Summary of Delta-Star and Star-Delta Transformation

Table 1 shows the equivalent Star and equivalent Delta resistances.

Table .  1

Example 1: Convert the given Delta in the Fig. 1 into equivalent Star.

Fig. 2

 Solution : Its equivalent Star is as shown in the Fig. 2.

Where

R₁ = (10 x 5 )/(5 +10 + 15) = 1.67 Ω

R₂ = (15 x 10)/(5 +10 + 15) = 5 Ω

R₃ = (5 + 15)/(5 + 10 + 15) = 2.5 Ω

Fig.  3

Example 2.: Find equivalent resistance between points A-B.

Fig.  4

Solution : Redrawing the circuit,

Fig. 4(a

Fig. 4(b

        R_AB = (21 x 14)/(21 + 14) = 8.4 Ω

Example 3 : Find equivalent resistance between point A-B.

Fig.  5

Solution : Redraw the circuit,

Fig.  5(a

Fig.  5(b

R_AB = 8.4 Ω