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From: rgarito@thunder.cis.ufl.edu (Robert David Garito)
Newsgroups: comp.os.linux.development,comp.os.linux.misc,comp.os.386bsd.questions,comp.os.386bsd.misc,sci.electronics
Subject: Re: APC SmartUPS series serial-port protocol anyone?
Date: 7 Nov 94 18:59:29 GMT
Organization: University of Florida (Computer Science Department)
Lines: 37
Message-ID: <rgarito.784234769@thunder>
References: <CMETZ.94Oct30192816@itchy.inner.net> <1994Nov3.012516.8955@csustan.csustan.edu> <rgarito.783901485@thunder> <1994Nov7.062826.5747@csustan.csustan.edu>
NNTP-Posting-Host: thunder.cis.ufl.edu
Two points on that flamy reply regarding how Best UPS's are crap.
1) The unit that he is referring to must have been quite an old
unit. All of the newer units (newer than a couple of years
ago) that are >= 3.1kVA have battery breakers. These CAN
break the circuit under load. (UL requires this)
2) The relays that he referrs to I am assuming are located on the
Charger PCB. I could be wrong on this one. But still, it is
much easier to replace the whole PCB than isolate the problem
to a relay. Also, the idea of semiconductor relays is for
reliability and noise resistance. No contacts to arc or burn.
I also do concert lighting professionally (BIG shows, not your
local groups) and we use solid-state relays EVERYWHERE where there
is high-current draw. In fact, we usually use PWM dimmer circuits
and the power device is usually a solid-state relay switching
up to 75 amps or so... Sure, a few have failed. But, everything
will eventually burn out.
3) The bypass switch that he is referring to is probably a break-before-
make switch. This is not designed to be used under load for
obvious reasons. Just to isolate the UPS when it is already down.
Best also sells MBB switches (for about $150 more) that can
be used to switch under load. If the size of the switch was
incorrect, that was because the person who specified the system
made a mistake. All Best UPSs are supposed to be used with a
bypass switch that is over-rated for it's load. (For safety and
reliability reasons). Now, if Best specified the smaller switch,
I guess he caught them...
--
Robert Garito, President
MicroLAN Technologies, Inc
rgarito@cis.ufl.edu