[RE-wrenches] Mac compatibility with Modsine

[Hugh]

>  Greetings,
>
>    Does anyone know if newer Macintosh computers are still 
>incompatible with Modsine inverters, and how about Mac loptops ?

I have been using Macs since the mid 1990s and much of the time 
plugging them into 'mod-sine' inverters such as the old Trace U 
series and DR, and various lightweight types too.  Never had a power 
supply problem (other than the plug falling off the wire due to 
abuse).  I started out with desktop Classic and moved through 
Powerbooks of various vintages to the Macbook pro.  It seems to me 
that computers are the easiest loads to run on mod. sine.  Washing 
machines and cordless drill chargers are the problem areas.  And 
buzzing noises in telephones, hifi and compact fluorescent lamps.

Peak voltages can go pretty high with mod.sine since peak is pegged 
to battery voltage that can go high during equalisation.  This can 
potentially blow up some electronics (never a Mac to my knowledge) or 
cause the inverter to shut down.

So far as I understand it, mod sine means that the rms voltage will 
be correct, whilst the peak attempts to be around the correct value 
for a sine wave (but this depends on battery voltage and load).  The 
older 'square wave' inverters had rms and peak both at the exact same 
voltage, which was not ideal, hence the invention of mod. sine with a 
pause at zero between pulses.  Adjusting the pulse width allows the 
mod. sine inverter to deliver a constant rms voltage that is usually 
less than the peak, roughly 71% like a sine wave.
-- 
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk