Alternatively, you could use the soundcard and audio recording software
(I use CoolEdit Pro on a laptop) with a low voltage ac output wallwart
(3 to 6vac) to safely sample the mains voltage waveform with a simple
resistor attenuator network to drop the 3 to 6v down to around 100mV or
so, suitable for feeding the line input.
Many years ago (around about twenty years back, istr) I used to use an
ancient all valved (tubed) dual beam 'scope to test mains and inverter
wavefroms simply by powering it from the supply under test and,
conveniently, making use of the "50 Hz calibration source" (derived from
a low voltage secondary on the 'scope's mains transformer).
When I first observed the mains waveform, I noticed it looked flat
topped and quite visibly a departure from a pure sinewave which I put
down to the effects of the scope's loading on the mains transformer
until I powered it up from an ancient UPSonic 600 which then showed a
much purer sinewave (admittedly with a low level of sample ripple at
around a frequency of 5KHz very similar to what you see with a Smart
Almost two years back I bought a cheap PowerCraft 2800LR generator and
ran into problems trying to persuade a SmartUPS 2000 to play nicely with
it. There's a problem with accessing the lowest sensitivity option only
available via the software interface with this particular sample of
SmartUPS so I couldn't make it tolerate what proved to be outrageous
voltage swings from the capacitive loading the UPS was switching into
the circuit whenver it tried to switch back to line power.
The smaller SmartUPS 700 could be configured to accept the poor quality
power from the generator (which, btw, is far better than that displayed
for the Alton generator which looks like it has a slipring/brush issue)
but I really need it to work with the 2KVA SmartUPS.
This time, I decided against dragging that ancient scope off the shelf
(it's a heavy brute!) to investigate what was actually happening and
decided I could get just as good results using the laptop as a low
bandwidth storage scope (5Hz to 22KHz is ample bandwidth for this
investigative work ;-).
Any PC with a soundcard and audio recording software can be used. The
only extra bit of kit is a suitable low voltage AC output wallwart to
let you safely sample the mains voltage and feed it to the line input at
around the 100mV mark.
A simple single cylinder 4 stroke prime mover will produce increasing
levels of 2nd harmonic with loading due to the modulation of the
rotational speed by the accelerations/decelarations as the engine
repeats its induction, compression, power and exhaust stroke cycle every
two revolutions. Don't worry though, as I discovered, this is amongst
the least of your problems regarding powering "sensitive electronic"
kit. The _real_ issue is voltage stability whenever the load has the
merest suggestion of a leading power factor (capacitive loading).
Sad to say, even a modest 4.7 microfarad capacitor sent the 230v output
shooting up to 270 or so volts. It seems that all such alternators
behave this way given sufficient capactive loading (Yes, even those MW
rated machines in power stations). It's the 'self excitation' effect
normally used to good effect to turn an ac induction motor into a
sinewave generator which is over-riding the AVR control.
My next generator purchase will _only_ be of the inverter design, such
as in that Honda EU2000i model since that is the only type that is
immune to the capacitive loading issue inherent in conventional
In the meantime, I'm hoping to get around the SmartUPS2000 problem by
using generator power to feed its 48 volt battery pack with a 1350 or
1800 watt 53 volt DC PSU to allow the UPS to stay 'on battery' (I'll
have to improve upon the rather restricted airflow that prevents the
cooling fan in the UPS from properly doing its job before I contemplate
running it for a protracted outage).
I've run endurance tests on the SmartUPS in the past with external
batteries that gave me in excess of four hours runtime at about one
quarter load. This UPS isn't strictly rated for indefinite runtimes on
oversized batteries but I think this is only because the style over
function case design severely compromised the fan cooling performance.
The runtime chart shows 7.5 hours on a 35W(50VA) loading with its
normal complement of 4 x 12v 18AH batteries which suggests that an
improvement in the cooling will be all that is required to uprate it to
indefinite autonomy at full load given a large enough battery (or that
1.8KW DC supply to keep the battery pack float charged from the
I know a local flea market trader who buys computer and electronics kit
at various auctions disposing of bankrupt stock or returns items who
sells this stuff for a fraction of their new cost. Amongst his inventory
are various universal laptop chargers which typically range from 90 watt
to 150 watt ratings. I've figured that I could string the outputs of
three such 150 watt units in series set to 18v to create an 8.44 amp 54
volt supply (a total power output of 456 watts) which, with a blocking
diode in series, should provide a 53 volt float charge supply.
