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Induction motors, particularly single‐phase induction motors (SPIMs), represent the major consumption of power in the household sector. SPIMs that fail during their life cycle represent the best opportunity to improve their efficiency by replacing or repairing them. Although replacing faulty motors with new and efficient ones results in significant energy savings, this replacement is uneconomical due to its high initial costs. Additionally, this option requires extensive energy and materials to manufacture, resulting in a considerable environmental impact. This article aims to introduce a three‐phase rewinding of a failed SPIM using a rewinding algorithm that significantly improves the machine's efficiency and performance in an economically viable way. The 0.75 HP single‐phase capacitor‐start induction motor has been rewound to convert it into a three‐phase motor with the required 110 V line voltage and 50 Hz frequency. The economic analysis implies that the rewound machine's life‐cycle cost is 6% and 18% lower than the purchased SPIM IE1 and existing SPIM by below efficiency class respectively. The rewound motor achieves a payback period of 1–1.6 years for different motor loading levels, based on the world average electricity price, indicating an economically viable solution. [ABSTRACT FROM AUTHOR]

This paper investigates a novel online method for static eccentricity (SE) fault detection of single-stator–single-rotor axial flux permanent-magnet (AFPM) machines. The method allows for both estimating the SE factor and computing the minimum air-gap position. As direct flux measurements are expensive, the proposed method for fault detection is based on the measurement of the voltages of three search coils uniformly distributed in the air gap. Unlike the current spectrum-based fault detection methods on which the winding configuration has a considerable impact, the proposed method can be used for any type of AFPM machine independently on the winding layout. A simplified 2-D analytical approach is used. Moreover, a circuit-coupled 3-D finite-element method (FEM) was used to compute the induced voltages in the search coils and show the validity of the method through 20 eccentric scenarios. Moreover, an experimental setup was built to validate the analytical approach and to confirm the results achieved with the 3-D FEM. Several experimental measurements have been done. All measurements confirm the accuracy of the proposed method. It is also shown that the method yields accurate results under any load condition. [ABSTRACT FROM PUBLISHER]

This paper studies static eccentricity (SE) fault detection in axial-flux permanent-magnet (AFPM) machines using 3-D finite-element analysis. The use of numerical modeling makes it possible to precisely study the eccentricity fault detection in these types of machines. The simulations are validated using experimental measurements. To the best knowledge of the authors, SE fault detection in AFPMs has not been studied before. Hence, a new definition for the SE factor is presented in these types of machines. A motor with different degrees of rotor eccentricity is simulated, and the back electromotive force (EMF) of all coils of the stator is obtained. In addition, an appropriate criterion has been presented for the fault detection using the back EMF of the coils. This study indicates that the back EMF of the coils of the stator is a good criterion for eccentricity fault detection. It is observed that the unbalanced back EMF suggests a method for the indirect measurement of eccentricity that could be carried out during manufacturing and assembling processes or maintenance operation. [ABSTRACT FROM AUTHOR]

This paper studies the effects of static eccentricity on axial flux permanent-magnet machines (AFPMMs) using three-dimensional finite-element analysis (3-D FEA). Use of numerical modeling makes it possible to precisely study the eccentricity in these types of machines. The accuracy of the FEM model is validated using experimental measurement. To the best awareness of the authors, effects of static eccentricity in AFPMMs have not been studied before. Hence, a new definition for the static eccentricity factor (SEF) is presented and it is shown that the occurrence of static eccentricity is very high in these types of machines. A motor with different degrees of rotor eccentricity is simulated and the flux density distribution in the air gap and the total axial force between rotor and stator is obtained. In addition, unbalanced magnetic force (UMF) is calculated and it is mentioned that a steady torque is created by the forces. This study indicates that static eccentricity has noticeable effects on motor characteristics and can deteriorate the motor performances. [ABSTRACT FROM PUBLISHER]

Here, the authors present a new constrained multi‐objective optimization method for maximizing output power and efficiency of switched reluctance motor (SRM). The constraints play a significant role in this process. Artificial neural network‐based models are created to represent the SRM behaviour which is a difficult task. For this reason, a single neural network for each objective is built and the number of training data has been increased to reach a good accuracy. The authors propose a neural network‐based adjoint Lp metric technique to combine several objective functions and constraints with different weight factors to a single function which should be minimized. To apply the constraints, an adjoint term is added to the original Lp function including only objective functions. The flux densities of the magnetic materials are selected as the optimization constraints. When approaching as close as possible to the saturation level, the SRM has a better performance. Adding an adjoint term to the original Lp leads to better optimization results which were proved by comparing with a conventional optimization. Also, all obtained results were finally validated by the Ansoft Maxwell software. [ABSTRACT FROM AUTHOR]

