Mohammadhossein Arianborna, Jawad Faiz, Mehrage Ghods and Amirhossein Erfani-Nik
The aim of this paper is to introduce an accurate asymmetric fault index for the diagnosis of the faulty linear permanent magnet Vernier machine (LPMVM).
Abstract
Purpose
The aim of this paper is to introduce an accurate asymmetric fault index for the diagnosis of the faulty linear permanent magnet Vernier machine (LPMVM).
Design/methodology/approach
Three-dimensional finite element method is applied to model the LPMVM. The geometrical and physical properties of the machine, the effect of stator and translator teeth, magnetic saturation of core and nonuniform air gap due to asymmetric fault are taken into account in the simulation. The air gap asymmetric fault is proposed. This analytical method estimates the air gap flux density of an LPMVM.
Findings
This paper presents an analytical method to predict the performance of a healthy and faulty LPMVM. The introduced index is based on the frequency patterns of the stator current. Besides, the robustness of the index in different loads and fault severity is addressed.
Originality/value
Introducing index for air gap asymmetry fault diagnosis of LPMVM.
Details
Keywords
Jawad Faiz and Farhad Rezaee-Alam
The purpose of this paper is to present an improved winding function theory (IWFT) for performance analysis of surface mounted permanent magnet (SMPM) motors, which can precisely…
Abstract
Purpose
The purpose of this paper is to present an improved winding function theory (IWFT) for performance analysis of surface mounted permanent magnet (SMPM) motors, which can precisely and simultaneously consider the impacts of stator slotting, the winding distribution, the magnetic flux density within PMs because of the armature reaction, the PM magnetization angle and the magnetic saturation,.
Design/methodology/approach
To obtain this improved analytical model, the conformal mappings (CMs) are introduced to calculate the relative complex permeance of slotted air-gap, which is used to obtain the function of slotted air-gap length. The equivalent magnetizing current model is used to extract the equivalent winding function for each PM pole. For retaining the basic assumption of WFT, the magnetic saturation is also considered by a proper increase in the air-gap length in the front of the stator teeth.
Findings
A new hybrid analytical model (HAM) based on WFT is presented in this paper, which can simultaneously and accurately consider the effects of slotting, the magnetic saturation, the variation of PM operating point and the winding distribution. In fact, IWFT removes all the drawbacks of the conventional WFT. Moreover, IWFT is more user-friendly and faster than other analytical and numerical techniques.
Practical implications
The obtained HAM can be used for design, optimization and fault diagnosis in electric machines.
Originality/value
This paper presents a new HAM for accurate modeling the SMPM motors, which includes different considerations of electromagnetic modeling. This new HAM can also be used for modeling the other electric motors.
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Mohammad Ali Taghikhani and Zahra Taghikhani
Using appropriate solution techniques for transformer inrush current transient study is of great prominence owing to the inevitable inclusion of differential equations leading to…
Abstract
Purpose
Using appropriate solution techniques for transformer inrush current transient study is of great prominence owing to the inevitable inclusion of differential equations leading to complicated analysis procedures. This study aims to propose an analytical-numerical method to accurately analyze the three-phase three-limb core-type transformer inrush current in different cases considering the nonlinear behavior of the iron core.
Design/methodology/approach
The proposed method focuses on acquiring equations for inrush current and also the magnetic core flux by the application of a simulation-based iterative approach. In this regard, multiple integral equations are solved taking the time intervals into account. Then several derivations and integrations of matrix terms are substituted into the obtained results so as to simplify the solution process.
Findings
The method provides notable enhancements in computation time and also excellent qualities of accuracy compared with conventional numerical methods.
Practical implications
The proposed method is simulated for two three-phase transformers via MATLAB software. The obtained simulation results have been also compared with experimental tests.
Originality/value
Actually, the analytical-numerical method is capable of computing higher number of iterations in a shorter time efficiently, while making use of the conventional numerical procedures may not result in expected convergences. The simulation results of the proposed analytical-numerical technique illustrate a close agreement with the experimental test, and hence, verify the method preciousness.
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F.A. Faiz, J.S.K. Ngo and K.B. Bujang
This study aims to improve the natural dyeing recipe with better light fastness using ascorbic acid (vitamin C) with pulverised plant dyes.
Abstract
Purpose
This study aims to improve the natural dyeing recipe with better light fastness using ascorbic acid (vitamin C) with pulverised plant dyes.
Design/methodology/approach
Silk fabrics pre-mordanted with alum (aluminium ammonium sulphate) were dyed using six types of plant dyes available in Sarawak, Malaysia, namely, Engkerabai leaves (Psychotria viridiflora), Ketapang leaves (Terminalia catappa), mangrove bark (Ceriops tagal), Sepang wood (Caesalpinia sappan), mangosteen husk (Garcinia mangostana) and onion skin (Allium cepa). Then, the dyed samples were immersed in vitamin C. The dyed and vitamin C-treated silk samples were exposed to direct sunlight for 40 h to test whether vitamin C had any effect on the light fastness of the dyed samples.
