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In this paper a novel Radial-Axial (RA) Flux Switching Permanent Magnet Generator (FSPMG) is introduced. In contrast to other RA flux machines, a major advantage of this generator is its implementation only by the use of conventional Non-Oriented Electrical Steel Sheets (NOESSs), even though the flux linkage of the novel RA-FSPMG has a three-dimensional (3D) path. Besides that, it benefits from the flux concentration strategy and a passive rotor. A concrete foundation of the novel RA-FSPMG is provided, in which, the 3D-Flux path is described, working principles are discussed, and power-sizing equation is derived. No-load (NL) characteristics and the Full Load (FL) performance of an optimized RA-FSPMG are investigated in contrast to an optimized Double Stator Radial (DSR) FSPMG and an optimized Double Stator Axial (DSA) FSPMG with similar volume, number of Permanent Magnets (PMs), and electrical loading. The results show the competitiveness of the novel RA-FSPMG, in particular, in the output power and the required copper mass. Furthermore, the PM demagnetization possibility and the rotor axial pull force of the optimized RA-FSPMG are investigated, in detail. All discussions are supported by the 3D Finite Element Analysis (3D-FEA) and experimental results.

The electromagnetic vibration and noise in motors is mainly induced by electromagnetic forces and magnetostrictive force. The low-frequency force waves have a great influence on the deformation of the motor stator core due to resonance. In this paper, a 2-D electromagnetic-mechanical coupling transient model was built based on the quadratic magnetic domain rotation model, considering the magnetostrictive characteristics of silicon steel sheet and the magnetoelastic coupling of materials. Through numerical simulation calculation and analysis, it was found that low-frequency force waves appeared in the motor stator, and the large amplitudes happened on the single and twice power frequency. The actual experimental measurements were designed in the rotating motor and the transformer to verify this phenomenon. It is concluded that the rotating field or the magnetic path distortion leads to the large amplitude at single-power frequency or rotating field frequency on the electrical equipment.

Permanent magnet (PM) synchronous motors have become excellent alternatives for traditional induction and DC motors in numerous applications in recent years. Therefore, torque density and efficiency improvements in development of PM synchronous motors has become a significant issue. In this study, various PM synchronous motor alternatives are proposed with both non-oriented (NO) and grain-oriented (GO) silicon steel material in the same stator in order to increase the power density and the efficiency. Detailed performance comparison using 2D/3D FEA is completed and a feasible stator design is manufactured. The proposed design with GO material is also compared with a conventional PM motor with a NO stator steel. As a result of the investigations, it is observed that the proposed motor with GO material in the stator have higher torque density and efficiency as opposed to the conventional PM motor.

This paper employs grain-oriented (GO) silicon steel in an axial-flux permanent magnet (AFPM) machine to improve its torque and efficiency. Rolling direction of the GO material have been studied to ensure the machine’s main magnetic flux passes through the easy magnetization direction. Based on the study of the electromagnetic characteristics of AFPM machine, GO silicon steel is laminated to form a stator according to a certain lamination direction. The torque and efficiency of the proposed machine with GO material shows an increase in comparison with that of the conventional non-oriented (NO) silicon steel machine under identical conditions. In addition, an equivalent magnetic circuit model is established to illustrate little difference of electromagnetic property under no-load condition for the yokeless stator AFPM using two kinds of silicon steel sheet. Furthermore, a AFPM machine with stator yoke is also established to highlight the superiority of GO in the application of the AFPM machine with yokeless stator.

In this paper, the low reluctance superconducting direct drive linear generator (DDLG) for harvesting oceanic wave is presented. At first, a permanent magnet DDLG is designed in the ANSYS/Maxwell environment. The DDLG with both the copper and superconducting winding are characterized with finite element analysis. The DDLG is analyzed with the conventional and recently developed M5 Carlite magnetic cores. High graded neodymium iron boron permanent magnet, N46SH is selected for the DDLG to create strong magnetic field. It is analyzed that the proposed superconducting DDLG with M5 Carlite magnetic core and N46SH permanent magnet produces 294 kW more electrical power compared to that of the DDLG with copper conductor. It is also found that the stator size of the proposed DDLG is much smaller than the conventional one for designing the winding with superconducting tape.

This article provides an update to a paper presented in 2006, sharing the results of a decade of core repair. The process described is for a microconversion coreplate of electrical steel laminations used in ac stators, ac rotors, and dc armatures. The treatment process restores the coreplate and avoids the laborious restack process, saving time and reducing the cost to the end user.

The refining of plant fibre, particularly wood fibre, in a disc refiner involves changes in its geometric parameters and fraction proportions in the general semi-finished material mass. Fibre disintegration nature and intensity largely depend on the loads and forces occurring at the intersection of the rotor disc knives and the refiner stator. This research presents data confirming the possibility of regulating both normal and tangential forces by modifying the discs operational part design. It assesses the efficiency of the developed disc design compared to the traditional design used in fibreboard production. The redistribution of knives on the disc surfaces reduced the knife crossing angle (to ≈0–15°) and the number of (contacts) points formed from their intersection (to ≈528 pcs.), thereby increasing the main process parameters of the refining process (length of cut per second, cyclic elementary length, working refining surface) and the share of the normal components of the applied force (to ≈75%). An experimental study of mixed softwood fibre refining was carried out; the dependencies and optimal process conditions for regulating the gap (0.08–0.1 mm) between the refiner discs and the pulp concentration (2.5–3%) were determined taking the fibre properties into account. The new refiner disc design ensures a more intense fibre diameter reduction compared to the length. As a result, the longer and thinner, and therefore more flexible, fibres prevail in the wood pulp (to 50%), ensuring better inter-fibre interaction and improving the strength properties of the finished products (for 20–25%) without the use of binding resins.