The results of numerical and experimental analysis of passive magnetic bearings are presented. The proposed structure is composed of three radially stacked ring‐shaped permanent magnets. The improvements of stiffness and load capacity are proven in comparison to the classical passive magnetic bearing composed of two rings. A preliminary sensitivity analysis is carried out by means of the 2‐dimensional finite element method (FEM) modelling, which is used to provide the initial points for the stochastic optimisation and also to define the best fitness and penalty functions. Finally, the 2‐dimensional FEM is used to compare the force density and the cost of the proposed structure to those of the classical passive magnetic bearing composed of two rings. The optimised structure was manufactured and validated by experimental measurements. The proposed passive magnetic bearing exerts greater axial force and stiffness than similar structures. [ABSTRACT FROM AUTHOR]

The present study investigated the design, simulation, and manufacturing of a new coreless stator axial‐flux permanent‐magnet motor. In addition, to magnets with magnetisation along the motor axis, the new structure included magnets that were magnetised circumferentially and buried at the rotor surface. The electromagnetic design of the conventional axial‐flux motor and the new motor was evaluated according to nominal values and design equations. In this regard, the number of poles and coils, as well as the outer diameter of both motors were assumed to be identical. It was observed that the axial length of the new motor is shorter than the conventional axial‐flux motor. Simulations were continued through comparing the motors in terms of air‐gap flux density, torque, and back electromotive force using the transient finite element method. A comparison of the results showed that the new motor had a better performance than the conventional axial‐flux motor. Subsequently, the new motor was manufactured and tested; the experimental results proved to be close to those presented in the analytical section. [ABSTRACT FROM AUTHOR]

Background: Permanent magnet machines can be used for many applications, due to their high power density, high efficiency, observable torque‐to‐current ratio, and low maintenance cost. As such, the generator design in wind turbine systems is highly dependent on improvement of efficiency and generator performance. Thus, in order to improve the quality of manufactured electrical machines, a robust and precise optimization model should be developed to substitute the traditional deterministic models. Purpose: This paper investigated the optimization design process of an interior permanent magnet synchronous generator (IPMSG) for wind power systems using the finite element analysis (FEA) based on a prototype IPMSG. To that end, a multi‐objective optimization design of a permanent magnet generator (PMG) based on Taguchi method was proposed. Design/Method: The influence of the pole arc angle, magnet inset, magnet thickness, magnet width, and stator tooth width as well as slot depth were considered as the design parameters. The main characteristics of generator efficiency, total harmonic distortion (THD) and the amplitude of induction electromotive force (EMF) were taken as the optimization objectives, as well. The orthogonal matrix was established based on the number of the selected variables and the level factor of each variable, and finite element method (FEM) was, in turn, applied to solve the experimental matrix. As a result, an improved generator with higher maximum efficiency and EMF and lower THD was designed. Conclusions: Finally, the prototype IPMSG which was manufactured based on the analysis results and Taguchi method was tested. The experimental tests were then performed to confirm the validity of the proposed design process and the generator efficiency. The prototype experiments and the finite element simulation results verified the efficacy of the optimization method. [ABSTRACT FROM AUTHOR]

Highlights • AC loss of HTS coil under nonsinusoidal current. • Comparison with sinusoidal shows higher AC losses in the same peak current for nonsinusoidal current. • The investigation on loading factor and some discussions on quench. • Proper to use for superconducting machine design. Abstract Nowadays in the competitive generation and consumption electrical network, the efficiency is the key elements which should be carefully considered before purchasing electrical machines. It is not only important for achieving a better performance but also to keep the total ownership cost of the machine as low as possible. For this purpose, many research efforts have been done to involve superconducting material in electrical machine fabrication process. Recently, with continuous fast-development in production technology of second generation high temperature superconducting tapes, it is likely to achieve a very high efficiency with superconducting electrical machines. In order to investigate the efficiency, one needs to measure the losses of the superconducting wires under different operating conditions. It is quite common for an electrical machine to work under distorted supply current because they normally are driven with non-sinusoidal current of speed drives or supplying non-linear loads. In this paper, power loss of a double pancake high temperature superconducting coil which is supplied by harmonic-wave current has been experimentally measured and then, the results discussed which have shown, the power losses of distorted currents are wave-shape dependent and this loss decreases the loading ratio i.e. the ratio of operation current respect to critical current, significantly. [ABSTRACT FROM AUTHOR]

