Imaging Equipment Failure - EMF Power Quality...IDK!

[living2learn]

Dear Experts,

I need some insight on this. I have an ultrasonic machine (attached cutsheet) that is showing false images. This is becoming very problematic. I hired an EMF company they returned and some power quality issue, he was 100% sure and had gray hair, so I believed him. I hired a PQ company and they found some high frequency noise on the ground. I bought a hospital grade

http://www.clary.com/products/instrumentation/s1500-601

double conversion UPS becuase they said it would take forever to find the motor contributing to the noise (also 24x7 facility)

Could a Power Quality event get through the UPS I bought? It is a double conversion unit?
Any other thoughts...

 

[Skogsgurra]

What do the disturbances look like? Do you have a picture?

Streaks? Snow? Distortion? Mirror images?

Did the picture fail in the same way before and after you put the UPS there?

I had the same problem with a unit in a prenatal application. It wasn't hard at all to find the fan with VFD that caused the problem. Used an EMI sniffer and traced the cable.

Other case, HF knife for cutting and stopping bleeding. Just changed the PCC and put an extra ground wire (there was a terminal for that).

Third case, wobbling picture (this was a CRT unit) caused by nearby train starting. Not much to do. Some success with mu-metal screen.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[living2learn]

Thanks!
Supposedly they show the same disturbances but will get photos and upload the before and after uPS disturbances.
EMI sniffer? Do you have an example and how hard would that be to use or do I need to hire somebody?
I thought an online Ups would have solved it.
The hf knife you mentioned changing the pcc, isn't that what a dual conversion Ups does?

 

[Skogsgurra]

The EMI sniffer is on another site and I can't remember the make. There are two of them, one for E-field and one for H-field. Comes in a kit. Itsmoked (Keith Cress) knows what I mean. He has a set, too. Wait for him to chime in.

The HF knife is a surgeon thing that is used to cut tissues with minimal bleeding. It emits rather strong HF energy and is often a source of interference. It has nothing to do with "cutting up" the grid, but that's a nice thought.

If your UPS isn't either a sine-wave output or a very well filtered UPS, you may end up with as much EMI from the supposedly clean grid as you had before. You need to really read the fineprint and also remember that the "reject", i.e. the noise that has been filtered away shall be taken care of in an orderly way and not dumped to your PE. Dumping noise onto the PE is like dumping the kitchen sink onto the floor. Only, you don't see the garbage when it is electrical. But your equipment senses it.

All for now. Wait for Keith.



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Funny, I had the kit in my hand last night as I was rummaging for a 485 sniffer.


Skogsgurra; This is what Skogs is referring to.

http://www.credencetech.com/scanem.html

I think you'd want the CTK010 without the cables.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Good ol' trustworthy Smoked!

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Except it was supposed to be:

living2learn; This is what Skogs is referring to.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[living2learn]

Awesome and thanks for the info - just ordered one.

In the meantime I thought I was ordering a solution that would solve my power quality problems. The ups is Fully Regenerative; True On-Line; Low Distortion Sinewave Output style

http://www.clary.com/products/instrumentation/s1500-601#specifications

but I guess that didn't solve this problem.

skogs - what should you do with all the garbage you filtered out? If you don't want it on your PE (protecive earth?) then where do you want it to go?

 

[Skogsgurra]

THAT is a very good question. The answer is that it usually isn't possible to get rid of it effectively. There are TN-C systems, where PE and N are combined. They are, for obvious reasons (the "where to put the garbage" question) banned in hospitals in Europe.
Instead, so called five-wire systems are used. They separate PE and N and use N instead of PE-N to drain filters. N is allowed to carry current - PE is not, unless there is a fault that needs to be cleared.

That is part of the solution, but keeping PE and N separated is a problem and I have been to hospitals where the local installation firms didn't know how important it is to maintain the five-wire system a five and not a four wire system, which it turns into if you inadvertently connect PE and N somewhere.

It is not an easy situation and you need to keep the system under constant surveillance, take part in buying decisions (to make sure the new equipment doesn't violate the five-wire system), educate the sparkies and inspect every new installation.

There are a few drives and perhaps UPS with what I once coined "intrinsic EMC" and they can be used in hospitals without any extra precautions. Not sure if they are available in the US.



Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

Forgot to mention that the five-wire system also has a name: TN-S, where S stands for Separée which is French for Separated. I do not know how French got into this. But there you are.

For completeness: T (Terre, GND) N (Neutre, N) says how your system is connected to ground at the feeding end and at the consuming end. And C or S says how PE and N are used.

There are also IT systems, where the feeding end is isolated (Isolée) and there is a local ground (Terre) at the consuming end. Used a lot in process industry. And in Norway.

In the US, you can find TT systems. There the feeding end has one ground connection (Terre, again) and the consuming end has its own ground (Terre, of course).

End of crash course.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[living2learn]

Thanks for going the extra mile and breaking it down, I love knowing the background behind todays common terms.
The first test I wanted to perfom at this location was to test the resistance between Nuetral and Ground at the transformer by removing the neutral disconnect link. Unfortunatly the 12kV circuit breaker feeding this transformer is broken and scheduled for replacement in a few months, therefore no test allowed. Do you know of another way to test multiple N-G bond connections without turning off the service (90% of loads are 4w+g)?

Funny story, met an electrician the other day who argued extremely with me that anytime you see the white wire (neutral) you connect the green (earth) to it...this is at a huge site and we have found so far over 30 connections!!

Also have attached the images that show the errors...I am starting to lean towards RF as the cause of problems

 

[Skogsgurra]

Told you! : "Keeping PE and N separated is a problem and I have been to hospitals where the local installation firms didn't know how important it is to maintain the five-wire system a five and not a four wire system, which it turns into if you inadvertently connect PE and N somewhere." Putting white and green isn't only bad practice - it is not allowed in hospitals.

If you have any influence, I think you have a tough job before you. Getting rid of all that isn't easy.

The Chauvin-Arnoux ground resistance tester works well in situations like these.

http://uk.rs-online.com/web/p/earth-ground-resistance-testers/3752574/

It makes it relatively easy to find unwanted connections. But it doesn't eliminate the need to plan and think.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ghostbuster7]

Our group also had image distortion problems with the High Frequency cotterizer that was used in the nearby operating rooms.
As a test we got a slab of meat and a cotterizer and observed the 1 to 1 correspodence on the image distortions, as this test set-up was moved up and down the hallways."Safe" operating distances were established.

 

[living2learn]

Ghostbuster7 - is 85 yards close to a cotterizer? what was your safe distance?

 

[Skogsgurra]

Cotterizer! Yes - that's what I meant with an "HF knife". Thanks.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[living2learn]

Just got word that it is not 85 yards but 30 yards.

 

[Compositepro]

Cauterizer is the correct spelling.

 

[waross]

Could a failing component such as a rectifier be generating the issues internally to your machine??

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

Cauterizer - that makes more sense. Caustic = Burning. Understand now.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[living2learn]

this problem is happening on both the emergency and normal power system on five different machines - showing same issue randomly...