The Role of Dissolved and Nascent Air in Oil-Hydraulic Systems

2000 ◽  
Author(s):  
Hansjoerg Stern
Keyword(s):  
Steady State ◽  
High Performance ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Phase System ◽  
Hydraulic Systems ◽  
Three Phase ◽  
Significant Damage ◽  
Water Hydraulic

Abstract In modern, high performance hydraulic systems the transient behavior of dissolving, dissolved and nascent air under changing dynamic conditions of pressure and temperature is emerging as an increasingly important factor, capable of creating undesirable operating conditions. The paper discusses the question of how to predict the performance of pump inlets and valve discharges, where we have known for some time that cavitation and cavitation-like conditions exist and can cause significant damage. The steady state conditions at which nascent air evolves from saturated air-in-oil solutions is normally one or two orders of magnitude above the vapor pressure of the system fluid. To what extent, therefore, is “cavitation” in these systems an air-oil problem? Or is it an oil-vapor problem that is analogous to cavitation in water hydraulic pumps and turbines? Or have we created the combination of the two, a three-phase system of liquid, gas and vapor?

The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture

1981 ◽  
Vol 103 (2) ◽  
pp. 193-242 ◽  
Author(s):  
E. M. Greitzer
Keyword(s):  
Steady State ◽  
Dynamic Instability ◽  
Transient Behavior ◽  
Operating Conditions ◽  
System Stability ◽  
Hydraulic Systems ◽  
Two Phase ◽  
Pumping System ◽  
Basic Concepts ◽  
Steady State Performance

A review is presented of the types of instabilities which are encountered in pumping systems of technological interest. These include axial and centrifugal compression systems, pumping systems involving cavitation, systems with two-phase flow, systems with combustion, hydraulic systems, and systems which have two or more pumping elements in parallel. All of the above will be seen to exhibit instabilities under certain operating conditions, although the mechanism of instability, as well as the particular system element that is responsible for the instability, will be quite different in the different systems. However, several basic concepts, such as the idea of negative damping which is associated with dynamic instability, will be seen to be common to the different systems. The review is organized around the different types of systems that are discussed, and includes descriptions of the steady-state performance, the regimes in which one would expect instability, and the mechanisms of instability. An idealized pumping system is first examined to illustrate some of the basic concepts. More realistic systems are then treated in the same manner of showing steady-state performance, regimes of instability and mechanisms. In the review attention is given mainly to those areas in which there is high current engineering interest, and an attempt is made to describe those areas of research which can be most fruitfully pursued. In general, it is suggested that efforts should be directed toward obtaining an improved understanding of the transient behavior of the active (instability causing) elements within the system, since it is lack of knowledge of this aspect that currently limits the accuracy of system stability predictions.

scholarly journals Muscle: A Three Phase System

1959 ◽  
Vol 43 (1) ◽  
pp. 55-79 ◽  
Author(s):  
Shirley E. Simon ◽  
B. M. Johnstone ◽  
K. H. Shankly ◽  
F. H. Shaw
Keyword(s):  
Steady State ◽  
Sartorius Muscle ◽  
Phase System ◽  
Extracellular Material ◽  
Foreign Ions ◽  
Three Phase ◽  
Na Efflux ◽  
Muscle Water ◽  
Toad Bufo ◽  
Normal Controls

The partition of Li+, Br-, and I- across the membrane of the sartorius muscle of the toad Bufo marinus has been investigated both at the steady state and with kinetic methods. Li+ was found to have access to an amount of muscle water similar to that of Na+. Br- and I- could be regarded as being interchangeable with cellular Cl-. None of the foreign ions caused significant losses of cellular K+. Li+ efflux from the cell was slower in muscles which were equilibrated for long periods in Li+ than in short equilibrated muscles. Na+ efflux from Li+-treated muscles was similar in rate to normal controls, but the amount of Na+ in the slow fraction was increased by Li+. I- efflux was extremely rapid, and it was not possible to differentiate kinetically between intra- and extracellular material. These results have been found to be consistent with the hypothesis of a three phase system for muscle.

