The transformation is used to establish equivalence for networks with three terminals. Where three elements terminate at a common node and none are sources, the node is eliminated by transforming the impedances. For equivalence, the impedance between any pair of terminals must be the same for both networks. The equations given here are valid for complex as well as real impedances Procedures: The power supply was turned off.
And the multimeter was used to measured the equivalent resistance of the network in the previous circuit we used =21. 5a¦ The power supply was removed, we measured again the equivalent resistance =28. 4a¦ The result in step 1 is smaller than in step 2. In step 1 , the power supply has not been removed, and it consists internal resistance. As it connects parallel to the circuit, the equivalent resistance will be smaller than without parallel internal resistance.
The star-to delta or the delta –to –star transformation was used to calculate the equivalent resistance of network shown in figure 3. equivalent resistance of : The we calculate is close to step 1 but smaller than step 2. When we calculate the equivalent resistance of ,we don’t know the internal resistance of power supply and we assumed the internal resistance is zero and ignore it in calculation, so the result we calculate is similar to data with removal of power supply.