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Thought to post this question hoping someone with experience here can answer. I am going to install TVS suppressors at my transformers and a friend asked if you could install them across your middle and outside rails instead. I didnt think so, but hope any assistance with this could be had from the more experienced on this forum. Thank You

Joe

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Joe---something you might want to take a look at.

I distribute railpower from transformer to rails via plate-jumpered Terminal Strips and mount a TVS on each strip.  The photo below shows an example of a 6 position strip with the HOT (green) and Common(white) conductors* from an 180 watt Powerhouse connected and energizing six screws. Thus, 5 pairs of Hot and Common screw heads are available to connect for soldering wire runs to the rails at diverse points on a single power district.

I also mount TVS at the 12 position Layout Distribution Strip at the Power Center that organizes and distributes to the various power district T-strips. 

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IMG_1784

 

* I remove all plugs from my PowerHouse transformer output conductors and solder on spade lug to accommodate virtually all threaded  connecting points on transformers, TIUs etc.

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Last edited by Dewey Trogdon
Guitarmike posted:

They are pretty cheap, I wonder if it makes sense to put a few of them online?

If a TVS fails, it can fail shorted or open. If it fails shorted, you will know it right away if you have a good breaker! If it fails open, you will not know about it, and you will have no protection. So having several do make sense, because if one fails open, the others are still protecting.

If you are installing them in an engine, then I would recommend two in each engine for the same reason. You will have a backup TVS in case one fails, with the added bonus that your protection travels with you if you take any of your engines to a friend's house for a play date! Also, I like the idea of protection right on each engine because that puts the protection as close as possible to the place where it's needed, in this case the sensitive and expensive boards in your engine. I can't prove that there's an electrical benefit to installing them in an engine vs, at the transformer, cuz like Rob said, they are "electrically equivalent", but my gut tells me that it's better.

George

This is not meant to be disrespectful.

So I have a component - a TVS that inoperation has 2 failure modes, open and shorted.  If it has failed open my on test is with a scope.  If it fails open it provides no protection and in operation I willhave no indiction that it has failed.  If it shorts is caused my breaker to trip.

Do I understand?

TVS components are difficult to test for function.  The test involves a current limited variable voltage to plot the breakdown voltage curve. This can obviously only be done out of the circuit as the voltages required would be very likely to cause more damage than just leaving an open TVS in the circuit.

As for determining if they're open in a circuit with a monitor, there is no effective way to test for that condition.  Obviously, a light bulb in series won't work as in normal operation the TVS is not conducting any current.  The only thing the lightbulb will do is increase the impedance through the part making the TVS less effective.  However, it would indicate a shorted TVS by lighting.

The TVS is not like an MOV that degrades for each spike, they normally have a pretty long life.  Also, the predominant failure mode is shorted, so the chances of having an open TVS aren't that great.

If you're worried about them being open and not protecting the circuit, put a couple in parallel, you are increasing the odds that at least one is intact.

The TVS is not like an MOV that degrades for each spike, they normally have a pretty long life.  Also, the predominant failure mode is shorted, so the chances of having an open TVS aren't that great.

I agree with John.

To add to what John said, if you have inadequate over current protection (breaker) then the TVS will first short, but may open due to excessive current through the TVS. Fast breakers will should prevent a TVS from going open.

I have a copy of an extensive article on surge protection written by Frank Quall’s a member of the DC Highrailers.  In it it he describes testing a number of products that were sold to provide surge protection that did not meet his stringent criteria for protection.

The article also has instructions on how to make a module that would let you know when a spike occurred.

As soon as I get back from vacation I’ll scan it in and e-mail it to any one who is interested.  I’ll also try to scan it in to this forum.

@WaynePa posted:

I have a copy of an extensive article on surge protection written by Frank Quall’s a member of the DC Highrailers.  In it it he describes testing a number of products that were sold to provide surge protection that did not meet his stringent criteria for protection.

The article also has instructions on how to make a module that would let you know when a spike occurred.

As soon as I get back from vacation I’ll scan it in and e-mail it to any one who is interested.  I’ll also try to scan it in to this forum.

Please forward the article to me as well.  Thanks!!

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