▁resident ial ▁locations , ▁to ▁supply ▁three - phase ▁distribution ▁systems . ▁ ▁An ▁example ▁would ▁be ▁a ▁distribution ▁transform er ▁with ▁a ▁delta ▁primary , ▁running ▁on ▁three ▁ 1 1 ▁k V ▁phases ▁with ▁no ▁neutral ▁or ▁earth ▁required , ▁and ▁a ▁star ▁( or ▁w ye ) ▁secondary ▁providing ▁a ▁ 3 - phase ▁supply ▁at ▁ 4 1 5 ▁V , ▁with ▁the ▁domestic ▁voltage ▁of ▁ 2 4 0 ▁available ▁between ▁each ▁phase ▁and ▁the ▁earth ed ▁( ground ed ) ▁neutral ▁point . ▁ ▁The ▁delta ▁w inding ▁allows ▁third - harm onic ▁curr ents ▁to ▁circul ate ▁within ▁the ▁transform er , ▁and ▁prevents ▁third - harm onic ▁curr ents ▁from ▁flow ing ▁in ▁the ▁supply ▁line . ▁▁▁ ▁D elta - w ye ▁transform ers ▁introduce ▁a ▁ 3 0 , ▁ 1 5 0 , ▁ 2 1 0 , ▁or ▁ 3 3 0 ▁degree ▁phase ▁shift . ▁ ▁Thus ▁they ▁cannot ▁be ▁par alle led ▁with ▁w ye - w ye ▁( or ▁delta - delta ) ▁transform ers . ▁However , ▁they ▁can ▁be ▁par alle led ▁with ▁identical ▁configurations ▁and ▁some ▁different ▁configurations ▁of ▁other ▁delta - w ye ▁( or ▁w ye - delta ▁with ▁some ▁attention ) ▁transform ers . ▁ ▁See ▁also ▁ ▁Electric ▁power ▁distribution ▁ ▁High - leg ▁delta ▁ ▁M ains ▁power ▁systems ▁ ▁Motor ▁soft ▁st arter ▁ ▁References ▁ ▁External ▁links ▁ ▁Three - phase ▁transform er ▁circ uits ▁ ▁Category :