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This article presents the simultaneous magnetic and structural topology optimization of a transverse laminated synchronous reluctance machine rotor using a solid isotropic with material penalization (SIMP)-based approach with the globally convergent method of moving asymptotes (GCMMA) optimization algorithm. Magneto-structural single and multi-objective optimization formulations are presented. The single objective formulation maximizes the average torque subject to constraints on torque ripple, Von Mises stress, and compliance. The multiobjective formulation simultaneously maximizes average torque and minimizes compliance subject to constraints on torque ripple and Von Mises stress. In both optimization formulations, the electrical steel densities in the rotor mesh elements are the control variables. Including stress and compliance in the optimization formulation ensures a structurally feasible design. The design-dependent centripetal force contributed by each element in the rotor mesh is considered dependent on its density and mass. An intermediate density material issue is observed where the density of the material in a mesh element does not converge fully to air or electrical steel. This issue is addressed through the use of a thresholding mass function which forces the convergence of the mass but not the density. The two optimization formulations are compared for rotors operating at 4000 and 12 000 r/min. An initial magnetic only topology optimization is used to seed the magneto-structural topology optimization to decrease the computational time. The impact of the magnetic only seed and rotor mesh density on the optimization outcomes is also examined. [ABSTRACT FROM AUTHOR]

Research into electric machine windings with reduced magnetomotive force (MMF) space harmonic content has a long history. However, attention has often been confined to lower order harmonics with larger magnitudes. To more clearly and easily visualize the MMF space harmonic spectrum, this paper will explain the phenomenon of harmonic “families” intrinsic to a majority of electric machine windings. With a concise proof, it will be shown that within each family, the harmonic components have magnitudes that are inversely proportional to their orders. As a consequence, harmonics of the same family have the same winding factor. The number of families and, hence, different winding factors is found to be only a fraction of the number of slots of a unit machine. The family phenomenon greatly simplifies the determination of an MMF harmonic spectrum, envisions the behavior of higher order components, and predicts how a design change can improve the winding harmonic profile. When the family phenomenon disappears and the special cases with enlarged periods are also discussed. Two examples, both eliminating the 5th- and 7th-order harmonics but with very different harmonic spectra, are analyzed and compared to illustrate the power of the family phenomenon to aid the design of windings with improved electromagnetic performance. [ABSTRACT FROM AUTHOR]

This paper studies the design of electric machine windings with reduced magnetomotive force (MMF) space harmonic content by adjusting the slot distribution and coil turns. Closed-form expressions for the winding factor and harmonic magnitudes established from a mathematical representation of winding functions are used to formulate the MMF space harmonic suppression problem. The framework is applicable to both distributed windings and fractional-slot concentrated windings (FSCWs) and can be solved with different techniques. No special requirements on the slot/pole combination and the number of layers are necessary. One example uses a linear algebraic technique to solve simultaneous equations and the result is a mixed-layer distributed winding. The process also reveals the criterion when multiple requirements on the winding factor and harmonic magnitudes can be satisfied concurrently. Contour plots are included to provide additional graphical insight. Another example designs a 24-slot 22-pole FSCW subset with numerical optimization. The resultant winding is a four-layer FSCW with two subsets and 3/4 of the harmonic orders are eliminated. The performance improvement of this winding is verified with finite-element simulations. [ABSTRACT FROM PUBLISHER]

A new switched-reluctance machine (SRM) topology with combined rotary and reciprocating rectilinear movement is introduced in this paper. The topology of this machine is based on the conventional radial-flux SRM with a modified rotor structure. Unlike the other rotary-translational electromechanical systems which have separate units, one for rotary motion and another for translational reciprocating motion, the proposed machine achieves combined rotary-reciprocating (RR) movement with just one set of stator coils around each pole identical to the conventional SRM. By exciting each pole of the stator, both radial and axial magnetic flux will be produced in the air gap of the machine. As a result, the electromagnetic reluctance torque around the axis of the rotation and the reluctance force along the axis of translational movement are produced. Details of the rotor structure and machine operation are presented. Magnetic equivalent circuit (MEC) analytical equations are derived for four operational points within the RR motion cycle. Finite-element analysis (FEA) is utilized to validate the analytical MEC equations. The output performance profiles are simulated for two example machines using static 3-D FEA to investigate the impact of the axial displacement of the consequent poles. In addition, a sensitivity analysis is carried out to investigate the impact of the rotor pole angle on the torque and force production of the machine. The dynamic behavior of the proposed structure is analyzed and discussed for two displacements of the consequent axially shifted poles. [ABSTRACT FROM PUBLISHER]

This paper describes the modeling, optimization, mechanical design, and experimental characterization of a high power density wound field synchronous machine (WFSM) for electric vehicle traction applications. The WFSM is designed for brushless rotor field excitation using an axial flux hydrodynamic capacitive power coupler (CPC). The flexible design environment, which was used for large-scale multiobjective optimization of the WFSM, is described. A prototype WFSM, spray cooled with automatic transmission fluid, with an 80-kW output at a base speed of 4000 r/min has been tested. The prototyped WFSM achieves volumetric torque and power densities of 17.22 N·m/L and 7.19 kW/L referred to the envelope cylindrical volume of the active materials plus spray cooling rings. The specific torque and power densities are 4.69 N·m/kg and 1.95 kW/kg referred to the mass of the active materials and the shaft. The prototyped CPC provided up to 1-kW excitation power with a mass 600 g and volume of 0.271 L. [ABSTRACT FROM AUTHOR]

