开槽实心转子电机转子端部系数的计算与比较

开槽实心转子异步电机转子的三维非线性涡流场计算量大,常采用二维有限元结合光滑实心转子端部系数的方法简化计算。但在转差率增大时,采用光滑转子端部系数仿真计算的误差明显增大。根据开槽实心转子涡流分布随转差率变化的规律,提出适用于全转差率范围的开槽转子端部系数。依据该端部系数修正转子电阻率,并采用非线性有限元计算开槽实心转子电机电磁场,可考虑转子端部效应以及定、转子铁心磁路饱和的影响。在不同工况下,对两台不同转子槽数的开槽实心转子样机分别采用不同转子端部系数进行仿真计算,并与实验结果比较。该文提出的开槽转子端部系数的仿真与实验结果较吻合,且在转差率较大时,开槽转子端部系数随转子槽数增多而增大。可为准确计算开槽实心转子电机参数及其设计优化提供依据。     

考虑阻尼绕组约束能量变换器空载电动势波形的分析

电机的阻尼绕组端部联结方式的不同,使得阻尼条中感应涡流的约束不同,引起阻尼绕组电流的分布不同,从而对气隙磁场和空载电动势产生影响.本文提出了场路耦合时步有限元法来计算凸极同步电机空载电动势波形,针对能量变换器样机,进行了考虑不同阻尼绕组约束条件下的空载电动势波形的计算,并对计算结果和实验值进行了比较.结果表明,阻尼绕组约束不同,能量变换器空载电动势谐波含量不同,电动势波形的正弦畸变率也发生一定的变化,精确计算时需要考虑这种变化.     

Investigation of a new extinguishing principle for a gas circuit breaker

A self-extinguishing principle of a gas circuit breaker (GCB) without puffer action (autopuffer GCB) using an external magnetic field was investigated to improve the interrupting capability in the small current region (several kA). Properties of the rotating speed of an arc, the arc voltage, and the gas pressure rise in an expansion space under the external magnetic field were studied experimentally. The relation between the interrupting capability and the radial magnetic flux density in the autopuffer GCB with a permanent magnet (magnet-assisted autopuffer GCB) was obtained experimentally and also analyzed numerically. The results are summarized as follows.

• 1 The arc column is driven in the azimuthal direction by the radial component of the external magnetic field.
• 2 The rotating speed of the arc driven by the radial magnetic field of a permanent magnet remains constant in the arc current range below several kA, and it decreases with an increasing current in the current above several kA.
• 3 Since the arc rotation raises the arc voltage and gas pressure in the expansion space, the gas flow from the expansion space to the arc increases in the vicinity of current zero. The interrupting capability is then improved in the small current region.
• 4 It is confirmed that the magnet-assisted auto-puffer GCB has a good interrupting capability not only for the large current region but also for the small current region.

     

双凸极无刷直流发电机的非线性数学模型

用变网络等效磁路法建立电励磁双凸极发电机等效磁路模型。在考虑磁路饱和、电枢磁场和励磁磁场相互作用的基础上 ,给出了描述该发电机非线性电感的函数 ,函数值与转子位置、各相电枢电流和励磁电流有关。有限元法验证了该函数的计算结果具有很高精度。在基于电感数值解基础上建立了该无刷直流发电机负载时一个工作模态非线性数学模型 ,给出了描述该数学模型的微分方程。理论计算结果和样机实验结果对比验证了该模型的正确性 ,为研究双凸极发电机的工作性能提供理论依据     

A Three‐Position Swing Electromagnetic Actuator with an Integrated Eddy Current Brake for Suppression of the Operating Time and Improvement of the Stopping Accuracy

A closed‐loop control system is commonly used in electromagnetic actuators to ensure operating performance. However, this system frequently leads to high costs. We developed a swing electromagnetic actuator with an integrated eddy current brake to reduce the operating time and improve the stopping accuracy. The developed actuator is a three‐position cylindrical actuator moving within a ±120º angle without closed‐loop control. The rotor is composed of a bulk and thin metal laminations and the stator has three sets of pairs of coils. The rotor is stopped at an intermediate position by magnetic force generated by the coils. This paper describes the electromagnetic design and its evaluation by using an FEM simulation to predict its operating characteristics and measure its performance on a test bench. The superiority of our actuator design is verified by comparing these measurements. The operating time is reduced to one‐sixth of that of a laminated rotor and the over travel is compressed to zero. In addition, this actuator has the advantage that it is electrically robust against variations in the power supply.     

