Is there a 2 piece AC transformer?

T Chap

I am interested in a way to transfer 110VAC at a gap of 1/8". Is there something on the market like this?

Wireless energy transfer has not turned up a product off the shelf.

Don M

Look for inductive coupling.

LoopyByteloose

You might take a look at the link below.

There are air-gap transformers. And many transformer cores are constructed of interleaved pieces of sheet iron. And we have radio transmission through the air. But I cannot quite grasp the purpose you are trying to achieve. Conventional transformers already provide safety through isolation and the iron core is there to enhance performance.

And yes, inductive coupling is used in a variety of ways. In some cases, steel is surface tempered by induction heating.

http://sound.westhost.com/xfmr.htm

T Chap

The goal is to not have 110VAC on a wire that is attached to a track that moves back and forth. If the track is in it's most farthest position and stopped, it will need access to 110VAC. In other positions it does not need the AC. So the thought is to replace the cable that moves back and forth. The idea is that a transformer sits on the stationary part of the machine, and it's mate sites on the moving part of the track. When the moving part is such that the two parts are next to each other at around 1/8", AC will be available if needed.

LoopyByteloose

I suppose you are thinking mobile coils, and nothing about cores.

It is difficult to pass judgement on what might work as much depends on how many watts of power you really require. As the demands for power become greater, the more likely that plain old wire is your best choice.

If you want wireless power transmission, microwaves are touted as being optimal. 60 cycle AC has specific limitations due to its frequency.

Duane C. Johnson

And don't forget laser power transmission.

My other group I work with is doing this. See:
Kansas City Space Pirates
We transmitted a few hundred watts to a tether climber at an altitude of 1Km.

Our current project is to demonstrate untethered duration flight of a quadcopter for 48 hours.
This needs about 50W of power.

The basic concept is to use silicon PV cells illuminated with a 960nm infrared laser.
The PV cell conversion efficiency is about 40% or so.

OK, we are doing this at 100m to 4km.
But, if you only need to send the light a few feet this could be quite viable.
And you would not need any of the complexities we have with tracking.

What amount of power do you need?

Duane J

Duane C. Johnson

Oh, I forgot that acoustic can be used to transfer considerable amounts of power.
Especially in the 50 to 200kHz range or higher.

Duane J

Phil Pilgrim (PhiPi)

You could hack a Sonicare toothbrush. It has a non-contact charging stand that uses inductive coupling.

-Phil

Beau Schwabe

We still need to know your power demands for your project, but in the meantime do a search for rotary transformer.

T Chap

Thanks guys. I will find out the current requirement Monday, I know that it requires 110VAC to run.

Mark_T

There is a real issue with having a large and variable air-gap in a transformer core - you loose the very high inductance that limits the no-load current to low levels. Even a gap of 1/8 inch will utterly dominate the magnetic circuit (since good mains transformer cores have relative permeabilities in the 4,000 or so). A transformer primary without a magnetic circuit will pull very very high currents (~ 10 times the normal full load current, dissipating 100 times the power in I-squared-R losses).

Basically you can't do this at mains frequencies where very high permeabilities are pretty much a requirement. You want to move to air-cored transformers at much higher frequencies.

Gadgetman

Why transformers?

Sounds like the ob could be done with sliding connectors of some sort?
Subways, trams, even large trains does this quite well.
(Or if you look at smaller scales, model railroads, model racecars)

lanternfish

At 1/8th inch (3mm) why not use a contact arrangement??

Mark_T

Exposed 110V contacts seem to be rather a hazard to the unwary - but this is all inside a machine I believe. Some lighting rail fixtures already provide recessed sliding mains connections to the bulb-fittings - perhaps this technology could be adapted? Contacts can arc of course - I see the attraction of contactless power transfer but think its quite a challenge compared to a more prosaic solution (wires).

lanternfish

@ T Chap - It would be interesting to know what the the functio(s)n of the machine is/are. There may be another solution. Do you have photos?

lanternfish

Mark_T wrote: »

Exposed 110V contacts seem to be rather a hazard to the unwary - but this is all inside a machine I believe. Some lighting rail fixtures already provide recessed sliding mains connections to the bulb-fittings - perhaps this technology could be adapted? Contacts can arc of course - I see the attraction of contactless power transfer but think its quite a challenge compared to a more prosaic solution (wires).

Should have been clearer. Something along the lines of a simple low-friction plug and socket arrangement. And it could be prone to arcing and/or contaminant ingress.

Dave Hein

It seems like you just need a way to plug into an AC socket when at the far end of travel. A well-aligned plug and socket would do the job, with some spring tension to allow for a small amount of travel. The design requirements depend on how often the AC is plugged and unplugged. If it's only once per day you should be able to just use a standard plug and socket. If it is many times per day you would need something more rugged, or you would have to replace it periodically. It also depends on whether you plug and unplug when large currents will be drawn, which would create arcing.

EDIT: The design also depends on the conditions of the area, such as whether it is dusty or there is moisture present. Maybe you can provide more details about your applicaion. Offhand, it seems like the current use of a coiled extension cord is a reasonable solution. Why do you want to change this?