circut breakers

Earl,

Circuit breakers are useful but the problem is they take a while to trip.  We often think a 10 A circuit breaker will "break" at 10A.   Note this chart from a Mouser datasheet for a typical pushbutton type circuit breaker (when it pops, a button pops out and is reset by pushing it back in)

Looking at the chart, a 10 A circuit breaker will pop after one hour of a 14.5 A load!  That's OK for a direct short circuit (lots of amps more than 10), but even for a 40A load, this 10A breaker may take between 1.6 and 4.5 seconds to "pop".   Not much protection for delicate electronics.

Finding a high speed circuit breaker becomes the issue of $$$$. A cheap one may be OK for a real solid short circuit, but that's about all it's good for.

Ed

For a fast trip electronic breaker, check out the PSX-AC from DCC Specialties.

Conductor Earl, consider using PTC Resettable Fuses - AKA PolySwitch, Polyfuse, PolyTron, MultiFuse as described in depth at Circuit Protection for Toy Trains .

The PTCs reset by turning off power until fault is cleared, restore power and run.

Susan, the PTC isn't all that fast unless it gets a significant overload, same issue as with the circuit breakers.

I use digitrax PM42 s.    They were great and have adjustable amperage settings.     Each board has 4 breakers.

I looked at the PM42, one thing that is odd.  They don't say what kind of track power.  I'm assuming they'll handle DCC, so it should handle AC, but it would be nice if they were specific in the specifications.  They went out of their way to tell you that you could use AC or DC for their separate logic power supply, why not specify the specifics of the track power?

Earl,

   The great thing about the Scott type 10 Amp breaker bank I have, is that they really break around 8+ Amps so I am very satisfied with them, and have never had a problem with them doing the job correctly, and they seem to be lasting for ever.  

PCRR/Dave

+1 vote for the PSX-AC, they are a incredibly fast - a marvel of electronic wonderfulness.

gunrunnerjohn posted:

Susan, the PTC isn't all that fast unless it gets a significant overload, same issue as with the circuit breakers.

They're priced so reasonable I've been able to size mine using different values for specific uses and they trip fast enough to protect my electronics and postwar accessories.

Your correct that the 8A and 9A values I use on my main lines for multiple passenger cars don't trip fast enough with low power faults.  The 2 A values can be placed in the engines for max protection.

Try a smaller breaker, one with a rating just above your normal draw.  5 amp or even 2 or 3 would be fine is you have only one loco.

Dave, if any breaker opens below it's rating, it's not rated properly, or is malfunctioning.

I use 1.1A hold PTC's in series with motors using the ERR Cruise Commander Lite to prevent damage due to a motor stall.  I cooked one of my beta test units when the K-Line Interurban snagged a switch and stalled the motor, that was my solution.  So far, no more cooked boards in the half dozen I've installed in my stuff and the others that have gone out the door.  Of course, any protection is better than none, and I like the PTC for inside units as you don't have to open them up to fix anything if the trip.

RJR,

   I have been aware that the 7 Amp and the 10 Amp Scott type breakers have been breaking pretty much at the same time for many years, probably the 10's were built to light from the very beginning, but they work great on my layout, and they do not sell the 7 Amp Breaker Banks at Train Electrics any more.  They were pretty much phased out when Scott got bought out.  I still recommend them they work perfectly with my DCS/Legacy Christmas layouts

PCRR/Dave

Dave, FYI, the Scott type breakers are just OEM circuit breakers, the ones I saw were the TE Connectivity breakers that are used in a majority of MTH transformers.  There's nothing wrong with them, but neither are they anything special.

OK, just so you know.  They are thermal breakers, so their internal characteristics might change with time

5 & 7-amp breakers are still available from Defender Marine & other marine supply houses.  I use 5's on all circuits but one where I often run 3 or more locos; that's 7.

I recently replaced a KW with a Powerhouse 180; it appears the Powerhouse's breaker opens on derailment before an external 5 amp. 

GRJ, can you elucidate?  Do you mean the manual breakers on the Z-series transformers & bricks, or the internal breakers of a Z4000.

The PH180 has an electronically triggered breaker, it's the best one I've seen on a brick, and far superior to a thermal breaker.  I'm led to believe the ZW-L has excellent foldback protection as well. 

RJR posted:

GRJ, can you elucidate?  Do you mean the manual breakers on the Z-series transformers & bricks, or the internal breakers of a Z4000.

The Z-4000 has standard TE Connectivity thermal circuit breakers for each output, they're on either side near the rear.  It also has internal electronic protection.

Thanks, I was wondering if TE made the internals.

Since you've mastered the Digikey and presumably other catalogs, do you know of any reasonably-priced magnetic breakers in the 5-10 amp range?

Nope, I've looked for magnetic breakers, they're all much higher priced than the thermal models.  They seem to be $30 and up.