380volt 3-phase step down transformer to 220 volt 3 phase what reading should you get from phases to earth?

Answer 1

The voltage of 3 phase is the phase to phase voltage. If you have a wye connection, the phase to neutral voltage is the phase to phase voltage divided by the square root of 3. For 220 V would have phase to neutral of 127V. You said earth. There is no relationship to the earth unless you connect part of the transformer to earth. If the secondary has a neutral which is connected to earth, then it would be 127V.