Well, I finally completed my latest project, converting a large DCC layout powered by a single 5 amp booster with five reversing sections controlled by Digitrax AR-1 units into 4 power districts controlled by circuit breakers.
This has been a real learning experience for me, and I drew several conclusions along the way.
One conclusion has been that my old reliable Digitrax AR-1 units with their mechanical relays do not not work with solid state PSX circuit breakers. As a result, one power district, the double mainline with three AR-1s remain protected by the main 5 amp booster rather than a PSX circuit breaker because I was not about to replace the perfectly good AR-1s with more expensive PSX-AR units. In fact, I moved the fourth AR-1 wiring to the mainline and out of a newly created power district for the same reason.
Two newly created power districts contain no reversing sections, and the PSX circuit breakers that protect each power district work just fine. So, my second conclusion is that circuit breaker protected power districts are an excellent way to keep mainline tracks running when shorts bring locos to a halt in yards and service facilities and vice versa when a short occurs on the mainlines.
My third conclusion is that a PSX-AR is the ideal way to implement a solid state auto-reverser when circuit breaker protected power districts are in use. On my layout, I did create one power district where I replaced an AR-1 with a PSX-AR. I did this because the entire power district was one big reversing section.
My fourth conclusion is really more of a question. When you have a reversing section within a power district, what do you do for circuit breaker protection? You can use a PSX-AR to control the reverse polarity, and the PSX-AR has a built-in circuit breaker. But as far as I can determine, that circuit breaker only protects the reversing section, not the entire power district of which the reversing section is only part of. So, apparently, you need a separate circuit breaker to protect the entire power district. So, why does the PSX-AR even have a circuit breaker associated with it?
Rich
Alton Junction
richhotrainWhen you have a reversing section within a power district, what do you do for circuit breaker protection?
The non-reversing section should be protected by its own circuit breaker. Or it can simply rely on the command station's circuit protection feature, which has the drawback of shutting own the entire layout when it trips.
richhotrainSo, why does the PSX-AR even have a circuit breaker associated with it?
Rich,
I think it was Randy who went into detail on this in another thread. A short is electrically different from the breaking of the electrical gap that a wheel causes when it passes into and out of the reversing section. It used to be that implementing both forms of protection required two separare modules. The PSX-AR handles both at the same time, which is what makes it good.
Mike Lehman
Urbana, IL
If you have a power district you protect it with a circuit breaker. If you include an auto reverser in part of that district, the AR protects the reversing section even though the circuit breaker protects the portion outside the reversing section. The PSX AR works by detecting a short circuit condition when a loco enters a reversing section and corrects it. But if you do the quarter test on the reversing section the AR cannot correct it and shuts down the section just like the main breaker does.
If you have two trains entering a reversing section from the opposite direction at the same time what will the AR do? Would it detect a non correctable short and stop both trains, or reverse the direction of one of the trains?
I think what both of you are saying is that you need both a PSX circuit breaker and a PSX-AR when you have a reversing section within a power district. That seems to be the implication of this drawing included in the PSX-AR instructions, as illustrated below.
No, that isn't right when it comes to the PSX-AR.
You're thinking in terms of the AR-1, but remember, the PSX-AR is BOTH a breaker AND an auto-reverser in one unit. So unlike the AR-1, the PSX-AR both protects the reversing section, and flips it's polarity (actually it's phase) as needed.
That's what the diagram shows. The PSX-AR is both protecting and flipping the reversing section, and the breaker they indicate as optional would protect the non-reversing section past the gaps.
If you put the PSX-AR behind another breaker, at best you're unnecessarily duplicating the breaker's function, and at the worst you might end up with a race condition, since unfortunately the PSX devices don't have an adjustable delay.
richhotrainI think what both of you are saying is that you need both a PSX circuit breaker and a PSX-AR when you have a reversing section within a power district.
"need" might be the wrong word. You can always rely on the comand station's protection circuit for the rest of the power district. Or it could be protected by extension of the coverage of a neighboring power district circuit breaker. To me, it would depend on the chances of having a short in the non-reversing part of a power district, if you choose to include. If it was a stretch of mainline with just a few turnouts, then I'd probably just wire it for protection from an adjoining power district. In fact, that's what's shown on page 2 of the PSX-AR manual.
Stevert the PSX-AR is BOTH a breaker AND an auto-reverser in one unit. So unlike the AR-1, the PSX-AR both protects the reversing section, and flips it's polarity (actually it's phase) as needed. That's what the diagram shows. The PSX-AR is both protecting and flipping the reversing section, and the breaker they indicate as optional would protect the non-reversing section past the gaps. .
the PSX-AR is BOTH a breaker AND an auto-reverser in one unit. So unlike the AR-1, the PSX-AR both protects the reversing section, and flips it's polarity (actually it's phase) as needed.
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That is my point, though. The "optional" circuit breaker is needed to protect the non-reversing section past the gaps.
