Transient electromagnetic field, losses and forces in a synchronous turbogenerator rotor

Abstract

Purpose -The paper seeks to present a methodology of computer simulation of 3D transient electromagnetic fields, losses and forces due to negative sequence currents in fragments of large synchronous turbogenerator rotors. The methodology allows for the preparation of initial data for further computations of thermal and mechanical behaviour of rotors. Design/methodology/approach -The governing equations for 3D negative sequence transient electromagnetic fields with the Coulomb gauge using magnetic vector potential and scalar electric potential A, V -A are solved by the nodal finite element method in a Cartesian coordinate system moving synchronously with the rotor. Findings -The presented methodology of 3D transient electromagnetic phenomena computation seems to be effective because the electromagnetic field in the rotor of a synchronous generator is generally three dimensional, and therefore 2D field-computation approaches and software are not able to simulate intrinsically 3D electromagnetic processes in turbogenerator rotors. Research limitations/implications -Currently it is difficult to carry out accurate numerical simulation of 3D transient electromagnetic fields and therefore losses and forces within the whole structure of the rotor because of the resulting huge computational expenses. This paper is devoted to the finite element analysis of electromagnetic fields, losses and forces in separate structural parts of the rotor. As an example of practical utilization of the developed technique, the computer simulation of electromagnetic phenomena in junctions of nonmagnetic rotor slot wedges of a 300 MVA class synchronous turbogenerator is carried out. Practical implications -The methodology can successfully be used during the design process of modern large synchronous turbogenerators. Originality/value -This paper presents numerical analysis of intrinsically 3D transient electromagnetic phenomena in large turbogenerator rotors.

Finite element modeling and identification of metallic materials step responses

“…Hence we applied targets in our simulations assuming the same axial symmetry, which allows for the reduction of the model to two dimensions (2D), namely the radial and axial dimensions. The model was represented as a 2D axial symmetric transient finite element model in the Ansys Maxwell software package (Pantelyat et al, 2013). As compared to the 3D model, a finer mesh could be defined using less hardware resources, thus the discretization error could be lowered.…”

“…Besides the single-frequency measurement chain, numerous methods are emerging to exploit the time domain response of objects to be detected by means of single-pulse or repetitive excitation and time dependent analysis of an induction signal captured by a coil or differential coil systems (Pantelyat et al, 2013;He et al, 2010). Transient analysis (Gopal, 2006) provides more detailed information about the target material and target distance compared to the single-frequency harmonic analysis and it may lead to the design of smart sensors with particular properties of material independent or material selective proximity sensing.…”

Influence factors to affect eddy current loss of damper winding in 24 MW bulb tubular turbine generator

“…Eddy current losses will cause the temperature to rise in rotors (Riley and Michaelides, 2006), and it will affect the security and stability operation of generator systems. Rotor eddy current loss is one of the main losses in the generator (Pantelyat et al , 2013). To reduce current loss of eddy current, the pole core in most hydro-generators commonly uses the stacking form of magnetic steel plates.…”