This paper presents a deadbeat-direct torque and flux controller for wound field synchronous machines (WFSMs) without damper/amortisseur windings. Compared to induction machines (IMs) or interior permanent magnet synchronous machines (IPMSMs), WFSMs have an additional degree of freedom through variable field excitation. Discrete time current and flux linkage observers are derived, which model the dynamics and cross coupling introduced by the variable field excitation. The variable field excitation also allows the torque line for the desired change in torque to be shifted on a sample by sample basis compared to IMs or IPMSMs where the torque line is static. This provides the opportunity to actively distribute the transient torque between the rotor and stator windings. A field flux linkage command is derived to achieve unity displacement power factor in the steady state. Experimental results are presented to demonstrate decoupled torque and flux linkage control. [ABSTRACT FROM PUBLISHER]

This paper proposes a systematic approach for the development of electric machine windings with reduced magnetomotive force (MMF) space harmonic content. By identifying the levels and slot position angles in the winding function of an electric machine winding, the winding factor, the magnitudes of individual harmonic components and thus the MMF spectrum of a winding can be represented mathematically as functions of the levels and angles. With numerical optimization, these functions can act as the constraints and the objective function. A typical formulation is to limit the magnitudes of undesired harmonics and to maximize the winding factor of the working component. The result of the optimization is often a new winding layout with potentially unequally pitched slots and different turns for the coils within a phase, and reduced or even eliminated harmonic orders of design interest, while maintaining a reasonable winding factor. The mathematical representation and design approach is applicable to both distributed windings and fractional-slot concentrated windings (FSCWs), with no special requirements on the slot/pole combination and the number of layers. Two design examples, a mixed-layer distributed winding and a 24-slot, 22-pole double-layer FSCW, are shown to have improved electromagnetic performance with finite element simulations. [ABSTRACT FROM AUTHOR]

This paper examines the relationship between rotor design, saliency-based signal injection sensorless control, and power conversion properties for four industrially relevant interior permanent-magnet machine configurations: a 36-slot 6-pole stator with v bar rotor, a 36-slot 6-pole stator with flat bar rotor, a 9-slot 6-pole stator with v bar rotor, and a 9-slot 6-pole stator with flat bar rotor. The influence of rotor geometric design variables over the range of current densities at the maximum torque per ampere angle was found using a design of experiments' methodology and standardized regression coefficients. Tradeoffs between sensorless control and power conversion properties are found using a Monte Carlo methodology. Power conversion and sensorless control properties were analyzed using hybrid static and time-stepping finite-element simulations. [ABSTRACT FROM AUTHOR]

This paper describes the design and experimental evaluation of two high-efficiency interior permanent-magnet (IPM) motors for use in a commercial transcritical \CO2 (R-744) heat pump water heater (HPWH). Two IPM topologies, a 36-slot 6-pole topology and a 9-slot 6-pole topology, were selected, optimized, and prototyped using a common flat-bar IPM rotor. The experimental analysis includes standard measurements of electrical machine parameters, and dynamometer tests. The initial measurements of the \CO2 compressor performance with a stock line-fed induction machine and the 36-slot 6-pole IPM configuration have been completed. This paper finds a small isentropic compressor efficiency improvement from using the 36-slot 6-pole IPM motor compared to the stock line-fed induction machine at rated operating conditions (essentially constant speed). This paper also expands the open literature on the impact of high-efficiency motor drives on \CO2 compressor operation and \CO2 HPWH systems. [ABSTRACT FROM AUTHOR]

A magneto-structural combined dimensional and topology optimization approach for interior permanent magnet synchronous machine (IPMSM) rotor design is proposed using the solid isotropic material with penalization (SIMP) density-based topology optimization method. This method optimizes the location and dimensions of the permanent magnets (PMs) embedded in the rotor, while simultaneously optimizing the lamination flux barriers using topology optimization. To allow for the location and dimensions of the PMs to change a Laplace smoothing mesh deformation technique is used. Three examples of IPMSM rotor optimizations are presented to demonstrate the proposed approach. In addition, a geometric template-based optimization is carried out for a comparison to one of the dimensional and topology optimized examples to better illustrate the difference. [ABSTRACT FROM AUTHOR]

The behavior of rotor eccentricities in current-regulated interior-permanent-magnet machines is investigated. The study focuses on two typical topologies of significant industrial relevance: machines with distributed windings with two slots per pole and phase and motors with concentrated coils and three slots per pole pair. The effect of stator-winding parallel paths is examined for both cases. Coil and terminal electrical quantities and radial forces were simulated using finite-element analysis. Unbalanced operation, where the currents are not equal in parallel phase connections due to eccentricity, is also investigated. Experimental measurements of electrical quantities and forces on motors with static eccentricity are carried out using two special test setups. The experimental measurements validated the simulation results. [ABSTRACT FROM AUTHOR]

