Question

In a delta connected system, the voltage across the terminals R and Y is 400∠0⁰. Find the line voltage VBR.

(a) 400∠240⁰

(b) 400∠120⁰

(c) 400∠-240⁰

(d) 400∠-120⁰

I got this question in an international level competition.

This interesting question is from Voltage, Current and Power in a Delta Connected System in chapter Polyphase Circuits of Network Theory

Answer 1

Right choice is (c) 400∠-240⁰

Easiest explanation: We know, |VBR| = |VPh|, and is displaced by 120⁰, therefore the line voltage VBR is VBR = 400∠-240⁰V. Delta connection is so called because the three branches in the circuit can be arranged in the shape of delta.