General 3D Analytical Method for Eddy-Current Coupling with Halbach Magnet Arrays Based on Magnetic Scalar Potential and H-Functions

Rapid and accurate eddy-current calculation is necessary to analyze eddy-current couplings (ECCs). This paper presents a general 3D analytical method for calculating the magnetic field distributions, eddy currents, and torques of ECCs with different Halbach magnet arrays. By using Fourier decomposition, the magnetization components of Halbach magnet arrays are determined. Then, with a group of H-formulations in the conductor region and Laplacian equations with magnetic scalar potential in the others, analytical magnetic field distributions are predicted and verified by 3D finite element models. Based on Ohm’s law for moving conductors, eddy-current distributions and torques are obtained at different speeds. Finally, the Halbach magnet arrays with different segments are optimized to enhance the fundamental amplitude and reduce the harmonic contents of air-gap flux densities. The proposed method shows its correctness and validation in analyzing and optimizing ECCs with Halbach magnet arrays.

Universal calculation method for optical reflection characteristics of dihedral reflector with lambert surfaces as per radiative balance method

Object and purpose of research. This paper discusses the ways to improve current calculation method for reflection parameters during remote laser detection and ranging by means of a dihedral reflector with Lambert surfaces equal to reflection coefficients of each surface as per the generalized method of radiative balance. The study also discusses the evolution of optical methods and analytical research tools in this domain, as well as laser signature calculation for various ships and other structures. Materials and methods. Analytical calculation methods, software, calculation methods for remote laser detection and ranging taking into account optical parameters and reflection coefficient of dihedral reflectors used to calculate laser signature of ship structures. Main results. Improved efficiency and accuracy of calculation methods for laser detection and ranging with respect to dihedral reflectors for surface ships. Conclusion. Calculation methods of remote laser detection and ranging suggested in this paper offer additional capabilities in lidar signature measurements of ships and other structures.

Calculation Method of Allowable Continuous Current for Direct Burial Laying HVDC Underground Cable

The calculation of the continuous allowable current of an underground cable is determined by various characteristics. To calculate the allowable current in cables with alternating magnetic fields such as AC, special phenomena such as the proximity effect and skin effect must be applied. However, there are no standards or research related to the calculation of the continuous allowable current of a DC power cable that does not have an alternating magnetic field. In this paper, a quantitative DC cable continuous allowable current calculation formula of direct burial laying was derived by applying the existing AC cable continuous allowable current calculation method to the DC system. We developed a calculation tool that can calculate the continuous allowable current of DC cables using the derived formula. Assuming the cable conditions (cable specification, laying conditions, soil characteristics, arrangement, and number of strands, etc.), a continuous allowable current simulation of DC cables was performed. In addition, the level of contribution to the continuous allowable current value was analyzed by classifying the parameter categories into major and minor factors in the order of influence on the allowable current among the determined calculated parameters. As a result, the effectiveness of the DC cable continuous allowable current calculation tool derived by performing the allowable current calculation simulation was evaluated, and the allowable current calculation method of the HVDC cable was established.

Simulation and Experiment Analysis of 10 kV Flexible Grounding Device

The traditional 10 kV distribution network grounding system has some disadvantages, such as small grounding current and poor arc extinguishing effect, thus, hindering the detection of high-resistance grounding fault. Therefore, this paper studied the flexible grounding system consisting of small-resistance and active inverter in parallel. The control system comprises the compensation current calculation module, the fault detection module, and line protection strategy. During a single-phase grounding fault, the device is designed to inject a current of a given amplitude and phase into the neutral point to effectively suppress fault-point voltage and current and, meanwhile, quickly identifying the fault line or the busbar fault and then systematically protecting the distribution line. In addition, a large number of simulations have performed based on three grounding faults (metal, low-resistance, and high-resistance) and two modes (ungrounded and small-resistance grounding). The device can all be functional. Finally, a 400 V-level experimental prototype was built, and the experimental results are consistent with the simulation results, which can verify the effectiveness and feasibility of the flexible grounding device.

Nonlinearity Analysis of Quantum Capacitance and its Effect on Nano-Graphene Field Effect Transistor characteristics

A simple, compact, and fundamental physics-based quasi-analytic model for Single layer graphene field effect transistors (GFETs) with large area graphene is presented in which the quantum mechanical density gradient method is utilised. The basic device physics of the two-dimensional (2D) graphene channel is studied analytically. This modeling leads to the precise drain current calculation of the GFETs. The drain current calculation for GFETs starts from charge carrier concentration, its density of states and quantum capacitance(QC). QC depends on the channel voltage as a function of gate to source voltage Vgs and drain to source voltage Vds primarily. The formulation of the drain current with velocity saturation has been done by the Monte Carlo simulation method. The performance of the analytical GFETs model is present the precise values of QC, its impact on drain current and transfer as well as output characteristics. The impact of QC at nanometer technology adds the nonlinearity to characteristics curves. The proposed method provides better results as compared with the previous analytical and simulated results.