Use of surface impedances in a 3D FEM linear model for the calculation of zero-sequence magnetising impedances of three-phase core-type transformers

2019 ◽  
Vol 13 (3) ◽  
pp. 435-440
Author(s):  
Elmer Sorrentino ◽  
Eizuneth Balliache ◽  
Juan Carlos Burgos
Keyword(s):  
Linear Model ◽  
3D Fem ◽  
Three Phase ◽  
Zero Sequence

Electromagnetic analysis of an AC electric arc furnace including the modeling of an AC arc

2010 ◽  
Vol 29 (3) ◽  
pp. 667-685 ◽  
Author(s):  
Arash Kiyoumarsi ◽  
Abolfazl Nazari ◽  
Mohammad Ataei ◽  
Hamid Khademhosseini Beheshti ◽  
Rahmat‐Allah Hooshmand
Keyword(s):  
Electromagnetic Field ◽  
Electric Arc ◽  
Electromagnetic Analysis ◽  
Arc Furnace ◽  
Molten Bath ◽  
3D Fem ◽  
Content Type ◽  
Three Phase ◽  
Ac Arc ◽  
Different Parts

PurposeThe purpose of this paper is to present a 3D finite element model of the electromagnetic fields in an AC three‐phase electric arc furnace (EAF). The model includes the electrodes, arcs, and molten bath.Design/methodology/approachThe electromagnetic field in terms of time in AC arc is also modeled, utilizing a 3D finite element method (3D FEM). The arc is supposed to be an electro‐thermal unit with electrical power as input and thermal power as output. The average Joule power, calculated during the transient electromagnetic analysis of the AC arc furnace, can be used as a thermal source for the thermal analysis of the inner part of furnace. Then, by attention to different mechanisms of heat transfer in the furnace (convection and radiation from arc to bath, radiation from arc to the inner part of furnace and radiation from the bath to the sidewall and roof panel of the furnace), the temperature distribution in different parts of the furnace is calculated. The thermal model consists of the roof and sidewall panels, electrodes, bath, refractory, and arc. The thermal problem is solved in the steady state for the furnace without slag and with different depths of slag.FindingsCurrent density, voltage and magnetic field intensity in the arcs, molten bath and electrodes are predicted as a result of applying the three‐phase AC voltages to the EAF. The temperature distribution in different parts of the furnace is also evaluated as a result of the electromagnetic field analysis.Research limitations/implicationsThis paper considers an ideal condition for the AC arc. Non‐linearity of the arc during the melting, which leads to power quality disturbances, is not considered. In most prior researches on the electrical arc furnace, a non‐linear circuit model is usually used for calculation of power quality phenomena distributions. In this paper, the FEM is used instead of non‐linear circuits, and calculated voltage and current densities in the linear arc model. The FEM results directly depend on the physical properties considered for the arc.Originality/valueSteady‐state arc shapes, based on the Bowman model, are used to calculate and evaluate the geometry of the arc in a real and practical three‐phase AC arc furnace. A new approach to modeling AC arcs is developed, assuming that the instantaneous geometry of the AC arc at any time is constant and is similar to the geometry of a DC arc with the root mean square value of the current waveform of the AC arc. A time‐stepping 3D FEM is utilized to calculate the electromagnetic field in the AC arc as a function of time.

scholarly journals Bearingless PM synchronous machine with zero-sequence current driven star point-connected active magnetic thrust bearing

2018 ◽  
Vol 4 (3) ◽  
pp. 5-25 ◽  
Author(s):  
Daniel Dietz ◽  
Andreas Binder
Keyword(s):  
Thrust Bearing ◽  
Lateral Force ◽  
Magnetic Bearing ◽  
Synchronous Machine ◽  
Active Magnetic Bearing ◽  
Three Phase ◽  
Zero Sequence ◽  
Force Ripple ◽  
Motor Operation ◽  
Modulation Degree

Common cylindrical bearingless drives require a separate thrust bearing, which is fed by a DC supply. Here, a technique is presented, which enables the feeding of the thrust bearing by an artificially generated zero-sequence current between the two star points of the two parallel windings in the bearingless PM synchronous machine. This way, no additional DC supply for an axial active magnetic bearing is needed. It is replaced by two three-phase inverters as stator winding supply, which are needed in any case to generate torque and lateral rotor force in the motor. This examination explains the technique of adapting the electric potential of the star points in two three-phase windings of the motor. The focus is on the determination of the operating area (maximum zero-sequence current and band width). It is constrained by the bearingless motor due to torque and lateral force ripple as well as additional eddy current losses. On the other hand, the DC link voltage and the modulation degree of the inverter for simultaneous motor operation as well as the bearing inductance limit the system dynamic. It is shown that the proposed technique is applicable for a modulation degree < 0.866, taking into account that other constraints by the bearingless machine and the inverter are mainly noncritical.

A Three-Phase Model Predictive Approach for Smooth Line-Switching in Islanded Microgrids

2021 ◽  
Author(s):  
Evangelos Pompodakis ◽  
Georgios C. Kryonidis ◽  
Minas Alexiadis
Keyword(s):  
Phase Model ◽  
Positive Sequence ◽  
Distributed Generators ◽  
Three Phase ◽  
Zero Sequence ◽  
Node Network ◽  
Switching Action ◽  
Switching Method ◽  
Line Switching ◽  
Distinct Features

This paper deals with a new line-switching method that facilitates the network reconfiguration of islanded microgrids. Its distinct features include the ability to handle network asymmetries and the minimization of the line current during the switching action. This is attained by developing a sensitive-based three-phase model predictive method to determine the operating set-points of the distributed generators (DGs) that minimize the current of the candidate line participating in the switching action. These set-points correspond to the positive-sequence powers as well as the negative- and zero-sequence currents of all DGs. Furthermore, the network constraints such as voltage limits and power limits of DGs are always satisfied. Simulations are performed in a balanced 33-bus islanded network as well as in the unbalanced IEEE 8500-node network to evaluate the performance of the proposed method.

scholarly journals Effects of the Selected Point of Voltage Reference on the Apparent Power Measurement in Three-Phase Star Systems

2020 ◽  
Vol 10 (3) ◽  
pp. 1036
Author(s):  
Vicente León-Martínez ◽  
Joaquín Montañana-Romeu ◽  
Elisa Peñalvo-López ◽  
Carlos M. Álvarez-Bel
Keyword(s):  
Reference Points ◽  
Power Measurement ◽  
Electrical Network ◽  
Entire System ◽  
Voltage Reference ◽  
Energy Principle ◽  
Conservation Of Energy ◽  
Three Phase ◽  
Zero Sequence ◽  
Power Component

The phenomenon responsible for the different apparent powers measured in a subsystem of a three-phase star-configured system, based on the voltage reference point, was identified in this paper using specific components of the instantaneous powers, as a result of applying the conservation of energy principle to the entire system. The effects of the phenomenon were determined using a proposed apparent power component referred to as the neutral-displacement power, whose square is the quadratic difference between the apparent powers of a subsystem, measured using two voltage reference points. The neutral-displacement power is a component of the apparent power, which is determined using the values of the zero-sequence voltages and the line currents in that subsystem. Expressions of the proposed power were derived using the Buchholz apparent power formulations. The validation of the derived expressions was checked in the laboratory and in a real-world electrical network, using a well-known commercial analyzer and a prototype developed by the authors.

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