Three windings can be joined two ways, and the connection decides which quantity gets the $\sqrt{3}$. Fix the naming first, because everything here depends on it: line quantities, subscript L, are measured outside the machine — between two supply conductors, or in one of them. Phase quantities, subscript φ (phi), belong to one winding inside it.

In a wye (star), the three windings meet at a common neutral point. $V_{L} = \sqrt{3} \, V_{\varphi}$ — V-L equals root three V-phi — where $V_{L}$ is the line-to-line voltage in volts and $V_{\varphi}$ the line-to-neutral voltage of one winding. The current has nowhere to divide, so line and phase currents are equal. A 400 V panel is a 231 V winding three times over; a 600 V panel is a 347 V one.

In a delta, the windings form a closed triangle and each supply conductor lands on a corner where two of them meet. Now it is the current that splits: $I_{L} = \sqrt{3} \, I_{\varphi}$, with $I_{L}$ the line current in amperes and $I_{\varphi}$ the current in one winding — while line and phase VOLTAGES are identical, because each winding sits directly across two lines.

One sentence carries the whole lesson: wye moves the voltage, delta moves the current, and in both the line quantity is the larger one. Say it once at the start of an exam and you will not have to reason it out again.