Uniform Air Gap Research Articles

A Computer Modeling Characteristics of Brushless DC Motors in Medical Application

This work presents a modeling process for Brushless DC motors (BLDCMs) that considers both magnetic saturation and reluctance variation. DC motors are employed in diagnostic equipment like blood analysers and centrifuges. They enable the rotation and mixing of samples, facilitating the analysis of blood, urine, and other biological substances. Dental Tools: DC motors power dental equipment such as dental drills and handpieces. Two classes of Brushless DC motors were introduced for modeling using MATLAB simulation that involved reluctance variation: the non-uniform air gap model and the uniform air gap model. The characteristics of torque-speed for the two models are studied and compared. Non-uniform air gap mathematical model was subsequently adopted to study the effects of magnetic saturation. When magnetic saturation is incorporated in this work, some constant parameters in the models developed are transformed into variables that are dependent upon current variation.

Electric Motor Noise Variation Study Due to Air Gap Effect in Electric Vehicles

Motor whine is a crucial factor in the design of electric motors for electric vehicles (EVs). Predicting noise in a virtual environment is challenging due to the many possible variations during sample testing. The air gap between the stator and rotor in each sample is a significant contributor to radiated noise variation in the electric drive unit (DU). A baseline is first established for radiated noise prediction, assuming a nominal uniform airgap distribution, using the front electric DU in General Motors' Hummer EV. This study explains how the sensitivity of critical motor orders changes with static offset direction when the stiffness of DU is non-uniform and varies with radial direction. It also predicts the range of motor airborne noise variation due to offset orientation. Next, the effect of tilt direction on motor noise variation is studied at different torque conditions and motor speeds. Motor noise is found to be sensitive to tilt direction and angle as the DU stiffness changes axially. Additionally, rotor dynamic offset is investigated, which generates sideband orders in addition to motor pole pass orders. A comparison study is conducted to examine various sideband orders and their central frequency.

Studying the breakdown electric field in uniform and non-uniform air gaps

High voltage is essential in power grids, but it inevitably leads to high electrical stress and the associated risk of electrical discharges. Due to the complexity of the phenomena involved in electrical discharges, there are no analytical formulas for predicting the electric field strength at which they initiate, so experimental data and numerical methods are required for this purpose. According to many sources, electrical discharges can occur in air at normal pressure and temperature when the electric field strength is approximately 3 kV mm−1 or greater. This paper analyzes and discusses this threshold in detail by examining relevant electrode geometries used in high voltage applications from experimental data found in the scientific literature and using 2D finite element analysis simulations. Uniform, quasi-uniform, and non-uniform field gaps are analyzed to help students draw conclusions and gain insight into the nature of gas breakdown and the applicability of the 3 kV mm−1 threshold. The approach proposed in this paper is well suited for a practical session or group project for undergraduate or even graduate courses. Despite the important effects and design implications of electrical discharges on high voltage equipment, apparatus and systems, this topic is often not covered in sufficient detail in regular courses.

Analytical Modeling of Eddy Current Losses and Thermal Analysis of Non-Uniform-Air-Gap Combined-Pole Permanent Magnet Motors for Electric Vehicles

In order to solve the problem of large eddy current losses and high temperature rises caused by a large number of permanent magnets, a new type of combined-magnetic-pole permanent magnet motor is proposed in this paper. The sinusoidally distributed subdomain model of a non-uniform-air-gap rotor was established using the Laplace equation, and the analytical expression of eddy current losses in the rotor in a uniform air gap and non-uniform air gap was derived. The effect of the rotor’s eccentricity on eddy current losses was obtained. According to the characteristics of the distributed winding of the non-uniform-air-gap combined-pole permanent magnet motor, an equivalent treatment was performed to obtain the equivalent thermal conductivity value; to establish an equivalent thermal network model of the motor; determine the temperature of each component of the motor; and verify the correctness of the thermal network model through magnetothermal bidirectional coupling. Finally, an experimental platform was set up to carry out temperature rise experiments on the two prototypes. The experimental results show that a non-uniform-air-gap rotor structure can effectively reduce a rotor’s eddy current losses and motor temperature rise, as well as verify the accuracy of the analytical model’s calculation results.