Findings
It was found that the fabric samples using vitamin C for after-treatment, particularly Engkerabai, Ketapang, mangrove and mangosteen, exhibited better light fastness. The colours of the four samples changed and looked darker when compared to the non-treated fabric samples. However, it was observed that vitamin C had a reverse effect on Sepang wood and onion skin. The acidic aqueous solution of vitamin C discharged the dyed samples instead.
Originality/value
In conclusion, depending on the plant types, vitamin C can be used to improve the light fastness of natural dyes or as a reducing agent for natural dyes.
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Mohsen Rostami, Peyman Naderi and Abbas Shiri
The aim of this paper is to propose the model for analyzing the electromagnetic performances of permanent magnet vernier machines (PMVMs) under healthy and faulty conditions.
Abstract
Purpose
The aim of this paper is to propose the model for analyzing the electromagnetic performances of permanent magnet vernier machines (PMVMs) under healthy and faulty conditions.
Design/methodology/approach
The model uses interconnected reluctance network formed based on the geometrical approximations to predict magnetic performances of the machine. The network consists of several types of reluctances for modeling different parts of machine. Applying Kirchhoffs laws in the network and the machine windings, magnetic and electrical equations are obtained, respectively. To construct the model system of equations, the electrical equation is converted into algebraic form by using the trapezoidal technique. Moreover, the system of equations must be solved by Newton–Raphson method in each step-time because of considering the core saturation effect.
Findings
The proposed model is developed based on the modified magnetic equivalent circuit (MEC) method, in which the number of flux paths in different parts of the machine can be arbitrary selected. The saturation effect, skewed slots, the desired machine geometrical parameters and various winding arrangements are included in the proposed model; therefore, it can evaluate the time and space harmonics in modeling the PMVMs. Furthermore, a pattern for inter-turn fault detection is extracted from the stator current spectrum. Finally, 2 D-finite element method (FEM) and 3 D-FEM analysis are carried out to evaluate and verify the results of the proposed MEC model.
Originality/value
Generally, the element numbers have important role in modeling the machine and calculating its performance. Hence, the proposed MEC model’s capability to choose desired number of flux paths is advantage of this paper. Moreover, the developed MEC can be used for analyzing several electrical machines, including other types of vernier machines, with simple modification.
Details
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Manuel Pineda-Sanchez, Angel Sapena-Baño, Juan Perez-Cruz, Javier Martinez-Roman, Ruben Puche-Panadero and Martin Riera-Guasp
Rectangular conductors play an important role in planar transmission line structures, multiconductor transmission lines, in power transmission and distribution systems, LCL…
Abstract
Purpose
Rectangular conductors play an important role in planar transmission line structures, multiconductor transmission lines, in power transmission and distribution systems, LCL filters, transformers, industrial busbars, MEMs devices, among many others. The precise determination of the inductance of such conductors is necessary for their design and optimization, but no explicit solution for the AC resistance and internal inductances per-unit length of a linear conductor with a rectangular cross-section has been found, so numerical methods must be used. The purpose of this paper is to introduce the use of a novel numerical technique, the proper generalized decomposition (PGD), for the calculation of DC and AC internal inductances of rectangular conductors.
Design/methodology/approach
The PGD approach is used to obtain numerically the internal inductance of a conductor with circular cross-section and with rectangular cross-section, both under DC and AC conditions, using a separated representation of the magnetic vector potential in a 2D domain. The results are compared with the analytical and approximate expressions available in the technical literature, with an excellent concordance.
Findings
The PGD uses simple one-dimensional meshes, one per dimension, so the use of computational resources is very low, and the simulation speed is very high. Besides, the application of the PGD to conductors with rectangular cross-section is particularly advantageous, because rectangular shapes can be represented with a very few number of independent terms, which makes the code very simple and compact. Finally, a key advantage of the PGD is that some parameters of the numerical model can be considered as additional dimensions. In this paper, the frequency has been considered as an additional dimension, and the internal inductance of a rectangular conductor has been computed for the whole range of frequencies desired using a single numerical simulation.
Research limitations/implications
The proposed approach may be applied to the optimization of electrical conductors used in power systems, to solve EMC problems, to the evaluation of partial inductances of wires, etc. Nevertheless, it cannot be applied, as presented in this work, to 3D complex shapes, as, for example, an arrangement of layers of helically stranded wires.
Originality/value
The PGD is a promising new numerical procedure that has been applied successfully in different fields. In this paper, this novel technique is applied to find the DC and AC internal inductance of a conductor with rectangular cross-section, using very dense and large one-dimensional meshes. The proposed method requires very limited memory resources, is very fast, can be programmed using a very simple code, and gives the value of the AC inductance for a complete range of frequencies in a single simulation. The proposed approach can be extended to arbitrary conductor shapes and complex multiconductor lines to further exploit the advantages of the PGD.
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Um-e-Rubbab, Shazia Faiz, Samyia Safdar and Namra Mubarak
Thriving at work can affect eustress and distress differently, so the main purpose of this study is to determine the impact of thriving at work on stress and to extend the…
Abstract
Purpose
Thriving at work can affect eustress and distress differently, so the main purpose of this study is to determine the impact of thriving at work on stress and to extend the existing literature on stress by examining the mediating mechanism of career growth, which is one of the functions of human resource development, in the relationship between thriving at work and stress. Person environment fit theory is used to explain the framework.
