my dad recently found a ZW 275 transformer for my layout and I was told I need to add a 5 amp fuse or a circuit breaker somewhere to protect modern locomotives, can anyone shed some more light on this? I run both postwar Lionel, modern Lionel and MTH trains.
Congrats on the zw find. There are things that you definitely need to do, but I believe that you have been totally mis-advised thus far.
I hope "lionelsoni" will address this question. Meanwhile, try searching the archives for this site, looking especially for posts authored by lionelsoni with the keywords TVS, fuse, etc.
In one sentence, no fuse or circuit-
breaker will protect sensitive electronics in modern locomotives or other running gear or table-top items. Fuses/circuit breakers, properly sized, will protect transformers and associated wiring, but NOT electronics. TVS technology, i.e. its application to toy trains is incredibly simple but for reasons beyond my ken seems to be resisted by far too many "experts."
If you are certain that your new ZW has a circuit-breaker that is working (not a given, by any means) you may run postwar and non-electronic stuff but wait until you understand TVS before using it with them.
External fuses or circuit breakers will protect your transformer and wiring, not your locomotives. To protect electronics-heavy modern locomotives, use a transient-voltage suppressor (TVS) for each ZW output. Connect it between the U and whichever of the A, B, C, or D terminals is powering the track. I recommend the 1.5KE36CA, which you can get from Mouser and other electronics distributers.
The ZW is not protected from connections among the A, B, C, and D terminals. You can use external circuit breakers on the individual outputs to correct this. If you use 5-ampere circuit breakers, you may wire your layout with wire as small as 20 AWG. With 10-ampere breakers, use wire no smaller than 16 AWG. With 15-ampere breakers (which is the rating of the ZW's inadequate internal breaker), 14 AWG. Automatically resetting automotive-type breakers are the most convenient. They allow brief overloads, which are not harmful to the wiring or transformer.
Bob Nelson
Here is a link. I have them at almost all of my LockOns
http://www.mouser.com/ProductDetail/Littelfuse/15KE36CA/?qs=sGAEpiMZZMsYiK5PgaDog38p0a8Da%252bhYSQsfo594C0A%3d
Joined 1-21-2011 TCA 13-68614
Kev, From The North Bluff Above Marseilles IL.
i am not very good with this stuff so can anyone post a picture of where these TVS are connected on the transformer and track, that would help me and my dad.
There are pics available, but I can't take the time to find one this morning. Basic hook-up is simplicity itself, however. You wire a TVS diode ACROSS the output terminals of your transformer; that is, between Red and Black, or hot and ground, or whatever you choose to call it.
In practice, on a postwar ZW this means you simply hook it up between posts U and A, assuming you are using them as the throttle to power to the track. You can also hook them up across the terminals of a lock-on device, or between the middle rail and an outside rail of your track, etc. If you did this with a piece of ordinary wire, you'd create a short-circuit; but TVS diodes are not ordinary conductors, they are devices. At ordinary track voltages they are "invisible" to the current and only "react" when they detect a voltage spike, which they squelch.
The basic principle is that in toy trains of the Lionel type, you must account for two potential problems, or else bad things could happen:
1. Current that is too high (short circuits)
2. Voltage that is too high. (spikes)
Two totally different problems requiring two different solutions:
The over-currents are dealt with by circuit-breakers or fuses. Voltage spikes are dealt with by TVS diodes.
With pre-and post-war equipment, voltage spikes were no problem. The circuit-breakers in the ZW transformers were very slow acting, typically 11 to 40 seconds according to my principal source.
Modern locomotives and other table-top gear typically contain electronic circuits which are pretty rugged with respect to current but very vulnerable to voltage spikes.
If you are only going to run pre-and post-war equipment on your layout, you don't really need protection against voltage spikes, but with modern electronic equipment you need BOTH.
"Fast-acting" fuses or circuit breakers are a pain-in-the-butt. They react too fast, limiting the current well before theire is any real dangerous problem, but are nowhere near fast enough to "clamp" voltage spikes.
If I cite him correctly, lionelsoni suggests putting a TVS diode as close as possible to the item you want to protect. In the case of modern locomotives this mean inside the case. In a loco, this would mean between the wire from the pick-up rollers and the "ground," generally the chassis. This has the added advantage of protecting your loco if you should run it on a friend's layout, which may not have TVS protection.
