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Registered Member #1822
Joined: Fri Nov 21 2008, 08:04PM
Location:
Posts: 300
There does seem to be a prevalence of new products that only accept a DC input. I have a bunch of gadgets that only get power from a USB port and electric cars would be easier to charge with DC
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
cduma wrote ...
There does seem to be a prevalence of new products that only accept a DC input. I have a bunch of gadgets that only get power from a USB port and electric cars would be easier to charge with DC
This thread is drifting away from transmission voltages (800 kV), but...
There is a movement to standardize on 380 VDC power distribution in data centers and other buildings with many computer loads. Because the traditional system is wasteful: - bring in power at 2xx volts AC - rectify for battery bus in central UPS - invert back to 2xx VAC and distribute to wall plugs - each device starts with a SMPS which rectifies the AC input to 3xx VDC on the filter caps. The subsequent switching stage is modulated for AC power factor correction.
The new way: - Central resource includes PFC and UPS functions. - 380 VDC is distributed to subpanels and IEC standard wall sockets with a soon-to-be-popular pin configuration. - Data center equipment is purchased with a 380VDC (or universal) power supply option.
One technical challenge is breaking the DC arc when something is unplugged "hot". A proposed solution is for smart connectors that include a switch, signaling the SMPS to shut down gracefully before the main contacts open.
Induction motors are no problem if they are, or should be, driven by VFD's. I haven't yet heard of any lighting fixtures (or CFL lamps) designed for 380 VDC.
Registered Member #1083
Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256
Well, consumer products have been using a DC input since the invention of batteries... But we're talking about high voltage power transmission here. IIRC the pacific DC intertie is an important component of the power grid. It maintains a power balance between the northern and southern power lines. In the summer, excess power from the north is relayed south for air conditioning, and in the winter, excess power from the south is relayed north for heating etc. In theory, DC is most efficient for long range power transmission but that's it. Maybe in the future, when technology allows cheaper DC converters, DC power lines will be more widely used. Manipulation of AC voltages is far easier Or maybe i have no idea what i'm talking about
I hadn't heard of standardizing a 380VDC system, that sounds very interesting
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800kV DC for power transmission? what?!?
