Delta--
Phase voltage = line voltage
Phase amperage * 1.732 = line amperage
Wye--
Phase voltage * 1.732 = line voltage
Phase amperage = line amperage
Draw your two diagrams of delta and wye, visually you can see why this is.
Write in all your numbers--You can see that in a delta that across one coil if you have 240 volts that the volts on the line will be the same.
Whereas in a wye you can see that if there is 120 volts across one coil(phase) that from line to line you are going through two coils and have to mutiply by 1.732 (not 2 because they are out of phase) to get the line voltage of 208.
Amperage in a delta gets increased because one line is hooked up to the corner of two coils. In a wye one line is hooked up to the corner of one coil only so amperage stays the same.
Hope this helps.
Remember a delta is a triangle and a wye is a Y.
