To find out how to wire more than one transformer to a multiple loop layout where all loops connect I have purchased Greenburg’s Model Railroading with Lionel Trains volumes I & II, The Lionel Fastrack Book, and Lionel Fastrack Model Railroads book.
They talk about how to make sure you have both / all transformers in the same phase and explain how to do that.
They explain to break the loops into control / power blocks which I understand. What I don’t understand is when an engine is going from one block, powered by transformer 1 to another block powered by transformer 2.
The way I see it is, when the engine moves across from block 1 to block 2 it will stall unless transformer 2 is already powered up, which means both transformers would be connected when the wheels of the engine cross the two blocks.
Am I wrong ? And wouldn’t that create a problem between the two transformers? And what about there being a voltage difference? I would think it might burn up something inside the transformer if not inside the engine.
I know there are a lot of folks here that have been around before the new Command Control systems came along and have used multiple cabs in the same scenario I am using. I would greatly appreciate some information on how to operate between two power / control blocks with two or more transformers.
Thanks,
Bill
Sorry--this post dealt with HO DC operation, which apparently is not what the topic is about, and has been edited/removed.
HO DC post removed.
I still use block wiring on my DCC n-scale layout although there aren't as many blocks as there would have been if it were DC. My reasoning was that if there was ever a wiring issue it would be easier to isolate where it is. I also keep tracks turned off that aren't in use, especially if there is an engine parked on one that isn't going to get used. I want as much power as possible available for what is actually running. It probably isn't necessary but it's just what I do.
Bill, many of the replies so far seem to be about 2-rail DC operation, which is not common with toy trains.
You are right to be concerned about this problem. When two transformer outputs are connected together, unless they are closely matched in frequency, phase, waveform, and voltage, a fault current will flow through the pickups. This will have two effects:
The transformers may be overloaded, even if not long enough nor severely enough to trip a circuit breaker. If your locomotive or lighted car has pickups on separate trucks, the fault current will flow through the wiring between them. It could be more than that wiring can stand. If the train should stop with the gap bridged, of course the fault current will continue to flow. If the outputs are from the same transformer, like a postwar KW, Z or ZW, there is no circuit breaker protection. The current will continue until something melts.
Even if no circuit breaker trips and no wiring burns up, when the fault clears as the second pickup roller crosses the gap, the transformer will generate a voltage spike which can easily be hundreds of volts. This can destroy the electronics in many modern locomotives.
A block system is a safer way to operate. Connect the center rail of each block to the common terminal of a switch that you will use to connect to any of your transformer outputs. Then you can arrange for each block that you enter to be powered from the same output as the last one. With two transformer outputs, you can use simple SPDT switches. If you get center-off switches, you can also shut a block off completely.
In any case, it is a good idea to have the transformer outputs used for trains in phase. This at least reduces the fault current when you make a mistake and cross a gap between differently-powered blocks. For the same reason, I advise adding automotive circuit breakers to the individual outputs of multiple-output transformers, to get the protection that Lionel left out. If you have electronics-intensive equipment, it is also a good idea to install transient-voltage-suppressors.
Bob Nelson
Block control wiring schemes typically use a single pole double, center off (SPDT) or a double pole double throw, center off (DPDT) toggle switch attached to each block. In its simplest form, block control is used to run two trains on separate transformers or power supplies. When running two trains, the toggle is flipped to the appropriate transformer before the engine enters a block. The toggle from the previous block is then set to the off position. This scheme is used while running around the layout with each engineer flipping the toggles to connect his throttle to each block.
If you're only running one train, you can simply connect all the toggles to the appropriate throttle.
It's not a good idea to bridge sucessive blocks controlled by two different transformers even if they're phased.
(This is a response to a post that has now been deleted.)
You're new here; so you might not have noticed that we tend to be civil in our discussions and don't usually call each other names. If you disagree with others' opinions, you should be able to make your case on its merits without calling them "rats".
If you want to see "what is the worst that can happen", take a multiple-output traditional transformer, set one output high, the other low, and connect them together. Have a fire extinguisher handy.
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I appreciate all the help. As a newbe to 3 rail I didn't want to burn something up. Bob and V8Vega's advice have helped a lot.
So if I understand right, if I have two trains goin around two connecting loops then the loops need to be broken up into several blocks. Since train, "A" is controlled by lets say transformer "1" and train "B" is controlled by transformer "2", the tains will maintain control by the same transformer regardless of where it is on the track. This is done with a series of switches.
This is what I thought. The only thing I didn't understand and was not clear in the books I read was that you could have two or more transformers connected to the same block but not used at the same time. This is done through the switches.
Thanks for clearing things up. I never thought it was a good idea to have a train corss from one block controlled by one transformer into another block controlled by another transformer while both transformers are powered up.
You do indeed understand it right. Here are some fine points for your consideration:
A block system as described, unlike the one-transformer-per-block approach, can have as many blocks as you want, with only as many transformers needed as there are trains to be run.
While SPDT-CO switches are close to ideal for two transformers, there are combinations of switches that you can use to deal with many more transformers. Some like to use rotary switches; but these can be expensive; and they have a problem with briefly connecting a block to unintended transformers while switching between the two that you want.
With two side-by-side transformer controls, like the handles on a ZW, it helps to mount the switches with their handles moving left-right rather than up-down.
If you want your transformers to be in different locations, there are simple ways to connect two sets of switches to insure that both operators do not try to power the same block.