Realization of a Three-Switch Leg/Phase Inverter for Nine-Phase Variable Pole– Phase Induction Machine With Phase Grouping Concepts

In this paper, a 3-switch leg/phase inverter topology is realized for 9-phase variable pole-phase induction motor (9Ph-VPIM) drives. The 3-switch legs (3SL) in the proposed inverter are controlled with two non-intersecting phase shifted references to achieve a 3-level voltage excitation for each phase winding. These two non-intersecting references per leg limit the possible modulation index (MI) and may require a higher DC link voltage. The split winding concept and the phase grouping solutions are used to enhance the MI. In the split winding concept, phase winding of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2n</i> pole machine is divided into <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> number of distinct windings and excited with the same voltage for attaining a uniform air gap flux. These coils are called cognate voltage coils (CVC). With these CVCs, different possible groupings are proposed to enhance the MI of a proposed 3SL/phase inverter. The symmetrical and efficient phase grouping solutions are analyzed and tested with an improved modulation index. Moreover, the proposed 9Ph-VPIM drive is controlled with carrier-based 3-φ SVPWM to further enhance the DC link voltage utilization. The proposed inverter will feed the effective phase by a 3-level voltage with suppressed harmonics resulting in a superior torque ripple. The proposed 3SL/phase inverter fed 5-hp 9Ph-VPIM drive is validated with the experimental prototype.

Design of a rotor with a starter-generator integrated into an aero car

The Halbach array structure rotor of the aero motor can satisfy the requirements of high power density and high air-gap flux for aeronautical motors. The size parameters of the rotor are determined by the power rating of the motor based on an analytic method. Producing a Halbach array structure is difficult. Comparison and analysis of the structure of the aero motor show that the overall structure of the rotor adopts a three-axial-section classic Halbach-array hollow structure, and the rotor magnetic steel adopts a discrete structure of 4 blocks per pole and a single 45 degrees magnetisation mode, which reduces the processing difficulty of the rotor magnetic steel. The finite element method was used to analyse the magnetic flux density distribution of the aeronautical motor under various working conditions. The results show that the motor can produce uniform air-gap flux density at various working conditions and present good sinusoidal periodicity. Furthermore, the axial segment did not produce obvious magnetic flux leakage. Finally, considering the eddy current loss of the stator under the rated power-generation condition with high-frequency magnetic field, we conducted coupling analysis of electromagnetic and heat flows to verify that the thermal characteristics of the rotor magnetic steel material could meet the requirements for the aero motor.

Near-superhydrophobic silicone microcapsule arrays encapsulating ionic liquid electrolytes for micro-power storage assuming use in seawater

Micro-energy storage, which is convenient for combination with energy harvesting, is known to be realized by microencapsulation with various shell materials, its application is limited to land. Here, we succeeded in fabricating a silicone microcapsule array encapsulating an ionic liquid electrolyte that can store minute power in NaCl solution as well as a minute power generation method. The ArF excimer laser-irradiated silicone rubber underneath silica microspheres was photochemically and periodically swelled by the photodissociation of silicone. Accompanied by the microswellings, the lower molecular weight silicones generated were ejected along a curvature of each the microsphere to enclose the microspheres. After the chemical etching, the silicone microcapsule arrays became hollow. Moreover, each the hollow silicone microcapsule could entrap an ionic liquid in a vacuum. In addition, the silicone microcapsules before and after the encapsulating ionic liquid showed a superhydrophobic or near-superhydrophobic property. As a result, the silicone microcapsule arrays could be confined in a uniform air gap of electrically insulated region in NaCl solution. This means that each the silicone microcapsule encapsulating ionic liquid as electrolytes enables to function as an electric double layer capacitor for micro-power storage, aiming to connect with Internet of Things devices that work under seawater.

