Analytical study on discharge process of multiphase air-core pulsed alternators

2021 ◽  
Author(s):  
Ying Zhang ◽  
Xuhui Wen ◽  
Wenchao Li ◽  
Jialin Wei ◽  
Xiaofeng Zhang ◽  
...  
Keyword(s):  
Finite Element ◽  
Short Circuit ◽  
Current Model ◽  
Short Circuit Current ◽  
Element Model ◽  
State Equation ◽  
Equation Model ◽  
The State ◽  
Discharge Process ◽  
Air Core

Abstract This paper has investigated the discharge process of a four-phase air-core pulsed alternator. A mathematical model of the short-circuit current, relating to firing angles of discharge thyristors and taking the current coupling and field current attenuation into account, is established. Compared with the conventional trial-and-error method and existing phase peak current model, the proposed model has considered the attenuation trend of the filed current in the discharge process and derived the intuitive expression of the resultant short-circuit current. Firstly, the state equation model of a four-phase air-core pulsed alternator is established. Meanwhile, the simulation comparison indicates that the results of the state equation model are close to the finite-element model. Then, the segmented formula of resultant short-circuit current is derived based on the voltage equations of the armature winding circuits and the approximate attenuation coefficient of the field current. Finally, the segmented formula is verified with the finite-element method, and some preliminary experiments for field windings are carried out. The results show that this method can well describe the decay trend of field current and discharge current. It is helpful for selecting firing angles to generate the desired current amplitude and waveform in the future.

Investigation on the shaft voltage generation of large synchronous turboalternators

2020 ◽  
Vol 39 (5) ◽  
pp. 1145-1156
Author(s):  
Kevin Darques ◽  
Abdelmounaïm Tounzi ◽  
Yvonnick Le-menach ◽  
Karim Beddek
Keyword(s):  
Finite Element ◽  
Design Methodology ◽  
Short Circuit ◽  
Element Model ◽  
Stator Winding ◽  
Content Type ◽  
Voltage Generation ◽  
The Impact ◽  
Investigation Process ◽  
Circulating Currents

Purpose This paper aims to go deeper on the analysis of the shaft voltage of large turbogenerators. The main interest of this study is the investigation process developed. Design/methodology/approach The analysis of the shaft voltage because of several defects is based on a two-dimensional (2D) finite element modeling. This 2D finite element model is used to determine the shaft voltage because of eccentricities or rotor short-circuit. Findings Dynamic eccentricities and rotor short circuit do not have an inherent impact on the shaft voltage. Circulating currents in the stator winding because of defects impact the shaft voltage. Originality/value The original value of this paper is the investigation process developed. This study proposes to quantify the impact of a smooth stator and then to explore the contribution of the real stator winding on the shaft voltage.

scholarly journals Electrothermal Modeling and Analysis of Gallium Oxide Power Switching Devices

2019 ◽  
Author(s):  
Ramchandra M. Kotecha ◽  
Andriy Zakutayev ◽  
Wyatt K. Metzger ◽  
Paul Paret ◽  
Gilberto Moreno ◽  
...  
Keyword(s):  
Finite Element ◽  
Power Electronics ◽  
Gallium Oxide ◽  
Short Circuit ◽  
Thermal Characteristics ◽  
Wide Band ◽  
Element Model ◽  
Oxide Semiconductor ◽  
Modeling And Analysis ◽  
Device Architecture

Abstract Gallium oxide is an emerging wide band-gap material that has the potential to penetrate the power electronics market in the near future. In this paper, a finite-element gallium oxide semiconductor model is presented that can predict the electrical and thermal characteristics of the device. The finite element model of the two-dimensional device architecture is developed inside the Sentaurus environment. A vertical FinFET device architecture is employed to assess the device’s behavior and its static and dynamic characteristics. Enhancement-mode device operation is realized with this type of device architecture without the need for any selective area doping. The dynamic thermal behavior of the device is characterized through its short-circuit behavior. Based on the device static and dynamic behavior, it is envisioned that reliable vertical transistors can be fabricated for the power electronics applications.

Thermal Effects on the Anchoring of Flexible Pipe Tensile Armors

2015 ◽  
Author(s):  
Olaf O. Otte Filho ◽  
Rafael L. Tanaka ◽  
Rafael G. Morini ◽  
Rafael N. Torres ◽  
Thamise S. V. Vilela
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Thermal Effects ◽  
Current Model ◽  
Element Model ◽  
Small Scale ◽  
Flexible Pipe ◽  
System A ◽  
Flexible Pipes ◽  
Better Than

In the design of flexible pipes, predict the anchoring behavior on end fittings is always challenging. In this sense, Prysmian Surflex has developed a finite element model, which should help the end fitting design as well the prediction of the structural behavior and the acceptable maximum loads. The current model considers that the contact between armor-resin is purely cohesive and has been suitable for the design of end fittings [1] and [2]. But tests and new studies [3] and [4] indicate that only cohesive assumption would not be the best approach. Experimental data from prototype tests also show that the current model would not predict acceptable results for loads higher than those used in previous projects. This document will describe a study developed considering the friction and thermal contraction, instead of the cohesive phenomenon in the anchoring behavior analysis. Small scale tests were conducted in order to understand the anchoring relation between the resin and the wire used in the tensile armor. For this purpose, a special test device was developed to simulate an enclosure system. A parametric study was also performed to identify the cooling temperatures, coefficients of friction and contact properties parameters taken from small scale tests. The finite element model considers the thermal effects during exothermic curing. Using the new parameters obtained, a second model was developed. This model consists of only one real shaped bended wire inside an end fitting cavity. To validate the model, samples were tested on laboratory according anchoring design. The results of this round of tests were studied and corroborate the argument that use friction and thermal effects is better than use only the cohesive condition.

