Measurement Of Power Factor Research Articles

Development and Applications of Non-destructive Screening Tools for Thermoelectric Materials at NIST

The increased research and development of thermoelectric materials for energy conversion applications is driven primarily by the need for improved efficiency in the global utilization of energy resources. To facilitate the search for higher efficiency thermoelectric materials, we have developed a suite of complimentary high-throughput screening systems for performing thermoelectric metrology on combinatorial thin films. These custom capabilities include a facility for combinatorial thin film synthesis and suite of tools for screening the Seebeck coefficient, electrical resistance, and thermal conductivity of combinatorial films. The room temperature Seebeck coefficient and resistance are measured via an automated multiprobe apparatus, thus obtaining the power factor, S2σ (where S = Seebeck coefficient, σ = electrical conductivity). In addition, we are developing a high temperature (>300 K) power factor screening tool. Thermal effusivity (to calculate the thermal conductivity) is measured using a frequency domain thermo-reflectance technique. Using these tools, we are capable of performing power factor and thermal conductivity measurements on 1000 distinct sample-points within 6 hours for each instrument. This paper will detail several application examples using these tools on thermoelectric materials, including composition-spread films, conventional thin films, bulk ceramics, ribbons/tapes, and on single crystals.

Ge-Si based Nanowire Thermoelectric Materials in the Phonon Confinement Regime

For over a decade, nanotechnology has allowed rational synthesis of nanodot, nanowire and nanotube materials with different structure, composition, and with size control at the atomic precision. These nanoscale building blocks make it possible to explore electronic and energy harvesting devices with completely new operating principles. Similar to photonic and electronic confinement regimes where the device size approaches the wavelength of photon and electron wavefunctions, nanoscale semiconductor materials have enabled a new era of phononic engineering to turn waste heat into power and to explore the greener side of silicon. In particular, we have devised a highly sensitive differential bridge thermometry method to characterize thermal transport properties of individual Ge and heterostructure core-shell Ge/Si nanowires with diameters < 20 nm[1]. The resulting drastically suppressed thermal conductance beyond the diffusive boundary scattering limit is the first experimental evidence for the role of confinement effect on acoustic phonon dispersions in nanowires[2]. Lately we have also explored the high carrier mobility and concentration modulation in the semiconductor Ge/Si nanowires using gate modulation, and presented the first field-effect modulated thermoelectric power factor measurement on nanowires with diameters down to 11 nm[3]. The power factor was found to strongly correlate with carrier mobility and can exceed that of bulk Ge in nanowires with high hole mobility. Taken together, the well-established tunable electronic property, excellent thermoelectric power in Ge/Si nanowire materials, combined with thermal transport in the phonic confinement regime, are expected to open up a new level of thermoelectric performance beyond classical avenues.1. Wingert, M. C.; Chen, Z. C. Y.; Dechaumphai, E.; Moon, J.; Kim, J. H.; Xiang, J.; Chen, R. K. Nano Lett. 2011, 11 (12), 5507−5513.2. Zou, J.; Balandin, A. J. Appl. Phys. 2001, 89 (5), 2932−2938.3. J. Moon, J-H. Kim, Z.C.Y. Chen, J. Xiang, and R. Chen, Nano Lett. 2013, 13 (3), 1196–1202.

Online Measuring Power Factor in AC Resistance Spot Welding

The power factor is a very important process variable in ac resistance spot welding (RSW) operation. Because of the variation of welding load during the welding process, the power factor is a time-varying variable. The power factor of RSW cannot be obtained online because the value of power factor angle cannot be directly measured in real time. After analyzing the electrical structure of RSW, a new algorithm for measuring the power factor angle in real time is developed. Then, an integrated algorithm for calculating the power factor on a practical discrete system in real time is proposed. Experiments were conducted to validate the effectiveness of the proposed method. The experimental results showed that the proposed algorithm can be used to obtain more accurate values of the power factor angle than using other methods over a very large operation range. The final results of power factors obtained from the proposed algorithm are very close to the results from the numerical simulation.

