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

To: "'towertalk reflector'" <>
Subject: Re: [TowerTalk] OT: Generators and UPS's
From: "John Wagner" <>
Date: Fri, 25 Aug 2006 16:59:14 -0400
List-post: <>
 A Ferroresonant type of line isolator will in-fact take a rather poor sine
wave and make it proper.

Topaz, Sola, Delta Emerson used to make them. They are not very efficient
and don't like loads as they become more inductive and less resistive. SO
they are not for every application. If they are loaded above 60%, they will
keep up the sine wave for better than two cycles before they
decay..sometimes, that's all you need for a 16ms UPS transfer switch to

We have really large diesel powered gen sets here and lots of individual
UPS's around without the problems noted when on gen power.

Keep the list informed if you get any answers from the UPS folks..

John W8JJW

> -----Original Message-----
> From: 
> [] On Behalf Of Jim Lux
> Sent: Friday, August 25, 2006 4:41 PM
> To: N2TK, Tony; 'WA3GIN @ Arlington County, VA'
> Cc: 'towertalk reflector'; 'Doug Rehman'
> Subject: Re: [TowerTalk] OT: Generators and UPS's
> 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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