Torsional axisymmetric finite element model for problems in elasticity

1986 ◽  
Vol 13 (5) ◽  
pp. 583-587
Author(s):  
Ming G. Lau
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Displacement Function ◽  
Infinite Medium ◽  
The State ◽  
Tangential Displacement ◽  
Shear Stresses ◽  
Pure Torsion ◽  
Typical Application ◽  
The Third

This note describes how the displacements and shear stresses of an axisymmetric elastic component, when loaded in torsion, can be computed by modelling the component with torsional axisymmetric finite elements. The model developed represents only minor modifications of the well-known plane stress or plane strain finite element technique.In the analysis, the model is split into a mesh of triangular annuli. Each node of each element has only one degree of freedom, the tangential displacement. The state of strain in each element is represented by a three-term displacement function, one representing a rigid body rotation, the second representing the state of torsion, and the third representing the state of strain in a hollow thin disc.The model has been applied satisfactorily to three torsional problems with known theoretical solutions. The first problem involves the computation of torsional shear stresses of a uniform shaft subjected to pure torsion. In the second problem, the solution is obtained for a conical shaft. In the third problem, known as the Reissner–Sagoci problem, an elastic semi-infinite medium is subjected to a torsional displacement on a small area of the surface.A typical application of the model to the problem of a shrink-fitted assembly subjected to torsion is discussed. Key words: torsion, finite element, elasticity, axisymmetry.

scholarly journals COST EFFECTIVE METHOD FOR THE STUDY OF THE SHORT-CIRCUIT BEHAVIOUR OF AN ELECTRICAL RESISTOR

10.6036/9802 ◽  
2021 ◽  
Vol 96 (3) ◽  
pp. 242-245
Author(s):  
DAVID GARCÍA MENÉNDEZ ◽  
CARLOS LUMBRERAS IGLESIAS ◽  
MARIO ALONSO MENÉNDEZ ◽  
ROBERTO SUAREZ SIERRA
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Systems ◽  
Thermal Stresses ◽  
Short Circuit ◽  
Cost Effective ◽  
Short Circuit Current ◽  
Power Grids ◽  
Element Analysis ◽  
Current Reduction

Electrical resistors for power lines are used worldwide as Neutral Earthing Resistors for short-circuit current reduction in power grids, and also as Filtering Resistors in combination with capacitors and inductances. The manufacturers of such resistors must certificate that they withstand the mechanical and thermal stresses imposed by the external loads, in accordance with IEC 62001 standard. Although this certification can be achieved by means of testing the resistor under working conditions, this process is both expensive and time-consuming. In this paper it is proposed a methodology for simulating the thermal and mechanical behavior of an electrical resistor, based on Multiphysics Finite Element Analysis. The methodology has been applied for the analysis of a filtering resistor for the Ethiopia-Kenia Power Systems Interconnection. Keywords: Earthing and Filtering Resistor, Multiphysics Finite Element Analysis, IEC 62001 short-circuit behavior.

Improvement of a Reduced Torsional Model by Means of Parameter Identification

1989 ◽  
Vol 111 (1) ◽  
pp. 17-26 ◽  
Author(s):  
P. Schwibinger ◽  
R. Nordmann
Keyword(s):  
Finite Element ◽  
Mechanical Model ◽  
Degrees Of Freedom ◽  
Short Circuit ◽  
Original System ◽  
Element Model ◽  
The Finite Element Method ◽  
System A ◽  
Reduction Methods ◽  
Short Circuits

Turbogenerator sets in operation may be excited to transient torsional vibrations by dynamic electrical moments at the generator due to short-circuits or faulty synchronization. For the solution of the torsional vibration problem it is essential to find an appropriate torsional model of the original system. A common approach is to model the torsional system finely by the finite element method which normally results in a very accurate mechanical model with many degrees of freedom (DOF). However for some applications it is desirable to have a torsional model with a reduced number of DOF which reproduces the original system exactly only in the lower eigenfrequencies and modes. This paper describes a method which allows finding a most accurate reduced torsional model with discrete masses and springs from a finite element model with many DOF. The results for the eigenfrequencies, the modes, and internal moments due to a short-circuit excitation of a 600 MW turbogenerator set are presented. They are compared with other reduction methods.

Short-circuit current model of organic solar cells

2014 ◽  
Vol 614 ◽  
pp. 27-30 ◽  
Author(s):  
Nianduan Lu ◽  
Ling Li ◽  
Pengxiao Sun ◽  
Ming Liu
Keyword(s):  
Solar Cells ◽  
Organic Solar Cells ◽  
Short Circuit ◽  
Current Model ◽  
Short Circuit Current
Sign in / Sign up

Export Citation Format

Share Document