This article proposes the core loss reduction of a surface-mounted permanent magnet motor with a segmented stator core. First, it is shown that the core loss of a motor is decreased by the segmentation of a stator core made of a nonoriented electrical steel sheet. The nonoriented electrical steel sheet used as the segmented stator core has an anisotropy, which is easy to magnetize in the rolling direction. Therefore, it is important to investigate the core loss of the segmented stator core in consideration of the rolling direction of the electrical steel sheet. The rolling direction of the steel sheet can be taken into consideration in magnetic field analysis by using the Enokizono & Soda (E&S) model, which is one of the vector magnetic property utilization techniques. Accordingly, the finite-element method, which introduced the E&S model, is used to evaluate the core loss of the motor. Second, the core loss of the segmented stator core is further reduced by applying a corner radius to each tooth root. Finally, the relation between the core loss and the rolling direction in the segmented stator core applying corner radius is investigated.

The process of making a weld using the heat-resistant EP693 alloy (Ni–Cr–W–Co–Co–Mo system) to make assemblies and components for gas-turbine engines (GTEs) is considered based on laser welding using a TruLaser Cell 7020 CO2 installation operating in the pulse-periodic radiation mode. EP367 (Ni–Mo–Cr–Mn) additive wire is used to obtain the weld. The effect of thermal treating is studied to estimate the change in structure and properties both in the weld-adjacent area and in the weld. The results are used to examine the structure of the weld and its breaks. The physics and mechanical properties of the weld are evaluated. The greatest durability limit is estimated for welds at a level of 2 × 106 cycles. The feasibility of using a laser-welding heat-resistant dispersion hardened nickel alloy is evaluated to make support and stator shells for GTEs. It is established that complex thermal treatment (quenching and aging) provides for the optimum values of strength at room temperature and at high temperatures. It is also responsible for the short-term strength of welds. According to the strength calculations made for the support and stator of GTE shells and experimental data, the strength of welds made using pulse-periodic laser welding results in a strength safety factor between 1.35 and 3. This technology is proposed for industrial application to make shell parts and assemblies to be used in GTE support and stator in order to improve the quality of welds with a reducing time of high-temperature heating to bring down power consumption.

This article presents a novel surface-mounted permanent magnet motor (SPMM) with hybrid NdFeB-Alnico magnets to achieve low cost and low torque pulsation. Based on the analysis of the effects of stator magnetomotive force (MMF) on rotor magnets, the Alnico magnets can be properly configured to avoid demagnetization. To reduce torque pulsation, three models with different slot-pole combinations are proposed and compared, with the aid of the finite element method (FEM), and the results show that the torque pulsation of the 27-slot/4-pole model is the lowest, which is selected for further optimization. The multi-objective genetic algorithm (MOGA) is adopted to optimize the usage of Alnico and NdFeB magnets, thereby improving torque performance and reducing the cost. To verify the effectiveness of the optimization, the optimized model with hybrid NdFeB-Alnico magnets is compared with other models with only NdFeB magnets under the same operating conditions. As a result, it shows that the optimized model can significantly reduce the cost of magnets while maintaining excellent torque performance.

Received:11 november 2020; Accepted: 27 December 2020; Published online: 05 April 2021 Abstract: Drones are used in agriculture and external control, utilizing cameras, various sensors, and autonomous flight functions. However, it is difficult to fly for a long time because of flying with heavy equipment. Therefore, it is necessary to increase the flight time through lightening of the drone itself and efficient control of the BLDC motor. That is, it is necessary to improve the motor itself, which accounts for most of the energy consumption in drone flight. Stator fabrication of existing BLDC motors is done by winding copper wires through individual processes on the stator core through an automated process. However, in the case of an ultra-small BLDC motor, the stator core has a small size and is manufactured using a thin-diameter copper conductor, and thus has a lot of problems in the automation process. Therefore, in this paper, the multi-division coupling structure method of individual teeth of the stator was applied through a new type of BLDC motor stator design. That is, the cartridge type BLDC motor stator was applied to improve and reduce the BLDC motor stator method. Through this, the performance limit of the BLDC motor was improved by combining individual teeth with multiple cartridges. The cartridge type BLDC motor is manufactured by stacking several cartridges on each tooth. Therefore, various performances can be produced according to the connection state of the cartridges

The influence of permanent magnet materials on the electromagnetic performance of switched-flux permanent magnet (PM) machine having C-core stator assembly is investigated and compared. Both two-dimensional (2D) finite element analysis (FEA) and 3D-FEA are used in predicting the results. Presently, there has not been any study on the performance effect of using a wide range of different types of magnet on C-core switched-flux PM machine. Hence, there is a need for this latest investigation. The considered magnetic materials are: Alnico grade A500, Ferrite grade F5, Neodymium–Iron–Boron (NdFeB) grade N52, and Samarium–cobalt grade S24. The analysis shows that the best electromagnetic performance, including machine efficiency, would be obtained from a given electrical machine when it is equipped with NdFeB magnetic material due to its possession of the highest amount of magnetic remanence, coercive force, and energy product (BH)max. Consequently, the machine having ferrite magnetic material would produce the worst electromagnetic performance, although it is of the lowest cost.

