Comparison Of Power Losses Research Articles

Magnetic properties evolution and crystallization behaviour of vacuum- and air-long-term-annealed rapidly quenched Fe80.3Co5Cu0.7B14 alloy.

This work aims to investigate the isothermal crystallization behaviour, crystal structure and magnetic properties evolution of long-term (up to 300h) low temperature (210 and 260°C) vacuum- and air-annealed Fe80.3Co5Cu0.7B14alloy. Before the α-Fe(Co) phase crystallization, the primary relaxation process has been identified at a temperature range up to 340°C. The relaxation process performed under 210°C for 300h did not initiate the crystallization process. However, the topological and compositional short-range rearrangements improved magnetic properties remarkably. Annealing 150h at 260°C helps to deliver enough energy to stabilize the glassy state and initiate the crystallization process fully. Structural and magnetic properties evolution of 150h annealing at 260°C corresponds to the evolution presented during isochronal 20min annealing at 310°C. Magnetic properties Bs = 1.75-1.79T, Hc < 20 A/m and P10/50are similar to those for 20min of annealing at 310°C. Comparison of core power losses from up to 400kHz frequency dependences of long-term low temperature annealed alloy with 20min classical annealing at 310°C shown that presented here long-term annealing is energetically insufficient to bring the glassy state system into the same low level of core power losses efficiency.

Study on Comparison of Power Losses Between UPQC and UPQC-DG

In the era of modern power distribution network, the motivation to use green and clean energy resources for fulfilling the need of energy demand is gaining abruptly. This has enhanced the use of power electronics-based conversion devices leading to deterioration of power quality in the power distribution network. Several compensating custom devices, such as static compensators (STATCOMs), dynamic voltage restorers (DVRs), and unified power quality conditioner (UPQC), etc., have been developed in recent decades. UPQC consists of shunt active power filter (APF) and series APF connected in back-to-back fashion with a shared DC-link. In the case of UPQC-DG, a distributed generator (DG) is also connected at the DC-link. In the existing literature available, UPQC integrated with DG is found to be a promising topology which can simultaneously compensate for power quality issues and integrate DG into the grid. Its functionality and performances have been presented by many researchers, but a detailed investigation on its power losses is missing. This article presents a detailed comparison of conventional UPQC, UPQC-DG, and UPQC-independent DG (UPQC-IDG) in terms of their respective power losses and further enhances the criteria for selecting the best possible configuration to be used practically based on requirements and economical viability. In this executed work, the power losses are compared among UPQC, UPQC-DG, and UPQC-IDG for different steady-state and dynamic operating conditions. The power losses in all configurations are inclusive of conduction losses, filtering losses, and switching losses, found using simulation and empirical studies. The comparative study is based on computer simulations performed in MATLAB/Simulink and real-time simulation using Opal-RT.

An experimental investigation of windage and oil churning power losses of gears and discs

This study presents comparable sets of churning and windage power loss measurements of a gear. Measurements are performed under windage (air only) and churning (immersion in oil up to a certain level) to quantify load-independent power losses of a family of spur and helical gears along with representative discs. Aiming at quantifying the impact of gear geometry on churning or windage losses to establish a baseline for the case of no enclosures around the gear, the test matrix is designed to investigate three key items: (a) contribution of losses along the periphery and faces, (b) the influences of gear teeth versus a toothless replacement disc as well as key design parameters (gear module and helix angle), and (c) a comparison of churning and windage power losses measured from the same exact set-up. The churning power losses are shown to increase with the static oil levels due to increased solid-fluid interactions. The impact of oil bath temperature (oil viscosity) on churning loss is observed to be more pronounced for higher oil levels. The presence of gear teeth on the rotating specimen (spur or helical) cause churning loss to increase modestly in comparison to the disc specimens. Furthermore, a larger tooth size results in higher churning power losses. The influence of gear teeth (gear vs. disc) on windage loss is shown to be significant, indicating that modeling a gear in a high-speed windage condition as a cylindrical disc might not be an acceptable practice.

Comparison of Power Distribution, Losses and Efficiencies of a Steam Turbine with and without Extractions

The paper presents an analysis of two steam turbine operation regimes - regime with all steam extractions opened (base process) and regime with all steam extractions closed. Closing of all steam extractions significantly increases turbine real developed power for 5215.88 kW and increases turbine energy and exergy losses with simultaneous decrease of turbine energy and exergy efficiencies for more than 2%. First extracted steam mass flow rate has a dominant influence on turbine power losses (in comparison to turbine maximum power when all of steam extractions are closed). Cumulative power losses caused by steam mass flow rate extractions are the highest in the fourth turbine segment and equal to 1687.82 kW.

