13 Oct
2024
13 Oct
'24
3:26 a.m.
On 2024-10-12 7:40 p.m., Jon Elson via cctalk wrote:
On 10/12/24 20:07, Jon Elson via cctalk wrote:
What did they use for air conditioning?
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