Question 250Electricity/Electronics - Assistant Engineer70% to pass
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
AI Explanation
The correct answer is B) 120 volts.
In a three-phase step-down transformer with a turns ratio of 4:1, the secondary voltage will be 1/4 of the primary voltage. Since the primary voltage is 480 volts, the secondary voltage across terminals A2-B2-C2 should be 480/4 = 120 volts.
The other options are incorrect because:
A) 69 volts is too low for a 4:1 step-down transformer from a 480-volt primary.
C) 208 volts is the line-to-line voltage, not the line-to-neutral voltage.
D) 277 volts is the line-to-neutral voltage for a 480-volt, 3-phase system, but not the output of a 4:1 step-down transformer.
Related Questions
#248 The turns ratio of the tapped step-down transformer shown in figure "C" of the illustration is four to one and all taps are equally spaced. If 440 volts were applied between 'H1' and 'H4', what would appear across 'X1' and 'X4'? Illustration EL-0082 #249 In figure "1" 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 440 volt supply is connected to terminals "A1-B1-C1", what voltage should develop across terminals "A2-B2-C2"? Illustration EL-0084 #251 The turns ratio of the tapped step-down transformer shown in figure "C" of the illustration is four to one and all taps are evenly spaced. If 120 volts were applied to terminals 'H1' and 'H3', what would appear at 'X1' and 'X2'? Illustration EL-0082 #252 In figure "4" of the diagram in the illustration, the three phase step-down power transformer has a turns ratio of five to one. If a three-phase 4160 volt supply is connected to terminals "A1-B1-B2", what voltage should develop across terminals "A2- B2-C2"? Illustration EL-0084 #253 If the motor shown in the illustration will not start when the "off-run" switch is placed in the run position, which of the listed components should be checked FIRST? Illustration EL-0017