TVS diodes are considered rugged, but their one weakness, as I see it, is that they are hard to test. So I use several on my layout (they are so absurdly inexpensive you can buy 'em by the bag) and scatter them around. They do absolutely nothing until needed.
Consider them to be akin to the protective device into which most of us protect our computers and other expensive electronics. The normal 15-amp fuses or circuit breakers in your household breaker-box protect against too much current; but many of us also use "surge protectors" to "clamp" voltage spikes in the AC circuitry. Your trains need similar protection between the transformer outputs and the trains. Note: some modern train electronics devices already incorporate both current and voltage protection, but we are talking here about a post-war ZW which AT BEST only has high-current protection -- and you ought to check (or have checked) the operation of the circuit breaker, AC power wire, etc. The 5-amp fuse or breaker that your dealer mentioned would certainly limit over-currents, but why restrict a ZW to a mere 5-amps when it was designed for 15? Some folks use an external 10-amp fuse or breaker for ultra-safety.
Hope this helps you or someone.
I understand that the bast place is inside each modern engine as stated already. I have mine on the lockOns
For lockOn use You can solder it to the LockOn
I'm gad someone brought this up. I have soldered feeders every so many feet, do I just solder these TVS where the feeders are from the center rail to the ground rail? Do I have to re-solder my feeders with the TVS or can they be spread out and soldered to the track independently around the loop? Hope that makes sense?
Across the transformer outputs (e.g., U to A, U to D, etc.) across the lock-on terminals, across the center and outside rails, these are all electrically equal, are they not? Scatter them around the layout anywhere that is convenient. You don't even have to solder them if you can make a good tight mechanical connection, such as with screw-down transformer output posts. (In other places I generally solder them, and replace them now and then.)
Inside an electronic engine, tender or accessory is also good and has been discussed in this thread.
I come from the area where there used to be Little Tavern mini-burger joints. Their slogan was "Buy 'em by the bag." That's my advice with TVS diodes too. Buy several and hook em up. One might be bad. Hard to tell.
By the way. The various train forums are filled with complaints that "my electronic locomotive (or component) worked fine when I put it into storage last January, but when I tried it this year it was dead." Does anyone know of a case where this seemingly inexplicable event has happened to an item that was protected with an (internal) TVS?
BF,
I appreciate the reply I just want to be certain. When you talk about across the transformer, can I solder two "connectors" onto the ends and attatch to post A,B,C and D and the other end to the commons on a ZW? Also I should pick convenient locations throughout the loop and solder one end to the center and one to the ground rail? By what your saying you cant have too many? I'm not concerned with inside the locomotives so much because my trains don't travel anywhere for now, just want the layout up to snuff. Lastly why don't the "experts" push this? Sounds important.
I absolutely would not do it! Connecting posts A, B, C, D to each other in any combination with anything is so fraught with the potential for disaster I wouldn't do it on a double-dog-dare.
You can't have too many TVS diodes but you can waste too much money, although the principal cost to obtain several TVS diodes is the shipping charge.
I generally have one each on throttle AU and DU, and I'd put them on BU and CU if I had any electronic devices on my table-top. Then I put one on the primary lock-on and perhaps another one or two across the inputs of any electronic accessory; but I run mostly postwar and only have a few electronic devices. I keep a few spares handy because typically they don't fail "catastrophically" so it's hard to know for certain whether one is still good. That's why I set up multiple units with easy swap-out capability. (You may have noticed that some 115 volt surge suppressors for TV and computer use have an indicator light that is supposed to show when the device has sacrificed itself.)
Please understand that I am not an "expert". Bob "lionelsoni" Nelson is, and there are a few others on the forum. I just beat the drum occasionally.
The "experts in stores are frequently better described as "clerks," and a lot of the old pre- and post-war geezers like me don't seem to understand that electronic equipment needs additional protection over the earlier non-electronic devices. I'll wager that you never felt the need to plug an old 1950's Emerson fan into a surge-supressor; but your computer, TV and stereo system are different birds altogether.
Also a lot of folks seem to fail to understand how harmful voltage spikes can be, or the magnitude of such events. Consider how many times you have walked across a carpet, usually in the dry air of winter, and zapped yourself when you touched a doorknob. In the dark, you may even have seen the spark. The current is relatively small, but the voltage could be in the hundreds of thousands. Sorting certain fabrics just out of the dryer can produce the same effect. We aren't talking about 1.5 to 9 volt battery voltage.
