Slot Opening Research Articles

Thermal Power and the Structural Parameters of a Wind Turbine Permanent Magnet Eddy Current Heater

Permanent magnet eddy current heating as a new type of wind energy utilization method, which is energy-saving, is zero-emission, and involves no pollution and a high utilization of wind energy, has attracted more and more attention. This paper deals with the simulation and optimal design of a permanent magnet eddy current heater (PMECH) driven by wind. Solid steel, closed-slot, and open-slot PMECH are proposed, and corresponding 2D finite element method (FEM) models are established. Using the skin depth concept, numerical analyses are conducted on the influence of the number, size, and position of copper strips on the thermal power of closed-slot and open-slot PMECHs, and the thermal power growth compared to solid steel PMECH. The results showed that there is an optimal value for stator wall thickness. When the air-gap length is 0.5 mm and the rotation speed is 200 and 1000 rpm, the optimal stator wall thickness is 16 and 9 mm, respectively. Compared to the influence of conductivity on thermal power, the influence of permeability is more significant. Compared with solid steel PMECH, both closed-slot and open-slot PMECH in a low-speed region can effectively improve thermal power, and the open slot has more obvious advantages. The maximum values of the thermal power growth (TPG) and thermal power growth rate (TPGR) of the closed-slot PMECH are 1.57 kW and 120.15%, respectively. The maximums of TPG and TPGR of the open-slot PMECH are 2.58 kW and 175.08%, respectively. The experimental results prove the validity of the analytical calculation.

Methods for the Viscous Loss Calculation and Thermal Analysis of Oil-Filled Motors: A Review

Oil-filled motors (OFMs) are widely used in deep-sea exploration and oil well extraction. During motor operation, the rotor stirs the oil in the air gap, causing viscous loss. Viscous loss affects the temperature distribution inside the motor. Accurately calculating the viscous loss and temperature rise in OFMs can provide a basis for optimizing the motor’s structural design. Motor structural parameters, including the rotor’s outer diameter, air gap, and slot opening, have a significant impact on viscous loss. The working conditions of OFMs, such as rotor speed and environmental temperature, also affect viscous loss. The viscosity of hydraulic oil is highly influenced by temperature, and changes in viscosity can lead to changes in viscous loss. These changes in viscous loss, in turn, alter the temperature distribution. Therefore, the coupling relationship between viscous loss and temperature must be considered. Additionally, when Taylor vortices occur in the fluid, the surface roughness of the rotor also has a significant influence on viscous loss. Currently, both domestic and international research on viscous loss and thermal analysis struggle to simultaneously consider the coupling of viscous loss and the temperature field, rotor surface roughness, and the effect of motor structure. This paper summarizes the methods used in recent years for studying viscous loss and thermal analysis, and puts forward some suggestions for future research on the coupling of the OFM temperature field and viscous loss.

Simulation and Design of Three 5G Antennas

In the context of 5G networks, this paper investigates microstrip array antennas and mobile terminal MIMO array antennas. It introduces two innovative designs and, based on these, develops and fabricates a mobile terminal antenna. The first of these designs, a 4 × 4 microstrip array antenna operating in the LTE band 42 (3.4–3.6 GHz), is researched and fabricated and an innovative approach, combining embedded and coaxial feeding methods, is proposed and employed. Measurement results indicate a bandwidth of 373 MHz (3.321–3.694 GHz), achieving a relative bandwidth of 10.7%. The antenna exhibits a high gain of 12.7 dBi, with an undistorted radiation pattern, demonstrating excellent directional characteristics. The second of these designs, a “loop-slot” MIMO antenna designed for 5G mobile devices with metal frames, is investigated. By opening slots in the metal frame and integrating them into the antenna’s feeding structure, the decoupling principle is analyzed from the perspective of characteristic mode theory. This design shares resonant modes between the loop and slot antennas, allowing for the overlapping placement of the two antenna units. Experimental results confirm an isolation level exceeding 21 dB, with significantly reduced dimensions. Finally, an eight-unit MIMO antenna is designed and fabricated for 5G mobile devices with metal frames. Continuous optimization of the “loop-slot” module layout and unit spacing leads to a compact and miniaturized antenna structure. Measurement results show an isolation level exceeding 17 dB, radiation efficiency ranging from 65.8% to 73.7%, and an envelope correlation coefficient (ECC) below 0.03. Finally, an analysis of specific absorption rate (SAR) demonstrates excellent MIMO performance in terms of human body radiation exposure.