The Study on Electric Parameters Automatic Test System

Based on a digital signal processor hardware and the wavelet transform theory the next generation of electri'cal parameters automatic test system is designed. The current and voltage signal measurement relative error is not more than 0.2%, the power factor and harmonic content measurement error is not more than 1.1%, and frequency signal measurement error is less than 0.1% by this system.

Absolute Measurement of Current Dependence in DC Resistors by a Double Current Method

A double current method is presented for absolute measurements of the current dependence (power variation) of dc resistors. Based on the resistance measurement principle of a direct current comparator (DCC), and adding another DCC-based extender with a turn ratio 1:1, the testing current in resistors to be tested is accurately doubled. Through three comparative measurements with two reference standard resistors connected in series as Kelvin resistive bridge inner arms, the change of resistance caused by doubling the currents is measured. Cyclically done, absolute measurement of current or power factor is realized. Examples of the current dependence of some commercial low-temperature coefficient 1 Ω standard resistors are given using the presented method and their results are analyzed.

Measurement of Phase Angle and Power Factor by Multiplexing Technique

A technique which measures the power factor and phase difference between two sinusoidal signals, using a multiplexers IC 4053 is explained in this paper.

Metallurgical and thermoelectric properties in Co1−xPdxSb3 and Co1−xNixSb3 revisited

Polycrystalline thermoelectric Co1−xMxSb3 (M=Ni, Pd) skutterudites have been synthesized by melting, annealing, and spark plasma sintering. The solubility limit of Pd and Ni are determined to be respectively xmax=0.03 and xmax=0.09. The density of states effective masses range between 2.0m0 and 4m0 in Co1−xPdxSb3 and Co1−xNixSb3. These values are consistent with the effective band mass (0.3m0) and the degeneracy number Nv=36 derived from band structure calculations. Power factor measurements and calculations in Co1−xPdxSb3 show that at 300K, the optimum electron concentration would be [n]opt=1.4×1020cm−3, slightly beyond the electron concentration (1.1×1020cm−3) of the solubility limit composition Co0.97Pd0.03Sb3. The maximum power factor is effectively obtained for the composition Co0.97Pd0.03Sb3 and reaches 4.3mWm−1K−2 at 700K. An activation energy, which can correspond to the intrinsic gap εG=0.13eV, is determined in Co0.98Ni0.02Sb3. Co1−xNixSb3 displays smaller electronic mobilities than in Co1−xPdxSb3 leading to smaller power factors. Best properties (3.4mWm−1K−2) are observed at 700K in Co0.95Ni0.05Sb3–Co0.94Ni0.06Sb3.

Research of Calibration Instrument of Multi-Site Single-Phase Energy Meter

This design is a full-featured, high precision power meter on-site calibration device and integrated electrical parameter measuring device. The internal use of SCM control, you can not open the instrument case, through the keys with precision adjustment, thus increasing the reliability and stability. This study projects able to keep the case of electricity meters for a variety of electrical power meter, indicating a variety of instrumentation and electrical power transmitters to provide on-site instruments detection, but also to voltage, current, power, power factor, phase, frequency and other electrical parameters measurement.

Design and implementation of a low-cost multiple-range digital phase detector

This article describes the design, simulation, implementation and testing of a novel low-cost multiple-range programmable digital phase detector. The detector receives two periodic signals and calculates the ratio of the time difference to the time period to measure and display the phase difference. The resulting output values are in integer form ranging from −180° to 180°. Users can select the detector pre-set operation frequency ranges using a three-bit pre-scalar. This enables to use the detector for various applications. The proposed detector can be programmed over a frequency range of 10 Hz to 25 kHz by configuring its clock divider circuit. Detector simulations were conducted and verified using ModelSim and the design was implemented and tested using an Altera Cyclone II field-programmable gate array board. Both the simulation and actual circuit testing results showed that the phase detector has a magnitude of error of only 1°. The detector is ideal for applications such as power factor measurement and correction, self-tuning resonant circuits and in metal detection systems. Unlike other stand-alone phase detection systems, the reported system has the ability to be programmed to several frequency ranges, hence expanding its bandwidth.

