Dept of Electrical & Electronics ELE 1001: Basic Electrical Technology Lecture 02 Resistance & Star-Delta Transformation ELE 1001: Basic Electrical Technology Lecture 02 Resistance & Star-Delta Transformation
Dept of Electrical & Electronics We will learn here… Fundamentals of Resistor Star & Delta connections Star-Delta & Delta-Star Transformations
Dept of Electrical & Electronics Resistors Resistance Property which opposes the flow of current R = V/I Unit – Ohms ( ) Power P = VI = V 2 /R = I 2 R Conductance Reciprocal of resistance Symbol: G Unit – Siemens (S) R V I + -
Dept of Electrical & Electronics Resistivity & Temperature Coefficient For a homogeneous material: where, ρ= resistivity, l= length & a= cross-sectional area of the material where, α 0 = Temp coefficient of resistivity at 0°C R 0 = Resistance at 0°C Positive temp coeff: Aluminum, Copper, Gold, Tungsten Negative temp coeff: Carbon, Germanium (pure), Silicon (pure)
Dept of Electrical & Electronics Resistive Circuits Resistors in parallel: Resistors in series: R1R1 R2R2 R3R3
Dept of Electrical & Electronics Current Division in Parallel Circuits
Dept of Electrical & Electronics Voltage Division in Series Circuits
Dept of Electrical & Electronics Star & Delta Connections A B C R ab R bc R ca B C RaRa RbRb RcRc A Star ConnectionDelta Connection
Dept of Electrical & Electronics Star-Delta Transformation B C RaRa RbRb RcRc A A B C R ab R bc R ca Delta to Star Transformation:
Dept of Electrical & Electronics Star-Delta Transformation contd… Star to Delta Transformation: B C RaRa RbRb RcRc A A B C R ab R bc R ca
Dept of Electrical & Electronics Example 1 For the circuit shown, determine the power supplied to the resistive network ( all resistor values are in ’s) P supplied =47.06 W
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Dept of Electrical & Electronics Example 2 Find the potential difference across 10Ω resistor. Also, find the power consumed by it. V 10Ω = 14.14V; P 10Ω = 20W
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Dept of Electrical & Electronics Summary We started with Resistance and its properties Then discussed Resistive circuits Current Division in Parallel Circuit Voltage Division in Series Circuit Star-Delta Transformation Concluded with Application of star-delta & source transformation concepts.