Analytical prediction of the open‐circuit magnetic field for the V‐shaped interior PM machine by the improved subdomain method

AbstractThe open‐circuit magnetic field of the V‐shaped interior PM (IPM) machine is predicted by the analytical method. The method is implemented following the basic principle of the subdomain method. The machine model is divided into five different regions, including rotor slot, magnetic barrier, air gap, stator slot, and stator slot opening. To perform the analytical prediction process in the polar coordinate system, these regions should be transformed into the appropriate subdomains. The last four regions can be transformed into the subdomains with the required shape based on the existing method. The rotor slot cannot be treated as a single subdomain, for the shape of which is irregular. Herein, the PM and vacuum region in the rotor slot is divided into several fan‐shaped subdomains. The division method is described clearly. Then, the boundary conditions alongside the interface between adjacent subdomains are derived based on function transformation. On this basis, the open‐circuit magnetic field of the IPM machine can be predicted. The magnetic field of the 6p/36 s V‐shaped IPM machine is obtained by the proposed method, finite element method simulation, and experiment, respectively. Additionally, the comparison results verify the accuracy and efficiency of the proposed method.

Wear Mechanism of an AlCrN-Coated Solid Carbide Endmill Cutter and Machined Surface Quality under Eco-Friendly Settings during Open Slot Milling of Tempered JIS SKD11 Steel

In the die and mold industry, tempered JIS SKD11 steel is selected to manufacture cold-forming dies that require an optimum balance of toughness, strength, and wear resistance. Therefore, the machinability of tempered JIS SKD11 in the milling machining process is challenging. The use of eco-friendly machining settings is intended to diminish tool wear and enhance the quality of the machined surface as well as the accuracy of the machined components. Adapting to the aforementioned factors for cold-forming dies is a pivotal issue. In this study, the machinability of tempered JIS SKD11 steel was analyzed under dry, MQL, cryogenic cooling with liquid nitrogen (LN2), and liquid carbon dioxide (LCO2) machining settings during open slot milling operations with varying input parameters, including cutting speeds and cutting feeds. An in-depth evaluation of output responses, including tool wear, surface roughness, cutting temperature in the cutting zone, and microhardness of the machined surface, was also conducted. The findings unveiled that the flank wear of the cutters and surface roughness of the machined surfaces obtained minimum values of 0.22 mm and 0.197 µm, respectively, during open slot milling operations at a cutting speed of 100 m/min and a cutting feed of 204 mm/min under cryogenic cooling with liquid carbon dioxide (LCO2). The findings from this study suggest that employing cryogenic cooling with LCO2 could serve as a viable substitute for dry, MQL, and cryogenic cooling with LN2 methods to enhance the machinability of hardened JIS SKD11 steel.

Analytical Calculation of the No-Load Magnetic Field of a Hybrid Excitation Generator

Hybrid excitation generators combine the advantages of electric excitation motors and permanent magnet generators. Focusing on a permanent magnet generator as the object of study, an auxiliary excitation winding is introduced for voltage regulation. The main magnetic field is established by the permanent magnet, and the auxiliary excitation winding provides the magnetic potential required to regulate the air-gap magnetic field. While improving the voltage regulation performance of permanent magnet generators, it also reduces the loss of excitation windings in electrically excited generators. Based on a hybrid excitation generator with dual excitation windings, in the following article, we present a hybrid excitation generator equivalent to a full permanent magnet motor with the minimum output voltage, and an accurate subdomain model of the full permanent magnet motor is established considering the influence of slot opening. By establishing a matrix, the distribution curve of air-gap magnetic density was solved and ultimately verified using finite element analysis. The results of the present study lay a solid foundation for solving the air-gap magnetic density distribution of various parts of the hybrid excitation generator and studying its performance in the future.

