Question 33Electricity/Electronics - Assistant Engineer70% to pass
A 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 141 VAC is produced across the secondary winding (across X1 and X2). What fault condition is indicated? Illustration El-0123
AI Explanation
The correct answer is D) A few shorted turns in the primary winding.
When a transformer is configured as a step-down transformer (480/120 VAC), a reduction in the primary winding voltage should result in a proportional reduction in the secondary winding voltage. However, if there are a few shorted turns in the primary winding, it would cause the primary winding voltage to drop more than expected, resulting in a lower than expected secondary winding voltage (141 VAC instead of the expected 120 VAC).
The other options are incorrect because an open primary winding would result in no output voltage, and an open or shorted secondary winding would not cause the observed reduction in secondary voltage.
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#31 In a series wound motor, the current passing through the field windings also passes through what component? #32 Which of the following types of DC motors is considered to produce the highest starting torque? #34 An open primary coil in a simple potential transformer will be indicated by which of the listed conditions? #35 A 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
#36 A 4160/480Y-277 VAC three phase power transformer bank as configured in figure "3" of the illustration produces the following voltages when 4160 VAC is applied across A1 to B1, B1 to C1, and C1 to A1. What condition is indicated? Illustration EL-0084 • A2 to B2: 480 VAC • B2 to C2: 0 VAC • C2 to A2: 0 VAC • A2 to N2: 277 VAC • B2 to N2: 277 VAC • C2 to N2: 0 VAC