Many people still believe that commonly-available high-speed fuses are helpful in this area. As a rule they are not. Certainly a high-speed instrument fuse is faster that the old thermal circuit breaker on a post-war ZW, for example. But that circuit breaker, whose response-time was measured in seconds, was designed to protect the transformer and associated wiring from high current, not voltage spikes which essentially occur at the speed of light. One-tenth of a second, for example, is not fast; indeed it is an eternity in electronic terms.
Finally, a lot of modern manufacturers do incorporate voltage-spike protection into their devices, but the main concern here is powering modern electronic devices with older-generation purely electrical ones.
Post Script: the person who advised the initiator of this thread to fuse his post-war ZW at 5 amps may have been taking into account the proposed use of relatively thin wires. For safe current-handling, the transformer-to-track wiring must be able to carry safely the maximum current that the transformer can put out. Otherwise the wires can heat up, the insulation melt, and the whole house go up in flames. (So the advice was not necessarily all bad -- it simply was not useful on the subject of voltage-spike protection.) Again, Bob "lionelsoni" Nelson has written extensively on the subject of wire-size too. (Evidently size matters.)
Happy and safe New Year, everybody.
bfskinner I wouldn't do it! Connecting or jumping posts A, B, C, D with anything is so fraught with the potential for disaster I wouldn't do it with anything. You can't have too many but you can waste too much money, although the principal cost to obtain several TVS diodes is the shipping.
I wouldn't do it! Connecting or jumping posts A, B, C, D with anything is so fraught with the potential for disaster I wouldn't do it with anything. You can't have too many but you can waste too much money, although the principal cost to obtain several TVS diodes is the shipping.
Thanks again for all the info, greatly appreciated. Forgive me I think I misled you in my post. My understanding was to take a TVS diode and connect it to the A with one end and the other to the U on the ZW and so on with B,C, and D, four total on the back of the transformer? If I'm correct in that method, can I take a single TVS and solder two insulated connectors on each end so I can just slip it over the post and tighten the main bus wire or whatever I have going to the corresponding post on top of the connector?
I too have mostly postwar but darn it, I cant help myself sometimes with all the bells and whistles of the newer, modern stuff. I just wanted to stay simple but read alot on here and freak myself out with all the tech stuff and want to do it right while learning as much as possible. I'm using 14 guage wire for the main loop and 16 for the switches, so I think I'm ok there. Unfortunately like I said the new stuff pulls me in and I want to protect it since I am using an older power supply. Again thanks for taking the time to respond.
Happy New Year!
Silentman,
Although I am not hungover this morning, I still can't visualize exactly what you are proposing. Also, I have a tendency to edit my drivel and notice that your quotation cites an early version of my last post.
That said, let me just note that the postwar ZW is roughly the equivalent of a modest arc-welder. [As I understand it, when Lionel sought to re-introduce the Postwar ZW back around 1990 they couldn't get approval from UL (or somebody important like that) to offer it as a "toy" transformer. So they had to go back to the drawing board and produce the modern two-piece electronic ZW and all the other electronic stuff.]
It is in this context that I recommend using extreme caution when using, repairing or modifying any post-war ZW.
My approach to TVS diodes, to try to protect my very few modern locos/tenders, was to begin by putting a TVS diode between AU, BU, CU and DU, for a total of four. I didn't solder them or modify them in any way except for actually shortening the leads on the diodes, bending them around each output posts, and tightening the knurled-nuts down snugly. Later I added a couple of more around the layout, and have similarly employed them with a KW, 1033, 1044 and other transformers for my layout and that of my granddaughter. To date, I have not installed them inside any modern locomotive or tender, etc., mostly because I am older than dirt and don't see too well.
So far, I have not "blown" any modern electronic equipment associated with my toy trains and I can safely assert that no tigers are roaming my back yard either!
Beyond that I cannot and will not opine.
Yes you can do it like this also. From what I have heard ( I think it was from Bob Nelson ) the closer it is to the engine's electronics the better. so this would be as far away as you could get and the least effective in protection. I use mine at the LockOns
Perfect! I think I will just request pictures instead. Thanks again all!
I put a TVS in each locomotive as I have occasion to open them up for other work. I also have them across the track feeds.
Do the TVS need to be applied in a certain direction? (Ie pointed toward a certain leg of the transformer like a diode?)
