Three identical resistors are first connected in a star and then in a delta configuration. The ratio of power consumption in the first combination to the second will be:

Question

Question

This question was previously asked in

ALP CBT 2 Electrician Official Paper (Held On: 23 Jan 2019 Shift 3)

Answer 1

Concept:

When resistors are connected in delta, the circuit as shown below.

F1 U.B Madhu 23.03.20 D8

Power consumed, \({W_{\rm{\Delta }}} = \frac{{3V_L^2}}{R}\)

When resistors are connected in star, the circuit as shown below.

By using star-delta conversion, the circuit becomes

F1 U.B Madhu 23.03.20 D9

Power consumed, \({W_Y} = \frac{{3V_L^2}}{{3R}} = \frac{{V_L^2}}{R}\)

Therefore, WΔ = 3WY

So that power consumed by three identical resistors in star configuration is 1/3 times of power consumption in delta configuration.