2 transformers on same track

No that is not recommended.  But you can split the track up into blocks so that each transformer only has to work a partial section of the loop.  But the transformers MUST be in phase with each other.

AND, as you span the tracks powered by both transformers the voltage should be the same on both transformers.

Should you go with two blocks ( one transformer per block) both transformers need to be in phase.  You can do a search for phasing.  Good luck.

It is possible to parallel transformers, AAMOF, Lionel actually shows a configuration of paralleled transformers in the TPU manuals.  Note that these are fixed voltage transformers, so there's no issue of significant voltage differences.  Also, they should be in phase as well.

Paralleling variable transformers is probably not a good idea.

A gentle word of caution.  If you do connect multiple transformers in parallel, ensure that both are firmly plugged in before switching on the power. Otherwise you can have quite an electrifying experience if you happen to touch the mains plug prongs of one when the other is powered. 

I have wondered the same thing as 842.  I understand the comments made by Susan, Anthony, and Nicole.  I have heard Marty's (not recommended) and gunrunnerjohn's

(probably not a good idea) from other people before.  However, when I asked a friend

who is an electrician (but not a model train operator) he said it should work if you could

connect the throttles with some type of bar the would keep voltage levels the same, of course they would have to be identical units, for example two cw-80s.  As you throttle up or down the bar would advance or reduce voltage the same for each unit.  I've not yet

been willing to risk engines or transformers to try this, but is there a specific reason why

this would or would not work.

Thanks in advance for any input,

Steam Rules

"a country boy can survive!"

I'm gonna' have to strongly disagree with your friend on the point above!  Connecting two CW-80's in that manner, or any electronically controlled voltage transformer, is a very bad idea!  You would probably get away with it with old PW transformers, though you'd doubtless have to replace rollers more often.  Many of the electronic transformers would shutdown (or worse) doing that.

This would actually work with two phased CW's, as the triacs in the transformer that might be set a fraction lower would not mind being back fed at all, and will not present an overload to either one.  Each CW would bear the load presented, as 5 amps is reached, the load would be shared more so equally.  I do this with parallel PM-1's all the time, but the "foldback" feature of the CW might present issues.  I will try it and report back!

NOT recommended for traditional postwar transformers, though!  This will pose a definite threat to the safety and longevity of secondary-tap type units.

Thanks for the feedback G-john, ADCX Rob .  My friend was not familiar with the internals of toy train transformers so he said "use caution", hence my not having tried it yet.  But if you can use two PHASED cw-80s to run seperate blocks that are paralleled every time multiple pick-up cars or engines cross the "break" no matter what the speed, I can't see what would be so dangerous just wiring two identical units, properly phased, with voltage controls locked in step to increase or decrease identically. Why would this not work similarly to a 160 watt power source with voltage control?  I don't disagree or doubt what you all are saying, I guess I just don't understand why, what will happen if I do it? Looking forward to ADCX Rob's report back.

Steam Rules

"a country boy can survive!"

You can lead a horse to water but a mule is another matter. There are many good reasons why transformers should not be paralleled. They have been discussed many times and it seems there is always somebody who knows better. Bear in mind there is only ONE manfacturer that has recomended paralleling transformers and even then only one transformer when used in one application. That company is Lionel, the transformer is the PH180 and the application is the input to a TPC 4.

But go ahead, I can understand the reasons why the idea looks good. I look forward to the post about transformers that have failled, layouts that don't work properly, and engines that have mysteriously failled. I am sure that no matter what the outcome there will be somebody that will extoll the benefits he has had from paralleling all manner of power sources.

Al

Al......I understand the horse/mule thing, but the rest of what you said in your post, does  that apply to operating all (lionel, williams) electric trains?  I get that it might not be a good idea for engines with sensitive electronics, but would the same problems you identified apply to conventional type engines?  My thought was just to have the extra power to operate multiple engines on the same large loop without loss of power.

Steam Rules

"a country boy can survive!"

It's not a good idea, period.  The only way this works is with parallel 135 or 180 power house bricks fed to a TPC-300 or 400 device.  The only reason this is because that's what the TPC was designed to do.

PW transformers are not identical inside.  The windings could be slightly off.  If the voltage isn't identical, you will get back currents in the lower voltage transformer and that's not a good thing.  A modern switching power supply is worse.  Most of these devices used modified sine waves that alter the wave form.  Same issues if the devices aren't EXACTLY the same (actually worse since there is more than just a transformer winding to deal with).

If you need more power, buy a higher rated unit.

Not entirely correct:

Exactly the BEST advice.

I'm with Steam Rules, When I was running all postwar lionel we did multiple ZW all the time. If we had a slow spot on the carpet central, just put in another ZW. OK I believe all of you when you say it's bad idea. But what happens? what is the danger? I just want to know.....Now I only run one Z4000 and modern trains. 

If you already know the answer, why ask the question?

At times in the past on a large layout I paralleled a pair of fixed voltage 135 watt Powerhouses linked to a Track Power Controller[TPC 3000] for 270 watts to enable operating two long,lighted passenger trains in the same power district. Note the advice from Nicole regarding backfeed and, only parallel identical fixed voltage units such as the Powerhouses or "bricks" as they are often called. You are apt to have circulating currents as also noted above when using variable voltage units that are difficult to equalize [such as the pw ZW].

