In a star connection , the similar ends (head or tail)
of 3 elements are connected together to form a common point called neutral and
the other 3 ends provide three terminals.
while in a delta connection , the head of each element is connected to the tail of next element and 3 wires are taken out from the joints .
In any complex network if you can identify a delta configuration and transform it into its equivalent star configuration , or transform a star into its equivalent delta configuration , the complex circuit gets very simplified and , therefore , the transformations are of great importance.
Delta- Star Transformation
The replacement of a delta connection by an equivalent
star configuration is called delta to star transformation . It is also known as
Delta wye transformation or Delta
y transformation . Consider a delta circuit
We want to convert it into an equivalent
star-connection.
Lets assume the equivalent star will look like as shown.
Our aim is to find the values of RCA , RAB
and RBC each in terms of RA , RB
and RC .
Lets connect a voltage source V across terminals AB
in delta connection , we get equivalent resistance between A and B as
How to remember the delta to Star
conversion formulae ?
It can be seen from above that each numerator is the product of
the two sides of the delta which meet the same point in star. Therefore, remember
it as , resistance of each arm of the star is given by the product of the
resistances of the two delta sides that meet at its end divided by the sum of three delta
resistances.
Star to Delta Conversion
Here, we want to find RA
, RB and RC in terms of RCA , RAB
and RBC . For this we use the
delta-Star transformation equations.
Lets find as
How to remember the Star to delta
conversion formulae ?
It can be remembered as , equivalent delta resistance between
two points is equal to the sum of star resistances between those two points ,
plus , product of these two star resistances divided by the third star
resistance.
