-----Original Message-----
From: Paul B. Webster VK2BZC <paulb@MIDCOAST.COM.AU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: 09 April 1999 12:59
Subject: Re: Energy in a capacitor


>Wagner Lipnharski wrote:
>
>> Some IBM large mainframes use an external "motor-generator", bigger as
>> a fridge, an huge motor and generator.  The motor ... mechanically
>> drives a 400Hz 208Vac also tri-phase generator. At 400Hz, the wires
>> and cables can be smaller,
>
>  OK, he *meant*, at 208V three phase, the wires and cables are smaller.
>
>> also the transformers, and the filtering capacitors.  As the mainframe
>> computer is almost 1/5 of its size just power supplies, you can
>> imagine the gain in space of just using 400Hz instead 60Hz...
>
>  Indeed.  This was the 1960s version of the switchmode supply ;-)
>
>  Aircraft used 400Hz and/ or 1600Hz during and presumably, prior to
>WWII.  Of course, in a plane, you don't notice the "singing" from the
>mains, do you?
>


Aircraft today are still using 115 volt 400hz AC and 28 volt DC.