Transient harmonic torques in induction machines: measurement and impact on motor performance

This paper focuses on the measurement of transient torques produced by the field harmonics in three phase squirrel cage motors and on the assessment of the operating conditions under which these torques might become significant. The paper presents first a model of the induction machine with any stator and rotor phase number and configuration, fed by arbitrary voltage waveforms and taking into account the space harmonics. Then, very much attention is paid to a reliable model validation against actual transient torques measurements. In this sense, the actual and great difficulties of measuring pulsating electromagnetic torques of several hundreds of Hertz are brought into light, the possible measurement techniques are critically reviewed and the solution chosen is discussed. Once the model accuracy has been experimentally confirmed, it is used to carry out a systematic plan of more than 250 simulations under clearly distinct operating conditions on five different motors. The analysis of these simulations yields a main practical conclusion: field harmonics may have (depending on the motor structure) a significant impact on electromagnetic torque, but only during transients characterized by high instantaneous frequencies of the rotor currents. For low slip transients, their impact is negligible. This conclusion is also theoretically justified in the paper.Echeverria Villar, JA.; Martínez-Román, J.; Serrano Iribarnegaray, L. (2012). Transient harmonic torques in induction machines: measurement and impact on motor performance. Electrical Engineering. 94(2):67-80. doi:10.1007/s00202-011-0216-4S6780942White D, Woodson H (1959) Electromechanical energy conversion. Wiley, LondonTaegen F, Hommes E (1972) Das allgemeine Gleichungssystem des Käfigläufermotors unter Berücksichtigung der Oberfelder. Teil I and II. 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Analysis and Diagnostics of Adjacent and Nonadjacent Broken-Rotor-Bar Faults in Squirrel-Cage Induction Machines

In this paper, faults associated with the rotor of an induction machine are considered. More specifically, effects of adjacent and nonadjacent bar breakages on rotor fault diagnostics in squirrel-cage induction machines are studied. It is shown that some nonadjacent bar breakages may result in the masking of the commonly used fault indices and, hence, may lead to a possible misdiagnosis of the machine. A discussion of the possible scenarios of these breakages as well as some conclusions regarding the types of squirrel-cage induction machines (number of poles, number of squirrel-cage bars, etc.) that may be more prone to these nonadjacent types of failures are presented. This discussion is supported through both simulation and experimental results. It is also shown that secondary fault effects can be used to diagnose such nonadjacent bar breakages

An Interface Design for Axial Induction Motor

Asynchronous motors have been used extensively in the industry since the first discovery. Although the general working principles do not change, they can be made geometrically in the form of cylinders, spheres, cones and even discs. One of these geometries is known as axial flux machine topology which has a disc structure. Axial flux machines are remarkable in terms of their high efficiency, high power density and advantage in terms of compact structures. In this study, extended literature search of axial flux induction motor is given. In addition to the literature, axial induction motor design interface has been created by using MATLAB GUI software. This interface can communicate with ANSYS Maxwell. Thus, the dimensioning values of the machine calculated via the interface can be drawn automatically in Ansys Maxwell and it can perform numerical analysis. The obtained torque, current and efficiency data were evaluated

Parameter estimation of squirrel-cage motors with parasitic torques in the torque–slip curve

This paper studies parasitic torques in steady-state torque–slip curves of squirrel-cage induction motors. The curves of nine motors (small, medium and large size units), three of which were measured in the range s = 2 to 0, are analysed. The torque–slip curves of eight of these nine motors differ significantly from the smooth curves predicted by the classical single- and double-cage models: a torque dip at large slips in the motoring regime and a notable torque increase in the braking regime occur. As parasitic torques have been traditionally associated with space harmonics, two singlecage chain models (which consider the space harmonics) are tested to fit the measured torque and current of the three measured motors: one neglects the skin effect, leading to the wrong torque prediction, whereas the other (the chain model proposed in the early 60s in the literature) considers the skin effect, leading to an accurate torque prediction.Postprint (author's final draft

A Review of Techniques Used for Induction Machine Fault Modelling

[EN] Over the years, induction machines (IMs) have become key components in industry applications as mechanical power sources (working as motors) as well as electrical power sources (working as generators). Unexpected breakdowns in these components can lead to unscheduled down time and consequently to large economic losses. As breakdown of IMs for failure study is not economically feasible, several IM computer models under faulty conditions have been developed to investigate the characteristics of faulty machines and have allowed reducing the number of destructive tests. This paper provides a review of the available techniques for faulty IMs modelling. These models can be categorised as models based on electrical circuits, on magnetic circuits, models based on numerical methods and the recently proposed in the technical literature hybrid models or models based on finite element method (FEM) analytical techniques. A general description of each type of model is given with its main benefits and drawbacks in terms of accuracy, running times and ability to reproduce a given faultThis work was supported by the Spanish "Ministerio de Ciencia, Innovacion y Universidades (MCIU)", the "Agencia Estatal de Investigacion (AEI)" and the "Fondo Europeo de Desarrollo Regional (FEDER)" in the framework of the "Proyectos I+D+i-Retos Investigacion 2018", project reference RTI2018-102175-B-I00 (MCIU/AEI/FEDER, UE)Terrón-Santiago, C.; Martinez-Roman, J.; Puche-Panadero, R.; Sapena-Bano, A. (2021). A Review of Techniques Used for Induction Machine Fault Modelling. Sensors. 21(14):4855-4873. https://doi.org/10.3390/s21144855S48554873211