Estimation of Surface Dose in the Presence of Unwanted Air Gaps under the Bolus in Postmastectomy Radiation Therapy: A Phantom Dosimetric Study.

The aim of this study is to design and fabricate a thorax phantom with irregularly shaped trapezoidal slots across the left side of the chest wall, allowing for the creation of unwanted air gaps under the bolus. Surface dose (Dsurf) measurements were made with Gaf Chromic EBT3 films at air gaps (0.0, 5.0, 10.0 and 15.0 mm) under gel bolus of thickness (5.0 mm & 10.0 mm), for 3DCRT technique (2 and 3 field) with clinical 6 MV photon beam under uniform and non-uniform air gap condition. The obtained values were compared with TPS estimated ones. In the presence of 15.0 mm uniform air gap, the mean estimated and measured Dsurf values with two and three field techniques decreased by 14.0 % to 15.2% and 14.7% to 17.4% under 5.0 mm and 10.0 mm bolus applications respectively. In presence of non-uniform air gap condition, the effect on Dsurf was minimal (3 to 3.5%) compared with the uniform air gap condition. Based on the study's findings, it is recommended that when using bolus in clinical radiotherapy applications, special care be taken to avoid unwanted air gaps under the bolus in order to achieve a uniform surface dose across the treatment region, where a customized 3D printed bolus may be a better option.

Electrical Utilizations of Air Gap Region Formed on Superhydrophobic Silicone Rubber in NaCl Aqueous Solution

A uniform air gap was successfully formed on a superhydrophobic silicone rubber in water or NaCl aqueous solution. The main chain of Si–O bonds of a silicone rubber was photodissociated by a 193 nm ArF excimer laser to lower the molecular weight only in the laser-irradiated microareas; due to the volume expansion, the microswelling structure was periodically fabricated on a silicone rubber, showing the superhydrophobic property. A pair of metal needles were inserted in the air gap formed on the superhydrophobic silicone rubber in a NaCl aqueous solution; an electrical insulation between two metal needles in the air gap was demonstrated. Additionally, a droplet of NaCl aqueous solution was confined in the air gap, after which the pair of metal needles contacted with the droplet through the air gap. As a result, an electrolysis of the droplet of NaCl aqueous solution occurred to produce hydrogen gas on the cathode in the air gap. Moreover, when Al and Cu wires were provided across the air gap and NaCl aqueous solution on the superhydrophobic silicone rubber, approximately 0.8–0.9 V of electric voltage was successfully generated between the two wires in the air gap based on the difference in electrochemical potential as an energy harvesting device in the sea.

Magnetic Field Analysis of an Inner-Mounted Permanent Magnet Synchronous Motor for New Energy Vehicles

The motor is an important component that affects the output performance of new energy vehicles (using new energy sources such as electric energy and hydrogen fuel energy to drive the motor and provide kinetic energy). Motors with high power and low noise can effectively improve the dynamic performance, passability and smoothness of new energy vehicles and bring a comfortable experience to driver and passengers. The magnetic field analytical model of the inner-mounted permanent magnet synchronous motor (IPMSM) is studied to improve its output quality. The motor is divided into four subdomains: the stator slot subdomain, the stator slot notch subdomain, the air-gap subdomain, and the permanent magnet (PM) subdomain. The general solution of the vector magnetic potential of each subdomain is solved, and the expression of magnetic flux density of each subdomain is derived. Meanwhile, the analytical model of the non-uniform air gap is established according to the uniform air-gap model. The model’s accuracy is verified by finite element analysis and prototype tests. The results show that the calculation results of the analytical model are effective. The model can be applied to predict the no-load back electromotive force (EMF) and cogging torque of the motor under different main air gaps. It also provides an effective and fast analysis method for the design and optimization of IPMSM for new energy vehicles.

