UPS for FreeBSD
starrtennis at gmail.com
Mon Dec 1 16:43:50 UTC 2014
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On Sun, Nov 30, 2014 at 8:11 AM, Paul Pathiakis via freebsd-questions <
freebsd-questions at freebsd.org> wrote:
> To all that responded on this thread:
> Thank you. I feel I have a better understanding of all this now. :-)
> The time spent to better educate others and myself is welcome and so
> "FreeBSD Community".
> On 11/30/2014 00:33, John Johnstone wrote:
>> I agree this thread is extremely long so I'll consolidate.
>> On 11/28/14 10:55 AM, Paul Pathiakis via freebsd-questions wrote:
>>> Again, these UPSes are not double sine wave, they are stepped. You can
>>> get one for cheap, but, again, how much value do you place on your
>>> server and the information it has? If you're looking at APC, you have
>>> to look at their 'server class' UPS. They start (I think) at 1500VA and
>>> about $850.
>> I think things could be clearer about the terms "double sine wave" and
>> "stepped". I think it should be made clear that although a UPS that
>> outputs a 60 Hz square wave is producing a poor approximation of a sine
>> wave, better designs still produce a sine wave in a stepped fashion, just
>> with a higher number of steps. One that produces an infinite number of
>> steps would be indistinguishable from a pure sine wave.
>> On 11/28/14 5:04 PM, Paul Pathiakis via freebsd-questions wrote:
>>> I found this which seems to be pretty solid. I believe it someone
>>> mentioned UltraUPS.
>> This whitepaper refers to the stepped approximation of a pure sine wave
>> in their design:
>> "The inverter reconstructs a sinewave from the DC using PWM (pulse width
>> modulation); a method that “digitizes” the DC into various width pulses
>> to make an AC sinewave."
>> The number of steps needs to be high enough to not cause problems.
>> On 11/27/14 2:25 PM, Darren Pilgrim wrote:
>>> Sine-wave approximating inverters do bad things to any power supply
>>> with a regulator cap (which is everything that won't catch fire on
>>> its own). The issue is the high frequency components and the
>>> hundreds of under- and over-voltage events per second inherent to the
>>> stepped square waveforms used (every step is a spike or sag).
>>> UPS manufactures know this is bad, so they try to hide it by calling
>>> it "modified sine wave", "quasi sine wave", "simulated sine wave",
>>> "PWM sinewave", etc., and hope you're dumb enough to fall for it. I
>>> have yet to see a consumer UPS that doesn't do this.
>> I wouldn't say it fair to interpret UPS manufacturer's descriptions of
>> their methods of simulation as "hiding".
>> You need to buy a server-grade UPS to get something that won't damage
>>> your electronics. APC SmartUPS, Cyberpower PFC Sinewave or Smart
>>> App, Eaton 5P/PX or 9 series, Tripp Lite SmartOnline, etc.
>> On 11/28/14 1:22 PM, Paul Pathiakis via freebsd-questions wrote:
>>> "Simulates" utility power. This is the sneaky little bit of
>>> marketing. Saying it's sine output.... It is, but it's simulated.
>>> I've been roped in by the APC marketing machine previously.
>> As far as "simulated" being a bad thing, by definition all UPS's have to
>> simulate a sine wave once the AC power goes away. It is just a question of
>> how close an approximation is it. There's no question that a 60 Hz square
>> wave would be a poor approximation.
>> As the number of steps increases, the magnitude of the "high frequency
>> components" and "under- and over-voltage events" becomes so small as to be
>> negligible. There are plenty of "server-grade" UPS's that produce a step
>> approximated simulated sine wave as the Controlled Power whitepaper states.
>> One aspect to consider is that if a UPS isn't an on-line design, any
>> negative effects experienced by the load due to the quality of the output
>> sine wave will only occur when the output is being produced by the UPS
>> during a power failure. It's reasonable to expect that this is going to be
>> a short interval which in many cases may not cause any power supply
>> John J.
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