Circuit Protection for MTH Locos when Using Lionel KW Tràansformer

Chasp;

While I don't run any MTH engines and use a pair of PW ZW transformers, I believe the answer is the same - you should place a fast acting 10 amp circuit breaker between the transformer and the track. I bought mine from digikey.com. They have already saved me several times! As a self-confessed electrical techno peasant, I picked up a copy of OGR's Backshop Video, Vol. 8 at York which included a clear segment on creating a circut breaker box.

Many thanks Paul.  I'll check DigiKey on line.  

ChasP, Geek-less in Colorado!

Can you provide Digikey part number? The website is daunting...thanks

Chasp,

    I use 10 or 7 Amp Scott type resettable breaker banks in front of my KW & ZW Transformers, place them on every Red Channel of the TIU between the Transformer and the TIU.  

PCRR/Dave

Gerry posted:

Can you provide Digikey part number? The website is daunting...thanks

Gerry;

Sorry... I thought I put it out there. It is part # PB190-ND. That is a 10 amp breaker.

P.S. "daunting" is not the word I used when I was looking, but this is a PG site!!!

I use 10 am inline auto fuses.  I bought the fuse box from a  company that used to be called Scott's Odds and Ends .... but changed its name to something else ... I think it now called Trains Electric.  I've had 2 blown fuses over the last year.... and saved big money by wiring my layout this way.

I control my Mountain Division and trolly line with a 250 watt ZW using 10 amp in line fuses.  The two lower mainlines are controlled with an MTH Z4000.   

I do mine this way

LINK

Dale H

I don't think it has been mentioned yet, but adding transient voltage suppresors (TVS) will provide additional protection to any modern engines you are running.  These are good even if you are running conventional.  Here is a simple diagram I used for my first layout.  You only need one TVS at the transformer, but I add the others at the track connection for extra protection.  Might be overkill.

I use the same breakers, only 5 amp, on each channel. I run 2 MTH diesels with smoke on each track with no problem. I can run 3 without smoke, even with one being 6 lighted passenger cars. They trip immediately in a derailment. I assume they trip faster than 10 amp ones; that is my reason for using them.

If you're using the common thermal breakers, I recommend the six or seven amp models.  They take considerable over current to trip, so you'll probably get the performance desired without issue and have better protection.

+1 on the 10amp automotive style breaker.   Easy to install and easy to replace fuses.  Yep, I've replaced a few or more and never lost an engine.   I'm running DCS and the fuse is between my Post War Z-Dub and the TIU.

Chief Bob (Retired)

Hello

This is for GRJ

Have thought about making something like this  ?

While I would not think twice about pulling a motor or dropping a trans ,I do not want to burn up any of my trains

There are some of us that would like something that we could just wire up and go.

Thanks JW

Haven't really considered such a product, there's lots of commercially available solutions.

Hello

Anything that you would recommend for us ?

Thanks - JW

I doubt if your KW was the problem.  I doubt if any of the circuit boards in our trains would be able to stand even 1 amp through the circuit board.  I am not talking about current to the motor here, only current in the circuit board where your failure occurred.  The circuit breakers will protect your train wiring, but I sincerely doubt if they will protect against any short on the circuit board regardless of whether the circuit breakers are fast-acting or not.  On the other hand, TVS diodes will protect your circuit board from voltage spikes that can cause circuit board damage.

Watch the lights on your layout when a short occurs.  They will either dim from a lack of voltage or they will go out altogether, but they don't fail.

Earl

Earl is correct, the TVS is electronic protection, the good circuit breaker is to protect against other faults.  For some sensitive drive electronics I've taken to adding a PTC in series with the motor to limit motor drive current.  This protects a motor stall when a truck snags a switch or the like.  The lesson was brought home when beta testing the Cruise Commander Lite board, my K-Line Interurban set hung on a switch coming into the yard and cooked the board.  It's been stalled several times since with the PTC in the circuit, and no damage.

I concur with gunnerjohn.  I use 5 or 7-amp breakers, but I don't turn smoke on.   I can't afford fuses; they'll break you over the long haul.  I use Blue Sea marine breakers from Defender, which can mount through a round hole in a panel; they come in various sizes, in either slip-on or screw terminals.

Thanks all for your advice and insights. 

Sorry for the fuzzy photo.  On the Pioneer Zephyr trucks are shared between the loco and the cars. On this early MTH set, the affected circuit board is part of each shared truck and appears only to carry power between cars to the rear observation car which has the second motorized truck.  My concern is to preclude this occurring again. 

