# transformers in "phase"



## peterbilt379 (Jan 4, 2013)

When using more than one transformer in a layout, make sure they are in "phase". System will be more compatable. Real simple to check..


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## alman (Oct 22, 2012)

Do you mean two transformers in parallel?

Just asking !


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## peterbilt379 (Jan 4, 2013)

At the risk of alienating the technicians here Ill try to explain. When two or more transformers are in "phase" is the same as saying the polarities are synchronized. AC current (alternating current) operates on a 60 cycle or times per second. Its not really a "hot" or "ground" sytem. Its more of plus voltage (source) to a minus voltage (common or return) system 60 times per second. One transformer mite be on the plus voltage phase while the other is on the minus voltage phase. When outta phase the voltage difference tween the source terminals could be as high as 40 volts. In my case I use 2 275W ZW's to run the trains & 2 190W KW'S run all the switches/lites/operating acc's. They all have a commom common or return so to speak. Heres how to check out two diff transformer say a ZW & KW. Plug them both into the same outlet or power strip. Take a jumper wire and connect it to both transformers at the "U' binding posts. Take another jumper wire and connect it to variable post say "A" on the ZW. Adjust variable output voltage of both transformer to 12 volts. Take the jumper thats connected to post "A" on the ZW and touch it to post "A" on the KW. If there is little or no spark they are in sync or phase. If there is a noticeable spark, pull out the plug on the KW turn it 180 degrees and plug it back in. Try the test again. No spark they are in sync or phase. If you dont wanna use the spark method use a multimeter or volt meter instead. Instead of the jumper wire on the "A" posts use the leads of the mutimeter. If in phase it should read 12 Vac if not itll read 24 Vac. Keep the jumper wire tween the "U" posts connected to the transformers forever. You can use this procedure for as many transformers as you need. Make sure you mark the plug if you unplug it. This is handy for running two trains on two diff loops. Also for connecting acc's far from transformers. Just run a "hot" wire to acc's. Instead of running a separate (common) wire from a transformer you can tap into the nearest common source say a cross tie from nearest track. Regardless of which transformer you use. Be careful tho. Lionel switched the common post on some transformers. E.I. 1033/1044/LW/TW/ use "A" post as common. They used Post "U" for variable voltage. No one knows why. Im sure this has confused everybody by now. Im not real good at explaining how or why things work. Im sure one of other the technicians on here can explain it better. Good luck....Rob


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## Dave Sams (Nov 24, 2010)

What he said

Having all the transformers in phase (yes parallel and in phase too) makes wiring a lot simpler and operating the train less exciting when going from one block to the other.


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## gunrunnerjohn (Nov 10, 2010)

This is not as difficult as it sounds, all that's required is to swap the plug orientation until you have them all in phase.


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## peterbilt379 (Jan 4, 2013)

Darn...Looks like I got long winded again. Havent seen anything here about having transformers in phase. I just thought Id throw in my 2 cents. Trying to contribute a little knowledge to the cause..Rob


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## gunrunnerjohn (Nov 10, 2010)

No objection to adding to the knowledge base, just didn't want to scare anyone off.


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## Texas Pete (Sep 28, 2011)

Currently (oops) I have two transformers for train driving and one for accessories. Although they are properly phased and the commons are tied together I prefer to not drive a train through blocks that use two different transformers. Why tempt fate? Instead, each of the blocks can be switched to either transformer by means of a single pole, double throw, center off toggle switch, so that when travelling between blocks both are set to operate from a single transformer. In the center position no power goes to that block.

Pete


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## peterbilt379 (Jan 4, 2013)

That sounds like a good system. There are so many different ways to wire a train set. Especially when using two or more transformers and having 2 or more trains running. It boils down to wantever works for you. One thing Ive learnd over the years is the less wire you use the better. keep on keepin on Rob


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## servoguy (Jul 10, 2010)

When I had my layout in California a few years ago, I had two KWs which required that I be able to switch each block among 4 transformer outputs. I used rotary switches but had to be careful switching them. 

I had the layout in two bedrooms and had two KWs in one bedroom and a single KW in the 2nd bedroom. The two bedrooms were isolated from each other. I frequently ran the train across the insulated pin that separated the two parts of the layout and never had any trouble. I was careful to make sure that the voltages on either side of the insulated pin were close together. 

I had a conversation about this with Bob Nelson on the CTT forum. Doing what I did is not as risky as some people might believe. With the transformers set to about the same voltage, the fault current from one transformer to the other as the train bridges the insulated pin is very small and doesn't cause trouble. Now if the transformers are not phased correctly, there can be a very large fault current and something may emit death smoke. 

To make sure the transformers are phased the same, I use an extension cord with a polarized plug which I buy from Home Depot for about $1 and check the phasing after I install the cord. No, there is no L for Lionel on the plug of these cords. 

Some engineers on the forums are advocating having the accessory transformers out of phase with respect to the transformers used to run the trains. I don't think this is a good idea as there can be unexpected high voltages between different things. I'll buy the heavier wire for the return and keep things simple. Also, even though the NEC says that 48 VAC is safe, it is not safe if the connection between you and it is good enough.


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