A technique for the steady-State analysis of a grid-connected permanent-magnet induction Generator

This paper presents a technique by which the steady-state performance of a grid-connected permanent-magnet induction generator (PMIG) can be predicted more accurately. By applying the topological principle of duality, an equivalent circuit of the PMIG is derived that takes into consideration the core loss as well as the permanent-magnet (PM) excitation. The nonlinear parameters in the equivalent circuit are modeled using curve-fitting methods. Experimental results performed on a 2.2-kW prototype PMIG demonstrate the accuracy of the proposed technique.     

Microprocessor Control of Double Output Induction Generator, Part I: Inverter Firing Circuit

This paper investigates the design and implementation of a firing scheme using the INTEL 8086 microprocessor to control the inverter firing angle of the Variable Speed Constant Frequency Double Output Induction Generator (VSCF-DOIG). The INTEL 8086 microprocessor is used to control the firing angle of the DC-linked inverter of the VSCF-DOIG. In this system, the microprocessor computes the voltage signals from a reference voltage pot and then outputs the calculated firing angle shifting time (as opposed to deriving it from a table look-up method) to the interface timer. This gives full range control of the firing angle between 0° and 180°, and updates the phase shifting timer in each cycle based on the values of the past three cycles. The control circuit is designed for multi-tasked purpose. The hardware, software, interface, I/O, and experimental results are presented in this paper.     

Reformer faults in SOFC systems: Experimental and modeling analysis,and simulated fault maps

The effects of fuel processor faults in an solid oxide fuel cell (SOFC) system are analyzed. Focusing on a laboratory-size SOFC system, a reformer fault is investigated both experimentally and through a model; comparison between experimental and modeling results is presented and discussed. The results show that some types of reformer faults can be dangerous, because they can give rise to local thermal gradients as large as 10–20·10² K/m or more in the SOFC stack. Simulation results show that SOFC stacks employing metallic interconnects are expected to withstand faults of larger magnitude than SOFC stacks employing ceramic interconnects. Fault maps are presented and discussed, which can be the basis for the development of a fault detection and isolation (FDI) tool.     

Generator winding I2R losses and harmonic interferenceunder variable frequency operation of an HVDC unit-connectionscheme

Variable frequency operation of an HVDC unit-connection scheme may affect the generator winding I²R losses, and may cause harmonic interferences on both the AC and DC system. The purpose of this research is to determine the magnitudes of generator winding I² R losses under a certain frequency range so as to improve the efficiency of the hydro unit operation at nonrated head and output power. The generator winding additional I²R losses and harmonic interference, are investigated by using the EMTDC program and other subordinate programs. The overall study shows that the generator winding power losses will be increased as the operating frequency decreases under the condition of a fixed generator output. The magnitude of increased losses, though, will not exceed 8-10% of generator total winding I²R losses under normal system operating conditions. Harmonic interference, on the other hand, will become more severe in both the AC and DC systems, as compared to fixed frequency operation. Active or on line tuning harmonic filters may be considered for a particular variable frequency operation scheme being implemented     

柴油机故障诊断与分析

通过采集16V240ZJ型柴油机振动信号并利用小波包分解对振动信号进行消噪处理,利用频带分解技术提取振动信号的特征值向量,应用神经网络实现柴油机自适应的故障诊断。     

Ten MVA air-gap armature winding: thermal, structural anddielectric results

This paper describes the armature winding built as part of MIT's 10 MVA superconducting generator project. The winding has a helical winding form, is an air-gap winding having no iron teeth in the active region, employs a limited voltage gradient insulation scheme and is cooled by an insulating fluid. Structurally, the winding employs bonded joints between the conductors and structural tubes, which are of filament-wound fiber-reinforced plastic. Preliminary tests indicated that thermal performance of this winding was satisfactory. On the other hand, the winding suffered a catastrophic insulation failure after only a short time at high voltage. The resulting fault gave the structural system of the armature winding (and the rest of the machine) a good test. In this paper the authors review the major aspects of the design of the winding, describe the thermal tests and then tell of the insulation failure. They can, at best, speculate about the cause of that failure, but they can, on the basis of this experience, make recommendations for further development of machines of this type     

太阳能热水器电热带失火原因分析及使用方法

介绍了电热带的主要发热原理、性能特点和测试要求,以及自限式电热带在解决太阳能热水器上下水管冻堵方面的使用情况,对自限温电热带失火的模拟试验进行分析,重点对使用过程中的安装方式、注意细则做了描述.     

某客车噪声故障分析及优化

针对某客车的噪声异常问题,通过试验,查找并确定故障源,分析故障产生机理并进行优化。噪声异常客车驾驶室存在怠速拍频,原因为空气压缩机1.12阶次与发动机曲轴1.00阶次能量干涉,导致振动、噪声异常,舒适度降低;客车内存在显著打鼓声,原因为进气系统设计不合理及空压机激励大,导致的进气系统声腔共振。通过更换离合器降低1.00阶次异常振动,消除了室内拍频;通过增加进气消音器,降低了激励源的能量,消除了打鼓声。优化后进行试验验证,整车噪声、振动、声振粗糙度(noise,vibration,harshness,NVH)水平得到明显提升,主观感受整车舒适性得到极大改善,为同类NVH问题的解决提供了参考。     

牵引电动机主、附极绕组线圈松动原因浅析

从环境、保养、检修以及设计等方面详细分析了牵引电动机主、附极绕组线圈松动的原因和危害并提出改进措施.     

