On Sat, 10 Mar 2007 08:14:11 -0800, "Chuck Tribolet"
wrote:

I didn't say true sine wave, I said modified sine wave.
I can't remember the last time I saw a square wave inverter for
sale. With digital control, modified sine wave is ASMOP (A Simple
Matter Of Programming).

A square wave inverter goes to +120V (or whatever) for 1/120 second, then
to -120V (or ...) for 1/120 second.

A modified sine wave inverter goes to +120V for a bit less than 1/120 second,
then to zero for a bit, then to -120V for a bit less than 1/120 second,
then to zero for a bit. The net is that the area under the curve is the
same as a sine wave. (Note: the above assume 60Hz. at 50Hz it would
be 1/100 second).

I must admit that I have always felt that the above should be called
"Modified square wave" as its resemblance to a pure sine wave is zero!
However that terminology would probably reduce sales.

--

Richard

Nb "Pound Eater" Parkend G+S
"Governments are like Nappies, they should be changed often."
(For the same reason)