# Inverters

Discussion in 'Electronic Basics' started by Sailor Bob, May 29, 2005.

1. ### Sailor BobGuest

Can anyone tell me if an inverter actually uses additional energy t
convert DC to AC? Is it a percentage in direct proportion to th
conversion

thank yo

Bo

2. ### John PopelishGuest

Yes, it uses additional energy that must escape as heat. There is
some minimum loss, just to run the converter, unloaded, some
proportional losses, and some losses proportional to the square of the
load. If the designers concentrated on efficiency, all these losses
may amount to 5% to 10% of the full load output (90to 95 % full load
efficiency. All units are zero percent efficient at no load.

John gave you some good answers. Let me add one thing -- if you model the
input power going to an inverter as something like:

Pin = A*Pout+B (watts)

....where A is perhaps 1.10 (~10% losses or ~90% inverter efficiency), the
constant loss term (B) tends to be proportional to the _maximum_ power the
inverter was designed for. It's not uncommon to see something like a 5,000
watt maximum inverter that'll sit there and dissipate 25 watts under no load,
because the designers figured normally you'd probably be running 2-4kW and,
hey, what's 25W vs. a few kilowatts? On the other hand, something like a
little 300W inverter would hopefully dissipate, say, no more than 3W under no  