抽水蓄能发电电动机转子稳定性研究

转子是水轮发电机中变换能量和传递扭矩的核心部件。针对转速相对较高、工况转换复杂的抽水蓄能机组,转子的稳定性研究是一项重点工作。良好的转子结构和性能可以避免机组投运后转子部件出现重大电气以及机械事故。随着抽水蓄能机组向高转速、大容量方向发展,转子的设计和检修难度也越来越大。本文详细介绍了溧阳抽水蓄能发电电动机转子结构特征,重点分析研究电磁性能、机械性能和绝缘性能。运行性能表明发电电动机转子结构合理、运行稳定。本文对类似蓄能电机转子的设计与研究具有指导意义。     

A systematic approach to design and operation of a doubly fed induction generator

The doubly fed induction generator (DFIG) is currently one of the most common topologies employed for wind turbine generators (WTGs). The system has the benefit of a back-to-back voltage sourced converter (VSC) of reduced rating, due to its connection to the rotor windings. This paper considers the impact of mechanical and electrical parameters on the kVA requirements of the two VSCs, which together with the dc link capacitor serve as the rotor winding's power supply. This topology is contrasted with alternatives utilizing a diode rectifier-voltage sourced inverter pair and a set of design curves are generated. In addition to steady-state analysis, an operating strategy for reactive power allocation management is proposed. The theoretical considerations are validated with results obtained from representation of the system in an electromagnetic transient program.     

Electromagnetic and mechanical design aspects of a high-speed solid-rotor induction machine with no separate copper electric circuit in the megawatt range

The most crucial electro-magnetic and mechanical design aspects of an integrated electrical-motor–gas-compressor system in high speed and high power operation are presented. The electric motor type considered is a solid-rotor induction motor with properties of which are particularly well suited in high-speed operation. The effect of the electro-magnetic material properties of the solid rotor core material on the performance of the machine is discussed. Guidelines to improve the performance of the solid-rotor induction motor are given. Thermal design aspects of a solid-rotor induction motor are presented. The mechanical properties of a solid rotor are discussed. Bearing arrangements as well as the rotor dynamics of an integrated system are presented.     

转子磁路结构对永磁同步电动机性能的影响

分别对采用U、W型永磁转子结构的15kW永磁同步电动机进行设计,利用场路结合法计算不同转子结构电机参数。使用Matlab/Simulink仿真软件对两种转子磁路结构的起动性能仿真,分析了不同转子结构对永磁同步电动机性能的影响。所得结论对采用U、W型转子结构的永磁同步电动机设计具有一定参考价值。     

13.2 MW海上超导直驱风力发电机设计

超导电机技术为减小大型直驱风力发电机体积、质量和成本提供了一种有效途径。提出了一种海上超导直驱风力发电机系统,其定子采用低温超导线圈产生励磁磁场,转子为常规的铜制电枢绕组。首先介绍了该电机的主要参数以及拓扑结构的选择,并分析了超导电机电磁设计过程中所需考虑的关键问题;之后介绍了超导电机的定转子设计方案,包括电磁设计、机械结构、转子风冷系统、超导定子的低温系统以及制冷系统等;最后估算了所设计超导电机的质量以及成本,并与相同功率等级的永磁直驱风力发电机进行了对比,结果表明所设计的超导电机的质量比永磁直驱风力发电机质量减轻约46%,而其初始材料成本仅为永磁直驱电机的71%。     

Optimization of Flux Barriers of Line-start Synchronous Reluctance Motors for Transient- and Steady-state Operation

Abstract—In this work, an electromagnetic design procedure for a line-start synchronous reluctance motor is presented, and the main considerations are highlighted. To improve the steady-state performance of this motor, the geometry of the flux barriers as well as their number are optimized using an automatic optimization algorithm. For this purpose, two types of flux barriers, arc shaped and trapezoidal shaped, are formulated and studied by finite-element analysis. Analyzing the average cage torque during synchronization, effectiveness of the dq-axis rotor resistances on successful synchronization is discussed. To validate the results of this analysis, dynamic simulations are used, and the impact of the dq-axis rotor resistances on synchronization is investigated. In addition, the effect of the rotor bar position on the value of the dq-axis rotor resistances is discussed and analyzed by finite-element analysis. Finally, the impact of small pieces of permanent magnet in the flux barriers is studied. It is shown that against the permanent magnet-assisted motor, permanent magnets always enhance the motor performance; the steady-state characteristic of the line-start permanent magnet assisted motor could be deteriorated by permanent magnet.     

