Question 35Electricity & Electronics - Assistant Engineer
70% to passA 480/120 VAC step-down control transformer is configured as shown in figure "E" of the illustration. When 480 VAC is applied to the primary winding (across H1 and H2), an output of 89 VAC is produced across the secondary winding (across X1 and X2). What fault condition is indicated? Illustration EL-0123
The correct answer is A) A few shorted turns in the secondary winding. When a step-down transformer is configured as shown in figure "E", the output voltage across the secondary winding (X1 and X2) should be close to the expected 120 VAC. However, the presence of an output voltage of only 89 VAC indicates that there are a few shorted turns in the secondary winding, which reduces the effective number of turns and results in a lower than expected output voltage. The other options are incorrect because an open primary winding (B) would result in no output voltage, and an open secondary winding (C) or shorted turns in the primary winding (D) would not explain the specific output voltage of 89 VAC.
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