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This paper aims to give a perspective about the variety of techniques which are available and are being further developed in the area of coupled field formulations, with selective bibliography and practical examples, to help postgraduate students, researchers and designers working in design or analysis of electrical machinery.

This paper reviews the recent trends in coupled field formulations. The use of these formulations for designing and non‐destructive testing of electrical machinery is described, followed by their classifications, solutions and applications. Their advantages and shortcomings are discussed.

The paper gives an overview of research, development and applications of coupled field formulations for electrical machinery based on more than 160 references. All landmark papers are classified. Practical engineering case studies are given which illustrate wide applicability of coupled field formulations.

Problems which continue to pose challenges to researchers are enumerated and the advantages of using the coupled‐field formulation are pointed out.

This paper gives a detailed description of the application of the coupled field formulation method to the analysis of problems that are present in different electrical machines. Examples of analysis of generators and transformers with this formulation are presented. The application examples give guidelines for its use in other analyses.

The coupled‐field formulation is used in the analysis of rotational machines and transformers where reference data are available and comparisons with other methods are performed and the advantages are justified. This paper serves as a guide for the ongoing research on coupled problems in electrical machinery.

The purpose of this study is to calculate the frequency electric field in substation.

The paper proposes a novel fast multipole method (FMM) called Super-FMM to solve the PFEF problems in substations. The paper substitutes the original approaches for analytic expansions and translations through equivalent density representations.

The paper shows that the Super-FMM is more efficient in terms of the complexity of its storage spaces and computational costs compared with the best-known FMM when placed under scenarios with exactly the same error rates.

Using the fast Fourier transform algorithm can further improve the optimization algorithm and computational efficiency.

A novel FMM called Super-FMM is proposed, which has a structure similar to that of the adaptive FMM algorithm, but the paper substitutes the original approaches for analytic expansions and translations through equivalent density representations.

The paper seeks to present a methodology of computer simulation of 3D transient electromagnetic fields, losses and forces due to negative sequence currents in fragments of large synchronous turbogenerator rotors. The methodology allows for the preparation of initial data for further computations of thermal and mechanical behaviour of rotors.

The governing equations for 3D negative sequence transient electromagnetic fields with the Coulomb gauge using magnetic vector potential and scalar electric potential A, V – A are solved by the nodal finite element method in a Cartesian coordinate system moving synchronously with the rotor.

The presented methodology of 3D transient electromagnetic phenomena computation seems to be effective because the electromagnetic field in the rotor of a synchronous generator is generally three dimensional, and therefore 2D field‐computation approaches and software are not able to simulate intrinsically 3D electromagnetic processes in turbogenerator rotors.

Currently it is difficult to carry out accurate numerical simulation of 3D transient electromagnetic fields and therefore losses and forces within the whole structure of the rotor because of the resulting huge computational expenses. This paper is devoted to the finite element analysis of electromagnetic fields, losses and forces in separate structural parts of the rotor. As an example of practical utilization of the developed technique, the computer simulation of electromagnetic phenomena in junctions of nonmagnetic rotor slot wedges of a 300 MVA class synchronous turbogenerator is carried out.

The methodology can successfully be used during the design process of modern large synchronous turbogenerators.

This paper presents numerical analysis of intrinsically 3D transient electromagnetic phenomena in large turbogenerator rotors.

The purpose of this paper is to present analysis of short-circuit transients in a single-phase self-excited induction generator (SP-SEIG) for different capacitor topologies.

The paper presents field analysis of the short-circuit problem in the SP-SEIG on the base of two-dimensional field-circuit model of the generator.

The carried-out field computations of the tested SP-SEIG show that the self-excited induction generator is intrinsically protected from the results of sudden short-circuit, as output voltage and current drop rapidly to zero. Short-circuit is a problem when a series capacitor is used to improve output voltage regulation. Experimental results show that re-excitation of the generator is possible after the short-circuit is removed.

The originality of the paper is the presented analysis of short-circuit transients at terminals of SP-SEIG. A finite elements method-based field circuit model was used. The simulation results were validated by the measurements conducted on a laboratory test setup.

This study aims to evaluate the effectiveness of substituting different concentrations of sesame, soy butter, dried moringa leaves and coconut powder on the physicochemical and sensory properties especially calcium and protein content of salted and sweet cookies.

Cookies were prepared by fortifying refined flour with sesame (T1 and T3) and soy butter (T2 and T4) and further fortified with dried moringa leaves (salted) and coconut (sweet). Linear programing was used to formulate percentage of major ingredients to yield maximum calcium and protein. Cookies were evaluated for physical, textural, colour, nutritional, functional and organoleptic properties and compared with refined flour cookies, C1 (salted) and C2 (sweet).

It was observed that fortification significantly decreased the hardness of the test cookies when compared with control. C2 cookies were observed to be the hardest (42.3 N), whereas T2 cookies were the softest (23.7 N). Nutritional and functional components of fortified (T) cookies were significantly (p = 0.01) higher than control (C) cookies, and within T cookies, salted cookies were more nutritious than sweet cookies. Cookies fortified with sesame and dried moringa leaves (T1) contained the highest protein (19 g), calcium (312 mg) and flavonoids (2.0 QE mg/100g) content. Scores on sensory acceptability revealed that T cookies were highly acceptable when compared to cookies for all sensory attributes tested.