In this study, the authors propose a fault detection algorithm used in an on-line magnetic monitoring system in the hydropower plant. The proposed algorithm is based on two magnetic measuring methods: measurement of (inner) flux within generator in air gap and measurement of stator leakage (outer) flux outside of the generator. The system has to ensure, in situ and real time, magnetic monitoring and fault detection of hydrogenerator. The monitoring system is also useful for modern maintenance approach such as a condition based maintenance without generators’ work interruption and better planned and preventive maintenance in the power plant. The proposed system successfully detects the presence of magnetic unbalance of hydrogenerator, occurring as a consequence of shorted turns in the windings of the rotor poles or air gap asymmetry. The presented measurement results are achieved in real exploitation conditions.

Gas turbines are widely used in the areas of air propulsion, electric power generation, ship propulsion, external driving units, and other industrial applications. Efficient coating and cooling methods are often essential for the gas turbine surfaces to further achieve higher turbine inlet temperature and output efficiency. The thermal barrier coating (TBC) is the type of multilayered coating applied on rotating and stationary surfaces of the gas turbine components to safeguard them against the attack of high stream thermal loads and pressure gradients of the hot mainstream flows. TBC can also assist in surface-modified film cooling of gas turbine components. In this paper, the thermal barrier coated surface-modified film cooling methods for gas turbine components, viz. leading edge, pressure side, suction side, end wall, flat surfaces of stator guide vane and rotor blade, were reviewed and discussed in detail. The surface-modified film cooling methods for gas turbine components are grouped into three broad categories based on their geometric appearance. Each group was reviewed in detail for geometric and flow parameters, measurement techniques, flow characteristics, and performance parameters. Further, this study provides an overview of geometric and flow parameters of the compound angled film hole. Finally, the areas required for future research on the application of surface-modified film cooling methods are recommended in this review.

Considering the cost and performance of the remanufactured motor, a motor remanufacturing method with a hybrid stator core structure was proposed, a prototype of the remanufacturing motor was made and the experiment was carried out. The modified magnetic circuit model of the hybrid stator motor was established by fitting the B–H curves of the two materials to consider the influence of the stator material. The errors for silicon steel and amorphous alloy were approximately 4.9 and 4.3%, respectively. The variation in no-load air-gap magnetic density along the axial direction was studied via simulation, and the air-gap flux density decreases gradually from the centre of silicon steel segment to the centre of amorphous alloy segment. A deflection occurs in the distribution of the air-gap magnetic field, which is in connection with the saturation degree of the materials. The method for calculating the air-gap magnetic density of the hybrid laminated stator from the magnetic density of the two materials was proposed. Compared with the stator composed of only one material, the calculation result obtained by the proposed method is in good agreement with the simulation result, with an error of

This paper proposes a multi-stage axial flux permanent magnet machine (MAFPMM) and the properties with different stator core materials are analyzed. The mentioned MAFPMM has three rotor-disks and two stator-disks. As a key part of the flux path, stator core of silicon steel sheet, soft magnetic composite (SMC) and amorphous magnetic metal (AMM) are studied by three dimensional (3-D) finite element method (FEM), respectively. The performances such as flux density distribution, no-load back-electromotive force (EMF), cogging torque, output torque, and core loss are analyzed. FEM results indicate that the three materials have almost equal influence on flux density distribution, no-load back-EMF, cogging torque, and output torque. But in terms of core loss, difference appears between silicon steel sheet, SMC and AMM. Considering the disadvantages in mechanical property of AMM and silicon steel sheet, a prototype is fabricated using SMC stator core. The FEM results are verified by the experimental results of the prototype.

In this article, a partitional stator flux-modulated memory machine (PS-FMMM) is proposed. Compared with a conventional variable-flux memory machine, it can significantly improve the torque density due to magnetic gear effect and PS, and can have good flux-regulating capability with AlNiCo magnets. First, the basic principle of the proposed PS-FMMM is introduced, and different combinations of stator poles and rotor poles are compared. Then, the torque-regulating characteristics of the proposed PS-FMMM under different magnetization levels of AlNiCo magnets are obtained. Finally, the pole-arc ratio of iron piece and parameters of AlNiCo magnets are optimized based on sensitivity analysis. Various finite-element analysis (FEA) simulation, optimization, and comparison studies of the proposed machine are performed. The results verified the effectiveness of the proposed structure.

In recent years long stator linear synchronous motors (LLSM) started to replace the typical rotating to linear converters like belts, chains, screw systems, pulleys, disks and so on. With LLSM a lot of drawbacks in the machine concepts and design can be prevented. For long tracks, reducing reactive power and individual control of numerous moveable units, the track is segmented in several fed stator units. Because of the LLSM construction an operation with a physical position encoder is not desirable. For that reason position observers should be used instead. In this paper a method to control the multiple segmented LLSM without position encoder is proposed. The special behaviour during entrance and exit of one moveable unit in an active stator segment is described and the control concept via a master slave relationship is proposed. Experimental results are presented to demonstrate the performance and feasibility of the proposed method.

