I am trying to understand the concept of wattage so I have thought of a hypothetical question. Suppose a 50 watt MTH brick and a 100 watt MTH brick were each connected to identical Z controllers which in turn were connected to identical loops of track having identical trains on them. ( I am trying to limit the number of variables-remember, this is hypothetical.) Now suppose we adjust each controller so that each train is traveling at exactly the same speed (same number of seconds per lap, for example). Would each controller be set at the same calibration mark under these circumstances? What exactly would be different and how would one measure it? I would appreciate any help you can give me to increase my understanding.
Try this, in theory,
P=E I, Power in (Watts) equal Electromotive Force (in Volts) times Amps (expressed as "I" ). In toy train motors, Voltage controls Speed, Amps is the Load or work being done.
If a 50 Watt transformer is putting out 18 volts it should (without allowing for loss) be good for about 2.7 Amps. That's enought to run small sets. A 100 Watt transformer should output about 5.5 Amps and would be needed for larger engines and sets.
If both transformers in your test were calibrated to put out 18 volts at 100% of dial setting and the draw was less than 2.7 Amps they should run the same. If you exceed the rating of that 50 Watt transformer, by drawing over the 2.7 Amps, the Voltage output should drop (the train slows) with the amperage climbing until the Overload trips.
Don U. TCA 73-5735
DMUinCT If both transformers in your test were calibrated to put out 18 volts at 100% of dial setting and the draw was less than 2.7 Amps they should run the same...
If both transformers in your test were calibrated to put out 18 volts at 100% of dial setting and the draw was less than 2.7 Amps they should run the same...
That depends on the internal resistance of each of the "bricks". As you near the 2.7 amps, you are demanding more from the small brick, which will be evident in a higher throttle setting than the other train that is not taxing it's supply anywhere near it's output capability. Depending on the internal resistances, this difference could be great or minimal.
Rob
Huh? Once again for us electrically challenged folks who only know they've done wrong when a fuse blows! lol
Becky
Trains, trains, wonderful trains. The more you get, the more you toot!
Penny I'm with you I would think if you had 2 bricks going to one transformer one would be giving 100 watts the other 50 that the out put to both tracks would be 75 watts each. unless where one brick plugs in only controls one side of the transformer and the other brick would control the other side. Then I could see one side being only 50 watts and the other 100 watts.
Now I'm no electrical person either. But I thought the power went in joined then was separated by the controls.
As in I've always heard when you add 2 180 bricks to a ZW you had 360 watts of power and if you do 4 you have 720 watts. now does that mean if I only have 2 trains running there getting 360 each well what if I hooked 2 135's and 2 180's does that mean if I use the correct 2 hookups that I have 270 on one side and 360 on the other I'm starting to confuse myself here but I think you see where I took this and didn't do so to be smarty about it just to ask the question the original person asked another way.
Life's hard, even harder if your stupid John Wayne
http://rtssite.shutterfly.com/
rtraincollector'
The OP is using MTH bricks with Z-Controllers, the Z-Controller is a single throttle controller, each with a seperate power brick. There is no mingling or combining the output of the bricks in this case, like there would be in the re-issue of the ZW with seperate power bricks. These are two completely seperate controllers, similiar to using two individual CW-80s, or any other single throttle transformers.
Doug
May your flanges always stay BETWEEN the rails
Don and Rob: Thank you very much for your input. The P=E I formula helps explain a lot and the fact that there are internal resistances lets me know there are limitations on the accuracy of the formula. Thank you also Doug for clarifying the topic. I am supposing two entirely separate layouts identical in every way except for the wattage of the power input.
So what's a "VA"? And why do "VA" transformers seem to make my proto 2 engines lose their minds? Similarly, why do DC VA transformers like the MRC Tech 4 220 go into overload when I try to run my Lionel MPC 8008 Chessie set?
I really don't understand electricity, but I'm trying! lol
"VA" is "volt-ampere", which is the same unit as a watt, but is used to indicate that it is apparent power rather than real power which is being measured in an AC circuit. Apparent power is the sum of the real power and the "reactive" power, which does no work. The apparent power is the product of the RMS voltage and the RMS current, without any consideration of any phase shift between them. When the voltage and current are in phase, the apparent power is equal to the real power and there is no reactive power. When the voltage and current are 90 degrees out of phase, the apparent power is equal to the reactive power and there is no real power. The apparent power in a DC circuit is equal to the apparent power. That is, there is no reactive power in a DC circuit.
Bob Nelson
Becky,
I REALLY wish Lonelsoni would find this thread, but I will try. VA is essentially the same as watts is my understanding, I believe that there may be a small difference that I don't understand.
VA stands for Volt Amps, if your transformer is rated for 18 volts @ 5 amps then it has a VA rating of 90. The same transformer MAY be able to supply say 7 amps @ 12 volts and still be within it's range, as it is only supplying 84 VA, of it's 90 VA capacity. Imay not be entirely correct, but that is my best understanding, and I WELCOME anyone to correct me if I am wrong in any way about this.