The switches can be mounted on a (perhaps stylized) map of your layout.
The following link describes the problem and provides an automatic solution for trains running in both directions across the power break.
Two power blocks with two transformers
Tim, the single-transformer scheme, if I understand your description, would not allow independent speed control of multiple trains. Is that what you meant?
As you know by now, I would disapprove of the multiple-transformer scheme because of the safety issue. One other consideration is that, while each transformer may be unloaded much of the time, short-term overloads may undo some of that advantage if voltage matching is not perfect.
I think that the arrangement that I recommended is enough different from either of these that it makes a total of at least three methods.
Fine!
Rheostats would work, and they don't have to be matched as long as they are supplied from the same transformer. They were commonly used before the war, with transformers that could be adjusted only in rather coarse steps or with batteries. Although DC supplies ("power packs"), as used with HO more recently, commonly had rheostats inside, the adjustable transformers we are used to for AC toy trains--and those used in Flyer "rectiformers" and with separate rectifiers, like the 14, 15, and 16--do not use rheostats but rather a sliding or rolling tap on the secondary winding. This gives much better voltage regulation but allows big currents to flow between transformers in the AC case.
The Flyer DC arrangement, unlike AC operation, does allow safe block transitions even if the transformer voltages are not matched. The rectifiers isolate the transformers. Each one can supply power to the train (the one set higher gets that honor); but the rectifiers prevent them from supplying each other. If they're set to opposite polarity, however, all bets are off.
Tim, note that, as I mentioned above, there is no problem running between DC supplies, like those traditionally used with HO and N, and with some American Flyer. The rectifiers between the transformers and the track isolate the transformers from each other.
The reason for having two (or more) pickups is that the center rail is not continuous. Specifically, it must be interrupted where it crosses over the outside rail in a turnout or crossing. I think the situation is similar for American Flyer operation, except that, instead of multiple rollers, you have multiple wheels on the trucks that collect the current. In the two-rail case, of course, the rail interruptions occur where the (always outside) rails cross over each other. Aside from those considerations, track and wheels are never perfectly clean, and the connection to the track is going to be broken occasionally. So I think we have the same situation in both cases, that is, brief connections between supplies, or longer ones if the train stops in the right (wrong?) place.
In lighted cars continuity is not so critical, so a single roller often suffices in a cheaper car. But two are frequently used to reduce the flickering of the lights. Williams interestingly uses two pickups, but connected to two separate lamps and not to each other.
With a rectifier, the same currents flow in the wires between the transformer and the rectifier and in the wires between the rectifier and the track. The (bridge) rectifier acts like a DPDT switch, reversing the connections 120 times each second; so the currents are flowing in the opposite directions on each side of the rectifier half the time. But they are the same currents. Therefore, with a perfect rectifier, the transformer's circuit breaker should trip just the same whether the short circuit is downstream from a rectifier or not.
I think that the difference that you observed may be due to the fairly high resistance of the now-obsolete selenium rectifiers that American Flyer used in their rectifier units. They did claim that it could carry a maximum current of only 6 amperes. Even assuming that this number was no exaggeration, only the smallest of train transformers would have had a circuit breaker that could protect such a device.
I simply wire a 6 amp or so circuit breaker in series with my track outputs. If a significant fault current was to flow due to different voltages on my transformers then the breakers open. This almost never happens as even when a fault current flows , the fault current is so brief (unless an engine stalls) that nothing happens. E units do not even trip. The voltage spikes with new equipment as Bob nelsen point out may be my problem. I have not had a problem yet but I run mostly post war.
My post refers to 3 rail ac model trains. I use modern resetable circuit breakers in series on the output when using multiple postwar transformers running different blocks. This gives me a little piece of mind should something stall between blocks. If voltages are the same , no significant current will flow. My trains use mostly mechanical e-units . I may need to get tvs devices to protect against voltage spikes that can occur. If they will protect??
I use PW ZWs. They are Phased. I have many many blocks, including sidings and storage yards. I have 4 mainlines that intersect. Basically an engine can go from any siding/storage yard to any place on the layout. The center pin is removed at the block connection. I use GG and Lionel O27 tubular. The center pin is replaced with a plastic toothpick bought at the local grocery. Power to the sidings is managed with toggles and Atlas 205 slide switches. The mainline blocks used a TMCC BPC controller - which is no more than a group of SPDT switches. I used TVS diodes at each power drop along the layout for spike control. I use Fast-blow and resettable fuses - 8/10 amp - to the various sidings/mainlines. NO PROBLEMS. I recognize and appreciate bob's point about multiple transformers and always have it in mind as I run the trains - 4 at a time crossing blocks here and there. I use the 2RC and the UTAC relays among other types of relays to manage accessories, lights and signals.
Protection from 120-volt faults is why I recommend grounding the layout common (that is, connecting it to the equipment ground of the branch circuit powering the layout, which is connected to the earth). Any such fault will trip the branch circuit's breaker, in the same way that electrical appliances with three-wire plugs are protected.
No dry cells: "The UTAC circuit board is powered by an AC transformer between nine and twelve volts....Each of the eight output switches can drive up to two amperes of AC power at up to thirty volts." and "[2RC i]nputs are powered from a fixed-voltage, AC transformer between eight and twenty volts or from train power."
A TVS diode protects a circuit from overvoltage, but does not provide any sort of back-feed prevention. A conventional diode could do this if desired, but only on a DC circuit, not with AC.
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