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Power conditioners and filters

R

RR

Jan 1, 1970
0
Hi,

Will a cheap filter clean up an AC waveform (remove most if not all noise)
or do I need a real power conditioner?

Any comments on the quality of the APC LE-1200I, which seems to be a real
power conditioner at a reasonable price?

I know I can buy one and look at the waveform to see if it's much improved,
but I thought I'd run it past you experts. (Thanks again for your help on my
other posts.)

The background is as follows.....

I've bought a diesel Generator Set for backup power, and today we actually
had a 2 hour power failure. It was a great asset to have!

I mainly use it for supplying our online (double conversion) UPS which power
our computers.

One UPS (the smaller one, of course!) handles the GenSet output fine.

The main (larger) UPS goes into fault condition when I plug it into the
GenSet.

I've worked with the UPS manufacturer and still have no resolution for this
problem. I do have a workaround, which worked fine today, but it's an
annoyance (I have to remove all load from the UPS - switch off the
computers - then apply the input power then apply the load once the UPS has
switched the inverter on).

I know what *is not* causing the problem. It's not the voltage, it's not
the frequency, and it's not the floating earth.

I now believe it is the noisy waveform that the GenSet supplies. It provides
a reasonably steady 54Hz and 240V, but the waveform is quite noisy. In
particular, at peak voltage there is a 10-20% short-lived voltage drop.
Thru the rest of the waveform there are notches or jitters.

The theory is that the UPS tries to match the frequency between the inverter
and the the mains (GenSet). The noise looks like very erratic frequency and
this confuses the UPS and it goes into fault.

All I want is a cheap filter or conditioner that I can place between the
GenSet and the UPS and have it remove enough of the noise so that the UPS
doesn't go into fault condition.

The UPS manufacturer has been very helpful, but the conditioners they supply
cost 6 times the APC one mentioned above.

tia,
RR
 
RR said:
Hi,

Will a cheap filter clean up an AC waveform (remove most if not all noise)
or do I need a real power conditioner?

Depends what kind of noise it is. RF will be removed with a simple
filter.
I've bought a diesel Generator Set for backup power, and today we actually
had a 2 hour power failure. It was a great asset to have!

I mainly use it for supplying our online (double conversion) UPS which power
our computers.

The main (larger) UPS goes into fault condition when I plug it into the
GenSet.

I've worked with the UPS manufacturer and still have no resolution for this
problem. I do have a workaround, which worked fine today, but it's an
annoyance (I have to remove all load from the UPS - switch off the
computers - then apply the input power then apply the load once the UPS has
switched the inverter on).

I know what *is not* causing the problem. It's not the voltage, it's not
the frequency, and it's not the floating earth.

Why is your earth floating?
I now believe it is the noisy waveform that the GenSet supplies. It provides
a reasonably steady 54Hz and 240V, but the waveform is quite noisy. In
particular, at peak voltage there is a > 10-20% short-lived voltage drop.
..

These are caused by the capacitors in smps charging, you cant do much
about them without spending lots of money.
 
R

RR

Jan 1, 1970
0
Depends what kind of noise it is. RF will be removed with a simple
filter.

From what I've read, any change to a sine wave (e.g. a square wave) can be
thought of as many harmonics being added to it, esp high freq harmonics.
But I guess this doesn't count as RF, does it?
Why is your earth floating?

The GenSet provides a floating earth and the UPS *was* set for M.E.N. We
converted the UPS to floating in case that was the problem. It wasn't.

AFAIK, floating earth simply means the Neutral is not tied to the earth
line. So, there's a potential between A-E and N-E which added together
provides the mains potential between A-N.

The earth wire is connected through the GenSet to a steel stake in the
ground.
drop.
.

These are caused by the capacitors in smps charging, you cant do much
about them without spending lots of money.

Do you mean that the *cheaper* power conditioners (such as the APC I
mentioned) can't fix this in the waveform, or do you mean that no power
conditioner can fix it?

tia,
RR
 
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