In recent years, there are fast-increasing concerns on the utilizations of superconducting rotating electrical machines in different application areas, such as ship propulsion systems, aircraft drivers, and wind turbine generators, since these machines exhibit the merits of high current density, compact design, high power density, light weight, high torque density as well as high efficiency. One of the main limitations in front of the vast use of superconducting tapes in the fabrication of electrical machineries is AC magnetizing loss when tapes are exposed to an external magnetic field, which can decrease the critical current density of wires, as well. In the literature, most of the research works have been done on calculation of the AC magnetizing loss under a pure external magnetic field, while in reality, magnetic flux lines in AC electrical machines are usually distorted with harmonics because of different reasons such as distorted leakage flux, distributed coils of a winding in several slots, cogging fields, mechanical faults, etc. Since these distorted fields contain harmonics, then in this paper, the AC magnetizing loss of superconducting tapes has been electromagnetically modeled and calculated when they are subjected to nonsinusoidally distorted external magnetic fields. The magnetic field dependency of critical current density has been considered in a proposed finite element model. The results have shown that the AC magnetizing loss increases significantly under a distorted applied field compared with a sinusoidal one. In addition, the loss increase depends on the harmonic content which would increases drastically with total harmonic distortion of the applied magnetic field. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) technology is the most promising, advanced, and beneficial technological developments of the last two decades in terms of fabricating more efficient, compact, and reliable electrical power apparatus. The second-generation HTS wires are now quite competitive with traditional conductors from the cost point of view. In addition, they are of high interest in electrical machine manufacturing due to their unique merits such as high current density, high magnetic field, and low loss. The most significant issue for any superconducting devices which work with alternating current or magnetic field is the AC loss of the HTS tapes. Since HTS tapes are always exposed to an external magnetic field in electrical machine applications, it is vital to consider the effect of this external field on their AC magnetizing (ACMG) loss. It is well-known that external magnetic field decreases the current carrying capability of the wire. In real life, critical current density of HTS tapes is dependent to magnetic field but this dependency sometime was not considered in modeling stage in order to make it faster and simple. In this paper, the electromagnetic properties of HTS tapes for use in superconducting electric machines have been investigated with a particular focus on the ACMG loss of YBCO tapes. For this purpose, a two-dimensional finite element model has been implemented based on the H formulation in order to study the effect of dependency of critical current density to magnetic field on the variation of ACMG loss. The modeling results will be helpful for electrical machine designers to have a better understanding about this effect and have a more accurate estimate of ACMG loss in design stage. [ABSTRACT FROM AUTHOR]

In this article, a new electro-thermal optimization algorithm is proposed to determine the parallel power cables arrangement to obtain the maximum ampacity. The optimization procedure is based on the imperialist competitive algorithm (ICA). Electrical calculations are performed using the sub-conductors method and consideration of the skin and proximity effects. FEM thermal model and electrical calculations are coupled with optimization procedure to determine the ampacity in the optimization algorithm. Optimized arrangements are determined under sinusoidal and harmonic load currents conditions. Furthermore, the effects of different boundary conditions of the ground surface such as isothermal and convective heat flux are evaluated. The underground single conductor cables with solid bonded metallic sheaths and existing of circulating currents are considered. Cables are considered to be installed adjacent to each other in different rows above each other in flat formations. Also, the artificial bee colony (ABC) optimization algorithm is performed to validate the ICA procedure. Experimental measurement of a case study is carried out for simulation confirmation and the results show good agreement. [ABSTRACT FROM AUTHOR]

Size and cost reduction are among the main issues of electric motor design and fabrication. This paper proposes an original layout for an axial flux permanent-magnet motor with printed circuit board (PCB) winding. In contrast to other axial flux motors of the same type, which are generally made with a three-phase fractional slot winding, the proposed motor has a two-phase wave winding printed on either side of the PCB. This configuration allows increasing the number of pole pairs and the supply frequency so to reduce the stator and rotor core widths. The winding is also characterized by a large copper percentage on the board, which improves the torque density of the motor. The results of the mathematical analysis, of the numerical simulation and of the experiments are compared. A method for the computation of the phase inductances is also proposed and validated. The main dimensions of the magnets are optimized via the finite-element method. The experimental comparison shows the advantages of the proposed motor in comparison to the traditional shaded pole motor for household applications. [ABSTRACT FROM PUBLISHER]