Given enough of these laptop chargers (and I'm hoping to get at least
ten to 14 of these at about 40 to 50 quid the lot - less than a hundred
dollars) I can just simply add extra strings, each with their own
blocking diode, in parallel to build up to a 1350 or even 1800 watt PSU
in units of 450 watts at a time.
If I can get my hands on these in the quantity promised by my friendly
flea market trader, I'll not be powering them directly from the
generator (remember those wild voltage swings?) but via a stepdown auto
transformer (they're laptop chargers - 90 to 265 Vac input range) so
that even an overvolt to 300Vrms on the generator will be kept below
their 265 volt max input limit. I'm no fool! ;-)
Of course, there's no guarantee that this will all work as envisaged
but I doubt the generator will produce the issues seen with 'Quasi
Sinewave' (aka MSW) inverters so it looks the most effective way to
maintain uninterruptable power using a cheap generator to extend the
autonomy (provided I can get those laptop chargers at the right price).
The DC supply I'm going to make up could be envisioned as being a
Redundent Array of Inexpensive Powersupplies (IOW, a RAIP ;-)
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On Fri, 26 Feb 2010 05:48:33 GMT, Johnny B Good
I do have an old laptop I could experiment with to look at the waveform.
I'll have to dig it out and give that method a try.
With regard to generator power, I hope your RAPE^H^HIP system works well
for you. We've got decent generators (1800 rpm/water-cooled/4cyl) -- 15kW
at one home, 12kW at the other, and don't have the problems you describe.
As a matter of fact, last night about four hours after I hooked up the new
SmartUPS1000 (SUA1000) to my wife's XPS9000, we had a three-four hour power
outage, courtesy of mother nature. The UPS worked properly and powered her
Dell computer during the 20-30 sec it took for the generator to start up,
stabilize, and begin supplying our backup power. And both that and the
BackUPS 1500 RS I have on my computer had no problem with generator power.
Oh, and both UPS's are set to "high" sensitivity.
You wrote about only being able to adjust your SmartUPS sensitivity from
the software. That's true on my APC UPS's also, but the software is
included with the units; and I'm pretty certain is freely downloadable from
the APC web site.
Good luck with your tinkering.
Well, there's a world of difference between a cheap PowerCraft 2800LR 2.5KVA
single cylinder gasoline fuelled generator and those 12 and 15 KVA 4
cylinder units of yours. ;-)
The low sensitivity option exists purely to permit cheap generator
power to be used. Quite obviously, your gensets are of a high quality
The software itself isn't the issue, it's a weird problem in the
SmartUPS 2000 that prevents the APC software from doing anything more
than allow the installer to detect I've got it connected. Once
installed, it cannot make sense of the responses it gets back from that
The same software has no problems whatsoever with the smaller SmartUPS
700 which can be set to low senstivity without using the software anyway
(it has a button on the back which allows you to toggle between hi, mid
and lo sensitivity. The SmartUPS 2000 can only be switched between hi
and mid sensitivity on the rear panel dipswitch with the low sensitivity
option only being available via the 'funny' serial port and the
I can access most of the monitoring functions using an open source APC
monitoring program but the problem seems to be that any attempts to make
any changes of settings fail to be stored. It's as if the nvram area has
been write protected. I suspect it may have been misprogrammed in the
past (I'd bought it secondhand at a radioham rally some years ago sans
its battery box, hence the external battery pack of four 25AH SLAs and
eight, in two banks, used 7AH SLAs of indifferent capacity being 'parked
to maintain condition' to provide additional, if uncertain, capacity).
Other than this strange software issue, the UPS works exactly as
intended. The only reason I even bothered wiring up a 'funny' rs232
adapter cable to run the software was because I needed to desensitise it
even further than the dipswitch option allowed. If I could get my hands
on a controller chip from a scrapped Smartups 1200, 1700 or 2000, I
think I can restore it back to full functionality again.
Thanks, I think I'm going to need every bit of luck I can grab onto to
sort this one out. ;-)
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