Wide Air Gap Research Articles

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.

Atmospheric pressure uniform dielectric barrier discharge (DBD) in a wide air gap initiated from a narrow starting point

Generating a uniform non-equilibrium plasma in atmospheric pressure air has always been a challenge. It is believed that the maximum spacing for generating a uniform non-equilibrium plasma in atmospheric pressure air, whether using AC or nanosecond pulse drive, is 4 mm. Discharges are always non-uniform when the spacing is greater than 4 mm. In this paper, we propose a new type of dielectric barrier discharge structure to address this challenge. The left end of the structure rapidly increases the discharge spacing from 0.5 mm to 6 mm, while the right side of the main discharge gap maintains a uniform spacing of 6 mm. Nanosecond pulse voltage is used to drive the plasma, an ICCD camera is used to capture the image of the plasma during a discharge pulse cycle, which indicates that a uniform plasma within the 6 mm spacing of the main discharge gap is generated. Upon further reducing the ICCD camera’s exposure time to 20 ns, it is revealed that the uniform plasma is formed due to the rapid propagation of the plasma from left to right at a speed of order of 105 m s−1. Due to the small transverse component of the external electric field, this rapid propagation behavior cannot be due to the external electric field. Therefore, this paper further proposes the hypothesis of electric dipole formation leading to this fast propagation. The hypothesis suggests that the charge separation on the surface of the anode forms an electric dipole, which generates a local discharge at its right end. This local discharge further triggers the discharge in the main gap, and the main gap discharge, in turn, forms a dipole due to charge separation again, by repeating this cycle, the plasma propagates rapidly to the right. Further analysis demonstrates that this dipole can indeed produce a strong electric field of up to 41 kV cm−1 at its right end, which is sufficient to induce a local discharge. Moreover, under such a strong electric field, the electron migration rate can indeed reach 105 m s−1. These findings support the plausibility of this hypothesis.

An improved waveguide method for accurate complex permittivity measurement of medium/high-loss material

In this paper, we propose an improved method for accurately measuring medium/high-loss material permittivity to overcome the air gap problem in the conventional waveguide method. This method improves the sample fixture and has a high tolerance on the wide side air gap, which is a dominant factor affecting the accuracy of the conventional waveguide method. Meanwhile, the proposed method avoids the effects of tilting and displacement during sample assembly. In our study, a typical lossy material commonly used in vacuum tubes has been quantitatively analyzed in Ka-band. The simulation results show that the relative error of ϵr′ can be reduced from more than 10% to less than 1% compared with the conventional waveguide method with a 0.1 mm wide side tolerance. The relative error of tanδ can be reduced from over 20% to below 6%. In addition, different lossy materials are discussed. The accuracy improvement was verified by measuring different BeO-TiO2 samples using conventional and improved methods.

A Simple Calculation Method for Center Magnetic Flux Density of a Magnetic Core Electromagnet With a Wide Air Gap

Generally, electromagnet equipment such as an electric transformer is designed with the air gap as narrow as possible for assuming that the magnetic flux in the air gap does not spread. Therefore, it is possible to calculate the magnetic flux density in the air gap of the electromagnet using the magnetic circuit theorem. However, some equipment requires a wide air gap to use the spatial magnetic field. In this case, the magnetic circuit theorem cannot design the electromagnet because of the spread of magnetic flux in the air gap. Then, it becomes difficult to estimate the magnetic reluctance of the wide air gap. Therefore, it is difficult to formulate the center magnetic flux density in the wide air gap. In this work, the authors assume that the wide air gap of the electromagnet can be assembled by an infinite length solenoid with the reverse magnetomotive force finite length solenoid. In this model, the magnetic flux density in the wide air gap can be formulated using the magnetic circuit and the Biot–Savart law. The proposed model was tested in comparison to the experimental results of test electromagnets. The result shows that the proposed model can be used in the engineering design of electromagnets with a wide air gap.

Improving Combined Flow and Thermal Network Accuracy for Radially Air-Cooled Generators by Considering the Nonlinear Resistance Characteristics of T-Junction Flow

This work aims to improve the combined flow and thermal network (CFTN) accuracy for radially air-cooled generators by investigating the possible error stemming from the flow part. The nonlinear resistance characteristics of the T-junction dividing flow are first time considered for such cooling arrangement, which is achieved by employing the Gardel equations and the blend equation as the governing equations. Compared with the CFD model results as the benchmark, the nonlinear CFTN predicts an accurate flow rate in the radially extended airducts, making only 9% root mean square (rms) error for all the airducts. On the contrary, the linear CFTN fails to obtain a reliable flow distribution, as the rms error is as large as 34%. As a result, the nonlinear CFTN improves the accuracy of the maximum winding temperature by 6.4% over the linear CFTN and gives a more reasonable temperature gradient in the axial direction. Furthermore, the relative difference between the linear and nonlinear CFTNs is found to be even larger in the following conditions: large cooling air flow rate, wide airgap, low slot fill factor, and large airduct number. The proposed nonlinear CFTN modeling approach is also validated against experimental measurements for a prototype. The modeled temperatures match well with the measurements at different axial positions. According to the aforementioned findings, the nonlinear CFTN modeling approach is considered to be a reliable thermal analysis tool for the radial air-cooling arrangement.

