The Experts below are selected from a list of 34569 Experts worldwide ranked by ideXlab platform
Pragasen Pillay - One of the best experts on this subject based on the ideXlab platform.
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design of a novel test fixture to measure rotational core losses in machine laminations
IEEE Transactions on Industry Applications, 2012Co-Authors: Natheer Alatawneh, Pragasen PillayAbstract:The need for testing magnetic materials used in electric machine laminations and Measurements under a rotating field is of importance in machine design. In order to obtain satisfactory experimental data, the design of the Measurement Apparatus deserves particular attention. The purpose of this paper is to propose a novel design of a magnetic circuit based on the Halbach array, which generates a uniform flux density inside the test specimen for the Measurement of rotational core loss. The proposed design is simulated and prototyped, and experimental tests are performed on two different samples of M19 gauge-24 and M36 gauge-29 silicon steel at three different frequencies (60 Hz, 400 Hz, and 1 kHz). The field-metric method is used in this work to evaluate the rotational core losses.
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design of a novel test fixture to measure rotational core losses in machine laminations
Energy Conversion Congress and Exposition, 2011Co-Authors: Natheer Alatawneh, Pragasen PillayAbstract:The need for testing magnetic materials used in electric machine laminations and Measurements under a rotating field is of importance in machine design. In order to obtain satisfactory experimental data, the design of the Measurement Apparatus deserves particular attention. The purpose of this paper is to propose a novel design of a magnetic circuit based on the Halbach array, which generates a uniform flux density inside the test specimen for the Measurement of rotational core loss. The proposed design is simulated, and experimental tests are performed.
Efstratios Skafidas - One of the best experts on this subject based on the ideXlab platform.
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comparison of corrected calibration independent transmission coefficient method to estimate complex permittivity
Sensors and Actuators A-physical, 2013Co-Authors: Chathurika D Abeyrathne, P.m. Farrell, Efstratios Skafidas, Malka N. HalgamugeAbstract:a b s t r a c t The accuracy of estimation of the frequency dependent complex permittivity of dielectric materials is important for medical applications to perform in situ chemical analysis. The achieved accuracy depends on the Measurement Apparatus and the methods used for permittivity estimation. Calibrating the sensor before use is not always possible nor is it desirable. The transmission coefficient S21 method is usually used because it does not require accurate calibration of the Measurement Apparatus. In this paper we analyze the disparity, observed in the literature, in the estimated permittivity at lower frequencies when the transmission coefficient method and small embedded sensors are used to estimate permittivity. Our results indicate that the large disparity of the permittivity at lower frequencies in the transmission coefficient S21 method is caused by the fact that the method neglects the multiple reflections at the air material interfaces. Here we propose a new method, extending the transmission coefficient method, to contend with the large disparity at lower frequencies in the existing methods whilst preserving the desirable properties of the method, namely not requiring accurate calibration of the Apparatus before use. The proposed method is compared with other calibration dependent and independent methods using Ansoft's HFSS simulation software. The accuracy of these methods is then also verified using on chip coplanar waveguides (CPW) Measurements in 1-30 GHz. Results indicate that the accuracy in dielectric estimates can be improved by taking into account both transmission and reflection coefficients (multiple reflection model) and reducing the CPW metal layer thickness. Further improvement in the accuracy in this method for short CPW can be achieved if a material of known permittivity can be used as a reference.
R L Thomas - One of the best experts on this subject based on the ideXlab platform.
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determination of thermal diffusivity of low diffusivity materials using the mirage method with multiparameter fitting
Journal of Applied Physics, 1993Co-Authors: Jukka Rantala, Lanhua Wei, P K Kuo, J Jaarinen, M Luukkala, R L ThomasAbstract:A method to determine anisotropic thermal diffusivities parallel to the surface of a solid sample is presented. The Measurement method is based on the mirage effect and the data are analyzed using multiparameter least‐squares regression fitting. The specimens studied were of medium and low diffusivity: rare earths, ceramics, and polymers. Before this study, the low‐diffusivity limit for the applicability of the mirage method was about 0.02 cm2/s, and therefore this technique has not been suitable for polymeric materials. In this work the limit has been reduced to 5×10−4 cm2/s by improving the Measurement Apparatus and the data analysis method. The thermal diffusivities obtained agree with the values obtained using the flash method within ±20%. The agreement with published values is good, taking into account that for ceramics and polymers the literature gives only the correct order of magnitude due to the differences in the manufacturing process. Even though the sensitivity of the Measurement decreases wit...
Zhanjie Song - One of the best experts on this subject based on the ideXlab platform.
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Truncation Error Analysis on Reconstruction of Signal From Unsymmetrical Local Average Sampling
IEEE Transactions on Cybernetics, 2015Co-Authors: Yanwei Pang, Zhanjie Song, Xuelong LiAbstract:The classical Shannon sampling theorem is suitable for reconstructing a band-limited signal from its sampled values taken at regular instances with equal step by using the well-known sinc function. However, due to the inertia of the Measurement Apparatus, it is impossible to measure the value of a signal precisely at such discrete time. In practice, only unsymmetrically local averages of signal near the regular instances can be measured and used as the inputs for a signal reconstruction method. In addition, when implemented in hardware, the traditional sinc function cannot be directly used for signal reconstruction. We propose using the Taylor expansion of sinc function to reconstruct signal sampled from unsymmetrically local averages and give the upper bound of the reconstruction error (i.e., truncation error). The convergency of the reconstruction method is also presented.
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an improved nyquist shannon irregular sampling theorem from local averages
IEEE Transactions on Information Theory, 2012Co-Authors: Zhanjie Song, Yanwei Pang, Bei Liu, Chunping HouAbstract:The Nyquist–Shannon sampling theorem is on the reconstruction of a band-limited signal from its uniformly sampled samples. The higher the signal bandwidth gets, the more challenging the uniform sampling may become. To deal with this problem, signal reconstruction from local averages has been studied in the literature. In this paper, we obtain an improved Nyquist–Shannon sampling theorem from general local averages. In practice, the Measurement Apparatus gives a weighted average over an asymmetrical interval. As a special case, for local averages from symmetrical interval, we show that the sampling rate is much lower than that of a result by Grochenig. Moreover, we obtain two exact dual frames from local averages, one of which improves a result by Sun and Zhou. At the end of this paper, as an example application of local average sampling, we consider a reconstruction algorithm: the piecewise linear approximations.
K Meehan - One of the best experts on this subject based on the ideXlab platform.
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high voltage capacitance Measurement system for sic power mosfets
Energy Conversion Congress and Exposition, 2009Co-Authors: Parrish Ralston, Tam Duong, Nanying Yang, D Berning, Colleen E Hood, Allen R Hefner, K MeehanAbstract:Adequate modeling of a power Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is dependent on accurate characterization of the inter-electrode capacitances. With the advent of high-voltage silicon carbide (SiC) power MOSFETs, it has become important to develop a Measurement system that can perform and record high-voltage capacitance versus voltage Measurements on these devices. This paper describes a Measurement Apparatus that safely and accurately allows high voltage capacitance-voltage (CV) Measurements to be performed. The Measurements are based on conventional LCR (Inductance (L), Capacitance (C), and Resistance (R)) meter CV techniques but with added circuitry to interface the LCR meter to high voltage bias sources. The effects of the added circuitry are studied theoretically, and the CV Measurement accuracy is verified with experimentation. High voltage capacitance voltage Measurements are presented for both silicon and SiC power MOSFETs.