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The commutation torque ripple adversely affects the performance of the six-phase inverter of the BLDC motor with trapezoidal back EMF and creates vibration and noise for industrial applications. In this paper, the motor model is obtained in non-commutation times and during the commutation period, and according to that, a suitable method to reduce the torque ripple, by equalizing the slope of the current disconnected from the motor and the slope of the current connected to the motor during commutation, is presented. At low speeds, torque ripple is reduced using predictive pulse width modulation technique. With this method, the duty cycle of the switch involved in the commutation is predicted and applied to the switch during the commutation intervals. At high speeds, this reduction is done using quasi z-source converter and selector circuit. The quasi z-source converter and the selector circuit increase the input voltage of the inverter during commutation intervals and increase its value to four times the back EMF voltage of the motor, thus reducing the torque ripple at high speeds. The theoretical and analytical results are verified using the simulations performed in the PLECS software. [ABSTRACT FROM AUTHOR]

Single-phase rectifiers are one of the most practical instruments with various applications. Among them, active front-end (AFE) rectifiers are introduced with bidirectional power transfer capability for power factor correction and the elimination of current harmonics. This paper proposes an adaptive model predictive control (MPC) for a single-phase AFE rectifier. The AFE topology used in this paper is a half-bridge boost converter. This topology has higher efficiency than other single-phase AFEs due to the fewer number of active semiconductor devices. Considering the presence of one leg of capacitors in this topology, balancing the voltages of these capacitors is a challenge, along with other control objectives. Also, this paper benefits from an MPC approach by which the switching signal for every switching state is chosen such that the defined cost function is minimized in the operation state to achieve all control goals based on the predefined model of the rectifier. Furthermore, an adaptive algorithm for the inductor current estimation is presented to robustify the control system against any unwanted disturbance in the control system. As a demonstration of the superior performance of the proposed method, a 1kW rectifier setup with 700Vdc output voltage fed from a 230Vrms/50Hz grid is built in the laboratory. The applicability of the MPC controller is verified and all operation waveforms of the test setup are presented. The proposed method offers a high-quality input current with total harmonic distortion (THD) below 5% and a high-power factor (PF) close to one. Also, the efficiency is comparable with the available commercialized rectifiers. [ABSTRACT FROM AUTHOR]

In this paper, the Hunger Games Search (HGS) optimization algorithm is used to estimate the electrical parameters of the induction machine steady state model. Induction machine nameplate data is used as input to the proposed algorithm. The performance of the proposed method is confil'med by comparing the output characteristics obtained by estimating the motor parameters including torque, current and power factor in the steady state model of the induction machine with the values provided by the manufacturer. In addition, by evaluating and comparing the results of the proposed method with the results of previous research, it is shown that the proposed algorithm is a very effective and accurate method for the acceptable estimation of induction machine parameters. [ABSTRACT FROM AUTHOR]

In this paper, to estimate the parameters of a three-phase induction motor, the current measured in one phase and Harris Hawk's optimization algorithm (HHO) as well as the recently introduced improved technique of this algorithm (IHHO) are used. This method includes estimating the electrical equivalent circuit parameters of a three-phase induction motor, including rotor and stator resistance, leakage inductance, magnetizing inductance, as well as mechanical parameters including the moment of inertia and friction coefficient. As three-phase induction motors are widely used in various industries, it is necessary to identify their parameters to implement adjustable speed control systems for such motors. Therefore, it is necessary to develop appropriate algorithms to accurately estimate the induction motor parameters. The main inspiration of the proposed method is the behavior of the Harris hawk group in nature. The objective function is defined as the calculation of the least mean squares of the error resulting from the numerical simulation of the dynamic equations of the motor and the measured value of the current of one motor's phase. The proposed method is applied to the dynamic model of a specific motor and the results of the proposed method are compared with other previously published methods. The obtained results demonstrate the remarkable capability of the proposed method and its rapid convergence. [ABSTRACT FROM AUTHOR]

