On 1/1/22 1:56 PM, W2HX via cctalk wrote:
The other benefit to 3phase power to something like a computer is that the
filter caps required can be much smaller. Once you rectify three phases 60* you
get MUCH less ripple because every 60 degrees you have a new peak arriving.
When you have a real gas (electron) guzzler like one of these, DC filtering
becomes an issue.
But, they DIDN'T! All power supplies on the /780 were
single phase.
On the IBM 370/145, they used a motor/generator set to
convert 208/3 phase 60 Hz power to 415 Hz 3-phase 120 V
regulated power, then fed that to 3-phase
transformer/rectifiers, and finally to low-drop regulators.
They also used "electronic capacitors", which was a scheme
to pull extra current through the smoothing inductor during
the voltage peaks, to even out the ripple. The 370/145 had
2 power supplies, one for +1.25 V 390A and the other for -3
V 390A.
Jon
