Magnetic Model Self-Identification for PM Synchronous Machine Drives

The Magnetic Model Self-Identification of PM Synchronous machines is proposed and experimentally validated. Provided that the shaft is free to turn, the commissioning procedure consists of spinning the machine to positive and negative speed values by way of an appropriate pattern of dq current reference values. The flux linkage versus current curves of the machine are constructed during the test via the standard measurements available on any industrial drive: phase currents, dc-link voltage and shaft position. Respect to the literature, the proposed method does not require a specific test rig nor off-line mathematical manipulation

IPM synchronous machine drive response to symmetrical and asymmetrical short circuit faults

Copyright © 2003 IEEEA closed-form solution is presented for the steady-state response of interior permanent magnet (IPM) synchronous machines to symmetrical short circuits including the effects of q-axis magnetic saturation. Machine response to single-phase asymmetrical short circuits is also investigated. Experimental data are presented to verify predicted behavior for both types of short circuits. It is shown that single-phase asymmetrical short circuit faults produce more severe fault responses with high pulsating torque and a significant threat of rotor demagnetization. A control strategy that purposely transitions such faults into symmetrical three-phase short circuits can minimize the fault severity and associated demagnetization risks. Implications for the design of IPM machines with improved fault tolerance are discussed.Brian A. Welchko, Thomas M. Jahns, Wen L. Soong and James M. Nagashima

Impact of maximum back-EMF limits on the performance characteristics of interior permanent magnet synchronous machines

Interior permanent magnet (IPM) synchronous machines are vulnerable to uncontrolled generator (UCG) faults at high speed that can damage the inverter. One approach to reducing this risk is to impose limits on the maximum machine back-EMF voltage at top speed. This paper presents the results of a comparative design study that clarifies the nature and extent of the penalties imposed on the IPM machine metrics and performance characteristics as a result of imposing progressively tighter values of back-EMF voltage limits. As an alternative to limiting back-EMF and penalizing machine designs, this paper also investigates the effectiveness of the system-side protection approach to the same UCG fault problem.Seok-hee Han, Thomas M. Jahns, Metin Aydin, Mustafa K. Guven, Wen L. Soon

Surface PM machine parameter selection for wide field-weakening applications

Recent work on fractional-slot pitch, concentrated winding (FSCW) surface PM machines has shown that these machines can achieve a wide constant-power speed range. This paper shows that defining the allowable machine design parameter plane using the characteristic current and the peak back-emf provides useful insights into how application requirements restrict the machine parameters. The parameter plane also shows the influence of changing the parameters on the machine's current rating and magnet losses. As an example of a practical application, the parameter plane is used to study the FreedomCAR traction motor drive requirements and the characteristics of five FSCW surface PM machine designs.W.L. Soong, P.B. Reddy, A.M. El-Refaie, T.M. Jahns and N. Ertugru

Photosystem II core phosphorylation and photosynthetic acclimation require two different protein kinases

Illumination changes elicit modifications of thylakoid proteins and reorganization of the photosynthetic machinery. This involves, in the short term, phosphorylation of photosystem II (PSII) and light-harvesting (LHCII) proteins. PSII phosphorylation is thought to be relevant for PSII turnover1,2, whereas LHCII phosphorylation is associated with the relocation of LHCII and the redistribution of excitation energy (state transitions) between photosystems3,4. In the long term, imbalances in energy distribution between photosystems are counteracted by adjusting photosystem stoichiometry5,6. In the green alga Chlamydomonas and the plant Arabidopsis, state transitions require the orthologous protein kinases STT7 and STN7, respectively7,8. Here we show that in Arabidopsis a second protein kinase, STN8, is required for the quantitative phosphorylation of PSII core proteins. However, PSII activity under high-intensity light is affected only slightly in stn8 mutants, and D1 turnover is indistinguishable from the wild type, implying that reversible protein phosphorylation is not essential for PSII repair. Acclimation to changes in light quality is defective in stn7 but not in stn8 mutants, indicating that short-term and long-term photosynthetic adaptations are coupled. Therefore the phosphorylation of LHCII, or of an unknown substrate of STN7, is also crucial for the control of photosynthetic gene expressio

Design and experimental verification of a 50 kW interior permanent magnet synchronous machine

This paper presents the design details for an IPM machine designed to deliver 50 kW constant power over a 5:1 speed range extending from 850 rpm to 4250 rpm, with a gradual reduction in the required output power up to 8000 rpm (25 kW). Electromagnetic, thermal, and structural considerations have been included in the design optimization process. The resulting machine is designed with two magnet layers per pole and a distributed stator winding. Special features of the machine include its deep stator slots and four-layer winding, made necessary by the desire to minimize the machine's moment of inertia. Test results available to date demonstrate that the machine is capable of delivering the required output torque and power, and the agreement between the predicted and measured machine parameters is generally quite good. Calculated iron losses for high-speed flux-weakening operation are presented in the final section of the paper, illustrating the challenges associated with minimizing the impact of high-frequency harmonic flux density components.Jahns, T.M.; Seok-Hee Han; El-Refaie, A.M.; Jei-Hoon Baek; Aydin, M.; Guven, M.K.; Soong, W.L

Microlasers for photonic switching and interconnection

Vertical-cavity, surface-emitting lasers have great potential owing to their inherent two-dimensional geometry and very small gain nedium volumes which are essential to low threshold currents. Possible applications are optical switching/computing, photonic interconnection, high/low power laser sources, image processing, optical neural networks, etc. Driven by these high promises, there have been numerous reports on vertical cavity surface emitting laser diodes using InGaAs/GaAs/A1As, GaAs/AlGaAs structures. In this paper, we report characteristics of discrete InGaAs microlasers and monolithic two-dimensional arrays of microlasers. The advantages of optics for communications of data over distances longer than nearby gates have been argued previously. We proposed and demonstrated a photonic interconnect scheme using microlasers with planar optics which will be robust, accurate, and easily alignable

Relationship between food waste, diet quality, and environmental sustainability

Improving diet quality while simultaneously reducing environmental impact is a critical focus globally. Metrics linking diet quality and sustainability have typically focused on a limited suite of indicators, and have not included food waste. To address this important research gap, we examine the relationship between food waste, diet quality, nutrient waste, and multiple measures of sustainability: use of cropland, irrigation water, pesticides, and fertilizers. Data on food intake, food waste, and application rates of agricultural amendments were collected from diverse US government sources. Diet quality was assessed using the Healthy Eating Index-2015. A biophysical simulation model was used to estimate the amount of cropland associated with wasted food. This analysis finds that US consumers wasted 422g of food per person daily, with 30 million acres of cropland used to produce this food every year. This accounts for 30% of daily calories available for consumption, one-quarter of daily food (by weight) available for consumption, and 7% of annual cropland acreage. Higher quality diets were associated with greater amounts of food waste and greater amounts of wasted irrigation water and pesticides, but less cropland waste. This is largely due to fruits and vegetables, which are health-promoting and require small amounts of cropland, but require substantial amounts of agricultural inputs. These results suggest that simultaneous efforts to improve diet quality and reduce food waste are necessary. Increasing consumers’ knowledge about how to prepare and store fruits and vegetables will be one of the practical solutions to reducing food waste