In this paper, a low-speed and high-efficiency permanent magnet generator (LHPM generator) for micro hydro-electrical generation system was developed, and two different low-speed generators by using silicon steel and SPCC core (Common Cold Steel Plate) were fabricated and compared. The proposed LHPM generator can have high no-load electromotive force (EMF) and high efficiency at low speed by optimizing its parameters, and shows possibility to reduce its production cost by comparing the performance with different ferromagnetic materials of iron cores. Firstly, the principle of the low-speed and high-efficiency permanent magnet generating system was introduced, and the parameter design of the LHPM generator was proposed. Then the performance with different ferromagnetic materials of cores was analyzed. Finally, various Finite Element Analysis (FEA) simulation, optimization studies and experiments were performed. The cogging torque reduction method, effect of PM’s parameters, and the influence of different materials of cores were also investigated. Furthermore, as a tradeoff between the generator’s performance and the production cost, so-called hybrid core type generator, of which the rotor is made of SPCC core and the stator is made of silicon steel core was proposed. The simulation and experimental results demonstrate the effectiveness of the proposed structure.

The performance of traditional flux switching permanent magnet tubular machine (FSPMTM) are improved by using new material and structure in this paper. The existing silicon steel sheet making for all mover cores or part of stator cores are replaced by soft magnetic composite (SMC) cores, and the lamination direction of the silicon steel sheet in stator cores have be changed. The eddy current loss of the machine with hybrid cores will be reduced greatly as the magnetic flux will not pass through the silicon steel sheet vertically. In order to reduce the influence of end effect, the unequal stator width design method is proposed. With the new design, the symmetry of the permanent magnet flux linkage has been improved greatly and the cogging force caused by the end effect has been reduced. Both 2-D and 3-D finite element methods (FEM) are applied for the quantitative analysis.

A low-loss and lightweight core material, with applications in electrical machinery, is made of highly packed and insulated magnetic microwires (MWs). These MWs are aligned in such a way as to guide the flux in the rotor/stator, with the ultimate goal of increasing the efficiency and substantially reducing core losses. Commercial F e bal N i 29 C o 17 -based MWs with a 127 μm diameter and a 33 μm insulation coating are utilised. The magnetic measurements of the fabricated sample demonstrate the high permeability and low core loss in a wide range of frequencies. To prove the utility of this type of material, the authors used it in the rotor core of a prototype 25 W three-phase synchronous reluctance machine. The core is lighter and the losses are significantly lower than in conventional core materials under the same torque density.

Tight assembly of stator windings with no insulation paper damage is a manufacturing challenge. We evaluate different sets of parts according to the following parameters: magnet wire thickness, stator slot smoothness, length of the straight magnet wire after the slot end, and type and amount of insulation cap at the end of the slot. These parameters have discrete values with small differences between them. The damage criterion is the decrease of the insulation paper breakdown voltage after assembly/disassembly of parts, assembled in a small set of designed experiments. Parameter values, i.e., levels at individual experiments are set by an orthogonal experiment matrix. Repetition of each experiment provides statistical significance. Data analysis shows that the additive model alone is not sufficient due to the high correlation of the parameters’ influences. We extend the model to include interparameter influences, which we model by adding a virtual parameter. The extended additive model generates parameter values that do not degrade the insulation paper breakdown voltage within the manufacturing process. These values are verified by repetitions of the control experiment.

Design and development technologies concerning aerodynamic efficiency enhancement of blades and turbine stages are explained and discussed in this chapter. Losses in steam turbines are rearranged taking into account the essential unsteadiness of flow fields in steam turbine blading and stages. Current aerodynamic designs of steam turbines are explained, including necessary relationships with layout design and mechanical design. Two-dimensional blade profile design and analysis, three-dimensional stator and rotor blade, and stage design and analysis are explained and discussed. As one of current distinguishing trends, three-dimensional design optimizations of steam turbine blades and contoured end-walls including effects of leakages of stator hub and rotor blade tip and effects of multistage configurations are explained. As a topic of future trends, an example of fluid structural interaction analyses is explained and discussed.

Acceptance tests on large fans to prove the performance (efficiency and total pressure rise) to the customer are expensive and sometimes even impossible to perform. Hence there is a need for the manufacturer to reliably predict the performance of fans from measurements on down-scaled test fans. The commonly used scale-up formulas give satisfactorily results only near the design point, where inertia losses are small in comparison to frictional losses. At part- and overload the inertia losses are dominant and the scale-up formulas used so far fail. In 2013 Pelz and Stonjek introduced a new scaling method which fullfills the demands ( [1], [2]). This method considers the influence of surface roughness and geometric variations on the performance. It consists basically of two steps: Initially, the efficiency is scaled. Efficiency scaling is derived analytically from the definition of the total efficiency. With the total derivative it can be shown that the change of friction coefficient is inversely proportional to the change of efficiency of a fan. The second step is shifting the performance characteristic to a higher value of flow coefficient. It is the task of this work to improve the scaling method which was previously introduced by Pelz and Stonjek by treating the rotor/impeller and volute/stator separately. The validation of the improved scale-up method is performed with test data from two axial fans with a diameter of 1000 mm / 250 mm and three centrifugal fans with 2240 mm / 896 mm / 224 mm diameter. The predicted performance characteristics show a good agreement to test data. NOMENCLATURE

This paper describes loss analysis of induction motors fed by inverters by considering major and minor hysteresis loops of electrical steel sheets used for stator and rotor cores. First, simple and practical models for major and minor hysteresis loops are described. Next, the validities of the models are confirmed by core material experiments. Finally, finite element analysis with the proposed hysteresis models is applied to an induction motor fed by an inverter. The calculated motor characteristics is also compared with the experimental results. It is clarified that the components of additional core losses caused by inverters are considerably affected by the shape of the minor hysteresis loops.

