Circuit breaker basics

I removed your link and embedded the video for you.

Thanks, Rich.  While I do not know how to embed a video file, if I did I would not have done so to avoid embroiling OGR in any copyright issues.  RJR

One misconception in the presentation.  The reason that AC and DC magnetic circuit breakers are not directly interchangeable is not due to voltage differences, but rather by inductive reactance of the solenoid to the AC current that is not present for DC current.  The inductive reactance for the AC current makes the trip point different for AC than DC in any given magnetic breaker.

Nice video.  So what breaker should we use between the transformer and the track?

Personally, I use push-button marine circuit breakers which are available from Defender Marine Supplies or West Marine, and come in 5,7,10,15 amps.  These are thermal type, and in the $5-$8 range.  I use the smallest avaiable above what I normally pull on a circuit.

If I could locate reasonably-priced electronic units, or induce one of our forum electronics gurus to produce a kit for same, I'd go to them.

The Lionel Powerhouse PH-180 has a built-in electronic breaker, and sometimes I think it may be too fast, opening if a wheel flange brushes a center rail when going through a switch.

This makes me wonder...  I have assumed that running post war locomotives on conventional power does not require a separate external circuit breaker between the ZW 275 and the track. Correct?

Well, no running "requires" good circuit protection, but you do yourself a favor by having decent circuit protection to the tracks.  The breaker in PW transformers are there to protect the transformer, they don't protect your wiring or locomotives.  Obviously, PW stuff with no electronics is less likely to die due to voltage spikes, but a derailment and short circuit can spoil your day anyway.

Ok. What do you recommend that I purchase. (I was under the impression that my locos built 1948 through 1954 were safe as is. I will get the added protection. 
What do you recommend and what is the TIU to which Stan refers?

Don, those old locos probably would never be affected by a short on the tracks, since the overcurrent wouldn't be flowing through the loco.  The breaker protects the entire circuit from overheating if there is a short.  Such overheating can result in a fire.

I use the Lionel postwar 91 circuit breakers. These are magnetic breakers so they open instantly when a short circuit occurs. They open with a load snap and have a red light indication they are open, so no mater where I am in the room I know what happened. I have never used the prewar version, but I believe it is also magnetic and may be just as effective. 

If I just counted each individual repairs, the repair I make most frequently is the replacement of the knuckle spring. When this spring is bad the coupler knuckle will not open when the pin is withdrawn releasing it.  I believe that most of these knuckle springs have died because they were in the short circuit path after a car came off the track.  This little spring has very small wire and when it carries short circuit current it gets very hot annealing and softening it.