Microtransformers for Teaching and System Stability Research

1986 ◽  
Vol 23 (2) ◽  
pp. 121-125
Author(s):  
P. H. G. Allen ◽  
K. J. D'Souza
Keyword(s):  
Single Phase ◽  
Second Order ◽  
System Stability ◽  
Rotating Machines ◽  
Linear Features ◽  
Three Phase ◽  
Non Linear ◽  
Design And Manufacture

Large transformers, like highly rated rotating machines, can be modelled in ‘micro’ form to demonstrate significant second order, non-linear, features. The design and manufacture of 3 kVA (nominal) rating three-phase and three single-phase transformer bank units, all with three-limb cores and 0.17 per unit leakage reactance are described.

scholarly journals Effect of load current harmonics on vibration of three-phase generator

2018 ◽  
Vol 197 ◽  
pp. 11023
Author(s):  
I Made Wiwit Kastawan
Keyword(s):  
Single Phase ◽  
Electrical Power ◽  
Electrical Power System ◽  
Negative Effects ◽  
Load Current ◽  
Current Harmonics ◽  
Three Phase ◽  
Non Linear ◽  
Electrical Loads ◽  
Linear Loading

Almost all today electrical loads are considered non-linear such as switch mode power supply (SMPS) for powering computer and mobile phone or variable speed drive (VSD) for driving home and industrial electric motors. These loads generate ac non-sinusoidal current containing a lot of harmonics as indicated by its high total harmonics distortion (THD) figure. Current harmonics bring negative effects into all electrical power system components, including three-phase generator. This paper provides analysis of load current harmonics effects on vibration of three-phase generator. Three different laboratory experiments have been conducted i.e. three-phase linear resistive loading, non-linear loading with a three-phase ac/dc converter and non-linear loading with three single-phase capacitor filtered ac/dc converters. Results show that the higher load current harmonics content the higher is vibration of the three-phase generator. Non-linear loading with a three-phase ac/dc converter that generate about 24.7% THD gives an increase of 4.3% and 5.5% in average of vertical and horizontal vibrations of the three-phase generator respectively. Further, non-linear loading with three single-phase capacitor filtered ac/dc converters that generate THD as high as 74.9% gives significant increase of 28.1% and 23.6% in average of vertical and horizontal vibrations respectively.

scholarly journals Power Quality Improvement using UPQC with Single and Three-Phase Non-linear Loads in Countryside Areas

2019 ◽  
Vol 9 (4) ◽  
pp. 18-24
Author(s):  
Shuchi Vishnoi ◽  
Keyword(s):  
Power Quality ◽  
Distribution System ◽  
Single Phase ◽  
Phase Distribution ◽  
Control Strategies ◽  
Electrical Power ◽  
Synchronous Reference Frame ◽  
Three Phase ◽  
Non Linear ◽  
Distribution Grids

This paper is intended to simulate a power quality conditioning device, Unified Power Quality Conditioner (UPQC), in countryside areas for non-linear loading. From past decades there is much increase in the requirement of the good quality electrical power in single phase distribution grids established in these locations. Due to technical advancement, three-phase loads are practiced more than single phase loads so that the demand for three phase distribution grids is growing. But the installation process of three-phase grids, at countryside areas, is not an economic option and to get access to these systems is a very challenging task. So a neighbouring three-phase distribution system is required to be established at the location, where single-phase to three-phase UPQC with single wire earth return is appropriate for the end user due to economic considerations. A dual compensation strategy is implemented to obtain the reference quantities for controlling the converters. The proposed idea is accomplished to eliminate voltage harmonics and mitigate further instabilities and power quality problems. This system allows the balanced and regulated voltage with lower harmonic content. Synchronous Reference Frame (SRF) based controllers are considered to organize the input grid current and the load voltages of the UPQC. The present prototype under consideration analyses and validates the compensation and controlling techniques using PI controller. The control strategies are simulated using MATLAB/SIMULINK.

