What is the capacity of the center tap on a 240 delta connection with one phase tapped?
A. This is one of the most common transformer application questions. If the transformer is a SolaHD T5H series the tap is full capacity, but we must define what full capacity means on one phase of a three phase transformer. A three phase transformer built by Hevi-Duty in a ventilated enclosure (standard construction on 15 KVA and above) has a per phase capacity equal to 1/3 of the nameplate rating. Therefore, the tapped phase of a T5H30S has a total capacity of 10 KVA (1/3 of 30 KVA). The 120 volt tap is at the center of this 240 volt winding so the capacity is 5 KVA on either side of the tap (X1 to X6 and X3 to X6).
