scholarly journals Overhead Line Mechanics Taking the Influence of Wind into Account

10.14311/1642 ◽  
2012 ◽  
Vol 52 (5) ◽  
Author(s):  
Miroslav Müller
Keyword(s):  
Harmonic Component ◽  
Overhead Line ◽  
Step Size ◽  
Continuous Description ◽  
Spatial Coordinates ◽  
One Step ◽  
Catenary Curve ◽  
Harmonic Components ◽  
Dynamic Description ◽  
The Time Domain

This paper deals with problems of overhead line motion. The line model is based on a dynamic description of a catenary curve. The benefits of dynamic modeling in this field are decrypted, and there is an explanation of one of the models that is used. The dynamic model is derived from a string equation. The main contribution of the model is in 3D simulation of complex mechanics. The model of an overhead line shaking is generally based on the superposition of harmonic components, in particular the spatial coordinates. Each individual harmonic component is solved separately in one step of calculation, and is then combined with the other solutions. The result is a continuous description of the position of the wire along its length in both the space domain and the time domain. The model thus allows calculationsof uneven effects of forces along the length of an overhead line. The accuracy of the calculation is determined by the number of harmonics and other parameters that are calculated (e.g. step size, simulation time) The model is actually a combination of discrete and continuous calculations. Each model function block is described in the form of an equation. In the case study, ACSR 350/59 wire is analyzed. In this part of our work, an auxiliary model of wind influence was integrated into the global model.

THE FORWARD MAGNETOTELLURIC PROBLEM FOR AN INHOMOGENEOUS AND ANISOTROPIC STRUCTURE

Geophysics ◽  
1974 ◽  
Vol 39 (1) ◽  
pp. 56-68 ◽  
Author(s):  
Flavian Abramovici
Keyword(s):  
Three Dimensional ◽  
Middle Layer ◽  
Conductivity Tensor ◽  
Dimensional Structure ◽  
Impedance Tensor ◽  
Variable Step Size ◽  
Step Size ◽  
Variable Step ◽  
One Step ◽  
Numerical Integration Procedure

The impedance tensor corresponding to the magnetotelluric field for a nonisotropic one‐dimensional structure is given in terms of the solutions of a sixth‐order differential system. The conductivity tensor is three‐dimensional. Its components depend upon depth only in an arbitrary manner such that the corresponding matrix is positive definite. The impedance tensor components are found by a numerical integration procedure based on a set of one‐step methods and a variable step‐size to insure a given accuracy in the final result. Calculations were made for three models having sharp boundaries and also transitional layers. The first of these models has a middle layer of high conductivity, sandwiched between two layers of linearly varying conductivity, while in the second model the middle layer has a very low conductivity. In the third model the conductivity tensor is three‐dimensional and is linearly varying in one of the layers.

scholarly journals Mitigation Method of Slot Harmonic Cogging Torque Considering Unevenly Magnetized Permanent Magnets in PMSM

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3887
Author(s):  
Jeong ◽  
Lee ◽  
Hur
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnets ◽  
Permanent Magnet Synchronous Motor ◽  
Harmonic Component ◽  
Magnetic Flux Density ◽  
Element Analysis ◽  
Cogging Torque ◽  
Maxwell Stress Tensor ◽  
The Finite Element Analysis ◽  
Harmonic Components

This paper presents a mitigation method of slot harmonic cogging torque considering unevenly magnetized magnets in a permanent magnet synchronous motor. In previous studies, it has been confirmed that non-uniformly magnetized permanent magnets cause an unexpected increase of cogging torque because of additional slot harmonic components. However, these studies did not offer a countermeasure against it. First, in this study, the relationship between the residual magnetic flux density of the permanent magnet and the cogging torque is derived from the basic form of the Maxwell stress tensor equation. Second, the principle of the slot harmonic cogging torque generation is explained qualitatively, and the mitigation method of the slot harmonic component is proposed. Finally, the proposed method is verified with the finite element analysis and experimental results.

