nanog mailing list archives
Re: Why choose 120 volts?
From: Dorn Hetzel <dhetzel () gmail com>
Date: Wed, 27 May 2009 09:28:13 -0400
The early problems with distance transmission of DC really didn't have anything to do with the inherent properties of DC current, but with the fact that, at the time, there was no good way to convert DC voltages up and down in a similar fashion to the function performed by transformers with AC. The inability to step DC up to high voltage for distant transmission was the real killer for early use of DC. Lately, very high voltage DC is actually a better performer than AC for some long distance transmission situations. In particular, DC can be used to move power between unsynchronized grids without the usual problems, and to transmit power through undersea cables, where AC capacitance losses would add up. See: http://en.wikipedia.org/wiki/High-voltage_direct_current#Advantages_of_HVDC_over_AC_transmission The main thing that has changed since the early days is that much better semiconductors are available to make the voltage conversion feasible... -Dorn 2009/5/27 Brian Raaen <braaen () zcorum com>:
As a Holder of two different FCC licenses I can tell you voltage is not what kills, it is amps and location that kill. Actually in certain cases as long at you have good electrical isolation, high enough dielectric breakdown voltage, and good grounding higher voltages can be safer and more efficient. Also, Thomas Edison was the one that discovered that trying to deliver DC more than a few feet was not a good idea. -- ----------------- Brian Raaen Network Engineer email: /braaen () zcorum com/ <mailto:braaen () zcorum com> FCC GROL (General Radiotelephone Operators License) FCC Amateur Extra Class KG4CXN (Also certified volunteer examiner with CAVAC and ARRL) Alex H. Ryu wrote:Also, adding followings. 5) availability from local power provider(s) 6) local regulation such as fire department safety rules... 7) for your own safety... (120V may not kill people, but 240V can do...) If you want better, why not just have everything to DC power ? Something like 48V... Alex Wayne E. Bouchard wrote:1) Equipment used to not be dual voltage 2) For smaller scale, 120V UPS and distribution equipment is usually cheaper 3) 120V embedded itself into operations as a result. 4) We're all lazy and hate change. On Tue, May 26, 2009 at 12:39:10PM -0700, Seth Mattinen wrote:I have a pure curiosity question for the NANOG crowd here. If you run your facility/datacenter/cage/rack on 120 volts, why? I've been running my facility at 208 for years because I can get away with lower amperage circuits. I'm curious about the reasons for using high-amp 120 volt circuits to drive racks of equipment instead of low-amp 208 or 240 volt circuits. ~Seth--- Wayne Bouchard web () typo org Network Dude http://www.typo.org/~web/
Current thread:
- Re: Why choose 120 volts?, (continued)
- Re: Why choose 120 volts? Barney Wolff (May 26)
- Re: Why choose 120 volts? Steve Bertrand (May 26)
- RE: Why choose 120 volts? Dave Larter (May 26)
- Re: Why choose 120 volts? Joe Greco (May 26)
- Re: Why choose 120 volts? Jared Mauch (May 26)
- RE: Why choose 120 volts? Dave Larter (May 26)
- Re: Why choose 120 volts? Alex H. Ryu (May 26)
- Re: Why choose 120 volts? Owen DeLong (May 26)
- Re: Why choose 120 volts? Brian Raaen (May 27)
- Re: Why choose 120 volts? Dorn Hetzel (May 27)
- Re: Why choose 120 volts? Peter Dambier (May 27)
- Re: Why choose 120 volts? Michael Thomas (May 27)
- Re: Why choose 120 volts? Peter Beckman (May 27)
- Re: Why choose 120 volts? Iljitsch van Beijnum (May 27)
- Re: Why choose 120 volts? Seth Mattinen (May 26)
- Re: Why choose 120 volts? Chuck Anderson (May 26)
- Re: Why choose 120 volts? Chris Adams (May 26)
- RE: Why choose 120 volts? Dave Larter (May 26)
- Re: Why choose 120 volts? Joe Greco (May 26)