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Hi Guys

Two years ago I revived my love of model railroading for the first time since the late 50s when all we had was a circle around the tree.  I'm 63.

I have a modest 8x8 layout running two tracks.  An outer loop and in inner reverse Y.  I've been running strictly conventional with a old refurbished ZW. 

I'm in the process of purchasing a new  (on order)  LionChief PLUS Hudson NYC and an MTH K4s Steam Engine with PS1 from a forum member I've been advised that there a chance of ruining the circuitry on these engines using the ZW, should a short occur.

Would someone please explain, in simple terms, how this would happen?  If a train derails and a short occurs, doesn't all power (juice) stop at the pickups even if the transformer's circuit breaker takes a few seconds to trip? 

A friend suggested that I install a fast-blow fuse between the transformer and track.

Thanks - Ponz

 

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Use breakers, not fuses, sized to the load(current, in amps) on each of A-B-C-D throttles as needed or desired. This will keep the whole transformer from shutting down from a derailment on one track and the other trains will keep running.

Fuses & breakers will not prevent the cumulative damage to modern electronics from voltage spikes that occur during derailmants and running the trains.

For that protection, advise your friend that Transient Voltage Suppression is needed. Here are detailed discussions on this topic.

Last edited by ADCX Rob
Ponz posted:

...

Would someone please explain, in simple terms, how this would happen?  If a train derails and a short occurs, doesn't all power (juice) stop at the pickups even if the transformer's circuit breaker takes a few seconds to trip?  

Correct.  The electrical short itself between the center (hot) rail and the outer-rail means there is 0 Volts between the two rails.  The harmful transients are caused by the rapid change in current when the short initially occurs and even more so when the short is removed by the breaker/fuse. 

I've posted this video before in different OGR threads showing a surge detector in action.  There are 2 red LEDs.  One flashes when there is a positive surge on the track, the other flashes when there is a negative surge.  The screwdriver is simulating shorts.  So while the screwdriver straddles the rails, the voltage between the rails is 0.  No harm to the electronics from 0 Volts.  It's the brief moment in time when entering and exiting the short where transients occur.  All has to do with energy transfer in electromagnetic fields - very tedious math.  

Since there is no electronics-harming voltage transient across the rails during the short itself, it doesn't matter if the breaker responds to the short in 1 sec or 2 sec.  It's a separate discussion about why you'd want a faster vs. slower breaker.

 

stan2004 posted:
Ponz posted:

...

Would someone please explain, in simple terms, how this would happen?  If a train derails and a short occurs, doesn't all power (juice) stop at the pickups even if the transformer's circuit breaker takes a few seconds to trip?  

Correct.  The electrical short itself between the center (hot) rail and the outer-rail means there is 0 Volts between the two rails.  The harmful transients are caused by the rapid change in current when the short initially occurs and even more so when the short is removed by the breaker/fuse. 

I've posted this video before in different OGR threads showing a surge detector in action.  There are 2 red LEDs.  One flashes when there is a positive surge on the track, the other flashes when there is a negative surge.  The screwdriver is simulating shorts.  So while the screwdriver straddles the rails, the voltage between the rails is 0.  No harm to the electronics from 0 Volts.  It's the brief moment in time when entering and exiting the short where transients occur.  All has to do with energy transfer in electromagnetic fields - very tedious math.  

Since there is no electronics-harming voltage transient across the rails during the short itself, it doesn't matter if the breaker responds to the short in 1 sec or 2 sec.  It's a separate discussion about why you'd want a faster vs. slower breaker.

 

Thanks Stan.  That was a great explanation. Now this begs a question. Marty, above, as others have suggested, buying a modern transformer. Even if a modern transformer breaker trips much faster than an old ZW wouldn't there still be a rapid change in current when the short initially occurs, as you stated?

I've attached a couple of transient voltage protectors to the common and positive posts on the transformer. So - wouldn't those and an in-line fast-blow fuse, between power and track suffice?

Also - Modern / smart equipment requires 18 volts to the track and the remotes take over from there.  Why would not an old ZW put out the same 18 volts and serve the same purpose regarding modern circuitry bearing equipment?

I'm not trying to be argumentative.  I'm just  trying to completely understand.

Thank you - Ponz

Last edited by Ponz
Ponz posted:
 
Even if a modern transformer breaker trips much faster than an old ZW wouldn't there still be a rapid change in current when the short initially occurs, as you stated?

As important, these transients are occurring constantly as the trains traverse the tracks. Not as pronounced as during a derailment short, but the TVS diodes will clamp spikes continuously. The damage to electronic components is cumulative, so the more protection the better.