Development of lateral interactions in the infant visual system

1992 ◽  
Vol 8 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Samuel Sokol ◽  
Vance Zemon ◽  
Anne Moskowitz
Keyword(s):  
Visual System ◽  
Long Range ◽  
Short Range ◽  
Second Harmonic ◽  
Harmonic Component ◽  
Frequency Component ◽  
Human Infants ◽  
Long Range Interactions ◽  
Harmonic Components ◽  
Inhibitory Interactions

AbstractThe development of lateral inhibitory interactions in the infant visual system, as reflected by the visual-evoked potential (VEP), was studied using a radial, asymmetrical windmill-dartboard stimulus. This contrast-reversing stimulus generates VEP responses with a strong fundamental frequency component and an attenuated second harmonic component (relative to that obtained using a symmetrical stimulus). These two harmonic components reflect distinct phenomena, and appear to be the result of short-range (the fundamental) and long-range (attenuated second harmonic) lateral inhibitory interactions elicited by differential luminance-modulation of contiguous spatial regions. We studied the development of the short-and long-range interactions at 100% and 30% contrast in human infants using both VEP amplitude and phase measures. Attenuation of the second harmonic (long-range interactions) was adult-like by 8 weeks of age while the strength of the fundamental (short-range interactions) was adult-like by 20 weeks suggesting a differential development of long-range and short-range interactions. In contrast, corresponding phase data indicated significant immaturities at 20 weeks of age for both the short-and long-range components.

Statistical Correlation Between the Crankshaft’s Speed Variation and Engine Performance—Part I: Theoretical Model

2003 ◽  
Vol 125 (3) ◽  
pp. 791-796 ◽  
Author(s):  
D. Taraza
Keyword(s):  
Statistical Model ◽  
Statistical Approach ◽  
Harmonic Component ◽  
Engine Performance ◽  
Statistical Correlation ◽  
Gas Pressure ◽  
Operating Conditions ◽  
Crank Angle ◽  
The Mean ◽  
Harmonic Components

The goal of this two-part paper is to develop a methodology using the variation of the measured crankshaft speed to calculate the mean indicated pressure (MIP) of a multicylinder engine and to detect cylinders that are lower contributors to the total engine output. Both the gas pressure torque and the crankshaft’s speed are, under steady-state operating conditions, periodic functions of the crank angle and may be expressed by Fourier series. For the lower harmonic orders, the dynamic response of the crankshaft approaches the response of a rigid body and that makes it is possible to establish correlations between the amplitudes and phases of the corresponding harmonic orders of the crankshaft’s speed and of the gas pressure torque. The inherent cycle-to-cycle variation in the operation of the cylinders requires a statistical approach to the problem. The first part of the paper introduces the statistical model for a harmonic component of the gas pressure torque and determines the correlation between the amplitudes and phases of the harmonic components of the gas pressure torque and the MIP of the engine. In the second part of the paper the statistical model is used to calculate the MIP and to detect deficient cylinders in the operation of a six-cylinder four-stroke diesel engine.

Combined Effects of Both Axial Gap and Blade Count Ratio on the Unsteady Forces of a Steam Turbine Stage

2012 ◽  
Author(s):  
Tie Chen ◽  
Kush Patel ◽  
Peter Millington
Keyword(s):  
Linear Time ◽  
Harmonic Component ◽  
Correction Method ◽  
Combined Effects ◽  
Steam Turbines ◽  
Unsteady Forces ◽  
Count Ratio ◽  
Shape Correction ◽  
Time Marching ◽  
Harmonic Components

Rotating blades of steam turbines are subjected to unsteady forces due to the presence of both wakes and potential field from the upstream stationary blades. These forces are strongly influenced by both axial gap and blade count ratio. The combined effects of these parameters are studied for 120 scenarios covering the normal design space. The calculated unsteady forces are transformed into harmonic components using a Fourier transform. Each harmonic component is correlated to both axial gap and blade count ratio to provide guidance for preliminary blade design. This study uses an in-house non-linear time marching CFD code TF3D-VIB, which adopts a Shape Correction method to manage an arbitrary blade count ratio using a single passage. Consequently it is one-order more efficient than a conventional multiple passage method.