Multiphase Flux-Switching Permanent-Magnet Brushless Machine for Aerospace Application

Flux-switching permanent-magnet (FSPM) brushless machines have attracted considerable interest as a candidate machine technology for applications requiring high torque density and robust rotors. To date, published findings have focused exclusively on single- and three-phase FSPM machines. This paper investigates FSPM brushless machines of higher phase numbers by means of a detailed comparison of the electromagnetic performances of three-, four-, five-, and six-phase variants within the specific context of aerospace machine. Machines having both all poles and alternate poles wound are investigated, with the latter offering scope to reduce mutual coupling between phases so as to achieve improved fault tolerance. The finite-element (FE)-predicted electromagnetic performances in both machines, such as electromotive force waveform, winding inductance, cogging torque, and static torque, are validated by the experiments made on a small-scale five-phase FSPM machine. The nature of the machine specification requires that consideration must be given to mechanical stress in the rotor and the tradeoff with electromagnetic design considerations, notably the degree of rotor saliency which can be incorporated. Therefore, a mechanical FE study of the rotor mechanical stresses of multiphase FSPM machines is also comparatively assessed.      

Closed-form analysis of adjustable-speed drive performance under input-voltage unbalance and sag conditions

Voltage unbalance or sag conditions generated by the line excitation can cause the input rectifier stage of an adjustable-speed drive (ASD) to enter single-phase rectifier operation. This degradation of the input power quality can have a significant negative impact on the induction-machine performance characteristics. This paper provides an approximate closed-form analysis of the impact of line-voltage sags and unbalance on the induction-machine phase voltages, currents, and torque pulsations for a general-purpose ASD consisting of a three-phase diode bridge rectifier, a dc link, and a pulsewidth modulation (PWM) inverter delivering constant volts-per-hertz excitation. Attention is focused on the impact of the dominant second harmonic of the line frequency, which appears in the dc link voltage during the sag/unbalance conditions, neglecting the impact of the other higher order harmonics. In addition to the closed-form analytical results that assume constant rotor speed, both simulation and experimental results are presented, which confirm the key analytical results, including the dominance of the second harmonic in the resulting torque pulsations. The analytical results can be used as a valuable design tool to rapidly evaluate the approximate impact of unbalance/sag conditions on ASD machine performance.     

Design, fabrication, back-to-back test of 14200-hp two-polecylindrical-rotor synchronous motor for ASD application

This paper describes the design aspects, fabrication, and testing of a 14200-hp two-pole cylindrical-rotor synchronous motor used with a load-commutated inverter (LCI) adjustable-speed drive (ASD) to drive a refrigeration compressor for a refinery alkylation plant. The motor design aspects include extensive finite-difference analysis of the rotor cage assembly and laboratory bench testing of a wedge assembly to verify finite-difference analysis results prior to fabrication. Torsional and harmonic analysis results are also presented. Special considerations are discussed regarding rotor heating due to harmonic currents and mitigation methods for handling the harmonic currents and heating. Mechanical design aspects are presented of the rotor cage, including rotor slot design, wedge, and end ring assembly. Two motors and drives were built, for companion projects, allowing for verification of the rotor-cage assembly by a back-to-back (BTB) test. Test preparation, setup and results are presented, including rotor temperature mapping, vibration data and torsional results. Finally, test results are compared with calculated values     

Two-Phase SRM With Flux-Reversal-Free Stator: Concept, Analysis, Design, and Experimental Verification

