Eccentricity Fault Diagnosis and Torque Ripple Analysis of a Four-pole Synchronous Reluctance Machine in Healthy and Faulty Conditions

Abstract—In this research, torque ripple is analyzed, considering both slot opening and distributed winding effects for a 4-pole 60-slot synchronous reluctance machine under healthy and eccentricity fault conditions. Mathematical-based models and numerical methods are used to study the behavior of the machine, especially when it is supplied with a voltage source. For this purpose, the parameters of the machine are computed in both healthy and eccentricity fault conditions using the winding function theory. This article proposes a method that deals with both dynamic and static eccentricity fault diagnosis using a vibration signature; consequently, the results demonstrate that the eccentricity fault has no significant effect on the machine's current signature. Moreover, unbalanced magnetic pull is computed considering eccentricity fault, and then mechanical instability is proven to occur under such circumstances. It should be noted that previous works were generally based on the finite-element method, and current sources were used as suppliers; in this article, a mathematical-based model is utilized and voltage sources are considered as suppliers, which are two main advantages of this article over previous ones. Verification carried out by simulation via the finite-element method supports the effectiveness of the model and control approach.     

Simulation and detection of dynamic air-gap eccentricity insalient-pole synchronous machines

This paper presents the effect of dynamic air-gap eccentricity on the performance of a salient-pole synchronous machine. The modified winding function approach (MWFA) accounting for all space harmonics has been used for the calculations of machine winding inductances. In addition, the winding inductances have been calculated by the finite-element method to support those calculated by the MWFA. Relationships between stator-current-induced harmonics and dynamic air-gap eccentricity were investigated. The coupled magnetic circuits approach has been used for modeling the synchronous machine performance under the dynamic air-gap eccentricity. Finally, experimental results to substantiate the theoretical findings are presented     

Five‐phase modular stator surface‐mounted permanent magnet machine with reduced space sub‐harmonics

Multiphase modular stator surface‐mounted permanent magnet machines (MSPMs) feature short end connection, unity winding factor, and low cost. However, they also exhibit rich space harmonics. A five‐phase MSPM with reduced space sub‐harmonics is proposed in this paper. The phase‐shifting method and magnetic flux barriers are adopted to reduce the slot harmonic and lowest order harmonic, respectively. A modified MSPM used for phase shifting is specially proposed. Further, the phase‐shifted MSPMs without and with magnetic flux barriers are both studied to show the separate effectiveness of the phase‐shifting method and magnetic flux barriers. The phase‐shifting angle is determined based on winding function method and the optimal angle is fixed considering the minimal tooth width. A double‐layer MSPM with 20 slots and 22 poles is exemplified, and two single‐layer 40‐slot 22‐pole MSPMs, which are respectively equipped without and with magnetic flux barriers, are proposed. Finite element analysis is performed, and the comparison results show that the space sub‐harmonics, permanent magnet eddy current loss, and the lowest mode of vibration are largely reduced in the phase‐shifted MSPM with magnetic flux barriers. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Modelling and study of PM machines with inter-turn fault dynamic model-FEM model

In this paper, a simple dynamic model for a PMSM with inter-turn winding fault is derived. Finite element method is used for parameter determination of machine with fault. This dynamic fault model is used to study the PM machine behaviour under various inter-turn fault conditions. A 2D time stepping finite element method (FEM) model is carried out to validate the dynamic fault model. The dynamic model results exhibit the same trend as predicted by FEM analysis for different fault insulation resistances. An experimental test is also conducted to verify the fault model. This model is used to study the machine behaviour under various fault conditions and severity. The proposed model seems to be well adapted for PM motors health monitoring and inter-turn fault diagnosis.     

A power‐performance tunable logic with adjustable threshold pseudo‐dynamic building blocks and CMOS compatibility

The continued downscaling of CMOS technology has resulted in very high performance devices, but power dissipation is a limiting factor on this way. Power and performance of a device are dependent on process, temperature, and workload variation that makes it impossible to find a single power optimal design. As a result, adaptive power and performance adjustment techniques emerged as attractive methods to improve the effective power efficiency of a device in modern design approaches. Focusing on this issue, in this paper, a novel logic family is proposed that enables tuning the transistor's effective threshold voltage after fabrication for higher speed or lower power. This method along with dynamic voltage scaling allows simultaneous optimization of static and dynamic power based on the workload requirement. The externally static topology of the proposed logic makes it possible to replace static circuits without requiring significant changes in the system. Experimental results obtained using 90‐nm CMOS standard technology show that the proposed logic improves the average power‐delay product by about 40% for the attempted benchmarks.     