Switched reluctance motors (SRMs) have several advantages: simplicity, robustness and low manufacturing cost, which is considered as one of the alternatives to permanent magnet motors in electric vehicle application. However, due to the doubly salient structure, its severe vibration and acoustic noise prevent its wide application in industries. Strain gauge is proposed as a possible sensor for the electromagnetic force, which is the dominant vibration source in SRMs. However, besides the stretching due to electromagnetic force, magnetostriction deformation is also detected in strain gauge signal during measurement. In this paper, the influence of magnetostriction on strain gauge output in SRMs is studied. Two iron materials, amorphous iron and high silicon steel, are employed to fabricate two test machines with identical designs. Strain gauges are attached to these machines to detect the strain on the stator teeth. Compared with the magnetostriction-ignored strain acquired from finite element analysis (FEA), the measured strain is found to be 8 times and 1.5 times higher in the amorphous iron and the high silicon steel, respectively. It is also found that the significant difference is caused by the magnetostriction based on the measured magnetostriction data of each material.

The electrical steel market is expected to witness considerable growth in the coming years due to increasing demand in the automotive industry. High-speed electric motors have become inevitable for electric vehicle applications (EV). Almost all laminated steels suffer from high iron loss when operated at high frequency. Soft magnetic composites (SMC) are an ideal candidate for high-speed motor designs with high efficiency and low iron losses. This paper compares the performance of the SMC and laminated steel-based design for a radial flux outer rotor permanent magnet synchronous machine (PMSM) and its impact on the core loss at higher frequencies. Also, this paper examines two different winding patterns (distributed and fractional) for the optimal field weakening operation.

This paper investigates the effect of stator laminations on the acoustic noise field around the interior permanent magnet synchronous motor. The procedure involves filling the design space of a 4 pole 12 slot interior permanent magnet synchronous motor with multiple motor samples that are partitioned into two sets: the first set represents electric motors with laminated stator cores, while the other set comprises electric motors with non-laminated stator cores. Then, the sound pressure levels for both sets of designs are studied using finite element simulations and statistical analysis to better understand the effect of modeling the electrical steel laminations from the acoustic noise perspective.

The race to achieving maximum efficiency and higher torque/power density in electrical machines has started long time ago and now is slowly pushing its limits. Choosing the right type of electrical machine for each application, using computer added design and optimization methods for dimensioning and building complex electric drive systems contributed to today’s performances in this field. Lately, the specialist’s attention turned to using revolutionary materials with outstanding proprieties, for electrical machines to reach higher goals; but this approach comes with additional production costs that some mass industries are not willing to pay. Instead, this paper comes with a new proposal for using grain-oriented electric steel, which is a commonly used silicon steel for electrical transformers, in fractional-slot concentrated-wound (FSCW) permanent magnet synchronous motors (PMSM), for performance improvement. Finite Element Analysis (FEA) is used for simulations and some preliminary conclusions are drawn.

Introduction.Three-phase inductors of a rotating magnetic field are used in grinders, separators and stirrers for the technological processing of bulk and liquid substances. This occurs in a cylindrical working chamber under the influence of ferromagnetic elements in the form of pieces of iron wire, which move together with the field.Problem.By analogy with three-phase induction motors, for the stator of inductors a concentric winding is adopted, which is a diametric single-layer winding. When moving from such motors to an inductor, its operating conditions have changed due to the significantly increased non-magnetic space inside the inductor compared to the motor clearances. The difference in the frontal parts of the phase windings has become essential for the electromagnetic parameters and the structure of the magnetic field in the inductor working chamber. Therefore, a loop shortened stator winding, which is symmetrical, can be considered as an alternative to a concentric diametric winding.Goal.The aim of the work is to compare the dimensional and electromagnetic parameters of a rotating magnetic field inductor in two versions of its three-phase winding: concentric single-layer diametrical and loop shortened two-layer.Methodology.Comparison of the windings is carried out through a detailed analysis of the geometrical parameters of their frontal parts, as well as through numerical-field calculations of the electromagnetic parameters of the inductor as a whole and the distribution of the magnetic field in its working chamber.Results.A significant difference in the geometrical parameters of the frontal parts of the two windings under inductor conditions was revealed. The loop version of the winding makes it possible to reduce the length of the winding conductor, its active resistance, as well as the reactance of its frontal dissipation. At the same time the asymmetry of the phase windings is excluded and an increase in the homogeneity of the magnetic field in the inductor working chamber is provided.Originality.The scientific novelty of the work lies in the development of a method of comparative analysis of the windings under the conditions of the rotating magnetic field inductor and in revealing the advantages of a loop shortened winding compared to the used concentric diametric winding.Practical value.The loop shortened stator winding recommended for the inductor will eliminate the asymmetry of its electromagnetic system. Thereby, the quality of its work in the technological processing of different substances is significantly increased due to ensuring the homogeneity of the magnetic field in the working chamber. At the same time, the copper conductor of the winding is still saved, and the efficiency of the inductor is also increased by reducing the power of electrical losses.

