The psx rules out conventional running. I believe I recall it needs a constant voltage over 12v.
John H, Your jumper wire couldn't hold 5a, so should have had a lower rated thermal breaker for the wire to be used. Or your breaker was bad.
Not burning the jumper with the new breaker is a decent show of ability, but yet kinda of misleading as compared example as example A is flawed making thermal seem unsafe; the wire choice is the usafe part.
As said,
Not really true, if they're sized right they will protect the whole circuit. Obviously, there's no "absolute" protection for electronic devices running around on metal rails, but a properly sized circuit breaker with good response is a key element in any protection.
The magnetic breaker is about as fast as you're going to get at a reasonable price....( They can be touchy with peaks though. That's why I keep pointing at the adjustable #91... If I can run under a 10a setting, I'd want to. You want the lowest amp fuse/breaker you can get away with period.)
...But wire chosen should easily handle what you allow to cross it with a breaker, even with a magnetic one. A 10a breaker needs all wire to handle 10a without issue unless another fuse/breaker of lower value allows a step down along that path.
A breaker or fuse is a weak point; the weakest point; placed in a ciruit on purpose to protect wire, switches, loads or the supply, and/or each individually.
To give you an idea how far you can go with concept, my last road legal offroad buggy came with 8 fuses. When done, it had two fuse boxes and 72 fuses. 3 added gauges, foglight set added, radio removed, washer fluid motor removed. All run in 2 looms, fore and aft. A burnt harness was not going to strand me hwy, tundra, or woods because of any one item, switch or wire shorting. Even my batteries, generator, regulators, and starter had fuses. (generator could be an emergency starter too)
Lionel internal breakers do provide some protection across the board if you use a large enough wire gauge. But it isn't ideal because each circuit should be evaluated and fused individually... then if you're lucky you can combine some and have lighter feeds put in place, etc. (there ARE some panel tap combinations for accessories that remain unprotected by internal breakers to throw another wrench in the works, lol) ...Also of mention, the thermal and point wear on the internal breakers is lower if it only gets tripped by occasional testing, so should live a long healty life with these others doing the dirty work.
If you had multiple loads on the magnetic breaker; load A is fine but heavy, fat wire, and loco for load. Load B is lighter, it begins to faulter, & so draws hard on your undersized jumper, but still less load than the loco is using. The jumper is in jeapordy. The heavy load A is possibly going to mask the lower draw long enough for the light jumper to melt. No direct short, just a slow draw just over the lighter wires rated capabilty, maybe leading to a short
I.e. I'm not too sure, but I'm afraid you guy are missing something fundimental. Even with magnetic breakers you can't just plunk down a high value 10a breaker then run undersized 3-4 amp wire and expect everything is as safe as can be.
At that point, the magnetic breaker only protects certain fast draws and reacts to sharp resistance/peak issues, like direct shorts. It does not magically protect wire from ALL high draws.
So, an underguage 4a wire's insulation melting down under a 5a slow build, slow-cook draw, because of 10a delivery capability and no spike to detect yet, the melt ends in a dead short....which, oops, finally trips it, but too late to help the wire and the other(s) now melted...is possible.