Prediction of the Transformer Inrush Current Forces

When a power transformer is switched to power supply there is a transient inrush of current in each of the transformer phases. Its peak value mainly depends on the resistance of the primary winding, the point on the voltage wave at the instant of switching the transformer on, and the residual magnetic flux of the transformer. The inrush current is predicted by the time stepping 2D finite-element method (FEM) coupled with the external electrical circuit. During the switching on process the electromagnetic forces that appear as a result of inrush currents and theirs leakage magnetic fields are calculated. An experimental transformer is built and the measured results are given.
Uključivanjem transformatora na mrežu napajanja pojavljuje se u svakoj od faza tranzijentna struja uklapanja. Njezina vršna vrijednost ovisi o otporu primarnog namota, trenutačnoj vrijednosti napona u trenutku uključivanja i remanentnom magnetskom tijeku. Struja uklapanja računata je primjenom 2D metode konačnih elemenata (MKE) spregnute s vanjskim električnim krugom, u vremenskoj domeni. Elektromagnetske sile na namote za vrijeme procesa uključivanja pojavljuju se uslijed tranzijentnih struja i njihovih rasipnih polja. Mjerenja struje uklapanja provedena su na eksperimentalnom transformatoru.