My wiring is largely for conventional operation. I have 18 toggled blocks, some with multiple bus connections. I have five early MTH sets and want to operate them safely.   If I understand correctly from Ron's post, it would be safe for each block to have a TVS wired in.  

Ron, is there a good source and a part number for the TVS that might be current?  Also, please forgive my electronic ignorance GunnerJohn, but is there a spec for the PTC thermistor? And a source?  Is it connected between the motor power wires or in line on the inbound or outbound sides?

Again many thanks for all the great inputs!!

I have to agree with Earl, Gunrunner John, and RJR in the immediately above exchange; I have an added comment or two.

First, I think any motor driver that isn't self-protected against a stalled motor is a poor motor-driver.  Deliberately I didn't say a poor design, because to the extent the designs are done here, I don't think they leave this country without consideration of a stalled motor.  But in China, you have at least the production engineering (and the design engineering in some cases, possibly); and in China you have the shortage of copper, which is viewed as a very serious matter by the government of China.  IE, don't add to it, Comrade factory manager.  It is what it is.  (I omit some glaring examples.)  So, to live with it, my other comments:

Second, on breakers and fuses, US fuses were eventually codified and somewhat standardized by the arms of the insurers, UL and NEC (NEC is UL standard 70, for those of you who may have thought it yet another governmental intrusion).  Just a bit of engineer black humor there , and I'll add a bit more of the same and then get back to breakers:  It used to be once UL permitted us to plug in the transformer, we as a group were pretty much trusted to wire from the other side of the transformer; and that has worked fairly well (I know of only one case where an insurer documented a train layout as starting a house fire).  Well, just recently the NEC may get you arc-fault breakers in your train room, if you carpet your basement; that's to stop house fires.  It also costs the unwary their effective ground-fault personnel protection (GFPP), which is important in a basement because of the number of grounded surfaces it contains-- to say nothing of a wet rug.   They actually sell combined ARC-GF breakers, but the GF trip level in these is 4 to 8 times the 5 milliamps used with GFPPs, a factoid which is not in the packaging, at least not in the large print.  That's enough of a seriously dangerous change that one might want to follow the controversy it has raised... your .

Back to breakers and fuses.  In US practice a fuse would not blow at less than 113% of its rating.  That did three things-- 13% is half a single number in wire sizes; the thermal circuit heating is 126%, or one single number in wire sizes; I think I am correct in saying that all the receptacle and lighter wiring (#12s for 20 amps and down) in a residential house are oversized enough to take that.  Also, in the day fuses cost, and we counted the watts marked on everything; so if we put a "full" load on the fuse (ie, 100%) we had a little margin which helped avoid "ageing" the fuse metal, which would impair its accuracy.  Finally, these margins lessened the use of pennies when no spare fuse was at hand, a very serious problem then.

I mention US practice, because in European practice, the 13% margin is not included in the rating.  A lot of the breakers mentioned here are Potter&Brumfield; I forget who owns them this week, but their last owner was headquartered in the Netherlands; P&B used a curious shuffle of ratings and rating curves to continue using the same designs but identifying them in such a way they had resemblance to European practice (you always wanted a 17-amp breaker, right?).

When breakers were introduced in residential use in 1928 (we still had fuses in a Baltimore house built about 1950), they were made to imitate the action of fuses, meaning that they do not open at all at less than 113% of rating (the definition of "at all" is 4 hours, and the UL acceptance test is run 3 hours).  A more useful rating is the test at 135% (1-1/2 single wire numbers, which IIRC the 20-amp and down receptacle circuits will also withstand).  Here the requirement is 2 minutes to open, IIRC; there is a tolerance on this.  Another figure often found is for 200%; Lionel ran its tests at this and set the acceptable time as a bit less than 30 seconds; it is important to know that breaker calibration can be changed by higher currents, such as may be caused by putting a screwdriver across the rails.  TI, who now makes the Klixon 15-amp breaker used in PW ZW's, said with use the opening slows.  Originally this breaker was used in the oven environment of a kitchen stove, I've read... so if your ZW is not yet hot, well...

Regardless, like all breakers and fuses, this is a "quick" operating device.  You can even find time-delay fuses which are "quick" operating.  The fact is, if you want a quick operating breaker, you must go to a magnetic release breaker.  But you can see why you might use the 6 or 7-amp thermal breaker suggested above where starting loads might get up toward the capacity of a 10-amp supply.

