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Three-Phase Systems in Power Applications - Engineering

Q1:

Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 .

A single-phase 32 A; three-phase 16 A

B single-phase 16 A; three-phase 8 A

C single-phase 8 A; three-phase 4 A

D single-phase 16 A; three-phase 0 A

ANS:B - single-phase 16 A; three-phase 8 A

In the three-phase system, one phase will carry current while the remaining two phases will act as a return so current required per phase will be proportional to 8A.

In the single-phase system two-conductor will be required per phase so so current required per phase will be proportional to 16A.