Brand New transformer

[nickt22]

In order to be able to operate two trains at different speeds and directions in different areas of the layout, i got a CW-80 watt transformer for christmas. Will I have problems if the first transformer I have is a MRC transformer.

 

Clueless as always,

Nickt22

[jefelectric]

Don't understand your question.  What kind of problems are you expecting?  If you isolate the two sections of track, it make no difference what kind of transformer you are using.

[lionelsoni]

John is right of course:  Two independent tracks, not connected to each other, are electrically just like two different layouts.

But, if you connect the tracks together so that the trains can move from one section to the other, things get complicated.  Whether you make a gap in all three rails at the boundary or a gap just in the center rail, which is what is usually done, when a train crosses the boundary, its pickups (and wheels if the outside rails are gapped) connect the two transformers' outputs together.  Only if the two transformers are putting out the exact same voltage waveform can you get away with this.  Even with two conventional sinewave transformers there is likely to be some voltage difference.  Getting the transformers in phase with each other is easy.  Setting the voltages the same is difficult.  Making a CW80 have the same waveform as a normal transformer is impossible.

When the transformers are connected, a fault current will flow.  This will cause arcing at the track and may damage the transformer(s).  (The CW80 already has a reputation for unreliability.)

A much better way to do this is to use a single-pole-double-throw switch for each block, to connect the center rail for that block to one or the other transformer's output.  Then both blocks can be powered by the same transformer when you cross the gap.  Furthermore, you can use more than two switches and divide the layout into smaller blocks, so that the entire layout is not powered by the same transformer when one train tries to cross the gap.  If you use center-off SPDT switches, you can stop multiple trains at various places while still running two other trains.

[Anonymous]

John is right of course:  Two independent tracks, not connected to each other, are electrically just like two different layouts.

But, if you connect the tracks together so that the trains can move from one section to the other, things get complicated.  Whether you make a gap in all three rails at the boundary or a gap just in the center rail, which is what is usually done, when a train crosses the boundary, its pickups (and wheels if the outside rails are gapped) connect the two transformers' outputs together.  Only if the two transformers are putting out the exact same voltage waveform can you get away with this.  Even with two conventional sinewave transformers there is likely to be some voltage difference.  Getting the transformers in phase with each other is easy.  Setting the voltages the same is difficult.  Making a CW80 have the same waveform as a normal transformer is impossible.

When the transformers are connected, a fault current will flow.  This will cause arcing at the track and may damage the transformer(s).  (The CW80 already has a reputation for unreliability.)

A much better way to do this is to use a single-pole-double-throw switch for each block, to connect the center rail for that block to one or the other transformer's output.  Then both blocks can be powered by the same transformer when you cross the gap.  Furthermore, you can use more than two switches and divide the layout into smaller blocks, so that the entire layout is not powered by the same transformer when one train tries to cross the gap.  If you use center-off SPDT switches, you can stop multiple trains at various places while still running two other trains.

Bob,
One of these days I swear I am going to figure out what you are talking about!

Wife bought me a book on layout wiring, so hopefully they cover all this.

My question is, if this should be a concern then why does Lionel recommend the opposite?  Not questioning you, just trying to understand this... I can program computers to do just about anything I want them to do, but when it comes to electricity, the only thing I know is don't touch the wires together while there is current running through them... that and don't stand in water when working with electricity.  

[lionelsoni]

Lionel is a company that once sold 220-volt DC controllers for kids' trains.

But seriously, Brent, tell me what you don't understand and I'll take another stab at explaining it.

[Anonymous]

Lionel is a company that once sold 220-volt DC controllers for kids' trains.

But seriously, Brent, tell me what you don't understand and I'll take another stab at explaining it.

Bob,
I think the problem is I don't have any 'visuals' to help my understand what you are explaining.  I am planning a rather large layout and I want to build it and wire it so there is little to no chance that I will have to take a transformer in for repair because of incorrect wiring.  I also want to be able to run all the trains on all the tracks, except for the trolley line and the logging line.  I am planning 3 seperate loops and would like to be able to safely send a train from one to another without shorting out an engine or a transformer, or causing a 5 alarm fire!

