Supercomputers, fishing for information

Jon Elson elson at
Sun Nov 6 12:57:37 CST 2016

On 11/06/2016 12:46 PM, Chuck Guzis wrote:
> On 11/06/2016 09:18 AM, ethan at wrote:
>>> But smaller than the Crays of the era. If it doesn't run on 400Hz,
>>> it's a 'mini' supercomputer.
>> Hmmm I knew the earlier Crays often had motor generator setups and
>> such but I thoght that was just for power filtering and maybe
>> flywheels for ups setups. Didn't know they were 400hz! Odd!
> Not at all--that goes back at least to the 1960s.  Consider the CDC
> mainframes--MG sets providing 3-phase 400Hz power to variac-regulated
> 3-phase fullwave rectifier setups.  The ripple frequency is 2400Hz and
> has a very high DC component.
All 370's ran off 415 Hz 3-phase power.  The mid-sized ones 
had the motor-generator set built into the back of the 
machine.  The 415 Hz (regulated) power was transformed to 
low voltage and run through an inductor-input filter and 
then series pass regulated.  They had a circuit they called 
an "electronic capacitor" that pulled extra current through 
the inductor during the voltage peaks, so the inductor 
carried enough current during the voltage valleys.  This 
reduced the ripple current on the capacitor banks.

The 360s ran off single-phase 120 V 2500 Hz power, produced 
by a "converter-inverter" unit in the back, that converted 
utility 3-phase power to DC, then inverted it with an SCR 
inverter.  This made the DC power supplies in the machine 
quite small.  Since they ran off regulated 2500 Hz power, 
they dropped only a very small voltage across the 
series-pass transistor.


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