need some help on protecting newer engines

Preface: based on real world experience since 2018

If all you are running is Lionchief, the primary risk is current (Amps) due to the typically thin wiring used in these. I'm not doubting that Lionchief cost you a fair bit of money each. The flipside is, this also isn't your father's Lionel from the 50s, and the general plastic construction and low cost methods of thinner wiring and thin metal to the pickup rollers, just every aspect of these engines is cost cutting measures when you compare to even engine built 10 years ago.

Again, by far, doing many, many, many repairs for the local shop, train club members, and the local community, the typical failure in this class of engine (Lionchief and typical starter set cars) is the thin wiring burning up when a derailment short happens. This happens because one truck is on the track, the other truck derails and is crossed up and the wheels touching the center rail or the pickup roller is now resting and touching the outer rail. This creates a short from one truck to the other across this wiring inside the engine. Again, the risk is more to the wiring and the pickup system melting plastic in the process- than the control board being at risk. Again, because this is mostly a wiring and pickup problem, it never even makes it to the board to damage it.

Second part is, that due to the use of electronics and can motors without a lot of inductance like the older motors and accessories, there are far less and less severe voltage spikes generated when compared side by side to Postwar. Again, I'm not saying it's not possible to damage or wipe out a Lionchief board from a voltage spike, but the shear numbers just to not bear out failures from voltage spikes in the same way we see on other control system boards.

Bottom line:

Fuses and/or circuit breakers protect against over current that happens from shorts and overloads. Again, this is just the raw power Voltage times Amperage that happens when a derailment or other short/overload occurs. The original DC lionchief adapters have relatively low current limits of around 36 Watts or less and relatively sensitive and fast circuit protection. The Z1000 bricks use slower thermal breakers, and the CW80s also have current sensing and a fuse as a last resort- but again, given the difference of what came with the set- vs what you get with these larger transformers- adding faster acting and lower current limit fuses or breakers would add a layer of safety.

Current limiters (fuses or breakers) go in series between the source and the track.

Transient Voltage Suppressors (TVS) protect against voltage spikes (spurious high voltage generated when current changes in an inductive or even capacitive circuit). These spikes (easily over 100V and maybe 400-600V) tend to break down the electronic components rated at typically around 35V maximum DC.  The whole point of the TVS is that it shorts out voltage higher than the rating, but appears mostly open circuit below that voltage.

TVS goes in parallel across the input to the track or the device you are trying to protect.

Vernon's post is pretty comprehensive and explains the situation. It boils down to

1)Having a fast blow breaker or fuse between the transformer hot output and the track. The circuit breaker even in modern transformers like the cw80 and z1000 may not trip fast enough. If you do a search on here there are a lot of threads on this, about which circuit breakers to buy or using things like fast blo auto fuses. I would recommend using a low a rated device in terms of current (for example, try 7 amp let's say, rather than 10), but that is just me.

2)The TVS as mentioned stops voltage spikes (it is a type of voltage clamp). Especially if you have a short, you can get a spike in voltage and that can seriously fry circuit boards/components. They are a kind of diode. You can install it across the neutral on the transformer (generally U) and any of the power output terminal(s) you use for track power. Some people put it between the center rail and ground/neutral at the track end for any drops they have, while that will work to me it is overkill (if you only have a couple of lockons on a small layout, though, you can put it across them pretty easily.

One other thing, if for some reason you ever open up an engine or let's say a tender on a steam engine or an operating accessory with a circuit board, be very careful if you go to handle the boards. Make sure to ground yourself to something that is grounded like a cold water pipe, whatever, people who work with boards often have a ground strap on their wrist to diffuse any static charge. Static zaps can do a number on boards/chips (CMOS just loved static, I can tell you!).

Also, just some additional notes. At home and at the local store, the test/demo track is powered with a Z500 brick and Z controller, not the higher power Z1000. In both cases, I'm not using additional breakers even though the Z500 brick breaker is slow acting i generally cannot push enough short circuit current to cause serious damage. Conversely, I have seen a customer use a Z1000 set, and definitely smoke a derailed caboose or car before the breaker tripped.

Z controllers also do have an internal TVS diode across the MOSFETs to protect them, now how much this protects anything else could be debated. They do not have current limiting internally and depend on the power source (the brick).

Older CW80s, I not aware of any TVS protection, and the current limiting of both new and the old CW80s trips after a short period of over current sensed. I've seen damaged cars and equipment also from a customer running a CW80. Not severe damage, but definitely some evidence of wires being pushed to the limits current wise.

