Need Some Electrical Expertice

[nachoman]

You can always put a smaller fuse downstream of a 10A supply. The danger is, if you have a short, 10A is enough to do a fair amount of damage. If you put a 5A fuse downstream of there, any current draw over 5A will blow the fuse, protecting you remaining circuitry from further damage. Think of it like the electrical system in your car. Let's say your alternator supplies 50 amps when the car is running. And let's say you have an accessory that draws 3 amps. The manufacturer designs a 5 amp fuse for that accessory's circuit. That way, if there is a short circuit, no more than 5 amps of current can flow through that wire until the fuse blows. If there was no fuse, the full 50amps would try to run through that wire until it melted the wiring harness and potentially caused a fire. You don't want the same thing to happen to your trains. If a DCC manufacturer says 5A max, that means the electronics can handle no more than 5A. If there is no fuse in the system and you forget to take one of those track gauges of the rails...