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Which, among the following is the correct expression for star-delta conversion?(a) R1=Ra*Rb/(Ra+Rb+Rc), R2=Rb*Rc/(Ra+Rb+Rc), R3=Rc*Ra/(Ra+Rb+Rc)b)(b) R1=Ra/(Ra+Rb+Rc), R2=Rb/(Ra+Rb+Rc), Rc=/(Ra+Rb+Rc)(c) R1=Ra+Rb+Ra*Rb/Rc, R2=Rc+Rb+Rc*Rb/Ra, R3=Ra+Rc+Ra*Rc/Rb(d) R1=Ra*Rb/Rc, R2=Rc*Rb/Ra, R3=Ra*Rc/RbThis question was posed to me in an online interview.I'm obligated to ask this question of Star Delta Transformation topic in division Network Theorems of Basic Electrical Engineering

Answer»

The CORRECT option is (c) R1=Ra+Rb+Ra*Rb/Rc, R2=Rc+Rb+Rc*Rb/Ra, R3=Ra+Rc+Ra*Rc/Rb

Explanation: After converting to delta, each delta CONNECTED RESISTANCE is EQUAL to the sum of the TWO resistance it is connected to+product of the two resistances divided by the remaining resistance. Hence R1=Ra+Rb+Ra*Rb/Rc, R2=Rc+Rb+Rc*Rb/Ra, R3=Ra+Rc+Ra*Rc/Rb.



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