JNTU B.Tech II ELEMENTS OF ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (March - 2022 - R13)

Delta to star (Δ-Y) transformation is used to simplify complex networks by converting three resistors connected in a delta configuration into an equivalent star configuration. Consider a delta network with resistors R_ab, R_bc, and R_ca connected between terminals A, B, and C. The equivalent star network consists of resistors R_a, R_b, and R_c connected to a common neutral point.

The transformation steps are as follows:

• Identify the nodes A, B, and C of the delta network.
• Calculate each star resistor by taking the product of the two adjacent delta resistors connected to the same terminal and dividing it by the sum of all three delta resistors.
• The formulas are:

To determine the values of R and V_s in a circuit, one must apply Kirchhoff's Laws or network reduction techniques. First, identify the total equivalent resistance of the circuit by simplifying series and parallel branches. Once the total resistance R_eq is found, use Ohm's Law (V = I × R) to relate the supply voltage V_s to the total current flowing from the source.

Steps for calculation:

1. Simplify all resistors in series or parallel to reduce the circuit to a single equivalent resistance R.
2. If the circuit contains multiple loops, apply Kirchhoff's Voltage Law (KVL) to each loop to establish a system of linear equations.
3. Solve the equations for the unknown current or voltage values.
4. Use the relationship V_s = I_total × R_eq to find the supply voltage if the total current is known, or vice versa.