Influence of Variable Air Gap on the Electromagnetic Performances of Permanent Magnet Brushless DC Motor

Simulation models of permanent magnet brushless DC motor with cam rotors and two kinds of uniform air gap motor determined by two limit arcs of the cam rotor were established on the basis of JMAG software. These simulation models were used to determine the influence of regularly varying air gap, which is formed during the rotation of the two cam rotors of the hydraulic motor pumps integrated with a cam rotor vane pump and a permanent magnet brushless DC motor, on the electromagnetic performance of the motor. The electromagnetic performance of the three kinds of motors were simulated and compared under rated and variable loads, respectively. Finally, the cam rotor motor prototype was developed for experimental research. Results show that the starting time of cam rotor motor under rated load is 20% shorter, and its output torque ripple is 23% smaller than those of the uniform air gap motor determined by the minimum limit arc of the cam rotor. However, the air gap flux density curve of the cam rotor motor weakens obviously amongst the three motors. Under different loads, the efficiency of the cam rotor motor is the highest amongst the three motors, and its mechanical property is hard. The research results can lay a theoretical foundation for the development of cam rotor motor pumps.

Design of an asymmetric rotor pole for wound field synchronous machines

This study proposes a novel asymmetric rotor pole design for wound field synchronous machines (WFSMs), which can achieve high saliency ratio and also low torque ripple. The key point is the optimal design of the asymmetric rotor pole with the inverse-cosine-shaped (ICS) plus reverse 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonic shaping. The asymmetric rotor pole can help to improve the average output torque by enhancing the saliency ratio. The reverse 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonic shaping on the rotor pole surface is mainly used to reduce the torque ripple. To certify the effectivity of the proposed design, three-phase 54-slot / 6-pole 4.7kW WFSMs with uniform air gap and with non-uniform air gap shaped by the ICS plus optimum reverse 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonic are utilized as the basic model and referenced model for comparison. For the referenced model, the optimum amplitude of reverse 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonic is preferred as 1/6. Finally, all electromagnetic characteristics of the investigated machines are predicted by the finite-element method (FEM). The highest saliency ratio and comparatively low torque ripple have been verified.

Statics and Dynamics of V-Shaped Microbeams Under Axial Forces

Abstract This work proposes an examination into the static and dynamic behaviors of in-plane V-shaped microbeam under both electric forces and axial loads. The microbeams are actuated with two separate electrodes of uniform air gap across their length. The effects of the initial rise and DC bias voltage are examined while varying the axial loads ranging from compressive to tensile. The numerical analysis is based on a nonlinear equation of motion of a shallow V-shaped microbeam. The static and eigenvalue problem were solved using a modal expansion based reduced-order modeling for numerous equilibrium positions. The analytical model is validated by comparing to an experimental case study. The results show rich and diverse static and dynamic behavior. It is shown that the microbeam may exhibit only the pull-in or snap-through and pull-in instabilities. Various multistate and hysterics behaviors are demonstrated when varying the actuation forces and the initial rise. High tunability is demonstrated when varying the axial and DC loads for the first two symmetric vibration modes. With various axial load and DC actuation options and different geometrical configurations, this particular V-shaped microbeam shows a capacity of increasing the static deflection range before pull-in, allowing more variation of its fundamental natural frequency. Therefore, it could be more promising for the realization of different wide-range tunable microresonator as compared to the regular straight and even bell-shaped microbeams. These results are very useful in microscale applications that can be benefit for designing some structures with low power consumption, high sensitivity, and wide tuning range. Such rich behavior can be very useful for high-performance microscale applications designs.

