Assuming that 450 VAC is the source voltage at the circuit breaker, if 450 volts AC were measured across the load as shown in the illustration as shown in figure "B" of the illustration, what would this indicate? EL-0083

Correct Answer: Option B — an open winding between the reference point "X" and the 25% tap connection

Measuring full source voltage across the load of an autotransformer indicates that the portion of the winding between the reference tap and the supply terminal is completely open, interrupting normal voltage division and placing full un-stepped line potential across the output terminals.