Search results for "armo"
showing 10 items of 1364 documents
The CIGR project for the harmonization of Agricultural Engineering University Curricula
1994
Abstract A project for the harmonization of Agricultural Engineering University Curricula was started in 1989 at European level. This project led to two seminars (in 1991 and 1992) and to a survey of current University organization and Curricula of Agricultural Engineering in 25 Countries. The harmonization project is still under way and has achieved world-wide interest. In this paper the main results already obtained, together with possible future developments, are presented.
A novel approach to current transformer characterization in the presence of harmonic distortion
2009
The current transformer (CT) performance under distorted waveform conditions is usually characterized by means of the frequency-response test. In this paper, a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase-angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency-response approach for the e…
Transverse flux generators a solution for stand-alone wind mill
2015
The transverse flux generator (TFG) proposed in the paper as a solution for stand-alone wind electric power plants has a topology derived from a reluctance one. This variant has a permanent magnet on the rotor derived for a well-known topology in literature. Consequently, the number of rotor poles becomes double compared with stator one. The paper analyses the possibility of using a multiple modules one phase structure in comparison with poly-phase topology. The costs, torque harmonic content and the different rotor poles' topology are discussed and the conclusions are useful for the plant designer.
Design optimization for the adoption of bonded magnets in PM BLDC motors
2014
The increment of the manageable power in machines where the normally adopted ferrites are replaced with bonded magnets can vary and can introduce saturation problems depending on the variations in the magnetic circuit design. The saturation of the magnetic circuit distorts the phase voltages, introducing undesired harmonics in the connection to the mains. Combined modifications of both stator poles and rotor ring of a Brushless DC motor are proposed to evaluate their impact on the increment of the manageable power and on the harmonic content. Several magnetic circuit modifications have been considered and the paper presents the results of the most reasonable solutions, obtaining significant…
A DAQ-based sampling wattmeter for IEEE Std. 1459-2010 powers measurements. Uncertainty evaluation in nonsinusoidal conditions
2015
Abstract This paper presents the evaluation of the metrological performances of a DAQ-based sampling wattmeter (DAQ-SW) for the measurement of IEEE Std. 1459-2010 power quantities in non-sinusoidal conditions. The instrument makes use of two commercial data acquisition (DAQ) boards, a non-inductive current shunt, a personal computer and a commercial software for data processing. Starting from the results of an experimental characterization of the two instrument channels with non-sinusoidal voltages and currents and a correlation analysis, the combined standard uncertainties of IEEE Std. 1459-2010 quantities are evaluated, following the approach of the ISO Guide to the Expression of Uncertai…
Comparative evaluation of pulse width modulation techniques on effective DC link voltage utilization of grid connected inverter
2016
In this paper, comparison between two different Pulse Width Modulation (PWM) techniques employed for three phase voltage source inverter (VSI) is discussed. The three phase voltage source inverter is basic topology used to supply a grid. In this paper we have design a LC filter between the inverter and the grid in order to stabilize the output voltage. The filter gives sinusoidal three phase voltage at the output of the inverter with almost zero/less harmonic distortion. A suitable PWM technique is employed to obtain the required output voltage in the line side of the inverter. The PWM generation techniques used mainly based on sinusoidal based Pulse Width Modulation (SPWM) and Space Vector…
Development details and performance assessment of a Wind Turbine Emulator
2016
This paper describes an experimental platform to emulate the static and dynamic behavior of real Wind Energy Conversion Systems (WECS). The Wind Turbine Emulator (WTE) consists of two coupled 1.5 kW squirrel-cage induction machines. The WTE calculations are performed on a PC and a DSP, both connected via USB. The total torque applied to the WTE motor is the difference of the scaled wind mechanical torque calculated on the PC, and the turbine inertia torque calculated on the DSP. An improved WTE shaft speed derivative has been used for the inertia torque calculation, which provides better results in terms of attenuation of the high-frequency harmonics present in the generator speed acquisiti…
2D harmonic analysis of the cogging torque in synchronous permanent magnet machines
2004
Presents an approach to determine sources of cogging torque harmonics in permanent magnet electrical machines on the basis of variations of air‐gap magnetic flux density with time and space. The magnetic flux density is determined from the two‐dimensional (2D) finite element model and decomposed into the double Fourier series through the 2D fast Fourier transform (FFT). The real trigonometric form of the Fourier series is used for the purpose to identify those space and time harmonics of magnetic flux density whose involvement in the cogging torque is the greatest relative contribution. Carries out calculations for a symmetric permanent magnet brushless machine for several rotor eccentricit…
An induction motor speed measurement method based on current harmonic analysis with the Chirp-Z Transform
2005
This paper presents a new method to measure motor speed by means of frequency estimation of rotor slot spectral components in the supply current of squirrel single-cage induction motors. The novelty of the method consists in the harmonic analysis of the supply current by means of the chirp-Z transform (CZT). The advantages are improved accuracy due to better spectral resolution and resolvability. Moreover, a shorter observation window is required, thus reducing errors related to nonstationary current signals. The experimental results are presented to validate the proposed method and to make a comparison with a similar method based on the fast Fourier transform (FFT).
An induction motor speed measurement based on current harmonic analysis with Chirp-Z Transform
2002
The paper presents a new method to measure motor speed by means of frequency estimation of rotor slot harmonics present in the supply current of squirrel single cage induction motors. The novelty of the method is the use of Chirp-Z Transform as supply current harmonic analysis. The advantages are an improved spectral resolution and accuracy. Moreover a shorter sampling time window is required reducing errors related to not stationary current signal. Experimental results are presented to validate the proposed method and to perform a comparison with FFT based one.