In figure "2" of the diagram shown in the illustration, the three phase step down power transformer has a turns ratio of four to one. If a three-phase 480 volt supply is connected to terminals "A1-B1-C1", what voltage should develop across terminals "A2-B2-C2"? Illustration EL-0084
Official USCG Answer & Rule Citation
Correct Answer: Option B — 120 volts
Three-phase transformer secondary voltage equals primary voltage divided by the turns ratio. For a 480-volt primary supply and a 4:1 step-down ratio, secondary voltage is 480 / 4 = 120 volts between lines.
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