Introduction to Electric Circuits

60 DC circuit analysis

and that

R12R23//(RI2 + R23 + R31) - R2

we obtain

R23 = R2 + R3 + R2R3/R1 (3.28)

and

R31 = R3 + R1 + R3R1/R2 (3.29)

Example 3.10

Transform the star connected resistances R~, R2 and R 3 shown in the bridged-T
network of Fig. 3.36 to a delta. Hence determine the current flowing through
the 40 11 resistor (R).

C

R

i I

R1 40~ R3

l I [" ' i o

10~ 10~

80V R2~-~5~

Figure 3.36

Solution

The diagram is redrawn in Fig. 3.37 to show the equivalent delta resistors R12,

80V

R

I I

R31 1

! I

N23

[

Figure 3.37

R23 and R31. Using the star-delta transform Equations (3.27), (3.28) and (3.29),

we have

R12 = R~ + R 2 + R1R2/R 3 - 10 + 5 + 50/10 - 20 11