A study on use of wobble features in laser welding of low alloy steel joint with butt joint configuration

Laser welding is modern digital welding process, which thanks to several advantages over traditional welding processes, is gaining ever growing role in manufacturing. The process has still some weaknesses. The better the beam quality the smaller the focal point, the actual welding tool, diameter is. Typically, because of this the welding of joints with lesser quality e.g. larger air gap is difficult or even impossible. So-called beam manipulation opens opportunities to deal with the problem. The dynamic beam manipulation gives opportunities to control the weld dimensions during the welding process by the requirements of individual locations of weld joint. This study used the two dimensional scanner to manipulate beam during welding with so called wobble function. Four different wobble configurations were tested in welding of low-alloyed steel with different joint qualities. The wobble typically made the welds wider, provided typically higher heat input and thus lowered the hardness of the joint. Wobble increased typically the root quality, but there are differences between different wobble parameters. It was possible to weld joints with wider air gaps in the selected material thickness, but the wider air gap and wobble caused finally, when wide enough the sagging of the joint.

Calculation Methods for the Self-inductance of Electromagnets with a Wide Air Gap

Calculation Methods for the Self-inductance of Electromagnets with a Wide Air Gap

Design, Development, and Experimental Results of a 30 000-R/Min One-Axis Actively Positioned Single-Drive Bearingless Motor

A novel structure design and experimental results of a one-axis actively positioned single-drive bearingless motor is proposed. This new single-drive bearingless motor is proposed by adapting the 4-pole 2-layer permanent magnet rotor and a wide air-gap length for high rotational speed operation. It is found that the rotational speed of 30 000 r/min is experimentally possible, although around 16 000 r/min top speeds were reported in the literature in only one-axis active magnetic suspension. In the machine design stage, it is shown that a wide gap length provides an efficiency improvement with a reduced risk of possible radial position touchdown.

Investigating the cooling of solar photovoltaic modules under the conditions of Riyadh

Cooling enhances the energy conversion efficiency and output of photovoltaic (PV) panels. In this work, the effects of natural convection, forced convection, and evaporative cooling on the performance of polycrystalline PV panels were investigated. The output and efficiency of a cooled PV panel were monitored and compared to those of an uncooled PV panel under the same conditions. The cooling was conducted using an insulated channel installed below a PV panel. Natural convection cooling was investigated for various channel air gaps (H = 30, 60, 90, and 120 mm). Natural convection currents in the cooling channels were capable of cooling the panel with wide air gaps. In forced convection cooling, the air was introduced by fans installed at the bottom opening of the cooling channel with various air velocities (ua = 1, 2, and 3 m/s). Evaporative natural convection cooling was performed by a wetted fabric along the lower surface of the cooling channel, whereas evaporative forced convection cooling by pushing air along the wetted lower surface of the channel. The experimental data showed that the panel efficiency and output increased due to cooling. The experimental results of natural convection cooling revealed that the use of an air gap of 120 mm to cool the solar panel contributed to an increase in the panel daily energy production and efficiency by 1.7% and 1.2%, respectively. For forced convection cooling, using air at a speed of 3 m/s increased the daily energy production by 4.4% and the efficiency by 4%. Natural convection evaporative cooling increased the daily energy production and the efficiency by 3.6% and 2.7%, respectively. Forced convection evaporative cooling contributed, at a speed of 2 m/s, to an increase in the daily energy production by 3.8% and an increase in efficiency of 3.8%.

A Wide Air Gap Flux Switching Bearingless Motor With Odd and Even Pole Pair Numbers

This paper introduces a bearingless motor topology with a magnet-free rotor that provides a higher rotor torque density and wider magnetic air gap compared to previously published topologies. The stray flux is minimized by using a stator with only eight teeth in temple configuration that contain permanent magnets. The motor performance is analyzed based on experimental prototypes, that were designed using 3D FEM simulations, for even and odd rotor pole pair numbers of six and nine, respectively. Control schemes that compensate parasitic radial forces to achieve stable magnetic levitation of the rotors are presented. The implemented prototypes reached a rotational speed of 2000 rpm and a maximum torque of 8 Nm.

