There is no DEC process cabinets that is really three phase. Some of the power
controllers (notably the VAX 780 and the larger PDP-11’s), that had three phase cords on
them but all they do is split out the three phases as three 120V circuits.
I believe Armando Stetner made use of this when he ran a VAX in his hotel room at one of
the conferences, he just ran 120V extension cords all over the place to get it up.
There are some of the old washing machine harddisks that were designed to run on 208/240
(still single phase). I’m not sure if the RP06’s fell into this category but some of the
Storage Tek drives did.