[BC] Cyberpower brand UPS

[Broadcast List USER]

I have seen this more times than I can count.  It isn't the UPS, it is  
the generator.

I dug way into this several decades ago, but sadly, my memory isn't  
that good for things I never use, but here goes.

There are more than a few ways of generating the field current.  Most  
standby motor/alternator sets use methods that produce a whole lot of  
harmonic distortion.  The UPS sees this, and thinks it isn't OK for  
the load, so it never switches to the generator.

Several decades ago I bought a AT&T System 25.  Sure, it was my third  
choice, but I was forced to by a corporate edict that I later learned  
was less than honest.  Anyway, since the System 25 will drop all calls  
immediately upon power loss, and takes a while to reboot, I bought the  
AT&T UPS with it.

Being a belt and suspenders kind of guy, I also put in the maximum  
number of power failure fall back phones (sets) with their hard to  
understand ground start button.  OK, it isn't hard for you and me to  
understand, but the staff at a radio station?

I was out on an errand, and got a page that the phone system was out.   
I called in, and of course, no one knew how to answer the five phones  
that were ringing, or why they were.  After all, they were single line  
sets in places like the lobby, the copier, the computer room, and so on.

I finally got through to the jock, who went and got someone for me.   
It turned out we had been on generator for about 20 minutes, then the  
phone system died.  Being on generator wasn't odd for us, so no one  
was concerned about that.  However, the AT&T UPS didn't see the  
generator as no problem, and stayed on battery until it was flat.

Now, you have to understand that since I was FORCED to buy the System  
25, my GM and I made it clear to the AT&T sales person that we didn't  
want it but we were being forced.  In fact, as the sales person was  
writing it up, she asked why we were buying it, seeing that we thought  
other systems were better.  We told her.  She got a very experienced,  
and very good engineering person to head up the installation, as they  
have seen this problem before, and they knew that if anything went  
wrong we would be yelling "WE TOLD YOU SO!"  As I recall, they threw  
in the UPS to make sure we wouldn't be upset.

Well, we had a Kohler generator that took up the entire plant.  The  
transmitter building, including HVAC, and the entire studio building,  
also including HVAC.  I was always happy with the gen-set as it ALWAYS  
worked, and since we had fuel, water and oil heaters, it started  
immediately and took the load in just over one second.  The  
transmitters never had a chance to complain, and wouldn't even go  
through the step start procedure.  We just stayed on the air.

AT&T threw all kinds of people into the problem.  They had people  
checking out the UPS, changed it out a few times, and started checking  
out our power, and our back-up systems.

In the end, they found the problem.  The Kohler gen-set put out nearly  
exactly 208 Volts, at exactly 60 Hz.  On its face, no one could find a  
problem with that.  Still, the UPS would REFUSE to switch to it.  So,  
here I am with a bunch of AT&T engineers, running the generator, and  
wondering what was wrong.

Someone wondered about the distortion.  I thought this was stupid, so  
I offered up my Tectronix AA-51 (if I recall the number correctly).  I  
figured I could directly plug it into a 120 VAC outlet, which was  
correct.  I couldn't believe it.  The THD was HUGE.  I don't remember  
the number off hand (it has been decades) but it was well over 10%  
(but under 30%).

It turns out this is very common, and I can see why UPSs wouldn't like  
it.

They wrote new software for the UPS, and the engineers really  
complained about it.  Still, it wasn't the frequency, and it wasn't  
the Voltage, it was the THD.

Check it out for yourself.  The power company provides power at  
generally under 1% THD, and always under 3%.  It isn't that the power  
company is generating this distortion, but power supplies hung on the  
line are doing it.

However, generators produce up to about 20% THD.  Depending on the  
bandwidth of your analyzer, SQUARE WAVES only produce just over 30% THD!

I have seen this over and over again since then.  The only gen-sets I  
have seen without this problem are the Honda Inerter series.  They  
work great at my house, and UPSs have no issues.  I am SURE there are  
others, but I don't know what they are.

In other words, not blame the UPS.

Buy a really cheep UPS, or one that is always on, a series UPS.  Both  
will have fewer problems.

--chip

On Jun 25, 2009, at 1:00 PM, broadcast-request at radiolists.net wrote:

> Message: 1
> From: tpt at literock93r.com
>
> Watch out for this brand of small UPS (they are sold at Office Depot).
>
> Needed something with 4 instead of 2 outlets just to float the
> satellite receivers and air monitors for a few seconds until our geni
> comes up when the power drops.  The XDS takes about 2 1/2 minutes  to
> reboot, the Wegener, 8 minutes +; rather silly to have a generator but
> be off the air because I am waiting for a satellite receiver to
> reboot.  So I picked up a CyberPower brand 450 VA unit to sit in the
> equipment rack.
>
> Yesterday --at 5:40 AM, a black snake crawled into the substation,
> killing power to the entire town. Or so the cover story goes. 3 phase
> power to us down until 11 AM.
>
> Generator came up (Onan 20 KW) and I switched over to our single-phase
> back-up (a Harris 2.5 K). About a half hour passes--and both satellite
> receivers dump.  Apparently the CyberPower does not like the AC out of
> the Onan genset, it refused to switch back from battery and just ran
> down. No problem with the half dozen APC units I have on the
> computers, exciter, Omnia processors, etc.
>
> Only two things comes to mind: A. The Onan's AC is not close enough to
> a sine wave to keep the Cyber Power happy (picky, picky!) or B. (more
> likely) voltage tolerances are way too tight.  Our usual line voltage
> floats around 217 to 220; the genset was made for 240.
>
> I bought another APC UPS, the CyberPower unit is going home to back up
> my home computer. Much less "mission-critical" use.