Performance Benchmarking of a Novel Magnet-Free Bearingless Synchronous Reluctance Slice Motor

This paper presents a novel bearingless synchronous reluctance slice motor topology that contains no permanent magnets. The rotor with two iron poles and flux barriers is levitated and rotated through a stator winding system with six coils wired as two three-phase systems. A constant rotor-oriented magnetization current is applied to generate a magnetic bias flux. The system can be controlled similar to a bearingless permanent magnet synchronous slice motor and provides passive stabilization of axial and tilting movements of the rotor. The motor topology is discussed in detail and a prototype implementation is presented. Its performance with regard to passive properties, achievable torque, controllability, and wide air gap suitability is benchmarked against two other designs that contain permanent magnets either in the rotor or the stator. A loss analysis of all topologies is performed and suitable application areas are identified. The proposed design provides an interesting alternative to existing bearingless slice motor topologies in applications that require high rotational speeds, high process or ambient temperatures, or a disposable low-cost rotor with short exchange intervals.

Highly Flexible High-Efficiency Multiple-Resonant Wireless Power Transfer System Using a Controllable Inductor

Low- $Q$ resonant converter, such as series–series resonant converter, series resonant converter, and parallel resonant converter (PRC), are highly flexible and highly tolerant to coil misalignments. However, these kinds of topologies cannot be employed to the wide air-gap, low-coupling transformers because of their inadequate magnetizing inductance. On the other hand, high- $Q$ multiple-resonant converters such as series-PRC) and series-SPRC are very suitable for low-coupling compact wireless transformer applications. However, because these multiresonant topologies have several resonant pairs resonating at a single frequency, these parameter values ought to be consistent throughout the operating conditions to resonate at the same frequency. However, since the wireless power transfer (WPT) applications are required to be flexible and convenient to the customers, the wireless transformers are not supposed to be rigid and stationary. To solve the problem, a controllable inductor for a high- $Q$ multiresonant WPT system is proposed to extend the soft switching region and to keep the resonant circulating energy minimum even at resonant mismatch conditions caused by the misalignments or temperature variations of the wireless transformer coils. The performance enhancement of the multiple-resonant wireless converter is validated using the proposed controllable inductor technique, and also the feasibility of the proposed technique is proven under different mismatch conditions through 200-W hardware experimental results.

Batch-Fabricated α-Si Assisted Nanogap Tunneling Junctions.

This paper details the design, fabrication, and characterization of highly uniform batch-fabricated sidewall etched vertical nanogap tunneling junctions for bio-sensing applications. The device consists of two vertically stacked gold electrodes separated by a partially etched sacrificial spacer layer of sputtered α-Si and Atomic Layer Deposited (ALD) SiO2. A ~10 nm wide air-gap is formed along the sidewall by a controlled dry etch of the spacer. The thickness of the spacer layer can be tuned by adjusting the number of ALD cycles. The rigorous statistical characterization of the ultra-thin spacer films has also been performed. We fabricated nanogap electrodes under two design layouts with different overlap areas and spacer gaps, from ~4.0 nm to ~9.0 nm. Optical measurements reported an average non-uniformity of 0.46 nm (~8%) and 0.56 nm (~30%) in SiO2 and α-Si film thickness respectively. Direct tunneling and Fowler–Nordheim tunneling measurements were done and the barrier potential of the spacer stack was determined to be ~3.5 eV. I–V measurements showed a maximum resistance of 46 × 103 GΩ and the average dielectric breakdown field of the spacer stack was experimentally determined to be ~11 MV/cm.

Design of an Axial-Flux PM-Assisted Claw-Pole Generator Based on an Equivalent Magnetic Circuit Model

An axial-flux permanent-magnet (PM)-assisted claw-pole generator (APCG) is designed based on an equivalent magnetic circuit model (EMCM). It is designed for generating power in vehicle with the merits of high power density, no brush, and wide airgap flux density modulation range. This paper mainly focuses on establishing the EMCM of the APCG and designing a set of optimal structure parameters. First, the topology and operation principle of the APCG are introduced in detail, including material, fabrication, and magnetic flux distribution. Second, the magnetic circuits in claw poles are simplified and the relationships among the key parameters are discussed. Finally, based on the simplified model and the relationships among the key parameters, the EMCMs of current and PM excitation are established, respectively. According to the EMCM, a scheme of a 4 kW APCG is carried out. Comprehensive investigations demonstrate that the EMCM is time-saving and relatively accurate when compared with a finite element method.

