If three currents, equal in magnitude and phase, are applied to the three terminals, the ampere-turns of the a2-N winding cancel the ampere-turns of the b1-b winding, the ampere-turns of the b2-N winding cancel the ampere turns of the c1-c winding, and the ampere-turns of the c2-N winding cancel the ampere turns of the a1-a winding.Learn More: Why we should not give dc supply to Transformer The outer coils are connected to phases a1,b1,c1 of the existing delta system.The inner coils are connected together to form the neutral and our tied to ground.The outer coil of phase c1-c is connected to the inner coil of phase b2-N.The outer coil of phase b1-b is connected to the inner coil of phase a2-N.The outer coil of phase a1-a is connected to the inner coil of phase c2-N.Each coil has the same number of windings turns (Turns ratio=1:1) but they are wound in opposite directions. One coil is the outer coil and the other is the inner coil.As such, there would be negligible current through the neutral pole and it can be connected to ground
Each phase, therefore, couples with each other phase and the voltages cancel out. The second coils are then all tied together to form the neutral and the phases are connected to the primary coils. The first coil on each core is connected inside out to the second coil on the next core. The zigzag transformer contains six coils on three cores.Zig-Zag connection is the combination star and delta connection and it has the both advantage of a star and delta.