Incorporation of protein and mineral rich natural ingredients like sesame, soy butter, dried moringa leaves and coconut powder has improved the nutritional, functional and sensory properties especially calcium and protein content of salted and sweet cookies. There is tremendous scope for utilisation, commercialization of such plant-based nutrient dense ingredients in variety of food snacks, and this will ensure better nutritional security.

Fortification of biscuits with sesame, soy butter, dried moringa leaves and coconut powder resulted in to a superior quality of biscuits in terms of its protein, minerals specially calcium, flavonoid content and organoleptic acceptability. These protein and calcium rich biscuits may help in solving many nutritional deficiencies and can add variety to the bakery industry.

This paper aims to evaluate the effect of optimal use of rooftop photovoltaic (PV) systems on improving the loss of life (LOL) of distribution transformers, reducing power losses as well as the unbalance rate of the 69-bus distribution network.

The problem is studied in three scenarios, considering different objective functions as multi-objective optimization in balanced and unbalanced operations. Meta-heuristic golden ratio optimization method (GROM) is used to determine the optimal size of the rooftop PV in the network.

The simulation results show that in all scenarios, the GROM by optimally installing the rooftop PV is significantly capable to reduce the transformer distribution loss of loss, unbalance rate and power loss as well as reduce the temperature of the oil and transformer winding. Also, the lowest %LOL, power loss and unbalance rate occurred in the second scenario for the balanced network and first scenario, respectively. In addition, the results showed that the unbalance of the network results in increased power losses and LOL of the distribution transformer.

The better capability of GROM is proved compared with the grey wolf optimization algorithm with better objective function and by achieving better values of LOL, unbalance rate and power loss. The results also showed that the %LOL, unbalance and power losses are weakened compared to without considering the PV cost but the achieved results are realistic and cost-effective.

Although, numerous optimization algorithms have been devoted to construct an electrical ladder network model (ELNM), they suffer from some frail points such as insufficient accuracy as well as the majority of them are unconstrained, which result in optimal solutions that violate certain security operational constraints. For this purpose, this paper aims to propose a flexible-constraint coyote optimization algorithm; the novelty lies in these points: penalty function is introduced in the objective function to discard any unfeasible solution, an advanced constraint handling technique and empirical relationship between the physical estimated parameters and their natural frequencies.

Frequency response analysis (FRA) is very significant for transformer winding diagnosis. Interpreting results of a transformer winding FRA is quite challenging. This paper proposes a new methodology to synthesize a nearly unique ELNM physically and electrically coupled for power transformer winding, basing on K-means and metaheuristic algorithm. To this end, the K-means method is used to cluster the setting of control variables, including the self-mutual inductances/capacitances, and the resistances parameters. Afterward, metaheuristic algorithm is applied to determine the cluster centers with high precision and efficiency.

FRA is performed on a power transformer winding model. Basing on the proposed methodology, the prior knowledge in selecting the initial guess and search space is avoided and the global solution is ensured. The performance of the abovementioned methodology is compared using evaluation expressions to verify its feasibility and accuracy.

The proposed method could be generalized for diagnosis of faults in power transformer winding.

This study aims to evaluate the quality characteristics of low-fat functional carabeef cookies incorporated with different levels of guar gum.

Meat cookies were incorporated with 0.5, 1.0 and 1.5 per cent guar gum powder to replace 20, 30 and 40 per cent hydrogenated vegetable fat, respectively. The formulation of low-fat carabeef cookies was maintained by addition of water.

There was a significant difference (p < 0.02) between control and treatments for all physico-chemical properties, except pH and thickness. The cooking yield increased significantly (p < 0.04) at 1.5 per cent level of guar gum. Moisture, protein and ash percentage increased significantly (p < 0.02) while there was significant (p < 0.00) reduction in fat percentage. The diameter and spread ratio of cookies decreased significantly (p < 0.03) with incorporation of guar gum. The sensory scores were not significantly affected with respect to color and appearance, flavor, texture, crispiness, aftertaste and overall acceptability at 1.5 per cent level. There was no significant difference in hardness and adhesiveness values, as well as color parameters.

The experiment can be further carried out to evaluate complete product profile and storage stability of product under different packaging conditions.

Fat imparts richness and tenderness, improving flavor and mouth feel to processed meat products, but higher fat consumption may lead to various life style diseases. Reducing fat content with fat replacers in meat cookies without affecting the sensory characteristics may be a significant challenge. Guar gum powder may be an excellent option at 1.5 per cent level to replace 40 per cent of hydrogenated vegetable fat without compromising quality attributes.

The purpose of this paper is to present the original study of an industrial device. Industrial inductors are used to decrease the current variations, resulting from the use of modern power converters. To reduce these variations, the magnetic energy stored in these components is automatically used when the receptor is unconnected to the principal sources. Such storage is generally obtained by using a magnetic circuit containing air‐gaps. The rigidity of this circuit, associated with the magnetic stresses which appear in these areas, causes the structure to produce mechanical vibration and to emit audible sounds.

Experiments, simulations and test devices are used to determine the main physical phenomenon that generates the undesirable audible noise. The resulting knowledge is used to design a quieter device.

The mechanical vibrations and emitted noises are attached to magnetic effects. Even if it is not possible to suppress all these effects, the level of sound emitted can be decreased through a suitable design of the magnetic core.

Industrial inductors are usually built and designed using methods coming from the transformer studies. A new concept for the design of the magnetic core is presented. Experimental approaches and numerical simulations are performed in order to highlight the physical behaviours of the coils and their magnetic coupling to the magnetic core. It appears that breaking the magnetic core into free parts is an original solution that decreases the emitted noise.