Design and Analysis of Five-Phase Fault-Tolerant Vernier Permanent Magnet Machines for Direct-Drive Occasions

Abstract A fault-tolerant vernier permanent magnet machine (FTVPMM) with five phases for direct-drive occasions is designed and analyzed. The construction of the proposed FTVPMM is introduced and the principle of the vernier modulation effect is investigated. Parameters are designed and optimized by finite element analysis (FEA), including tooth width, slot opening, PM thickness, pole-arc coefficient, air-gap length, and rotor yoke. Furthermore, major electromagnetic performances are discussed, including cogging torque, no-load back electromotive force (BEMF), output torque, and fault-tolerant capability.

Numerical Analysis of Outer-Rotor Synchronous Motors for In-Wheel E-Bikes: Impact of Number of Windings, Slot, and Permanent Magnet Shapes

This study investigates the design an electric motor propelling hubless wheel mounted on an electric bicycle (e-bike) by numerical analysis. The motor is part of an in-wheel system that uses a permanent magnet synchronous motor (PMSM) to drive the hubless wheel. This paper presents an optimized PMSM design and compares various torque-related parameters, such as cogging torque, cogging torque total harmonic distortion (THD), and ripple torque. The comparison is based on a motor design that examines the effect of different factors, including the number of windings, slot openings, permanent magnet span, and magnet thickness. The motor was modeled and analyzed with variations in the number of windings (21, 23, 25), slot openings (2.4 mm, 3.0 mm, 3.6 mm), permanent magnet span (23 mm, 25 mm, 27 mm), and permanent magnet thickness (3.5 mm, 4.0 mm, 4.5 mm). Our findings suggest that increasing the permanent magnet’s thickness leads to a higher magnetic flux density. Additionally, when the permanent magnet span exceeds 25 mm, there is a sharp increase in cogging torque THD. Based on these results, a slot opening of 3.0 mm and the use of 25 windings are considered suitable for a hubless e-bike.

Effect of Parameter Modification on Torque Ripple in Interior Permanent Magnet Synchronous Motor

Electric motors are electromechanical machines commonly used in industry and automotive products. Interior Permanent Magnet Synchronous Motor (IPMSM) is a synchronous electric motor with a permanent magnet that is often used on electric vehicle engines. However, one of the characteristics of an electric motor with permanent magnet is the existence of torque ripples. The presence of torque ripples in electric motors can cause vibrations in the machine which affect efficiency, structural durability and operating speed. Therefore, it is necessary to make improvements or changes to the motor design to overcome this problem. This study was conducted to analyze the effect of a modification of the electric motor parameter on the torque value in the existing design. Modifications are applied to the existing design with an initial condition of torque ripples of 42.58%. This study modified the air gap, magnet angles, magnet thickness, and opening slot width. Modifications are carried out through a finite element method-based software simulation with the Taguchi method to reduce experimental configurations of design factors from 625 to 25 experiments. Through this research on parameter modification, the results of the analysis show that each modification of the design factor has an influence on the value of torque ripples. From the process of Analysis of Mean (ANOM), it can be seen that wider air gap and slot opening, the smaller torque ripples. Then, the greater magnet rib and thicker magnet cause the greater torque ripples.

