I am sure the subject has been long worn out, but there is one question that I just can’t seem to find an answer to. A little while back, I was checking out the display cabinet at my LHS that had the DCC products inside. I started a little conversation with an employee there and asked him a little about each system in the display case. He said that the NCE PowerCab has some problems with the spike current of some Sound equipped models. I understand that the PowerCab has a current rating of 1.5A or so, and the other system (a Digitrax Zephyr) had a rating of 2.5A. I was just wondering, what is the average spike current of sound equipped locomotives? I only have a single sound locomotive (a BLI M1b with the factory installed QSI system) but I am planning on equipping another few of my locomotives with Tsunamis as soon as I pick a DCC system. I am assuming that if I have multiple locomotives with sound on the track at the same time I should power them up separately to avoid overloading the system. If anyone can confirm this, that too will be appreciated.
I don’t know about spike current, but the QSI’s for sure have an inrush that is fairly steep, probably near 0.4 amps, but probably lasting just a fraction of a second.
With the newer locos these days, you should count on the motor and speaker system needing about 0.25 amps for the typical working session with 10-15 cars, a grade of 1-2%, and so on, nothing really demanding. So, if you would like 6 sound-equipped locos, and intend on having three running at any one time (one running free on a closed loop for effect, and two that you are actually controlling…about the limit for most of us), you will need about 2.5 amps and still have a cushion of something close to a full amp.
These are just my general recollections and gleanings…I have never done a methodology where I tested a wide arrangement of trains and conditions to test amperage draw. So, take this as a suggestion that 3 amps is lots for the majority of us. Add a couple of operators and get 10 trains storming up 3% grades, you will be happier closer to 5 amps.
Ok I will try to answer this question the best I can. I understand what you are asking and I know what is going on I just need to be able to type it out here.
The spike current is only going to last a few miliseconds but that is long enough to trip the internal breaker in the booster. Obvously the higher the booster’s amp rating the higher the spike before it trips. Now if you only have 1 sound loco you should be fine with either system. But add one or two and you may be getting into the trip or close to tripping range. Once the loco is powered up the amount of current needed to keep it all running is lower than when it first gets power, this is the spike that will trip the booster. This will occur when the booster is powered up, a loco shorts the tracks out, and possably if one gets stalled.
If you have say 5 sound locos that only require .5 amps to run at full throttle then you can run 5 on the Zyphyr system in theory (maxing the amps will start to cause problems so try to stay about 10% below max). Now if you have all 5 locos on the tracks at the same time and one shorts a frog the power will drop and all locos will be shut off momentarily. When power comes back on your current will spike (lets say .75 amps per loco) now you are asking your booster to supply 3.75 amps to start 5 locos, that is a 1.25 amp spike and that will trip the breaker in the booster over and over again until the over amp problem is corrected. If you start the system up and add locos as you go then you will avoid the problem mentioned above.
Each loco will have different current needs depending on, the loco, its condition, decoder installed, and volume of the sound. All this plays into the equation. The best thing I can advise you is to keep the sound locos to a minimum on the layout if you want lots of trains at once or buy a better system that can handle 5 amps or better. Also using power districts, and/or multiple b
If I run more than 3 sound equipped locomotives with my NCE Powercab (1.7amps) the circuit breaker trips. So 3 is the max with my system. However each sound equipped locomotive is not the same when it comes to drawing current. My proto2000 E8 is a current HOG which has more to do with its engine than anything else. So perhaps I could run 4 sound units, but without including the proto.
I run a Lenz LZV100 (5a) with an RRamp meter wired to measure all track current drains. My roster of locomotives include P2K (QSI), BLI(QSI) and Soundtrax Tsunami. I have run as many as 6 locomotives at one time with sound and pulling 8 - 10 cars. Max current drain I have ever had on my layout is under 2 amps. The largest single current drain on my pike is passenger cars with light bulbs. I also run 10 Tortoise Hare components driven by the DCC bus as well.
Only time I have ever seen current inrush issues is on the program track which is why I purchased a booster.
Ive seen Digitrax Zephyrs run a railroad by it’s lonesome. A 5 amp Super Chief pretty much owns all.
Me? Heh. I have too many amps. With a 2012 power supply I can have one 8 amp SC which I use now and a second connection free for another 8 amp booster if needed.
Will I ever use those extra amps no. It is my opinion that 5 amps is plenty.
Now if I got into O scale and fired that up… I can do it.
I dont even think about program track problems as long as the rails are clean and the decoder is good.
It’s not just the DCC system and boosters you have, it’s also the power supply you use to drive them. I’ve got a Lenz 5-amp system, but I was driving it with an old train transformer. It worked fine until that Hudson with a QSI decoder put me into overload. The transformer just didn’t have enough, and I started seeing voltage drops. The transformer is so old that it has no circuit breaker on it (unless there’s one inside I don’t know about) so it just slowly degraded as more demand was put on it.
I bought a “real” supply from NCE and my problems went away.
I’ve run as many as 8 locos on my Zephyr, 2 were PCM with Loksound, one was a BLI with QSI, and one had a Sountdtraxx. The other 4 were P2K and Stewart with no sound, just motor decoders. I even deliberately shorted the track to see if there was a problem with inrush current, didn’t seem to have any problem recovering after removing the short. The current inrush issues is mostly confined to QSI decoders which have a large capacitor to prevent sound dropouts for minor power interruptions. The level of a potential inrush is near infinite, for a VERY short time - a discharged capacitor with no resistor limiting its charging current is a dead short until it charges. Any resistor value plus the capacitor’s value determines the duration of the inrush as wella s its level. A larger resistor lowers the current but make it take longer to charge the capacitor. It is entirely possible to build a circuit that limits the charge current yet allows the full power to be delivered to the circuit when power is interrupted, unfortunately the circuit used in the QSI decoders is not this one.
Not every system has problems with the QSI inrush, unless you have many QSI locos on the track at the same time. Depending on the presence of any downstream short protection (circuit breakers like Tony’s PowerShields or other similar devices), you can handle this without interrupting the restof the layout.
Thanks a lot for your input! It was really helpful. Although I do not plan to install sound decoders in all of my locomotives (at least not right away… far too expensive for me!) I think I will go with the Digitrax Zephyr. Although I do not plan to run more than three trains at a time (perhaps one doubleheader) I really like the Z’s ability to use smooth powerpacks as a throttle. Since this saves another 100 dollars for me to run multiple trains at once with multiple operators, I like the Zephyr even more. When I decide to upgrade some other locomotives to sound I will add a few UT4’s or perhaps a UT400, but for now, I just want to run trains. Thanks again for all the help!