[Milsurplus] DC vs AC for power distribution
J. Forster
jfor at quikus.com
Tue May 1 16:23:22 EDT 2012
There are switching regulators that can increase the part of the cycle the
caps charge. An inductor would do the same thing.
I very much doubt you are going to see DC come back into common use.
YMMV,
-John
==============
> One serious problem today is the third harmonic current in the neutral
> of a 3 phase 4 wire distribution system feeding switching power
> supplies. Because current flows only at or near the peak of the wave to
> charge the condensors, the effects on the line are serious if there are
> large numbers of these power supplies. Office buildings and other places
> where there are many 120 volt single phase computers can cause
> dangerous overloading of the neutral. There are various methods used to
> offset the effects or capture the wasted harmonic power, but having one
> master DC supply in the building might be a better way to deal with this
> problem. A six phase or zig zag transformer connection could give very
> good DC and yet keep the phases balanced and the harmonics to a far
> lower level, also would allow a convenient battery backup. I have not
> yet tried powering up a 120 volt AC switching power supply on 170 volts
> DC, but as long as all the power for the device is derived from the
> output of the supply, it should work fine. The two major considerations
> I can see would be cooling fans, relays, or transformer loads in the
> device that operate directly from the incoming line, and the rating of
> switches and fuses between the power source and the rectifier in the
> switching supply.
>
> Bruce Gentry
>
> J. Forster wrote:
>> IMO, the major benefit of DC HV transmission is the issue of
>> synchronizing
>> the grid. With DC, it is not an issue. With AC it is a nightmare.
>>
>> -John
>>
>> =============
>>
>>
>>
>>
>>> The problem being encountered with ultra high voltage transmission
>>> lines
>>> these days is insulation (and air) breakdown at voltage peaks. Since
>>> DC
>>> doesn't have them, it is preferred over AC for maximum capacity lines.
>>>
>>> 73,
>>> George
>>> W5VPQ
>>>
>>> ____________________________________________________________
>>> 53 Year Old Mom Looks 33
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>>>
>>>
>>>
>>
>>
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