АНАЛИЗ ПОТЕРЬ МОЩНОСТИ В КОНТАКТНОЙ СЕТИ ПРИ ПОПЕРЕЧНОЙ ЕМКОСТНОЙ КОМПЕНСАЦИИ

Objective: To analyze the loss of power in cable wires of the railroad alternate current catenary system both in the presence and in the absence of equalizing gear in the middle of inter-substation zone, taking into account train traffic. Methods: Passing of one train and two others following each other along the inter substation zone was considered. The comparison of power losses in cable wires of the catenary system was conducted both in the presence and in the absence of equalizing gear. The difference of losses was determined. The simulation of one train passing along the inter-substation zone was fulfilled in the environment of MATLAB-Simulink. Results: It was shown, that the average values of power losses in cable wires of the catenary system were equal with one train passing along the inter substation zone both in the presence and in the absence of equalizing gear. In case of two trains passing along the inter substation zone, following each other with equalizing gear capacity, selected by the average idle current of one train, the losses of power in cable wires of the catenary system decreased with equalizing gear installation, however, in that case, reactive power was partially compensated. The simulation of one train passing along the inter-substation zone in the environment of MATLAB-Simulink, taking into account power losses in the catenary system and railroad substations resistance, substantiates the assumptions taken in the analytical estimation. Practical importance: Despite the fact, that active development of filter compensating devices is conducted in the sphere of reactive power compensation on the railroad transport, capacitor banks are still used on alternate current railroads. The given study is aimed at the improvement of the current procedure of selecting optimum power of equalizing gears.

A comparison of time-average power losses in insulated-gate bipolar transistors and hybrid SIT–MOS–transistors

Switching of equivalent silicon insulated-gate bipolar transistors, such as carrier-stored trenchgate bipolar transistors (CSTBTs) and hybrid static induction transistor/metal–oxide–semiconductor (SIT–MOS) thyristors (HSMTs), from a blocking state to a conducting state and vice versa is numerically simulated in two dimensions. It is shown that on–off switching losses in an HSMT are greater than in a fully equivalent CSTBT. Thus, time-average power P that dissipates in an HSMT becomes smaller than the power in the equivalent CSTBTh only at a long current pulse duration. However, a decrease in lifetime τ0 of nonequilibrium charge carriers in an SIT makes it possible to significantly reduce HSMT switching losses while maintaining its advantage in the on state. Consequently, for each set of CSTBT parameters, such τ0, it can be selected in the almost equivalent HSMT that power P dissipating in the HSMT will be smaller than the power in the equivalent CSTBT in any given range of amplitude J a and duration T on of the current pulses.

Comparison of Power Losses and Temperatures between an All-Steel and a Direct Outer Ring–Cooled, Hybrid 133-mm-Bore Ball Bearing at Very High Speeds

ABSTRACTNext-generation aircraft engines will have to face more stringent requirements for reliability, thrust to weight, efficiency, environment protection, and profitability. These requirements affect all engine modules and components, including rolling element bearings. To cope with the above-mentioned requirements, next-generation aircraft engine main shaft bearings will operate under higher loads, speeds, and temperatures and increased reliability. In addition, lighter weight components are desirable. Hence, new material and cooling technologies including weight- and stress-optimized designs need to be developed.In this article, the experimental investigation results of a novel main shaft ball bearing featuring ceramic balls, direct outer ring cooling, squeeze film damping, as well as surface-nitrided raceways are presented. Bearing rig testing under typical aircraft engine flight conditions has been performed. Savings for oil flow quantity of more than 45% and for power loss of more than 15% were identified. Outer ring temperature reductions of more than 20 K were achieved due to the use of ceramic ball material and the direct outer ring cooling concept. The ultra-high-speed capability of the bearing was demonstrated. Rotational speeds of 24,000 rpm were achieved at bearing temperatures below 200°C. The fundamental experimental results including oil and bearing temperature distribution, power dissipation, and bearing efficiency are presented. In addition, experimental power loss and temperature results are compared with data for a conventional all-steel bearing.

