Analysis of a Low-Cost Air-Gap Winding for Permanent Magnet Synchronous Motors

This paper presents an analysis of a concentrated air-gap winding concept intended for low-cost, high-speed applications where the reduced winding construction cost can motivate its use. Expressions for magnet flux linkage, torque, winding inductance, and unbalanced magnetic pull are derived and compared, with good agreement, to measurements and results obtained from finite-element simulations.      

Interturn Fault Diagnosis in Induction Motors Using the Pendulous Oscillation Phenomenon

A robust interturn fault diagnostic approach based on the concept of magnetic field pendulous oscillation, which occurs in induction motors under faulty conditions, is introduced in this paper. This approach enables one to distinguish and classify an unbalanced voltage power supply and machine manufacturing/construction imperfections from an interturn fault. The experimental results for the two case studies of a set of 5-hp and 2-hp induction motors verify the validity of the proposed approach. Moreover, it can be concluded from the experimental results that if the circulating current level in the shorted loop increases beyond the phase current level, an interturn fault can be easily detected using the proposed approach even in the presence of the existence of motor manufacturing imperfection effects     

Real-Time Implementation of Wavelet Packet Transform-Based Diagnosis and Protection of Three-Phase Induction Motors

This paper presents a real-time implementation of an online protection technique for induction motor fault detection and diagnosis. The protection system utilizes a wavelet packet transform (WPT)-based algorithm for detecting and diagnosing various disturbances occurring in three-phase induction motors. The criterion for the detection is the comparison of the coefficients of the WPT of line currents using a mother wavelet at the second level of resolution with a threshold determined experimentally during the healthy condition of the motor. The algorithm is implemented in real-time using the Texas Instrument TMS320C31 32-b floating-point digital signal processor with the help of object-oriented programming. The proposed technique is tested on two three-phase induction motors. The online test results give a response signal at the instant or within one cycle of disturbance in all cases of investigated faults. In addition, the algorithm is also tested during no load and full load operating conditions of the motor.     

Multiple Reference Frames Theory: A New Method for the Diagnosis of Stator Faults in Three-Phase Induction Motors

This paper proposes the use of the multiple reference frames theory for the diagnosis of stator faults in three-phase induction motors. The development of a simplified mathematical motor model allowed the establishment of the equivalent circuits of the motor, in$d!!-!!q!!-!!0$axes, in the presence of stator interturn short circuits. The use of the stationary reference frame, clockwise and counterclockwise synchronous reference frames, allows the extraction and manipulation of the information contained in the motor supply currents in a way that the effects introduced by the fault are easily isolated and measured. A severity factor is defined and the simulation and experimental results presented demonstrate its independence in relation to the working conditions of the motor, such as the load level and unbalances in the voltage supply system. Although the technique is here introduced for the diagnosis of stator faults, it is possible to extend its use for the diagnosis of other asymmetries such as broken rotor bars and air-gap eccentricity.     

Sensorless Slowdown Detection Method for Single-Phase Induction Motors

The single-phase capacitor-run induction motor is generally used for fractional power in applications where the price is an important criterion. In order to save costs, one tries to estimate the speed on the basis of voltage and current measurements, and thus avoid a speed sensor. The techniques used are very varied. In the last few years, they have included numerous patents and often the use of microcontrollers. First of all, this paper shows the analytical characteristics of the induction motor with its capacitor. It explains the different possible methods to assess the speed. Then, the paper suggests a realization using one of these methods on a motor of a rolling shutter. The setup tested implements a microcontroller that cuts off the supply as soon as an abnormal reduction in speed is observed on a basis of a voltage measurement. This paper details the implementation on the industrial application.      

Models for Balanced Voltage Operation of Linear Induction Motors

The mathematical analysis for many studies on linear induction motors is based upon an extension of the iron in the direction of motion. The models from two such analyses are compared. For a single layer induction motor fed by a three phase balanced voltage, one of the models is shown to yield better results than the other.     

逆向推理法在汽轮机进水事件故障诊断中的应用

以某公司汽轮发电机组的一次跳机事件为内容,介绍了在一起不常见的汽轮机进水事件的分析处理中,应用逆向推理法进行设备故障诊断的思考方法,以及故障处理情况。     

Improvement in Modeling and Testing of Induction Motors

The paper presents a method for identifying the parameters of a new model of induction motor. This model has two rotor loops in order to take into account the deep-bar effect and a non-linear leakage reactance which represents magnetic saturation effect. These phenomena cannot be neglected when induction motor dynamic characteristics have to be evaluated. The test method is simple and non-iterative. Only two locked-rotor tests at rated current and different frequency are required to derive the parameters of the two rotor loops. A further locked-rotor test at a suitable current value is necessary to determine the non-linear leakage reactance of the model.     

Artificial-Neural-Network-Based Sensorless Nonlinear Control of Induction Motors

In this paper, two architectures of artificial neural networks (ANNs) are developed and used to correct the performance of sensorless nonlinear control of induction motor systems. Feedforward multilayer perception, an Elman recurrent ANN, and a two-layer feedforward ANN is used in the control process. The method is based on the use of ANN to get an appropriate correction for improving the estimated speed. Simulation and experimental results were carried out for the proposed control system. An induction motor fed by voltage source inverter was used in the experimental system. A digital signal processor and field-programmable gate arrays were used to implement the control algorithm.     

Magnetic Equivalent Circuit Modeling of Induction Motors

Finite element models are invaluable for determining expected machine performance. However, finite element analysis can be computationally intense; particularly if a large numbers of studies or high bandwidth studies are required. One method to avoid this difficulty is to extract machine parameters from the finite element model and use the parameters in lumped parameter models. While often useful, such an approach does not represent space harmonics or asymmetries in the motor. A methodology for constructing a state-variable model, based on a magnetic equivalent circuit of the motor is described herein. In addition, the parameters for this model are based solely on geometrical data. This approach is an excellent compromise between the speed of lumped parameter models and the ability of finite element methods to capture spatial effects. Experimental validation of the model is provided.     

