electricall fuses

If a 10-amp fuse is getting blown often, there's a problem somewhere, and it's not the fuse.

@360RPM posted:

I have a post war ZW transformer with a fuse between the transformer and the rails. What amp fuse would be appropriate so that it doesn't get blown a lot, but still provides protection to my newer electronic locomotives. The 10 amp fuse I am using gets blown to often.

Ditto on needing to find the underlying cause. Unless you are running multiple engines on one circuit, a ten amp fuse should not be blowing in normal use. I use five amp circuit breakers on each of my circuits, and rarely if ever have them trip under ordinary use.

Speaking of which, I think the relatively slight extra cost of circuit breakers is well worth what you have to pay to never again have to replace fuses. If you have expensive electronics on board your rolling stock, the instant-action circuit breakers are well worth the money, but since I just run PW trains, the cheap thermal breakers I used have so far done fine, at a fraction of the cost of the better versions.

Thanks for your reply. The fuse blows when I have a derailment.  I have tried to order an airpax instant breaker, but they are out of stock. Do you have any other suggestions for a breaker? The engine that is mostly causing the short when derailed is a Western Pacific SD70-AC.

@360RPM posted:

Thanks for your reply. The fuse blows when I have a derailment.

As it should be.

@360RPM posted:

Thanks for your reply. The fuse blows when I have a derailment.  I have tried to order an airpax instant breaker, but they are out of stock. Do you have any other suggestions for a breaker? The engine that is mostly causing the short when derailed is a Western Pacific SD70-AC.

Suggest searching the forum for posts on circuit breakers and TVS diodes - there are lots of threads on this topic.  There are fast acting breakers (not as good as the Airpax, but sufficient for most uses) which are similar to those found on MTH power bricks that sell for under $10 each - I'm sure there are links in the other forum posts on this topic.

You don't mention the manufacturer and model number of the engine that's having most of the derailments, but since it's an SD70, it probably contains modern electronics.  Having frequent derailments is playing Russian roulette with the electronics - in addition to a better breaker, add a TVS diode to either the circuit or the engine.

It's a Lionel modern loco with Legacy Railsounds. But it is very long and probably too long for the 042 turn that takes it into the stub. I considering taking one of the stubs out and making the turn into the other stub a 054 turn.

@360RPM posted:

I have tried to order an airpax instant breaker, but they are out of stock. Do you have any other suggestions for a breaker?

Check the Octopart links here.  

They show a few suppliers with the Airpax Instant in stock.

@360RPM posted:

I have a post war ZW transformer with a fuse between the transformer and the rails. What amp fuse would be appropriate so that it doesn't get blown a lot, but still provides protection to my newer electronic locomotives....

@Mallard4468 posted:

Suggest searching the forum for posts on circuit breakers and TVS diodes - there are lots of threads on this topic.

Fuses / breakers are the wrong device for the protection you seek.

You really need Transient Voltage Suppression.

@360RPM posted:

Thanks for your reply. The fuse blows when I have a derailment.  I have tried to order an airpax instant breaker, but they are out of stock. Do you have any other suggestions for a breaker? The engine that is mostly causing the short when derailed is a Western Pacific SD70-AC.

Well, at least there's no mystery to be solved -- as others have already said, that's what a fuse is for.

I also agree that, in addition to instant-action (or slower but cheaper thermal) circuit breakers, TVS diodes on each circuit are important, because derailments can cause voltage spikes that can wreak havoc on modern electronics. IMHO, the only mystery is how you got so lucky as to have not already fried your circuit boards, given the number of derailments you've had.

[Which brings up another topic: you may want to figure out what's causing so many derailments. If they typically happen in the same areas (certain switches or curves, for instance), you may have a track or rolling stock issue.]

@Steve Tyler posted:

...in addition to instant-action (or slower but cheaper thermal) circuit breakers, TVS diodes on each circuit are important, because derailments can cause voltage spikes that can wreak havoc on modern electronics.

...the only mystery is how you got so lucky as to have not already fried your circuit boards, given the number of derailments you've had...

The damage to the electronics is ongoing even in the absence of a derailment, and is cumulative.

TVS protection is mandatory, fancy/additional/redundant overload protection is optional.