On Sat, 19 Jul 2008 04:33:40 -0700 (PDT), wrote:

At a local plant, there once was a computer center. The room was fed
with a motor generator to provide clean power to it. I made an
inquiry and the unit might be available.

It has been years since I saw it, but it was a motor, probably 480
3ph, driving a generator with a large flywheel between them.

Any reason not to pursue it? Were the old mainframes run off of
anything other than 60Hz AC?

I am sure that it was a top quality unit when installed. I am hoping
that it would be a upgrade over the ST15 generator run by my 16-2
Lister CS. I am working at getting in there to inspect it.

They were a good low-tech idea in their day, even if they weren't
very efficient considering all that mass you had to keep spinning.

The ones that were motor=clutch=generator=clutch=engine would
provide output with only a momentary frequency and voltage sag as they
switched over - as long as the engine was kept hot and ready, and it
started normally when they dropped the clutch...

But make DAMNED sure you rebuild the bearings before you put it back
in service, and have thermostat sensors and alarms on all the shaft
bearings. Top and bottom halves of the shells.

With that much energy stored in a huge rotating mass, if one bearing
gets hot to the point of seizing up I can guarantee that all nine
circles of hell is going to break loose very quickly....

It has happened in the past, and it will totally trash the power
room and anything else that gets in the way like a bull in a china
shop - including people running to find out what all the commotion is.
People are soft and squish quite easily in those situations.

-- Bruce --