A new method of characteristic analysis for three‐phase induction motors

Generally speaking, the characteristics of induction motors (IM) are analyzed by means of the equivalent circuit with d–q transformation. Although this method is simple, the magnetic flux distributions in the stator and rotor are defined as sinusoidal waves. Therefore, the equivalent circuits become relatively complex for the high‐frequency components and transient states. For detailed analysis, the finite element method (FEM) is used. The FEM can take account of the influence of skewed rotor bars and slots, and of the skin coefficient. However, the calculation time is very long for high‐frequency components and transient analysis. We therefore propose a new method of characteristic analysis for IM. The proposed method analyzes the magnetic flux simply based on the construction of the IM. It can analyze transient and steady states and high‐frequency components regardless of the type of source. The influence of skewed rotor bars and slots can also be treated simply. This paper describes the method of analysis, presents the results of the proposed method and compares them with experimental results, and describes the d–q transition. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 64–75, 2001     

交交变频同步电机阻尼绕组损耗的分析与计算

本阐述了凸极同步电机中谐波增量磁场的作用及特点。给出了可计及包括端部影响的任意复杂转子回路的场路耦合计算格式。针对交交变颏同步电机阻尼绕组的计算问题，提出一种等效多端口网络的概念，并据此对两种阻尼绕组结构的损耗进行了分析比较。     

Reduction of higher harmonic sequences in terminal voltage of an AC exciting synchronous generator using magnetically anisotropic slot wedges

This paper describes relationships between characteristics of a magnetically anisotropic slot wedge and voltage higher harmonics in an ac exciting synchronous generator terminal due to permeance ripple caused by an open-slot-type rotor. From the relationships obtained, practical guidelines were formulated for machine designs applying the magnetically anisotropic slot wedge. The results are as follows.

• 1 (1) Equivalent permeability of the magnetically anisotropic slot wedge became isotropic wedge permeability for air-gap flux ripple.
• 2 (2) Two ways were identified to reduce voltage-higher harmonics by using the slot wedges.
• 3 (3) The level of leakage flux passing through the anisotropic slot wedge was determined only by its permeability in the width direction.
• 4 (4) Effectiveness of the magnetic anisotropic slot wedges inserted into the stator slots was verified from experimental results using a model machine of the open- slot-type rotor.

     

大型汽轮发电机定子端部磁场与参数的准确计算与分析

建立了用三维正弦行波磁场有限元法计算汽轮发电机定子端部磁场的数学模型,提出了一种能准确反映定子绕组端部渐开线分布的电流密度的离散表达式,给出了用能量法计算定子端部漏抗的计算公式,并在此基础上以一台600MW汽轮发电机为例分析端部结构件中涡流,定、转子铁心长度等因素对定子端部漏抗的影响,得出了一些有价值的结论.     

