Transcient filters 2

[Nehemiah]

When troubleshooting equipment, we frequently have to shut off the power to remove cables and check wiring problems. Frequently, when we re-energize the panels, the transcients are damaging our power supplies.

Could someone please provide me with information as to where to purchase 480VAC, 3-phase, up to 60 amp trasncient supressors that would work in a situation like this?

 

[busbar]

Gizmos like these look pretty cool

http://www.geindustrial.com/products/brochures/9l10m.pdf

They permit a handy, true-Kelvin connection, where most [all?] others do not. This makes connecting-lead impedance/inductance effectively zero, which seems a bit unique.

 

[Nehemiah]

Thanks, those look good.

We just found out the damage is around $10k for new power supplies from one incident alone.

 

[peebee]

There's LOTS of companies selling TVSS (transient voltage surge suppressors).

The major electric suppliers (GE, Cutler Hammer, Square D, Siemens) all sell them. So do data center type companies, such as Liebert. There's other companies that specialize in TVSS, such as Current Technologies.

In the words of my boss, TVSS is voodoo science. They all have some tests to prove their stuff is better than anyone else's. Call any of them, and they'll fall all over themselves trying to get you to buy their product.

Note that if this is a grounded system, you need a wye-connected TVSS, with an additional TVSS module between neutral and ground.

Surge arrestors, which are different but similar, and which protect more against things like lightning hitting a utility line, can also be a good idea.

Multi-level TVSS, whereby you protect your main panel, downstream panels, and then provide TVSS power strips at your computers, etc., might also be a good idea.

 

[Nehemiah]

Thank you peebee. Any recommendations that you could make about the companies? The equipement that we are damaging is used to generate a 300Vdc, nothing too difficult. But when trouble shooting this, we have to drop power because the power supplies do not have an off switch.

 

[jbartos]

Suggestion: Visit

http://www.thomasregister.com

and type Suppressors: Transient Voltage Surge under Product or Service, which will return 20 companies to look for TVSS.
Alternately, type Suppressors: Voltage Surge under Product or Service, which will return 26 companies to check for TVSS

 

[peebee]

Re: "Any recommendations that you could make about the companies?"

No, sorry. As I mentioned, the manufacturers all have some documentation of some laboratory tests which "prove" that theirs work better than all others. Field experience is not much help either, as transients are so variable from site to site; it's often hard to tell if you had a good or bad TVSS or if you had a good or bad utility source.

At least one manufacturer heavily promotes individual fusing of each MOV or whatever technology is being used (usually, the protection on each phase is made up of several MOV's in parallel). That makes a LOT of sense, to me anyway. I'd say look for individual fusing.

Metal Oxide Varistors (MOV's) and Silicon Avalanche Diodes (SAD's) are the two most common technologies used. They each have advantages and disadvantages. Some manufacturer's include both -- hey, the more the merrier, if you ask me. At least no-one can say you went for the cheap one that way.

There's various conflicting UL, IEEE, NEMA, and IEC standards. They all seem to measure completely different parameters. Pick the one you like best.

Leviton publishes an "Applications Manual and Reference Guide for Surge Protection and Line Conditioning Products," available in PDF format here:

http://www.leviton.com/pdfs/fullcats/ApplicationRef.pdf

This is not a recommendation for Leviton, and for all I know this is a completely biased publication (although it seems OK to me). At least it gives you some more detail on some of the considerations I oulined above, and seems to be reasonably logical. They have some other information available here:

http://leviton.com/sections/prodinfo/newprod/npleadin.htm

Keep in mind that for any TVSS, it's critical to keep the lead lengths as short as possible. That means to get something mounted integral to the equipment if possible. That usually means a TVSS by the same manufacturer. (Next best to integral is to mount the TVSS to the enclosure externally).

My standard is to allow any major mfgr to include their own TVSS with their equipment. Beyond that, I'll accept any well-known TVSS manufacturer. My idea of "well-known TVSS manufacturer" is probably different from the next guys, so I won't even bother listing them here.

As I mentioned, this is voodoo science. It's only a little more scientific than specifying a voodoo doll. You find a voodoo doll you like, buy it. If it works out for you, go back to the same witch docter next time. If not, well, then try a different witch docter. Same thing with TVSS's. Don't worry yourself TOO much about finding the right witch docter or TVSS manufacturer on the first try. Just talk too as many friends as possible about their experiences first (actually, this is about the same way I select my medical docter too).

Hope this helps. Good luck.

 

[peebee]

By the way, here's some sample TVSS specs from actual users:

City of Santa Monica (includes a big list of vendors):

http://www.santa-monica.org/engineering/intranet/masterspec/generic_templates/full/16/16289fl_.doc

NASA:

http://si.ksc.nasa.gov/specsintact/masters/NASA masters/NASA/pdf/16288.pdf

Chicago Public Schools:

http://intranet.cps.k12.il.us/Technology/12/16680Transient_Voltage_Surge_Supression.pdf

Texas Tech. University:

http://www.physicalplant.ttu.edu/engr/standards/eng16289.htm

State of Wisconsin:

http://www.doa.state.wi.us/dfd/documents/16412.doc

Stanford University (buried in a panelboard spec):

http://facilities.stanford.edu/fdcs/docs/16442.pdf

And here's some from some vendors:

Intermatic:

http://www.intermatic.com/comind/guides/guidespecs/UG40 Modular Series.rtf

ITVSS:

http://www.itvss.com/pdf/Protector-Guideform-LowExp.doc

Call Square-D or Cutler-Hammer, they'll email you a guide spec in Word format.

 

[peebee]

Here's some more thoughts:

I did not mean to imply that "TVSS = voodoo doll." A TVSS would work much better than a voodoo doll in your application, and would likely be money well spent.

Make sure you have a solid neutral-ground bond at your main panel or switchboard in accordance with the typcial NEC requirements for any service-entrance panel. A bad N-G bond is the #1 cause of premature TVSS failure (the N-G TVSS module will tries to make up for the bad connection, and it's just not designed to handle the constant current flow).

I forgot to include "selenium" with the MOV's and SAD's. Depending on who you talk to, selenium is either critical or completely optional in TVSS design. Just make sure your spec is liberally sprinkled with TLA's (three-letter acronyms).

Now you have as much reference material at hand on TVSS's as 99% of the professionals out there specifying TVSS's. And it would be difficult or impossible to correctly identify the other 1%, so don't worry too much about finding them.

 

[Nehemiah]

Thank you very much for all the help. We are now looking at different manufactures.

Actually locating the TVSS in the enclosure will not be a problem. We are using large enlcosures (7 feet by 10 feet is typical) for all of our control cabinets.

Thanks again.