Concentric toroids instead of slip rings?

[ab1jx]

On at least a small windmill putting out AC like from a converted motor, would it work to have one toroid mounted horizontally so that it rotates on the yaw bearing then another stationary fitting outside of it? Toroids are supposedly self-shielding but I'm not sure that applies to putting one inside another.  I imagine the braking would be significant at high power levels so if you got a good gust of wind it would lock the yaw bearing in place.  I should try to simulate it, I just thought maybe somebody had tried it. The converted motor would drive the inside toroid with AC then you put bridge rectifiers on the outside one. Not sure it would work with multi-phase.

If a toroid won't work because of the self shielding then maybe some sort of coils so it's like a transformer with the primary rotating inside the secondary. I'm tired of replacing wires.

[joestue]

you mean coupling the power through concentric toroids?

that could work if you use a rotating transformer.. similar at least in concept to what is in a VCR head.
rotating transformers don't work in the toroid topology unless you can accept less than 180 degrees of practical rotation, perhaps up to 240 degrees of rotation but the floating secondary will be 60 degrees wide, thus low power throughput.

there are two other topologies that work for rotating transformers but you'll be dealing with high axial forces.. or expensive iron cores.

i don't see this being practical for power, but if you want to send a few watts to drive a brake, or send data and power through it to drive a gear motor to change the pitch of the blades, then that would be practical.

[Flux]

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