Analysis of electromagnetic torque for induction motors with a novel non-skewed rotor structure

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Amir Darjazini ◽  
Abolfazl Vahedi ◽  
Amin Nobahari ◽  
Saber Gharehseyed
Keyword(s):  
High Performance ◽  
Induction Motors ◽  
Acoustic Noise ◽  
Torque Ripple ◽  
Iron Loss ◽  
Mechanical Equipment ◽  
Electromagnetic Torque ◽  
Content Type ◽  
The Mean ◽  
Rotor Structure

Purpose Pulsating torques cause a number of problems in electrical machines, including mechanical vibrations, acoustic noise and the depreciation of mechanical equipment. In induction motors, the slot skewing method is an effective way to solve these issues; however, it has some drawbacks such as output torque drop, stray loss intensification due to inter-bar currents and iron loss increment. Besides, slot skewing may not be practical in higher-rated induction motors. In this regard, this paper introduces a modified non-skewed rotor (MNSR) structure as a possible alternative to the skewed designs. Design/methodology/approach The proposed structure includes a two-segmented rotor with an intermediate ring between the rotor parts that are mounted on the shaft with a relative shift angle. Detailed information about the idea and structure of the MNSR as well as its manufacturing aspects will be presented in the second section of the paper. First, the working principle of the proposed design is described via analytical equations to provide an insight into the concept. The shifting angle will then be calculated by analyzing the harmonic contents of the electromagnetic torque. Finally, the validity of the analytical method will be verified by developing three-dimensional finite element models. Findings It is demonstrated that by using the proposed rotor structure, the torque ripple has been reduced to a satisfactory level without significantly affecting the mean torque, unlike the skewing method. Furthermore, the new method could avoid the disadvantages of the skewing method while enhancing other motor characteristics such as iron loss. Also, the total volume of the MNSR is equal to the initial design, and the mass and material differences are also negligible. Originality/value In this paper, a MNSR is introduced as a possible alternative to the skewed patterns. The study mainly focused on electromagnetic torque profile characteristics, i.e. the mean torque enhancement and the ripple reduction. The MNSR structure can be used for general purposes and high-performance applications, especially where excellent torque characteristics are required.

Direct Torque Control for a Bearingless Induction Motor Based on Model prediction

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ding Wang ◽  
Zebin Yang ◽  
Xiaodong Sun ◽  
Weiming Sun ◽  
Haitao Mei
Keyword(s):  
Phase Angle ◽  
Direct Torque Control ◽  
Torque Ripple ◽  
Torque Control ◽  
Electromagnetic Torque ◽  
Flux Linkage ◽  
Content Type ◽  
Voltage Vector ◽  
Space Voltage Vector ◽  
Stator Flux

Purpose The purpose of this paper is to address the large stator flux linkage ripple and electromagnetic torque ripple caused by the hysteresis comparator in traditional direct torque control for a bearingless induction motor (BIM). Design/methodology/approach Model predictive direct torque control (MPDTC) strategy is adopted. On the basis of the mathematical model of BIM, the stator current and stator flux observational values are obtained, and the electromagnetic torque and stator flux at the next moment are predicted. Then, based on the relationship between the stator flux and the electromagnetic torque, the predicted stator flux can be transformed into an equivalent flux linkage vector, which eliminates the weighting coefficients problem among multiple variables in traditional objective functions. The objective function and torque PI controller will output the optimal stator flux linkage and the increments of the torque phase angle. Through the phase angle increments, the space voltage vector can be obtained by the reference flux linkage controller instead of the stator flux linkage and the torque hysteresis controller. Findings The proposed MPDTC method can effectively improve the stator flux linkage and the torque ripple. It can implement the stable suspension of the rotor and improve the dynamic performance and steady-state accuracy of the BIM system. Originality/value A MPDTC strategy is proposed to reduce the ripple of stator flux and electromagnetic torque. The phase angle increment angle of stator flux linkage and electromagnetic torque is optimized by model prediction, and the optimal space voltage vector is obtained by designing the reference flux controller.

scholarly journals Distribution of Linezolid in Tuberculosis Lesions in Patients with Spinal Multidrug-Resistant Tuberculosis

2020 ◽  
Vol 64 (7) ◽  
Author(s):  
Yuan Li ◽  
Weijie Dong ◽  
Tinglong Lan ◽  
Jun Fan ◽  
Shibing Qin ◽  
...  
Keyword(s):  
Bone Tissue ◽  
Granulation Tissue ◽  
High Performance ◽  
Multidrug Resistant ◽  
Sample Collection ◽  
Tissue Samples ◽  
Content Type ◽  
Mdr Tb ◽  
The Mean ◽  
The Difference