Performance Analysis of Permanent Magnet BLDC Motor for Reducing Cogging Torque Using Taguchi Method

An electric motor is an electromagnetic machine commonly utilized across various industries and automotive products. One prevalent type of electric motor employed in electric vehicles is the Permanent Magnet Brushless DC Motor (PM-BLDC), a brushless motor employing permanent magnets. However, despite its efficiency, permanent magnet motors often experience vibrations that can disrupt their performance. This research aims to optimize the existing BLDC motor design, with a specific focus on reducing the existing cogging torque. Initially, the existing design exhibited a cogging torque level of 0.21482 Nm. The optimization process involved modifications to several key design parameters, such as air gap, magnet thickness, magnet type, and slot opening width. In previous research, only comparisons were made between stator slot designs, which proved to be less effective as significant differences were not evident in the results of the comparative analysis of BLDC motor designs. So, in this research, the Taguchi method was utilized for the optimization process due to several advantages it offers. Through an analysis of means and variance, the optimization process successfully achieved a significant reduction in cogging torque by 0.099744 and an increase in efficiency by 0.6%. The results of the optimized permanent magnet BLDC design indicated a cogging torque value of 0.115072 Nm and an efficiency of 86.64% at an operational motor speed of 1500 rpm. This research provides a substantial contribution to the development of more efficient electric motors suitable for various applications.

Efficient and Shape-Sensitive Manipulation of Nanoparticles by Quasi-Bound States in the Continuum Modes in All-Dielectric Metasurfaces.

Current optical tweezering techniques are actively employed in the manipulation of nanoparticles, e.g., biomedical cells. However, there is still huge room for improving the efficiency of manipulating multiple nanoparticles of the same composition but different shapes. In this study, we designed an array of high-index all-dielectric disk antennas, each with an asymmetric open slot for such applications. Compared with the plasmonic counterparts, this all-dielectric metasurface has no dissipation loss and, thus, circumvents the Joule heating problem of plasmonic antennas. Furthermore, the asymmetry-induced excitation of quasi-bound states in continuum (QBIC) mode with a low-power intensity (1 mW/µm2) incidence imposes an optical gradient force of -0.31 pN on 8 nm radius nanospheres, which is four orders of magnitude stronger than that provided by the Fano resonance in plasmonic antenna arrays, and three orders of magnitude stronger than that by the Mie resonance in the same metasurface without any slot, respectively. This asymmetry also leads to the generation of large optical moments. At the QBIC resonance wavelength, a value of 88.3 pN-nm will act on the nanorods to generate a rotational force along the direction within the disk surface but perpendicular to the slot. This will allow only nanospheres but prevent the nanorods from accurately entering into the slots, realizing effective sieving between the nanoparticles of the two shapes.

Is language change chiefly a social diffusion affair? The role of entrenchment in frequency increase and in the emergence of complex structural patterns

Complex systems research has chiefly investigated language change from a social dynamics perspective, with undeniable success. However, there is more to language change than social diffusion, i.e., a one-off adoption of an innovative variant by language users. Language use indeed factors in, besides prevalence (the percentage of adopters of the form in the community), lexical diversity (the number of different lexical items a conventionalized pattern combines with), and entrenchment (the average rate at which speakers choose the form in suitable pragmatic environments). Changes in token frequency may reflect changes in any of these three variables. To sort them out, we defined proxies to factor entrenchment out of empirical measures of prevalence and lexical diversity. From a French corpus, we analyzed 25 schematic constructions, featuring an open slot that hosts a variety of fillers. We show that their rise of token frequency across a change episode is mostly explained by entrenchment; however, the magnitude of the change is uniquely explained by the final extent of its lexical diversity. Furthermore, the fillers obey a construction-specific Zipf-Mandelbrot organization, that robustly holds throughout the change episode. We also show that in some cases, the fillers arise simultaneously, hinting at the possibility that such a complex organization emerges all at once, highlighting the role of structural features in language change.

