Search

Hybrid stepper motors (HSMs) are a type of stepper motor that have both a magnet and teeth on their rotors. These actuators are used in very fields including automation and robotics. Although these motors have high torque densities, improving their performance, their torque density, and their response time is very essential and useful. The most important problem in HSMs is their heavy rotor. A weightier rotor means more rotor vibrations and oscillations for each step. Therefore, in this study two motors with new rotor structures are represented. The first one has a light cup-shaped rotor which improves motor response time and decreases rotor oscillation on each step, and the second one not only has these benefits but also has increased motor torque density noticeably, which is due to one extra teeth row on its rotor that has made it two motors in one structure, indeed. Finally, the results of these improvements are compared with the conventional HSMs performance. Comparisons proved the significant superiority of these two motors over conventional HSMs.

In this article, a new modular structure of Marx generators (MGs) based on interleaved boost converter is proposed. The converter operates in discontinuous conduction mode to generate a high-voltage pulsed power with a common low-voltage source. Unlimited stages can be added to the proposed structure to reach lower maximum voltage stress for the semiconductors or to generate several kilovolts of the output pulses, while the voltage of the semiconductors remains constant. This structure resulted in a higher pulse repetition rate, fewer semiconductor elements, and lower semiconductor voltage stress in comparison to conventional MGs. Hence, the proposed structure is applicable for and efficient in supplying plasma applications with high-voltage pulses. The theoretical foundation of the introduced converter is presented and its performance is simulated using OrCAD software. Based on the obtained results, the maximum voltage of the output pulse is 40 times the input voltage in a single-stage structure. An 80-W prototype of the proposed structure was built to validate the accuracy of the theoretical foundation and the simulation results.

The main contribution of this research is to present a modular hybrid reluctance motor (MHRM) for high-torque drive systems. The main sizes and parameters of the structure are presented. To obtain the main characteristics of the suggested HRM, a two dimensional finite element method (FEM) is used. The flux distributions at the alignment and unalignment of the rotor, flux linkage, and magneto-static torque profiles of the proposed topology are provided. In addition, the magnetic circuit model (MCM) of the introduced motor is derived, the reluctances of the machine are calculated, and the static features of the motor are attained from the MCM are compared with those of the FEM. The results are indicative of the fact that there is an acceptable discrepancy between the results of the FEM and MCM. Finally, it is shown that the HRM produces higher torque than the conventional SRM.

Recently tape wound cores are widely used in transformers for power electronics applications. The spiral structure of theses cores affects the flux distribution inside the core and causes complication of magnetic analysis. In this paper, a model based on reluctance networks method is used for analysis of magnetic flux in toroidal wound cores and losses calculation. A Preisach based hysteresis model is included in the model to consider the nonlinear characteristic of the core. Magnetic losses are calculated by having the flux density in different points of the core and using hysteresis model. Additionally a thermal equivalent circuit is applied to determine the temperature rise in transformer due to the magnetic and electric losses. A transformer for using in a series resonant converter is modeled and the results are compared with experimental measurements to evaluate the validity of the model. Comparisons show accuracy of the model besides simplicity and fast convergence.

In design of a pulse transformer, there are several conflicting objective functions that should be optimized. However, due to the high complexity, the conventional design methods cannot consider all of them simultaneously. In this paper, multiobjective particle swarm optimization is used to design a pulse transformer. This method is based on Pareto optimality. The output consists of a set of optimal solutions that the best design is selected from it. To use this optimization method, a model is developed for a pulse transformer with toroidal wound core. The model considers magnetic, electric, and thermal characteristic of a transformer. Its simple calculations make it proper for using in an optimization process. A transformer is designed and implemented for minimum rise time, temperature rise, and volume using the presented method. This transformer is compared with a transformer that has been designed by conventional methods. Measurements and comparisons show that the results are more acceptable than the results of convectional designs besides simplicity and accuracy of the method.

This paper presents the design formulas for the calculation of the leakage inductance and stray capacitance of a toroidal core transformer. An analytical approach is utilized to calculate the leakage inductance and the turn-to-turn stray capacitance based on stored magnetic energy and electric energy, respectively. In addition, the effect of frequency on the leakage inductance is studied and some modifications are applied to the calculation method to consider the skin effect. The obtained results are validated by 3-D finite element simulations. In addition, the measurements for a prototype transformer are presented as a comparison with the calculated and simulated results. The results show that the presented formulas for the toroidal core transformers have a good accuracy.

