Faraday Cages & Bringing Power Into Them

[welectrical]

Not sure if there's a better sub to post this in, but I am designing a job where a faraday cage is being installed for brain scanning / reading. However, the room needs power for lighting, equipment use, etc. It also needs data connections within.

I know MRI rooms are common faraday cage applications, how do you bring power/data into them without destroying the cage's properties?

Does one use non-conducting conduits within the room and outside of the room then use a shielded cable that is grounded to the room's cage?

 

[OldSparks]

An isolation transformer immediately outside the cage and all conduit bonded to the cage (on the secondary side of the transformer) should do the trick.

 

[welectrical]

An isolation transformer immediately outside the cage and all conduit bonded to the cage (on the secondary side of the transformer) should do the trick.

Ah, nice! Bond the iso transformer to the cage as well I assume?

 

[suemarkp]

You can also just install power line filters. These tend to block everything much over 60 Hz. I've bought them in 60A and 100A sizes. Same problem exists for data lines that penetrate. Fiber is the best for those, but sometime you just have to use wire.

Conduits inside that pass through ideally would have a non-metallic segment just at the room penetration. You can buy waveguides to pass fiber through or just use a small conduit that is at least 5X long as its diameter. HVAC penetrations also typically have waveguides installed in the duct and non-metallic duct couplings at the room perimeter.

Look for shield room filters, or how to build shield or TEMPEST rooms. Common suppliers are ets-lindgren, and genisco. I'm not sure how much attenuation you need to achieve or at what frequency range. That affects the filters and the design.

 

[Speedskater]

Ralph Morrison writes about this in some of his old books.
Probably his 1990 "Grounding and Shielding in Facilities" is the best.
His books are often available used for about $20.

 

[welectrical]

Follow up - I wound up using RF filters on either side of the penetration with non-metallic conduit as suemarkp mentioned.

This was confirmed by some MRI room design drawings I received from a friend for coordination.

 

[GoldDigger]

The Faraday cage is necessary to keep the subject's brain from covertly transmitting information to a brain outside the room.