Agree with Joestue. possible for signal coupling but totally impractical for power transfer at the sort of frequencies you will have to deal with.
There are a few odd sites where cables twist up and where slip rings are needed. Properly engineered slip rings are fine but a half baked codge often causes lots of trouble.
I have used engineered slip rings on 3 phase without trouble. On small mills on a dreadful site I have used a fairly simple scheme to carry the dc, A centre brass rod is fitted (insulated) in the yaw tube and an insulated brass pad on the yaw head rests on it, the weight makes a totally reliable connection.
The negative connection is carried via the yaw bearing. This is not so easy, pipe on pipe with an offset force makes good contact when new but with grease you have an inevitable spark eroder and with vibration there is occasional loss of contact.
I have ended up including a crude brush and slip ring within the set up, a brush box containing a copper/graphite or brass brush is fitted to the outer tube and the brush has a good spring that presss it hard on to the inner tube, pressure and just a thin film of lubrication seems to prevent the occasional sparking that causes the spark erosion.
The idea was copied from a Lucas Freelite in use on this site. The Freelite just has cast iron running on a steel pipe and does occasionally spark but it does no harm, there is obvious wear from friction and sparking but it has been running since 1939.
It has a dynamo so only needs 2 dc leads.
My machines are alternators and have the rectifiers mounted up on the yaw head so that the centre connection brings down dc positive and dc negative goes via the yaw bearing and the simple brush. These have given no trouble in 10 years.
Flux