scholarly journals High Performance Multistring Converter Topology for Three-Phase Grid Tied 200 kW Photovoltaic Generating System

2017 ◽  
Vol 1 (2) ◽  
Author(s):  
Mohammad Rustam M. L. ◽  
F. Danang Wijaya
Keyword(s):  
Power Efficiency ◽  
High Performance ◽  
Reactive Power ◽  
Simulation Method ◽  
Operating Conditions ◽  
Total System ◽  
Voltage Reference ◽  
Pv System ◽  
Three Phase ◽  
Converter Topology

Under various external conditions, grid connected PV system performance is strongly affected by the topology that is used to connect a PV system with grid. This research aims to design a multistring based converter topology for three-phase grid connected 200 kW PV system that has a high performance in various operating conditions. Research was done by a simulation method using Matlab-Simulink with performance being evaluated including the generated power, efficiency, power quality in accordance with grid requirements, as well as the power flow. In the simulation, multistring converter topology was designed using two dc-dc boost multistring converters connected in parallel to a centralized of three-phase three-level NPC inverter with the size of the string being shorter and more parallel strings as well as the maximum voltage of the PV array of 273.5 V close to dc voltage reference of 500 V. Each dc-dc boost multistring converter have individual MPPT controllers. The simulation results showed that this multistring converter topology had a high performance in various operating conditions. This due to more power generated by the NPC inverter (> 190 kW) at the time of high power generation on the STC conditions (1000 W/m2, 25 oC), the lowest efficiency of the total system is 95.08 % and the highest efficiency of the total system is 99.4 %, the quality of the power generated in accordance with the requirements of grid, as well as the inverter put more active power to the grid and less reactive power to the grid. The response of the inverter slightly worse for loads with greater reactive power and unbalanced.

scholarly journals Analysis of Stationary- and Synchronous-Reference Frames for Three-Phase Three-Wire Grid-Connected Converter AC Current Regulators

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8348
Author(s):  
Israel D. L. Costa ◽  
Danilo I. Brandao ◽  
Lourenço Matakas Junior ◽  
Marcelo G. Simões ◽  
Lenin M. F. Morais
Keyword(s):  
Steady State ◽  
Reference Frames ◽  
Computational Cost ◽  
Transient Behavior ◽  
Computational Effort ◽  
Superior Performance ◽  
Positive Sequence ◽  
Voltage Source ◽  
Three Phase ◽  
Grid Connected Inverter

The current state of the art shows that unbalance and distortion on the voltage waveforms at the terminals of a grid-connected inverter disturb its output currents. This paper compares AC linear current regulators for three-phase three-wire voltage source converters with three different reference frames, namely: (1) natural (abc), (2) orthogonal stationary (αβ), and (3) orthogonal synchronous (dq). The quantitative comparison analysis is based on mathematical models of grid disturbances using the impedance-based analysis, the computational effort assessment, as well as the steady-state and transient performance evaluation based on experimental results. The control scheme devised in the dq-frame has the highest computational effort and inferior performance under negative-sequence voltage disturbances, whereas it shows superior performance under positive-sequence voltages among the reference frames evaluated. In contrast, the stationary natural frame abc has the lowest computational effort due to its straightforward implementation, with similar results in terms of steady-state and transient behavior. The αβ-frame is an intermediate solution in terms of computational cost.

scholarly journals Improvement of protection relay with a single phase autore-closing mechanism based on artificial neural network

2020 ◽  
Vol 11 (1) ◽  
pp. 505
Author(s):  
Zozan Saadallah Hussain ◽  
Ahmed J. Ali ◽  
Ahmed A. Allu ◽  
Rakan Khalil Antar
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Transmission Line ◽  
Circuit Breaker ◽  
Logic Gates ◽  
Operating Conditions ◽  
System Stability ◽  
Phase System ◽  
Three Phase ◽  
Artificial Neural

