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 ZRY.

(a) (5.22-j0.82) Ω

(b) (-3.02+j8) Ω

(c) (3.8-j0.38) Ω

(d) (-5.22+j0.82) Ω

This question was addressed to me during an online interview.

This interesting question is from Star to Delta and Delta to Star Transformation topic in section Polyphase Circuits of Network Theory

Answer 1

Correct option is (c) (3.8-j0.38) Ω

Explanation: ZRY = (ZRZY + ZYZB + ZBZR)/ZB

= (3.8-j0.38) Ω.