Hi,
I was reading about the Digitrax 20 amp power supply and that it will provide full power for 4 - 5 amp "districts". When I convert to DCC (on the layout rebuild), having 4 districts seemed to be right for my plan - and therefore this might be the best power supply to get as it will "meet my needs".
My question is this - The 20 amp supply puts out 20 amps at a reduced voltage (15 or so V?), but how many amps of 110 V does it consume when being used?
Thanks!
Mobilman44
ENJOY !
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
I'm sure someone will reply with the exact figure, but I'll get you close.
12V x 20amps= 240watts
240watts/ 120volts = 2amps
It will draw about two amps. That's if the supply is working at its full output of 20 amps which most times it won't be.
Martin Myers
That assumes it's 100% efficient, which no power supply is. I believe it's a switchign power supply simialr to what's in most computers, although not quiet as much current. Decent ones are 80% efficient, so figure 2.5-3 amps draw on the AC side if fully loaded. No need to panic that you have to install a dedicated circuit to run a 20 amp power supply. When you reduce the voltage you increase the current, proportionally less the losses in the circuit (usually given off as heat).
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You folks are just great! When I posted the question I should have remembered my physics data on conversions.
I continue to design the "new and improved" layout, and when that is settled I'll be able to work up the Digitrax system shopping list. Of course I will review that with you all first - as I want to do it right the first time!
ENJOY,
I will presume you are speaking about the Digitrax PS 2012.
I own one.Ratings:
18.0 Volts HO Scale setting gives you 15 Amps not to be exceeded.
13.8 Volts in N scale not to exceed 20 Amps.
G scale 23.0 volts not to exceed 12 Amps.
You are not permitted to use more than 15 amps when voltage is 18.0V and you cannot use more than 12 Amps when Voltage is at 23.0
That is directly from the sticker on top of the unit.
Also.
You get two outputs of about 10 amps each.
Your HOUSE Outlet at the wall 110 V socket USUALLY is about 15 amps max UNLESS you have a SPECIAL T shaped socket input that will provide you 20 amps.
I use a Digitrax PS 515 5 amp supply to drive a DCS 200 Command Station and it is perfectly adequate.
What the power supply CAN do is drive TWO 8 amp super chiefs or one 8 amp chief and one 5 amp Empire builder booster. And that is about as much as you want to pull from your house anyhow.
To put your thinking of amps into perspective, light breaker boards in homes behind the meter generally are rated for no more than 100 total amps for the entire home at once.
Chew on that for a bit.
Oh ya. Dont go running out with a wad of money for the monster. I converted to DCC last night and my 2012 refused to generate 9 volts necessary for the Chief to stay booted up. (On) Im thinking either I have a failure of the power supply itself (Very similar to what I have on my computers that I build) or I have human error with the two wires between the command station and the outputs.
Start off with the 5 amp PS515 and you will not be sorry. Cheaper too. Just be sure to set it on a fireproof surface as it will get warm after a time.
And you totally disregarded what was said previously. A power supply that puts out 20 amps at a low voltage DOES NOT draw 20 amps from your 110 volt AC outlet. If it does, it is VERY VERY broken.
Keeping it simple, assume we have 120VAC at the outlet. The output voltage of our power supply is 12 volts. It it's 100% efficient, when the power supply ir outputing 12 volts at 10 amps, it's drawing only 1 amp at 120 volts.
In reality, 80% efficiency is a goot power supply, so it would be drawing 1.25 amps at 120 volts to supply 10 amps at 12 volts.
If this were not the case you'd need a dedicated line from the pole just to run a computer - 20 amps at 12 volts, 35 amps at 5 volts, plus the various other voltages. In reality your computer is drawing only a couple of amps from the 120 volt AC plug to provide all that at low voltages.
As for costs, individual power supplies will be cheaper. If you're buying from a dealer who has both NCE and Digitrax - buy the NCE P515, it has a $15 lower list price and it's the same power supply.