If your MRC 220 goes into overload, DO NOT try to run that locomotive with that transformer, until someone who is familiar with BOTH your locomotive and that POWERPACK. I am NOT familiar with the Lionel Chessie 8008 set, and I do not know if it has an AC ONLY motor, UNIVERSAL motor or a DC ONLY motor, some Lionel trains were made with different motors, a universal motor will run on either AC or DC power, a DC motor can be damaged by feeding it AC power. MOST BUT NOT ALL, Lionel trains will run on AC power, Lionel did produce some DC ONLY sets as well.
The MRC 220 is a DC POWERPACK. Technicnally a TRANSFORMER just alters AC Voltage, It transforms the 120 Volt AC from your household outlet to a much more train friendly 18-20 Volts (max). A Powerpack, includes a TRANSFORMER to lower the Voltage, but also RECTIFIES the power from AC to DC.
Looks Like Lionelsoni and I were typing at the same time with Bob hitting "Post" before me.
Bob, PLEASE feel free to correct anything that I have posted incorrectly.
Were your ears burning? is that why you showed up just now?
OK, remember I'm completely illiterate when it comes to electricity, so I went and wrote down some numbers.
First of all, the MRC Tech 4 is a 260, not a 220 as I previously named it. (Don't know if that makes a difference, but there we have it.) It says 23VDC, 18.5VAC, Total 20VA. I bought it at a hobby shop, now closed, because I was told it was strong enough for G-Scale. Which it wasn't. So I replaced it with an Aristo-Craft Train Pack 7000, 12 VAC 1 Amp, 21/16 VDC 3 Amp, 60 VA Total. Overload protection is switchable between 16V or 21V circuits. So, how does the 7000 have a higher VA at 21 VDC when the MRC has the higher VDC of 23? Is the Amp rating different?
Over on the O-gauge side, my weenie little Life-Like 20VAC 18VDC 6VA HO starter set pack pushes the 8008 with none of the problems the MRC 260 has. The 8008 is a 4-4-2 with a 2036 style diecast shell. Looking up from the bottom you see the standard nylon and brass back end of a typical DC motor sticking out sideways from the post-war style motor fame. This is the cheaper version of the Chessie Berkshire but it looks fine pulling the steam special cars. It has the sound wheel tender and both the tender and loco are blue with the Chessie logo on the tender sides and a yellow stripe on the engine's running boards. It's a very nice engine, but I'm not sure when or whether it was catalogued. O'Brien's Collecting Toy Trains Volume 5 doesn't mention this engine at all.
For this one DC engine, I use an old Leviton 125V DPDT knife to switch between the Life-Like pack and a Lionel Type R, which is my usual controller. Of course, I also had to install a sliding switch under the roof of my gateman to keep both it and a wig-wag signal from freaking out when I run DC.
Is the MRC overload sensor just too sensitive? Maybe I just have a bad MRC 260?
Hi Becky,
From the researching I did, it seems that your 8008 is indeed a DC locomotive, I would think that the MRC 260 should have been adequate to at least get some response from your 8008, even if not setting any new land speed records for a wheeled vehecile on rails. The 260 would seem a bit weak for "G" scale to me, when I dabbled in Large scale, I used MRC 6200 model powerpacks, and IIRC, those had a VA rating of 60 VA. I don't know what to tell you about your 260, if it is bad or not.
Good luck,
I run "G" gauge (collect old "O" gauge).
To operate any brand of "G Gauge" locomotives, and be safe, use a 18 to 22 volt, DC (Direct Current) power supply putting out at least 10 Amps. Most "G" locomotives will draw 2 or 3 Amps plus car load, lights, and sound. A few locomotives, notably MTH brand, can run on ether AC or DC. On the other hand, if you accidently put AC to DC Only locomotive it will quickly destroy itself as it attempts to reverse at 60 times a second.
You will find two types of G Gauge power packs. The "Transformer Type" works fine, it is low in cost, but will drop the voltage as current draw (Amps) rises. It should have a fuse or Circuit Breaker.
The "Switching Power Supply" produces the voltage with "solid state circuit boards", no transformer. This type will maintain the set output voltage under all loads until the maximum output in Amps is reached. At this time it will "instantly" shut down. This type of protection, known as a "Crowbar Circuit", also protects your train electronics from sudden shorts or derailments.
Lewis Polk's Aristo-Craft sell several of both types under the "Crest" name. I use the CRE-55465 that can be switched to put out 22 volts DC at 13 Amps (G Gauge) or 13.8 volt DC at 20 Amps (HO Gauge). I feed the output of the power supply to ether an "MTH Track Interface Unit" or a "Aristo Train Engineer" to provide radio control.
Lionel was originally built around AC control. In most cases, in the older locomotives, the "E Unit" and "Whistle Controller" will miss-operate on a DC power supply.
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