Transformers and their Power!!

[lionel2]

Okay,  I have (3) Z's, (1) ZW and (1) KW.  In total I have 18 variable post to work with.  I will be running 4 trains at one time on seperate variable posts. 

On KW....A Side- (6) 022 switches for fixed voltage plugs.  B Side- (6) 022 switches for fixed voltage plugs.

On ZW...A Side- 364 log Loader.  B Side- 252, 151, 154 accessories.  C Side- 456 Coal Ramp  D Side- 497 Coaling Station.

Z #1...A side- 342 & 345 culvert loader & unloader.  B side- 362 barrel loader & 352 icing station.  C side- Train Line #2 & 3656 cattle car.  D side- Train Line #1.

Z #2...A side- 397 coal loader & 264 Forklift loader.  B side- 3356 horse car.  C side- Train Line #4.  D side- Train Line #3.

Z #3...A side- 445 switch tower & 45N gateman.  B side- 138 water tower & 356 freight station.  C side- 164 Log elevator loader & 415 diesel fueling station.  D side- 97 coal elevator loader & 464 Lumber mill.

Small 100 Watt transformer...Use for all my #71 Lamp Posts, (8) of them.

 Does this wiring scheme seem like it is good enough?  And will not overload my transformers? I split up all the accessories and 022 switches among the transformers.  And will use a seperate small transformer for my lights for houses and 71 lamp posts.  I will be using 12 AWG for power buses, 14 AWG for track power, and 20 AWG for Accessories and 022 switch fixed voltage plugs.  I hope this all seems like it will work.  Let me know if maybe I need another Z or KW or whatever.  But, I think I have more than enough power, because I never run more than 1 accessory at one time and maybe 2 at most locos at one time.  But, the 022 switches are on at all time.  Thanks.

[ben10ben]

 12 O22 switches on the KW should be no problem.

Everything else looks good-most of the things that you mentioned will only be on for an instant, or at best for a relatively short time, so their load is minimal.

Just as a side note, every one of the transformers you've mentioned can supply their full capacity through one of the terminals. Thus, you don't need to split the O22s between two terminals, for example, unless you want to be able to separately control the power to each one.

[phillyreading]

Lights on the 022 switches may use a little power but having six to eight 022 switches should not be a problem as you most likely only throw one switch at a time, the 022 switches can handle the higher voltage, the lens cover over the light bulb may melt but the switch itself should be good to go.

20 gauge wire is a bit small in my opion even for accessories, I would use 18 gauge wire. 12 gauge wire is good but a little bit of overkill(with costs) unless you have a very large layout(35 feet or more of wire) with a long run for feeder wires.

Lee F.

[mdainsd]

 on my 022 i have interupped the bulb circuit and added a simple 1n4001 diode which effectively cuts the votlage to the bulb in half. I then run the switch power through the contant voltage plug and supply them from a dedicated 28V transformer. the switches snap smartly on 28v the lamp thinks it has 14v and everyone is happy. I dont use the illuminated switch controllers so I have no issue with bulbs there.

[lionel2]

So you are saying that if I put all (12) 022 switches on the A side of the KW I will be okay??  That leaves side B open for some block signals I would like to hook up.  Will hooking up say (4) 153 block signals be okay when I have (12) 022 switches on side A??  But, leave the fixed voltage tap unused.  Thanks.

[lionel2]

So you think maybe, because I have 500 feet of 14 AWG wiring, that I can use that for my accessories and my 022 switches??  I have no 16 or 18 AWG.  I have only 12, 14, and 20 AWG wiring.  You think maybe I should invest in some 18 AWG wiring for just my 022 switches and accessories??  My layout is 12x12.  I have not very long runs of wiring, so wire wont cost me much.  Now, I think the 022 switches have small 18V lamps, some are bayonet, some screw in, is that true they are 18V lamps and should not exceed 18V on the transformer, or else I will melt the lanterns.  Thanks.

[mdainsd]

lionel2

So you are saying that if I put all (12) 022 switches on the A side of the KW I will be okay??  That leaves side B open for some block signals I would like to hook up.  Will hooking up say (4) 153 block signals be okay when I have (12) 022 switches on side A??  But, leave the fixed voltage tap unused.  Thanks.