Specific details including selections of process materials, tooling/fixture setups, and a step-by-step procedure for scaling-up demonstrations of the newly developed potting process, namely vacuum-assisted axial injection potting (VaAIP) have been fully developed for the stator winding of high power density electric motors for the future electrified aircrafts. Various essential pre-trial subtasks identified for the full-scale demonstrations were carried out. To date, optimization of cure condition and thermal stability of the coating epoxy and determination of optimum application conditions and thermal stability of the high temperature encapsulant wax were completed successfully and other subtasks were under way. The efforts to enhance thermal conductivity of the selected potting compound by adding conductive nano fillers such as boron nitride nanosheets (BNNS) have also been advanced. Initially, selection of the best mixing method and procedures was attempted via extensive and systematic experimental design.

The paper deals with a high frequency model of inorganic coils used to build high temperature (HT∘) motor. The HT∘ wire has a nickel layer that protects the copper against oxidation and a thin inorganic coating, which has poor electrical and mechanical properties. Therefore, the coils must be designed with a special care for getting a good distribution of turn-to-turn voltage during the fast transients excited by the steep fronted voltages of the PWM inverter.A specific coil structure is proposed and a high frequency (HF) equivalent circuit able to compute the turn-to-turn voltages during transients. The voltage distribution between the coils of a stator phase is also detailed.

This paper proposes two hybrid asymmetric cascaded multilevel inverters for driving medium-voltage open-end winding motors. Each phase of the proposed systems consist of a three-level (3L) H-bridge cell and a nine-level (9L) H-bridge cell connected in series. An unequal dc-voltage ratio of 1:8 between cells is used, providing 19 phase voltage levels. The topologies of the 9L H-bridge cell are based on modular multilevel cascade converter (MMCC) with double-star chopper cells, while the 3L H-bridge cell is fed by a floating capacitor. Compared to conventional MMCC for open-end stator winding motor drives, the proposed inverters can produce more phase voltage levels. In addition, they require a smaller number of power semiconductor switches, drivers and capacitors. Simulations and experimental results are presented in order to demonstrate the performance and feasibility of the proposed topologies.

Two types of surface-mounted permanent magnet synchronous machines (PMSMs) with the same physical dimensions but different stator core materials are comparatively analyzed, prototyped, and tested in this paper. In order to quantify the magnetization and loss characteristics of the stacked amorphous metal (AM) stator core, an experiment is conducted under different supply frequencies. Based on the data, the no-load iron losses, harmonic losses generated by the inverter-induced non-sinusoidal current harmonics, and the $d$ -axis and $q$ -axis inductances of two types of motors are comparatively analyzed by the finite-element method under different conditions and verified by experiments carried out on the two types of PMSM prototypes. The results illustrate that the AM PMSM has a characteristic of extremely low no-load iron losses, relative to the conventional silicon steel PMSM.

This paper investigates the no-load iron loss, on-load loss, and thermal performance of a high-speed surface-mounted permanent-magnet synchronous machine with an amorphous metal stator core (AMSC) and a titanium alloy retaining sleeve by numerical methods. The electromagnetic properties of the AMSC are tested by an experimental platform. The distributions of no-load iron loss, rated-load loss, and the thermal behavior of the motor are investigated under converter supply conditions. Finally, the loss and thermal performances of the prototype are tested and compared with the corresponding simulation results to verify the accuracy of the calculation results and the superiority of the prototype.

The effect of tooth tips on the performance variations due to using grain-oriented electrical steel (GOES) stator laminations in permanent magnet fractional-slot modular machines is studied in this work. It is concluded that the electromagnetic performance is further improved using GOES in machines with tooth tips compared to machines without tooth tips. This is due to a higher increment on the flux density in the airgap. The acoustic behaviour variations due to using GOES are predicted by analysing several mechanical- and acoustic-related parameters. It is predicted that implementing GOES improves the acoustic behaviour in machines without tooth tips. Furthermore, the effects of GOES in machines with tooth tips are slightly improved compared to machines without tooth tips. However, in order to determine the real mechanical and acoustic behaviours, further analysis is needed.

This paper discusses the fault tolerance performance of two hybrid six-phase drive systems under single-phase open-circuit fault. The topologies are considered to be hybrid because each of the two three-phase groups of the six-phase machine is connected to a different type of converter. One group is connected to a two-level converter and the other group is connected to a dual converter in an open-end arrangement. A compensation strategy is discussed in order to keep the rated operation even after the occurrence of the fault. The six-phase machine mathematical model after the fault is presented and utilized to elaborate the compensation strategy. Simulation and experimental results show the validity of the discussed solutions. It is observed that the use of the degree of freedom represented by zero-sequence components makes stator currents assume lower amplitudes after a single-phase open-circuit fault than the case in which these components are not present. This fact brings the possibility of operation with rated torque/power after the fault or lower reduction in torque/power to meet the thermal windings requirements.

