Don't really know them, but I had a look at the brochure for the RT series UPS and I am confused. They claim it is an online double conversion UPS, and yet they say when not running on battery, the efficiency is 98% (ECO mode). When running on battery, it is 87%.
http://powershield.com.au/wp-content/uploads/Brochures/Centurion_RT_Print_31032016.pdfJust doesn't make sense to me. It sounds like it is a standby UPS of some sort. If they have built a true online UPS and then offer an eco mode that turns it into a very expensive standby UPS, it sounds like a very odd decision to me. No way do they have a double conversion system with 98% efficiency.
The key principal on an online UPS is that the output is always coming from the inverter (unless an overload or inverter failure sends it to bypass), so what happens on the mains has absolutely no effect on the output waveform.
There is a huge difference in the design decisions between a standby UPS and an online UPS. The online UPS has to be designed for many thousand of hours of constant inverter use. A standby UPS may in its life have the inverter running a handful of hours.
If you find out anything, let us know. Particularly if they have done something brilliant.