HARMONIC DISTORTION IN 3-PHASE LOADS SUPPLIED BY TWO SINGLE PHASE TRANSFORMERS.

Many utilities find it both convenient and economical to supply three phase power to small consumers, from an open-delta distribution transformer. However, rectifier failure and associated problems in equipment power supplies have recently been attributed to this type of transformer connection. This paper presents the results of an evaluation of the existence and severity of consumer problems arising from the open delta connection. It describes both theoretical and laboratory investigations of the presence of distortion in magnitude, phase angle, and waveshape of the voltage and current waveforms. The results show that, although there are some conditions under which the open delta connection should not be used, the connection is, in general, suitable for supplying most consumer loads.