An alternative to a zig zag transformer is a delta-wye transformer. These electric transformers are a more popular choice because they are better known as well as at times being less expensive than zig zag transformers; however, zig zag transformers have lower internal impedance and can be more effective in certain applications than delta-wye transformers.
Zig zag transformers have earned their name from the zig zag design of their winding. Consisting of six coils on three separate cores, zig zag transformers have a primary winding but do not have a secondary winding. The windings for each phase of a zig zag transformer come in two halves. Thus, the difference in winding patterns results from the way in which the two halves of the windings interconnect while connecting the coils and the core.
On each core, there are two coils. The first coil is connected to the second coil through the windings, of which there are two for each phase. Thus the outer and inner windings are wound onto the same core, but they are wound in opposite directions. While the first coil on each core is connected to the second coil on the next core, the second coils are all wound together and create the neutral. Since the phases are connected to the first coils, every phase is connected to every other phase, resulting in the voltages being canceled out. In order to provide earthing to ungrounded systems, a resistor is normally inserted between the neutral point of the transformer and the ground in order to limit the ground fault current and its effect on the system.