A conical beam antenna array with filter characteristics for multi-rotor unmanned aerial vehicle measurement system

ABSTRACT This paper proposed a novel filter antenna with the conical beam, which consists of four magnetoelectric (ME) dipole antennas. By printing parasitic patches and etching open slots on the bottom of the substrate, two radiation nulls near the high frequency of the passband are introduced. Combined with the intrinsic radiation null of the ME-dipole antenna, the filtering response is obtained. In order to verify the design method, a prototype is manufactured and measured. The measurement results show that the impedance bandwidth (VSWR <2) of the antenna is 1.48 ~ 2.61 GHz (55.3%). In addition, the out-of-band suppression is more than 17.4 dB and the maximum radiation direction of the conical beam is stable around to Theta = 30°. The proposed antenna array can be promising candidates for multi-rotor unmanned aerial vehicle (UAV) measurement systems.

An Embedded Magnetic Encoder-Based Rotor Position Estimation for Switched Reluctance Machine

This paper investigates the possibility of applying embedded magnetic encoder (EME) consisting of three linear Hall sensors (LHS) for rotor position estimation in SRM. The key concept of this scheme is to detect the flux density characteristics (FDC) inside of stator slots. However, the armature field is to be detected in SRM, which is rather different from permanent magnet (PM) machines, where the PM field is detected. In this paper, FDC in stator armature slot openings are firstly analyzed between different winding configurations. Thus, a selection principle of winding configuration is proposed. Secondly, the proper installation location of LHS is investigated, where the sensitivity of FDC to location deviation is discussed. Accordingly, a sensor holder is specifically designed and manufactured to reduce location deviation. Thirdly, based on the detected FDC, a simplified multiple complex-coefficient filter (MCCF) is utilized as a filter to extract the positive sequence of the fundamental component of LHS output signal. As a result, the angular frequency and rotor position can be tracked by the synchronous reference frame-based phase-locked loop (SRF-PLL). Finally, the proposed method is verified by a series of experiments under steady- and transient-state conditions, which confirm the feasibility of EME scheme.

Investigation of Key Parameters on Cogging Torque in Permanent Magnet Machines Based on Dominant Harmonic Contents

The investigation of design parameters on the cogging torque has been a classical and common research subject over the last few decades. Nevertheless, an accurate analysis of major contributors to the cogging component is still difficult to find in past published works. This paper aims to address this knowledge gap by identifying the dominant harmonic contents responsible for the amplitude of cogging torque. As a result, a new factor is introduced to denote the level of cogging torque, rectifying the defect of the well-known existing factor called the goodness factor. The correlations between the key parameters (i.e., pole and slot numbers, pole arc to pole pitch ratio, and slot opening to slot pitch ratio) and the cogging torque are clarified by the proposed methodology. Finally, finite element (FE) and statistical results demonstrate the validity of the proposed results. It is expected that the key findings reported in this paper will serve as a valuable reference in the field of electric machines.

Structural analysis and optimization of gravity-driven membrane (GDM) for water treatment using computational fluid dynamics (CFD) with open slot implementation

Appropriate cleaning methods are essential to ensure the continuous use of membranes, however, research on the suitable cleaning methods for Gravity-driven membrane (GDMs) remains insufficient. To remove contaminants accumulated on the membrane surface of GDM modules, open slot and non-slot modules were designed and manufactured. These modules were compared for their filtration performance and contaminant removal efficiency through computational fluid dynamics simulations and filtration experiments using influent from wastewater treatment plants (WWTP). While the flow velocity in the housing of the open slot module is slower than that of the non-slot module, flow velocity of 0.17 m/s through the slot can effectively remove sludge accumulated near the beginning of the filtration area, thereby reducing the dead zone. Evaluation of the filtration performance of both modules using influent from WWTPs revealed that flushing effects occurred in both modules for the initial 100 L of filtration, but thereafter, flushing effects were observed only in the open slot module. Therefore, an introducing a slot structure can lead to significant cleaning effects compared to non-slot modules. Therefore, to maintain permeate flux continuously, it is deemed necessary to accompany an appropriate open-slot module for clean-in-place and chemical cleaning.

