Investigation of Dynamic Loads in Wind Turbine Drive Trains Due to Grid and Power Converter Faults

Electrical faults can lead to transient and dynamic excitations of the electromagnetic generator torque in wind turbines. The fast changes in the generator torque lead to load oscillations and rapid changes in the speed of rotation. The combination of dynamic load reversals and changing rotational speeds can be detrimental to gearbox components. This paper shows, via simulation, that the smearing risk increases due to the electrical faults for cylindrical roller bearings on the high speed shaft of a wind turbine research nacelle. A grid fault was examined for the research nacelle with a doubly fed induction generator concept. Furthermore, a converter fault was analyzed for the full size converter concept. Both wind turbine grid connection concepts used the same mechanical drive train. Thus, the mechanical component loading was comparable. During the grid fault, the risk of smearing increased momentarily by a maximum of around 1.8 times. During the converter fault, the risk of smearing increased by around 4.9 times. Subsequently, electrical faults increased the risk of damage to the wind turbine gearbox bearings, especially on the high speed stage.

Opportunities and Challenges in Converting Existing Natural Gas Infrastructure for Hydrogen Operation

Hydrogen holds enormous potential in helping the world achieve its decarbonization goals and is set to play a key role in the Energy Transition. However, two central building blocks are needed to make the hydrogen economy a reality: 1) a sufficient source of emissions-free (i.e., blue or green) hydrogen production and 2) a needs-based transportation and storage network that can reliably and cost-effectively supply hydrogen to end-users. Given the high costs associated with developing new transportation infrastructure, many governments, pipeline operators, and regulatory bodies have begun exploring if it is both possible and economical to convert existing natural gas (i.e., methane) infrastructure for hydrogen operation. This paper outlines opportunities and technical challenges associated with such an endeavor – with a particular focus on adaptation requirements for rotating equipment/compressor drive trains and metallurgical and integrity considerations for pipelines.

Tool wear development in gear skiving process of quenched and tempered internal gears

Gear skiving is a highly productive machining process, especially for manufacturing of high strength internal gears as required for high performance electric drive trains. However, the complex process kinematics cause intense variations of the effective cutting parameters during tool engagement. Thus, particularly the tool must meet high requirements to achieve long tool life at required workpiece quality. These requirements are amplified even more when machining quenched and tempered materials from the massive blank.In the presented study, the influence of various key factors on the tool wear development in gear skiving process are quantified. In several tests, the cutting speed, workpiece tensile strength, cooling lubricant strategy, as well as the cutting strategy are varied in order to optimize tool life. Therefore, single-tooth tests on quenched and tempered internal gears from 31CrMoV9 (AISI 4340) steel are conducted and wear flank land width evolution of the tools is examined. In addition, the workpiece is evaluated with regard to surface quality. Results reveal that different factor level combinations can have various effects on tool wear characteristics and therefore on tool life. The correlations presented provide recommendations for practical application and contribute to deeper process understanding.

Operating Behavior of Sliding Planet Gear Bearings for Wind Turbine Gearbox Applications—Part II: Impact of Structure Deformation

The use of planetary gear stages intends to increase power density in drive trains of rotating machinery. Due to lightweight requirements on this type of machine elements, structures are comparably flexible while mechanical loads are high. This study investigates the impact of structure deformation on sliding planet gear bearings applied in the planetary stages of wind turbine gearboxes with helical gears. It focuses on three main objectives: (i) development of a procedure for the time-efficient thermo-elasto-hydrodynamic (TEHD) analysis of sliding planet gear bearing; (ii) understanding of the specific deformation characteristics of this application; (iii) investigation of the planet gear bearing’s modified operating behavior, caused by the deformation of the sliding surfaces. Generally, results indicate an improvement of predicted operating conditions by consideration of structure deformation in the bearing analysis for this application. Peak load in the bearing decreases because the loaded proportion of the sliding surface increases. Moreover, tendencies of single design measures, determined for rigid geometries, keep valid but exhibit significantly different magnitudes under consideration of structure deformation. Results show that consideration of structure flexibility is essential for sliding planet gear bearing analysis if quantitative assertions on load distributions, wear phenomena, and interaction of the bearing with other components are required.

Evaluation of ventricular tachycardia inducibility after implementation of a standardized programmed ventricular stimulation protocol in patients with repaired Tetralogy of Fallot

