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There is probably more DC power stuff now than there has ever been at any time in history. In the past 20 years with the growth of ISPs, telecom, internet infr
by walrus01 6y ago
There is probably more DC power stuff now than there has ever been at any time in history.
In the past 20 years with the growth of ISPs, telecom, internet infrastructure stuff, a huge percentage of it runs entirely from giant -48VDC battery banks, rectifiers, bus bars, fuse panels and distribution systems. In general as you get to the size of really big important core routers, DWDM systems and such, a lot of them don't even exist in AC powered versions.
The difference is that it's normal 3-phase AC power distributed to the building, and turned into DC within it.
The origin of this is within the Bell system and other similar legacy telco equipment manufacturers (Northern Telecom, etc), all of which standardized on -48VDC power systems more than 65 years ago.
It is just not apparent to most people how common and widespread -48VDC stuff is, since unless you work at the OSI layer 1 in the telecom business, you'll rarely have a reason to lay eyes on it in person.
- londons_explore 6y ago48V DC is mostly popular because human safety laws don't require special handling of 48v. Voltages above 48v/50v normally require testing/certification/etc. 48v is basically a voltage to avoid paperwork, while still being as high as possible to avoid spending too much money on copper.
- kortilla 6y ago> 48v is basically a voltage to avoid paperwork A less cynical take is that it’s a safe voltage for people to work with.
- jeffrallen 6y agoPlease grab two terminals of a -48v system and repeat that statement.
- Goz3rr 6y agoI don't have a -48VDC power supply to test it with, but as far as I know +48VDC has the same effect. Firmly grabbing a lead with both hands results in absolutely nothing happening.
- NullPrefix 6y ago>I don't have a -48VDC power supply to test it with, but as far as I know +48VDC has the same effect. Grab the same leads of +48VDC, but switch your hands, left lead to your right hand, right lead to your left hand. You will get -48VDC.
- londons_explore 6y agoDoing it with wet sweaty hands is somewhere between "pretty painful" and "deadly". You're right that with dry non-sweaty hands, you can't even notice 48 volts.
- cfn 6y agoIt is also a multiple of 12V batteries and 2V cells so most house level off-grid solar based systems run on 48V.
- interestica 6y agoAlso, 48v for 'phantom power' on condenser mics in studio audio production has been around for decades.