ABSTRACT Linezolid has strong antimicrobial activity against the multidrug-resistant (MDR) strains of Mycobacterium tuberculosis. Little is known about the distribution of linezolid in tuberculosis (TB) lesions in patients with MDR-TB. The aim of this study was to evaluate the distribution of linezolid in TB lesions in patients with spinal MDR-TB. Nine patients with spinal MDR-TB were enrolled prospectively from August 2019 to February 2020. The patients received a linezolid-containing anti-TB treatment regimen and needed surgery for the removal of TB lesions. During the operation, nine blood samples, eight diseased bone tissue samples, seven pus samples, and four granulation tissue samples were collected simultaneously and 2 h after the oral administration of 600 mg of linezolid. Linezolid concentrations in plasma, diseased bone tissue, pus, and granulation tissue samples were subjected to high-performance liquid chromatography-tandem mass spectrometry. At sample collection, the mean concentrations of linezolid in plasma, diseased bone tissue, pus, and granulation tissue samples of the nine patients were 11.14 ± 5.82, 5.94 ± 4.27, 11.09 ± 4.58, and 14.08 ± 10.61 mg/liter, respectively. The mean ratios of linezolid concentration in diseased bone/plasma, pus/plasma, and granulation/plasma were 53.84%, 91.69%, and 103.57%, respectively. The mean ratios of linezolid concentration in pus/plasma and granulation/plasma were higher than those in diseased bone/plasma, and the difference was statistically significant (t = −2.810, P = 0.015; t = −4.901, P = 0.001). In conclusion, linezolid had different concentration distributions in different types of TB-infected tissues in patients with spinal MDR-TB.

scholarly journals Performance Improvement of Concentrated-Flux Type IPM PMSM Motor with Flared-Shape Magnet Arrangement

2020 ◽  
Vol 10 (17) ◽  
pp. 6061
Author(s):  
Keun-Young Yoon ◽  
Soo-Whang Baek
Keyword(s):  
Permanent Magnet ◽  
Performance Improvement ◽  
High Efficiency ◽  
Acoustic Noise ◽  
Permanent Magnet Synchronous Motor ◽  
Torque Ripple ◽  
Proposed Model ◽  
Interior Permanent Magnet ◽  
Low Torque ◽  
Rotor Structure

This study demonstrates that the use of a flared-shape rotor structure in interior permanent magnet (IPM) permanent magnet synchronous motor (PMSM) yields better performance than the basic IPM PMSM motor, using a spoke structure with ferrite magnets. To concentrate the effective magnetic flux, the proposed rotor structure is composed of a number of ferrite magnets, which are inserted in a flared shape in the rotor core. This paper shows the comparison with the analysis results of 2D finite element method (FEM), and it is shown that the proposed IPM PMSM motor can be an effective substitute for the basic IPM PMSM motor, which requires low torque ripple and high efficiency. In particular, the proposed flared IPM PMSM motor has lower pulsation of torque and superior efficiency, as well as lower acoustic noise and vibration, compared to the basic IPM PMSM motor. To verify the performance improvement of the proposed model, a prototype of the proposed model was manufactured. It was experimentally confirmed that the proposed model has lower torque ripple and higher efficiency than the basic model. Based on this performance improvement, the proposed flared IPM PMSM motor is suitable for electric vehicles and home appliances.

Design techniques for cogging torque reduction in a fractional-slot PMBLDC motor

2020 ◽  
Vol 39 (5) ◽  
pp. 1041-1055
Author(s):  
Lidija Petkovska ◽  
Paul Lefley ◽  
Goga Vladimir Cvetkovski
Keyword(s):  
Torque Ripple ◽  
Simple Design ◽  
Electromagnetic Torque ◽  
Arc Length ◽  
Original Design ◽  
Cogging Torque ◽  
Content Type ◽  
Motor Design ◽  
Fractional Slot ◽  
Design Techniques

