Measurements of magnetic properties

Pokusima praznog hoda i kratkog spoja dobiveni su rezultati u skladu s teorijskom obradom ponašanja transformatora. U praznom hodu, uz vrlo nizak faktor snage, primarom je tekla samo struja magnetiziranja i transformator je transformirano napon na željenu vrijednost određenu njegovim omjerom transformacije. Pri kratkom spoju tekle su nazivne struje primara i sekundara, koje su mnogo više od struje praznog hoda, te su se namoti i spojne žice poprilično zagrijale. Zbog niskog napona kratkog spoja jezgra je bila nezasićena i odnos napona i struje bio je linearan. Gubici u oba slučaja ovise kvadratno o naponu, no ta korelacija proizlazi iz različitih razloga, objašnjenih u zaključku i u poglavlju 4. Mjerenjem ukupnih nazivnih gubitaka, koji u ovom slučaju iznose približno 160 W moguće je izračunati faktor korisnosti pri bilo kojem opterećenju. Ograničenje pri izvođenju pokusa su bili manjak vremena mogućnosti izvođenja pokusa, kako transformator nije u mom vlasništvu. Također odabir mjernih instrumenata bio je ograničen na digitalne unimetre široke primjene.Open and short circuit tests yielded results expected by the theoretical analysis of transformer behaviour. While open circuited, with a very low power factor, only a magnetising current passed through the primary winding and the transformer transformed voltage to the wanted value defined by its turns ratio. While short circuited rated current flowed through the primary and secondary windings which are much higher than the magnetising current, leading to a substantial heating of the windings and the circuit wires. Because of the low short circuit voltage the iron core was unsaturated and the voltage – current ratio was linear. Losses in both cases depended by the square of primary voltage, however that correlation arises for entirely different causes, which are explained in chapter 4. Measuring total rated losses , which in this case amount to approximately to 160 W it is possible to calculate the utility factor at any load. Limitations in performing the tests were a deficiency of time, since the transformer is not in my property. In addition the selection of measurement instruments was limited to wide application digital unimeters