Standard 3 phase circuit can have different topologies, but most common are delta Î” (sometimes also called triangle or pi) and star (sometimes also called Y, T or wye) topology, both given in figure bellow.
Given 3 phase network can be transformed from delta to star and vice versa. Impedances between points A and B, B and C and C and A has to be preserved. Impedances are follows:
By solving above set of equations for ZA, ZB and ZC, delta-star transformation is obtained, and delta-star transformation calculation is:
With delta-star transformation, 3 phase circuit is transformed from delta to star topology with equivalent impedance.