Don sent this by e-mail. I’m answering here, as is my custom, so that others can join in and benefit from the discussion.
Bob,
I remember you talking about a device, that would prevent “surge spikes” as a
potential result of a short ckt on the track. But I can't find the
information. It wasn't a ckt bkr or fuse, but a type of diode I believe. I
already have both ckt brkrs and fuses in the system, but concerned about
protection between the track and a TIU.
Since I'm allready bugging you, Isn't it best that a fuse be on the
ground wire as oppossed to the positive? The ckt brkr also intierupts the black
as oppossed to the red ?
As referance this is how I have things hooked up
OR, Do you think this would be better?
Thanks for your time and thoughts
Don Baker
The gadget you’re looking for is a transient voltage suppressor, or TVS. If you search for those names, you will find a lot that I have had to say about them.
If a transformer has only one output (two terminals), it doesn’t matter which side has the circuit breaker. But, if the transformer has more than one–three or more terminals, with one of them common to the multiple output circuits, then the circuit breaker should not be in the common wire. Instead (or in addition), there should be a circuit breaker in each circuit. Unfortunately, to save money, Lionel didn’t do it this way. The result is that there is a fire danger with traditional Lionel transformers used without supplementary circuit breakers or fuses. Search on “fault current” for a lot of preaching from me on this.
Unfortunately, the CTT e-mail elves removed your diagrams. Maybe you can post them here.
Don sent this by e-mail. I’m answering here, as is my custom, so that others can join in and benefit from the discussion.
Bob,
I remember you talking about a device, that would prevent “surge spikes” as a
potential result of a short ckt on the track. But I can't find the
information. It wasn't a ckt bkr or fuse, but a type of diode I believe. I
already have both ckt brkrs and fuses in the system, but concerned about
protection between the track and a TIU.
Since I'm allready bugging you, Isn't it best that a fuse be on the
ground wire as oppossed to the positive? The ckt brkr also intierupts the black
as oppossed to the red ?
As referance this is how I have things hooked up
OR, Do you think this would be better?
Thanks for your time and thoughts
Don Baker
The gadget you’re looking for is a transient voltage suppressor, or TVS. If you search for those names, you will find a lot that I have had to say about them.
If a transformer has only one output (two terminals), it doesn’t matter which side has the circuit breaker. But, if the transformer has more than one–three or more terminals, with one of them common to the multiple output circuits, then the circuit breaker should not be in the common wire. Instead (or in addition), there should be a circuit breaker in each circuit. Unfortunately, to save money, Lionel didn’t do it this way. The result is that there is a fire danger with traditional Lionel transformers used without supplementary circuit breakers or f
When a TVS “clamps” to deal with a spike/overvoltage situation, isn’t it creating a short across the inputs? aka it prevents the overvoltage from reaching the device it is trying to protect by diverting the energy back at the source? It’s then supposed to release the clamp when the overvoltage situation is resolved? This is in oppostion to a crowbar (thyristor/SCR) that stays “clamped” until the main power is cut?
Don, I don’t know anything about DCS and TIU; so I can’t advise you specifically about your diagrams, except to say that there is no indication of which wires are connected to the transformer common.
In the engineering and scientific worlds, current flows from positive to negative in the load. For technicians whose education has something to do with the military, it flows the opposite way. The US Navy, which is responsible for technicians’ education for all the services, introduced this confusion because they thought it made it easier to understand vacuum tubes. Electrons in particular do flow from negative to positive. But outside of the navy they are considered to have negative charge, which makes electron flow from negative to positive equivalent to charge flow (current) from positive to negative.
In the US, there is no association of red and black with common or grounded conductors. (There was until recently in England.)
There is no need to put fuses and circuit breakers in series. One or the other is all you should need. I like automatically-resetting automotive breakers, which are very similar to those built into toy train transformers. You can often get them for a few bucks at parts stores.
Chuck, the TVS doesn’t create a short circuit. It just holds the voltage to the voltage that it’s rated for. This does prevent any overvoltage from reaching the protected device. But energy is not diverting back to the source. Instead, it is absorbed and dissipated as heat by the TVS. The TVS can handle a lot of power; but only for a very short time. Fortunately, there is not a great deal of energy involved in the inductive voltage spikes that it is called upon to deal with. When the source has expended its stored energy, the circuit voltage just drops back to a normal level.
Concur with everything you said, Let’s see there is the Suppressor grid, Collector grid, Secondary, then the Pentode, Oh Yeah, it all comes back.
Well, I sure found a lot of information, will take me a week to get through it all. Trying to figure out all the characteristics, clamping voltage, operating temp, package rqmt, breakdown volt, peak surge cur., ppp disapation, et. al…
Or maybe just by a box from an train electronic supplier for $50.
Now I remember why I didnt do it before, back to the research.
Bob, thanks for the explanation. Followup qustion. When a TVS fails from an overload does it just cease to function as a TVS (aka circuit is unprotected) or does it do something else?
We reviewed two capacitors in the dec 1998 issue - and I’d bet both outfits are long gone - the Clark 007 voltage stabilizer and the Soundmaster non-polar capacitor.
We also reviewed the QSI PowerGuard in the May 1999 issue.
These reviews were directly connected to a spate of loco frying, which happened at random, during our product testing. The only problem with testing any of the surge protecting systems, was that you had to try to fry something. We didn’t have any tragic results during testing, but we didn’t know if the products prevented/filtered the surges, or if we simply didn’t duplicate the conditions for a surge.
They can fail either open or shorted. If shorted, your trains will still be protected. Whatever overcurrent protection, circuit breaker or fuse, is upstream of the TVS will open to protect the source. If open, the case is likely to show signs of being burned. I think shorted is more likely in the toy-train environment.
TVSs are very different from capacitors. They are also small, simple, and cheap.
Don, I recommend the 1.5KE36CA for use with a ZW. That’s a bidirectional 1500 watt 36-volt axial-lead TVS, made by Vishay and many others. Mouser sells them for 50 cents (cheaper in quantity).
Thanks for the followup. The main issues that should be looked at are the clamping voltage and the total power you would expect to see handled? Would it make sense to place the tvs between the power pickups and the return feed in the loco’s? These control and sound boards seem to be the most delicate of the electronic devices we deal with.
The 1.5KE series is fine for any toy train application that I can imagine. The voltage should be selected to be higher than the peak track voltage. This is 1.4 times the maximum RMS voltage plus a few volts for the whistle, plus a little safety margin. Here is the Vishay data sheet:
I have mentioned putting them in locomotives before. In fact, they are so small and so cheap that I have suggested putting them in both places, on the layout and in the locomotives. That way, your locomotives are protected wherever they go and visitors’ locomotives are safe on your layout.
Bob: I’m pretty sure this is the thread Don was referring to. Some excellent info here about transformers as well as the TVS gizmo[tup]
I brought it back to the first page of the forum a few days ago and we planned on bringing it back again around Thanksgiving for when folks start setting up their trains for the holidays. Great stuff here!!! [:)] You da man Bob!!! [:D]
