Transform from Delta (Δ) to Star or Wye (Y)
Let consider the network shown in figure below and supposed the resistances (RAB, RBC, & RCA) in Δ network are identified. Our trouble is to find the values of RA, RB, & RC in Wye (Y) network as shown in figure below that will generate the similar resistance whenever measured among similar pairs of terminals. We write the equivalence resistance among any two terminals in the form below as follows.
 to Star or Wye (Y).png)
 to Star or Wye (Y) 1.png)
Subtracting the above equations, we can write and state for unknown resistances of Wye (Y) network as:
 to Star or Wye (Y) 2.png)