4.0 Types of transformer drivesLike electrical machines, transformers arenormally operated under changeable loadwhich usually may hardly be expressed byany pattern. However, in operation there arealso some loads that take place pursuant tocertain patterns. The following typical typesof load may be distinguished.4.1 Continuous operation (S1)Transformer is loaded by a constant powerfor long enough to achieve a final maximaltemperature.
5.2 Connected windings (autotransformer)An autotransformer is a transformer in whichthe energy between windings is transferrednot only electromagnetically but also galvanically.The windings are connected electrically.The winding consists of a joint and a serialpart. It may be said that suchtransformer is 'connected sparingly'). Ratedpower of autotransformer is also calledtransitory power, unlike approximate lowertypical power which would a common twowindingtransformer have in this case. This means that the transformer of ratedpower 10 kVA may be designed on core fortypical power 5 to 6 kVA. (depending on otherrequirements of the customer)Important: Due to galvanic connection betweenthe primary and secondary, the autotransformermay not be used as so-calledprotective transformer used to reduce thenetwork voltage onto the voltage safe forpeople, e.g. From 220 V to 24 V.
Transformatorski spoj jest spoj primarnoga i sekundarnoga namota trofaznoga transformatora; spoj dvonamotnoga trofaznoga transformatora označuje se tako da se prvo navede znak spoja višega električnoga napona (za spoj u zvijezdu znak Y, u trokut znak D, u cik-cak znak Z), zatim znak spoja nižega električnoga napona (y, d i z) i na kraju.
Namely, aninterruption in grounding conductor supply totransformer could occur and the whole networkfor 24 V would achieve full voltage of220 V toward the ground.5.3 Tapped (Regulation)Transformers may also be designed with tappingrange on the primary and /or secondaryside. Tapping is used for setting (control) oftransformer supply voltage or for regulationof load voltage.Usual values of tapping are +/- 5%, +/- 10%(e.g. 230 V +/-5%) or pursuant to requirementsof the customer. Transformer is designedfor rated voltage and rated current(rated cutting), unless otherwise requested.(See Fig.-03).