DESIGN OF DUAL ROTOR AXIAL FLUX PERMANENT MAGNET GENERATORS WITH FERRITE AND RARE-EARTH MAGNETS

This article addresses dual rotor axial flux Ferrite permanent magnet (PM)  generator,  as an alternative to a surface mounted and  spoke types Nd-Fe-B generator which have concentrated windings. The performance parameters of all generators, particularly the efficiency, are identical. The design objective function is the generators mass minimization using a population-based algorithm. To predict the performance of yhe generators a finite element (FE) technique is applied. Besides, the aims of the design include minimizing cogging torque, examining different rotor pole topologies and different pole arc to pole pitch ratios. Three-dimensional FE technique is employed. It is shown that the surface mounted Ferrite generator topology cannot develop the rated torque and also has high torque ripple. In addition, it is heavier than the spoke type generator. Furthermore, it is indicated that the spoke type Ferrite PM generator has favorable performance and could be an alternative to rare-earth PM generators, particularly in wind energy applications. Finally, the performance of the designed generators is experimentally verified

DERATING OF THREE-PHASE SQUIRREL-CAGE INDUCTION MOTOR UNDER BROKEN BARS FAULT

This paper addresses derating of a three-phase squirrel-cage induction motor under rotor broken bars fault. For this purpose, a winding function based analytical model is used. Different types of effective losses including core losses and Ohmic losses are estimated using a full analytical method. The relationship between the induction motor losses and load is determined and it is shown that the core losses, known as the constant losses in the motor, vary with load. A proper function based on the induced electromotive force (emf), Steinmetz coefficients and load level are introduced to show variations of losses with the induction motor load. Finally, derating is applied assuming that the motor losses in all cases must be equal to that of the healthy induction motor

Analysis of Dynamic Behavior of Switched Reluctance Motor-Design Parameters Effects

Abstract-In the design of switched reluctance motor (SRM) and its drive, analysis and simulation of the dynamic behavior of the motor is essential. In the simulation process, model of the SRM and its controller is taken into account. In this paper motor characteristics are examined and effects of the motor design parameters, such as inductance, resistance and supply voltage, on the system response is studied. Variations of phase current and developed torque of the motor are predicted and discussed

Crash helmet – the harbinger of death: a case report

In one of the rarest form of freak accident, a young woman surrendered to her death in a manner that belie the reality only to be played back in a slow motion sequence. History is replete of instances in which death struck individuals in otherwise innocent forms. In this case – elaborated below – a helmet tucked under the crook of an elbow became the undoing causing the woman to topple backward in a slow-motion, the head striking the hard surface of the road and precipitating her death later in a hospital

An Evaluation of Inductances of a Squirrel-Cage Induction Motor Under Mixed Eccentric Conditions

Abstract-This paper presents a more precise model for computation of three-phase squirrel cage induction machine inductances under different eccentric conditions. Generally, available techniques are based on the winding function theory and simplification and geometrical approximation of unsymmetrical models of the motor under mixed eccentricities. This paper determines a precise geometrical model under the mixed eccentricity conditions and evaluates the inductances. Meanwhile, the evaluated inductances are compared to those calculated using different approximate geometrical models and the best approximation is recommended for a geometrical modeling of induction motor under eccentricity conditions

Prophylactic mesh placement for the prevention of incisional hernia in high-risk patients after abdominal surgery: A systematic review and meta-analysis

Background and objectives: In high-risk populations, the efficacy of mesh placement in incisional hernia (IH) prevention after elective abdominal surgeries has been supported by many published studies. This meta-analysis aimed at providing comprehensive and updated clinical implications of prophylactic mesh placement (PMP) for the prevention of IH as compared to primary suture closure (PSC).Materials and methods: PubMed, Science Direct, Cochrane, and Google Scholar were systematically searched until March 3, 2020, for studies comparing the efficacy of PMP to PSC in abdominal surgeries. The main outcome of interest was the incidence of IH at different follow-up durations. All statistical analyses were carried out using Review Manager version 5.3 (The Nordic Cochrane Centre, The Cochrane Collaboration, 2014) and Stata 11.0 (Stata Corporation LP, College Station, TX). The data were pooled using the random-effects model, and odds ratio (OR) and weighted mean differences (WMD) were calculated with the corresponding 95% confidence interval (CI).Results: A total of 3,330 were identified initially and after duplicate removal and exclusion based on title and abstract, 26 studies comprising 3,000 patients, were included. The incidence of IH was significantly reduced for PMP at follow-up periods of one year (OR= 0.16 [0.05, 0.51]; p=0.002; I2=77%), two years (OR= 0.23 [0.12, 0.45]; p\u3c0.0001; I2=68%), three years (OR= 0.30 [0.16, 0.59]; p=0.0004; I2= 52%), and five years (OR=0.15 [0.03, 0.85]; p=0.03; I2=87%). However, PMP was associated with an increased risk of seroma (OR=1.67 [1.10, 2.55]; p= 0.02; I2=19%) and chronic wound pain (OR=1.71 [1.03, 2.83]; p= 0.04; I2= 0%). No significant difference between the PMP and PSC groups was noted for postoperative hematoma (OR= 1.04 [0.43, 2.50]; p=0.92; I2=0%), surgical site infection (OR=1.09 [0.78, 1.52]; p= 0.62; I2=12%), wound dehiscence (OR=0.69 [0.30, 1.62]; p=0.40; I2= 0%), gastrointestinal complications (OR= 1.40 [0.76, 2.58]; p=0.28; I2= 0%), length of hospital stay (WMD= -0.49 [-1.45, 0.48]; p=0.32; I2=0%), and operating time (WMD=9.18 [-7.17, 25.54]; p= 0.27; I2=80%).Conclusions: PMP has been effective in reducing the rate of IH in the high-risk population at all time intervals, but it is associated with an increased risk of seroma and chronic wound pain. The benefits of mesh largely outweigh the risk, and it is linked with positive outcomes in high-risk patients

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Način optimizacije zunanjega rotorja za trajni magnetni sinhronski motor

The Finite Element Method (FEM) is a prominent analysis approach. Although it is applicable for simulation and optimization of electrical machines, FEM is a very time-consuming technique. One of the approaches to shorten the optimization runtime is the use of surrogate models instead of FEM. In this paper, the design and optimization of an outer rotor permanent magnet synchronous motor for a hybrid vehicle are investigated. Response surface methodology (RSM) with four input variables is integrated with a sequential quadratic programming algorithm for optimization. Before the optimization, the performance of the surrogate model in the prediction of untried points is validated. Finally, the optimal motor is simulated by FEM to verify the results of RSM-based optimization, and the outputs of both models are compared.Metoda končnih elementov (FEM) je eden boljših pristopov analize. Čeprav je FEM uporabna za simulacijo in optimizacijo električnih strojev, je pa zelo zamudna tehnika. Eden od pristopov za skrajšanje trajanja optimizacije je uporaba nadomestnih modelov namesto FEM. V prispevku je raziskano načrtovanje in optimizacija sinhronskega motorja s trajnim magnetom zunanjega rotorja za hibridno vozilo. Metodologija odzivne površine (RSM) s štirimi vhodnimi spremenljivkami je integrirana z algoritmom zaporednega kvadratnega programiranja za optimizacijo. Pred optimizacijo je bila uspešnost nadomestnega modela pri napovedovanju neizkušenih točk potrjena. Končno FEM simulira optimalni motor, da preveri rezultate optimizacije na osnovi RSM in primerja izhode obeh modelov