Question

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

(a) 400∠120⁰

(b) 400∠-120⁰

(c) 400∠240⁰

(d) 400∠-240⁰

This question was posed to me in unit test.

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

Answer 1

The correct answer is (b) 400∠-120⁰

Explanation: As |VYB| = |VPh|, and is displaced by 120⁰, therefore the line voltage VYB is VYB = 400∠-120⁰V. A balanced three phase, three wire, delta connected system is referred to as mesh connection because it forms a closed circuit.