Question

A symmetrical three-phase, three-wire 440V supply is connected to star-connected load. The impedances in each branch are ZR = (2+j3) Ω, ZY = (1-j2) Ω, ZB = (3+j4) Ω. Find ZBY.

(a) (-5.22+j0.82) Ω

(b) (5.22-j0.82) Ω

(c) (3.8-j0.38) Ω

(d) (-3.02+j8) Ω

This question was posed to me in an online interview.

My query is from Star to Delta and Delta to Star Transformation in division Polyphase Circuits of Network Theory

Answer 1

The correct choice is (b) (5.22-j0.82) Ω

Easiest explanation: ZBY = (ZRZY + ZYZB + ZBZR)/ZR

= (5.22-j0.82)Ω.