The plasma limiter (PL) is a suitable method to protect electronic devices from high-power electromagnetic pulses. The $S$ -band PL has target specifications of 100 kW of power handling capability, < 100 ns of response time, and < 0.5 dB of insertion loss. Carbon nanotube (CNT) can be used to reduce power losses and instrument corrosion under frequent electromagnetic attacks. This article used CNT-coated copper needles in a PL to increase the electric field for the rapid breakdown process. Furthermore, the impact of dimensional parameters (needle’s length, needle’s radius, and axial displacement of the needles) were investigated. The experiment was conducted at 1800 W of peak power and 25 ns of the $S$ -band (2.45 GHz) microwave duration. In this case, the height of 19 mm and diameter of 1 mm were found to be the optimal needle parameters, in which the fastest breakdown of the electric field is available. The finite-element method was used by CST software to verify the experiment results. The transmission losses were < 5% in the normal state. The breakdown electric field threshold was ~431 kV/m near the atmospheric pressures. There was an error of < 1.28 in the case with the lowest compatibility. [ABSTRACT FROM AUTHOR]

This article proposes a method to design a three-stage induction coilgun system using the finite-element method (FEM). The system is designed to launch a 21.5 kg projectile. The method which is used to calculate the mutual inductance and the mutual inductance gradient between the two coils is expressed. Furthermore, the variation of mutual inductance and its gradient with respect to the distance between the two coils is indicated. The system parameters (i.e., coil currents, mutual inductance, mutual inductance gradient, force, velocity, and magnetic field distribution) are calculated and analyzed utilizing ANSYS Maxwell software. To verify the performance of the initial design, its analytical model is developed and validated in MATLAB software. The results of the analytical model are compared with the results obtained from the FEM method, and it is shown that they are well-matched in all waveforms. Besides, the efficiency of the system is improved through optimization by applying a genetic algorithm (GA). In this way, the efficiency of the system is enhanced from 29% to 36.6% and also the muzzle velocity is increased from 128 to 143 m/s. This method can be used to design a large-scale multistage induction coilgun (MSIC) for launching massive projectiles and reach high velocities. [ABSTRACT FROM AUTHOR]

This article intends to design, simulate, and implement a dummy load coil, a very significant element, in the Loran transmitter system. In order to ensure the impedance matching, the solenoid coil is designed with an inductance range from 200 to 300 $\mu \text{H}$. Analytical and finite-element methods are deployed as the most common practice solutions to calculate and simulate the coil inductance. The results obtained from these two methods are compared, and their accuracy and effectiveness are analyzed based on the experimentally implemented coil. Furthermore, a new method is devised to calculate the inductance of the solenoid coil containing numerous wire strands. [ABSTRACT FROM AUTHOR]

In this study, a new DC--DC single-input--dual-output (SIDO) converter is proposed which is able to step up and share the input voltage between the output terminals with constant duty cycle for whole ranges of duty cycles. Due to the fact that the voltage stresses on the semiconductors of the proposed converter are considerably low, the proposed converter can be applied in both low- and high-power applications. This topology can be used instead of two boost converters, which have very improved conversion ratios in comparison with the recently presented step-up converters. The proposed configuration can be used in many applications such as renewable energy sources and diode-clamped inverter in the grid-tied systems. In this paper, steady-state and small-signal analyses of the SIDO converter are presented and the simulation and experimental results are extracted and compared. In practical applications that SIDO is needed, using single-input--single-output can be a solution, resulting high cost. To reduce the costs, this study proposes a novel topology, which has reduced components and can step up the input voltage into two separate ports. Finally, a prototype circuit with 42 V input and 510 V/372 W and 730 V/381 W outputs are built to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

A magnetohydrodynamic (MHD) thruster is a type of electric motors which moves electrically conductive fluids without any mechanical moving parts. In this study, a linear-type MHD thruster is compared with a helical-type MHD thruster that has the same channel length and volume. For this purpose, two analytical models are used to predict the behaviors of these two types of marine MHD thrusters. The analytical model used for the helical thruster is validated by comparison to the experimental data obtained by other researchers. To validate the analytical model used for the linear thruster, a thruster prototype is manufactured and tested. The results show that although the solenoid magnet of the helical-type thruster is much easier to get a higher magnetic flux density than the saddle-shaped magnet of the linear-type thruster, the efficiency and propulsion force density of the linear-type thruster are much better than those of the helical-type one. Therefore, the linear-type thrusters cannot be ignored simply because of the complexity of their coils. [ABSTRACT FROM AUTHOR]

