Let's refresh a bit of theory Transformer Magnetizing Inrush Currents
When voltage is switched on to energize a transformer, the transformer core normally saturates.
This results in a large inrush current which is greatest during the first half cycle (approximately .01 second) and becomes progressively less severe over the next several cycles (approximately 1 second) until the transformer reaches its normal magnetizing current.
To accommodate this inrush current, fuses
are often selected which have time-current withstand values of at least 12 times transformer primary rated current for .1 second and 25 timess for .01 second. Two questions and one answer for Ichan :
1) Which is the mark stating shown in the breaker? (Please indicate model and value , C32, D32, ...)
2) Are you living in Europe? Because the nominal value of three phase voltage in Europe is 400V and your transformer is 380V rated and if in your place is near to a power grid, voltage it is even more high further increasing the inrush current.
May you measure your voltages? (L1-L2, L1-L3, L2-L3)
In a transformer the shield is used to reduce interference by reducing the stray capacitance between primary and secondary windings.
Simply connect it to the ground wire.