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Current News "Help Me I am Melting"

Dave Heap from Australia sent us this response to our article.

There are two reasons for melted wires:


1) Too much resistance in the circuit (wiring, track joins) to allow sufficient short circuit current to flow and trip the booster promptly.


2) Too slow a tripping time for the booster.


Boosters are designed to protect themselves, not the layout. For example an NCE booster takes 500ms to shut down, and large currents can flow for a significant time before then.


Current limiting devices such a light globes exacerbate the problem. They allow relatively high currents to flow indefinitely, casing overheating.


There are two good mitigation strategies:


1) Reduce loop resistance - thicker bus wires, more frequent droppers (every rail section), never relying on rail joiners, remove globes and other current limiting devices.


2) Fast acting adjustable circuit breakers. Some can be set to operate in as little as 10ms, and the trip current can be reduced to the minimum needed to feed your locos. Reducing the trip current helps mitigate the effect of inadequate wiring.


Dave Heap, Armidale NSW, Australia, Committee member, website manager, resident electrical/electronics/computer/DCC expert is a member of the

New England Model Railway club: http://www.newenglandmodelrailwayclub.com/


Dave is beginning a series of articles in his bi-monthly club newsletter and is later putting the articles up on their club website at:

  http://www.newenglandmodelrailwayclub.com/content/articles.shtml

Thanks Dave,

Paul Wussow

Updated 11/10/14
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