automatic transfer does not take place at
one quarter of a cycle in a 60 cycle per second AC
power supply, then the sensitive logic controllers of
any network equipment, PLCs, etc will detect the
automatic transfer as a possible zero voltage
condition.
So What? Does that matter, as it is a one time event when the initial
transfer occurs?
So the 750VA UPS, temporarilly switches to the UPS battery standby power,
keeping Radios up, until the Generator power stablizes as on, then UPS
switches back to line power from the generator. IF the generator delivers
unclean unstable power so what, that is the purpose of the small APC UPS to
keep clean power going to the radio devices. So what if the UPS regularly
switches back and forth from battery to Line voltage, as long as the switch
is quick within required tolerances, and that it is not to frequent to drain
the UPS battery.
From my experience, when the UPS did not do its job, it was because the UPS
had a bad battery that could not handle the load, or a low grade UPS that
did not have a fast enough transfer time itself, not a flaw in the
generator's or its autoswitch.
What I had understood that George had said was not the the UPS switched back
and forth between line and battery, but he said the UPS itself kept
switching OFF and ON, as if the UPS was then malfunctioning.
What I was wondering was what type of power output was the problematic
generator putting out? Pure Sinewave or Pulse Modulated. Many low cost
devices put out PulseModulated, which is easier to regulate, to put out
regulated power. However, the Squared edge nature of the wave can be
interpreted by a UPS further downstream as Bad Power, and possibly even
damage the downstream UPS. Which is a reason one is never supposed to
install a ppure sinewave UPS downstream of a Pulsemodulated UPS.
We had designed some battery backup systems usign Tripplite's Power
Inverters (pulse modulated output), which worked great, but we could not use
APC Online UPS (puresinewave) UPSes in the racks. To add better surve
protection we put the protection directly in the Panel box with AC surge
protection. To check status of power outage, we install a cheap Linksys
router, plugged directly into the AC outlet prior to the backup power
systems, and then when this device stops responding, we know that there is
not power beign sent to it. (yes there is an issue where the Linksys could
lock up, and then us not know if it is the Linksys locked up or no power).
One thing we were considering was to plug it inline with the Generators AC
output feed, so teh Linksys bydefault is always off, and then when generator
power kicks in the Linksys powers up, and if we can get to it, we know we
are runnign on backup power.
So the point I'm making is, many generators, just put out raw voltage
without regulation, purposely, so a UPS can be used after it to protect
against drops and surges, and so Rack based UPSes do not need to be removed.
The acception to this is if it has high end voltage regulation that puts out
Pure Sinewave power.
Its actually relevent that we are specifically talkign about the APC 750VA
rackmount UPS. I'm assuming you are talking about the Pure sine wave Online
version.
That model is a sweat spot model because it is inexpensive, has SNMP model
support, and it allows external batteries, and uses the slighly larger
battery type, which enables longer run-time. Its worth finding a generator
compatible with it. I was surprised to hear you were having the problem you
represent.
Thats my take on it. But will be interesting what you guys find out on what
ends up working best.
Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
----- Original Message -----
From: "Felix A. Lopez" <[EMAIL PROTECTED]>
To: "WISPA General List" <wireless@wispa.org>
Sent: Saturday, June 30, 2007 3:33 PM
Subject: Re: [WISPA] Low cost generator
George/Mike: I worked for 6 years in deep UPS and
power quality at PG&E in Silicon Valley including
IEEE1159 and CBEMA curve. Our field work demonstrated
that if an automatic transfer does not take place at
one quarter of a cycle in a 60 cycle per second AC
power supply, then the sensitive logic controllers of
any network equipment, PLCs, etc will detect the
automatic transfer as a possible zero voltage
condition. The weblink provided below did not specify
the automatic transfer switch cycle time (see pages 18
to pages 23). A true UPS with continuous power will
actually provide your utility power source through a
battery system including power conditioning along
with generator backup. I had the opportunity to work
with the FAA in Fremont, California which has true
UPS> it was quite a setup.
So you may want to ask at what level you of continuity
you need for your wireless network.
I know of a few subject matter experts in the industry
should you need a consultant.
Felix
Energy and Wireless practioneer
Silicon Valley Area
--- Mike Hammett <[EMAIL PROTECTED]> wrote:
You can change this all via the APC management
software.
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
----- Original Message -----
From: "Eric Muehleisen" <[EMAIL PROTECTED]>
To: "WISPA General List" <wireless@wispa.org>
Sent: Saturday, June 30, 2007 12:23 PM
Subject: Re: [WISPA] Low cost generator
> Travis,
> How do you go about tweaking a UPS? We use APC
750's at most small tower
> sites. During the event of a power outage we use
1000watt generators but
> as you said...the UPS just shuts off and on,
repeatedly.
>
> -Eric
>
> Travis Johnson wrote:
>> Brad,
>>
>> You can adjust the sensitivity of the APC UPS's
to handle just about any
>> type of incoming power. We have run a tower off a
cheap Home Depot
>> 2000watt by adjusting the APC so it would not
keep switching off an on.
>>
>> Travis
>> Microserv
>>
>> Brad Belton wrote:
>>> We have found many (most all?) <10kW "job site"
type generators do not
>>> work
>>> well if at all with APC UPS. In the event of a
power failure we simply
>>> rent
>>> a 25kW towable diesel generator. Granted 25kW
is way overkill for most
>>> any
>>> HUB site, but apparently the larger generators
provide "cleaner" power
>>> that
>>> the APC UPS's are happy with.
>>>
>>> Does anyone have one of these 7kW Guardian
standby generators in use
>>> with
>>> APC UPS's? $1999.00 delivered with transfer
switch is a pretty strong
>>> deal!
>>>
>>> Best,
>>>
>>>
>>> Brad
>>>
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On
>>> Behalf Of Scott Reed
>>> Sent: Saturday, June 30, 2007 11:30 AM
>>> To: WISPA General List
>>> Subject: Re: [WISPA] Low cost generator
>>>
>>> The Guardian comes as small as 7KW for about
$2100 and goes up a long
>>> way from there.
>>> I have seen Guardians at cell sites and waste
water lift stations around
>>> here.
>>>
>>> George Rogato wrote:
>>>
>>>
http://www.electricgeneratorsdirect.com/catalog/product_info.php?products_id
>>> =538
>>>> I'm in the market for a generator and came
across this one.
>>>> The auto transfer switch and propane caught my
eye and I figured I'd
>>>> share it with the list.
>>>>
>>>>
>>>
>>>
>
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