Five-Phase Modular External Rotor PM Machines with Different Rotor Poles: A Comparative Simulation Study

The performance of fault-tolerant modular permanent magnet machines depends on the proper selection of the pole and slot numbers which result in negligible coupling between phases. The preferred slot and pole number combinations eliminate the effect of low-order harmonics in the stator magnetomotive force and thereby the vibration and stray loss are reduced. In this paper, three external rotor machines with identical machine dimensions are designed with different slots per phase per pole ratios. A simulation study is carried out using finite element analysis to compare the performance of the three machines in terms of machine torque density, ripple torque, core loss, and machine efficiency. A mathematical model based on the conventional-phase-model approach is also used for the comparative study. The simulation study is extended to depict machine performance under fault conditions

Studying the effect of over-modulation on the output voltage of three-phase single-stage grid-connected boost inverter

AbstractVoltage boosting is very essential issue in renewable-energy fed applications. The classical two-stage power conversion process is typically used to interface the renewable energy sources to the grid. For better efficiency, single-stage inverters are recommended. In this paper, the performance of single-stage three-phase grid-connected boost inverter is investigated when its gain is extended by employing over-modulation technique. Using of over-modulation is compared with the employment of third order harmonic injection. The latter method can increase the inverter gain by 15% without distorting the inverter output voltage. The performance of extended gain grid-connected boost inverter is also tested during normal operation as well as in the presence of grid side disturbances. Simulation and experimental results are satisfactory

A ring-connected dual active bridge based DC-DC multiport converter for EV fast-charging stations

This paper proposes a multiport DC-DC converter for EV fast-charging stations. The proposed converter is comprised of Ring-Connected Dual Active Bridge (RCDAB) DC-DC converters, where the connection point between every two adjacent DABs provides a DC port. Bypass switches are added to each DAB to eliminate unnecessary power processing stages in the event of idle ports (no EVs) (open circuit ports). The nature of the ring connection of the RCDAB theoretically allows infinite internal power flow solutions within the ring to satisfy a certain power flow scenario at the DC ports, hence, the optimal power flow solution can be selected to minimize total RMS current and losses. Single-phase shift control is applied to this optimization problem to make it simple. A novel closed-loop control scheme using Bisection optimization is developed to minimize the total RMS current. A control-hardware-in-the-loop (CHiL) validation is carried out for a 5-port network of the proposed topology to investigate the converter efficiency and fault tolerance/availability characteristics. Also, an experimental hardware validation is implemented for a 3-port network where different scenarios for power flow and faults are performed. Finally, a comparative discussion between the proposed topology and other multiport topologies in literature is presented revealing the superior performance of the RCDAB topology

Traction system with on-board inductive power transfer

In traction applications based on long primary and short secondary type, contactless electrical energy transmission can offer distinct advantages over the conventional energy transmission based on catenary system to provide the required on-board power. In this paper, a linear brushless doubly fed machine with dual-primary windings and a reluctance secondary mover is proposed as a means of providing decoupled traction and on-board power. The machine primary contains two three-phase windings with different number of poles while an additional third winding is added around rotor saliencies forming a third output electric port to provide the required on-board power. A prototype machine is designed and simulated using 2D finite element analysis to verify the proposed concept.Qatar National Research FundScopu

Significance of computerized tomography and nasal cytology in the diagnosis of rhinosinusitis among asthmatic children

Background: Chronic sinusitis, allergic rhinitis, and asthma are conditions that frequently coexist. Nasal sinus disease may contribute to poor control of asthma; this suggests that sinonasal involvement might be a risk factor for asthma severity and morbidity. Proposed mechanisms of this interaction include the presence of postnasal drip, nasobronchial reflex or systemic effect of mediators released from inflamed paranasal sinus tissue. Objective: In the present study, we sought to investigate the relationship of sinonasal inflammation as assessed by coronal sinus computerized tomography (CT) scanning, nasal cytology score, and asthma severity. Methods: Twenty-five children with asthma were recruited from the Pediatric Respiratory Clinic of Ain Shams University. Their ages ranged from 5-13 years with a mean age of 7.78 years. Twenty healthy children who were age- and sex-matched and who had normal sinus CT scans were selected as the control group. Patients were subjected to asthma severity assessment, nasal cytology, total serum IgE assay, and paranasal CT scanning and scoring. Results: Sinus CT scoring showed abnormalities in 88% of asthmatic children, and sinus CT scores correlated positively to asthma severity. Nasal cytology scores for eosinophils and neutrophils correlated positively with sinus CT scores. The most frequent symptoms associated with sinusitis were rhinorrhea (68%) and nasal obstruction (40%). The maxillary sinus was the most frequently affected one followed by the ethmoid sinus. Pathological features included mucosal thickening, osteomeatal complex occlusion, and polyp formation. Conclusion: Computed tomography scan is a useful diagnostic tool for assessment of sinus disease in asthmatic children. Rhinosinusitis is a common asthma comorbidity. Nasal eosinophil or neutrophil score >0.5 provides a better predictive value for rhinosinusitis compared to total serum IgE.Keywords: computerized tomography, nasal sinus, asthma, sinusitis, allergic rhinitis, childrenEgypt J Pediatr Allergy Immunol 2003; 1(2):94-10

Postfault operation of five-phase induction machine with minimum total losses under aingle open-phase fault

Five-phase induction machines (FPIM) have attracted notable interest in safety critical applications as well as wind energy generation systems. This is largely due to their additional degrees of freedom that retain the machine starting/running steadily under fault conditions. In the available literature, postfault operation of multiphase machines is typically implemented using two techniques: minimum losses (ML) or maximum torque per ampere (MT) strategies. The optimization embedded into the control strategy, however, mostly addresses minimization of the stator copper loss, while the effect of the rotor loss and core loss are discarded in the optimal current calculation. This paper revisits postfault operation of the FPIM under single open phase fault (1OPF) by including the effect of both rotor loss and core loss on the machine's optimal current calculation over the full achievable loading range. The proposed searching algorithm, which combines the advantages of both MT and ML techniques, attempts to minimize the total machine losses induced by the current components of both the fundamental \alpha \beta and the secondary xy subspaces. The theoretical findings have been experimentally validated using a 1.5Hp five-phase prototype system