Transient Voltage Protection---Is It Necessary?

[MickeyDemian]

Hello:

  I'm asking for opinions and instructions on Transient Voltage protection when running modern Lionel Locos (sounds crewtalk etc., fan driven smoke unit) with a PW transformer (ZW).  The ZW has an upgraded breaker/diode, but do I need to place a Transient Voltage suppresor in the circuit?  Does one place this in the loco itself or just on the power circuit to the middle rail?  I'd appreciate any help and opinions so I don't ruin an engine.

Thanks--Mickey

[rtraincollector]

First I'm no expert but from what I understand the Breaker in the transformer is for the transformer not the trains. So yes is the answer to your question. Now where to put it. I have heard both , I have also heard some say you should have it in your locomotive. And some say at the terminal is fine. I guess it all depends. now will say this if you do it in your locomotive I guess that means you need it in each one. 

[cwburfle]

1 - When using a Postwar Lionel transformer with modern era trains containing electronics, TVS devices are recommended. The devices should be placed as close to the train boards as possible. So putting the TVS across the lock-on terminals is better than placing it across the transformer terminals. Putting one inside each locomotive would be even better, but I don't think many people go that route.

2 - Regardless of whether the internal ZW circuit breaker has been replaced / upgraded, it is a good idea to add external circuit breakers for two reasons:

Due to the internal wiring of postwar ZW transformers, it is very easy to accidentally create a circuit that is not protected by the breaker, and when those circuits are created, often they will have a short condition.

The trip characteristics of the internal breaker is there to protect the transformer. The original breaker does not trip until there are a lot of amps flowing for a rather long time. An upgraded breaker may trip faster, but it will still require a lot of amps.

So what to do? ....... put an external breaker on each power terminal "A", "B", "C", and "D".

I use Postwar Lionel adjustable electromagnetic #91 breakers. They trip instantly.
Warning: it is possible to overtighten the adjusting knob and effectively disable the breaker.
 (Just don't do that)

[lionelsoni]

Consider putting TVSs both on the track supply and in the locomotives.  That way, any friend's equipment running on your layout is protected; and your locomotives  are safe running on anyone else's layout.  There is no reason not to have multiple TVSs on the same circuit.

There is no harm in using fast-acting circuit breakers or fuses; but (slower) thermal circuit breakers avoid nuisance tripping from harmless brief overcurrents.

[sir james I]

I have GG track so I put the TVS(s) across a Marx lockon(s). Those and fuses inline with the center rail is about as good as I can do.

S.J.

[phillyreading]

I would highly recommend putting the TVS unit across the transformer's two output wires at the output area. One goes across the positive terminal and the other goes across the negative terminal, looks like you might short out something but no it won't short out as that is the correct way to hook up a TVS unit. Also make sure you have a TVS unit that is bi-directional(must be bi-directional or don't buy it) and at least 32 volt rating.

I am using a post war 275 watt ZW with added in 7 amp quick blow breakers and a 32 volt bi-directional TVS unit. I use this transformer for my older Lionel engines. 

Lee Fritz

[MickeyDemian]

phillyreading

I would highly recommend putting the TVS unit across the transformer's two output wires at the output area. One goes across the positive terminal and the other goes across the negative terminal, looks like you might short out something but no it won't short out as that is the correct way to hook up a TVS unit. Also make sure you have a TVS unit that is bi-directional(must be bi-directional or don't buy it) and at least 32 volt rating.

I am using a post war 275 watt ZW with added in 7 amp quick blow breakers and a 32 volt bi-directional TVS unit. I use this transformer for my older Lionel engines. 

Lee Fritz

 Lee:

 Thank you for the input.  Where can one purchase a 7 amp quick blow fuse and the 32 volt bi-directional TVS unit.

 

thanks again--Mickey

[lionelsoni]

Here is a link:

http://www.mouser.com/Circuit-Protection/TVS-Diodes-Transient-Voltage-Suppressors/_/N-5g3gZscv7?P=1yzv44x&Keyword=1.5KE36CA&FS=True

The "1.5" is the peak power rating in kilowatts.  The "36" is the nominal peak voltage.  The "CA" means "bidirectional".  "A" alone means unidirectional; but you don't want that.  There are three voltage ratings to consider:

Operating voltage--30.8 volts.  This should be no less than the RMS voltage times the square-root of 2, which is 29.7 for 21 volts RMS (ZW).

Breakdown voltage--34.2 volts.  This is the voltage at which the TVS will begin to conduct.

Peak voltage--49.9 volts.  This is the voltage to which the TVS will limit the circuit.

I recommend auto-resetting automotive thermal circuit breakers instead of fuses or magnetic circuit breakers.

[cwburfle]

I recommend auto-resetting automotive thermal circuit breakers instead of fuses or magnetic circuit breakers.

I prefer manual reset. I prefer to clear the problem before restoring power.

And I'll take the instant trip of an electromagnetic breaker over the delayed response of a thermal breaker.
I like to address any problems that cause my electromagnetic breaker to trip, as opposed to ignoring a problem that is masked by a delayed response.

 

[lionelsoni]

There's nothing wrong with that; I just recommend the alternative.  A switch machine throwing, an accessory operating, or a heavy train starting up may trip a fast overcurrent device without there being any problem.

[KRM]

Mickey, I have both the TVS that and re-setting breakers at a lower AMP rate. Here are some of what I am doing and what you can do.

TVS on the ZW,

 

Re-set breakers behind the ZW.

TVS on the lockon

 

 Just some ideas.

 

 

[EIS2]

Jim Barrett made an excellent video for constructing a fast acting circuit breaker box.  I don't recall if he installed the tvs diodes, but I made the box using his instructions and I did install tvs diodes across all of the circuits.  The only thing I changed was the circuit breaker rating.  I used a lower amp rating than he suggested.  The video can be found here:

https://vimeo.com/ondemand/breakerbox

Earl