In this study, two high voltage gain active Z-source dc/dc converters are proposed, which are suitable for renewable energy applications. The complete analyses of the proposed structures are presented and the suitable control method is proposed. The voltage and current stresses of all elements are calculated. Moreover, in order to recognise the advantages and disadvantages of the proposed converters, a comprehensive comparison between the proposed dc/dc Z-source converters with conventional converters are made. The efficiency of both proposed converters and the conventional ones are also compared. In addition, the application of the proposed topologies in fuel cell vehicle is proposed. Finally, in order to verify the theoretical analyses, simulation results in PSCAD/EMTDS software and experimental results of the prototype are presented. [ABSTRACT FROM AUTHOR]

A magnetohydrodynamic (MHD) thruster is a type of electric motors which does not have mechanical moving parts and directly converts electrical energy into mechanical energy. In this study, the effect of magnetic field intensity and seawater electrical conductivity on the performance of a marine MHD thruster model is investigated using fully three-dimensional numerical simulations. For the first time, all electric, magnetic and fluid flow fields are considered in three dimensions. The effects of seawater electrolysis and end loss are taken into account in all simulations and a simple analytical model is developed to verify the numerical results. It is shown that increasing the magnetic field intensity or the electrical conductivity of the working fluid decreases the electrochemical and ohmic losses of the thruster at a specific velocity. Therefore, a higher efficiency can be achieved at higher magnetic field strengths and higher seawater electrical conductivities. Also, it is revealed the end loss of the channel increases with an increase in the electrical conductivity of the working fluid and decreases with an increase in the magnetic field intensity. [ABSTRACT FROM AUTHOR]

An Electro Magnetic (EM) launcher can be used as an experimental tool to accelerate small-mass specimens up to 300 m/s to study impact phenomena. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. For this purpose, 2-D and axisymmetric plasma models are widely used as these are less complicated and fairly available. The presented model solves the entire set of magneto hydro dynamic, including transport equations of mass, momentum, and energy along, with the vector potential form of Maxwell's equation-coupled time-varying electron energy distribution function for the novel EM launcher in axial symmetry domain. Radiation of the energy balance is calculated using the P-1 radiation method by dividing the electromagnetic spectrum into several gray bands. Simulations are performed using Comsol Multiphysics 4.2 software. [ABSTRACT FROM AUTHOR]

An EM launcher can be used as an experimental tool to accelerate small-mass specimens up to 300 m/s to study impact phenomena. A plasma armature is employed to avoid the friction produced by a sliding metal armature and, in particular, to prevent high-Z impurities from entering the tokamak. High currents are used to achieve high accelerations, resulting in high plasma temperatures. For this purpose, two-dimensional (2-D) and axisymmetric plasma models are widely used as these are less complicated and fairly available. The presented model solves the complete set of Magneto Hydro Dynamic (MHD): transport equations of mass, momentum, and energy along, with the vector potential form of Maxwell's equations to account for the electromagnetic effects. Radiation of the energy balance is calculated using the P-1radiation method by dividing the electromagnetic spectrum into several gray bands. The model has the features of predicting properties of the whole domain. [ABSTRACT FROM AUTHOR]

This paper provides a mathematical model for voltage natural balancing process in multi-phase capacitor-clamped multicell converters. The analysis leads to state-space model of the multi-phase flying capacitor multicell converters. This analytic model can be utilized to investigate the start-up and steady states of clamping capacitor voltages. To provide verification, numeric solution results for multi-phase capacitor-clamped multicell converter's analytic model in different cases are presented. [ABSTRACT FROM AUTHOR]