Localizing Unbalance Faults in Rotating Machinery

2013 ◽  
Author(s):  
R. B. Walker ◽  
S. Perinpanayagam ◽  
I. K. Jennions
Keyword(s):  
Frequency Domain ◽  
Health Management ◽  
Sensor Placement ◽  
Rotating Machinery ◽  
Next Generation ◽  
Rotating Machines ◽  
Linear Features ◽  
Rotating Machine ◽  
Rules Of Thumb ◽  
Non Linear

Excessive levels of unbalance in rotating machinery continue to contribute to machine downtime and unscheduled and costly maintenance actions. Whilst unbalance as a rotordynamic fault has been studied in great detail during the last century, the localization of unbalance within a complex rotating machine is today often performed in practice using little more than ‘rules of thumb’. In this work, localizing excessive unbalance has been studied from an experimental perspective through the use of two rotordynamic test rigs fitted with multiple disks. Sub-synchronous non-linear features in the frequency domain have been identified and studied as a method of aiding the localization of unbalance faults, particularly in situations where sensor placement options are limited. The results of the study are discussed from the perspective of next-generation Integrated Vehicle Health Management (IVHM) systems for rotating machines.

A Control of Homeostasis for Three-Phase Load in Power System

2014 ◽  
Vol 521 ◽  
pp. 298-302
Author(s):  
Wei Zhao Gao ◽  
Qing Chao Zhang ◽  
Ming Zhong Zheng ◽  
Heng Chao Zhang
Keyword(s):  
Power System ◽  
Single Phase ◽  
Reactive Power ◽  
Neutral Current ◽  
Reactive Power Compensation ◽  
New Method ◽  
System Stability ◽  
Stable Operation ◽  
A Value ◽  
Three Phase

With the increasing asymmetry of the three-phase load, the problem of three-phase imbalance in power system is becoming more serious every day. Asymmetrical three-phase voltages and currents affect the safe and stable operation of the power system.The main direction for solving the problem of unbalanced three-phase power system is reactive power compensation. But in present paper, we demonstrate a new method. First, we load the single-phase load into the phase with smallest current and keep oscillation. Then, considering that system stability requires as small as possible imbalance, so we treat line current as criterion and adjust part load into system phases to reduce the neutral current to a value less action. Thus we can achieve homeostasis of three-phase load. We also have realized it by simulation.

Three-phase to Single-phase Matrix Converter for Improvement of Three-phase Voltage Unbalance in Distribution System

2015 ◽  
Vol 135 (3) ◽  
pp. 168-180 ◽  
Author(s):  
Ryota Mizutani ◽  
Hirotaka Koizumi ◽  
Kentaro Hirose ◽  
Kazunari Ishibashi
Keyword(s):  
Distribution System ◽  
Single Phase ◽  
Matrix Converter ◽  
Phase Voltage ◽  
Voltage Unbalance ◽  
Three Phase

First and Second Order Elastoplastic Analyses of Thin-Walled Metal Members using Generalized Beam Theory

2018 ◽  
Author(s):  
Miguel Abambres
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Cross Section ◽  
Beam Theory ◽  
Second Order ◽  
Flow Rule ◽  
Non Linear ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Generalized Beam Theory

Original Generalized Beam Theory (GBT) formulations for elastoplastic first and second order (postbuckling) analyses of thin-walled members are proposed, based on the J2 theory with associated flow rule, and valid for (i) arbitrary residual stress and geometric imperfection distributions, (ii) non-linear isotropic materials (e.g., carbon/stainless steel), and (iii) arbitrary deformation patterns (e.g., global, local, distortional, shear). The cross-section analysis is based on the formulation by Silva (2013), but adopts five types of nodal degrees of freedom (d.o.f.) – one of them (warping rotation) is an innovation of present work and allows the use of cubic polynomials (instead of linear functions) to approximate the warping profiles in each sub-plate. The formulations are validated by presenting various illustrative examples involving beams and columns characterized by several cross-section types (open, closed, (un) branched), materials (bi-linear or non-linear – e.g., stainless steel) and boundary conditions. The GBT results (equilibrium paths, stress/displacement distributions and collapse mechanisms) are validated by comparison with those obtained from shell finite element analyses. It is observed that the results are globally very similar with only 9% and 21% (1st and 2nd order) of the d.o.f. numbers required by the shell finite element models. Moreover, the GBT unique modal nature is highlighted by means of modal participation diagrams and amplitude functions, as well as analyses based on different deformation mode sets, providing an in-depth insight on the member behavioural mechanics in both elastic and inelastic regimes.

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