Calculating transformer size for layout size

[eZAK]

QUOTE: Originally posted by FJ and G

That's good for ole eZak!

I can't see no use in going out and slamming down 400 clams for a ZW or Z4K with fancy handles and all if you really don't need the power.

I can think of better things to do w/my $$$ like get my shotup TIU back in shape and buy some bones for the hound.

Dave, You can get industrial transformers at electrical supply houses for alot less.
They come in various sizes.
I picked up a 1.5 kva for 80 clams[;)] for my cousins layout.
If you have a TIU or TPC's your in .

[Anonymous]

Hello All: Pat is right about purchasing at supply houses, but I would only use them for light's & accessories, also make sure they are grounded(use a three prong cord on the 110 volt side & install a fuse or breaker on the secondary side (low Volt side). I would not use them for track power because of the electronics in the engine's & Loco's of today. The manufacture's power supply are regulated with a lot of diode's & resistor's to keep the voltage clean for today's technology. Also remember the KISS rule, Keep It Simple Stupid. Kind Regard's to All Steve

[eZAK]

Steve,
That is why I said to use a TIU or TPC for track control.
You would also need a AIU or APC for acc. control.

Many older transformers are still widely used today, all without electronics.[:)]

[FJ and G]

Pat,

Can "industrial transformers" be used in place of transformers? In my example, could they substitute for Z750s under DCS control?

(I bet the toy train companies don't like to hear your suggestion!)

[Anonymous]

Whatever happened to the "Max?" This morning I was looking through the only CTT I own, February '99, and in the product reviews on page 118, they reviewed a 600 watt train transformer that even had a program function for MTH. MSRP $799, but they used it to run ten trains, and the breaker finally popped at 15 v. and 16 a.

[eZAK]

Yes they can.

You just have to match one with your needs.

They come in various sizes stated in kva, i.e. 0.1kva(aprox.100 watts) or 1.0 kva(1000w)
You would also want to make sure you have a 120v pri, & a 18v or 20v sec.(there are also multi tap sec. which will give more freedom)

They come enclosed in a metal case and require wiring a 3 prong male cord end to it (H-N & case Ground) Simple!

Now hook up your sec. to your TIU or TPC. It is also advisable to add a $0.49 Transient Voltage Suppressor accross all sec. outputs.(hot to common)

[eZAK]

Doug J.,

That probaly did not get UL approved for a toy trans.

[lionelsoni]

In any situation where you would use a traditional train transformer to supply the fixed track voltage for a modern control scheme, you can perfectly well use a simple "industrial" transformer.

The reason for putting the circuit breaker after the secondary on a traditional train transformer is that, at low voltage settings, an excessively high secondary current does not necessarily cause an unusually high primary current. This is not the case for a fixed transformer. So it would be slightly safer to put the fuse or circuit breaker for a fixed transformer before the primary. If you were also to connect one side of the secondary to the equipment ground, the fuse would then protect you from any insulation failure that would put a dangerous voltage on the secondary.

[FJ and G]

Thanks, Pat,

Another reason to stay away from the pricey bricks!

Besides running the trains, how would you step it down for low voltage DC for some of the accessories?

[lionelsoni]

There are two simple ways to get (unregulated) dc:

Use a transformer with a center-tapped secondary. The center tap is one of the output terminals. Connect the anodes of two rectifier diodes to the ends of the secondary and connect the cathodes together. The cathodes are the positive terminal. (Reverse the diodes to reverse the polarity of the output.) The average voltage will be about 90 percent of the rms voltage of the half-winding, minus about .7 volts. The rms voltage will equal the rms voltage of the half-winding, minus about .7 volts.

Use a simple secondary into the ~ terminals of a bridge rectifier. The + and - terminals are the output. The average voltage will be about 90 percent of the rms voltage of the winding, minus about 1.5 volts. The rms voltage will equal the rms voltage of the total winding, minus about 1.5 volts.

If you want filtered dc, put an electrolytic capacitor across the output. The peak-to-peak ripple voltage will be approximately 8333 times the current drawn, in amperes, divided by the capacitance in microfarads. The output voltage will be about 141 percent of the half-winding or winding, respectively, minus about .7 or 1.5 volts, respectively. The capacitor's working-voltage rating should be at least as high as the filtered output voltage.

Notice that the dc output of the center-tapped transformer and its unrectified ac can share a common terminal, which is not possible with the bridge rectifier.

[3railguy]

I came up with 4 watts per square foot for an average outfitted layout with modern era trains and lighted accessorys which are more energy efficient than postwar. On the other extreme, for a densely outfitted postwar layout, I came up with 7 watts per square foot.

[FJ and G]

thanks for your great advice guys,

I've gotta run to the dentist in 10 minutes so may have to read the other posts when I get home tonight after running the hound.

[lionelsoni]

Dave, it seems that your appointment might be close to the ideal time to visit the dentist, that is, 2:30.

(tooth-hurty)

(sorry)

[FJ and G]

scratch b.

the 2 rail and 1 wire is the end result. I've still got more wire to string as it is under construction.

I'll keep you guys apprised of the progress, hopefully not too ad nauseum!