This toroidal autotransformer is designed to provide a combination of voltages for a variety of applications where a grounded neutral is not available to establish a common. For example, it is common practice for an irrigation consumer to ask that only the three "hot" phases from a 480/277-volt 4-wire wye transformer bank be brought out to a three-phase pump motor in the middle of a field. The same would apply if the supply voltage is 480-volt ungrounded delta where the voltages to ground are indeterminate. If there is a need for either 120 or 240 volts to be available for irrigator/utility load control or load curtailment/interruptible programs, or another device, this transformer is perfect.

By connecting the outside leads to the "hot" phases and supplying either 120 or 240 volts between the three interior taps, there is no need to use a hot phase as a common. The impedance of the windings between the taps that are used and the hot phases helps reduce available voltages and fault currents to safe levels. The transformer has convenient ¾" conduit fitting for easy external mounting through a knockout or punched hole if no room is available for interior mounting.

** It is important to leave any unused taps insulated as they will become "hot" when the transformer is energized!