This may seem a trivial problem but has bugged me since some time. I am working on a microcontroller based power supply for variable load upto 3kW. I have 3600uF capacitor to supply 300Vdc from 208Vphase-phase (three phase).

What I have noted is that as the load is increased, the DC voltage across capacitor begins to drop from 300Vdc to nearly 270Vdc at maximum load (30Vdc drop). The phase ac voltage seems constant

(1) Has the voltage dropped across the bridge rectifier? But its datasheet says maximum drop that can occur is only 1.6V! By the way, do I set multimeter readings for AC reading or DC reading to measure across from the phase AC terminal to DC terminal?
(2)I charge the capacitor by ramping up throuh a variac (to avoid inrush). Can I directly plug in? Wil high inrush destroy the capacitor (set up for 450V)?

Thanks