Influence of magnet shaping on cogging torque of surface‐mounted PM machines

In the presented work, influence of magnet shaping on cogging torque of surface‐mounted Permanent Magnet (PM) machines is investigated. The considered PM shape for the magnet shaping is the loaf‐shape PM with off‐set arcs. For the first time, based on the solution of the Poissons's equation, an analytical model is provided to predict the magnetic flux density of the slotted‐armature and surface‐mounted PM machines with the loaf‐shape PM. The influence of the slotted armature on the magnetic flux density is taken into account by considering the slot virtual surface currents. The geometry of the loaf‐shape PM is formulated and optimized to reach a design with a low value of the cogging torque. The machine cogging torque is computed by the Maxwell stress tensor. The obtained analytical model is used as the computational tool to find the dependence of the machine cogging torque on the PM geometry. Finally, the validity of the obtained results is verified by finite element analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

Analog circuits fault diagnosis using multi‐valued Fisher's fuzzy decision tree (MFFDT)

Fault diagnosis of analog circuits is more challenging compared with digital circuits as a result of the parametric deviation and the difficulty in signal discretization. There still lacks effective approaches to realize reliable fault detection and isolation for a comprehensive diagnosis. A new fault diagnosis technique called multi‐valued Fisher's fuzzy decision tree (MFFDT) is proposed in this paper to solve the problem. This technique uses the decision tree as the diagnosis model and incorporates the Fisher's linear discriminant principles. The fuzzification mechanism is devised to discretize the input monitoring data. The proposed MFFDT method is composed of two aspects: decision tree training and real fault diagnosis processes. The former uses the benchmark data to train a decision tree, while the latter sends the monitoring data into the decision tree to generate diagnosis results. The proposed method is validated using simulated data and the real‐time data for an active filter circuit and an audio amplifying circuit. The comparative analysis is also presented to evaluate diagnosis performances. Copyright © 2015 John Wiley & Sons, Ltd.     

Chaotic system identification using Wiener‐LSSVM model

In this paper, a new method is proposed for identifying chaotic system based on a Wiener‐least squares support vector machine (Wiener‐LSSVM) model. The model consists of a linear dynamic subsystem followed by a static nonlinear function, which is represented by LSSVM in this paper. The parameters of the linear dynamic part and those of LSSVM are estimated simultaneously by solving a set of linear equations using the least squares (LS) method. The proposed method incorporates partial structure information into the identification process and does not assume that the parameters of linear dynamic part are known. On the other hand, the LS algorithm is more efficient than gradient‐descendent‐based algorithms for estimating the parameters of Wiener‐LSSVM. Three identification examples are given to validate the effectiveness of the proposed method. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A method for dynamic simulation of air-gap eccentricity ininduction machines

In this paper, a method is proposed which enables the simulation of the air-gap eccentricity in induction machines. The method is based on the coupled magnetic circuit approach. The model is derived by means of winding functions, and no symmetry in windings layout is assumed. The parameters of the model are calculated directly from the geometry and winding layout of the machine. The effect of eccentricity is included in calculation of machine inductances. It is shown that by proper modeling of the induction motor it is possible to determine the effect of eccentricity on the machine startup, whether the machine is running off a sinusoidal supply or a converter. Theoretical foundations of the technique, as well as the detailed differential equations describing the machine performance under rotor eccentricity are presented     

Slot Numbering and Distributed Winding Effects Analysis on the Torque/Current Spectrum of Three-phase Wound-rotor Induction Machine Using Discrete Modeling Method

Smooth torque production by induction machines is an improbable phenomena that is taken into account only in classic and ideal studying methods. In this research, slot numbering and also non-sinusoidal winding function effects are studied for a three-phase wound-rotor induction machine, which is addressed for the first time, and a new formula is introduced for calculating the spectral components of machine torque and current. To reach this aim, mathematical modeling of the air-gap function is proposed, and a discrete time modeling of the machine is introduced to study the effects of space harmonics on the torque/current spectral. To study the mentioned phenomena, in the first part, the winding functions are considered as ideally sinusoidal and the behavior of simulated machines is investigated based on the winding function approach and numerical method analysis. Two certain formulas are introduced for the spectral components of torque ripple and stator currents according to the slot numbers, rotor speed, and number of machine poles. In the second part, slot opening effects are neglected and non-sinusoidal windings are considered for obtaining the same results. Finally, considering both effects, model validation is confirmed by a finite-element-based method, and the introduced method is proven.     

