Motor generator

[Curious Marc]

The IBM 7090 used a motor generator, IBM model 7618 apparently
http://ed-thelen.org/comp-hist/7090-PowerSupplyControl&Distribution-223-6904.pdf
Marc

> On May 4, 2021, at 5:03 PM, Jon Elson via cctalk <cctalk at classiccmp.org> wrote:
> 
> On 05/04/2021 06:06 PM, Donald via cctalk wrote:
>> In the deep recesses of my mind I seem to remember something about S/360
>> machines using a motor generator.
>> If I am right was this to create a stable power source at a certain
>> frequency or voltage?
> Nope.  I know the 360/50 and 360/65 used a "converter-inverter" that converted 208 3-phase
> to about 280 V DC, then inverted it with a 4-SCR inverter feeding a resonant transformer to
> create 120 V 2.5 KHz regulated single-phase sine wave power.  All the critical loads in the CPU ran off this power.  Notably, the I/O power sequencer and console lamps power supply did not run off this power.  The converter-inverter made an absolutely HORRIBLE whine that could be heard 20+ feet from the back of the CPU even in a very noisy machine room.
> 
> The only "360" machine I know of that used 415 Hz was the Model 195, although I can guess that
> the 360/85 used 415 Hz also, as it was essentially the prototype of the 370/165.
> 
> The 370/145 used an internal motor/generator set in the back of the CPU cabinet to produce 120 V 415 Hz 3-phase power.  Larger 370's generally were provided with UPS's instead of M/G sets to create the 415 Hz power.
> 
> Also, the 709X series ran off 400 Hz from a motor/generator set.
> 
> The 360/50 and /65, at least, were pretty sensitive to noise and short dropouts in the mains supply.
> The 370's with the MG sets rode through pretty severe power dips with no effect at all, until the disk drives and tape drives went offline.
> 
> Jon