On 29 Oct 2020 00:44:08 GMT, Bob Eager wrote:

I doubt if a 650W generator or anything other than a professional

grade hi surge current server rack UPS would be able to power a
compressor motor. The peak current surge to start is very high
for a
few cycles.

My 2 kVA diesel set just changes exhaust note a tiny bit when a
fridge freezer kicks in. Rather more of a change in not if you drop a
2 kW fan heater on to it, no noticable speed chnage. B-)

That's why ordinary UPSs all insist they can't be used with laser
printers - they are unhappy with even very brief over-current
events
when running on the inverter.

UPS's don't like CRT monitors from powered down either. OK if already
up and in standby though. Degausing coil is a hefty load for a second
or so...

Despite the ring circuit being correctly wired and being quite short,
and there being little load on it...when I switch on the laser printer,
the UPS shifts taps to compensate for the voltage drop - it is clearly
audible.

That sort of surprises me, there will be an inrush as the filter
capacitor and PSU capacitors charge but wouldn't expect that to be
greatly different to a PC. Think I'd be looking to see if the UPS is
a bit "sensitive" or what the volt drop drop is on that ring when
loaded. May be indicating a slightly iffy joint somewhere.

--
Cheers
Dave.