[ADCX Rob]

You need to study these tips by MartyE:

Marty's Phasing Tips/Tricks

Rob

[lionelsoni]

On page 83 of the current (January) issue of CTT, there is an article by Neil Besougloff on how to wire a block system.  It has some errors and omissions, but with a little explanation of them, might be useful.

For some reason, he says to use "double-throw double-pole" switches.  (These are normally called "double-pole double-throw" or "DPDT".)  He shows DPDT switches in the diagram, but with only one side wired up.  This is equivalent to "single-pole double-throw" or SPDT, which is what you should look for.  Actually I strongly recommend that you get SPDT center-off switches, to allow you to shut off a block entirely, freeing its transformer up for use elsewhere on your layout.

The transformers are shown with two terminals, marked A and U, with U connected to the outside rails.  Whether this is right depends very much on what transformer(s) you have.  If you can tell us that, and whether you are using or intend to use any track-activated accessories, we can sort out which terminals to connect where.

One thing which you should avoid is running between blocks powered by different transformers or, especially, by different outputs of a multi-train transformer.  This can be dangerous.  The proper way to transfer a train between transformers is to throw the SPDT switch for the block that it's in.  With decent switches, you can even do this while it is moving.

As for "phasing", it helps to reduce the danger when you might accidentally run between blocks powered by different transformers.  With the same type of transformer on both blocks, you can possibly get the voltages and waveforms to match.  But you will never get a CW80 to match a postwar transformer, for example, because the waveforms of some modern transformers like the CW80 are not sinusoidal.

Now, with more than two trains, things become only a little more complicated.  You need a switch for each block that can connect the center rail of that block to any of the three or more transformer outputs available.  There are rotary switches that can do this; but you can also use ordinary toggle switches:  For three transformer outputs, use an SPDT switch just as if you had only two outputs.  However, connect one of the terminals of that SPDT to the common of another SPST, which in turn connects to the remaining two transformers.  Lets call the center, common terminal of each switch C and the other terminals 1 and 2:

center rail----C   (common of first SPDT)

1----C'   (common of second SPDT)

1'----transformer 1

2'----transformer 2

2----transformer 3

Now there are two switches for each block; and you can see that various combinations of their handle positions will connect the block to whichever transformer you want.  Switch 1, or both, should be center-off to allow the block to be switched off completely.

Now for 4 transformers, we can use a DPDT, which is just two SPDTs in the same case, along with one SPDT:

center rail----C   (common of SPDT)

1----C'   (first common of DPDT)

1'----transformer 1

2'----transformer 2

2----C"   (second common of DPDT)

1"----transformer 3

2"----transformer 4

This sort of thing can be extended ad nauseum, with 3 switches handling 8 transformers and so on; but 4 is probably enough for most people.

Does any of this help?

[Anonymous]

Bob,
Yes that helps a lot.

I'll probably be asking you a lot of questions when I start designing/building the large layout.  So far I have where I have 1 mainline that doubles the entire layout twice (241 feet of track), a second line that doesn't follow the entire layout (approx 113 feet of track), a trolley line (bumper to bumper - approx 41 feet), and a logging line of O-27 approx 23 feet.

I hope to be able to run 2 or 3 trains on the mainline and 1 or 2 on the second line.

I'm not done playing with the design so I may end up with 3 mainlines, that will depend on how much of the basement I claim!

I have 1 modern ZW that I plan to upgrade to 4 180 PHs, 1 KW, 1 LW, 2 CW-80s.  I plan to purchase 1 more modern ZW with 4 180 PHs, and as many accessory transformers as I need for the different voltages for the accessories.  I will reserve the KW, LW, and CW-80s for the Christmas layout.

There will be no track activated accessories other than crossing gates and signals.  All other accessories including switches will be powered by accessory transformers.

[lionelsoni]

That many trains?  Well, you can handle 8 with three switches per block, but two of them need to be 3PDT, which you won't find at Radio Shack but can get through the mail.  However, you can do 6 trains with one SPDT and two DPDTs.  I won't tell you the circuit, in case you want the fun of figuring it out for yourself!