1.5 MW Cummins Diesel Genset - PeachParts Mercedes-Benz Forum

jay_bob · #22 12-13-2017, 06:21 PM

The rotating converters were used prior to the advent of electrical rectification.
In the telephone central office, they take the commercial power and turn it into -48 V dc. In the old days it was a rotary converter. Of course the modern equivalent is the rectifier.

Fun fact, they would take the 60 Hz commercial power, convert to -48 V dc with a rotary converter, and float that across the batteries. The vast majority of the switching equipment as well as the subscriber lines and trunks came from the -48 V dc. Any other voltage that was needed, such as the 90 V, 20 Hz ringing voltage, came from another dc powered rotary converter. This way everything ran off the batteries. Of course now all that is solid state rectifiers and inverters.

The modern flywheel UPSs do have a carbon fiber rotor. A co worker of mine was in the room when one had a catastrophic failure. He thought he was a dead man. Funny he was just telling me that story last night.

Solar is another animal. The residential grade solar inverters cannot output unless the utility is present, per NEC and UL requirements. Most likely for the issue you described. This upset a lot of people in the hurricane zones this fall who lost their power but their solar system survived. They found out that they could not use the solar system power to run their house unless the utility was available.