How does the secondary delta relate to the primary wye in a wye-delta transformer configuration?

In a wye-delta transformer configuration, the relationship between the secondary delta and the primary wye involves a phase difference of 30 degrees. In this arrangement, the primary side is connected in a wye configuration, and the secondary side is connected in a delta configuration.

The wye (Y) configuration's phase voltages are 120 degrees apart, and when stepping down the voltage to the delta (Δ), the phase currents and voltages transform accordingly. Specifically, the delta connection lags the wye connection by 30 degrees due to the nature of how phase shifts occur in these configurations.

This phase shift can be attributed to the way that voltages interact in the transformer. The line-to-line voltage in the delta configuration is related to the line-to-neutral voltage in the wye configuration, resulting in a 30-degree lagging phase angle. Therefore, when considering the electrical characteristics and transformations between these configurations, it is accurate to state that the secondary delta lags the primary wye by 30 degrees.