Advanced Induction Motor End Ring Design Features for High Speed Applications

This paper presents advancements in induction motor endring design to overcome mechanical limitations and extend the operating speed range and joint reliability of induction machines. A novel endring design met the challenging mechanical requirements of this high speed, high temperature, power dense application, without compromising electrical performance. Analysis is presented of the advanced endring design features including a non uniform cross section, hoop stress relief cuts, and an integrated joint boss, which reduced critical stress concentrations, allowing operation under a broad speed and temperature design range. A generalized treatment of this design approach is presented comparing the concept results to conventional design techniques. Additionally, a low temperature joining process of the bar/end ring connection is discussed that provides the required joint strength without compromising the mechanical strength of the age hardened parent metals. A description of a prototype 2 MW, 15,000 rpm flywheel motor generator embodying this technology is presentedCenter for Electromechanic

Neurite outgrowth and gene expression profile correlate with efficacity of human induced pluripotent stem cell-derived dopamine neuron grafts

Transplantation of human induced pluripotent stem cell-derived dopaminergic (iPSC-DA) neurons is a promising therapeutic strategy for Parkinson's disease (PD). To assess optimal cell characteristics and reproducibility, we evaluated the efficacy of iPSC-DA neuron precursors from two individuals with sporadic PD by transplantation into a hemiparkinsonian rat model after differentiation for either 18 (d18) or 25 days (d25). We found similar graft size and dopamine (DA) neuron content in both groups, but only the d18 cells resulted in recovery of motor impairments. In contrast, we report that d25 grafts survived equally as well and produced grafts rich in tyrosine hydroxylase-positive neurons, but were incapable of alleviating any motor deficits. We identified the mechanism of action as the extent of neurite outgrowth into the host brain, with d18 grafts supporting significantly more neurite outgrowth than nonfunctional d25 grafts. RNAseq analysis of the cell preparation suggests that graft efficacy may be enhanced by repression of differentiation-associated genes by REST, defining the optimal predifferentiation state for transplantation. This study demonstrates for the first time that DA neuron grafts can survive well in vivo while completely lacking the capacity to induce recovery from motor dysfunction. In contrast to other recent studies, we demonstrate that neurite outgrowth is the key factor determining graft efficacy and our gene expression profiling revealed characteristics of the cells that may predict their efficacy. These data have implication for the generation of DA neuron grafts for clinical application

Structural properties and testing of a composite banding used in high-speed rotors

The use of high-strength structural composite bandings is essential for high-speed rotors. In addition to bandings designed for maximum stiffness and strength, there is also a need for bandings that exhibit a controlled radial growth during operation. Controlling the radial growth rate of rotor bandings to match the growth of other rotor components maximizes the structural integrity of the rotor by minimizing reaction forces between parts during operation. This paper presents the structural material properties and strain-to-failure of a composite banding built with a nontraditional layup consisting of high-strength IM7 hoop filament windings and a combination of T700 tape laid at 0deg and plusmn45deg. The analysis and structural test results used to determine the strength of a composite banding with this layup is discussedCenter for Electromechanic

Design and stress analysis of a high speed rotor for an advanced induction motor

This paper presents the particular mechanical design considerations and analysis results relating to an induction motor rotor designed specifically for high-speed, power dense, mobile applications. A unique end ring design is presented which balances the mechanical and electrical requirements of the high-speed, high-temperature design. Specification of core lamination material is treated in the context of managing spin stresses and maintaining radial contact pressure over the broad operating speed range. Analysis of the rotor bar extension configuration is described to accommodate the relative growth between the end ring and laminated core at operating speed and temperature. A low temperature joining process for the bar / end ring connections is presented that maintains the strength properties of the age hardened copper alloy materials of the squirrel cage assembly.Center for Electromechanic

Transient 3-D thermal analysis for an air-cooled induction motor

For an induction motor that is cooled by an airflow ventilated across the air gap between the rotor and stator, the rotor end-ring and stator end-turn cooling might influence the motor temperatures in the core sections appreciably. Detailed motor thermal modeling is typically required to provide transient rotor temperature distributions for rotor structural analysis and to predict stator temperature distributions to assure the maximum stator temperature is below the stator insulation temperature limit. For an air-cooled induction motor, transient 3-D finite element thermal analyses for both rotor and stator have been performed in this paper. In the stator thermal model, the slot conductors and various insulations were smeared and equivalent thermal properties were used to reduce modeling and computational effort. Position-dependent and time-dependent air cooling boundary conditions, which include air temperatures and forced convection heat-transfer coefficients, were applied to the 3-D thermal modelsCenter for Electromechanic

[¹⁸F]Difluorocarbene for positron emission tomography

The advent of total-body Positron Emission Tomography (PET) has vastly broadened the range of research and clinical applications of this powerful molecular imaging technology1. Such possibilities have accelerated progress in&nbsp;18F-radiochemistry with numerous methods available to&nbsp;18F-label (hetero)arenes and alkanes2. However, access to&nbsp;18F-difluoromethylated molecules in high molar activity (Am) is largely an unsolved problem, despite the indispensability of the difluoromethyl group for pharmaceutical drug discovery3. We report herein a general solution by introducing carbene chemistry to the field of nuclear imaging with a [18F]difluorocarbene reagent capable of a myriad of&nbsp;18F-difluoromethylation processes.&nbsp;In contrast to the tens of known difluorocarbene reagents, this&nbsp;18F-reagent is carefully designed for facile accessibility, high molar activity and versatility.&nbsp;The issue of Am&nbsp;is solved using an assay examining the likelihood of isotopic dilution upon variation of the electronics of the difluorocarbene precursor. Versatility is demonstrated with multiple [18F]difluorocarbene based reactions including O&ndash;H, S&ndash;H and N&ndash;H insertions, and cross-couplings that harness the reactivity of ubiquitous functional groups such as (thio)phenols,&nbsp;N-heteroarenes, and aryl boronic acids that are easy to install. Impact is illustrated with the labelling of highly complex and functionalised biologically relevant molecules and radiotracers.</p