EMI Interfrence

[belango99]

Hi All,

We have 4 Nos of 60KVA UPS (MGE Make) in our facility, which located in Electrical Panel Room. Parallel to the UPS Room, we have helpdesk room which is been separated by a wooden plate.
The Problem what we are facing is the computer systems nearer to the wooden wall, the monitors( 05 Nos) of Computers shows some grid lines, shaky picture and colour changes happens. We installed the Systems from 2 mtrs away from where it was, then that problem stopped. When we enquired with UPS guys, they said it was due to EMI Interfrence

Kindly advice a solution in suppressing the EMI's from UPS room.

Thanks & Regards,
Elango.B

 

[ghostbuster]

This would appear to be low frequency magnetic field interference problem.Solutions are:Shield the monitors,shield the wall, relocate the monitors,or use lcd screens.

 

[dbuckley]

Most folks of my acquaintance wouldn't actually call this EMI interference, despite the fact it is; the term EMI is usually saved for fancier problems. This almost certainly is inductive coupling from the transformer(s) in the UPS as the Ghostbuster states, and LCD tellys are by far and away the easiest solution. It shouldn't be anything else as the UPS is a Merlin-Gerin (widely used in Europe), the monitor will be just a monitor, and they'll both be CE marked for European use, and the EMC standards there are pretty comprehensive. But putting a telly on a quarter megawatt of transformers is perhaps an unfair test of electromagnetic compatibility.

And this is one of those reasons that Back in the Day TV frame sync was syncronised to the grid, so that your picture may be distorted by magnetic fields from grid connected stuff, but it wouldn't wobble, and its the wobbling that gets peoples goat up.

 

[robbietan]

why not adjust the monitor frequency of your monitors before going out to buy that LCD screen?

that is, if you cant really move the monitors away from the source.

 

[kc8dxx]

We've dealt with this problem before in some systems. The most cost effective solutions are as described above, move the motor or change to LCD monitors.

If you choose to shield, then you will need a material called mu-metal. It is extremely expensive, and must be worked by the OEM into the proper shape. If you, say, drill a hole in it after it's built, there is a chance that it will have a dramatic loss in it's shielding properties. You can choose to shield the wall, or build a shield around the monitors. The shield around the monitors must cover the rear and sides, and be designed such that heat can still escape. From personal experience, several iterations will be needed to get it right.

There is a lot of conflicting evidence regarding whether or not humans are affected by 60hz magnetic fields. I would suggest that it can't be a good thing, and IMHO would suggest rearranging the room so that the monitors see no distortion.