Loads on delta-connected transformers with mid-taps

Mid-taps on the secondaries of a 3-phase delta-connected transformer bank enable loads to be supplied simultaneously at full voltage and half voltage. Although the nonuniform loading of the different windings makes an exact determination of the maximum permissible loads difficult, equations and curves have been developed to facilitate these calculations. A rating factor is included which permits the rating of the transformer bank to be expressed in terms of the maximum current in any portion of the windings. Equations for voltage regulation with balanced loads and similar transformer units have been developed.