Excitation system of synchronous generator can help to an effective voltage control and power system stability support. In fact, for the stability improvement, this excitation system should be able to apply proper input voltage to the generator field winding. In this paper limiters and protective circuits of generator excitation system are explained. Two important types of these limiters are over and under excitation ones. The over-excitation limiter protects the generator against over-temperature caused by high field current for long time. Under-excitation limiter prevents the decrease of generator field current to the values lower than the stability margin or the thermal limit of end side of the stator core. Various models of the over and under excitation limiters have been presented in the literature. Tuning these limiters can be performed in different ways by considering the generator,s capability curves. The limiter models and their parameters tuning affect voltage stability straightly. In this research, after implementation the proper model for our case study, the tuning of limiters is obtained by analyzing well known voltage stability methods. Some simulations have been done in Matlab/Simulink to analyze the effect of the selected model and tuned limiters on voltage stability both in single and multi-machines system. Also the dynamic parameters of a real system (Bistun power plant) are used as the case study. The results issued from this study are also discussed and validate the simulations. [ABSTRACT FROM AUTHOR]

A toroidal field coil (TFC) is composed of several individual toroidal coils (ITCs), which are connected in series and distributed in the toroidal and symmetrical forms. This paper presents the analytical equations of mutual inductance and electromagnetic torque of the TFC that are applicable to Tokamak reactors. The analytical equations of translational forces, which are imposed on the ITCs of the TFC, are also discussed in this paper. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The results obtained from the numerical simulation agree with the empirical results and the virtual work theorem, which indicates the reliability of the presented equations. The behavior of the mutual inductance of the coil shows that the maximum stored energy is obtained when the electromagnetic torque is zero and vice versa. [ABSTRACT FROM AUTHOR]

In this paper, equations for the calculation of the selfand mutual inductances of the modular toroidal coil (MTC) applicable to Tokamak reactors are presented. The MTC is composed of several solenoidal coils (SCs) connected in series and distributed in the toroidal and symmetrical forms. These equations are based on Biot-Savart's and Neumann's equations, respectively. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. Comparing the results obtained from the numerical simulation with the experimental and the empirical results confirms the presented equations. Furthermore, the comparison of the behavior of these inductances, when the geometrical parameters of the MTC are changed, with the experimental results shows an error of less than 0.5%. The behavior of the inductance of the coil indicates that the optimum structure of this coil, with the stored magnetic energy as the optimization function, is obtained when the SCs are located on the toroidal planes. [ABSTRACT FROM AUTHOR]

Calculations of inductance for helical toroidal coils are of great interest to researchers since they are the basis of optimal design with target functions such as the maximization of the ratio of the stored magnetic energy with respect to the volume of the toroid or the used conductor, the elimination or the balance of stress in certain coordinate directions, and the attenuation of leakage flux. In this paper, using Neumann's equation, formulas are presented to calculate the self-inductance and mutual inductance of the helical toroidal coil in superconductivity conditions. It is shown that calculation of self-inductance is similar to that of mutual inductance if the diameter of the conductor's cross section is smaller than 9.4 of the minor radius. Comparison between experimental and empirical results with numerical results indicates that the presented formulas are highly reliable. Plotting contours for the magnetic flux density shows that a special design approach must be taken so that the coil eliminates the leakage flux. It is also shown that the optimal design of the coil to eliminate or balance the stress in certain coordinate directions requires selection of geometrical parameters from accurate inductance equations, and therefore, the use of approximate equations for this purpose is not recommended. [ABSTRACT FROM AUTHOR]

Abstract-In this paper, formulas are proposed for the self- and mutual-inductance calculations of a helical toroidal coil by direct and indirect methods at superconductivity conditions. The direct method is based on the Neumann's equation, and the indirect approach is based on the toroidal and the poloidal components of the magnetic flux density. Numerical calculations show that the direct method is more accurate than the indirect approach at the expense of its longer computational time. Implementation of some engineering assumptions in the indirect method is shown to reduce the computational time without loss of accuracy. Comparison between the experimental, empirical, and numerical results for inductance, using the direct and the indirect methods, indicates that the proposed formulas have high reliability. It is also shown that the self-inductance and mutual inductance could be calculated in the same way, provided that the radius of curvature is greater than 0.4 of the minor radius and that the definition of the geometric mean radius in the superconductivity conditions is used. Plotting contours for the magnetic flux density and the inductance show that the inductance formulas of the helical toroidal coil could be used as the basis for coil optimal design. Optimization target functions such as maximization of the ratio of stored magnetic energy with respect to the volume of the toroid or the conductor's mass, the elimination or the balance of stress in certain coordinate directions, and the attenuation of leakage flux could be considered. [ABSTRACT FROM AUTHOR]