Optimal Power Factor Correction for Inductive Load Using PIC

Power factor correction (PFC) is a technique to improve the stability and efficiency of the transmission network to reduce the costs charged to the customers by their electricity supplier. A PIC microcontroller based power factor correction has been designed. The paper deals with the hardware and software features of the power factor correction unit. The phase difference between the two signals is obtained by measuring the ON time ‘τ’ of the XOR gate and the time period ‘T’ of the signal using the two CCP module of PIC18F452 microcontroller. The power factor correction unit is designed for the measurement of power factor between 0 -1 for frequencies up to 500Hz with an accuracy of ± 0.1. This involves measuring the power factor value from the load using PIC and sensors proper algorithm to determine and trigger sufficient switching capacitors in order to compensate excessive reactive components, thus bringing power factor near to unity and also monitoring the power factor changes in LCD as a result acquires higher efficiency and better quality AC output Power factor correction.

Design of a Power Factor Measurement System for Nonlinear Load

This paper introduces and develops an efficient method for measuring power factor (PF) and its nature under nonlinear load current situations. The method is based on generating a pulse width modulated signal whose width correlates to the value of PF. This signal can then be employed as a feedback signal for controlling PF related power quantities in a system. This method has the advantages of its simple implementation, less computational complexity, and its allowable error of less than 4[%], which is justified by the computer simulation results.

Experimental proof of voltage‐current waveform sensor output of resin molded type for measurement of power factor and harmonics in general power distribution system

AbstractWe have proposed a voltage‐current sensor of resin molded type for measurement of the power factor and harmonics. To understand the characteristics of the conventional prototype sensor and the problems of its practical use, we conducted a finite element analysis. Problems involving the cost and practical usage of the sensor were identified. Therefore, we have redesigned the prototype sensor, incorporating the current sensor designed on the basis of the FEM and a ready‐made voltage sensor. In this paper, we describe feasibility field experiments with the present sensor in a practical 6.6‐kV distribution system and show that the sensor can measure the power factor and harmonics of horizontal and vertical power line systems successfully. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(3): 1–10, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21213

POWER FACTOR AND DISTORTION MEASURING FOR SMALL LOADS USING USB ACQUISITION MODULE

Power factor and distortion measuring usually require dedicated and expensive equipments. Computer-based acquisition modules and software provide for a possibility to create simple and nonexpensive methods and instruments for power factor measurement and distortion characterization of small loads and bring all advantages of virtual instrumentation. A new approach to power quality characterization by measuring power factor, distortion, and several other parameters of small electric loads (up to 0.5 kW) will be described in this paper. Besides low price maximum versatility and adaptability are provided without any loss in accuracy.

An Adaptive Scheme for Power-Related Measurements and Power-Factor Correction

This paper presents a fast, low cost and accurate instrumentation scheme for power-related measurements and power-factor correction. These measurements include the root-mean-square values of current and voltage, the active and reactive powers, the total harmonic distortion and the true power factor. It is a microcontroller-based digital sampling system which runs a fast algorithm for displacement power factor measurement. The controlling system monitors and senses any variations in power factor, and accordingly switches the appropriate capacitor combination across the load. The scheme presents an economical and efficient solution to the power distribution companies for its customers.

Temperature dependent thermoelectric material power factor measurement system

Thermoelectric materials can be used for cooling/heating applications, or converting waste heat into electricity. Novel thermoelectric materials have been discovered in recent years. Characterization of an electrical conductivity and thermopower of a sample from room temperature to > or = 900 K is often necessary for thermoelectric materials. This paper describes a system built for measurement of the power factor of thermoelectric materials from 300 to 1273 K. Characterization results of the system are also presented.