高压自耦变压器肺叶磁屏蔽特性的数值计算与分析

针对一种新型的器身磁屏蔽——肺叶磁屏蔽自身以及其在变压器中的设计问题,以一台容量为334MV?A、带有肺叶磁屏蔽的单相自耦变压器为研究对象,首先应用三维频域非线性有限元法分析了肺叶磁屏蔽对变压器结构件、绕组区域漏磁场以及杂散损耗的影响;然后,以漏磁场分析以及杂散损耗计算为手段,以变压器油箱、夹件、拉板、油箱屏蔽以及肺叶磁屏蔽的磁感应强度(或损耗密度)作为观测目标,研究肺叶磁屏蔽安装位置以及尺寸对变压器漏磁场的影响,并通过负载损耗试验将有限元计算所得结果与实验值进行对比,验证分析的有效性;最后,针对肺叶磁屏蔽自身可能出现的局部过热问题,设计三种不同的肺叶磁屏蔽油路结构,基于有限体积法对比分析不同油路结构下肺叶磁屏蔽的油流、温升特性。对肺叶磁屏蔽特性的系统分析可为其设计以及其在变压器中的设计提供指导,具有重要工程意义。     

大型同步发电机故障灭磁仿真

本文对大型同步发电机故障状态下的线性和非线性电阻灭磁进行了仿真计算。其仿真模型考虑了转子阻尼绕组的感应作用和发电机空载特性的非线性,并利用积分算子1/s实现了灭磁微分方程的求解和磁能的计算,以期对电阻的灭磁性能进行更直观的分析。给出了某一300WM汽轮发电机故障灭磁的Matlab仿真结果,其较好地再现了发电机的灭磁过程,获得了灭磁电阻性能的对比结果。     

基于场路耦合法的大电流互感器屏蔽绕组分析

大电流互感器通常工作于强杂散磁场环境,必须采取有效措施来保护其不受外界电磁干扰。屏蔽绕组作为一种新颖的屏蔽方式,在大电流互感器中得到了广泛的应用。该文以25000/5A电流互感器为研究对象,利用基于场路耦合的方法来建立大型发电机组用电流互感器的三维有限元仿真模型和统一的场路耦合数学模型,在此基础上计算其屏蔽绕组中的电流；通过比较等效磁势法和降流回路法仿真计算结果与试验测量数据,证明了3D有限元仿真模型的正确性；最后,依据上述模型分析屏蔽绕组抗具有电磁干扰的良好效果。     

考虑磁路饱和的永磁式同步电机计算

介绍一种考虑到磁路饱和的永磁同步电机转矩和电抗的计算方法。该方法利用有限元法对二维磁场进行数值解析，并给出包含正交磁化现象影响的d、q轴方程式。通过改变转子的位置计算水磁同步电动机的转矩和电抗，给出了转矩和电抗随转子位置变化规律的曲线。实验结果验证了其计算方法的正确性。     

带平衡绕组大电流互感器磁场的三维有限元仿真研究

在大电流互感器(大TA)设计中,由于一次额定电流很大,无法进行现场三相环境条件下的物理试验,故常以等效试验方法来优化平衡绕组的匝数及其各段间的连接方式。但目前的等效试验法不准确,且成本高、周期长,为解决此问题,笔者对以三维有限元法分析现场三相环境条件下大TA磁场的有效性进行了研究。具体采用基于矢量磁位和标量电位的A-Φ法计算了大TA的磁场,采用棱边单元而不是节点单元,避免了用基于矢量磁位的节点单元法计算媒质磁导率不一致的模型时带来的错误,并以间接场路耦合法计及了外电路的影响。计算了在邻相大电流母线磁场干扰下,大TA的四段平衡绕组做反极性串接时,平衡电流值以及铁心中的最大磁感应强度值,并确定了它们随平衡绕组位置改变的变化规律。数值仿真与磁路法估算结果相吻合,证明了以三维有限元法对现场环境条件下大电流互感器的磁场进行仿真是可行的。     

阻尼绕组对凸极同步发电机空载电势波形的影响

采用二维瞬态涡流场有限元法，对装有阻尼绕组的凸极同步发电机的空载电势波形进行了计算，分析了阻尼绕组节距对空载电势波形的影响。结果表明，阻尼绕组可以削弱定子齿谐波分量，而对与阻尼绕组节距有关的谐波分量则有加强作用。     