This paper presents direct power control (DPC) of three-phase current source rectifier without line voltage sensors. In this method active and reactive powers are calculated by estimating virtual flux (VF). Direct power control of CSR and virtual flux DPC that are presented before, are described briefly then the theoretical principles of this method are described. To illustrate steady state and dynamic performance of this method, a CSR is simulated in MATLAB environment and its performance under balanced and unbalanced supply is investigated. In addition, the proposed system is compared with conventional DPC method to show the excellent performance of it.

Increasing from day to day application of rectifiers in electric motor drives and due to the advances in power electronic devices and microprocessors technology, The PWM rectifiers have received more attention in industry. To improve the performance of rectifiers, new control algorithms are proposed such as direct power control (DPC). DPC is a relatively new method and it could properly control the electrical parameters of voltage and current source rectifiers. This paper investigates the performance of direct power control (DPC) method in a three-phase current source rectifier (CSR). The effects of different operation condition such as unbalanced supply voltage, voltage sag and voltage flicker on this rectifier are investigated and the simulation results (in MATLAB/SIMULINK environment) are presented.

The switching table based direct power control (ST-DPC) of three-phase PWM rectifier is analysed and an improved switching table (IST-DPC) is presented. The proposed switching schedule improves the quality of line current and results in better dynamic performances. In addition, the predictive direct power control (PDPC) of three-phase boost rectifier is presented and simulation results (in MATLAB/SIMULINK environment) are compared with those generated by ST-DPC and ISD-DPC approaches. Advantages and limitations of each control scheme are highlighted and conclusions regarding applications, quality of current waveforms and burden of calculations are presented.

Hysteresis motor is self-starting synchronous motor that uses the hysteresis characteristics of magnetic materials to make torque. There are different methods to model this kind of motor and take into account the magnetic hysteresis characteristic of the rotor hysteresis ring. In this investigation the application of complex permeability concept is implemented to model the hysteresis loop and the hysteresis loop in inclined ellipse shape is adopted. To the best knowledge of the authors, this has not been studied before. Based on this concept, simulation of hysteresis motor in conventional configuration is done in order to obtain the output values of motor using 3D Finite Element Model (FEM). This 3D finite element model has high level accuracy and gives better insight of motor performance. Meanwhile, in order to validate the simulation results an experimental set up is provided and the output values of typical motor are measured. It is shown that there is a good agreement between experimental and simulation results. i, Abolfazl Vahedi, , r, avahedi@iust.ac.ir(Corresponding author),

The switching table based direct power control (ST-DPC) of three-phase PWM rectifier is analysed in this paper. The approach for constructing switching tables used in DPC is presented and an improved switching table (IST-DPC) is proposed. The new switching schedule improves the quality of line current and results in better dynamic performances as compared with the conventional switching table (ST-DPC). In addition, the predictive direct power control (PDPC) of three-phase boost rectifier is presented, and simulation results (in MATLAB/SIMULINK environment) are compared with those generated by ST-DPC and IST-DPC approaches. Advantages and limitations of each control scheme are highlighted and conclusions regarding applications, quality of current waveforms and burden of calculations are presented.

Recently, tape wound cores due to their excellent magnetic properties, are widely used in different types of transformers. Performance prediction of these transformers needs an accurate model with ability to determine flux distribution within the core and magnetic loss. Spiral structure of tape wound cores affects the flux distribution and always cause complication of analysis. In this paper, a model based on reluctance networks method is presented for analysis of magnetic flux in wound cores. Using this model, distribution of longitudinal and transverse fluxes within the core can be determined. To consider the nonlinearity of the core, a dynamic hysteresis model is included in the presented model. Having flux density in different points of the core, magnetic losses can be calculated. To evaluate the validity of the model, results are compared with 2-D FEM simulations. In addition, a transformer designed for series-resonant converter and simulation results are compared with experimental measurements. Comparisons show accuracy of the model besides simplicity and fast convergence