Hacker News new | ask | show | jobs
by Night_Thastus 199 days ago
It's not about pure sine wave - it's double conversion. Only double-conversion would actually isolate the equipment from EMI on the line. Without that pure sine wave won't do squat for EMI.

And one of those, even the cheapest ones, run for about ~$900. And they are LOUD.
4 comments
LoganDark 199 days ago
Are they loud because they're double-conversion or are they loud because they're designed for server racks? When I search for double-conversion online I can practically only find rack-mount solutions.
link
arde 199 days ago
They're loud because silence is not a priority in their design and their fans run non-stop.
link
Night_Thastus 199 days ago
They're loud because unlike a regular UPS they need to run continually to convert the power back and forth. That generates a lot of waste heat, which fans must remove.
link
icehawk 199 days ago
I have several that are not rackmount (SU1000XLCD/SU1500XLCD), and they're all loud because they run fans constantly.
link
saltcured 199 days ago
I wonder if modern motor and power control tech could be adapted to make a desk-side motor-generator set that is efficient enough to rival an always-active, dual conversion AC-DC-AC UPS.

How efficient could a small AC->motor->generator->AC chain be with a modest flywheel mass to provide cycle-to-cycle stability?

Could it ever make sense to put one of these after a standby UPS so the output is always filtered by the motor-generator but the UPS only has to kick in for outages?

link
mrob 199 days ago
One advantage of a motor-generator set is that it's relatively easy to get high-voltage isolation using an insulating shaft. It might be possible to build something that could survive nearby lightning strikes to the incoming AC line. I don't think any standard UPS can do this.
link
andyferris 199 days ago
The portable lithium battery "powerstations" double as great double-conversion UPS in addition to their intended outdoors (camping, beach, etc) activities, and depending on capacity go for less than 900 USD. It's only noisy when fast charging or providing high currents.

Definitely had various computer equipment plugged in to ours and it was great (I didn't specically test for EMI).

link
monster_truck 198 days ago
In my testing combining this UPS with a cheap power conditioner, the noise floor is more than sufficient.

Sure, it isn't the -80db noise floor of a P-2400, but I'm not running a broadcast studio

link