Surface induction motor for two‐dimensional drive

In this paper, the authors propose an induction type surface or planar motor for smooth two‐dimensional drive including rotating operation. The secondary member is composed of the flat conducting plate without directional qualities and the back‐iron plate as secondary yoke. The primary member is composed of the torodial core and the armature winding which can supply the current in every coil embedded in a slot. For the rotating drive, all the coils are used and the same rotating magnetic field as an ordinary rotating motor is generated. For the linear drive, a partial rotating field is generated in the direction of movement in each region separated into two groups every half of toroidal core. For the armature winding, two types of methods are used which are a ring‐winding supplied current at each slot and a double‐layer‐winding supplied current to each coil. The two‐dimensional electromagnetic analysis in Cartesian coordinate system is shown for the analysis, in which an effect of circular shape is considered as an edge effect. The thrust and normal force characteristics at standstill were confirmed practically by using test machine. It was cleared that the surface motor had high transformation rate of about 79% for thrust in spite of the circular shape. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 107–115, 2000     

电网对称故障下无刷双馈电机低压穿越分析

通过控制电机转子磁场定向得到同步坐标系下的仿射非线性状态空间模型,针对无刷双馈发电机组机侧控制器应用反馈线性化解耦控制方法。在电网电压三相对称跌落下,分析控制电机定子电流和控制电机定子反电动势的暂态响应。推导得出BDFM稳定运行时,控制电机转子磁链与功率电机定子电压满足线性比例关系,在低压穿越模式下来改善系统控制性能和稳定性,提高机组低压穿越能力。仿真结果证明了理论分析的正确性和有效性。     

异步电动机断条与静偏心复合故障的电流特征

为了研究笼型异步电动机断条和静态偏心复合故障特征,采用多回路数学模型和改进的绕组函数法对复合故障下的定子电流特征进行了机理分析和仿真研究。首先建立笼型异步电动机的多回路数学模型,通过改进的绕组函数法计算了笼型异步电动机复合故障下的电感参数,推导了复合故障在定子电流中产生的特定谐波频率计算公式,然后建立了笼型异步电动机正常状态和复合故障时的有限元仿真模型,通过仿真对理论结果进行了验证。结果表明,复合故障发生时定子电流中除存在单一断条和静态偏心故障的特征频率外,还会产生一系列附加谐波分量,理论分析与仿真结果相符。     

Radial Force Analytic Modeling for a Novel Bearingless Switched Reluctance Motor When Considering Rotor Eccentricity

Abstract—Analytic modeling of radial forces is proposed for the novel bearingless switched reluctance motor, where the rotor eccentricity is taken into account. The novel bearingless switched reluctance motor's model is never disclosed, even though there are many advantages, such as fewer suspension windings and simpler control circuit and algorithm, when compared to the conventional bearingless switched reluctance motor. The analytic model of radial forces is very important to achieve this new bearingless switched reluctance motor's suspension control. The rotor eccentricity is a key cause to affect the radial forces. This article calculates the air-gap permeances through considering rotor eccentricity. The self-inductance and mutual-inductance expressions of the motor torque windings and the suspension windings are derived by using the magnetic equivalent circuit method. The derived radial force model discloses the effects of winding currents, rotor position angle, and rotor eccentricity displacement. The finite-element analysis based results verify the built model.     

基于FFT-LSTM的变速抽蓄机组转子绕组短路故障和偏心故障诊断方法

变速抽水蓄能机组是适应系统功率波动的重要调节手段。转子绕组短路故障和转子偏心故障是其常见的故障类型,两种故障均会在定子侧感应生成特征频带相近的谐波环流,导致两种故障难以被区分。提出了一种基于快速傅里叶变换-长短期记忆(fast Fourier transform-long short-term memory, FFT-LSTM)网络的故障诊断方法,以细化分辨故障特征相近的转子绕组短路故障和转子偏心故障。所提方法以定子分支环流的谐波分量为特征量进行故障诊断,分别推导了两种故障发生时定子侧环流谐波特征,并总结二者间的相似性和差异性。鉴于该差异较为微弱,引入长短期记忆(longshort-termmemory, LSTM)神经网络算法对其进行辨识。利用内部故障仿真模型对可能发生的转子绕组短路故障和偏心故障进行批量仿真,以得到用于LSTM网络训练和测试的数据集。仿真结果表明FFT-LSTM能够准确诊断不同转速下变速抽蓄机组的转子绕组短路故障和转子偏心故障。     