涡流效应对磁轴承参数设计的影响及优化设计

实心结构的转子旋转时,产生的附加磁场(涡流场)会使转子的运动状态显著不同于静止悬浮,可见依赖于静态工作点的磁轴承参数设计精确性不高,因此需要考虑涡流效应对参数设计的影响。利用有限元仿真软件估算了磁轴承设计中的关键参数受涡流效应影响的变化情况,并通过对比气隙磁通密度的实测值与有限元仿真值,验证了所建立有限元模型的正确性。在此基础上还提出了一种优化方案,并通过优化实例的仿真结果验证了该设计方法的合理性和设计结果的正确性。因此,分析涡流效应对交流主动磁轴承参数设计的影响并提出的简单精确的优化方案对采用实心转子的交流主动磁轴承参数设计具有重要的参考价值。     

阻尼绕组对磁力齿轮动态特性的改善

与传统机械齿轮相比,磁场调制式磁力齿轮输入与输出轴之间非机械连接,具有无磨损、无润滑、大速比与过载保护等特点,使得其在变速机械方面具有特殊应用价值。然而,由于两转子间存在非刚性磁耦合特性,导致在启动以及负载和速度发生变化时,出现暂态振荡现象。为了提高整个传动系统的动态稳定性,提出一种在高速转子侧增加阻尼绕组的结构设计,在电磁场有限元分析基础上,建立了动态仿真模型,对磁力齿轮增加阻尼绕组前后动态性能进行对比研究,结果证明阻尼绕组结构能有效减小传动系统的振荡幅值,缩短调节时间。     

EFFECTIVENESS AND DISSIPATION IN CRYOGENIC SHIELDS FOR SUPERCONDUCTING FIELD WINDINGS*

ABSTRACT

This paper is a contribution to the analysis of rotor shielding systems, particularly with respect to shielding and losses in cryogenic shielding systems. The method of surface wave impedance is used in a modified way, and extended to accomodate transposed shields. Solid shields are found to have good shielding properties but relatively large losses, while transposed shields have lower losses but poor shielding. Combination screens may be expected to present satisfactory characteristics, but only with the provision of adequate radial spacing within the rotor.     

现场校准用磁调制式直流电流比较仪磁屏蔽结构仿真研究与设计

直流电流互感器现场校准存在较强的电磁干扰和其他不确定的环境因素,因此现场校准用直流电流标准器不仅需要具有较高的测量准确度,还要具备较强的抗电磁干扰的能力。首先利用ANSYS软件对用于现场校准标准器的磁调制式直流电流比较仪磁屏蔽结构进行了建模仿真,分析了屏蔽层厚度、屏蔽材料的磁导率以及气隙对屏蔽效果的影响。根据仿真结果,完成了直流电流比较仪磁屏蔽结构的设计。其次,通过仿真分别分析了无磁屏蔽结构和有屏蔽结构条件下,母线偏心和邻近外导体所产生的干扰磁场对直流电流比较仪测量准确度的影响。最后,完成了额定参数为5 000 A:5 A的直流电流比较仪样机的研制,并通过测试验证了仿真设计的有效性,所研制的直流电流比较仪整体准确度达到0.005级的应用要求。     

Performance evaluation of squirrel‐cage damper structure for superconducting generators

Superconducting generators have many advantages such as increasing generation efficiency and improving power system stability. In Japan, 70‐MW‐class superconducting generators have been developed through the national project “Electric Power Application of Superconducting Technologies (1988–1999).” In this paper, performance evaluation of the rotor damper structure for the 70‐MW‐class model generator is discussed. Double‐layered damper structure, which consists of a squirrel‐cage warm damper and a single‐layered cold damper, was set as the target. As the first step, basic electromagnetic and thermal performances were obtained. Consequently, it was proven that the damper structure had the performances to satisfy the requirements of the superconducting generators. Performances obtained from the experimental model, design of the 70‐MW model rotor, and evaluation by the verification tests are described in this paper. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(1): 19–33, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20025