Reflectance spectra of Mesosiderites: Implications for asteroid 4 Vesta

Oxygen isotopic data argues that HEDs and mesosiderites may be from the same parent body. A spectral survey of mesosiderites was done to determine their spectral properties in the visible and near-infrared and compare to HEDs

Question words in pidgin and creole languages

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Reflexives

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Introduction

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Introduction : Problems in the identification of substratum features in the creole languages

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Conclusions

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Impact of wind conditions on thermal loading of PMSG wind turbine power converters

Power converter reliability is critical for permanent magnet synchronous generator (PMSG) wind turbines. Converter failures are linked to power module thermal loading but studies often neglect turbine dynamics, control and the impact of wind speed sampling rate on lifetime estimation. This paper addresses this using a 2MW direct-drive PMSG wind turbine model with a 2-level converter, and simulating junction temperatures (Tj) using a power module thermal equivalent circuit under various synthetic wind speed conditions. These synthetic wind conditions include constant and square wave profiles representing stable and gusty wind conditions. Responses to square wave wind speeds showed that the lower the gust frequency, the higher ∆Tj becomes, demonstrating that low turbulence sites have greater thermal variation in the converter. In contrast, wind speed variations with frequencies greater than 0.25Hz deliver only small increases in ∆Tj . It is concluded that reasonable approximations of Tj profiles can be made with 0.25Hz wind speed data, but that lower data rate wind measurements miss essential, damaging characteristics

Experimental Set-up for Applying Wind Turbine Operating Profiles to the Nacelle Power Converter

Studies have shown that the reliability of fully rated converters (FRC) in permanent magnet synchronous generator (PMSG) wind turbines is critical. This paper outlines an experimental rig that applies PMSG wind turbine specific operating profiles to a machine side converter (MSC) power module. A number of test regimes have been designed to verify thermal models of the power module, validate the use of cycle life vs. Tj profile manufacturing data, and determine the wind turbine operational profiles that cause the most damage to the MSC