I have an APC UPS that puts out modified squarewave (the marketing
people calls it modified sinewave) when on battery. I connected a
fluorescent fixture with an electronic ballast containing passive L-C
power factor correction. The UPS crashed and shut down as soon as it
switched over to battery. The UPS doesn't have issues with residential
electronic ballast such as CFLs which doesn't have a PFC circuit. It
must not be getting along with the PFC. UPS is rated at 600VA. Light
only takes 100VA.
Electronic ballasts have the identical rectififier+capacitor front end
as switchmode power supplies used in computers. Like electronic
ballasts, computer power supplies are available with PFC. They're rare
in the US, but EU legislations mandated power factor corrected power
supplies on new computers.
An example of power factor corrected PSU:
The passive PFC on a power supply like the one linked above is the same
type as the one in my ballast. Since computer power supplies in the US
typically don't have a PFC, we're fine, but how do Europeans get their
PFC equipped computers to get along with their UPS? I searched "PFC
UPS" on Google and looks like I'm not the first one to have issues with
a UPS interecting badly with a PFC power supply.
My UPS shares the transformer between inverter operation and charging.
It's a steel core transformer with center tapped secondary. When
operating on battery, the center tap on secondary is tied to one of the
battery terminals and the MOSFETs switch the other terminals back and
forth between the two taps on the sides. A relatively common design.
18 years ago