All posts by cburada

Reactive Energy Compensation Equipment Used in High Power Laboratories

17 January 2023Fără categoriecburada

Abstract

The power quality covers the means to conserve energy resources, such means consist in improving the power factor and judiciously managing the reactive energy in the power system. Electric grids do not have an unlimited energy transmission capacity, therefore any load on the grid with reactive energy is measured by the energy distributor/supplier and billed to the consumer. On the premise that for industrial consumers, the main consumers of reactive energy are the low-load induction motors and transformers, this paper presents a synchronization equipment for a wound-rotor induction motor with a power of 2000 kW, nominal voltage 6kV, nominal current 210A, which allows the increase of the power factor, significantly reducing the reactive energy consumption. The equipment presented was designed, built, tested and validated by tests carried out in the high-power laboratory.

Comparative Analysis in the Case of Indirect Current Control in a Shunt Active Filtering System

17 January 2023Fără categoriecburada

Abstract

In this paper, the performance of a three-phase four wire shunt active power filter (APF) using indirect current control with active load current calculation was compared with that corresponding to using indirect current control with prescribed current calculation from the voltage controller. It is clear that, under balanced and sinusoidal voltage conditions, these two methods give similar results. The variant of the indirect current control with prescribed current calculation from the voltage controller has the  advantage of simplicity, but exhibits increased sensitivity to voltage ripples on the compensation capacitor, as they are reflected in the output of the voltage controller. The whole system was modeled using MATLAB-SIMULINK software. The simulation results demonstrate the applicability of both methods for APF control.

Application of Electrical Substation, Ring Topology versus Star Topology

17 January 2023Fără categoriecburada

Abstract

In order to solve the problem of analyzing network performance of SCADA (Supervisory Control And Data Acquisition) system communication of power grid in effective and practical way, this paper proposes to change the star topology with ring topology, specifically method rapid spanning tree protocol (RSTP), in an electrical substation. The paper discusses about SCADA architecture, main equipment like remote terminal unit, intelligent electronic device, server, server network time protocol, HMI (human machine interface), router and their role in the electrical substation. Also, the levels of the command hierarchy in the SCADA system are discussed. Each level has certain tasks set for the optimization and reliability of the electrical substation. The data flow describes the types of information that are transmitted between hierarchical levels. In the last part the paper the topologies of the system are described.

Analyzing the Influence of Harmonic Parameters on Accuracy Indices When Applying Wavelet Transform

17 January 2023Fără categoriecburada

Abstract

The paper deals with the evaluation of root mean square deviations and maximum absolute relative errors associated to the decomposition followed by recomposition based on Wavelet Packet Transform (WPT) of signals polluted with harmonics. Subtrees associated to sets of harmonics presenting practical interest for industrial applications are addressed. The study uses artificial signals generated through the superposition of perfect sinusoids with pairs of harmonics which proved to be related in an almost exclusive manner to pairs of nodes from the bottom level of a WPT tree. 4 parameters had to be considered when determining the maximum and minimum values of errors for each set: the clustered harmonics’ magnitudes and their phase-shifts relative to the  omponent of fundamental frequency. The decomposition/recomposition are time-efficient due to an original system of flags labeling each node from the WPT tree. For each analyzed set of harmonics, 3d graphical representation of minimum and maximum errors along with the associated 3d graphical representation of the phaseshifts are provided. At the same time, per set limits of errors ranges were established and discussed while specific patterns were deduced for the context in which extreme errors appear (phase-shifts and harmonic magnitudes). The results were commented, and conclusions were drawn.

Two Numerical Studies for Longitudinal Movement of a Canard UAV with Vectored Thrust

21 January 2022Fără categoriecburada

Abstract

This work presents a study concerning the possibilities to improve the longitudinal dynamic of a canard UAV using vectored thrust. It is followed to harness the advantages of canard configuration of UAV and to obtain further a better longitudinal dynamic, able to fulfil more complex missions than canard UAV without vectored thrust. There are tested two methods. The first uses the UAV polars obtained in XFLR 5 and extended, using literature experience, a little bit over the stall angle. By this method is determined the necessary gain between the elevator steering angle and thrust deflection angle in order to maintain the UAV in landing configuration (flaps down) to the optimum angle of attack for landing. Using this method is studied also the effect of vectored thrust in maneuver, in cruise configuration. Step signal on the elevator, thrust and both commands simultaneously are applied on the UAV without and with vectored thrust and are identified the advantages of vectored thrust in this situation. The second method uses the polars of the UAV components obtained in XFLR5, extended independently up to a little bit above each stall angle. By this way is studied the effect of the vectored thrust on the atack angle in horizontal flight for the UAV in cruise configuration. There are obtained horizontal flight parameters (speed, elevator steering, angle of attack and thrust), when vectored thrust is used. It is followed to obtain results for attack angle as high as possible. Both methods are limited by the results obtained in XFLR 5, that can’t determine polars at atttack angles near stall, and for the second method, by the aerodynamic interferences between UAV components.

