Testing a transformer
A 3-phase transformer, like any transformer is more naturally inclined to be an isolation transformer therefore, measuring the secondary voltages with respect to neutral may be totally meaningless because the secondaries will not normally be galvanically connected to neutral.

However, assuming they are galvanically connected AND there is no fault on the transformer, the voltages measured can only be because the secondary turns are different thus they produce 220V, 110V and 105V.

It would be wrong to have a three-phase transformer with different primary windings because the ampere-turns wouldn't be balanced and the core would likely saturate due to this.

It could also be that there is just one secondary winding and this has got tap-off points.

A picture might help.