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 differen
I think the question is a matter of what happens when an engine with multiple pickup rollers is crossing into another block. If one roller is in one block and the other pickup roller is in the next block, and they are both linked together, how does this work? How do the transformers deal with it as momentarily they are electrically linked? They wouldn’t be if only 1 pickup roller were used but nearly everything out there has 2.
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 reas
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.
If you are new to our forums, welcome! Below is an outline of our general forum rules.
…
Thanks for participating in our forums. Your contributions make our forum a great resource for train enthusiasts from around the world. Your assistance policing our forums helps keep the environment positive and enjoyable for people of all ages.
Now, to the rules:
…
No personal attacks or name-calling. Please keep conversations cordial. We understand that there will be differences of opinion. Please don’t let those differences turn ugly. Accept that others might not have your same point of view, don’t sink to personal attacks. Nothing is gained by doing so.
…
May 1999 CTT has the best article by Mark Horne on 3 rail dual cab control. The toggle on your control panel for a block if to the left then the left transformer controls one locomotive. That loco stays with that transformer. If to the right then another loco controlled in that block by the right transformer. This article tells how to make a control panel and wire the toggles and the buss wires from the toggles to the track and from the transformers to the toggles. It has a easy to understand diagram.
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.
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.
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.