Question

A three-phase balanced delta connected load of (4+j8) Ω is connected across a 400V, 3 – Ø balanced supply. Determine the phase current IB.

(a) 44.74∠303.4⁰A

(b) 44.74∠-303.4⁰A

(c) 45.74∠303.4⁰A

(d) 45.74∠-303.4⁰A

This question was addressed to me in examination.

Origin of the question is Three-Phase Balanced Circuits in portion Polyphase Circuits of Network Theory

Answer 1

Right choice is (b) 44.74∠-303.4⁰A

The explanation is: Taking the line voltage VRY = V∠0⁰ as a reference VRY = 400∠0⁰V, VYB = 400∠-120⁰V and VBR = 400∠-240⁰V. Impedance per phase = (4+j8) Ω = 8.94∠63.4⁰Ω. Phase current IB = (400∠240^o)/(8.94∠63.4^o) = 44.74∠-303.4⁰A.