The demand for high-efficiency electric motor drives at low cost is increasing, particularly, in high-volume applications, such as household appliances. Single- and two-phase machines are viable under such constraints. Between them, two-phase switched reluctance motor drives are preferred from the viewpoint of performance. This paper presents a novel two-phase switched reluctance machine (TPSRM) that is conceived for high-efficiency operation and full-load starting performance for any initial rotor position. The principle of operation of the proposed TPSRM and its unique features such as the flux-reversal-free stator for reducing core losses, the utilization of only two thirds of the stator core for each phase operation, and the resulting low noise are presented. The machine is analyzed with the 2-D finite-element analysis method. Self-starting in the proposed machine is developed with rotor pole shaping, and a unique technique to provide the desired torque characteristics is described. The effect of varying pole arcs, the number of turns per pole, asymmetric pole placement, and rotor pole shaping on torque and phase inductance is evaluated to find the best machine dimensions for a required performance as well as to understand qualitatively the influence of each variable on the machine performance. Experimental results from a 2.2-hp laboratory prototype correlate the performance predictions and validate the claims for this novel TPSRM.     

高速永磁电动机设计的关键问题

高速电机具有功率密度大、尺寸小、响应快、可直接与高速机械设备连接等优点。永磁电机因其高效率、高功率因数等特点成为高速电机研究的热点。该文详细讨论了高速永磁电机设计应考虑的关键问题,包括材料选取、铁耗计算方法、转子结构和轴承选取等。     

Operating temperature considerations and performancecharacteristics for IEEE 841 motors

This paper reviews the operating temperature considerations and performance characteristics for totally enclosed fan-cooled motors as covered in the IEEE 841-2000 motor standard. NEMA MG-1-1998 motor standards are also included since they are embodied in the IEEE standard. Although the scope of product covered is for AC squirrel-cage induction motors through 500 hp, the material presented has application with many other sizes and types of motor. The paper reviews this standard as it applies to the motor operating temperature and various performance characteristics. The impact of temperature on the stator winding, rotor cage, bearings, lubrications, as well as the effects on motor efficiency and other applicable life factors, are considered     

Analysis of Rotor Core Eddy-Current Losses in Interior Permanent-Magnet Synchronous Machines

This paper presents the results of an investigation focused on the rotor core eddy-current losses of interior permanent-magnet (IPM) synchronous machines. First, analytical insight into the rotor core eddy-current losses of IPM machines is developed. Next, major design parameters that have the most significant impact on the rotor core eddy-current losses of IPM machines are identified. Finite-element analysis results are then presented to compare the predicted eddy-current losses in the machine core of IPM machines with one- and two-layer rotors coupled with concentrated- and distributed-winding stators. It is shown that the lowest total eddy-current losses in the machine core are achieved using a combination of distributed stator windings and two magnet layers per rotor pole, whereas minimizing only the rotor core eddy-current losses favors replacement of the rotor with a single-layer configuration.      

宽转子无轴承开关磁阻电机的转子极形优化

为了解决宽转子无轴承开关磁阻电机由于开关型供电方式以及双凸极铁心结构在运行过程中容易导致转矩脉动很大的问题,本文对其转子极结构进行改进,提出在转子极两侧开槽的优化设计方案。旨在通过增大开槽处的气隙磁阻,提高用于产生转矩的切向分量的气隙磁密,从而降低转矩脉动。对所开槽进行参数化处理,使用控制变量法分析各开槽参数对转矩性能的影响,以性能指标最优为目标确定开槽参数。利用场路耦合的方法将电机有限元分析模型和直接瞬时转矩控制电路模型结合起来,实现电机系统的动态运行。仿真结果表明转子极开槽后能够有效降低宽转子无轴承开关磁阻电机的转矩脉动,提升平均转矩,并且对径向悬浮力的影响很小。     

Semiconductor thermoelectric-energy conversion systems working at low temperature differences

The present thermoelectric semiconductor integrated into the commercially available thermoelectric units are not designed elaborately for low temperature difference operation. Those elements available in the room-temperature range are usually applicable for the temperature difference around 60 K with relatively poor coefficient of performance. For air-conditioning purposes, it is expected that the thermoelectric energy conversion will have a high coefficient of performance as well as economical advantage because of the low temperature difference operation. This paper describes basic and analytical considerations for low temperature-difference operation, and also the new design systems desired from viewpoints of the effective and economical use of environmental energy. An appropriate design allows a drastic economy in the material and also a drastic improvement in the coefficient of performance, and it is possible to put the material, with the presently available figure of merit, in practical use. The availability of a simple cascade connection is discussed for the operation under some increased temperature difference. The concept of the cooling or heating systems using thermoelectric units driven by a solar-cell array will also be proposed and experimental results will be illustrated.     

