Power Factor correction with CFL bulb question?

[BB.]

Unfortunately, PF issues can be a relatively big issue for off-grid applications...

For example, the MorningStar SureSine TSW inverter is rated at 300 watts continuous at 25C... In reality, it is probably rated at 300 VA (Volt*Amp) or:

VA = Watts/PF ; or Watts = PF * V * A

Say you have 10x 13 watts CFLs with a PF of 0.5 (bad, but I have seen worse).

Somebody looking at the specifications--they see a 300 watt inverter - 130 watts = 170 watts for other loads... A laptop PC at 60 watts and a 25 watt Halogen desk lamp looks doable... But--the PC is an old one with PF = 0.6 -- we add everything up in watts and VA:

Watts = 10 x 13 Watts + 60 Watts + 25 watts = 215 Watts
VA = (10 x 13 Watts / 0.5) + (60 Watts / 0.6) + 25 watts = 385 VA

So--if you add everything up in watts--you are running at 72% of the inverter's rating.

In VA, you are running at 128% of the inverter's rating...

Battery/solar panel wise--you are still running 215 watts (+ losses). But your inverter is actually overloaded at this point (may shutdown in hot weather -- or may not last as long because of elevated operating temperatures). Also--your wire is carrying more current than you planned on -- so you may have more voltage drop and/or more wasted energy than you allowed for.

PF issues have hit large companies before (decades ago, a local credit card processor using a whole building full of, then new, PC's kept burning out wiring and popping fuses--even though the the circuits were well under the power ratings--bad PF was the cause).

-Bill