A Dynamic Model for Six-Degree-of-Freedom Bearingless Linear Motor Systems

This article develops a dynamic model for six-degree-of-freedom bearingless linear motor systems by means of lumped-element modeling. A four-sided motor system, containing eight three-phase motor units fed by their own inverters, is considered as an example system, but the modeling approach can be applied to other motor systems as well. The mechanical subsystem of the model comprises the rigid-body dynamics. The electromagnetic subsystem governs the electrical dynamics of the motor units and the production of the resultant electromagnetic force and its associated torque. In order to model the unbalanced magnetic torque due to tilting of the mover, the motor units are spatially discretized into a number of identical submotor models having a uniform air gap. The submotor models of each motor unit are electrically connected in series, i.e., they share the same current, but their flux linkages and forces differ in tilted positions. The electromagnetic subsystem can be parameterized based on simple static two-dimensional finite-element method computations at a range of uniform air-gap and current values. The developed model is validated through a comparison between the time-domain simulation results and the experimental results. The model can be applied to time-domain simulations, real-time control system development, and various analyses of the system.

Static and dynamic actuations of clamped-clamped V-shaped micro-resonators under electrostatic forces

This work presents detailed static and dynamic analysis of electrostatically actuated in-plane micro-electro-mechanical V-shaped micro-beam resonators. An analytical model is presented, based on the Euler Bernoulli beam theory, which accounts for the nonlinear electrostatic forces and the mid-plane stretching. The model is utilized to simulate the static and eigenvalue problems of the beam under various DC actuation scenarios. The model is validated by comparing with a finite element model and with experimental data. The experiments are based on in-plane silicon devices. The micro-beams are sandwiched between four electrodes (four ports) with uniform airgap for various electrostatic actuation options. These electrodes not only offer various electrostatic actuation options, but also allow the detection of the three lowest symmetric and anti-symmetric resonance frequencies. Results are presented for several case studies of micro-beams resonators of various geometrical parameters and airgap dimensions. With various actuation options and different V-shaped configurations, the structure may show only pull-in instability, the snap-through buckling, or both instabilities together. The results enable careful characterization of the snap-through buckling with the ability of increasing the static deflection range before pull-in. Also, the results can be promising for the realization of different wide–range tunable micro-resonator and for various vibration modes. These results can be useful in micro-scale applications that can be beneficial for designing structures with low power consumption, high sensitivity, and wide tuning range.

Study on longitudinal vibrations in turbomachinery coupled with skewed slotted bar cage induction motors

The present paper discusses the study of longitudinal vibrations in turbomachines coupled with skewed slotted bar cage induction motors and which are of the typical configurations in refinery industries. Based on vibration data, the severe longitudinal vibrations in tilting pad thrust bearing assembly and its failure mechanism during start up transient and steady-state operations has been observed. The excitation sources for these longitudinal vibrations originates from asymmetric air gaps in cage induction motors. Hereby, the study of longitudinal vibrations in turbomachines with thrust bearing is found to be necessary. A simplified Single degree freedom (SDOF) analytical model is proposed to estimate the peak response based on tuned variable stiffness method. Uniform air gap with rotor skew causes fixed thrust and is proportion to square of the load current. Static eccentricity across the rotor motor air gap causes variations in gap length and intern creates the torque fluctuations. This value is proportional to variance in square of the load current. In the proposed model evaluates the cascade effect of preloaded thrust due to rotor motor skewness and followed by compressor thrust due to differential pressure across the impeller in the form of the variable stiffness. This model has advantage in analysing the coupled motor and turbomachinery system response in longitudinal direction in a simple manner. The longitudinal vibrations estimate at thrust bearing and compared with experimental vibration data obtained from the field machinery. There is a good convergence between results of the analytical model and experimental field vibration data.

Расчет эквивалентных контуров демпферной обмотки и индуктивности взаимоиндукции синхронной машины

Formulas for calculating the leakage inductances and resistances of the equivalent damper winding of a salient-pole synchronous machine are proposed. The proposed formulas are based on the equality of the leakage field and thermal loss energies in a real winding and in its virtual image. Based on the equality of the MMFs of the real and equivalent damper windings, calculations for determining the number of turns in the equivalent damper winding are carried out. A 2D mathematical model of a synchronous machine with a uniform air gap is analyzed using complex periodic potential functions. It is shown that the reciprocity principle is not fulfilled in the mutual inductances of the stator winding phases and rotor windings due to difference in the MMF shapes of these windings. This principle is fulfilled for the mutual inductances between the stator winding phases and damper winding circuits.