Distinguishing Load Torque Oscillations and Eccentricity Faults in Induction Motors Using Stator Current Wigner Distributions

This paper proposes a novel diagnosis method for detection and discrimination of two typical mechanical failures in induction motors by stator current analysis: load torque oscillations and dynamic rotor eccentricity. A theoretical analysis shows that each fault modulates the stator current in a different way: torque oscillations lead to stator current phase modulation, whereas rotor eccentricities produce stator current amplitude modulation. The use of traditional current spectrum analysis involves identical frequency signatures with the two fault types. A time–frequency analysis of the stator current with the Wigner distribution leads to different fault signatures that can be used for a more accurate diagnosis. The theoretical considerations and the proposed diagnosis techniques are validated on experimental signals.      

Non‐linear adaptive control of induction motors

Given measurements of rotor position, rotor velocity, and stator currents, we design an adaptive control scheme that is free of singularities, does not require rotor flux measurements, and provides for simultaneous asymptotic rotor position/rotor flux tracking despite the uncertainty associated with the mechanical subsystem parameters and the rotor resistance parameter. For the case when the rotor resistance parameter is known exactly, we modify the structure of the controller to achieve global asymptotic rotor position/rotor flux tracking while accommodating for parameter uncertainty associated with the mechanical subsystem parameters and the stator electrical subsystem parameters. Experimental results are presented to illustrate the performance of the control structure. Copyright © 1999 John Wiley & Sons, Ltd.     

无刷励磁机电枢及转子绝缘结构与工艺研究

对无刷励磁机的电枢及转子的绝缘结构与工艺进行了研究,通过多次试验改进,试制成功了双聚酯纤维丝和玻璃丝包双漆包F级热熔扁铜线及其他绝缘材料,从而保证了无刷励磁机安全可靠运行。本文介绍了电枢及转子绝缘结构及材料的研究情况,包括选择方法,电性能及冷热态机械性能。     

Optimization of Shield Thickness of Finite-Length Solid Rotors for Eddy-Current Loss Minimization

A high-conductivity shield is often used for coating the rotor of solid-rotor synchronous machines for reducing the surface eddy-current losses due to armature-reaction space/time harmonics and/or tooth ripple. Since the design process for determining the optimal shield thickness can be complicated and time consuming, a simple analytical model based on Maxwell's equations was developed and presented in a previous paper to simplify the process. It has been shown that such an analytical tool can be used as a quick and effective “screening tool” for determining the range of the optimal shield thickness for minimizing rotor surface losses; however, the influence of finite rotor axial length including the end-face losses was not taken into account. In this paper, an additional step is introduced in the shield design process where a special finite-element (FE) method that accounts for the impact of finite rotor axial length is employed for refining the design obtained from the analytical solution. Comparisons are made for a number of shield thicknesses and rotor lengths for significant space and time harmonic combinations to verify the validity of the proposed two-step design process (analytical and FE) and to evaluate the impact of the finite length of solid rotors.      

Instrumentation, testing, and analysis of electric machine rotor steady-state heating

It is not a simple task to measure temperatures on the rotors or rotor components of large induction and synchronous machines during steady-state operation. The single greatest obstacle to obtaining these data is related to getting the data from the rotating element. Other problems are associated with instrumentation noise, sensor type, and attachment. This paper describes a number of techniques that have been used by the authors and their associates over the last 30 years. Test and calculated temperatures are presented for one machine. Also, test data from a number of machines are presented that show, for this particular population of enclosures and ventilation schemes, the steady-state temperatures at the design load can range from the value of the stator rise to greater than 70/spl deg/C higher.