In which case, you need both a PSX-AR and a PSX.
mlehman To me, it would depend on the chances of having a short in the non-reversing part of a power district, if you choose to include.
To me, it would depend on the chances of having a short in the non-reversing part of a power district, if you choose to include.
Exactly. And that is the point that I am trying to make. You need both a PSX-AR and a PSX circuit breaker.
Okay, I didn't catch that you were talking about two different sections - The reversing section, and the section next to it. It sounded like you wanted to run the reversing section through two units - First the PSX, then the PSX-AR.
But yes, the PSX-AR's built-in breaker would protect the reverse section, in addition to flipping it as required.
Then one or more other breakers to protect other sections of the layout.
Stevert Okay, I didn't catch that you were talking about two different sections - The reversing section, and the section next to it. It sounded like you wanted to run the reversing section through two units - First the PSX, then the PSX-AR. But yes, the PSX-AR's built-in breaker would protect the reverse section, in addition to flipping it as required. Then one or more other breakers to protect other sections of the layout.
Let me clarify something a little more.
Yes, I am talking about two sections, the reversing section and the adjacent non-reversing section, but both sections would form part of a single power district separate from the rest of the layout. To fully protect that power district, it seems that I need both a PSX-AR and a separate PSX circuit breaker.
In my current situation, the only reason that I need just a PSX-AR for one of my power districts is because the entire power district is one big reversing section.
richhotrain...why does the PSX-AR even have a circuit breaker associated with it?..
I'll give you a quick example to see if it helps. Say you have a loop to loop railroad(reverse loop, mainline, reverse loop), and you want to break it up into three power districts - each reverse loop and the mainline. If you put a regular auto-reverser(without built-in circuit breaker) on each reverse loop and a circuit breaker on the mainline, then a short on the mainline will not shutdown the reverse loops but a short on either reverse loop WILL shut down the mainline. You have to have an auto-reverser and a circuit breaker on each loop to keep a short on one of them from shutting down the mainline. Having the circuit breaker function built in to the auto-reverser eliminates the need for the additional circuit breakers.
richhotrain mlehman To me, it would depend on the chances of having a short in the non-reversing part of a power district, if you choose to include. Exactly. And that is the point that I am trying to make. You need both a PSX-AR and a PSX circuit breaker. Rich
Again, maybe. How big is a bushel basket? Doesn't matter as long as you own the only basket in town...
OK, I digress. But it really is one of those things where there are really two choices. Can the section where the "optional" breaker is shown be piggybacked onto the adjacent section's breaker? If yes, that's basically what page 2 in the PSX-AR manual shows.
If no, in other words, if there are reasons why you want that section to be supported independently by its own breaker, then yes, you need an extra or "optional" breaker.
I think the assumption tripping you up was that the PSX-AR independently supported an auto-reverser and a breaker. No, the breaker function is piggybacked together with the AR function in the PSX-AR. I think it's just one of the quirks of a DCC system that the terminology doesn't necessarily clarify everything. This is especially true with regard to terms that the NMRA doesn't define. Each vendor uses a different set of terminology when things often function just the same and then uses similar sounding terminology that will make you think they function the same, when they often don't. Digitrax has the way they implement things and NCE has theirs, with PSX mixing it up because it offers something NCE doesn't quite have while at the same time pitching their better mousetrap to Digi-users.
Are you thoroughly confused now? I almost am and I'm writing this. It's natural that things often don't work quite the way we think the do. Been struggling with the household icemaker between posts. I think I'm learning something...maybe that I'm confused?
CSX Robert richhotrain ...why does the PSX-AR even have a circuit breaker associated with it?.. I'll give you a quick example to see if it helps. Say you have a loop to loop railroad(reverse loop, mainline, reverse loop), and you want to break it up into three power districts - each reverse loop and the mainline. If you put a regular auto-reverser(without built-in circuit breaker) on each reverse loop and a circuit breaker on the mainline, then a short on the mainline will not shutdown the reverse loops but a short on either reverse loop WILL shut down the mainline. You have to have an auto-reverser and a circuit breaker on each loop to keep a short on one of them from shutting down the mainline. Having the circuit breaker function built in to the auto-reverser eliminates the need for the additional circuit breakers.
richhotrain ...why does the PSX-AR even have a circuit breaker associated with it?..
CSX, thanks, I see what you are saying and it makes sense.
mlehman I think the assumption tripping you up was that the PSX-AR independently supported an auto-reverser and a breaker. No, the breaker function is piggybacked together with the AR function in the PSX-AR.
I think the assumption tripping you up was that the PSX-AR independently supported an auto-reverser and a breaker. No, the breaker function is piggybacked together with the AR function in the PSX-AR.
Yeah, I think that is at the heart of my problem with fully understanding the PSX-AR. Initially, I did wrongly assume that the auto-reverser and circuit breaker operated independently of one another. I see now what is going on there.
Thanks for that additional explanantion, Mike.