A study on power losses of the 50 kVA SiC converter including reverse conduction phenomenon

Abstract This paper deals with performance of the 50 kVA three-phase converter built with switches based on SiC MOSFET and anti-parallel Schottky diodes. In contrast to popular IGBT converters, a negative switch current is capable of flowing through the reverse conducting transistor, which results in different distribution of power losses among the devices. Thus, equations describing the conduction power losses of the transistor and diode are improved and verified by means of circuit simulations in Saber. Moreover, a comparison of power losses calculated with the use of standard and new equations is also shown. Total power losses in three SiC MOSFET modules of a 50 kVA converter operating at 20 kHz are up to 30% lower when reverse conduction is taken into account. This shows the importance of the discussed problem and proves that much better accuracy in the estimation of power losses and junction temperatures of SiC devices may be obtained with the proposed approach.

Comparison of power losses, current and voltage stresses of semiconductors in voltage source transformerless multilevel inverters

The power losses, current and voltage stresses in semiconductor devices in voltage source transformerless multilevel inverters (VSTMLIs) topologies are unequal, depending on the switching states, the duty ratio, the levels of output voltage, the load power factor and the depth of modulation index. Non-uniform power loss profiles mean both unequal junction temperature and power rating in semiconductors. In this study, a comparison of power losses, current and voltage stresses in semiconductors of VSTMLIs is performed. Initially, the structural characteristics and operating principles of dominant VSTMLIs with sinusoidal pulse width modulation are analysed. Then, modifications of existing VSTMLIs and simplified multilevel topologies are proposed, which achieve a further reduction in switch count and power losses in semiconductors. The proposed modified circuitries are suitable for converting existing four-level VSTMLI topologies into five-level ones. This conversion is desirable, when a zero output voltage level under no-load conditions or low modulation indices should be obtained. Power losses in semiconductors are calculated analytically and then confirmed by simulation. A comparative presentation of profiles of power losses, current and voltage stresses in semiconductors of the examined VSTMLIs is analytically carried out. The obtained results are valuable for sizing and selecting the semiconductors in VSTMLIs.

Two‐switch flyback PWM DC–DC converter in discontinuous‐conduction mode

AbstractThe two‐switch flyback DC–DC converter is an extended version of the conventional single‐switch flyback converter. An additional switch and two clamping diodes serve as a simple, but an effective way to limit the switch overvoltages, which occur in the conventional single‐switch flyback converter due to the ringing of the resonant circuit formed by the transformer leakage inductance and the transistor output capacitance. The clamping diodes in the two‐switch flyback topology clamp the maximum voltage across each switch equal to the DC input voltage. This paper presents a detailed analysis and design procedure of the diode‐clamped two‐switch flyback converter operated in discontinuous‐conduction mode (DCM). A comparison of power losses of the two‐switch and the single‐switch flyback converters is given. The two‐switch flyback converter was bread‐boarded to validate the theoretical analysis. Experimental results from a 20‐V/30‐W, 100‐kHz laboratory prototype verified that the maximum switch voltage is limited to the DC input voltage. Copyright © 2010 John Wiley &amp; Sons, Ltd.

It’s effective to set down systems with frequency – controlled by electrical accessories

In the article the basic attention is paid to comparison of power losses in drives of pumps with various kinds of control. The resulted material focuses in determination of those units of the drive systems where the application of a frequency control is the most advantageous.

Power losses of Finemet using nonsinusoidal waveforms

Though many practical applications preferably take advantage of nonsinusoidal induction waveforms the characterisation of soft magnetic materials is performed under sinusoidal induction waveforms. Therefore, it would be useful if results from magnetic measurements could be transformed to be valid for applications using different waveforms. This also enables to compare results obtained from measurements where sinusoidal waveforms could not be realised and thus makes them independent of the measuring device used. The dynamic hysteresis loops of differently prepared Finemet ribbons were measured with a computer controlled device at different frequencies and polarisations using sinusoidal and triangular waveforms of the magnetic field which leads to induction waveforms varying with frequency, amplitude of polarisation, waveform of the magnetising field and preparation of specimen material. The samples measured were strips of Fe 73.5Si 13.5Cu 1Nb 3B 9 nanocrystallised at 580°C for 1 h. Different types of samples were used which includes specimens surface treated prior to heat treatment in order to achieve domain refinement. A one to one functional dependency between power loss, frequency, and k-factor was found that enables the comparison of power losses for different induction signals characterised by their form factor as it is already known for grain oriented silicon steel sheets. This dependency is valid for all types of specimen investigated regardless of their different magnetic properties.