The object of the Cray way was smooth power all of the time.
If there was time to power down ok. But spikes and sags were
not wanted when measuring signals and building monster machines.

Yours was a UPS of sorts as long as the 'oil' was flowing.

Martin

On 3/11/2015 10:37 PM, DoN. Nichols wrote:
On 2015-03-11, Martin Eastburn wrote:
The real isolation method is the flywheel method. Electrical to
mechanical that doesn't change with fluctuations.

AC mains drive massive multi-ton rock that spins. On that shaft is a
AC (generator) alternator. It generates the AC in single or three
phase. If the external AC shuts down, the rock keeps turning. It
turns for a long time without input power. So brown outs and twinkles
are never seen on the real load because the rock absorbs small and large
changes.

Cray Research used them for their buildings. Massive spinning disks of
rock.

Martin - been there, seen it.

Well ... our lab had something similar to make sure that the
fume hoods would not suddenly stop when some rather toxic gasses were in
use there. It also protected the rest of the building, too.

But -- it was not a separate motor and generator. Instead, a
*big* permanent magnet rotor three-phase motor kept the flywheel (steel,
not rock in this case) spinning. About 4' diameter by about 8" thick,
IIRC.

On the other side of the flywheel was a flexible coupling, an
electro-magnetic clutch (brake assembly from a B-58 I believe) and a big
Detroit Diesel.

A cabinet of electronics monitored the power. If the frequency
or voltage drifted out of spec, the clutch was allowed to transmit
torque, and the flywheel started the Diesel *right* *now*. In the
meanswhile, the permanent magnet rotor three phase motor became a
generator, and kept the building going. The flywheel for a little
while, and then the Diesel

Now there were three *big* breakers on a panel. One from line
to the motor, one from the motor to the load, and one from line to the
load. Once, someone switched off the line to motor breaker, and then
switched it back on -- without the benefit of the electronics in the
cabinet. Thus it connected about the time the phase had drifted 180
degrees. It drew a *lot* of current, and blew out the fuse on the pole
pig, and another closer to the substation on post. :-)

Enjoy,
DoN.