3D heat transfer modeling and parametric study of a human body wearing thermal protective clothing exposed to flash fire

SummaryUnderstanding the heat transfer mechanism through a clothed man system in extreme environments is of great significance for human thermal protection. Three‐dimensional heat transfer models were developed based on the computational fluid dynamics considering a real‐shape human body in this study. The influences of air gap width, clothing thickness, and emissivity on the heat transfer within a dressed manikin exposed to flash fire were investigated. Simulated results indicated that the heat transfer in the air space was more complicated on the garment level than the fabric, because of the varying relative positions between different body segments and the heat source, as well as the ventilation openings. Increasing the fabric thickness was an effective method to reduce the transferred energy, which could remarkably lower the skin temperature. Decreasing both of the surface and backside emissivity from 0.9 to 0.3 could increase the protective performance, where surface emissivity reduction was recommended since the decrease of clothing temperature could minimize the risks of fabric degradation. The purpose of assuming the uniform air gap was to perform the parametric study, which was unrealistic indeed. The model with real clothing shape will be developed and investigated in the near future.

Optimisation of Multistep Cavity Configuration to Extend Absorption Bandwidth of Micro Perforated Panel Absorber

Micro perforated panel (MPP) absorber is a new form of acoustic absorbing material in comparison with porous ones. These absorbers are considered as next generation ones and the best alternative for traditional porous materials like foams. MPP combined with a uniform air gap constructs an absorber which has high absorption but in a narrow bandwidth of frequency. This characteristic makes MPPAs insufficient for practical purposes in comparison with porous materials. In this study instead of using a uniform air gap behind the MPP, the cavity is divided into several partitions with different depth arrangement which have parallel faces. This method improves the absorption bandwidth to reach the looked for goal. To achieve theoretical absorption of this absorber, equivalent electro-acoustic circuit and Maa’s theory (Maa, 1998) are employed. Maa suggested formulas to calculate MPP’s impedance which show good match with experimental results carried out in previous studies. Electro-acoustic analogy is used to combine MPP’s impedance with acoustic impedances of complex partitioned cavity. To verify the theoretical analyses, constructed samples are experimentally tested via impedance tube. To establish the test, a multi-depth setup facing a MPP is inserted into impedance tube and the absorption coefficient is examined in the 63–1600 Hz frequency range. Theoretical results show good agreement compared to measured data, by which a conclusion can be made that partitioning the cavity behind MPP into different depths will improve absorption bandwidth and the electro-acoustic analogy is an appropriate theoretical method for absorption enhancement research, although an optimisation process is needed to achieve best results to prove the capability of this absorber. The optimisation process provides maximum possible absorption in a desired frequency range for a specified cavity configuration by giving the proper cavity depths. In this article numerical optimisation has been done to find cavity depths for a unique MPP.

Parameter design and characteristic analysis of the interior non-uniform airgap permanent magnet synchronous motor for electric vehicle

Aiming at the demand for high torque and wide speed range of permanent magnet synchronous motor (PMSM) used in electric vehicles, a PMSM with fractional slot concentrated winding and the rotor of non-uniform airgap is designed. Fourier harmonic analysis theorem is used to calculate the harmonic content and peak value of cogging torque of different rotor eccentricities. Combined with finite element simulation software, the influence of rotor of uniform airgap and the rotor of non-uniform airgap on the q axis and d axis magnetic circuit is analysed respectively, so the optimal rotor eccentricity is determined. Compared to the rotor of uniform airgap, the peak value of cogging torque and the waveform distortion rate is reduced, while the salient rate is increased. Performance test is done and results show that reasonable rotor eccentricity can effectively improve the motor of flux weakening capability and widening the operation region of high efficiency.