To obtain the measured ratio for a delta-wye connected transformer, you must multiply the nameplate voltage ratio by what factor?

To obtain the measured ratio for a delta-wye connected transformer, the correct factor to multiply the nameplate voltage ratio by is the square root of three (approximately 1.73). This is because a delta-wye transformation involves a phase shift and a voltage relationship that reflects the square root of three.

In a delta-wye configuration, the line-to-line voltage in the delta is equal to the line-to-neutral voltage in the wye multiplied by the square root of three. Thus, when converting from the reference voltage (that is typically provided in the nameplate specification) for the delta configuration to the equivalent wye voltage measurement, you need to account for this relationship.

This factor accounts for the geometrical properties of the three-phase system where the phase angles create a need for the square root conversion between line-to-line and line-to-neutral voltages. Therefore, to correctly relate these voltages in a delta-wye transformer scenario, multiplying by 1.73 ensures you are deriving the correct measured voltage ratio.