Page 208 - Basic Electrical Engineering

To remember this expressions of R , R , and R let us look at Fig. 2.122 (a)
1
2
3
again. The star equivalence of delta-forming resistances can be shown
through dotted lines. The value of R is equal to the product of the two
1
resistances of delta touching point A, i.e., R and R divided by the sum of
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31
all the delta-forming resistances, i.e., sum of R , R , and R . Similarly the
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12
23
values of R and R can be remembered.
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3
2.9.2 Transforming Relations for Star to Delta

Now let us consider star to delta transformation as shown in Fig. 135. The

basic equations guiding the conversion from delta to star remains the same in
this case also. As such we can use eqs. (1), (2), and (3). Solving eqs. (1), (2),

and (3) we got eqs. (5), (6), and (7).
Multiplying eq. (5) by eq. (6),

Figure 2.123

Multiplying eq. (5) by eq. (7),