 

 

Put all the switches on one tap. the load is only 24 lamps, 12 in the switches and 12 more on the controllers if you are using that type. Those lamps are about 2 watts each if memory serves me. I bought some bare solid conductor #12 ground wire at the HD. It is stapled to the bottom of the layout and follows the track plan. Each switch has a #14 twisted insulated wire attached to the constant voltage plug that then goes through a hole in the layout and solders direct to the #12 buss.

[lionel2]

So bottom line is to use 12 AWG for power buses, and 14 AWG for 022 switch fixed voltage plugs.  I have some of that 12 AWG, I will use that for power buses. I also have 14 AWG, might wanna use that for my 022 switches, I have lots of it.  And I am gonna buy some colored electrical tape, 3 or 4 different colors, so everything is color coded and easy to work with.  Its only $3.54 a roll of 35 yards each color.  Thanks.

[lionelsoni]

Add up the currents drawn by the loads on each proposed circuit.  Use wire for that circuit heavy enough to carry that total current.  If there is any chance of a fault (like a derailment) on the circuit, use wire able to carry the transformer's circuit-breaker rating instead.

Add up the currents of all the circuits proposed to be connected to any one transformer.  That total current should be less than the circuit-breaker rating of the transformer (15 amperes for Z, 10 amperes for KW).  Add up the power delivered to all the same circuits.  Each circuit's power is the circuit current multiplied by the voltage at which you are going to set the circuit.  That total power should be no more than about 70 percent of the input power rating for the transformer (about 180 watts for Z, 140 watts for KW).

Putting a diode in series with a lamp drops the voltage only about 30 percent, not 50 percent.  So 28 volts is reduced to 20 volts, not 14.  An ordinary AC voltmeter will tell you that it is 14 volts; but that is because the meter is accurate only for measuring sinewaves, which is not the waveform that is left after you put in the diode.  You would have to start with 20 volts to get 14 after adding the diode.

[lionel2]

How many amperes do my trains use up??  I have single & double motor locomotives.  And all those accessories I listed.  I have 10 locomotives on the track at one time, but only 2 at most running at one time.  Man,  think of all the light bulbs that are lit when I juice up the throttles, must be like 50 light bulbs that are lit, 24 just for the 022 switches, 16 for all the locomotives.  Thats 40 right there.  Thanks.

[lionelsoni]

I generally assume that a train draws about 5 amperes.  Some draw more; but that's a fairly conservative number I think.  You could look up all the lamps individually; but I think that 1/5 ampere per lamp is a reasonable guess.  As with the trains, some will draw more, some less.  You don't need to count anything for the switch machines other than the lamps in them--they draw current so briefly that it doesn't matter.

[lionelsoni]

Mark ("mainsd") posted this on another thread, I think by mistake:

"Lionelsoni. I must be missing something in my old age. if one put a scope on a transformer and recorded 28Vpp, then inserted a diode n series. i wouldh have thought the resulting wave for would only be the portion of the sine wave that was forward biased of the diode, so 14-.7V forward drop. Help me out here please."

If you saw only 28 volts peak-to-peak, you would have only 10 volts RMS, which is the usual way AC voltage is measured.  But let's assume that we are talking about 28 volts RMS, which is what I suspect that your transformer is putting out.

"RMS" stands for "root-mean-square", which means the square-root of the average over time of the square of the voltage.  While this way of measuring voltage may seem overly complicated, it has the advantage that it is directly comparable to DC voltage for resistive loads.  So, if you have a lamp rated for 120 volts, you will get the same light out of it whether you connect it to 120 volts DC or to 120 volts AC RMS.  The 120 volts in your house is RMS voltage.

The peak voltage (not the peak-to-peak voltage) is the RMS voltage times the square-root of two.  So the peak of 120 volts RMS is actually 170 volts.  The voltage waveform is sometimes below 120 volts and sometimes above it.  The peak of your 28 volts RMS is about 40 volts.

If you look at the square of your AC waveform, it looks like a 120 hertz (twice the line frequency) sinewave, shifted so that the negative peaks are at zero and the positive peaks are at 1568 volts-squared.  The average (the "mean" of the "square" in "RMS") is 784 volts-squared.  And the square-root of that (the "root" of the "mean" of the "square") is--surprise!--28 volts.

