either the voltage harmonics, or winding distribution, or rotor slots. In particular, the components at frequencies near to fifth and seventh harmonics, produced by the interaction between the rotor faults and the harmonics of the spatial distribution of stator windings, are analyzed in this work. A multiple coupled circuit model of the induction motor is used to evaluate the sensitivity of these components for different stator winding configurations, load level, supply voltage conditions, and different number of broken bars. Simulation results showed that a particular analyzed component near to fifth harmonic depends mainly on fifth harmonic of winding distribution, which remains almost constant for most common distributions. Therefore, it is expected that this component should be found in most motors with broken bars. Finally, experimental laboratory results and two industrial cases that validate the analysis are presented.     

Total Airgap Flux Minimization in Dual Stator Winding Induction Machines

Multiphase machines are gaining attention in specific applications due to their increased reliability and the possibility to split the power between more than one inverter. Dual stator winding machines can be seen under certain conditions as two independent induction machines coupled by the rotor. To ensure control independence of both windings, airgap flux saturation must be avoided. Proper flux synchronization of both windings is required to achieve this goal while maximizing the torque per ampere ratio of the machine. The conditions to obtain proper orientation of the fluxes are discussed in this paper, and the inverter control scheme to perform such orientation is developed.     

Mechanical Loss of HTS Coils Reinforced With Negative Thermal Expansion Fiber Materials

High-$T_ c$superconducting (HTS) coils with various types of reinforcement are investigated with respect to the reduction of mechanical loss. The total AC loss of the coils is measured under an external DC magnetic field at liquid nitrogen temperature, the reduction of the mechanical loss components are estimated. Tensioned stainless-steel tape is found to be the most effective for reducing the mechanical loss by improving the rigidity of the entire winding. The mechanical loss of the HTS coils is reduced by reinforcement with a bobbin of negative thermal expansion material, although the hoop stress caused by radial expansion of the bobbin is absorbed by a small number of winding turns. Bobbins of negative thermal expansion material are therefore unsuitable for pancake-type coils or multilayer windings, but can be expected to realize substantial reductions in mechanical loss for single-layer windings or thin solenoids.     

一种新颖的双三相感应电机缺相运行矢量控制

双三相感应电机的绕组开路后,运用传统的旋转坐标变换,不能实现转子磁场定向矢量控制。本文推导出不对称绕组结构的解耦旋转坐标变换,并提出了一种基于不对称绕组结构的转子磁场定向矢量控制新颖策略,运用PI调节器,使得定子侧谐波电流最小化,降低定子侧谐波损耗。在MATLAB MATLAB/Simulink仿真软件下,建立相应的仿真模型,仿真结果验证本文所提出控制策略的正确性和有效性。     

Modeling of permanent magnet motor drives

Research has indicated that the permanent magnet motor drives, which include the permanent magnet synchronous motor (PMSM) and the brushless DC motor (BDCM) could become serious competitors to the induction motor for servo applications. The PMSM has a sinusoidal back EMF and requires sinusoidal stator currents to produce constant torque while the BDCM has a trapezoidal back EMF and requires rectangular stator currents to produce constant torque. The PMSM is very similar to the wound rotor synchronous machine except that the PMSM that is used for servo applications tends not to have any damper windings and excitation is provided by a permanent magnet instead of a field winding. Hence the d, q model of the PMSM can be derived from the well-known model of the synchronous machine with the equations of the damper windings and field current dynamics removed. Because of the nonsinusoidal variation of the mutual inductances between the stator and rotor in the BDCM, it is also shown that no particular advantage exists in transforming the abc equations of the BCDM to the d, q frame. Hence the solution of the original abc equations is proposed for the BDCM     

Modeling and Real-Time Simulation of Internal Faults in Synchronous Generators With Parallel-Connected Windings

In large synchronous generators, the stator windings are usually parallel-connected in order to increase the machine current capacity. In analysis and modeling, the parallel windings are usually lumped into one equivalent stator winding since equal currents flow in these windings. However, when an internal fault occurs in the windings, the symmetry between the parallel windings is broken and different currents will flow in the parallel windings since unsymmetrical magnetic linkage may exist between the stator windings. The aim of this paper is to present a simulation model to investigate the internal fault currents of large synchronous generators with parallel-connected windings. This model is based on a modified winding function theory that takes into account all space harmonics. Moreover, the calculation of the machine inductances is made easier by the use of the machine electrical parameters instead of the geometrical ones. The simulation results illustrate the existence of different currents in parallel windings in the case of internal faults. Results are given for an implementation of the internal fault model in a real-time simulator of large power networks