Question

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

(a) 398.37∠-30⁰

(b) 398.37∠210⁰

(c) 398.37∠90⁰

(d) 398.37∠-90⁰

I have been asked this question in an online interview.

Origin of the question is Voltage, Current and Power in a Star Connected System topic in section Polyphase Circuits of Network Theory

Answer 1

Right option is (d) 398.37∠-90⁰

To elaborate: Corresponding line voltages are equal to √3 times the phase voltages and are 30⁰ ahead of the respective phase voltages. VYN = 230∠-120⁰V. VYB = √3×230∠(-120^o+30^o)V=398.37∠-90⁰V.