Motor generator

[Chuck Guzis]

Very large machines, certainly.  There were "site preparation" documents
that detail this.

I can quote from the 1975 edition of the STAR-100 hardware manual on
bitsavers (PDF page 25):

"Power for the basic computer consists of one 250 kva, 400 Hz motor
generator set.  The motor-generator set has the capability of providing
power for the CPU, MCS, I/O and the MCU. The optional memory requires
the addition of an 80 kva motor-generator set."

Granted, the STAR was a monster of a machine, but similar setups were
used for CDC 6000, 7000 and Cyber 70, 170 machines and others.   That
doesn't include the refrigeration necessary for the chilled water
supply.  I/O devices such as card readers and tape drives often used a
"split" supply with the 400Hz supplying the electronics and normal 50/60
Hz AC supplying power for motors, etc.

Small S/360 systems were operated from standard AC distribution.  I
don't know where the breakover was for IBM S/360; probably not for the
model 30, 40, or 75.   The 195, I suspect did use an MG set.

The 7090 certainly used MG sets.  From the "Power Supply and
Distribution Manual"
(http://bitsavers.org/pdf/ibm/7090/ce/7090%20Power%20Supply%20Control%20and%20Distribution%20223-6904.pdf,
page 5):

"The IBM 7608, a power converter or motor-generator set which converts
incoming 60-cycle three-phase (3Ø), 208v power to regulated 400-cycle 3Ø
208v power."

--Chuck