Ways to Determine the Structural Resource of Highly Maneuverable Aircraft

21 January 2022Fără categoriecburada

Abstract

This paper emphasizes the importance of monitoring aircraft structural fatigue and proposes as paramount the analysis of military aircraft structural constitutive materials aging process, during flight. Aircraft structural health monitoring is defined as an evaluation process for the integrity of key structural components with the sole purpose of enhancing flight safety and mitigating maintenance risks and loses. Nowadays, aircraft are predominantly built from composite materials with at least two layers with different mechanical properties, which combined, result in a new composite material with highly superior resilience and elastic properties. Even though there are great advantages of using composite materials, when it comes to operating military aircraft, a mere visual inspection cannot be sufficient for observing or identifying structural damages within the composite layers of the aircraft. The focus of this study is on improving the process of monitoring the structural condition of highly maneuverable military jet aircraft by using the strain gauge marks methods. Monitoring aircraft structural condition can be easily implemented, both during maintenance and flight missions, by using a wide array of sensors that can generate specific sets of instructions for all processes involved in enhancing flight and maintenance safety. The main concern of implementing a structural evaluation, within aircraft maintenance processes, sits on preventing and not ameliorating incidents and accidents during flight. As a result of the continuous research and testing, it has been proved that the operational resource of the aircraft structure, provided by the manufacturer, can be easily reached in a lot lesser flight hours than initially anticipated, by engaging the aircraft in specific operational missions and, therefore, inflicting pronounced fatigue on the aircraft structure.

Simulation of Multi-Motor Propulsion System for Energy Efficiency in Electric Vehicles

21 January 2022Fără categoriecburada

Abstract

For a vehicle, the knowledge of components, characteristics, performances, and behaviors are some base elements for a successful simulation. Today’s tools are offering instruments able to cover a such request and new possibilities appear. Choosing the right ones, representing the entire vehicle as a system of subsystems, integrating as much as possible the parameters of different components, are also few additional elements. For internal combustion engine vehicles, the generation and the transmission of the mechanical power to the wheels imply the usage of specific mechanic parts. From a single engine, the mechanical power is controlled to offer the requested torque and speed simultaneously to the vehicle wheels, passing by clutches and gearboxes. An electric propulsion, generating high torque at zero speed, and covering large speed area, implies less components for the mechanical transmissions. One single gear, a reducer, could cover the entire speed area request of the vehicle. On the other hand, it is possible to approach the generation of the mechanical power to the wheels, by using not only one electric motor, but one for each axle, or, even more, one electric motor for each wheel of the vehicle. This paper presents the usage of numerical simulation in such situations, emphasizing opportunities for onboard energy efficiency improvement, and opening new possibilities for optimization in multiple motor solutions.

Experimental Study of HBC Fuses with Aluminium Fuse Element at Minimum Rated Breaking Current, Maximum Rated Breaking Current and Transfer Current of Fuse-Switch Combination

21 January 2022Fără categoriecburada

Abstract

The article presents an experimental study of high breaking capacity fuses with aluminum fusible element with and without a eutectic point, at minimum rated breaking current, preceded by experiments at maximum rated break-ing current. The paper shows that in the construction with aluminum fusible element, the fuse has no problem breaking the maximum rated breaking current, but real difficulties appears when it comes to the minimum rated breaking cur-rent. The experiments were made on a homogeneous series 6-20 A, with a focus on the 36 kV, 25 kA, 16 A fuse. The fuses suffered multiple construction changes and tests with and without a eutectic point. After several tests was found an acceptable constructive solution was, but the obtained value for the minimum rated breaking current is not a commercially attractive value. It was also tested the capacity of the fuse to transfer the breaking duty to a load break switch.

Considerations on the Disturbances Occurred in the Operation of Medium Voltage Electrical Networks with Neutral Treated by Suppression Coil

21 January 2022Fără categoriecburada

Abstract

In this paper are analyzed the analytical models of theoretical calculation and analysis of the main conse-quences of neutral treatment by suppression coil on the ope-ration of medium voltage electrical networks, both in nor-mal regime and especially in single-phase fault regime. The size of stationary and transient overvoltages and fault cu-rrents is evaluated for a concrete case study. Also the au-thors present in this paper the results they obtained after the extension of their research and in the field of harmonic regime produced by the grounding of a power line. This type of fault occurs frequently in the case of medium voltage networks, with neutral treated with suppression coil. Thus, they managed to reconstruct the waveforms of currents and voltages during the fault period (grounding). Then, having these calculation elements available, a comparative analysis of similar incidents (earthing) from a 20 kV network with the neutral treated with classic suppression coil and mo-dern Trench suppression coil, respectively, was made.

Automatic Ventilation and Air Conditioning System for Educational Trainin

21 January 2022Fără categoriecburada

Abstract

The air quality from closed spaces is very im-portant for people or for technological processes. The heat-ing, ventilation and air conditioning installations ensure the maintenance of the air parameters in the rooms served with-in pre-established limits, throughout the year, regardless of the variation of meteorological factors, the degree of occu-pancy of the rooms or the development of production pro-cesses. The paper presents an automatic ventilation, heating and air conditioning system made on a small scale. Climatic parameters can be monitored and controlled in two ways: in local mode and also in remote mode. In local mode, the con-trol of the installation is done with a Mega 2560 develop-ment system made around the Atmega 2560 microcontrol-ler, which processes the information received from the DHT22 temperature and humidity sensor. Information about parameters and system status is displayed on the local screen. The WeMos D1 R2 WiFi development system based on an ESP8266 wireless microcontroller with Wi-Fi 802.11 compatible with the IDE-Arduino development environment was used for the remote control. All information is transmit-ted wirelessly to an online platform, called Cayene that al-lows their storage and control. The platform referred to offers a number of graphical features that do not involve costs for users. The system can be used both for educational purposes for engineering students, but can be adapted for real practical applications.