CDC mainframe shops used 400 Hz three-phase power for the CPU and the display console (DD60). I don't know if it was used in other places. The advantage of 400 Hz power is smaller transformers and filters; in addition, it was generated by motor-generator units which produce good clean power even if the building receives crummy power from the utility. There is a by-invitation list of CDC experts and fans, I included a BCC to the list owner on this reply. There might be help available from that group. There are two considerations for disk drive power. Older disk drives often use AC induction motors, which tend to be three-phase motors. With induction motors, the rotational speed is determined by the motor design and the power line frequency. But I haven't heard of induction motors operating from 400 Hz power; those would spin quite rapidly indeed unless they had lots of poles. 50 or 60 Hz induction motors are fairly common, which is why you tend to see 3600 rpm nominal rotation specs for a lot of disk drives. The other aspect is DC power supply design. If a supply is designed specifically for 400 Hz input, it won't operate properly from 60 Hz mains. The transformers will be too small, and the filtering inadequate. But if the spec says 50-400 or 60-400 Hz, that means the transformer and filter sizing is done for mains power (50/60 Hz) and the transformer core is constructed to still have acceptable losses at 400 Hz. That's not common but I could imagine CDC doing this because of their use of 400 Hz. If you have such a wide-range device, just feed it mains power and all will be well. But, say, a CDC 6600 central processor can't be powered by 50 or 60 Hz mains power. As for 3-phase vs. 1-phase DC power supplies, that just means there are more rectifiers and smaller filters because the ripple is reduced by rectifying 3 phases. You might be able to get away with feeding such a device 1-phaser power but it would probably be marginal, and 3 phase would be a better option if you can get it. There are converters that do a decent job, and depending on where you live you might just get it from the power company. paul

On 2/18/18 9:34 AM, P Gebhardt via cctalk wrote: "BM101" shown in the pictures is what you should be looking for 90310500_Literature_Catalog_Jan85.pdf on bitsavers page 22 shows BM101/103 multiple disk drive gen desc p/n 41248900 oper, instal ckout maint ce man theory,diagrams, wire list p/n 41249000 parts data p/n 41243700 '412' is Normandale operations code # I've got 41249000 ./___UNSORTED/41249000J_BM101_Theory_jun72.tar