Optimal Slot Opening Width for Magnetic Noise Reduction in Induction Motors

This paper presents a method to characterize the main magnetic force waves occurring in a sinusoidally fed induction machine. Three main force types are identified: slotting force waves, winding force waves, and saturation force waves. Slotting force waves are characterized in terms of number of nodes, velocity, propagation direction, and magnitude. On the ground of the expression of these forces magnitude, a method to cancel a given magnetic force wave by properly choosing the rotor slot or stator slot opening width is presented. This new method is validated with both simulations and experiments. Contrary to the common design rule that advices to decrease rotor and stator slot openings width in order to reduce magnetic noise, it is shown that a wider slot opening can lower the global noise level when properly chosen.      

抽油机用电动机和外加装置的节能运行分析

电网直接供电的普通三相异步电机的特点与抽油机负载的需求不匹配,是抽油机系统效率低下的根源。对电动机进行改进或外加节能装置,可以实现一定程度的节能运行,但往往又会引起新的问题。抽油机系统是比较复杂的系统,系统的节能不仅取决于电动机的效率,而且与输电线路上的损耗、对电网的谐波污染、生产工艺、可靠性及成本等因素有关。本文从系统的角度详细分析了抽油机常用的各种电动机和外加节能装置的节能原理与优缺点,对其进行综合评价,为抽油机节能装置的改进或研制提供借鉴。     

A New Longitudinal End Effect Factor for Linear Induction Motors

The longitudinal end effect in a linear induction motor (LIM) is analysed assuming two travelling magnetic flux density waves in the airgap: the wave travelling with synchronous velocity and the wave representing end effect [1]. A simple equation for the end effect factor which modifies the airgap EMF is obtained, and a simple equivalent circuit incorporating the end effect factor is established. Analysis is compared with measurements from two largescale single-sided LIM's. The equation for the end effect factor is sufficiently accurate to be used for design studies of LIMs. Since end effects are negligible at low speeds, the end effect factor has application for medium and high-speed LIMs.     

Magnetic and Dimensional Properties of Axial Induction Motors

A rotating magnetic field model of the axial induction motor is developed relating the geometric properties of the stator/rotor core. The main geometric dimensions of different type induction motors are compared using the field model formulas. An axial induction motor constant is derived from the output power formula. A new expression for the output power per unit volume is achieved by means of main dimensions and construction modification. A flowchart with stationary input data anticipates the assigned computed parameters of the axial induction motor.     

电动汽车用电动机的发展概况

描述了目前电动汽车用电动机的需求背景,分析了电动汽车对电动机的特殊使用要求,对常用的电动汽车用电动机进行了分类和比较,简述了目前国内电动汽车用电动机的研发现状,并对以后的前景进行了展望。     

Simulation Studies of the Transients of Squirrel-Cage Induction Motors

A new simulation approach is proposed in consideration of a saturation and a deep bar effect for the study of transients of three-phase squirrel-cage type induction motors. The mathematical model of an induction motor is expressed by the six differential equations of three-phase instantaneous voltage and current. The torque of an electric equation is related to the motion equations of motor and driven machine in the mathematical model. The values of reactance of stator and rotor are changed by the saturation of core caused by starting current. Also both the values of reactance and resistance of rotor bar are varied by the deep bar effect in the rotor core during starting. The calculation method of circuit constant that adds the influence of saturation and deep bar effect is proposed in this paper. The circuit constant of simulation model in consideration of saturation and the deep bar effect are decided by these computation methods in accordance with the conditions of rotation speed and current. If the large current flows, the leakage reactance of the stator and the rotor decreases by saturation. Moreover, the resistance of the rotor gradually decreases when the rotational speed rises from stop to synchronous speed, and the leakage reactance increases gradually. The calculated values were compared with the observed values of the examination machine of 1100 kW4P and an excellent agreement was obtained demonstrating the accuracy of the proposed simulation. Consequently, it is shown that the saturation and the deep bar effect are the essential factors to perform the accurate simulations of the induction motor. After checking the validity of the proposed approach, the simulation of the grounding faults was performed. In this study, all the simulation programs have been developed in the Matlab/Simulink environment.     

Analysis of Repairs on Three-Phase Squirrel-Cage Induction Motors Performance

This paper presents the results of research conducted to assess the effects of preventive maintenance and repairs on three-phase squirrel-cage induction motor performance regarding energy efficiency. The results brought interesting insights on how simple tasks can improve the energy efficiency, both in industry and in repair shop procedures.     

On the Choice of Phase-Balancer Capacitance for Induction Motors Fed from Single-Phase Supply

This paper presents analytical evaluation for performance characteristics of a three phase induction motor when fed from a single phase supply. Starting as well as running of such motor are achieved by connecting a capacitor across two of stator phases in a way to act as a phase converter. Symmetrical components concept was employed in the analysis. The influence of capacitor value on motor characteristics is being investigated showing that there exists an optimum value of capacitor for a specific characteristic. Formulas are then derived for calculating these optimum values and recommendations are given for proper choice of capacitor rating and value.     

Non-Simultaneous Reclosing Air-Gap Transient Torque of Induction Motor: Part I, Analysis and Computation Logic

Non-simultaneous reclosing of an induction motor involves three transient steps: the switching off, the reclosing of two of the three switch poles, and the reclosing of the third pole. Each step is initiated and superimposed successively to give a complete transient picture. The analysis and the computation logic are given in this part. The application of the analytical results and the discussion of the American National Standard, ANSI C50.41, for reclosing of induction motors, are given in Part II.