clare @ snyder.on .ca wrote in message
...
On Wed, 11 Feb 2004 19:58:40 -0800, "Tim Ward"
wrote:

Mechanical INS are three phase, but they have battery back up.

Cool! Where do they get those 3-phase batteries?

Same place they get the AC batteries, I suspect.

It has more to do with the DC accelerometers and designing for reliability.

Back when 707s ruled the world there were mag amps for operational
amplifiers and mica capacitors were what could survive comertial operations
and storage. A three phase DC source with a battery is how clean DC power
could be made reliably.