In this paper, comparisons between two permanent-magnet-free machines, namely a wound-field flux-switching machine (WFFSM) and a switched reluctance machine (SRM), are carried out. The topologies and operation principles of the WFFSM are illustrated first. Then, the effects of rotor skewing angle on static characteristics, e.g., open-circuit phase flux-linkage and back electromotive force due to field currents, electromagnetic torque, and torque ripple, have been investigated in depth by finite-element analysis (FEA). Consequently, the optimal rotor skewing angle is determined. After that, comparisons at the rated speed 1500 r/min and at the rated RMS current density of 5 A/mm2 among the 6-armature-slots/5-rotor-poles (6/5) straight- and skewed-WFFSMs, and two representative SRMs, namely conventional 12/8 SRM and the short-flux 12/10 SRM with the same stator outer diameter and stack length are conducted in terms of phase flux-linkage, inductance, and torque performance. The results indicate that for these two PM-free machines, at the rated speed and the rated RMS current density, the skewed-rotor WFFSM exhibits considerably larger torque capacity, much smaller torque ripple, stronger saturation withstand ability. In addition, the experiments of the skewed-WFFSM and the 12/8 SRM prototypes working at the mechanical character curve are conducted. The experimental results present that the power factor of the WFFSM is much higher and the efficiency is slightly lower than that of the 12/8 SRM.

The performance improvement of using grain-oriented electrical steels (GOES) in the stator of PM fractional-slot modular machines is analysed in this study. Several models using a finite element tool are examined and it is concluded the techniques used in the actual software are not accurate for simulating anisotropic behaviour. Consequently, a simplified yet accurate modelling technique is proposed to simulate the performance of this type of electrical machines equipped with GOES. The advantages as well as the drawbacks of using GOES on the electromagnetic performance are investigated for different pole/slot combinations. It is concluded that the use of GOES is beneficial from an electromagnetic point of view mainly due to an increase on the radial component of the airgap flux density.

3-phase induction motors are widely used in industrial applications such as pumps, blowers, compressors, conveyors, etc. In addition, single-phase motors also have domestic use. For this reason, the design of the induction motor is of great importance. During the design, according to the parameters given as input, there are many situations that are contradictory to each other in order to achieve the goal. For example, if high efficiency is required, the motor size and the price will increase, and if lower price is required, other performance characteristics should be ignored. In the practical design of an induction motor, the designer has to comply with a number of constraints because of the large number of input variables. For this reason manual calculation becomes a very long and difficult process. To overcome this tiresome process, it is necessary to create a computer aided program or simulation model to determine the induction motor design parameters. In induction motor design, many parameters directly affect motor performance. Therefore, the selection of these parameters is of great importance. The C0 coefficient, which takes place in the first steps of the design process, also has a great influence on the motor design. In this paper, a program for optimizing design of 3-phase induction motors written in MATLAB is presented. The structure of the program is modular and therefore can be modified for the various requirements of the induction motor design. C0 constant (output coefficient), one of the design parameters, also varies with some other parameters. The most important ones are the specific electrical loading coefficient (A1) and the specific magnetic loading coefficient (Bav), making dramatic effect on the output coefficient. The effect of the variation of the C0 constant on the performance of the induction motor was investigated in the study. Stator inner and outer diameter, stack length, stator and rotor slot parameters, equivalent circuit parameters, losses and efficiency was obtained according to the change of Bav and A1 values. The obtained results are given and interpreted in tables and graphs.

This work was supported in part by the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea, and in part by the BK21PLUS Program through the National Research Foundation of Korea within the Ministry of Education.

This paper presents a theoretical and experimental investigation into a dual rotor magnetically geared power split device for hybrid electric drivetrains. It is shown that the modulation of magnetic field, created by rotor permanent magnets, by an array of ferromagnetic pole pieces results in two dominant space harmonics in the airgap adjacent to the stator. Thus, special attention is given to the design of the stator and the selection of the winding configuration, and the effects of air gap space harmonics on performance of the device are discussed. A full-scale prototype for a mid-sized passenger vehicle is designed, built, and tested, and the operation as a power split device is demonstrated and it is shown that efficiencies in excess of 94% can be achieved. Furthermore, torsional vibration attenuation by the proposed device is discussed and experimentally demonstrated on a purpose-built test rig.

The torque production of variable flux reluctance machines (VFRMs) is explained by the “magnetic gearing effect” in recent research. Based on this theory, this paper concludes the general principles for feasible stator/rotor pole selection and corresponding winding configuration for VFRMs. The influence of stator/rotor pole combination on torque performance is comprehensively investigated not only in terms of average torque and torque ripple, but also in terms of each single torque component. It is found that the synchronous torque is proportional to the fundamental rotor radial permeance component and has the dominant contribution in average torque for all the VFRMs. The stator slot number and rotor pole number should be close to each other to achieve the highest output torque. Meanwhile, the 6-stator-slot/(6 i ± 2)-rotor-pole (6s/(6 i ± 2)r) and their multiples are large torque ripple origins for VFRMs due to the large reluctance torque ripple. Also, it is proved that a lower stator slot number is preferable choice to obtain higher torque/copper loss ratio, whereas a higher stator slot number is more suitable for large machine scale scenario. Finally, the analyses and conclusions are verified by finite element analysis on the 6-, 12-, 18-, and 24-stator-slot VFRMs and by experimental tests on a 6s/7r and 6s/8r VFRMs.

