Delta Service

A three phase delta service hookup normally provides 240 or 480 volts as three phase voltage and 120 or 240 volts as single phase voltage. A three phase delta service is commonly used to supply loads in which the three-phase load requirement is much larger than the single-phase load.

Thee-Phase Transformers PictureDelta systems may be center tapped, corner grounded, or open depending on the type of load served and the required service voltages. The center tapped delta system is used when single phase as well as three phase power is needed. This system produces two separate single phase voltages. The higher single phase voltage is referred to as the high leg because it is higher than the normal single phase voltage. If an electrician connects single phase equipment to the high or wild leg accidentally it will burn out because of the higher voltage.

The corner grounded delta service is used primarily for supplying large pumps, for instance oil and irrigation well services. The corner grounded delta gets its name from the location of the ground connected to one corner of the delta arrangement.

Two single-phase distribution transformers can be used to supply an open delta service where one phase of the delta is "missing" or "open". This arrangement provides three-phase service for small three-phase loads within rural, residential or light commercial areas.