Did the transient suppressors, too.
A few years ago in a severe winter storm, after we got the neighbor's
house on generator, his furnace still wouldn't work -- furnace brain
fried. Took the repair guy 4 hours to make 20 minute trip . . . . my
surge suppressors went in a week later.
One thing I left out of my earlier post: ANYTHING I care about is on a UPS.
Good luck!
Jim
On 10/11/2015 12:24 PM, Bob Camp wrote:
Hi
If your problem is transients, from lousy power companies or from lighting on
your power line, there are ways to address that.
High voltage at the service line into the building should be fixed at the point
the line comes in. If you don’t, then you get into
all sorts of neat “transient went here, then there, then nuked the gizmo”. For
things like time or frequency distribution this
is a very real thing. The power to one set of gear may / may not be on the same
UPS as the power to another set of gear.
The best answer is a whole house protection device. These can range from < $100 at
your big box store to > $1K. They can be
a wire it in on a spare breaker or a call out a pro sort of thing. A lot
depends on just how bad your problem is. The net effect is that
your line is fully clamped to local ground at the panel. The phases are both
clamped to a level that should not affect properly
designed gear that’s in good condition. There is always a tradeoff between how
tight to clamp and how fast the gizmo wears out.
There is the usual “get what you pay for” in terms of knowing the current
degree of wear out of the device.
The alternative is to get your entire lab (and all the devices that feed it)
onto a good isolation transformer. . Everything then ties to
a single “lab ground”. What ever bounce you get is now all on everything at
once. Each time I’ve done this, keeping all the standard
lines, antenna feeds, ethernet cables, GPIB cables, cable TV feeds, and the
rest of it correct has become impossible after a year or two.
There’s just to much going all over the place.
We are already more than just a bit off topic for this list. There is another
twist this can take, that heads over to talking to
your power company and the people who regulate it. I have seen that work (as in
the nice new line that feeds this side of town).
Bob
On Oct 11, 2015, at 10:44 AM, Jim Sanford <[email protected]> wrote:
Where I live, there are two problems. Frequent long outages. Solved with a
natural gas standby generator, which has run several times in anger for
extended periods since installed. (Vulnerable supply, low priority for
restoration.)
The bigger problem is transients. On a good night, my computer UPS activates
at least once an hour. SOmetimes you can see the lights blink, some times not.
In the last 6 months, I have had problems with a UPS (recovered by extended
shutdown), an Astron Power supply for amateur radio equipment, a spectrum
analyzer, two signal generators, a network analyzer, and an oscilloscope. All
were power supply failures, not all repairable. My lab is now protected from
the power company by a SmartUPS 2200NET.
I expect the grid to get /less/ reliable.
-- In 2007, DOE published a grid study which said there did not exist
sufficient generation capacity over load to maintain grid stability.
Insufficient additional generation was booked for construction, so they
predicted widespread rotating blackouts by 2010.
-- The 2008 recession greatly suppressed aggregate load, which is probably
why the rotating blackouts did not happen. I read recently that demand has not
yet recovered above the suppressed levels following the precipitous drop in
2008. (Which generates interesting other questions . . . .)
-- I have lost track of the number of GigaWatts of generation which has
been shut down.
If the load ever recovers . . ..
Good luck!
Jim
[email protected]
On 10/11/2015 9:05 AM, Bob Camp wrote:
Hi
Unless you live in an unusual location, long term power outages are going to be
pretty
rare. At the house I’m now in, we had a high voltage feed that was on it’s last
legs. We
had short outages on a “many times a week” basis if the wind was blowing at
all. We had
rare outages in the > 5 minute range. The short / frequent blip stuff is what
most light weight UPS’s
are designed to handle. Not everybody has this problem. I no longer have it,
they
ripped out 10 miles of old feeder and the new one works fine.
Indeed there are locations that experience multi hour outages on a fairly
regular basis.
The combination of bars closing late on Saturday and a long straight road with
an abrupt
turn in it was particularly hard on a feed line I once had to cope with. In
that case gas turbine
generators were the answer.
If you have a case where long outages are common, rotary machines are often the
better
answer than batteries. In the case above, the power company was the one footing
the bill
for the gear. Fair in this case since they were the ones that *could* have
moved the line.
If a > 10 minute outage is a “less than once a year” sort of thing, and OCXO’s
are your only concern,
let them shut down. The net impact to your lab will be relatively small. The
cost to fix the problem will
be relatively large. Short blips often, are well worth fixing.
The hidden issue with running a UPS is the relatively short life of the
batteries.
Sealed lead acid is low cost up front, but they simply do not last when charged
the way
a typical UPS charges them. Before you go into “can’t be true” mode … plug a
100W light
bulb load into your UPS and see how long it runs. Battery still *shows* as
good on the indicator.
Gizmo only runs for 1/4 the time it should … hmmmm …. It’s very common to go
into these
projects with a reasonable budget, and then find out that the budget to keep
it going is
not quite so generous.
Bob
On Oct 11, 2015, at 4:57 AM, Kasper Pedersen <[email protected]> wrote:
On 10/11/2015 12:07 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
Essentially the charging circuits are not designed to run as long as needed
to charge big batteries. Even on ones designed for external batteries,
there's a recommended limit on the size of them. So if you think you might
want to increase runtime by adding some batteries, buy one designed for
that service.
I have gone down that route, so I have some real data to share:
My (soon to be replaced) backup is an old back-ups CS 500, with a
rewired battery pack out of an RT3000 UPS. So instead of 7Ah, the UPS
has 40Ah. With plenty of fuses.
When charging the standard 7Ah battery, the UPS delivers about 0.7A
(from memory) for many hours, and sits at about 14C above ambient.
When charging the 40Ah, the current is the same, the temperature is the
same, just for longer, as it should be, since the thermal time constant
is much shorter than the time it takes to charge the 7Ah.
Where this has problems is during discharge:
I have about 55W load on it, which in turn is at least 5A on the
battery. After 2 hours a timer in the UPS shuts it off, regardless of
battery voltage.
Also, if you run the UPS at high load where the standard battery lasts
shorter than the thermal time constant, then there might well be trouble.
The replacement, a back-ups pro 1500 behaves differently.
It has support for external battery packs, and will happily run for at
least 5 hours, even when the external-pack-present signal is not connected.
The external-pack-present signal does make a difference when charging;
Without it, it charges at 0.7A. with it, it charges at 1.5A, and the fan
is on continuously.
/Kasper Pedersen
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