Just before retiring from the telco, we had installed hundreds of the -52 vdc, 3.3 kw CCS switching supplies. 6 of em per shelf, and shelves stacked in 7' tall racks. They ran at aprx 60-75% of their CCs ratings. Unlike SSB, the telco supplies ran CCS current 24/7/365. The single, small fan inside em never came on. They were completely dead quiet. Some smaller sites, like cell sites, they ran on 240 vac, single phase. On the bigger central offices, they ran on 208 vac, also single phase. I will have to check old notes. They were US made..and were $475.00 each, in qty. No clue how much noise they put out on HF bands.
If one supply in any shelf went defective, the remaining 5 x supplies took up the slack. The current was always evenly split between the supplies. They would handle extremes in incoming voltages, (like 165-300 vac) and also anything from 40-70 hz. The power factor was superb, always > .99 at any phase angle. Never had one fail, and never replaced any. One thing I did note in the manual was, for abrupt changes in load current, it took aprx 100 msecs for the switcher to react. That would not be suitable for SSB / CW modes. I have seen some hb SS amps, where a large lytic was wired in parallel with the output of the switching supply...probably for that reason.