Design/methodology/approach
Data were collected from 179 employees of the hospitality sector of Pakistan to assess the impact of thriving at work on eustress and distress through the mediation of career growth. Structural equation modeling was used to test the hypotheses.
Findings
Results revealed thriving at work is positively related to eustress whereas it is negatively related to distress, and there is a positive association between thriving and career growth. Furthermore, career growth appeared as an effective explanatory mechanism for relationships between thriving at work and stress. Implications for managers are also discussed.
Originality/value
This study encompasses both positive and negative stressors. There are lots of studies available that examine thriving at work and stress, but the present study aims to examine the impact of thriving on both aspects of stress in the presence of career growth as the mediator in the hospitality sector of Pakistan. It also opens new avenues for research on P-E fit theory to gain benefit from the eustress of employees.
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Christopher Raymond and Paul R. Ward
This chapter explores theory and local context of socially constructed pandemic fears during COVID-19; how material and non-material fear objects are construed, interpreted and…
Abstract
This chapter explores theory and local context of socially constructed pandemic fears during COVID-19; how material and non-material fear objects are construed, interpreted and understood by communities, and how fears disrupt social norms and influence pandemic behavioural responses. We aimed to understand the lived experiences of pandemic-induced fears in socioculturally diverse communities in eastern Indonesia in the context of onto-epistemological disjunctures between biomedically derived public health interventions, local world views and causal-remedial explanations for the crisis. Ethnographic research conducted among several communities in East Nusa Tenggara province in Indonesia provided the data and analyses presented in this chapter, delineating the extent to which fear played a decisive role in both internal, felt experience and social relations. Results illustrate how fear emotions are constructed and acted upon during times of crisis, arising from misinformation, rumour, socioreligious influence, long-standing tradition and community understandings of modernity, power and biomedicine. The chapter outlines several sociological theories on fear and emotion and interrogates a post-pandemic future.
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Martin Petrun, Simon Steentjes, Kay Hameyer and Drago Dolinar
This paper aims to compare different static history-independent hysteresis models (mathematical-, behavioural- and physical-based ones) and a history-dependent hysteresis model in…
Abstract
Purpose
This paper aims to compare different static history-independent hysteresis models (mathematical-, behavioural- and physical-based ones) and a history-dependent hysteresis model in terms of parameter identification effort and accuracy.
Design/methodology/approach
The discussed models were tested for distorted-excitation waveforms to explore their predictions of complex magnetization curves. Static hysteresis models were evaluated by comparing the calculated and measured major and minor static hysteresis loops.
Findings
The analysis shows that the resulting accuracy of the different hysteresis models is strongly dependent on the excitation waveform, i.e. smooth excitations, distorted flux waveforms, transients or steady-state regimes. Obtained results show significant differences between predictions of discussed static hysteresis models.
Research limitations/implications
The general aim was to identify the models on a very basic and limited set of measured data, i.e. if possible using only the measured major static loop of the material. The quasi-static major hysteresis loop was measured at Bmax = 1.5 T.
Practical/implications
The presented analysis allows selection of the most-suited hysteresis model for the sought-for application and appraisal of the individual limitations.
Originality/value
The presented analysis shows differences in intrinsic mechanisms to predict magnetization curves of the majority of the well-known static hysteresis models. The results are essential when selecting the most-suited hysteresis model for a specific application.
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J. Faiz, H. Ehya, A.M. Takbash, S. Shojaee, M. Hamidian and A. Ghorbani
Electrical energy distribution systems must be low losses systems in order to enhance the system efficiency. Therefore, it is preferred to distribute electrical energy by…
Abstract
Purpose
Electrical energy distribution systems must be low losses systems in order to enhance the system efficiency. Therefore, it is preferred to distribute electrical energy by bus-ducts in the place of cables over all energy levels and decrease the losses. The purpose of this paper is to focus on a comprehensive survey of various aspects of bus-ducts design including electromagnetic, mechanical and thermal. Advantages and disadvantages of different available design techniques are reviewed.
Design/methodology/approach
Different works on various bus-based power transmission and distribution systems are reviewed. Generally these are done in three categories including systems modeling methods, heat transfer in the systems, short circuit and electromagnetic force. The attempt is made to provide geometrical and materials specifications in order to present the analyzed system well.
Findings
Different types of bus-ducts from used materials, voltage level and insulation types are reviewed. Bus-duct modeling techniques are introduced which can be easily applied for bus-ducts design. Electromagnetic field distribution, thermal pattern inside and outside of the bus-duct in normal and short circuit modes and finally mechanical considerations are dominant factors which must be taken into account in the bus-ducts design. This leads to an optimal design of bus-ducts which prolong the life span of the bus-ducts fixed in the installations.
Originality/value
This paper for the first time systematically reviews the latest state of arts in the design of bus-ducts for efficient electrical energy distribution. It summarizes a variety of design techniques applicable to bus-ducts design.