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[aprssig] Field Day power (220 VDC)

Scott Miller scott at opentrac.org
Mon Oct 22 00:45:34 UTC 2007


That was for open-air use, and not in chassis wiring.  I think it's just 
a guideline and not an official specification, but still... 18 AWG seems 
thin.  That's what, 16 watts dissipated as heat for every 100 feet at 5 
amps?  I suppose it's not going to melt the insulation, but 14 AWG would 
have 1/3 the loss.

Scott
N1VG

Bob Bruninga wrote:
>>> Anyway, using lightweight #18 extension cords can
>>> deliver killowatts of power over hundreds of feet 
>>> using this method.  Delivering a kW is only 
>>> drawing 5 amps at 220 VDC [using switching power 
>>> supplies at the end down to 12v at 20+ amps each...]
>> Just thought I'd point out that the... power 
>> transmission capacity of 18 AWG cable is about 
>> 2.3 amps using the 700 circular mil per amp rule.
> 
> That generally applies to windings inside a transformer where heat is a driving factor.  In open air, #18 is rated at 16 amps and in cables and bundles it is rated at 10 amps.  So I figured 5 amps (1 kW) to be very conservative per line cord.
> 
> Modern switching power supplies give us lots of power options, and as more and more applications turn to switching supplies, we can take some advantages of their wide range of input voltage specifications.  etc..
> 
> And soon most cars will have a variety of voltages that we may want to inteface.  Anyway, seeing this 50 kW generator sitting in the driveway begs to be used somehow...
> 
> Bob, WB4APR
> 
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