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Thanks BigAl956 and Rob412 for your quick responses.
.
Do I need the 275 watts of power for the 50 foot distance ?? Is the new 180 watt # 37947 power pack not enough to run one train at a 50 foot distance ?? Or does the ZW got extra power and two cabs that could be used to run multiple trains in the future ??
Thanks for your responses !! John
Whether the trains run 50-feet from the transformer depends very little on how much power the transformer can put out and very much on the voltage drop in the feeders you use to connect it at that distance. If you know how much current your train will draw, you can multiply that by the feeder resistance to find out how much extra voltage your transformer will have to put out to overcome the voltage drop.
The resistance of 10 AWG wire is about 1 milliohm per foot, so 100 milliohms in the 50-plus-50 feet out and back. If your train draws 5 amperes, the drop is only 500 millivolts, which would be hardly noticeable. With 12 AWG wire at 1.6 milliohms per foot, the drop is 800 millivolts. With 14 AWG at 2.5 millivolts per foot, it's 1.25 volts. I would use 12 AWG.
A trick to reduce voltage drop is to power accessories out-of-phase with the track (from a separate transformer), but use the track as the common return for trains and accessories. The out-of-phase accessory return current will cancel some of the voltage drop caused by the train current. Another is to connect outside rails of multiple tracks together wherever they come close to each other.
The bottom line is that the transformer selection should not depend on the size of a well-wired layout.
Bob Nelson
John,
Great suggestions so far. Since you have such a large layout planned, I would recommend using a common bus wire but break your layout into isolated blocks by using the Fastrack 1 3/8" pieces to isolate the powered rail and using SPDT switches. This would allow you to use cab control to run multiple conventional locomotives. It would also allow you to add either Legacy/TMCC or DCS at a later date.
good luck with your project,
Jay in Ottawa
lionelsoni A trick to reduce voltage drop is to power accessories out-of-phase with the track (from a separate transformer), but use the track as the common return for trains and accessories. The out-of-phase accessory return current will cancel some of the voltage drop caused by the train current. Another is to connect outside rails of multiple tracks together wherever they come close to each other. The bottom line is that the transformer selection should not depend on the size of a well-wired layout.
Neat tricks! Short feeds means optimum power distribution and less cost. The out of phasing gives the accessory transformer a second duty.
Bruce
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