Papers by Author: Ivan Yatchev

Abstract: The paper presents a computer model, developed in the software programme Comsol, for studying the influence of the ventilation apertures on low voltage (LV) switchboard heating. Results have been obtained, concerning the distribution of the LV switchboard thermal field and air velocity field in cases of closed LV switchboards and switchboards with ventilation apertures both at natural and forced ventilation. The influence of the ventilation apertures location, as well as of the air velocity at forced ventilation, on heating the current carrying circuits in the LV switchboard has been studied.

Abstract: The electromagnetic field of the active part of oil-immersed transformers 160kVA and 630kVA has been modelled in the present paper. Finite element method and ANSYS program have been employed for the field modelling. Based on the created model, the field distribution with values of the magnetic flux density has been obtained, as well as the Joule losses have been calculated. Two variants of the model - with and without tank are studied and compared.

Abstract: Three-dimensional finite element method has been used for modelling of the magnetic field and computation of the electromagnetic force of recently developed permanent magnet linear actuator. The actuator is subject to specific requirements – having four stable positions without supply and maintaining minimum static force during the whole working stroke. The actuator consists of several cores with coils placed on a common yoke and a moving permanent magnet. It is intended for needle driving in a knitting machine. Influence of different factors on the static force characteristic is estimated.