All I'm trying to say is, you are on a fine line with what you are running and your power sources. They are sized to limit current and thus power, and will typically not vaporize some wiring in the same way an unprotected postwar ZW transformer can. Protection is always a good thing and money well spent in the long term. One of the harder things to justify is spending money when there is no obvious benefit - example the lack of blowing up board, damaging wiring, melting things. I'm just saying, that trying to get folks to understand you spend the money on safety- in hopes you don't have to spend many times more on repairs and replacements.

Good Magnetic Hydraulic fast acting breakers like the Airpax models that many suggest are a little harder to find and also finding the right current rating.

TVS diodes are relatively cheap by comparison and very easy to get from multiple sources.

Tons of related topics

https://ogrforum.com/topic/77875232681100885

https://ogrforum.com/...7#149098340133171337

Also, again more related topics and a usage note on the airpax with the Z1000

https://ogrforum.com/...and-z1000-controller

Airpax breakers discussion https://ogrforum.com/...-internal-mechanisms

Good TVS discussion with specific info and even further links and discussion- suggest you read this one all the way through

https://ogrforum.com/...rder-20-from-digikey

Both of these are pretty cheap insurance. With breakers, you might need a couple of them, depending on how you wire, but they aren't prohibitively expensive (I can't speak to ones like the airpax these days). If a fast blow breaker is too expensive, a fast blow fuse would work just as well, like auto fuses, and they are cheap. TVS are like 15c, and while they do wear out, are easy to replace and use.

And compared to expensive or non existent boards, not to mention the hassle of having to replace them, it is a lot cheaper IMO to have the right protection.

As per those discussions (of which I was a part), the Airpax breakers and the Z1000 do not play well together.  A 4A Fast Blow Fuse in an automotive fuse holder works much better.

John

If this question has been asked and answered before, I apologize: I am always aware of the effect anything we do has on the DCS signal. Therefore, knowing that TVS diodes can degrade the signal if overused, is there any effect on DCS signal of circuit breakers/fuses in line between the TIU and track distribution blocks?

@LT1Poncho posted:

If this question has been asked and answered before, I apologize: I am always aware of the effect anything we do has on the DCS signal. Therefore, knowing that TVS diodes can degrade the signal if overused, is there any effect on DCS signal of circuit breakers/fuses in line between the TIU and track distribution blocks?

My recommendation is- put your fuse or breaker on the input to the TIU, not the output. The "why" is the TIU is an electronic device or load, and specifically, each output having a TVS inside the TIU that can fail can short. In addition, this puts the breaker or device on the choke side of the power and DCS signal.

Current protection placement= nearest the source- transformer

Voltage protection (TVS) nearest the electronic device you are protecting.

example diagram originally by @CAPPilot and edited by me a few times.

I believe this one was an original diagram I used to edit and create. Key points in this one, the 22uH chokes are redundant and not needed- the TIU input channels already have chokes for this purpose. This diagram has a lot of "extra" TVS diodes that could lead to DCS signal loss. This is an example of overkill or too much of a good thing IMO. But it does show, something like a PSX-AC brand of electronic breaker has to be before the input of the TIU. If put on the output, a PSX-AC can degrade the DCS signal.

Thank you Vernon, makes sense and well explained.

@LT1Poncho posted:

If this question has been asked and answered before, I apologize: I am always aware of the effect anything we do has on the DCS signal. Therefore, knowing that TVS diodes can degrade the signal if overused, is there any effect on DCS signal of circuit breakers/fuses in line between the TIU and track distribution blocks?

The best way I describe the why and the chokes from above (inductors). When the TIU adds the DCS signal onto the power, that signal wants to go in both directions- to the track via the output and back towards the transformer on the input. Being a high frequency digital signal compared to the 60Hz AC power, a choke in series is high impedance (complex resistance) to that DCS digital signal so that the transformer doesn't "short out" the DCS signal. A choke passes lower frequency or DC, but chokes off (high impedance) to a higher frequency digital signal.

So, you are putting a breaker, that has some unknown effects, but if before the input, then it's "behind" the choke compared to the DCS signal generator.

THANK YOU ALL FOR THE REPLIES ORDERING THE TVS DIODES. NOW TO FIND FAST ACTING RESETABLE BREAKER FOR IN LINE