Zoltan Erdei

Considerations about power system grounding for different soil structure

The paper presents some considerations about power system grounding based on analytical computation, Finite Element Analysis (FEA) combined with neural network. There are studied vertical rods buried on different depth in homogenous and double-layer soil. First, the analytical solutions are compared with the numerical results for certifying the FEA settings then, different configurations for electrodes in different soil structures were analyzed and the results were interpreted using neuronal network. This approach offer solutions for any configurations in less time than FEA alone.

Utilization of Finite Elements Programs and Matlab Simulink in the Study of a Special Electrical Motor

This paper presents the study of a single-phase synchronous motor with permanent magnets (PM) using some computer programs. This motor type is used especially in household applications, and it has a low power. It is known that PM synchronous motors have a great advantage consisting in the lack of rotor losses. For this motor the starting problem has been solved performing a variable air gap under polar shoes, what determine the occurrence of the starting torque due to the fact that the axis of the rotor field created by PM in the rest position differs from the axis of the stator. First the parameters of the motor have been determined by tests and finite elements (FE) simulations, without knowing the properties of the PM. At the beginning magnetostatic FE simulations have been performed and then in magnetodynamic regime. The obtained results in the two regimes are closed. Secondly, with the determined parameters, a Matlab Simulink model has been realized (this being the final goal), and the dynamic regime of the motor has been studied. The results regarding the motor speed in starting process, the current variation, are also presented and discussed.

Frequency behavior of the residual current devices

This paper presents an experimental investigation into the operating characteristic of residual current devices when in presence of a residual current at a frequency of 60Hz. In order to protect persons and equipment effectively the residual current devices are made to be very sensitive to the ground fault current or the touch current. Because of their high sensitivity the residual current circuit breakers are prone to tripping under no-fault conditions.

Single-phase PM synchronous motor simulation with Matlab/Simulink

The permanent magnet (PM) synchronous motors have a major advantage compared to the asynchronous motors, namely that there are no losses in the rotor. As regarding the single-phase motors must be considered the possibility to obtain the starting torque. A simple and inexpensive constructive solution is the motor with tapered air-gap, which can develop a starting torque (although specific starting torque is small) in a well-defined direction, simply by powering the stator winding from the network of industrial frequency. Starting torque occurs due to the fact that the axis of the rotor field created by PM in the rest position differs from the axis of the stator because of the tapered air gap. Therefore this motor is more often used in low power household appliances. The development and the implementation in Matlab / Simulink of the motor model will be presented in this paper. The model is based on a mathematical model with lumped parameters, parameters that are determined through calculations and finite elements analysis. The motor behavior will be studied, both in stationary and dynamic operation. The accuracy of the model is verified by comparing simulation results with results obtained by measurements.

Considerations about medium voltage SF 6 switch disconnector framework design based on 3D electrostatic FEA

The paper presents some considerations regarding the framework design for a medium voltage SF6 switch disconnector based on 3D Finite Element Method Simulation. The conflict between dielectric design, at one side and technologically challenges, costs and dimensions on the other side is the main issue of this research. The analytically designed configuration is implemented in CST Studio Suite environment and the electric field intensity is evaluated in order to suggest some advises in switchgear design.

Determination of system for wireless power transfer

The wireless power transfer (WPT) is an technology from 1856, but not enough used for the moment. It is based on magnetic resonance between two or more coils. In this paper you will see a two simulations of the WPT, one made in FEMM to see the magnetic field between two coils (emitter and receiver), and other one to see how circuit work, and how the capacitor are charging, made in LT Spice.