ZW Transformers

I respect what you are doing for the hobby by refurbishing and keeping these old postwar transformers in use. Personally I no longer use postwar transformers for a variety of reasons. Many of my fellow AF operators like to use ZW's to run their trains, they operate postwar Gilbert engines. Those who use postwar transformers with modern Lionel AF Legacy or FlyerChief engines use modern circuit breakers with built in spike protection. An example of one is the Dallee #1113 breaker with spike protection. This is an 8A model, other ratings are available. The spike protection is essential for operating modern engines, or even old postwar engines that have an electronic E unit in place of the old mechanical E unit.

I am familiar with Gilbert transformers but not the internals of Lionel transformers. In Gilbert transformers the breaker is ALWAYS at the Base Post terminal so all outputs are protected, plus the transformer core rating is the sum of the fixed and variable outputs. The Base Post is the only place the entire core power is seen by a breaker.

TinMan

You mentioned you installed "modern circuit breakers, which open much faster than the original. After several hundred transformers sold and or reconditioned, we have not received a single complaint regarding this issue. This does not mean there have been problems, it just means we have not heard any."

Your are proposing "installing 2 chassis mount fuse holders on both the ZW and KW transformers".

Is the fuse you propose to add faster than the "modern circuit breakers" ?

Fuses on the transformer feeds to O gauge trains can cause a lot of fuse changing and time lost running trains.  The reset button on a circuit breaker is a real plus.  Fuses cost time and money verses circuit breakers.

Charlie

@TinMan3rail posted:

As I am sure you know a fuse will blow almost instantly.

You have a lot to learn about fuses.

I like fuses. But you will have to use fast blow fuses to get the desired results.

This is an interesting discussion.

The older, all tube Fender guitar and bass amps had "Slo Blo" fuses; I'm guessing the fuses being discussed here are just the opposite?

Mark in Oregon

Mark, kind of. Those old amps had a lot of margin and usually had heat sinks on the amps and sometimes even cooling fans. They could take a substantial overload for short periods of time, just the distortion percentage would go up. Plus any group whose amps blew fuses on a big base note would not get many bookings!

Postwar transformers have no heat sinks and are in enclosed cases. Use a Gilbert 100W transformer as an example, Lionel transformers will be similar. the 100W rating is input. For continuous duty it will output 75W, 5A @ 15V. That metal case would get really hot. I can tell you from more than 60 years of experience that a 4B will deliver 8A short duration, the voltage sags to about 13V at that load. The auto resetting thermal breaker inside the case would eventually trip, maybe a minute. However If I accidentally laid a screwdriver across the rails, which happened many times in days gone by, the breaker would trip in less than a second.

The above is why I use an 8A fast acting breaker on the 4B and 15B transformers. They have margin and we do not want to trip the breaker right at rated load, it is unnecessary. Also I make sure that the total connected loads are not over 5A continuous.

A lot of AF high rail operators use ZW's. They are great transformers and have a lot of short term margin above the rating. The 275W input rating translates to maybe 220W output but for short durations they can easily output 275W. Breaker or fuse selection needs to take that into consideration to prevent nuisance tripping.  The circuit protection must be selected to distinguish between shorts and momentary overloads.