Semi-Analytical Approach Towards Design and Optimization of Induction Machines for Electric Vehicles

Electric machine design is a comprehensive task depending on the several factors, such as material resource limitations and economic factors. Therefore, an induction machine is a promising candidate because of the absence of magnetic material in the rotor. However, the conventional design approach can neither reflect the advances of the induction machine(IM) design nor exploit the trade-offs between design factors and the multi-physics nature of the electrical machine. Therefore, proposing fast and accurate novel methods to design, develop and analyze IMs using electromagnetic field oriented approaches is competitive to the old-fashion numerical methods. To achieve improved IM design from a baseline design to an optimal design, this dissertation: (1) Investigates the challenges of the high speed IM design specified for the electric vehicle application at the rated operating condition considering electromagnetic boundaries for the reasonable saturation level within a compact volume; (2) Proposes a new design approach of IM using modified equivalent circuit parameters to reduce spatial harmonics because of slotting effect and skewing effect; and also presents the importance of the 3-D analysis over 2-D analysis while developing the IM; (3) Proposes a novel electromagnetic field oriented mathematical model considering the slotting effect and axial flux variation because of skewing rotor bars to evaluate the IM performance with a lower and precise computational effort; (4) developed baseline IM is optimized with genetic algorithm incorporated in proposed subdomain model to improve the torque-speed profile. In order to further simplify the optimization procedure, a parametric and sensitivity based design approach is implemented to reduce the design variables. To evaluate the proposed optimal IM with extended constant power region and high torque density within a compact volume using novel 3-D subdomain model, the machine has been prototyped and tested from low to high speed under no-load and loaded condition. Electrical circuit parameter variation is demonstrated and compared to the one simulated in the FEA environment. This innovation can be applied to a family of electric machines with various topologies

Advanced Non-Overlapping Winding Induction Machines for Electrical Vehicle Applications

This thesis presents an investigation into advanced squirrel-cage induction machines (IMs), with a particular reference to the reduction of the total axial length without sacrificing the torque and efficiency characteristics and analysis of recently found non-sinusoidal bar current phenomenon, which occurs under some certain design and operating conditions, and affects the overall performance characteristics of the IMs. As a first step, the most convenient method is determined by utilizing a fractional-slot concentrated winding (FSCW) technique, which has advantages such as non-overlapping windings, high slot filling factor, and simple structure. After implementing this technique, it is found that due to the highly distorted magnetomotive forces (MMFs) created by the FSCWs, significant high rotor bar copper loss occurs. In order to reduce the MMF harmonics without increasing the size of the machine, a new technique titled “adapted non-overlapping winding” is developed. This technique consists of the combination of the auxiliary tooth and phase shifting techniques, resulting in a stator with concentrated windings of two-slot coil pitches but without overlapping the end-windings. Thanks to this method a large number of the MMF harmonics are cancelled. Thus, a low copper loss IM with significantly reduced total axial length is obtained. Influence of design parameters; such as stator slot, rotor slot, and pole numbers, number of turns, stack length, stator and rotor geometric parameters, etc. on the performance characteristics of the advanced IM is investigated and a comprehensive comparison of advanced and conventional IMs is presented. This thesis also covers an in-depth investigation on the non-sinusoidal bar current phenomenon. It is observed that the rotor bar current waveform, usually presumed to be sinusoidal, becomes non-sinusoidal in some operation and design conditions, such as high speed operation close to synchronous speed, or fairly high electrical loading operation, or in the IMs whose air-gap length is considerably small, etc. Influences of design and operating parameters and magnetic saturation on the rotor bar current waveform and the performance characteristics of squirrel-cage IMs are investigated. The levels of iron saturation, depending on the design and operating parameters, in different machine parts are examined and their influences are also investigated, whilst the dominant part causing the non-sinusoidal rotor bar current waveform is identified. It is revealed that the magnetic saturation, particularly in the rotor tooth, has a significant effect on the bar current waveform

A Model for Induction Motors with Non-Uniform Air-Gap

Equations to calculate inductances of induction motors, considering non-uniform air-gap, are proposed. The analyzed air-gap variations are static and dynamic eccentricity and stator slots. The equations for inductance calculation, obtained from the modified winding functions and the energy stored in the air-gap, allow considering the effect of rotor bar skewing. Experimental results that validate the proposed method are presented.Fil: Bossio, Guillermo Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ingeniería. Grupo de Electrónica Aplicada; ArgentinaFil: de Angelo, Cristian Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ingeniería. Grupo de Electrónica Aplicada; ArgentinaFil: Solsona, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Garcia, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ingeniería. Grupo de Electrónica Aplicada; ArgentinaFil: Valla, Maria Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentin