Potential transformer three phase wiring diagram. For service voltage above 600 vac potential or voltage transformers pts or vts are used to step down the voltage to a lower range that will work with a wattnode meter. Three phase systems can be three phase three wire or three phase four wire systems. Thus the flux in the core remains nearly sinusoidal. Pts are used for medium voltage services above 600 vac but also sometimes for 575 600 vac three phase three wire delta circuits.
The leg of the transformer with the missing transformer is referred to as the phantom leg. 3 phase transformer banks can introduce a phase shift between the three phase primary and the three phase secondary function of the primary and secondary winding connections. The following paragraphs describe three phase transformers which utilize the delta and wye connections. 10132003 electromechanical dynamics 4 delta delta connection three single phase transformers connected delta delta the h 1 terminal of each transformer is connected to the h 2 terminal of the next.
Next part of this article will discuss three phase transformers using the open delta and open wye connections where one of the single phase transformers making up the three phase bank is omitted. 120 208 and 240 v ac caution is required when making connections to a three phase four wire trans former secondary because of the potential damage that can be caused by accidentally connecting the high leg. Figure 3 a delta connected three phase four wire secondary transformer can provide three output voltages. The three limb core type three phase transformer is the most common method of three phase transformer construction allowing the phases to be magnetically linked.