Question

A symmetrical star connected system has VRN = 230∠0⁰. The phase sequence is RYB. Find VBR.

(a) 398.37∠210⁰

(b) 398.37∠-210⁰

(c) 398.37∠120⁰

(d) 398.37∠-120⁰

The question was posed to me during a job interview.

My question is taken from Voltage, Current and Power in a Star Connected System in chapter Polyphase Circuits of Network Theory

Answer 1

The correct answer is (b) 398.37∠-210⁰

The best I can explain: All the line voltages are equal in magnitude and are displaced by 120⁰. VBN = 230∠-240⁰V. VBR = √3×230∠(-240^o+30^o)V=398.37∠-210^oV.