A better long term solution when running multiple long passenger consists is to dispense with paralleling and equip the passenger cars with LEDs in place of incandescent bulbs.

After reading the post from ACDX Rob it occures to me that there may be some misunderstanding of what we are talking about when we talk about paralleling transformers. The instructions Rob posted describe phasing two transformers connected to ADJACENT blocks that are otherwise insulated from each other. Now as some have pointed out that during the brief time an engine or lighted car is bridging the joint the transformers are indeed paralleled. There have been many post on this and other forums about the dangers of burned wires and other problems caused by this condition if the two transformers are not close in voltage. This is a condition to be avoided if possible but this is almost inpossible on any large layout. When it cannot be avoided it must be delt with and mitigated as much as possible. In any case it is a momentary case.

What we are talking about is the perminent connecting of two transformers in parallel before they are connected to the track. This is done on the assumption that the outputs of both will add together giving the power of both to the track. Now the reality, It has been a long time since I attempted to get this deep in theory so I apologize if not exactly correct but it is close. Each transformer will act as a point source of voltage. Lets say that one puts out 10 volts and another 12 volts. When connected in parallel there will be a difference of 2 volts between them. As re result of this you will have a current from the 12 volt source to the 10 volt source. Since you used heavy wire to connect the two units the resistance will be low and this current could be quite high. If you now put a train on the track this load will affect the equation to some extent but the difference dosen't go away and you do not have trains running on the track the whole time these transformers are connected together. Now 2 volts is a big difference, let's say the difference is 2 tents of a volt (.2) and you have good wire so the resistance is one tenth of a Ohm (.1) this current is only 2 amps. That is almost enough for another engine.

Now Rob, I do not understand your addition of the comment (sic) to my reference about recomendations. Sir, the facts are facts and just because you may find them aggravating does not change them.

Al

An absolute problem when you do this to one or more outputs of, say a  Z or ZW, a somewhat serious cause for concern when you do this between/among outputs of phased postwar transformers.  Damaging high amperage fault currents are quite possible.

But not an issue between outputs of separate CW's(as pointed out in the Lionel diagram).  While there may be a measurable voltage potential between circuits, there will be very little if any fault current even if one is set to 5 volts and the the other to 17 volts.  The one set to 17 will carry nearly the whole load through the triacs, it won't "backfeed" or short out the other one.   Try it.

So, can you parallel two CW's mechanically and will it work?  Well, sure, for power.  But it's a very clunky proposition, and then you have to consider the button operations too - Bell, Whistle, Direction.  It's just not practical.  Get a GW-180, ZW-C, or a ZW-L if your power demands require it.

ADCX Rob....

From the standpoint of my trying to understand what would work (or not) and why; or even how to make it work (with CW-80s, of which I have several), you seem to have summed it up best;  paraphrasing :  'will it work? sure, for power. But, its just not practical. get a GW-180 (etc.) if power demands require it.'  Sounds like good advice -I believe I'll go with the larger power supply for higher power requirements (main lines, longer trains) and reserve the CW-80s for yard, siding and switching needs and powering lights and accessories.

Thanks to all for such an informative discussion,

Steam Rules

"a country boy can survive!"

Well sometimes the mule turns out to be a donkey. I will try one more time. ADCX Rob keeps refering to an instruction page he posted. Appearently he has decided not to read it so I will quote from the first paragraph. "...you may decide to create two isolated blocks of track. Trains in each block are controlled by seperate transformers." The bold indications are mine. Nowhere does it mention any model transformer. Rob's contention is that the triacs will somehow minimise this problem. In fact the reverse may be true. It will be even harder to sync the operation of one output to that of the other thus causing an instanious difference in the output.

I have tried to impart the correct knowledge of the subject. If you wish to take the side of the donkey I cannot stop you and I wish you luck.

Peace be to you.

Al

ps. I apologize to other forum members. I have stretched the decorum of good taste and beg the indulgence of the powers that be. I believe this to be a serious misunderstanding in the proper use of transformers that was started by Lionel for only one instance but has been pushed by some to include cases that can be down right dangerous.

Al Werder

Sorry my bad, this is from the CW-80 equipped Polar Express set manual... but it's not unique to the PE, it's in all the starter set manuals.

Although it has happened at least once in the postwar era where Lionel recommended this wiring scheme using a KW or ZW, and posing a considerable possibility/risk of large fault currents and property damage, you don't really think Lionel would currently recommend it in their manuals(printed and online) without knowing what they're talking about?  You would be underestimating the electronics talent at Lionel.

Passing from one block to another, powered by separate CWs(or PM-1s, for that matter) does not introduced the unprotected fault currents we all grew up with using postwar transformers.  It is because of the way the power is delivered and regulated - electronically instead of mechanically. 

If you don't accept it, all you have to do is run some empirical testing.  It'll come out in the results.

If you want to do some reading on the technical aspects of the CW check out Dale's work on his Train Facts website.

Never connect transformers in parallel, use power districts (blocks) instead. Besides the problems already mentioned there is a serious safety issue. An overload or low grade short may fail to exceed either breakers ratings and not trip the circuit breakers. If the total current exceeds a safe level you’re likely to cause a fire.

Safest way to go.