Debabrata Roy

Fabrication and development of a novel flux-concentration type linear induction motor

This paper has reported the fabrication and development of a novel flux-concentration type linear induction motor (LIM) based on the effect of flux concentration by eddy currents. In the developed LIM, the leakage flux between the yokes is reduced and as a result more flux is concentrated into the air gap. It is observed from the calculated results using equivalent circuit parameters and the experimental results that the flux-concentration type LIM (FCLIM) has better thrust-characteristics compared to that of normal type tubular LIM.

Field distribution of a flux-concentration type linear induction motor

This paper has reported the eddy current and secondary-core flux density distributions of a flux-concentration type linear induction motor (FCLIM) based on the effect of flux-concentration by eddy currents. In the developed FCLIM, the slot leakage flux is reduced and as a result more flux is concentrated into the air gap. Thrust characteristics are also determined using the parameters of the equivalent circuit. It is observed from the calculated and experimental results that the developed FCLIM has better performance than that of the normal type tubular LIM.

Novel thermal model aided motor derating under waveform distortion

Static power converters and nonlinear loads used by industries change the sinusoidal nature of power system voltages, resulting in the injection of harmonic voltages in the power system. Due to the presence of harmonics, the total losses of the motor will increase, resulting in a higher temperature rise of motor which may not be allowed due to the faster deterioration of the motor insulating materials, thereby reducing the life-expectancy of the motor. This paper reports on the development of a novel hybrid thermal model, based on which the temperature distributions along the motor cross-section under different operating conditions can be obtained. Utilising this thermal model, the derating of the motor can be carried out more effectively.

Calculation of Passive Magnetic Force in a Radial Magnetic Bearing Using General Division Approach

This paper represents the force calculation in a radial passive magnetic bearing using Monte Carlo technique with general division approach (s-MC). The expression of magnetic force is obtained using magnetic surface charge density method which incurs a multidimensional integration with complicated integrand. This integration is solved using Monte Carlo technique with 1-division (1-MC) and 2-division (2-MC) approaches with a MATLAB programming. Analysis using established methods such as finite element method (FEM), semi-analytical method, and adaptive Monte Carlo (AMC) method has been carried out to support the proposed technique. Laboratory experiment has been conducted to validate the proposed method. 2-MC gives better result than 1-MC. The computation time of the proposed method is compared with the quadrature method, FEM and AMC. It is observed that the proposed method invites less computational burden than those methods as the algorithm adaptively traverses the domain for promising parts of the domain only, and all the elementary regions are not considered with equal importance.

Jiles–Atherton Hysteresis Approach in Analyzing the Effect of Field Suppression in Saturated Iron-core Superconducting Fault Current Limiters

Abstract Saturated iron-core superconducting fault current limiters (SISFCL) are becoming more popular in the recent years due to their ability of reliable, effective and instantaneous fault limiting. With a superior performance than conventional current limiting methods, the SISFCL is finding its application in modern transmission lines and distribution system. In the SISFCL, the iron core is forced into saturation using a superconducting coil carrying DC current. During a fault in the system, the high fluxes set up in the AC coils interact with the DC flux, thereby reducing the flux density abruptly. This sudden change in the flux density induces a high voltage across the DC coil, which may damage the DC current source as well as the superconducting material. As a protective measure, a field suppressor unit is used that disconnects the DC supply following a fault. In this paper, a mathematical model of the SISFCL is developed considering hysteresis and the effects of the field suppressor unit have been analyzed. The paper also aims to highlight the effects on the performance of SISFCL with varying hysteresis loops of the core material.

Mathematical modeling and harmonic analysis of SISFCL

Purpose A saturated iron core superconducting fault current limiter (SISFCL) has an important role to play in the present-day power system, providing effective protection against electrical faults and thus ensuring an uninterrupted supply of electricity to the consumers. Previous mathematical models developed to describe the SISFCL use a simple flux density-magnetic field intensity curve representing the ferromagnetic core. As the magnetic state of the core affects the efficient working of the device, this paper aims to present a novel approach in the mathematical modeling of the device with the inclusion of hysteresis. Design/methodology/approach The Jiles–Atherton’s hysteresis model is utilized to develop the mathematical model of the limiter. The model is numerically solved using MATLAB. To support the validity of model, finite element model (FEM) with similar specifications was simulated. Findings Response of the limiter based on the developed mathematical model is in close agreement with the FEM simulations. To illustrate the effect of the hysteresis, the responses are compared by using three different hysteresis characteristics. Harmonic analysis is performed and comparison is carried out utilizing fast Fourier transform and continuous wavelet transform. It is observed that the core with narrower hysteresis characteristic not only produces a better current suppression but also creates a higher voltage drop across the DC source. It also injects more harmonics in the system under fault condition. Originality/value Inclusion of hysteresis in the mathematical model presents a more realistic approach in the transient analysis of the device. The paper provides an essential insight into the effect of the core hysteresis characteristic on the device performance.

Performance Analysis of SISFCL with the Variation of Circuit Parameters using Jiles Atherton Hysteresis Model

Abstract In modern day power systems, fault current limiters (FCL) are used to provide protection from high fault currents in the event of electrical faults and thus help to deliver uninterrupted electric supply to the consumers. Several technologies of FCLs are available for practical usage. However, the saturated iron-core superconducting fault current limiter (SISFCL) has gained a lot of attention in recent years in view of its ability to offer very low impedance during normal operation and high impedance during faulted condition. Previous mathematical models defining the performance of the device employs a simple BH curve. But as the change in mathematical state of saturation and unsaturation is important for the operation of the device, the paper investigates the responses considering the effects of magnetic hysteresis utilising the Jiles Atherton hysteresis model. Further the performance of the device is analysed with the variations of different parameters viz., the fault resistance magnitude, DC bias current, number of turns of the AC winding and number of turns of the DC winding that portray the effectiveness of the parameters encouraging an optimal design of the limiter.

Recognition of Grouping Areas in Trademarks Considering Proximity and Shape Similarity

According to the Gestalt principals, we model features for representing the attraction degree between pairs of image regions, and, grouping areas in trademarks are recognized. This investigation would be used for content-based image retrieval systems from the view of mirroring human perception for trademark images. Depending on variability in human perception for trademark images, the proposed method finds grouping areas considering combinations of the features. We have evaluated the effectiveness of the proposed method on 36 test images of abstract trademarks from the Japan Trademark Registry. Experimental results have shown over 80% in the images have been the same as humans perception.