The current distribution, ampacity and magnetic field of parallel power cables are calculated. The calculations are performed in both sinusoidal and harmonic current profiles. The simulations are conducted on the underground medium voltage cables with metallic sheaths. The effects of single‐point bonding and solid bonding of sheaths grounding system are evaluated. In this study, cables are installed in flat formation with three cables in each phase and the effect of different distances between cables on the parallel cables parameters is studied. Computations are conducted for all possible arrangements of parallel cables and the worst and the best arrangements from the point of balancing current division, maximum ampacity and minimum magnetic field are presented. Furthermore, the effects of placing parallel cables in one row or two rows above each other are investigated. Calculations of current distribution and magnetic field are performed using the sub‐conductors method that considers the skin and proximity effects. Finite element method thermal simulations are excited to determine the power cable ampacity in different configurations. Experimental tests on parallel cables in both single‐point bonding and solid bonding systems are carried out and the results verify the accuracy of simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of metallic sheaths on alternating current (AC) losses and ampacity of power cables. The AC losses are expressed as AC/direct current (DC) resistance in power cables, which is the main factor in loss computations. With regard to the importance of harmonic contents of the currents, a comprehensive study is performed on AC/DC resistance of medium-voltage cables in the presence of harmonics. Different harmonic frequencies include triple and nontriple orders are considered. A derating factor is proposed on the basis of cable constructions. Two types of sheathed and unsheathed medium-voltage power cables are considered. Also for metallic sheathed cables, 2 types of sheath grounding are investigated. It is shown that single-point bonding and both-ends bonding of sheaths have different effects on cable ampacity in harmonic frequencies. Moreover, different conductor cross sections and distances between cables are considered, and their effects on AC/DC resistance and ampacity derating are assessed. It is shown that these factors have important effects on AC/DC resistance and thus power cable losses. Furthermore, all cases are investigated in both flat and trefoil formations that are the most popular formations in power cables. To achieve precise results, we performed this study on the basis of finite element simulation, which is an exact way to cable losses computations in each configuration. [ABSTRACT FROM AUTHOR]

Eccentric air-gaps occur very likely in wind generators as the turbines are subject to continued mechanical stresses. This article analyzes the effects of rotor eccentricity on axial flux permanent magnet machines’ performances, such as air-gap flux density, cogging torque, and unbalanced force. In modeling axial flux machines, three–dimensional finite-element method models are required for accurate calculations. However, three-dimensional finite-element analysis is usually time consuming. In order to have a quick evaluation of the axial flux machine performance suitable for online identification, an analytical approach that utilizes quasi three-dimensional computation is developed. The proposed method allows taking into account variation of tooth skewing and different magnet shapes. The results have been validated using two-dimensional and three-dimensional finite element computations. It is shown that by using the proposed analytical approach, it is possible to assess the performance of the axial flux permanent magnet generators under eccentricity with reasonable accuracy. [ABSTRACT FROM AUTHOR]

• Nonsinusoidal AC loss of superconducting tape/coil is investigated using finite element method. • Results are essential for all large scale applications of superconductivity. • Findings are useful for design of HTS transformers, and HTS power cables. • Harmonics increase the AC loss drastically and impose huge heat load to cryocooler. There are two main obstacles in front of the development of high temperature superconducting (HTS) technology for electric power network applications; tape price and cooling cost. In order to reduce cooling cost, it is vital to evaluate AC transport current loss of the tapes precisely and then reduce it by some design innovative approaches. In addition, AC transport current loss in HTS material is a critical design variable for large-scale power network applications such as HTS transformers, superconducting fault current limiters, and power cables, since they are continuously carrying the network/load current during their operating life. In existing power networks, harmonic production sources are commonly used and thus, currents are distorted. Therefore, the effect of nonsinusoidal current on the critical apparatus in the network such as transformer must be studied. In this paper, AC transport current loss of a single-turn 2G YBCO HTS coil was modeled and numerically calculated under nonsinusoidal transport current using finite element method. Furthermore, influence of dependency of critical current density to magnetic field on the AC transport current loss of HTS coil when carries distorted currents was considered. It was observed that nonsinusoidal current causes excessive losses in HTS coil. On the other hand, a case study on an HTS transformer supplying non-linear load was considered to study the loss increment as well as heat load change. It was observed that current harmonics increases the AC loss, and heat load of transformer and decreases the efficiency, consequently. [ABSTRACT FROM AUTHOR]