This paper presents a developed logical tripping scheme to improve conventional protection performance. Adaptive single pole auto reclosure (ASPAR) system is proposed that considers, automatically tripping and reclosing of a multi-shot independent pole technique of a circuit breaker at a predetermined sequence, which can be used to boost the synchronization of the power grid under the transient fault conditions. Moreover, the ASPAR can be utilized to enhance the electrical system stability and reliability at the same operating conditions. Based on the three-phase system, the Artificial neural network (ANN) in this work has been done in order to diagnose and detect healthy and faulted phases. The proposed ANN fault classifier method consists of the logic gates, router circuits, timers, and positive and negative sequence analyses circuit. In addition, it is used to give the ability to recognize a fault type, which by training on the sequence angle values and coordination of the transmission line. Three-phase overhead transmission line including the proposed ASPAR is built in MATLA \SIMULINK environment. Thus the performance ANN-fault classified is tested under different fault conditions. Simulation results show that the proposed ASPAR based on ANN is accurate and well performance. Whereas resultant tripping and reclosing signals of ASPAR are successfully provided that enhances the circuit breaker mechanism under these operating condition.

scholarly journals Design of Super Twisting Sliding Mode Controller for a Three-Phase Grid-connected Photovoltaic System under Normal and Abnormal Conditions

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3773
Author(s):  
Kamran Zeb ◽  
Tiago Davi Curi Busarello ◽  
Saif Ul Islam ◽  
Waqar Uddin ◽  
Kummara Venkata Guru Raghavendra ◽  
...  
Keyword(s):  
Steady State ◽  
Dynamic Behavior ◽  
Reactive Power ◽  
Sliding Mode ◽  
Operating Conditions ◽  
Photovoltaic System ◽  
Frequency Variation ◽  
Sliding Mode Controller ◽  
Pv System ◽  
Three Phase

The novelty behind the research in this paper is to investigate the Super Twisting Sliding Mode Controller (ST-SMC) for efficiently injecting both active and reactive power under normal and abnormal operating conditions for a three-phase grid-connected photovoltaic (PV) system. The ST-SMC is aimed to inject sinusoidal current to the grid with low Total Harmonic Distortion (THD), to avoid chattering with easy real implementation, and to enhance the quality of disturbance rejection and sensitivity to parameter variation. The test under normal conditions includes initialization, steady state behavior, dynamic behavior, and interrupting the injection of acting and reactive power while the abnormal conditions consists of voltage sag, voltage swell, frequency variation, DC-link variation, and inclusion of 5th harmonics, etc. The phase lock loop used for synchronization is based on a synchronous reference frame that works well under distorted grids and nonideal. Automatic code is generated in PSIM 9.1 for hardware implementation in the DSP board TMS32F28335 from Texas Instruments while code composer studio 6.2.0 is used for debugging. The real time testing is executed using Typhoon Hardware in Loop (HIL) 402 device on the DSP board. The results authenticate the fastness, effectiveness, and robustness for both steady state and dynamic behavior under various scenarios of the designed controller.

Analysis of Saturated Self-Excited Dual Stator Induction Generator for Wind Energy Generation

2015 ◽  
Vol 24 (09) ◽  
pp. 1550129 ◽  
Author(s):  
Marwa Ben Slimene ◽  
Mohamed Arbi Khlifi ◽  
Mouldi Ben Fredj ◽  
Habib Rehaoulia
Keyword(s):  
Power Generation ◽  
Experimental Study ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Induction Generator ◽  
Magnetic Saturation ◽  
Wind Energy Generation ◽  
Three Phase ◽  
Mutual Leakage Reactance ◽  
Power Generation Systems

This paper presents the modeling of saturated dual stator induction generator (DSIG) for analysis of its transient and dynamic behavior for stand-alone operation. In the analytical model, the effect of common mutual leakage reactance between the two three-phase winding sets and the cross saturation have been considered. For this purpose, a detailed description of a procedure to introduce magnetic saturation in found models is presented. Paper also discusses the possibility of DSIG for supplying two individual loads by presenting the results of analytical and experimental study of transient behavior under various operating conditions. Use of such models leads to more accurate predictions in industrial drives, especially wind driven power generation systems. This is verified by experimental lab tests.