I have noticed, particularly on club layouts, where wires to the track can get rather long without noticed effect (can motors and cruise control), the circuit resistance may be high enough that breakers cannot be made to open (my club).  This brings me to my last point, the curious omission above of the Z400 as a capable welder:

Third, more or less all transformers are capable of doing damage to rolling stock features related to electronics, like circuit boards to replace wiring, and particularly so at the present 180-watt/10 ampere limit.  This by rule may be exceeded for 60 seconds.  I assume all things being equal, a new breaker and adequately large wiring may achieve this 60-second opening in all cases of PW conventional trains.  Now in the case of the Z4000, if you exceed 180 watts output for 24 consecutive seconds, it will shut off electronically.  If you badly exceed 10 amps, well for the first 24 seconds you will depend on the externally mounted 10-amp (or was it 12?) thermal circuit breaker; for this see the preceding paragraphs.  I will say that at the club this breaker never opened, nor was a short ever cleared except by running to the handles of the Z4000s (it was a requirement of membership that one could make this run from any place in the room in under 24 seconds; you should have seen me run when my twin-motored Pulmor dropped one motor screw solidly onto the 3d rail but not out of the bottom of its truck, and continued to move...  talk about welded rail!  ).  [By the way, I'd appreciate any corrections here from anyone who has actually taken a Z4000 apart; perhaps I should just have said you have to work at making it a welder, but it can be done.]

A couple of short notes:  The layout was wired with 100 feet (and 100 feet returning) out to the one central TIU by someone who apparently believed that DCS would not work with wire larger than #14.

Breakers of a fixed preset value can't be made very accurately for ratings less than 15 amps.  The smaller breakers Lionel used (such as 5 amps in the 1033) and even early ZWs used individually manually set breakers with an adjusting screw locked with "Sauereisen" (air iron auf English, using oxy- for air, I think... the thread locker of its day).  Their magnetic breaker was of course manually adjustable by user.

Another quick acting "breaker" is the variable output of the Lionel MOSFET-device solid stake throttles.  The solid-state MOSFETs are so vulnerable to overcurrent that they must be self-protected; they had single-cycle protection in the earliest PowerMasters (the 7-amp ones, except the earliest production where the protection was erroneously omitted in manufacture) using 35-amp MOSFETs.  I believe the heat-sinking gave about 2 cycles life at the 77-amp short circuit current of the matching PowerHouse 135-watt transformer.  On the other hand, in small sizes (10 amps should qualify as small (low inertia)) magnetic devices, which should have sub-cycle drop-out times (I have no way of measuring this with what I have).  The Lionel line-side shed breaker may be a sub-cycle device (gravity drop-out).  There is no inherent necessity for MOSFETs to break circuit at current zeros, but there may be a concern for voltage peaks driven by source inductance in this situation.  IMO, the shed contact looks like it will break the heaviest current to be expected.

--Frank

Whether you agree that motor drivers should be short circuit protected, the facts on the ground indicate any such protection is not foolproof.  I have replaced the drivers and/or boards in pretty much every style of popular command electronics due to over-current or shorts in the motor circuit.  That includes the Lionel DCDR, DCDS, and their new RCMC Legacy board.  Both the ERR CC-Lite and the CC have come in with cooked drivers, one CC-Lite I cooked myself.  The DCS electronics hasn't fared any better, I personally had a motor stall with a thrown traction tire using the 5V PS/2 board.  That board was toast before I could get to the power switch, maybe five seconds at the most.  I've got a PS/3 board on the bench now with smoked motor drivers.

CHASP, I use this TVS, 1.5KE36CA at Digikey, and the PTC I use is also from Digikey, I size it for the motor and the board that's driving it.  For the Cruise Commander Lite, I use a 1.1A hold, 1.6A trip PTC.

Frank, regarding your mention of combined arc-fault/GFI breakers and their shortcoming, would the solution, if you have an arc-fault breaker, be not to have the GFI protection in the breaker, but to use a GFI receptacle in the first outlet box on that circuit?

Thanks for alerting me to a change in NEC re arc-.fault breakers

To all, thanks for all the great insights.  To GUNRUNNERJOHN...sorry I got the handle wrong the first time...I also overlooked the TVS specification on your excellent wiring diagram.  And to Frank, thanks for an exceptional combined history and engineering tutorial!  I'm convinced that I'll use the GUNRUNNERJOHN wiring diagram with a 5-7 amp fuse as insurance and see how that works, fully understanding from Frank, et al, that there are just no guarantees!  Again, thanks all! 

ChasP posted:

 

Ron, is there a good source and a part number for the TVS that might be current?  Also, please forgive my electronic ignorance GunnerJohn, but is there a spec for the PTC thermistor? And a source?  Is it connected between the motor power wires or in line on the inbound or outbound sides?

 

Chasp,

I see John beat me to it.  Have fun!