Improved Mayr Model of Electrical Arc Furnace to Analyse Harmonic

2011 ◽  
Vol 110-116 ◽  
pp. 1762-1766
Author(s):  
A.M. Zare Zadeh ◽  
R. Ghandehari
Keyword(s):  
Power Quality ◽  
Time Domain ◽  
Arc Furnace ◽  
Negative Effects ◽  
The Real ◽  
Electrical Arc ◽  
Real Behavior ◽  
Voltage Flicker ◽  
Harmonic Components ◽  
The Time Domain

Voltage flicker and harmonics are power quality problems which are imposed on power system by electrical arc furnace. To study furnaces and find a solution to remove the negative effects of them, it is needed to have an appropriate electrical arc furnace model. Several methods in time and frequency domain have been presented. One of the time domain methods is Mayr model which has two problems. Firstly, it shows the harmonic components more than the real values. Secondly, it does not involve voltage flicker phenomenon. In this article with the comparison of harmonic components of Mayr model and measured values of arc furnace, an improved Mayr model is introduced. In the presented model, the problems of Mayr model are removed and it shows the real behavior of arc furnace

scholarly journals Accelerated Runge-Kutta Methods

2008 ◽  
Vol 2008 ◽  
pp. 1-38 ◽  
Author(s):  
Firdaus E. Udwadia ◽  
Artin Farahani
Keyword(s):  
Computationally Efficient ◽  
Step Size ◽  
Time Step ◽  
Integration Schemes ◽  
Local Accuracy ◽  
Numerical Integrators ◽  
One Step ◽  
Runge Kutta ◽  
Finite Step ◽  
Proof Of Convergence

Standard Runge-Kutta methods are explicit, one-step, and generally constant step-size numerical integrators for the solution of initial value problems. Such integration schemes of orders 3, 4, and 5 require 3, 4, and 6 function evaluations per time step of integration, respectively. In this paper, we propose a set of simple, explicit, and constant step-size Accerelated-Runge-Kutta methods that are two-step in nature. For orders 3, 4, and 5, they require only 2, 3, and 5 function evaluations per time step, respectively. Therefore, they are more computationally efficient at achieving the same order of local accuracy. We present here the derivation and optimization of these accelerated integration methods. We include the proof of convergence and stability under certain conditions as well as stability regions for finite step sizes. Several numerical examples are provided to illustrate the accuracy, stability, and efficiency of the proposed methods in comparison with standard Runge-Kutta methods.

Developing a Generalized Harmonic Balance Method for Accurate Identification of Crack Depth in a Continuous Shaft-Disc System

2015 ◽  
Author(s):  
Hamid Khorrami ◽  
Ramin Sedaghati ◽  
Subhash Rakheja
Keyword(s):  
Harmonic Balance ◽  
Crack Detection ◽  
Crack Depth ◽  
Harmonic Component ◽  
Harmonic Balance Method ◽  
Balance Method ◽  
Vibrational Properties ◽  
Accurate Identification ◽  
Harmonic Components ◽  
Generalized Harmonic Balance Method

In this work, the effect of a crack on the vibrational properties of a shaft-disc system has been studied applying a generalized harmonic balance method. In the reviewed literature, the reported methods to find the unbalance response of a continuous shaft-disc system provide only the first harmonic component of the response; whereas, the presented method gives the super-harmonic components as well. The shaft-disk system consists of a flexible shaft with a single rigid disc mounted on rigid short bearing supports. The shaft contains a transverse breathing crack (fatigue crack). The main concept for crack detection in vibration-based methods is basically the investigation of crack-induced changes in the selected vibrational properties. Shaft critical speeds and harmonic and super-harmonic components of the unbalance lateral response have been used as typical vibrational properties for crack detection in a rotating shaft system. A generalized harmonic balance method has been developed to efficiently investigate changes in vibrational properties due to the effect of crack properties, depth and location. The results of the developed analytical model have been compared with those obtained from the finite element model and close agreement has been observed.

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