TMCC Lockon and post war ZW???

[KRM]

Hi guys,

I was watching this video on the Charles Ro web site 

http://www.charlesro.com/store/merchant.mvc?Screen=CTGY&Store_Code=CRSC&Category_Code=OLTP

  They suggested using a 6-34120 TMCC lockon with the post war ZW to protect newer equipment.

 

I was thinking that I could wire one in between my ZW and the main feeder bar that supplies the power to all of my track power lockons. I would think you would need to put it at the 180 watt setting to use it and it would eliminate the need for any other fast blow breakers and TVSs.

I am currently feeding 10 lockons around the track that all have a TVS at them or in front of the power to them.

Your thoughts??

Tks,

Kev.

[lionelsoni]

There is no particular advantage to fast circuit breakers.  Overvoltage, not overcurrent, is the threat to locomotive electronics.  You should be fine with all those TVSs.

[KRM]

Thanks Bob,

 I was just thinking it might be a good idea to have the better breaker because right now I only have the newer style in the ZW

Kev.

[gunrunnerjohn]

Actually, overcurrent is a problem!  When you have a derailment, it's best to have something that immediately shuts off the power.  If the power remains on, you can get arc spots on the wheels and pickups, also if at pickup roller sets on the middle rail and the other on the outer rail, the internal wiring may smoke, it's frequently a lot smaller than the exterior wiring. 

I think the TMCC Direct Lockon is a good solution.  It'll work with most any transformer, for the ZW or KW, I'd set it to 180W.

Note that the TMCC Direct Lockon doesn't work for conventional, below 10-11 volts it'll quit working and drop the track voltage.  It's only for directly connecting a fixed voltage for command/control.

 

[KRM]

gunrunnerjohn

 Note that the TMCC Direct Lockon doesn't work for conventional, below 10-11 volts it'll quit working and drop the track voltage.  It's only for directly connecting a fixed voltage for command/control.

 

Thanks John, Now I get it. I think.

Most of my stuff is pre-war. All of it is conventional.

 I do not have any TMCC and don't plan on it anytime too soon but not to say I will not go there as the $$$ allows. I do have some newer stuff like some 90s Lionel and some 2011 RMTs that have electronics in them. So as Bob said I guess I would be okay with the TVSs I have because a lot of my running is below the 10-volt range.

Am I right or confused? 

Tks,

Kev.

[lionelsoni]

It is true that the wiring between pickups on separate trucks are vulnerable in that way.  I've never had that particular case; but perhaps a better solution (other than beefing up the internal wiring) would be to put lower-current circuit breakers on the individual transformer outputs.  Few trains need more than 10 amperes, and many would be fine with 5.  The full 15 amperes of the ZW would still be available for the total load, but the lower-rated breakers would trip sooner for any one train's derailment.  In any case, though, the threat is not to the electronics but to that wire between the trucks.

A related situation that I have seen a couple of times is a derailment where the wheels of one car's truck are on the center rail while the wheels of the truck to which it is coupled are on the running rails.  This can burn out a coupler spring (with a bright flash).  I once also had the thin steel actuating rod in a 2500-type passenger truck burn out for the same reason.  A lower overcurrent protection might have saved the latter case; but I doubt that any current limit that will let a train run will protect the tiny spring on a coupler knuckle.

[gunrunnerjohn]

Well, the coupler springs are easy to replace, so I'm not so worried about those.  I recommend resettable fuses on the wiring between pickups for the very reason of shorts.  It's not always practical in locomotives, but I've never seen a passenger car that you couldn't put them into.  That's part of my modification when I install LED lighting in my passenger cars.

I agree with the lower value fusing or circuit breakers for conventional operation, since there's only one train on the handle, 5-6 amps should be plenty.  For TMCC/DCS, it's a bit trickier, as you can have three or four trains on one power district at the same time.  That's where the TMCC Direct Lockon works out well.  It's also why I like LED lighting in any lighted car, it cuts the power consumption of non-locomotive rolling stock to next to nothing.

 

[lionelsoni]

Why not just duplicate the rectifier for the passenger cars, to isolate the pickups?

[gunrunnerjohn]

lionelsoni

Why not just duplicate the rectifier for the passenger cars, to isolate the pickups?

I typically use bridge rectifiers for the lighting supply, and using the PPTC is cheap and effective.  Are you suggesting that's a better method?  If so, why?

[lionelsoni]

Use two bridge rectifiers, one fed from each pickup, and connect their outputs in parallel.  There will never be any fault current to interrupt, no matter which rails the pickups land on.

[gunrunnerjohn]

I don't see this as a superior solution, but if you're happy with it, you're free to do it your way.

[lionelsoni]

Unless it happens right at a zero-crossing of the current waveform, clearing a fault can cause the transformer's stray inductance to generate a voltage spike, which is not a good thing.

[gunrunnerjohn]

That's what the TVS suppression diodes across my track feeds and in every TMCC locomotive and tender are for.