scholarly journals Speed Control Using an Integral Sliding Mode Controller for a Three-Phase Induction Motor

2021 ◽  
Vol 3 (3) ◽  
pp. 10-19
Author(s):  
Samar Abdulkareem AL-Hashemi ◽  
Ayad AL-Dujaili ◽  
Ahmed R. Ajel
Keyword(s):  
Steady State ◽  
Induction Motor ◽  
High Efficiency ◽  
Sliding Mode ◽  
Speed Control ◽  
Pi Controller ◽  
Operating Conditions ◽  
Sliding Mode Controller ◽  
Integral Sliding Mode ◽  
Three Phase

Induction motors are widely used in commercial and industrial applications due to their robustness, high efficiency, low maintenance requirements and durability among other reasons. Consequently, their speed should be controlled for better performance. This paper describes utilization of a scalar speed control of a three-phase squirrel cage induction motor (SCIM) to control a motor’s speed using an integral sliding mode controller (ISMC). The controller was tested under various operating conditions. The results are compared with a case employing a conventional PI controller. It was found that speed control by ISMC has a 0.16 RPM steady-state error, 0.03 s to reach steady-state from a standstill, and a 5% overshoot. All of these are lower values as compared to the results of a conventional PI controller. In this paper, the robustness of each controller to uncertainties is checked. Simulation results show the advantages of ISMC control methods. The system is simulated using MATLAB SIMULINK R2017a.

Steady and Transient Flow of a Non-Newtonian Chemically Reactive Fluid in a Twin-Screw Extruder

2001 ◽  
Author(s):  
W. Zhu ◽  
Y. Jaluria
Keyword(s):  
Steady State ◽  
Response Time ◽  
Transient Flow ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Twin Screw Extruder ◽  
Screw Extruder ◽  
Twin Screw ◽  
Calculated Velocity ◽  
Screw Extruders

Abstract The flow of chemically reactive non-Newtonian materials, such as bio-polymers and aciylates, in a fully intermeshing, co-rotating twin-screw extruder is numerically investigated. A detailed study of the system transient behavior is carried out. The main transient aspects, including response time, variation of system variables, and instability of operation, are studied for both single- and twin-screw extruders. The effect of a time-dependent variation in the boundary conditions is studied. The coupling due to conduction heat transfer in the screw barrel is found to be very important and is taken into account for single-screw extruders. In the absence of this conjugate coupling, the response time is much shorter. Several other interesting trends are obtained with respect to the dependence of the transient response on the fluid, materials, and operating conditions. Steady state results are obtained at large time. The calculated velocity distributions in the screw channel are compared with experimental results in the literature for steady state flow and good agreement has been obtained. The numerical results show that not all desired operating conditions are feasible. The calculated results for transient transport agree with the few experimental observations available on this system. These results will be useful in the design, control and optimization of polymer extrusion processes.

Steady-State and Dynamic Behavior of a Single-Phase Self-Excited Induction Generator Using a Three-Phase Machine

2007 ◽  
Vol 8 (3) ◽  
Author(s):  
S. N. Mahato ◽  
M. P. Sharma ◽  
S. P. Singh
Keyword(s):  
Steady State ◽  
Reference Frame ◽  
Single Phase ◽  
Short Circuit ◽  
Induction Machine ◽  
Transient Behavior ◽  
Experimental Results ◽  
Induction Generator ◽  
State Variables ◽  
Three Phase

This paper presents the steady-state and transient behavior of a single-phase self-excited induction generator (SEIG) using a three-phase machine with one shunt and one series excitation capacitors for resistive and inductive loads. The generation scheme consists of one three-phase delta connected induction machine and two capacitors - one connected in parallel with one winding and the other in series with a single-phase load. The dynamic model of the system has been developed as a hybrid model considering the stator phase currents in abc reference frame and the rotor currents in stationary d-q axes reference frame as state variables. The simulated and experimental results are presented for different dynamic conditions such as initiation of self-excitation, load perturbation and short-circuit. The simulated results of the steady-state analysis have been compared with the transient and experimental results and a close agreement between them indicates the accuracy and effectiveness of the approach.

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