3 phase 12 V step down transformer
Option 1







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A low-voltage 3-phase supply made from single-phase transformers.

Option 2

I have seen 24 V DC industrial power supplies which were 400 V primary and probably about 18 V secondaries feeding a rectifier. The rectified 3-phase supply has very little ripple so no smoothing capacitors are required. If you can find one of these you could tap in before the rectifier to get your three phases but they will be wired in delta so there will be no star / wye point for a neutral.