I was reading in a book that the total power pack output is figured by dividing the VA by 12. On my MRC Tech II 2500 that is 16VA. This would mean that my peak output is 1.33A. A doubleheaded train alone would pull 3A. I have used this pack to doublehead before with no problems. What am I missing? Surely I would have enough power to handle a single engine and six coaches with lighting that ammounted to .06A per car. I think the advertisement for these packs bragged about pulling a very long consist. Perhaps I misread somewhere.
First of all, I'm no electronics expert. If your pack is indeed 16VA, you would have 1.33 amp at 12v. However, depending on where the breaker trips, you may have, for instance, 8v at 2amp. The thing that caught my eye was your statement that a doubleheaded set would draw 3 amp. Are you running Hobbytown's or really old Athearn's? My 20 year old Athearns draw about 1 amp each. A three unit set of proto 2000 Fa's draws 1 amp. Perhaps you can run your doubleheader because it is drawing less than you thought, or perhaps you are not being able to run at full voltage. Gary
I've got a voltmeter and an ammeter on my power supply, so I can watch what's happening on the track. I think you may typically see current draws on the order of 1/2 or 3/4 of an amp per engine. My newer Athearns draw 0.7 amps under full load, and I've weighted the engines down for better traction. On the flats they don't pull more than 0.5 amps once things get up and running. My Genesis, Kato, and P2K all draw a little less. One advantage of having an ammeter on the power supply is you can tell when the track is getting dirty. The current draw starts to bounce up and down when the engine hits a spot of dirt. As for my power pack, I can pull 4 ngines, but not 5. Trying to pull five under full load will trip out the power supply. I'm toying with the idea of building my own power supply. It would cost me around $100 to build a "bullet-proof" unit that could supply around 20 amps with crowbar protection and current foldback for limiting the current on short circuits. Mark. [ 06 September 2001: Message edited by: Mark_Athay ]</p>
Electrical ratings are a huge grey area unless you know exactly what all the conditions are - which is why designers always add a bit for luck! Heat is what limits most electrical devices power rating and most ratings are given for worst case (e.g. hot room/hot day). As suggested in the other posts, you probably aren't pulling the amount of power you think, but even if you are the power pack will probably supply it for a considerable time before it eventually gets too hot and gives up.
Ok folks here we go. I'm not an electronics expert, however I am an electrician. I never liked VOLT AMPEARS. It's a fancy word that I feel people use when they have no blumen idea what there saying! Volts and Amps are what we are really looking for. Look at this way, volts is more of the amount of flow of electric. Where as Amps is the amount of work that can be done. Next Volts or Voltage is a constant (usually) from its source. Where as Amps tend to fluctuate or change. A good example is water. When we open a faucet water runs at a cretin pace, ( Voltage ). If we put that water to work or open to many faucets then water pressure goes down ( kind of like a short or to much of a drain, to many lights on exec. ) Say we put a water wheel on the faucet, then we turn it on. The amount of water pressure goes down. A perfect answer to this is when I'm in the shower and the lady ( term I use loosely in this case ) flushes her toilet because she hers the water running upstairs. Suddenly the preslected balance of comfort between cold and warm water is disrupted, and the flow of water goes down. Which in turn makes me disrupt the calm quite morning with a " WHO THE H*^^ IS DRAWING WATER ! ". In a nut shell Volts / Voltage = amount of flow ( usually a constant, except in model railroading, we change this to change the speed of the train ). Amps = amount of work that can be done. In most case for us model railroaders this means the amount of locomotives that we can run at one time. In the past I have built my own power supplies. Using transformers from Radio Shack ( RAT SHACK ) at 12.5 volts and 2.5 Amps. For along time I used this configuration but taking advantage of the 2 coils in the transformer I made a HI and LOW switch. At the time I had a layout with really STEEP GRADES. So when I needed more locomotives, I put the throttle in HIGH ( going from 12.5 Volts at 1.5 Amps to 24 Volts and 3 Amps. ) This made it possible to run 4 - 6 Athearn's and I had a rocket train if I was not careful. As soon as I made the grade I'd lower the setting back to LOW as the increased voltage would hurt the locomotives if used for to long. I hope this is a help!
