Determination of dynamic parameters of large hydro-generators by finite-element simulation of three-phase sudden short-circuit tests

This paper proposes an improvement for the dynamic performance of presaturated stacked permanent magnet biased three-phase fault current limiter (PMFCL) through COMSOL finite element simulation. The nonlinear demagnetization behavior of the permanent magnet, especially in the upper part of the B-H curve with negative magnetic field intensity, has been modelled through the Jiles-Atherton method. This enables a realistic representation of the PMFCL dynamic behavior throughout its entire operations of pre-fault, fault and fault removal, respectively. The experimental measurements have been considered to validate the trends of the simulation outcomes during the entire operation of PMFCL. Extensive finite element simulation shows that the stacked design of PMFCL can increase the capability of fault current limiting with proper selection of the number and arrangement of the AC coils around the iron core (soft magnet). Results reveal that the division of AC coils into series differential connected subcoils, with an even number, can increase the limiting capability with increasing the AC coil number of turns, without exceeding the permissible tolerances of voltage drop and power losses. Moreover, this stacked design is subjected to parametric investigation for different fault types, either symmetrical or unsymmetrical, or even when changing the fault current peak value.

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Dependancy of Three Phase Induction Motor Derating Aspects on Complex Voltage Unbalance Factor: A Calorimetric and Finite Element Simulation Study

IEEE Access ◽

10.1109/access.2021.3117375 ◽

2021 ◽

pp. 1-1

Author(s):

P. Sudasinghege ◽

U. Jayatunga ◽

P. Commins ◽

J. Moscrop ◽

S. Perera

Keyword(s):

Finite Element ◽

Finite Element Simulation ◽

Induction Motor ◽

Simulation Study ◽

Voltage Unbalance ◽

Element Simulation ◽

Three Phase

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Local Approach of Fracture in the Ductile Regime and Application to VVER Materials

10th International Conference on Nuclear Engineering, Volume 1 ◽

10.1115/icone10-22710 ◽

2002 ◽

Author(s):

B. Z. Margolin ◽

V. I. Kostylev ◽

E. Keim ◽

R. Chaouadi

Keyword(s):

Finite Element ◽

Crack Resistance ◽

Ductile Fracture ◽

Finite Element Simulation ◽

Volume Fraction ◽

Stress Triaxiality ◽

Local Approach ◽

Gurson Model ◽

Element Simulation

Within the TACIS R2.06/96 project: “Surveillance Program for VVER 1000 Reactors”, sponsored by the European Commission, the local approach of fracture has been applied in the ductile regime. Two different models were applied and compared, namely Tvergaard-Needleman-Gurson versus Prometey model. The main tasks are: • perform special Local Approach experiments on smooth and notched cylindrical specimens; • predict JR-curve on the basis of the ductile fracture models; • compare two models of ductile fracture, namely, the Tvergaard-Needleman-Gurson model and the Prometey model. In this paper, the Tvergaard-Needleman-Gurson and Prometey models are briefly described. The parameters of both models were calibrated by using experimental data obtained on tensile specimens. While only smooth tensile specimens are used to calibrate the Tvergaard-Needleman-Gurson model, notched tensile in addition to smooth tensile specimens are used to calibrate the Prometey model. In the latter, standard smooth tensile specimens are used to determine the mechanical properties (the yield stress σy, the ultimate stress σu, the ultimate elongation δu, the area reduction Z) and notched cylindrical specimens to determine the strain at rupture. The numerical analysis comprises essentially two steps: • Step 1: finite element simulation of the smooth tensile specimen (determination of true stress-strain curve and critical void volume fraction for the Tvergaard-Needleman-Gurson model) and simulation of the notched cylindrical specimen up to rupture (determination of stress triaxiality for the Prometey model); • Step 2: finite element simulation of the 2T CT specimen and determination of the crack resistance behaviour in the ductile regime (J-Δa curve). It is found that both models were able to correctly predict the crack resistance behaviour of the investigated materials. The numerical and the experimental results were in very good agreement. The main difference between the two models is that the required number of calibrated parameters in the Prometey model is less than in the Tvergaard-Needleman-Gurson model but additional tests on notched specimens are required for the Prometey model.

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