THE EFFECT OF VARIATION OF NONLINEAR LOAD ON POWER FACTOR OF THE AC SUPPLY NETWORK

The aim of this paper is to evaluate the effect of the converter system on the power factor of the supply network .Therefore a 3-phase, 6-pulse , bridge converter is assembled and connected to a power supply through a 3-phase ac voltage regulator .The theoretical analysis is simulated using Fourier series analysis and Fast Fourier Transform ( FFT ) algorithm . The experimental measurements of distortion factor , displacement factor and total power factor are recorded . The experimental results are shown to be coincident with the theoretical results. The consideration of power factor improvement relative to distortion and displacement factors is discussed.

Power factor measurements of bismuth telluride nanowires grown by pulsed electrodeposition

AbstractThe power factors of bismuth telluride nanowires were determined. Large‐scale thermopower measurements of the nanowire arrays were performed under a constant thermal gradient. The local electrical resistance of individual nanowires inside alumina matrix was investigated at ambient conditions by a conductive tip attached to an atomic force microscope (AFM). In order to prevent oxide formation on the nanowire tips, an Au electrode segment was electrochemically deposited onto the nanowires. The optimized structural properties led to a significant improvement of the electrical conductivity of the nanowires from 0.053 to 0.169 × 106 (Ω m)–1 and their Seebeck coefficient also increased moderately from 46.6 μV/K to 55 μV/K. Based on our measurement approach, the determined maximum power factor is 476.3 μW/mK2, which is one of the highest reported values for electrodeposited Bi2Te3 nanowires. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Experimental Proof of Voltage-Current Waveform Sensor Output of Resin Molded Type for Measurement of Power Factor and Harmonics in General Power Distribution System

We have proposed the voltage-current sensor of resin molded type for measurement of the power factor and harmonics. To grasp the characteristics of the conventional prototype sensor and the problem in its practical use, we have conducted the finite element analysis for that. There occurred problems on the cost and the practical usage in making use of the sensor consequently. Therefore we have redesigned the prototype sensor, where the current sensor designed based on the FEM and a ready-made voltage sensor have been incorporated. In this paper, we will describe the feasibility field experiment of the present sensor in the practical 6.6kV distribution system and show that the sensor can measure the power factor and harmonics for the horizontal and vertical power line systems successfully.

Design and implementation of a novel power factor monitoring unit using discrete wavelet transform

Design and implementation of a novel on-line single-phase power factor measurement technique under non-sinusoidal and time-varying environments are presented. The proposed method expresses true power factor in terms of displacement and distortion power factors under certain significant facts, as defined in IEEE Std. 1459-2000. The displacement power factor is evaluated using a unique digital signal-processing algorithm, whereas discrete wavelet transform (DWT) based multi-resolution analysis has been proposed for an accurate estimation of distortion power factor. An efficient algorithm to perform DWT in real time, using Texas Instruments TMS320VC5416 digital signal processor, has also been discussed. Illustrative laboratory test results confirm the validity and accurate performance of the proposed method for tracking true power factor under both static and dynamic situations.

Model-Based Real-Time Dynamic Power Factor Measurement in AC Resistance Spot Welding With an Embedded ANN

Today, real-time measurement of dynamic power factor in resistance spot welding (RSW) is of increasing importance. On the basis of the welding transformer circuit model, a new method is proposed to measure the peak angle of the welding current and then calculate the dynamic power factor in each half-wave. The tailored sensing and computing system ensures that the measuring method possesses a real-time computational capacity with satisfying accuracy. Since the power factor cannot be represented via an explicit function with respect to measurable parameters, the traditional method(s) has to approximate the power factor angle with a constant phase lag angle and fails to detect its dynamic characteristics. An offline-trained embedded artificial neural network (ANN) successfully realizes the real-time implicit function calculation or estimation. A digital-signal-processor-based RSW monitoring system is developed to perform ANN computation. Experimental results indicate that the proposed method is applicable for measuring the dynamic power factor in single-phase half-wave controlled rectifier circuits