On an additional note, as Jim alluded to earlier:
> Also, switching power supplies seem to be more tolerant of noisy power.
The switching PS in most computer and modern consumer electronics
converts AC to DC to high voltage AC and then back to DC and is actually
like a little on-line UPS without the battery. This, of course, means it
is interruptible but it does do a lot of the power conditioning too
(though not as thoroughly as a proper UPS).
Ever wondered how the manufacturers of "surge suppression" power bars
can offer massive warranties on the computer equipment they "protect"?
That's because the failure rate on devices with switching PS caused by
power fluctuations is very low to start with. The only real function of
"surge suppressing" power bars is to increase the margin for the
manufacturer (and give you a few more outlets). They do little to
protect the equipment downstream as they cannot suppress "common mode
noise", the most harmful type.
regards,
Drew
David Cook wrote:
Thanks Drew.
I wasn't mixing my concepts, I was falsely believing APC SmartUPS series and
above were all Online rather than "Line-Interactive" (APC's terminology)
therefore conditioning circuitry was not necessary. So much for me thinking
the server at home had an online supply!
So ...
Online UPS = conditioning not needed due to design
Line Interactive = must have good conditioning circuits/do your
homework/looks like most APC models fit here.
-dbc.
-----Original Message-----
From: Drew Gibson [mailto:[email protected]]
Sent: April-07-09 5:15 PM
To: David Cook
Cc: [email protected]
Subject: Re: [biz] UPS: power conditioned
I think you might be mixing two different UPS concepts here.
This can be a contentious subject but if I may be allowed to simplify....
The best UPSs (eg larger and more expensive, say >8KVA) are online,
full-time. They constantly convert the AC in to DC, feed it to the
batteries and then draw the load as DC and convert it back to AC to
supply the load device.
Most of the of UPSs the small to mid-size, affordable UPSs are only
fully online when the mains power fails and power from the batteries is
required. There is a short (very short) interval during a power failure
as the UPS switches the supply from the AC input to battery. Otherwise
the AC is fed straight through to the load device.
In the first case, power conditioning is done by default as the power is
always being processed and "conditioned". This is the best type in terms
of protecting your computers, but hard on the budget.
In the second case, power conditioning has to be added. Most reasonable
devices will, in fact, condition the power to some extent. They will
moderate high input voltages, boost sags in the voltage (by drawing from
battery) and suppress spikes and surges. This type is a little less
capable in terms of protecting equipment but the lower price makes up
for that and more.
APC do make both types as do Tripp-Lite and others.
Since phone systems are expected to operate during power outages for
much longer than regular servers, I would recommend the second type due
to cost. I would oversize the UPS (they are usually sized by power
rather than runtime) to get a longer runtime. Both APC and Tripp-Lite
make units that can have external batteries added for additional
runtime. The last one I spec'd would run the Asterisk server and the
VoIP switches for 3-4 hours. (APC 2200XL rackmount, if I remember rightly)
regards,
Drew
David Cook wrote:
I believe all APC upses qualify in that regard. Conditioning should refer
to
methods of ensuring that transients and other oddities from the power line
never reach the equipment plugged into them.
My understanding is that all APC upses (and most other "good" upses) are
of
the variety that the line power only serves to charge the batteries -
nothing more. The batteries subsequently feed constant power into the
inverters which create the 110VAC (hopefully a sine wave) to power the
equipment. Therefore at no time are the products plugged into the UPS ever
connected to the line current and therefore not subject to stuff outside
affecting your equipment.
The analogy used to explain it to me was filling a bucket (batteries) with
water with a fixed size hole in the bottom (VA rating of the UPS). As long
as some volume of water is retained in the bucket, you can fill the bucket
evenly or sporadically but the flow rate out the hole remains the same.
If my understanding of this is full of crap, please let me know :-)
-dbc
-----Original Message-----
From: Frank Bax [mailto:[email protected]]
Sent: April-07-09 3:00 PM
To: [email protected]
Subject: [biz] UPS: power conditioned
In the Asterisk book from O'Reilly; it says "Make sure your UPS is power
conditioned. If it doesn't say exactly that, it isn't."
http://astbook.asteriskdocs.org/en/2nd_Edition/asterisk-book-html-chunk/aste
risk-CHP-2-SECT-2.html#asterisk-CHP-2-SECT-2.1
I don't see this wording on any UPS devices from APC; do they sell one?
If not, who does?
Frank
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