Introduction The electrophysiologic (EP) evaluation with programmed electrical stimulation (PVS) is generally recommended in patients with repaired Tetralogy of Fallot and additional risk factors for sudden cardiac death. Nevertheless, different PVS protocols have been described. The aim of our study was to evaluate the differences in ventricular tachycardia (VT) inducibility of patients with TOF after the implementation of a standard PVS protocol in the EP laboratory of a Congenital Heart Disease reference center. Methods All patients with repaired TOF who underwent an EP study with PVS between January 2001 and October 2020 were included. The new standardized PVS protocol was performed in 2 ventricular sites (apex and outflow tract) with 3 drive trains (cycle lengths 400, 500 and 600ms) and up to 3 extrastimuli. In absence of VT induction, the protocol was repeated under isoprenaline infusion. This new protocol was implemented since January 2012. Non protocolized PVS studies before 2012 were defined as “Non-standardized”. Baseline clinical information about symptoms and previous arrhythmias was recorded as well as electrocardiogram, echocardiogram and cardiac MRI parameters. Finally, the follow-up events (ICD implantation, sudden cardiac death, global mortality, arrythmias and ICD therapies) were also retrospective recorded. Results A total of 154 EP studies with PVS were performed in 128 patients with repaired TOF. 31 of them were performed before the 1st January 2012 (non-standardized PVS) and 112 were performed with the new standardized protocol. The median follow-up was 6,5 years. Both groups had similar baseline characteristics except LVEF and RVEF, that were lower in the “Non-standardized PVS” group. There were no differences between the ventricular tachycardia inducibility of both protocols (22,3% vs 33,3%; p=0,162). The risk factors for VT inducibility were the QRS length (184,46ms vs 169,34 ms; p=0,038), the RVEF (36,25% vs 43,79; p=0,0007), the presence of ventricular ectopia (VE) (38,5% vs 20,0%; p=0,024) and previous VT (35,9% vs 13,9%; p=0,003). VT induction during EP study was related with ICD implantation (71,8% vs 21,7%, p≤0,001), VT (30,8% vs 20%, p<0,001) and all kind of arrythmias (VT, non-sustained VT, VE and auricular flutter) (41% vs 21,7%, p=0,005) during follow-up. A total of 6 deaths (1 in the group with induced VT and 5 in the group with non-induced VT) were recorded. Conclusions The implementation of a standardized and more complete PVS protocol in patients with repaired TOF has not shown differences in the experience of our center. The risk factors for VT inducibility were the QRS length, the RVEF, the presence of ventricular ectopia and previous VT, which have also been reported as risk factors for sudden cardiac death in previous studies. The presence of VT induction entailed more ICD implantation and more arrythmias at follow-up. FUNDunding Acknowledgement Type of funding sources: None.

A Comparative Analysis of Power Consumption in Conventional and Differential – Less Drive for Electric Vehicle

The general design of the methodology of the transmission system is usually used to give efficient power to the driven wheel, such as usually used differential to differentiate speed and motion of the wheel. In this paper; we analyze methods of motion control and power transmission variation for an electric vehicle (EV) with two independently driven in-wheel motors and conventional differential used EV. Compares the power transmission ratio of two different configurations drives energy conversion differential and epicyclic gears train analysis. This investigation gives an orderly examination of compendium an electrical vehicle is driven by transmissions system journals published and about different losses through mechanical differential system transmission and how they affect on torque. These studies present a comprehensive convergent study report of power Variation and torque transmission with simulation result distinction in differential and differential-less EV’s by compendium studies and show some comparative results. After a compendium study author finds few losses in differentials such as Pocketing power losses, WPL, drag mishap, friction, and different slip in gears. We have mention different factors also affect drive trains and illustrate the main reason to generate losses during transmission. In addition, we have explained this through simulation.

Effects of Different Hard Finishing Processes on Gear Excitation

Gearboxes are essential in mechanical drive trains for power transmission. A low noise emission and thus an optimized excitation behavior is a substantial design objective for many applications in terms of comfort and operational safety. There exist numerous processes for manufacturing gears, which all show different properties in relation to the process variables and, therefore, differences in the resulting accuracy and quality of the gear flank. In this paper, the influence of three different manufacturing processes for hard finishing—continuous generating grinding, polish grinding and gear skiving—on the surface structure of gear flanks and the excitation behavior is investigated experimentally and analyzed by the application force level. A tactile scanning of the gear flanks determines the flank surface structure and the deviations from the desired geometry. A torsional acceleration measurement during speed ramp-ups at different load levels is used to analyze the excitation of the gears. The results show only a minor influence of the surface structure on the application force level. The excitation behavior is dominated by the influence of the flank modification and its deviation from the design values.

Low excitation spur gears with variable tip diameter

One important source of noise in drive trains are transmissions. In numerous applications, it is necessary to use helical instead of spur gear stages due to increased noise requirements. Besides a superior excitation behaviour, helical gears also show additional disadvantageous effects (e.g. axial forces and tilting moments), which have to be taken into account in the design process. Thus, a low noise spur gear stage could simplify design and meet the requirements of modern mechanical drive trains. The authors explore the possibility of combining the low noise properties of helical gears with the advantageous mechanical properties of spur gears by using spur gears with variable tip diameter along the tooth width. This allows the adjustment of the total length of active lines of action at the beginning and end of contact and acts as a mesh stiffness modification. For this reason, several spur gear designs are experimentally investigated and compared with regard to their excitation behaviour. The experiments are performed on a back-to-back test rig and include quasi-static transmission error measurements under load as well as dynamic torsional vibration measurements. The results show a significant improvement of the excitation behaviour for spur gears with variable tip diameter.