Some Design Calculations for a 60kW, 6000 rpm, 4/6 SRM

This report contains results from a finite element study of the SR machine whose dimensions were provided by Mr Lewis Unnewehr of Sullair Corporation. The objective of the study is to determine the static and steady-state operational characteristics of a given machine design to see if it meets certain design specifications. The study made use of a two-dimension, finite element program that has been developed and described in [1-3]. The same set of references also contained information on the simulation methods and types of control used in this study. Part I of this report presents the basic input data used in this study. The iron parts, including that of the shaft, are assumed to have the magnetic characteristics of M19 steel. The current distribution in the stator coils is assumed to be uniform. Part II contains the results from the FEM calculations: included in here are static characteristics of the flux distribution at several rotor positions, and computed profiles of the flux linkages, the induced emf, and the static torque as a function of rotor position for a range of current excitation. These static characteristics are for the base case design given in Table 1 and are obtained with only one stator phase energized at a time. Part III of the report contains results from sensitivity studies to determine the effects of variations in the airgap, in the relative width of the stator to rotor poles, in the shape of rotor poles, and in the skewing of the rotor poles. Unless otherwise stated the curves and data presented in this report are for the base case dimensions given in Table 1. Sensitivity analysis on airgap length, pole shape, and pole width have been obtained by making the appropriate changes on the rotor pole, the stator dimensions remained the same as those given in Table 1. Also presented are a set of static characteristics for a machine with a smaller airgap length of 0.5 mm. Finally, Part IV of report contains steady-state operational characteristics of the stator current and shaft torque of the machine operating in the current- and angle-control modes as predicted from a steady state simulation assuming a constant input dc voltage. In the steady state simulation the electrical condition of the machine and its torque output are modeled by the appropriate flux linkage, induced emf, and developed torque profiles given in Part II. At the end of the report is a brief discussion on some of the effects that we have studied, and the conclusion that the basic design, with standard angle and current controls, appears to be capable of delivering the desired torque

Biomaterials in Valvular Heart Diseases

Valvular heart disease (VHD) occurs as the result of valvular malfunction, which can greatly reduce patient\u27s quality of life and if left untreated may lead to death. Different treatment regiments are available for management of this defect, which can be helpful in reducing the symptoms. The global commitment to reduce VHD-related mortality rates has enhanced the need for new therapeutic approaches. During the past decade, development of innovative pharmacological and surgical approaches have dramatically improved the quality of life for VHD patients, yet the search for low cost, more effective, and less invasive approaches is ongoing. The gold standard approach for VHD management is to replace or repair the injured valvular tissue with natural or synthetic biomaterials. Application of these biomaterials for cardiac valve regeneration and repair holds a great promise for treatment of this type of heart disease. The focus of the present review is the current use of different types of biomaterials in treatment of valvular heart diseases

Lead and cadmium levels in raw bovine milk and dietary risk assessment in areas near petroleum extraction industries

P. 308-314Oil fields are a source of heavy metal pollution, but few studies have evaluated its impact on the intake of these contaminants through milk, an important food especially for children. From February 2015 to 2016, 118 samples of raw cow's milk, 14 of fodder and 8 of water in Southwest Iran were collected from farms close to oil fields or related industries. Lead (Pb) and cadmium (Cd) levels were evaluated by graphite furnace atomic absorption spectrometry. Mean ± SE in milk and fodder were 47.0 ± 3.9 and 54.0 ± 6.9 μg/kg for Pb, and 4.7 ± 1.0 and 3.5 ± 1.3 μg/kg for Cd. No Pb or Cd was detected in water. Most milk samples (82.2%) for Pb were above the permissible limits (20 μg/kg). Exposure to Pb and Cd from milk consumption was calculated in two scenarios: mean and maximum exposure for the age range of 2–90 years. The intake of an average Iranian adult (25 years, 60 kg b. w., 0.14 kg milk/day) would be 6.6 μg Pb and 0.66 μg Cd/day (WI of 46.2 and 4.6 μg, respectively), well below the risk values proposed by some international organizations, even in the maximum exposure scenario. However, Pb exposure for infants and toddlers may be closer to the risk values, since milk and milk products could be the main contributor to Cd and Pb, and small children consume 2–3 times more food than adults relative to their body weight. The risk of Pb and Cd exposure through milk close to oil fields should be considered and a monitoring plan for these contaminants is strongly recommended.S

