EMI from High Voltage Transformer 1

[CK01]

So I'm on a REALLY big project which I can't go into, but there is a REALLY big transformer 35kv primary / 1500kva in a room right next to the main server room and there is this huge fear of EMI from that XFMR.

We want to put up some of that EMI shielding fiber board on the drywall walls but I can't find a product.

Has anyone ever used this kind of fiber board before?

 

[tweege]

could you use some lead-lined wall boards, like are used in rooms that house x-ray machines? i realize we are talking about a different kind of energy here......don't know if lead would help with emi or not.

 

[tweege]

check this site out:

http://lairdtech.thomasnet.com/category/metallized-fabric

 

[DTSMAN]

Start here

http://www.ramayes.com/Copper_Screen_Shield_Room.htm

Bo

Remember,
If the women don't find you handsome,
they should at least find you handy.
(Red Green)

http://www.redgreen.com

 

[CK01]

Wow, this might actually be the schizel!

I'm not entirely sure what the EMI affect would be exactly but I think if there was an area in this building that would have an affect it would be a 35K volt / 1500kva transformer would be it.

My personal experience as an electrician in the field back in the day is you get more problems from Cat cabling being run parallel to electrical for long distances and really only like electrical feeders & motor circuits.

Thanks for the info.

 

[wires]

Neither of those products are designed to handle the sort of issue you are facing. The first is for MRI use and the second is for RF fields.

If the transformer is in use now you need to find someone familiar with this sort of issue. They might be able to do a survey with a magnetometer / gauss meter to determine what the field strength you are dealing with. This is not a job for guess work.

I had a client who's receptionist had all sorts of problems with her computer. Disk problems, network problems and I noticed that the monitor (CRT) looked funky. There was a locked room sharing the common wall with her workspace and after getting it unlocked there was a transformer for the lighting on the entire floor less than 3' from her computer. Relocating her to the other side of the room fixed the problem.

Sometimes you just have to find a different location for certain types of occupancy. You wouldn't put a rifle range next to a food preparation area. Sometimes you just have to move one of the uses.

 

[CK01]

Agreed and the relocation option was considered.

However, we're not talking about someone's desk. The XFMR is as big as a shipping container and the server rack room next to the XFMR room is... Well, a server room. As big as they come.

There has to be a product out there to block EMI.

 

[wires]

I realize the sizes. I checked eBay for transformers of the size you mentioned. It looks like these units weigh around 3-5 tons. My feeling that the magnetic field of a 1500kVA transformer is substantial.

Realize that you are not trying to suppress higher frequency energy like RF but a much lower frequency magnetic field at 60Hz. For example the RA Mayes specs show greatly diminished attenuation as frequency goes down:

USC-26 TYPICAL ATTENUATION
21 dB at 1 kHz, 58 dB at 15 kHz, 90 dB at 100kHz

USC-44 TYPICAL ATTENUATION
15 dB at 1 kHz, 40 dB at 15 kHz, >50 dB at 100kHz

Some decent reading can be found here:

http://www.fms-corp.com/resources_pubs_bioelectromagnetics96.php4

The units I saw on eBay were all configured in a linear array. The study suggests that "secondary low voltage phase conductors and neutral connections were the largest source of magnetic fields". Test site #2 is relevant to your problem. Sounds expensive!

Good luck!

 

[wires]

Check this out:

http://www.magnetic-shield.com/products/shielding.html

"Unlike RF (Radio Frequency) shielded rooms, magnetic shielding does not usually require a full, six - sided enclosure with sealed doors in order to solve a problem in a room. The shielding alloys are typically applied on the surface (floor, wall or ceiling) between the interference source and the area to be protected.

 

[CK01]

It appears that testing is going to be needed to really put this issue to rest and unfortunately we have to build the walls WAY before we turn that XFMR on.

 

[wires]

A couple of things to keep in mind.

1. Be sure the wiring coming off the transformer secondaries is kept as close together as possible. In other works don't tap the neutral on one side of the bus bars and the phase wires on the other. The transformer itself is designed to minimize magnetic leakage since such leakage is power loss.

2. Give the folks at Magnetic Shield Corp a call. They have substantial experience in this field and may be able to give you some pointers. I doubt the issue you are dealing with would be unique in their experience. I recognize their logo from old tube equipment, they have been around...

This has been a very interesting bit of research. It has some parallels to marine wiring that I am familiar with. In marine wiring minimizing magnetic fields around the cockpit is essential due to the effect on the good old compass. In such wiring it is important to run each circuit on it's own pair of wires to minimize magnetic fields. Some even twist the wires to suppress the field even more.

 

[CK01]

Thanks.

I'll call them.

Well, actually I'll check into if it's OK to call them 1st.
Then I'll call them.

Security clearance levels I believe restrict me from just calling any old soul up to talk about... stuff.

Feel me?