Phase control of spin waves based on a magnetic defect in a one-dimensional magnonic crystal

Magnonic crystals are interesting for spin-wave based data processing. We investigate one-dimensional magnonic crystals (1D MCs) consisting of bistable Co20Fe60B20 nanostripes separated by 75 nm wide air gaps. By adjusting the magnetic history, we program a single stripe of opposed magnetization in an otherwise saturated 1D MC. Its influence on propagating spin waves is studied via broadband microwave spectroscopy. Depending on an in-plane bias magnetic field, we observe spin wave phase shifts of up to almost π and field-controlled attenuation attributed to the reversed nanostripe. Our findings are of importance for magnetologics, where the control of spin wave phases is essential.

Design and fabrication of hybrid SPP waveguides for ultrahigh-bandwidth low-penalty terabit-scale data transmission

Here we design and fabricate a hybrid surface plasmon polarities (SPP) waveguide on the silicon-on-insulator (SOI) photonics platform. The designed hybrid SPP waveguide is composed of a metal ridge, an air gap, and a silicon ridge. We simulate the mode characteristics in the structure and design the waveguide with a wide air gap that can simplify the fabrication process and maintain the advantages of the hybrid SPP mode. The performance of ultrahigh-bandwidth data transmission through the proposed waveguide is then investigated using 161 wavelength-division multiplexing (WDM) channels, each carrying a 11.2-Gbit/s orthogonal frequency-division multiplexing (OFDM) 16-ary quadrature amplitude modulation (16-QAM) signal. The bit-error rates (BERs) of all 161 channels are less than 1e-3. The favorable results show the prospect of on-chip optical interconnection using the proposed hybrid SPP waveguide.

Aperture slot size effect to wide band open air gap radial‐line slot array performance

ABSTRACTA wideband open air gap radial line slot array (RLSA) antenna is presented for point‐to‐point application. This article investigates the optimum slot arrangement and the effect of slot width to the RLSA antenna. Eight models were developed and simulated with slot width taking range in values from 1 to 8 mm. Results from simulation shows optimum performance at 6‐mm slot width. The 2‐mm slot width gave similar performance to the 6‐mm slot width in term of gain and directivity. Both antennas were fabricated and measured, from the measurement; a better return loss performance of about 28% was realized at 6‐mm slot width when compared to 2‐mm slot width RLSA. However, both antennas produced the same gain. A better sidelobe level of 2.9 dB was achieved with the 2‐mm slot width antenna. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2974–2978, 2014

Plasmonic waveguide ring resonators with 4 nm air gap and λ0(2)/15,000 mode-area fabricated using photolithography.

Plasmonic air-gap disk resonators with 3.5 μm diameter and a 4 nm thick, 40 nm wide air gap for a mode area of only λ0(2)/15,000 were fabricated using photolithography only. The resonant modes were clearly identified using tapered fiber coupling method at the resonant wavelengths of 1280-1620 nm. We also demonstrate the advantage of the air-gap structure by using the resonators as label-free biosensors with a sensitivity of 1.6 THz/nm.

601 高効率超ワイドギャップ磁気軸受に関する研究(OS6 オーガナイズドセッション《振動・音響・制御》)

In this study, a high efficiency ultra-wide gap active magnetic bearing is proposed. It has homopolar type rotors with a permanent magnet between them. The stators are composed of bias and control components. The bias components generate bias magnetic fluxes by the strong permanent magnets, while the control ones generate control fluxes by the electromagnets. The control fluxes don't act directly on the homopolar rotors, but can change the bias fluxes. The control forces are generated by the imbalance of the bias fluxes. Even though the wide air gap, it is feasible to reduce the energy consumption and maintain the high control performance.

Simulation of air gap formation in slab continuous casting mould

A coupled model for describing the air gap formation in a continuous casting mould was developed. In the model, the evolution of the shell and mould temperatures and the gap between them were predicted by a two-dimensional transient thermomechanical coupled finite element model, and the formation of the air gap was described by an interfacial heat transfer model. Based on these, the basic formation characteristics of the air gap in a slab mould during casting of peritectic steel and the influences of varying the casting conditions, such as casting speed, mould taper, molten steel superheat and mould flux solidification temperature on the air gap formation, were described. The results show that the air gap in the mould first forms in the shell corner and mainly concentrates in the regions of 0–20 mm and 0–10 mm from the wide and narrow face corners respectively under typical continuous casting conditions of peritectic steel. The air gap on the shell wide face grows continuously and increases in the low part of the mould, where it mainly forms in the range of 160–450 mm below the meniscus on the shell narrow face. Increasing casting speed reduces the air gap. Increasing mould taper promotes air gap formation on shell wide face but reduces it slightly on the narrow face. Higher steel pouring and mould flux solidifying temperatures result in a wider air gap formation on both the wide and narrow faces.