Performance characteristics of switched-reluctance motor drive

In this thesis, methods and computational techniques for predicting the static and steady state characteristics of a switched reluctance motor drive are developed and the predicted characteristics are compared with experimental results. Because of high local saturation and narrow airgap in the SR motor, accurate calculation of the static characteristics of the torque, flux linkage, inductances, and speed emf from its FE field solution is not straightforward. For the purpose of this study, a two-dimensional finite element model is developed to handle the nonlinear magnetic field inside the machine. Based on a thorough study of the potential sources of errors in the field solution and in the computational methods used in postprocessing, new guidelines are developed regarding the shape and uniformity of the mesh in the airgap and the preservation of these qualities of the mesh as the rotor is rotated. When the proposed guidelines on the mesh configuration and its rotation were used, significant improvement in the accuracy of the field distribution and in the accuracy of the predicted torque/angle characteristics as compared to the experimentally measured torque was observed. Furthermore, all three methods of torque calculation, namely global virtual work, local virtual work, and Maxwell-stress tensor methods are converging to the same results and the torque/angle characteristics are smooth. Improvement in the prediction of such static characteristics is also essential to a realistic prediction of the steady state behavior. In the study of steady state performance of the SRM drive, the converter is approximated by a controlled, square wave pulse generator. In the integration process, the coefficients of the governing differential equation, being dependent on the phase current and rotor angle, are updated using surface interpolation method on the static characteristics. The predicted steady state characteristics compare favorable with the experimental results over a wide range of torque/speed variation

A Novel Control Strategy for Three-Phase UPS Based on B-Spline Network

This paper is concerned with the control of three-phase Uninterruptible Power Supply (UPS) systems based on a B-spline Network (BSN). A UPS must be able to maintain regulated output voltage in the face of all line/load disturbances. To achieve this, the control system of a UPS must have a fast transient response and a low steady-state error. Fast controllers cannot always maintain the required steady-state accuracy. Therefore, in this paper, a hybrid control solution is proposed. In the proposed method, a fast yet simple controller based on deadbeat (DB) control law is used to achieve the fast transient response required for UPS output voltage control. A B-spline based controller is added to the deadbeat controller to improve steadystate performance of the UPS system. This results in distortion free output voltage along with a fast error convergence. The system modeling and controller design for the proposed structure are presented in this paper. Simulations results are shown for verification of the theoretical analysi

A New Method for Leakage Inductance Calculation of Transverse Flux Machines

This paper presents a new analytical method for leakage inductance calculation of transverse flux permanent magnet machines. In this method, leakage flux paths are predicted base on the finite element results, and then all paths would be modeled by flux tubes. Finally, the inductance of the machine would be obtained by calculation of the permeance of flux tubes. The validity of the proposed model is verified by comparing the Finite Element results with the results obtained from the proposed approach. Comparing the results shows that the proposed model is able to accurately estimate the leakage inductance of the machine with an average error less than 9%

Generalizability in convolutional neural networks for various types of building scene recognition in High-Resolution imagery

Building recognition is a core task for urban image classification (mapping), especially in optical high-resolution imagery. Convolutional Neural Networks (CNNs) have recently achieved unprecedented performance in the automatic recognition of objects (e.g. buildings, roads, or trees) in high-resolution imagery. Although these results are promising, questions remain about generalizability. This is a great challenge, as there is a wide variability in the visual characteristics of the building image scene across different geographic locations. CNNs are overfitted with limited and low diversity samples and are tested on the same or nearby geographic locations. In this work, we propose two scenarios with regard to transfer learning CNN features for building scene classification. We also investigate the generalizability of CNNs for building recognition across different geographic locations. The results of the two scenarios show that the final model, generalizable in different geographic locations, unseen areas

Alternate Rotor Design for Line-Start Synchronous Reluctance Motor With Minimum Use of Copper

Line-start synchronous reluctance motors (LSSynRM) combine the high efficiency of synchronous reluctance Motors (SynRM) with the self-starting capability of induction motors. They operate at synchronous speed in steady state and produce minor rotor losses, thereby providing higher efficiency than induction motors and a higher power density. Despite the simple structure of LSSynRM, its analysis, modeling, and optimal design pose several challenges. In particular, design trends aiming at higher starting capabilities and improved steady-state operation pose significant hurdles. In this study, three synchronous reluctance motors with line-start capability are designed to achieve maximum efficiency at steady-state operation with the optimum amount of copper for starting. The induction cage is constructed using rectangular bars installed in flux barriers to minimize the changes in performance under the steady-state condition. Although different rotor shapes offer similar steady-state performance, they achieve synchronism using different cage bar widths. The rotor with the lowest copper weight is selected for manufacturing. The prototype is constructed based on the optimal design. The experimental results are in good agreement with the simulation results

Opportunities and Challenges of Switched Reluctance Motor Drives for Electric Propulsion: A Comparative Study

Selection of the proper electric traction drive is an important step in design and performance optimization of electrified powertrains. Due to the use of high energy magnets, permanent magnet synchronous machines (PMSM) have been the primary choice in the electric traction motor market. However, manufacturers are very interested to find a permanent magnet-free alternative as a fallback option due to unstable cost of rare-earth metals and fault tolerance issues related to the constant permanent magnet excitation. In this paper, a new comprehensive review of electric machines (EMs) that includes various new switched reluctance machine topologies in addition to conventional EMs such as PMSM, induction machine, synchronous reluctance machine (SynRel), and PM-assisted SynRel is presented. This paper is based on performances such as power density, efficiency, torque ripple, vibration and noise, and fault tolerance. These systematic examinations prove that recently proposed magnetic configurations such as double-stator switched reluctance machine can be a reasonable substitute for permanent magnet machines in electric traction applications