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Re: [TowerTalk] OT: Generators and UPS's

To: "N2TK, Tony" <>,"'WA3GIN @ Arlington County, VA'" <>
Subject: Re: [TowerTalk] OT: Generators and UPS's
From: Jim Lux <>
Date: Fri, 25 Aug 2006 13:40:32 -0700
List-post: <>
At 01:19 PM 8/25/2006, N2TK, Tony wrote:
>Any thoughts about using something like a Tripp Lite IS1000 isolation
>transformer to help this? Was thinking of getting one and plug in my rig,
>and UPS.

Nope.. a transformer doesn't help the waveform.  A big ol' honkin' 60 Hz 
bandpass or low pass filter maybe?  Or, loads that have better current 
waveforms (i.e. they look more like a resistor, rather than a diode feeding 
a capacitor)

There are solid state PFC and harmonic content devices made that 
essentially turn a very spiky current draw into something smooth and 
sinusoidal.  I've only seen them as modules for the front end of switching 
power supplies (e.g. from Vicor), but I imagine that someone makes them for 
generalized AC in to AC out kinds of applications.  Think of them as an 
active bandpass filter for 60 Hz.

But pretty soon, you run into a cost effectiveness problem.  It might just 
be easier and cheaper to use a bigger generator (so that the series 
impedance is lower, so the current ripple results in a smaller voltage 
ripple) as 'GIN suggests.

OTOH, hams are great scroungers... maybe a LC filter tuned to 60 Hz would 
do the trick.  Surplus PFC or motor run capacitors are available. Scrounge 
a big transformer core  (microwave ovens are a good source, these days) and 
wind your inductor.  100 uF and 70 mH will resonate at 60Hz.  Actually, 
probably a low pass filter with a cutoff of, say, a few kHz might be all 
you need (depends on how picky the UPS is... and, the filter only has to 
carry the UPS current, not the full load current of the generator)


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