Influence of the catalyst preparation on properties of chromium-magnesium catalysts for freon 125 synthesis

The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested

Influence of the catalyst preparation on properties of chromium-magnesium catalysts for freon 125 synthesis

The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested

Principles of modeling transformer transients taking into account topology and magnetic core features

A method describing processes in cold-rolled steel and reproducing dynamic hysteresis loops in certain core components (legs and yokes) is proposed. A method that takes into account magnetic fluxes in a nonmagnetic medium that makes the transformer model reversible is described. Transients initiated by sub-sequent energizing of a three-phase group of four-limb transformers in a 500-kV network are simulated

Transient modeling principles of transformer taking into account topology and properties of the core

A method of describing processes in cold-rolled electrical steel is proposed, which reproduces the dynamic hysteresis loops in core legs and yokes. A method of accounting for magnetic fluxes in nonmagnetic medium which makes the transfomer model reversible is described. The model developed is illustrated by calculating inrush current produced by subsequent energizations of three-phase bank consisting of four-limb transformers

Topological transient models of three-phase, three-legged transformer

The paper further develops a modeling concept of three-phase, three-legged transformer with tank walls represented as a distributed parameter structure. The circuital models proposed replicate accurately all possible zero-sequence impedances and losses of a three-winding transformer. Several model versions are compared to each other and to a conventional topological model with respect to their transient behavior during inrush and short circuit events, and in the presence of geomagnetically induced current (GIC). It was found that in all the cases considered, except that with a large GIC, all the models yield similar results. The reliability of the models is due to the representation of the tank walls behavior in a physical way, allowing one to observe the field distribution over the wall thickness as a function of transformer excitation. The modeled results are in a close agreement with positive and zero sequence data measured on a 25 MVA transformer as well as with inrush current test on a 300 kVA unit