13 Oct
2024
13 Oct
'24
1:40 a.m.
On 10/12/24 20:07, Jon Elson via cctalk wrote:
On 10/12/24 16:25, Wayne S via cctalk wrote:
> Didn’t all the IBM mainframes use 400hz? Maybe ask the
> IBMers how they got 400hz.
> Also, can the local power company supply it?
>
Oh, the IBM 7090 series had a 400 Hz motor generator. The
mid-range IBM 360's (360/50 and 360/65) has
"converter-inverters". There was a star rectifier that took
in 208 V 3-phase and converted it to DC with an
inductor-input filter at about 300 V DC. This was then fed
to an inductor-input resonant inverter with fast SCRs at 2.5
KHz. All the power supplies for logic, memory, etc. ran off
120 V single-phase 2.5 KHz power. This kept the
transformers and filter caps and inductors very small. The
inverter SCRs were commutated by two smaller SCRs that
momentarily shorted the main SCRs through oil-paper caps.
The problem with this system is it didn't offer much
ride-through capability if you had crummy power quality.
Jon