For this AC application, you use bi-directional TVSs. No polarity.
Rob
Great thread. I have a question. The TVS recommended (1.5KE36CA) appears to have an operating voltage of 30.8V and peek current of 30.5A.
Why would you not go with a lower voltage TVS such as the 576-SA18CA with a operating voltage of 18V and 17.5A given that our ZWs are 18V?
This is not a recommendation from me. I am asking because I don't know. With my little bit of knowledge (the dangerous kind) it seems to me that a rating closer to 18V would give better spike protection? Possibly?
Thanks.
Connor895 Great thread. I have a question. The TVS recommended (1.5KE36CA) appears to have an operating voltage of 30.8V and peek current of 30.5A. Why would you not go with a lower voltage TVS such as the 576-SA18CA with a operating voltage of 18V and 17.5A given that our ZWs are 18V?
While the transformers are putting out 18-20 volts RMS. the peak voltage(as visible on a scope) is 28-30 volts. The 576-SA18CA would clamp the operating/RMS voltage to ~12.8 volts.
There is a way to test the TVSs. You need two transformers, a power resistor, and an oscilloscope. Put the two transformers in series so the maximum voltage from one to the other is the sum of the out voltages of each one. Remove all of the electronics, such as locos and tenders and anything that has a TVS in it. Put the 100 ohm power resitor in series with the transformers. Then put the resistor and the other output of the transformers across the Lockon. With the scope, look at the waveform across the lockon. It should show clipping at about 30 volts. Now, if you have several TVSs you won't know if all of them are working. To test each one, you would have to separate them somehow. Don't test a loco or any electronics with a TVS this way.
Thank you Rob.
I just got a postwar ZW with a bad breaker. Is a 15 amp automotive breaker the right choice to replace it? 'Cos I just put in a Littelfuse 15 amp breaker, and the durned thing practically arc welds without popping...
Mitch
To paraphrase Lionel: The ZW's internal circuit breaker is designed to protect the transformer.
It's trip point is too high to protect commonly used wiring or much of anything else. Many people use smaller external breakers to provide a lower trip point for individual transformer outputs. I like to put one on each of the "Hot" terminal posts, "A" through "D". I use Lionel Postwar #91 electromagnetic, adjustable circuit breakers. When properly adjusted they will trip instantly on a short.
There are many other options.
Does it ever trip? If so, how long does it actually take? Thermal circuit breakers provide the useful function of modeling the approximate temperature of the wiring that they're protecting. This prevents what is called "nuisance tripping" on harmless momentary overloads. But it's possible your replacement circuit breaker is simply no good.
Individual breakers in series with the output terminals other than the common can be useful for two purposes: One is to stop fault currents when those terminals are accidentally connected together, as at block gaps. The other is to allow safe use of lighter wire for feeders, for example, AWG 16 with 10-ampere breakers. However, the common circuit breaker (15 ampere rating in your case) should still be retained if the currents in the individual circuits can sum to more than its rating (40 amperes in the 10-ampere example).
Did a quick test. At full power on the D-U contacts, the new breaker trips at around 5-7 seconds, so it's working, but with the casing off I can see smoke coming off the wiper, so I'm wondering how much damage that sort of thing does to the roller...
Thanks to Bob, BF, and others who have posted here. CTT is a terrific resource. Based on the knowledge I gained, I placed TVS diodes across each of my lock ons and will install them in the modern locomotives I have as I open them for service from time to time.
I just purchased 10amp breakers for use on my zw for my layout on my power feeders. they are bussman 250vac resettable breakers. i have my layout wired with 14gauge wire for the power feeders...here is my question...
I want to wire red indicator bulbs to come on when the breaker trips. How would i do this, if i can...the zw indicator bulb is the type of action i am looking for....i am putting this on my layout and a layout for a xmas display and i want people to see when the breaker trips...
thanks
Put the lamp in parallel with the circuit breaker. When the circuit breaker is closed, the lamp will be looking at a short circuit. When the circuit breaker opens, the lamp will be in series with the load, which will probably be a short circuit (or something close to it if it drew so much current that the breaker just tripped). That will light the lamp. Even when the fault is cleared, the load will probably have such a low resistance that the lamp will remain lit. So, only if you disconnect the load entirely (take the locomotive off the track, for example), will the lamp go out.
I use the tvs all around track and behind zw plus use fast acting breaker
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