Re: What kind of UPS do Europeans use? My modified sq wave UPS +PFC'edload = CRASH !
From: AC/DCdude17 (dude17_at_sacREMOVEbeemail.com)
Date: 07/09/04
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Date: Fri, 09 Jul 2004 17:13:07 GMT
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w_tom wrote:
> My point apparently was not obvious. Because computers are
> so resilient, then these plug-in UPSes "do it on the cheap";
> output dirty, crappy electricity when in battery backup mode.
> I was not talking about a UPS damaging computers. I
> demonstrated why plug-in UPSes output very dirty power - power
> that may be destructive to some small electric motors.
> Because computers are so resilient and would not be harmed by
> that "dirty" UPS electricity.
Isn't it sad that the UPS that's giving me a headache is one of the
smaller APC SMART UPS? This isn't supposed to be like the $29.99 junk.
> What is the frequency response of that PFC circuitry - if it
> really is a PFC circuit. Is circuit the EMI filter that is
> required by EU (and other) regulations?
I don't know the frequency response. The series reactor extends the
current rise time of the typical rectified load and it is tuned to give
a PF of >0.95 when used with a constant load on 60Hz 120V line.
The EU regulation now requires PFC on computer power supplies. EMI
filter was most likely mandated long before that.
> Then, does that
> filter impedance increase or decrease with higher frequency?
> These line interfaces vary in design so that only you can tell
> us what that circuit really is. But a line interface circuit
> must include a line filter. Does the line filter design cause
> lower impedance (short out) those higher frequency
> components? If so, then that is the answer of why a line
> filter (or PFC circuit) caused UPS problems.
See the PDF file in my previous post. It shows you how the typical PFC
is setup. I don't have any specific information on the actual
components in ballast.
>
> A UPS with high THD (too much power in higher frequency
> harmonics) would see a short circuit in that filter.
hmm mine says 28% total harmonics, 21% single harmonic.
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