Purpose This paper presents the design techniques applied to a novel fractional-slot 6/4 pole permanent magnet brushless direct current (PMBLDC) motor, for cogging torque reduction. The notable feature of this motor is the simplicity of the design and low production cost. The purpose of this paper is to reduce the peak cogging torque of the motor. The focus is put on the stator topology tuning, and a new design for the stator poles is proposed. By determining the optimum stator pole arc length and the best pole shoe thickness, the cogging torque is significantly reduced. This new optimised motor design has been analysed in detail. The validation of the results is documented with respective figures and charts. Design/methodology/approach At the beginning, the design data for the 6/4 pole PMBLDC motor with concentrated three phase windings and asymmetric stator pole arcs is presented. In the study, this motor is taken as a reference model (A0, T0). A full performance finite element analysis of the reference motor has been carried out, and the weak points in the motor design have been identified. By simple design techniques, tuning the stator pole geometry, a two-stage design optimisation for cogging torque minimisation has been performed and the solution array has been derived. The optimised model is selected and proposed (Aopt, Topt). The comparative analysis of the reference and optimised motors show the advantages of the proposed novel design and prove the methodology. Findings The results of the work demonstrate how simple design techniques can minimise the peak of the cogging torque profile, while maintaining the specified electromagnetic torque value. The sensitivity of the cogging torque profile because of changes of the stator pole design inside the prescribed constraints is apparent. The stator poles of the reference motor have an arc length of 85° and pole shoe thickness of 6 mm. The newly shaped stator poles have an arc length of 78.5° and pole shoe thickness 4.8 mm. The peak-cogging torque has been reduced from 0.158 Nm to a respectable value of 0.066 Nm. However, to reduce electromagnetic torque ripple and pulsations, further investigations are required. Originality/value The paper presents an approach to cogging torque reduction for a 6/4 PMBLDC motor. A two-step original design procedure is introduced and an optimised stator pole geometry is defined. The minimised cogging torque has been demonstrated with improved usage of the active materials. This work could serve as a good basis for further optimisation of the motor design.

Performance analysis of segmented rotor switched reluctance motors with three types of winding connections for belt-driven starter generators of hybrid electric vehicles

2018 ◽  
Vol 37 (3) ◽  
pp. 1258-1270 ◽  
Author(s):  
Xiaodong Sun ◽  
Zhuicai Zhou ◽  
Long Chen ◽  
Zebin Yang ◽  
Shouyi Han
Keyword(s):  
Magnetic Flux ◽  
Hybrid Electric Vehicle ◽  
High Efficiency ◽  
Torque Ripple ◽  
Iron Loss ◽  
Switched Reluctance Motors ◽  
Content Type ◽  
Switched Reluctance ◽  
Output Torque ◽  
Hybrid Electric

Purpose Inductance, torque and iron loss are the key parameters of switched reluctance motors for belt-driven starter generators. This paper aims to present the analysis of a segmented rotor switched reluctance motor (SSRM) with three types of winding connections for hybrid electric vehicle applications by using a two-dimensional finite element method. Design/methodology/approach The rotor of the studied SSRM consists of a series of discrete segments, while the stator is made up of exciting and auxiliary teeth. First, the concept and structures of the different winding connections are introduced. Then, the magnetic flux path of the three types of winding connections for the SSRM is described. Second, the magnetic flux distributions in the three parts, i.e. the stator yoke, the stator tooth and the rotor segment, are described in detail to calculate the iron losses. Third, three SSRMs with the different winding arrangements are analyzed and compared to evaluate the distinct features of the studied SSRM. The analysis and comparison mainly include self-inductances, mutual inductances, phase currents, output torque and iron loss. Findings It is found that the self-inductances of the three types of winding connections are almost equal, and only the SSRM1 has a positive mutual inductance. In addition, the current waveforms of SSRM1 and SSRM2 are regular. However, it is irregular in SSRM3. It is shown that SSRM1 has better characteristics, such as higher output torque, high power density, lower torque ripple and iron loss. Originality/value This paper proposes and analyzes three novel winding connections for the SSRM to provide guidance for enhancing the output torque and reducing the iron loss to achieve high efficiency.

scholarly journals Pharmacokinetics and Safety of Intravitreal Caspofungin

2014 ◽  
Vol 58 (12) ◽  
pp. 7234-7239 ◽  
Author(s):  
Ying-Cheng Shen ◽  
Chiao-Ying Liang ◽  
Chun-Yuan Wang ◽  
Keng-Hung Lin ◽  
Min-Yen Hsu ◽  
...  
Keyword(s):  
High Performance ◽  
Potential Role ◽  
Elimination Rate ◽  
Retinal Toxicity ◽  
Primary Therapy ◽  
Time Intervals ◽  
Content Type ◽  
Fungal Endophthalmitis ◽  
Time Points ◽  
The Mean

