The Perplexing Case Of The Melty Lounge Cars

[kvp]

Inobu, imho you weren't reading carefully enough. The problem is that the cars short two opposing controllers together. This sends 3A short current through each bogie as they cross.

 

The 6A is the total current capacity of two matching controllers connected in parallel by the bogies.

 

Both could happen on a correctly wired layout with no proper current limiting at the rail level and more than one controller.

 

The solution in both cases is a fast tripping overcurrent protector in each block, set to something sensible like 1.5A (=3A with two in parallel).

 

The polarity warning would be usable to detect operator error before the train crosses over, so the short could not happen or immediately detected in case someone switches under a train.

Edited November 13, 2016 by kvp

[inobu]

kvp,

 

You need to look at the configuration. The PM42 is designed to take 1 power supply that supports one command station and its boosters to distribute a single DCC signal among 4 independent outputs. The four outputs are electrically isolated but still has the same common power supply. It appears that this configuration is

not utilizing DCC but using DC. What and how the PM42 operates with DC is not talked about.  

 

This configuration does not make sense to me. The PS2012 in N Scale mode puts out 13.8 volts at 20 amps. That is too hot for N-scale. The Y52 is 5 amp protection going into what ever the transformer/controller is. (it is undermined....wireless of some sort as posted) that is still kinda hot. "2 opposing controller" means a hand off of some sort. This hand off is the beginning of the problem but I think the configuration is the root cause.  

 

I guess adding breaker on top of another breaker works but only slows the issue down not resolve it, Every time the carriage goes from one block to another that 3 amps is going light up that bogie. 

 

Maybe these DC configurations are out of my league. i think I'll stick to my simple DCC stuff.

 

Inobu  

Edited November 13, 2016 by inobu

[kvp]

This handoff is electrically the same as going from one loop to another, controlled by two Kato transformers.

 

If you set one forward and one backwards, the cars will short the two controllers on both rails (power to ground and ground to power). This means full power short until the safeties trip. (usually within a few msec)

 

If you are going across with the right polarities, the available current will double as two controllers are feeding the salme train. (one directly to the locomotive, the other through the car above the isolation)

 

Current limiting each block with a fast acting limiter that turns back on only after turning the power off guarantees, both controllers have to be turned to zero before the train gets power again. The polarity mismatch warning is good to avoid getting a short in the first place. Having controllers that have sensitive short detection, including shorts with another controller, would eliminate the need for anything else as with the Kato ones.

 

ps: the same problem occures with a high power dcc booster with weak short detection and any sort of short circuit

[inobu]

Like I said the configuration with the PM42 and two controllers does not make sense to me and I think the bogies agree. This problem has been going on for

months. To create a DC environment/layout where you can fry bogies but have multiple DC controllers just-don't-make-sense.

 

 

ps: the same problem occures with a high power dcc booster with weak short detection and any sort of short circuit

 

I guess I have to agree.....the same problem will occur on a poorly designed DCC layout with shorts.

 

Inobu

[kvp]

I would like to repeat that this kind of shorting is normal with multiple DC controllers and could happen on any layout with electrofrog turnouts (even with a single controller). These shorts are expected on most operator faults, even with two Kato controllers. The trick is to limit the short circuit current both in size and time. In N, this means 1-1.5A fast acting safeties that turn off the power on a short and leave it disabled until the DC power is turned off. (pm42-s can't do this and don't support out of synch boosters/controllers/reversing loop situations at least without an ar1 on every output and running on full throttle dcc levels)

[Davo Dentetsu]

Insanity never entered into it, we thought we fixed it at the time?

[inobu]

I would like to repeat that this kind of shorting is normal with multiple DC controllers and could happen on any layout with electrofrog turnouts (even with a single controller). These shorts are expected on most operator faults, even with two Kato controllers. The trick is to limit the short circuit current both in size and time. In N, this means 1-1.5A fast acting safeties that turn off the power on a short and leave it disabled until the DC power is turned off. (pm42-s can't do this and don't support out of synch boosters/controllers/reversing loop situations at least without an ar1 on every output and running on full throttle dcc levels)

So your remedy is to place fast acting breakers to the layout and have the operator enable/reset/power on his controller each time it's tripped. OK

 

Davo,

 

It's not a good configuration for club operation. Some one is going to lose one of their prized units and that's when the real problem will start. I think I'll

leave it to you guys to figure this one out as it's beyond my level of expertise.

 

Inobu

Edited November 14, 2016 by inobu

[Davo Dentetsu]

Well, anyway.  Now I'll be chasing up new bogies for this coach.  Anyone familiar with the Tomix part number?

[Davo Dentetsu]

Why AMRA WA seem to push this as my issue I'll never know, their faulty layout caused this!

 

https://imgur.com/gallery/zlnqt

[kvp]

As soon as a club has sig-s and commitees, my only advice would be: run...

[Ochanomizu]

Hello,

 

Apparently electrical problems on a layout can be rectified by spending less time on social media and more time walking around the layout ... :whistle:

[kvp]

Actually yes. As long as you have a wire cutter in your hand and keep removing the circuits that are not functioning properly. This forces everyone who want to to run a train to look for a solution somewhere, like on social media (=forums)...

[Davo Dentetsu]

Hello,

 

Apparently electrical problems on a layout can be rectified by spending less time on social media and more time walking around the layout ... :whistle:

I have found an alternative idea.  I'll leave them to their mess entirely, save my membership fee that I won't be paying any further and just go elsewhere.