Suggestion: The open-delta connection or V-connection is and unsymmetrical connection with is used if one transformer of a bank of three single-phase delta-connected units must be cut out because of failure. It is a connection that is sometimes resorted to as an emergency expedient or used as a temporary measure with the intention of completing the delta when condition of load warrant the addition of a third unit. The normal capacity of the open-delta bank is reduced to 57.7% of its delta winding.
Utilities often install two pole mounted transformers to provide three phase system voltage of 240V and a 120V of one of the pole mounted transformer center-tap neutral and end winding.