Zero-to-low-speed flux/rotor-position self-sensing techniques rely on the interaction of saliencies (asymmetries) with an injected signal or special switching pattern in the inverter to produce a response which contains information about the location of the saliency. In this paper, three types of deterministic spatial rotor position saliencies are introduced into an induction machine (IM). The saliencies were created by modulating the following: 1) the rotor bridge opening width; 2) the rotor bridge opening height; and 3) the rotor bridge opening fill. The influence of saliency geometric design variables on the self-sensing and power conversion properties is determined using a design of experiments and response surface methodology. An example IM design, which maximizes the self-sensing properties while preserving power conversion abilities, is presented. Modulation of the rotor bridge fill appears to be the least desirable saliency type. Both rotor bridge opening width and height modulations can be used successfully, but the rotor bridge opening width modulation requires extra simulations to characterize the self-sensing properties. [ABSTRACT FROM AUTHOR]

Enhancements to the deadbeat-direct torque and flux control (DB-DTFC) of wound field synchronous machines (WFSMs) are proposed allowing for operation at low sampling frequency to fundamental frequency ratios. Discrete-time current and flux linkage observers, which properly model WFSM $d\text{--}q$ and $d\text{--}f$ cross-coupling are formed using a Taylor series approximated sampled Laplace approach. The effect of the Taylor series order on the discretization error and model accuracy is examined. The torque curve to determine the inverter voltage commands is derived from the flux linkage model coefficients. Experimental comparison of the WFSM torque response is made between the classical DB-DTFC with current and flux observers formed using a z-transform approach and the torque line derived from a forward Euler method and the newly proposed observers and torque curve. [ABSTRACT FROM AUTHOR]

Introduction: Hallway beds in the emergency department (ED) produce lower patient satisfaction and inferior care. We sought to determine whether socioeconomic factors influence which visits are assigned to hallway beds, independent of clinical characteristics at triage. Methods: We studied 332,919 visits, across 189,326 patients, to two academic EDs from 2013-2016. We estimated a logistic model of hallway bed assignment, conditioning on payor, demographics, triage acuity, chief complaint, patient visit frequency, and ED volume. Because payor is not generally known at the time of triage, we interpreted it as a proxy for other observable characteristics that may influence bed assignment. We estimated a Cox proportional hazards model of hallway bed assignment on length of stay. Results: Median patient age was 53. 54.0% of visits were by women. 42.1% of visits were paid primarily by private payors, 37.1% by Medicare, and 20.7% by Medicaid. A total of 16.2% of visits were assigned to hallway beds. Hallway bed assignment was more likely for frequent ED visitors, for lower acuity presentations, and for psychiatric, substance use, and musculoskeletal chief complaints, which were more common among visits paid primarily by Medicaid. In a logistic model controlling for these factors, as well as for other patient demographics and for the volume of recent ED arrivals, Medicaid status was nevertheless associated with 22% greater odds of assignment to a hallway bed (odds ratio 1.22, [95% confidence interval, CI, 1.18-1.26]), compared to private insurance. Visits assigned to hallway beds had longer lengths of stay than roomed visits of comparable acuity (hazard ratio for departure 0.91 [95% CI, 0.90-0.92]). Conclusion: We find evidence of social determinants of hallway bed use, likely involving epidemiologic, clinical, and operational factors. Even after accounting for different distributions of chief complaints and for more frequent ED use by the Medicaid population, as well as for other visit characteristics known at the time of triage, visits paid primarily by Medicaid retain a disproportionate association with hallway bed assignment. Further research is needed to eliminate potential bias in the use of hallway beds. [ABSTRACT FROM AUTHOR]

Wound field synchronous generators (WFSG) are the standard electromechanical converter for back-up and utility scale power generation. Maintenance costs may be minimized by adopting noncontact or “brushless” technologies to replace sliding slip ring connections for rotor field excitation. This paper presents a brushless excitation approach using ceramic insulated sleeve (journal) bearings with oil lubrication to form capacitively coupled slip rings, in contrast to more traditional inductive brushless exciters and rotary transformers. This capacitive power transfer (CPT) approach exhibits advantages including low weight, low volume, and has a relatively simple construction using off-the-shelf components. Analysis, design, and prototype construction of the CPT system are presented. Experimental results demonstrate that 1.7 nF of capacitive coupling transfers 340 W to the rotor field winding of a 10 kW 208 V WFSG. Voltage regulation of a WFSG is demonstrated during steady state and 1 per unit load step changes yielding a NEMA-MG1 class G2 rating. [ABSTRACT FROM AUTHOR]

The authors discuss the results of the civil-military collaboration efforts, which was part of the initial medical response from the U.S. to the disastrous earthquake that hit Haiti in January 2010. They say that a couple of days after the earthquake, a medical relief team under the auspices of the nonprofit group International Medical Corps provided emergency medical support, which was made up of emergency nurses and emergency physicians. They also mention how the U.S. military's support was unequivocally integral to the medical mission's success.