Designing an omnidirectional horizontally polarized circular patch antenna implementing unequal open‐circuited stubs

AbstractA novel method of designing an omnidirectional horizontally polarized (OHP) patch antenna with omnidirectionality in the H‐plane is proposed in this letter. The three pairs of unequal arch slots with three open radial slots are etched on the ground, which is equivalent to three pairs of open‐circuited unequal stubs that excite the TM1.5,1 patch mode and produce two resonance frequencies with circulating in‐phase current on the patch and the ground. Additionally, three pairs of open‐circuited unequal stubs are generated to enhance bandwidth and generate extra resonance frequencies by sequentially printing unequal arch and open radial slots on the top patch. The proposed antenna's 10 dB impedance bandwidth, including all resonance frequencies of TM1.5,1 patch mode, is 10.20%, covering the 2.326–2.576 GHz Wi‐Fi band. The patch and ground diameter are 0.31λ0 and 0.387λ0, respectively, with a real gain of 1.84–1.98 dBi over the operating band, and a gain variation is within 1.3 dB in the H‐plane at two measured resonance frequencies.

Advanced Parking System

The project entitled ADVANCED PARKING SYSTEM utilizes JavaScript and Python to reduce traffic congestion stemming from parking unavailability. The system identifies and displays the nearest vacant parking slot relative to a user's location. Efficient usage of parking real estate is achieved by continually tracking open spaces and allocating bookings. The core on-site module monitors parking occupancy through signals reflecting the availability status of individual spaces in real-time. This data feeds into a mobile application that allows drivers to check availability and reserve open slots. Together, the automated signaling of vacancies and user-friendly booking interface aim to create a reliable, rapid, and secure parking management ecosystem. By directing drivers to empty spaces, congestion arising from hunting for slots is greatly mitigated.

Investigating the Role of Stator Slot Indents in Minimizing Flooded Motor Fluid Damping Loss

This research examines how fluid damping loss affects the operation of a two-pole, 5.5 HP (4 kW) induction machine (IM) within the context of different slot opening configurations developed for downhole water pump applications. Since these motors operate with their cavities filled with fluid, the variations in fluid viscosity and density, compared to air, result in the occurrence of damping losses. Furthermore, this loss can be attributed to the motor’s stator and rotor surface geometry, as the liquid within the motor cavity moves unrestrictedly within the motor housing. This study involves the examination of the damping loss in a 24-slot IM under different stator slot indentations. The investigation utilizes computational fluid dynamics (CFD) finite element analysis (FEA) and is subsequently validated through experiments. The aim of this work is to emphasize the significance of fluid damping loss in submerged machines. Results reveal that the damping loss exceeds 8% of the motor output power when the stator surface has indentations, and it diminishes to 3.2% of the output power when a custom wedge structure is employed to eliminate these surface indentations.

Applicability evaluation of innovative simplified methods of slatted floor in pig houses – A CFD study

The slatted floor system is often used in pig housing. Computational Fluid Dynamics (CFD) is a valuable technique for determining the airflow and gas dispersion within the pit headspace through the slatted floor. However, there is a practical issue related to modeling the thousands of small slot openings in real livestock buildings for CFD simulation. It is unpractical to simulate the slatted floor with geometry details due to the large mesh number and the limited computer capacity. In this study, several methods to simplify the model of the slatted floor were explored to reduce the computational cost. The study was based on CFD analysis supported by experimental validation. The slatted floor was modeled in four ways: direct geometry method (DGM), porous-region method (POM), and profiled-porous-region method (including PPOM-cell (PPOM-C) and PPOM-floor (PPOM-F)). To assess the feasibility of the simplification, the four modeling approaches were compared with the experimental data. The results showed that it’s feasible to model the slatted floor as POM or PPOM. The accuracy of POM was high, but it was greatly affected by the calculation of the resistance coefficient. PPOM-C has greatly reduced the amount of calculation, which could be used to simplify the large-scale pig house model whose flow fields and gas emissions below the slatted floor could be ignored. The simulation result of PPOM-F was the closest to DGM, however, due to the large number of meshes and complex setup, it was not suitable for practical simulation.