ABSTRACTCaspofungin exhibits potent antifungal activities againstCandidaandAspergillusspecies. The elimination rate and retinal toxicity of caspofungin were determined in this study to assess its pharmacokinetics and safety in the treatment of fungal endophthalmitis. Intravitreal injections of 50 μg/0.1 ml of caspofungin were administered to rabbits. Levels of caspofungin in the vitreous and aqueous humors were determined using high-performance liquid chromatography (HPLC) at selected time intervals (10 min and 1, 2, 4, 8, 16, 24, and 48 h), and the half-lives were calculated. Eyes were intravitreally injected with caspofungin to obtain concentrations of 10 μg/ml, 50 μg/ml, 100 μg/ml, and 200 μg/ml. Electroretinograms were recorded 4 weeks after injections, and the injected eyes were examined histologically. The concentrations of intravitreal caspofungin at various time points exhibited an exponential decay with a half-life of 6.28 h. The mean vitreous concentration was 6.06 ± 1.76 μg/ml 1 h after intravitreal injection, and this declined to 0.47 ± 0.15 μg/ml at 24 h. The mean aqueous concentration showed undetectable levels at all time points. There were no statistical differences in scotopica-wave andb-wave responses between control eyes and caspofungin-injected eyes. No focal necrosis or other abnormality in retinal histology was observed. Intravitreal caspofungin injection may be considered to be an alternative treatment for fungal endophthalmitis based on its antifungal activity, lower retinal toxicity, and lower elimination rate in the vitreous. More clinical data are needed to determine its potential role as primary therapy for fungal endophthalmitis.

Torque production improvement of a five phase fractional-slot PM machine under faulty operation

2015 ◽  
Vol 34 (6) ◽  
pp. 1758-1770
Author(s):  
Hajer Rebai ◽  
Imen Abdennadher ◽  
Ahmed Masmoudi
Keyword(s):  
Open Circuit ◽  
Electromagnetic Torque ◽  
Propulsion Systems ◽  
Element Analysis ◽  
Content Type ◽  
Production Capability ◽  
Production Improvement ◽  
The Mean ◽  
Practical Implications ◽  
Fractional Slot

Purpose – The purpose of this paper is to deal with several approach to recover the torque production capability of a five phase double-layer fractional-slot PM machine under faulty operation. The considered fault is an open-circuit coil in a given phase. Design/methodology/approach – In a first step, the mean futures, such as the phase back-EMFs and the electromagnetic torque, are computed by finite element analysis under healthy operation, and are taken as references. Then, they are investigated, under a faulty coil, for different approaches to recover the torque production capability. Findings – A comparison of the potentialities of the torque recovery approaches has clearly highlight the superiority of the approach consisting in the re-adjustment of the current initial phases, in an attempt to equilibrate the resulting air gap MMF. Research limitations/implications – This work should be extended by an experimental validation of the predicted results regarding the back-EMFs and the electromagnetic torque. Practical implications – The investigation of the considered five phase fractional-slot PM machine under faulty operation should be extended to several faulty scenarios in order to fulfill the requirements of many applications such as the propulsion systems. Originality/value – The paper proposes different approaches to recover the torque production capability of a five phase fractional-slot PM machine under faulty operation.

Placental Transfer of Vitamin K1 and Its Implications in Fetal Hemostasis

1988 ◽  
Vol 60 (01) ◽  
pp. 039-043 ◽  
Author(s):  
L Mandelbrot ◽  
M Guillaumont ◽  
M Leclercq ◽  
J J Lefrère ◽  
D Gozin ◽  
...  
Keyword(s):  
Vitamin K ◽  
High Performance ◽  
Ultrasound Guidance ◽  
Placental Transfer ◽  
Vitamin K1 ◽  
Vitamin K Deficiency ◽  
Prothrombin Activity ◽  
Oral Supplementation ◽  
K Deficiency ◽  
The Mean

SummaryVitamin K status was evaluated using coagulation studies and/ or vitamin IQ assays in a total of 53 normal fetuses and 47 neonates. Second trimester fetal blood samples were obtained for prenatal diagnosis under ultrasound guidance. Endogenous vitamin K1 concentrations (determined by high performance liquid chromatography) were substantially lower than maternal levels. The mean maternal-fetal gradient was 14-fold at mid trimester and 18-fold at birth. Despite low vitamin K levels, descarboxy prothrombin, detected by a staphylocoagulase assay, was elevated in only a single fetus and a single neonate.After maternal oral supplementation with vitamin K1, cord vitamin K1 levels were boosted 30-fold at mid trimester and 60 fold at term, demonstrating placental transfer. However, these levels were substantially lower than corresponding supplemented maternal levels. Despite elevated vitamin K1 concentrations, supplemented fetuses and neonates showed no increase in total or coagulant prothrombin activity. These results suggest that the low prothrombin levels found during intrauterine life are not due to vitamin K deficiency.

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