Phasing Transformers

As your railroad grows and you add multiple transformers, it is important to make sure that they are all in phase.  All that this means is that the common and hot terminals of the transformers are at the same polarity. For a review of the theory behind this, in addition to what you need to do to phase your transformers, take a look at this video: [youtube=]

Phasing transformers sounds complicated and technical, but it really isn’t that hard. Here’s all you need to do:

  1. Start with 2 transformers (you can add more later). With the transformers turned off, plug them into a common wall outlet or plug-in strip.
  2. Attach a wire to the common (black or “U” on most Lionel transformers) of the first transformer. If the terminals aren’t labeled, you’ll simply have to guess. We highly recommend color coding your wires. Since most Lionel transformers use black terminals for the common, black is a good choice.
  3. Power up the two transformers to the same voltage.
  4. Test the transformers to ensure they are in phase by using a test light. You can use one of our lighted accessories or a simple grain-of-wheat bulb or LED (make sure it is rated for at least 18 V AC!) Attach one lead of the bulb to the common terminal on Transformer 1 and the hot terminal on Transformer 2. On most Lionel products, the ground is indicated by black and hot by red. If you don’t know, you’ll just have to guess. If the light turns on, you’re in phase. If you don’t get a light, you’ve connected common-common or hot-hot.
  5. Now that you know which poles are the same and opposite, connect the two ground terminals with a black wire. (We recommend black due to the normal color code on our transformers.)
  6. Double check with a light from Transformer 1 Ground to Transformer 2 Hot.
  7. If you have additional power supplies to add, repeat this process by connecting another wire from the Transformer 2 common to number 3 and so on.

Ensuring your transformers are in phase takes only a minute and will be critical as you wire accessories, common-rail wire multiple track loops, and add additional power supplies going forward.

0 thoughts on “Phasing Transformers

  1. I have a couple of questions:
    1. I want to connect my remote switches to the SC-2 controller. Can I directly connect the switches, through the SC-2, to my accessory connectors on my CW-80 in order to have 14v output, or do I have to phase that transformer with my 185 power house and direct lock on? If the latter how do I do that?
    –The instructions with the SC-2 indicates that I can directly connect power from the transformer to my SC-2 which to me is the simplest method.
    2. Is it really necessary to have a constant 14v to the remote switches? Is the 185 with constant 18v truly a problem?
    I have a L shape layout that measures 4×6 on one leg and 5×9 on the other. The layout has an inside and outside loop that are connected through switches that allow for three reverse loops. I have two sidings that are blocked and can be turned on/off through SPDT switches allowing me to park trains without drawing power.
    I am powering the layout with a 185 power house and direct lockon and I control the trains through the Legacy System. I have three locomotives but only operate at max two at the same time. I have 8 command/control switches and three remote switches. I have two 80 watt transformers that are used to operate accessories. My accessories consist mostly of lights in buildings and IR reflectors, none are on tracks.

    • Andrew,
      It sounds as though your layout is probabably already pretty well wired. If things are working for you without having phased transformers, especially since the accessories aren’t really connected to track power anyway, then no, there is certainly no need to rewire your layout. You can use the CW80 directly to supply power. (If it ain’t broke…)

      I would however recommend that you set the voltage on the CW80 at about 14 volts and supply that constant power to your switch machines. This will prevent the illuminated lamps from burning too hot and melting the lanterns. The reduced voltage will also put less stress on the motor and points as the switch throws, lessening the chance of problems and extending their life. The same is true for the other accessories – your lights will last much longer at 14 volts and you won’t notice a dramatic change in brightness – in fact it may be an improvement!

  2. Phasing other transformers (pls Verify)

    I have some alternate AC supplies (12VAC) .They are Completely AC isolated.

    USE A DVM (Volt Ohm Meter on the AC measurement scale)
    (You could use a lamp as described above, but you will need to use 2 in series, so you dont blow them out )

    #1 Set Your Lionel unit for full output (18Vac)

    #2 Verify there was NO AC coupling between the transformers by
    Testing between the Lionel unit and the AC transformer (supply):
    A) Lionel Black to both polls/leads on my transformer, and
    B) the Hot (Red) side of the Lionel unit and both leads from my transformer

    AFTER Confirmation there is not coupling

    #2 Connect the Transformer in series to the Lionel unit where One of the leads from the transformer is connected to the red (HOT) terminal on the Lionel unit (a series connection)

    Measurements (using DVM):
    From Lionel Unit Black (common) to the unconnected lead of the transformer

    IF the units are ‘IN PHASE’ the Measured voltage across these are the SUM of their voltages ( ~18 + 12 = 30VAC ).
    The transformer lead connected to the RED terminal is actually the transformers common (Black)

    IF the units are ‘OUT OF PHASE’ the voltage measured is the difference ( ~ 18 – 12 = 6VAC )
    The transformers lead you are measuring on is the transformers common.

    Label and or color code your transformer (colors work wonders for keeping this straight). If you label the transformer terminals, be consistant eg common=U=Black, and the Hot=[some letter]=red

  3. I plan on using two cw80 transformers for accessory and lighting, none of which will be operated off track power( which uses a ZW360.) When phasing the two cw’s do I connect the accessory posts which I beleave would give me a lower voltage for the lights. or do I run it off the track terminals and adjust with the throttle

    • The accessory outputs on the CW80 can be adjusted to the voltage you desire. If you are only controlling accessories then you can wire them to either terminal and adjust the voltage.

    • Dennis,
      I’d like to try and help, but I’d need some more information. It may be easiest for you to call and talk it through with one of our Customer Services representatives. 586-949-4100
      Thank you and good luck!

  4. I have a total of five trains running simultaneously on separate loops, being controlled by two ZW’s and a KW. As you are aware, the ZW’s have a total of four controls each (two throttles and two variable voltage sliders). I use the throttles to run four of the trains and the the sliders to control output for lights, constant voltage plugs for switches, and accessories. I assume that if I run a common wire between the U terminals of the transformer throttles that control each of the four trains on both ZW’s, I would only need one hot bus wire to go to each loop rather than two (hot and neutral). It is my impression that a short neutral (or common) wire would only be required to one of the four loops that would suffice for all the loops because of the interconnection between the transformers on their U terminals. Could I also use this same configuration for the accessories and lights with the U terminals on the sliders? In this way I would only need one hot bus wire from each of the sliders to control lights, constant voltage accessories, and lights? But what would I connect the neutral wire to for all the lights and accessories? Perhaps another neutral bus wire that would go to one of the transformer slider’s U terminals? Since each ZW already has four common U terminals built-in, would it only be necessary to phase one of those U terminals governing the throttles to one of the U terminals governing the throttles of the other transformer, doing the same configuration for the sliders? I hope I have made myself clear on this since I am trying to avoid duplication of wires as much as possible. Thanks

  5. If phasing two CW80 for two train loop operation plus accessories do I need to connect both black on the track connectors and both black on the accessories connector or just connecting both black prones on the track connectors is enough?

  6. I plan to run two connecting loops ., each loop to a CW80. But I also want to run accessories off of the accessory connector.

    When phasing two CW80 do I need to connect both black on the track connectors and both black on the accessories connector or just connecting both black on the track connectors is enough?

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