A new false‐root identification method based on two‐terminal fault location algorithm for double‐circuit transmission lines

A fault location algorithm without synchronization for double‐circuit transmission lines does not require sampling synchronization, reduces the cost, and has a higher engineering value, but the algorithm still needs to be improved in the false‐root identification. This paper conducts further studies on this issue. First, the false‐root problem of the fault location algorithm without synchronization is analyzed, and then a new false‐root identification method is proposed, which is based on the difference of the existence of the false root in the calculation of the voltage amplitude along the line with different electrical moduli. It can solve the problem of the traditional method, which cannot distinguish between voltage amplitudes when they are close. Second, considering the shortcoming of the existing phase‐mode transformation matrix, a new phase‐mode transformation matrix applied to double‐circuit lines is deduced, which is based on the six‐sequence component method; it can be combined with the new false‐root identification method, thereby realizing false‐root identification under various types of faults. Finally, fault location is realized by using the moduli in the mold domain. The principle does not need to synchronize data in two terminals and is not affected by the fault types, fault resistances, and other factors. As is shown in a large number of Alternative Transients Program version of Electro‐Magnetic Transients Program (ATP‐EMTP) simulation results, the fault location has a higher accuracy © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

以槽电势为分析单元的大型发电机定子接地故障定位方法

已有的大型发电机定子绕组单相接地故障定位方法一般以线圈匝电势为分析单元,对于短距绕组的机组存在理论误差。为此,提出一种以槽电势为分析单元的大型发电机定子单相接地故障定位方法。首先,基于绕组连接顺序,以槽电势为单元建立定子绕组电势分布的解析表达式。然后,针对发电机是否配备注入式定子接地保护采取不同的故障定位方案。若配备注入式定子接地保护,则基于注入式设备的过渡电阻测量值构造故障评价指标。若未配备注入式定子接地保护,则引入3次谐波测量值构造不含过渡电阻的故障评价指标。最后,在故障相人为设置多个虚拟参考点,结合绕组电势分布计算各虚拟参考点的故障评价指标,将计算值最小的虚拟参考点视为故障位置,进而确定故障所在槽编号。利用在PSCAD中搭建的准分布参数仿真模型验证了所提方法的有效性。     

基于Hilbert边际谱和IPSO-SVDD的滚动轴承故障诊断

滚动轴承是旋转机械状态监控及故障诊断的重要研究内容。为了更加高效的对轴承故障位置及故障程度进行诊断,提出了一种基于Hilbert边际谱和改进粒子群算法(IPSO)优化支持向量数据描述(SVDD)相结合的滚动轴承故障诊断方法。该方法首先求取轴承振动信号的本征模态函数,在此基础上得到信号的边际谱以及信号的AR模型参数,积分求取边际谱的能量特征函数和AR模型参数相结合构成系统特征向量。然后针对传统网格搜索法或凭经验确定SVDD核心参数的缺点,提出利用基于动态因子的粒子群算法对SVDD的核心参数惩罚常数C及核函数宽度σ进行优化,利用优化后的SVDD模型对滚动轴承各状态信号进行智能诊断。人工数据集及真实数据集实验结果表明,该方法可以有效识别各故障状态信号,并且优化后模型的诊断效率及诊断精度高于传统网格搜索法确定的模型。     

Basic Design Method for SPMSM Based on Air‐Gap Magnetic Flux Density Distribution Focusing on Image Magnetic Pole

This paper presents a basic design method for the surface‐mounted permanent magnet synchronous motor (SPMSM) for both distributed and concentrated windings. The design is based on the air‐gap magnetic flux density distribution focusing on the image magnetic pole. The calculus equation of the air‐gap magnetic flux density distribution is analytically derived by supposing the magnetic pole is located on the magnet surface and image planes. In this study, a three‐phase and double‐layer stator winding SPMSM that has a linear demagnetizing characteristic magnet, such as a ferrite or rare‐earth magnet is considered. From the required specifications and design conditions, the design target values of the parameters that appear in the voltages equations of the d–q axis coordinate system are calculated. Then, the relational equations for the torque constant, d‐axis inductance, copper loss, and the maximum current density are presented as a function of three design parameters under i_d = 0 control. They are the stator stack length, the number of coil turns in series in a phase, and the slot bottom length. Hence, this approach reduces the SPMSM basic design to the problem with these design parameters has to be solved. The proposed method makes it possible to address the concentrated winding as a special case of the distributed winding. The FEA results confirm the validity of the proposed basic design method for both distributed and concentrated windings.