>Tim wrote:
>> And by this point in time ferroresonant transformers were also being
>> dropped in by folks who weren't happy with the original supply, either.
>> Having used a large variety of S-100 boxes, far and away my favorite
>> power supplies are ones with ferroresonant transformers.
>I've been told that one shouldn't plug anything using a ferroresonant
>transformer into a UPS. Perhaps someone who knows more about the
>characteristics of ferroresonant transformers (and UPSes) can explain why,
>or refute the claim.
Ferroresonant transformers really really want sine waves as input.
Many UPS's put out square waves, or slightly shaped square waves.
There are many high-frequency harmonics in a square wave, and these
disrupt the careful LC-resonance-at-saturation regulation mechanism.
Not only do ferroresonant transformers want sine waves, they want
sine waves of a specific frequency. I've never tried running a 60Hz
unit at 50Hz, but I do know from hard experience what happens at
400 Hz :-(.
There are UPS's that do put out nice sine waves, but these aren't all
that commonly found.
>(*) The only modern thing, anyhow. Did DEC use ferroresonant transformers in
>any of their machines?
DEC computers from 1970 onwards typically used switching supplies for
all high-current supplies, though there are usually some low-current
supplies with linear regulators. (There are some exceptions, such as
the "large" 8/E using a linear supply while the "small" 8/F used a
switching supply)...
DEC did sell ferroresonant line conditioners (some of them quite large;
one that I passed by took 440VAC 3-phase in and had about 70 15 amp
circuits out), but these came before the computer.
--
Tim Shoppa Email: shoppa_at_trailing-edge.com
Trailing Edge Technology Voice: 301-767-5917
7328 Bradley Blvd Fax: 301-767-5927
Bethesda, MD, USA 20817
Received on Sat Sep 19 1998 - 14:51:08 BST