Dynamic response analysis of wind turbines under blade pitch system fault,grid loss,and shutdown events

This study focuses on the dynamic responses of land‐based and floating wind turbines under blade pitch system fault and emergency shutdown conditions. The NREL 5 MW turbine is studied. A hydraulic pitch system is considered, and the faults under study are events with a seized blade or a blade running out of control. Emergency shutdown is defined as a fast pitch‐to‐feather maneuver of the blades. Load cases with power production and grid fault with ensuing shutdown are also analysed for comparison. The fault scenarios and the blades' fast pitching activity are simulated using HAWC2 through external Dynamic Link Libraries. On the basis of the time‐domain simulations, the response characteristics of the land‐based and the floating turbines in the four design load cases are compared. The load effects from the fault conditions are compared with the operational cases. Strong system dynamics and resonant responses, such as the tower elastic mode and the yaw resonant response, are elicited during shutdown. If the pitch system has a fault and one blade is hindered from normal pitching, the uneven load distribution of the blades leads to large structural and motion responses. For both turbines, the response maxima vary cyclically with the instantaneous azimuth when the blades start pitching to feather. For the floating wind turbine, the interaction of waves and wind also affects the results. The effect of the pitch rate during shutdown is analysed. The responses of the land‐based turbine in grid loss and shutdown conditions are proportional to the pitch rate, whereas decreased sensitivity is found in the cases with pitch system faults. For the floating turbine, the effect of the pitch rate is small, and reduced pitch and yaw motion extremes are observed as the pitch rate increases. Copyright © 2013 John Wiley & Sons, Ltd.     

Small Signals, Large Signals, and Saturation in Generator Modeling

Test and analytic results from recent EPRI-sponsored programs are organized to explain insights into generator modeling. It is shown how small-signal tests and analysis are related to the nonlinear incremental properties of rotor iron. Changes in rotor circuit topology caused by rotation are identified. The large-signal response of rotor circuits is differentiated from the small-signal response. These effects, customarily lumped under the term ``saturation,' are separated and differentiated.     

Transient pattern analysis for fault detection and diagnosis of HVAC systems

Modern building HVAC systems are complex and consist of a large number of interconnected sub-systems and components. In the event of a fault, it becomes very difficult for the operator to locate and isolate the faulty component in such large systems using conventional fault detection methods. In this study, transient pattern analysis is explored as a tool for fault detection and diagnosis of an HVAC system. Several tests involving different fault replications were conducted in an environmental chamber test facility. The results show that the evolution of fault residuals forms clear and distinct patterns that can be used to isolate faults. It was found that the time needed to reach steady state for a typical building HVAC system is at least 50–60 min. This means incorrect diagnosis of faults can happen during online monitoring if the transient pattern responses are not considered in the fault detection and diagnosis analysis.     

直驱与双馈风电机组的故障特性对比分析

基于PSCAD软件建立了直驱永磁同步风电机组(D-PMSG)和双馈感应式风电机组(DFIG)的暂态仿真模型,对比分析了D-PMSG和DFIG风电机组在单相、三相短路故障下的故障特性。仿真结果表明:D-PMSG在电网发生故障时能向电网提供几乎恒定的持续故障电流和一定的无功支持;DFIG在电网发生故障时能提供持续的故障电流,但故障电流呈衰减特性。     

Finite-element time-step coupled Generator,Load, AVR, and brushless exciter modeling

This paper presents a model of a small brushless generating set that incorporates independently validated subsystem models. The new model links: a finite-element and time-stepping circuit model of the main alternator and load, a real-time model of the analog automatic voltage regulator (AVR) and a model based on the self and mutual inductances of the exciter machine along with the rectifier diode bridge. The composite model can be used to study the transient and steady-state performance of the whole generating set under different load conditions including synchronous operation in parallel with mains. The predicted transient behavior of an isolated generating set when subjected to various loads is presented, the implications with regard to induction motor starting are discussed, and voltage recovery and the function of each component are demonstrated.     

主电路瞬间接地故障的原因分析及预防措施

分析了电传动内燃机车主电路瞬间接地的故障原因,提出了判断方法和防止措施。     

空冷机组机炉电匹配的探讨

国产机组炉电产品均已形成系列，但空冷机组机炉电的匹配没有统一规定，可谓各抒己见。根据山西电力勘测设计院近期设计的空冷机组机炉电匹配情况，论述空冷汽轮机的主要技术条件，提出机炉电匹配的建议，供编写空冷机组主设备招标文件时参考。表5参5     

一起DF4型机车冷却水系统故障的原因分析及处理

1 故障现象 2004年11月20日,我段DF4型7147号机车发生一起冷却水系统故障,其故障现象为:起机后,特别是提转速后膨胀水箱溢水,一室的暖风机热,二室的暖风机不热.经测量得知高温水泵出水口处没有水压,但高温散热器组温度却较高,打开高温散热器组排气阀,不排水却向里吸气,两室的暖风机排气口处也同样不出水而向里吸气.     

CIT400检测车的高阻抗试验故障原因分析及预防措施

针对CIT400检测车的高阻抗试验故障,对其转向架绝缘点及电流路径进行分析,给出了故障查找的一般方法,并提出了预防改进措施。