When you put the diode in series, you chop out half of the 120-hertz squared waveform, every other cycle of the 120-hertz sinewave, so the mean of the square goes down by half, from 784 volts-squared to 392 volts-squared.  The square-root of that is 19.8 volts, close enough to 20.

(Note that I have ignored the forward drop of the diode, which introduces a very slight additional voltage drop.)

An ordinary AC voltmeter doesn't actually measure RMS voltage.  It measures the average of the absolute value of the voltage.  If you assume that you are always measuring sinewaves, you can calibrate such a meter to show the RMS voltage, because the average of the absolute value is always proportional to the RMS voltage for a sinewave, actually very close to 90 percent of it.  But when you chop out every other half-cycle with a diode, the average of the absolute value goes down by half, while the RMS voltage drops only 30 percent as we have seen.  So, if you happened to measure your lamp voltage, you would have been misled, because the meter was not designed to measure accurately the half-wave voltage that you created with the diode.

 

[mdainsd]

Thank you! A lot to digest but I see how that works, I appreciate your time to spell it out.

[ben10ben]

 Bob, I had never really considered that before, however it make sense.

 I just ran through some quick calculations, and it seems as though the answer I'm arriving at is that the RMS voltage of half-wave AC(assuming an ideal diode) should be 1/2 the peak voltage. 

This came from taking the square root of the integral of sin squared from 0 to pi, divided by 2pi. 

Would this be the correct answer?

Thanks

[ben10ben]

.

[lionelsoni]

Correct--both times!

[ben10ben]

 Oops, sorry about the double post.

Thanks again!

[lionel2]

So, a train draws 5 amperes and each lamp draws 1/5 of an ampere.  So I think I am looking at just 5 amperes drawn on my KW, which can handle humm 10 Amperes. And it was 15 amperes for a Z and ZW.  My one Z draws nothing because it has all accessories hooked up to it and those all have snap or fast action, but then again some of them have light bulbs in them, so at best maybe 2 amperes on my first Z.  On my second Z, I have (2) 2 trains hooked up to it, so thats 10 amperes right there, and a few snap fast action accessories, and this Z is not the main line, just a gang car and 400/404 budd cars, so I would say 12 amperes on this Z.  My third Z, main line Z, has 10 bulbs on the passenger train, 8 bulbs on the train line inside the main line or second loop of track.  So, I would say Z#3 draws about 14 amperes at best.  My ZW draws about 10 amperes i would say, lots of light bulbs.

KW- 5 Amperes

ZW- 10 Amperes

Z#1- 2 Amperes

Z#2- 12 Amperes

Z#3- 14 Amperes

Total among all (5) transformers is 33 Amperes.  Now how many Amperes can a standard 15 Amp outlet handle??  I am guessing its 15 Amperes before the fuse blows.  But, that would only happen if I had all my trains running at one time, all accessories going at one time, and all bulbs lit at one time.  Thanks.

[ben10ben]

Are you concerned about tripping a household breaker?

If so, it won't happen. Amps on the output side of the transformer don't transfer directly to the input side. Figure the total input amps being aproximately 1/6 the total output amps. Thus, 33 amps on the output would only draw about 5 1/2 amps at the wall-nowhere near the limit. 

[traindaddy1]

Well, after reading and re-reading the information on this thread, I have come to realize that the depth of my knowledge about trains is very shallow.  All this time, I've just turned on the switch, powered on the old ZW and "played" with my trains.   Thanks for the schooling.

 

[lionel2]

I just wanted to know that I was playing with my trains the safe way.  So, my trains would last longer and run smoother.  Hope my tread helps everyone with all this.  Thanks.

[lionelsoni]

The current into the transformer at 120 volts is not the same as the current out at less than 24 volts.  They are in the inverse ratio of the voltages.  For example, 15 amperes out at 12 volts is only 1.5 amperes in at 120 volts.  (This neglects the relatively small magnetizing current that the transformer draws all the time.)

An ideal transformer takes in the same amount of power that it puts out; and the power is the product of the current and the voltage.  So 15 amperes times 12 volts equals 180 watts; and 1.5 amperes times 120 volts is also 180 watts.  Your outlet can easily handle all your transformers.

[lionel2]

Ok, got it.  Thanks.