 

The reason for the modern circuit breaker for the old ZW is the fact that the stock breaker may not trip at all, and the unit will just sit there cooking until something fries.  The ZW breaker trips rather slowly, and the ones that I've tested only opened at more than 15 amps after a significant delay.  Also, the ZW breaker keeps recycling automatically, IMO that's a very bad thing!  When I have a short that kills the power, I want to look for it before it keeps getting hammered with shots of power.

stan2004 posted:
Ponz posted:

...

Would someone please explain, in simple terms, how this would happen?  If a train derails and a short occurs, doesn't all power (juice) stop at the pickups even if the transformer's circuit breaker takes a few seconds to trip?  

Correct.  The electrical short itself between the center (hot) rail and the outer-rail means there is 0 Volts between the two rails.  The harmful transients are caused by the rapid change in current when the short initially occurs and even more so when the short is removed by the breaker/fuse. 

I've posted this video before in different OGR threads showing a surge detector in action.  There are 2 red LEDs.  One flashes when there is a positive surge on the track, the other flashes when there is a negative surge.  The screwdriver is simulating shorts.  So while the screwdriver straddles the rails, the voltage between the rails is 0.  No harm to the electronics from 0 Volts.  It's the brief moment in time when entering and exiting the short where transients occur.  All has to do with energy transfer in electromagnetic fields - very tedious math.  

Since there is no electronics-harming voltage transient across the rails during the short itself, it doesn't matter if the breaker responds to the short in 1 sec or 2 sec.  It's a separate discussion about why you'd want a faster vs. slower breaker.

 

Stan - Another thought if I may.

Let's say I'm running a LionChief PLUS on one ZW channel and an MTH PS1 on another channel with an in-line fast blow 6amp fuse.  If the LionChief PLUS shorts out, how if at all, would that affect the more susceptible MTH PS1 engine's (circuitry) since it's running on a different channel? 

Anyone - please feel free to chime in.  I appreciate all the feedback I can get.

Thanks - Ponz

Ponz posted:
 
Let's say I'm running a LionChief PLUS on one ZW channel and an MTH PS1 on another channel with an in-line fast blow 6amp fuse.  If the LionChief PLUS shorts out, how if at all, would that affect the more susceptible MTH PS1 engine's (circuitry) since it's running on a different channel? 

There is only one "channel" on your postwar ZW.

There are 4 variable taps on that one channel(transformer secondary), so all trains are running off of the same source.

Last edited by ADCX Rob

Ponz, I was in your shoes not long ago with respect to transformers. I've been around toy trains all my life and up until recently, thought the Lionel ZW was the be-all-end-all of transformers. I own 5 of them, all completely reconditioned and ready for use--but they will only be used on my layout to power lights, switch machines etc. I finally took Marty's advice and bought a modern transformer, a brand-new MTH Z4000. At around $400.00, it  was money well-spent. You get state-of-the-art protection, and best of all, I think the trains run better. I run both modern and prewar trains in both command and conventional modes, and the operation is much smoother with all my trains--even the old ones. If I were you, I'd go for a modern transformer. Just my $.02. 

John

Last edited by BlueComet400

Since 2005 I've used primarily AF 30B transformers (S gauge layout), a spike protector by Scott's Odds 'n Ends (no longer available, but still working great) and 7A fast-blow fuses -- one per block and every siding.   Together they have provided and continue to offer solid protection.  However, if I were to do it over today I'd use PSX-AC units by DCC Specialities.   We have them on our club layout and they are fantastic.  Definitely very fast-acting (critical attribute) and resettable.  

PS  Their RRampmeter is also very good, especially if you run DCC, which I do in addition to Legacy and conventional. 

Chuck K posted:

I too use a post war Lionel transformer and at times with modern electronic engines on one of my loops. I just added a Dallee circuit breaker between the transformer and the track. They are inexpensive, simple and have a re-set button.

https://www.dallee.com/Model-T...ircuit-Breakers.html

 

I disagree, in my view they are actually very expensive.

You can get TVS diodes at DigiKey for $0.68 per diode and their shipping is very reasonable.

DigiKey also has the same Potter & Brumfeld circuit breakers used in the item that Chuck K links to:

You can find these parts at other suppliers, I just happen to use DigiKey because their prices are competitive and their shipping rates are low.

Ponz, if your PW transformer is in good shape physically, in good working order, you protect it with properly rated thermal breakers, and you protect your engine's circuit boards with TVS diodes, you should be fine, and you won't be wasting money.

If you must have the PCB with the terminal strip, a PCB from OSH Park would be around $1/ea, maybe less.  I buy the Euro-style terminal blocks in bulk on eBay for peanuts, and as you say, the 1500W TVS is around 50 cents for 25 or more, always useful to have these around.

Also, with a little searching, you can have even cheaper breakers.

5A P&B Panel Mount CB, $2.47

These also come in 8A and 10A, also below $3/ea.

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