Hydroelectric power plants are the most widely used renewable energy sources all over the world. In these plants, many studies have been conducted in order to produce energy continuously and efficiently. Among these studies, predictive maintenance methods, efforts to increase power by improving cooling conditions, and improving efficiency by improving the turbine wheel. In this paper, soldering at the junctions of the stator windings in the central generators has been investigated. Traditional solder (Cu Zn) materials and silver alloy solders (Ag-Cu-Zn) have been investigated in terms of thermal and metallographic. Silver alloy soldering has been found to have lower electrical conductivity than conventional soldering. The winding temperatures measured on the generating generator show that silver alloy soldering is more efficient. Reducing the stator winding temperature in hydroelectric power plants allows more energy production and also reduces costs by preventing winding failures.

With the development of aviation electrification, higher demands for electrical machines are put forward in aircraft electric propulsion systems. The aircraft electric propulsion requirements and propulsion motor features are analyzed in this paper. Comparing with conventional PM machines, ironless stator axial flux permanent magnet (AFPM) machine topologies with Litz wire windings allow designs with higher compactness, lightness and efficiency, which are suitable for high-frequency and high-power density applications. Based on the motor requirements and constraints of aircraft electric propulsion systems, this paper investigates a high-power 1 MW multi-stack ironless stator AFPM machine, which is composed of four 250kW modular motors by stacking in axial. The design guidelines and special attentions are presented, in term of electromagnetic, thermal, and mechanical performance for the high-frequency coils and Halbach-array PM rotor. Finally, an ironless stator AFPM motor is manufactured, tested and evaluated with the consideration of cost and processing cycle. The results show that the output power is up to 53.8kW with 95% efficiency at 9000r/min at this stage. The proposed ironless stator AFPM machine with oil immersed forced cooling proves to be a favorable candidate for application in electric aircraft as propulsion motors.

This paper investigates the differences in the electromagnetic vibration and noise of an amorphous metal (AM) permanent magnet synchronous machines (PMSMs) and silicon steel (SS) PMSMs. The electromagnetic vibration and noise of an AM PMSM and an SS PMSM sharing the same structure and dimensions are calculated under different conditions: 1) only radial forces (RFs); 2) only magnetostriction (MS) effects; and 3) both RFs and MS effects, and the calculated results of the two machines are compared. The effects of Young's modulus parameters and the MS coefficients of stator cores on the electromagnetic vibration and noise are analyzed. The vibration and noise of the AM PMSM and SS PMSM prototypes are tested and compared with the corresponding calculated results to verify the accuracy of the calculated results.

This work proposes a Model design simulation and implementation of a novel engine of an Electric Hybrid Vehicle of Permanent Magnet Synchronous Motor (EHVPMSM) based on field oriented vector control. The experimental analysis was carried out using: automotive motor control MTRCKTSPS5604P, 3-Phase PMSM coded of a single Motor Control Kit with MPC5604P MCU and simulation with Simulink. Therefore, the direct torque control can be obtained by adjusting the magnitude and phase angle of the stator flux linkage to match the vector torque required by the load as fast as possible. This eradicates the stress of charging the vehicle battery. It automatically charges when it is connected to the main supply of the EHVPMSM. The electromagnetic torque can be increased from 0 Nm to 6.7 Nm in approximately 340 μs. The response of speed transient was from −2100 rpm to +2100 rpm in 100 ms of 6.7 Nm torque limit. This is a novel way of conserving the energy consumption in a vehicle, which conserves space and weight and minimizes cost as it is simply done with low-cost materials. In this research, a new mathematical model is proposed for the direct and quadrature axis of the current to control the speed mechanism for the engine. Computer simulation ensures experimental validation of the system with a percentage error of 4.5%. The methodology employed to control the system was with the use of various sensors and software controller, this can be easily implemented in industry and institutional laboratory of learning. Keywords: Permanent magnet machines, PID, EHVPMSM, Vector control, Hybrid vehicle

Metallic additive manufacturing, also known as 3D printing, is greatly improving for the last decade. This new technology brings a greater design freedom than classical manufacturing and allow the production of breakthrough architectures especially thanks to topological optimization. In many industrial applications, metallic additive manufacturing already showed its importance, as the mechanical properties of parts manufactured this way are comparable with conventional materials. This article purpose is to evaluate the maturity of metallic additive manufacturing in the field of electro mechanical conversion. To achieve this goal, a rotor of a synchronous reluctance machine has been printed with metallic additive manufacturing, specifically Selective Laser Melting (SLM) technology. For its interesting magnetic properties and low magnetic losses, the INVAR 36, i.e. the binary Fe-35%Ni alloy was used. The performances of this rotor are compared to the performances of a classical laminated rotor with the exact same dimensions, both driven by the same stator.

Accurate prediction of core losses plays an important role in the design and analysis of flux-switching permanent magnet (FSPM) machines, especially during high-speed and high-frequency operation. Firstly, based on the numerical method, a high-frequency core loss prediction method considering a DC-bias magnetization component and local hysteresis loops as well as the harmonic effect is proposed. Secondly, the magnetizing characteristics of the silicon steel sheet and, consequently, the core loss of the electrical steel used as the core lamination are measured. Then, the loss coefficient of each core loss component is obtained by the data fitting tool. Based on the proposed method, the stator and rotor core losses of a three-phase, 12-stator-slot, and 10-rotor-pole (12/10) FSPM machine with different soft iron materials and driving modes are calculated. Finally, the results of the numerical method are verified by conventional finite element analysis.