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Old 7th December 2022, 01:18   #3  |  Link
Emulgator
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Join Date: Feb 2007
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Power suppliers have to take great pains to supply stable mains
with low harmonics and low losses under today's varying load conditions.

A cheapo generator is quite load sensitive and would like to feed an ohmic load only, like a pure resistor.
But not much is ohmic anymore these days.

Incandescent Lightbulbs are PTCs already with up to 10x cold starting current,
A simple protection will not like that, but can be cheated by making it slow responding.

Already a standard linear PSU (Si rectifiers feeding large caps) makes up for decent charging current ripple
which loads the generator only peakwise.
Still a simple generator protection should be able to handle that going after mean value (or high-end RMS) only.


Now the UPS will have a SMPS upfront to charge the batteries.
That inrush current alone may trip the generator's protection, let alone the load waveform.

Next challenge: For efficiency that SMPS may have a PFC in front, buzzing away on the mains input.
Waveform is even more complex now, with large flyback voltage.
A simple protection will not like that and will most probably trip.

Batteries then feed Output SMPS as DC/AC converter. The usual mess of hacked current....

Rule of thumb: You will need to provide double the capacity for any SMPS to follow, not half.

And as Shark says: Look at the PC's service tag.
Newer notebooks have multi-region PSUs.
These are SMPS bricks for 90..260V range in best cases,
or 100..240V range (more often seen) which can handle lots of fluctuation.
No need for a UPS inbetween in that case.
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Last edited by Emulgator; 7th December 2022 at 01:27.
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