Trains.com

ZW-Wiring = Scary

15060 views
50 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    August 2007
  • From: North Kingstown, RI
  • 132 posts
ZW-Wiring = Scary
Posted by clickmatch on Monday, August 27, 2007 1:39 PM

Hi I'm new here.  I am excited though, I have my Grand Dad's trains out of the closet now that our addition is finished and I now have the space for the table. One of these early steps involves the nasty dangerous cord coming out of my ZW Transformer.

I searched around, but I want to be extra cautious as this thing scares me... it's like newer electronics seem normal, but these old transformers are heavy bulky.. I feel like they amplify power. Big Smile [:D]

Anyways, I bought this "power tool replacement cord". 14 Gague wire.

It's a 3-prong plug. I checked out the inside of the ZW and I see two solder points. A top and bottom. The cord I have has 3 wires. Green, white, black. I am assuming I am to wire the green and black together (common and ground) and solder it in one spot (not sure top or bottom) and the white (hot) in the opposite.

Please let me know if this is right or wrong, or steer me in the right direction. Thank you in advance for your advice.

  • Member since
    January 2007
  • From: Berea, OH
  • 362 posts
Posted by jmkk on Monday, August 27, 2007 2:00 PM
  From what I know about wiring (white is common ) (black is hot) (green or bare copper is ground) If you put black and green together your going to cause a dead short. I know in a new pannel box there is a green screw to connect the common to the ground  I would buy a new cord wit only two wires. Hope that helps. You will get many answers on this forum,many with more knowledge than me.

Jason   

 B&O  =  Best & Only

  • Member since
    March 2004
  • From: Bensalem, PA
  • 194 posts
Posted by Dave45681 on Monday, August 27, 2007 2:58 PM

You should probably go to your local home supply or electronics store and buy a 2 prong plug (if possible, one with both blades the same width).

Without re-designing the internals of the ZW, the third prong or wider blade cannot help you here.  (It can only constrain you to re-wire if you ever need to phase this transformer with another one) 

You can probably use the wire you already have if you were to remove the three prong plug, unless you want to return it and just get regular 2 conductor wire.

Using a plug with equal width blades is beneficial if you ever use more than one transformer together at a later time - this is referred to as phasing.  You probably don't need the details right now, but it's a benefit to be able to invert the wiring of the transformer when phasing - which is easiest accomplished by reversing the plug at the wall.

It doesn't sound like you are using more than one transformer right now, but I thought I would provide the brief background for you.

Good luck, and welcome to the forum!

 

-Dave

  • Member since
    January 2005
  • From: Lake Worth FL
  • 4,014 posts
Posted by phillyreading on Monday, August 27, 2007 3:08 PM

From what I know about the older ZW's you need only two wires to complete the circuit.  Black in A.C. wiring is always hot!  White is the nuetral or return wire.  Green is always the ground.   Other things to look for in the ZW include taking the cover off and looking at the roller wheels, condition of the wheels and how much dirt is on the top of the windings, you may have to clean the windings.

D.C. wiring like in a car; black is negative, red is hot, there is  no ground like in A.C.  For car stereo the black wire gets hooked to the frame as a cheap way to wire speakers for your car stereo.

Lee F.

 

Interested in southest Pennsylvania railroads; Reading & Northern, Reading Company, Reading Lines, Philadelphia & Reading.
  • Member since
    December 2003
  • From: Central PA
  • 2,536 posts
Posted by jefelectric on Monday, August 27, 2007 3:35 PM
 clickmatch wrote:

Hi I'm new here.  I am excited though, I have my Grand Dad's trains out of the closet now that our addition is finished and I now have the space for the table. One of these early steps involves the nasty dangerous cord coming out of my ZW Transformer.

I searched around, but I want to be extra cautious as this thing scares me... it's like newer electronics seem normal, but these old transformers are heavy bulky.. I feel like they amplify power. Big Smile [:D]

Anyways, I bought this "power tool replacement cord". 14 Gague wire.

It's a 3-prong plug. I checked out the inside of the ZW and I see two solder points. A top and bottom. The cord I have has 3 wires. Green, white, black. I am assuming I am to wire the green and black together (common and ground) and solder it in one spot (not sure top or bottom) and the white (hot) in the opposite.

Please let me know if this is right or wrong, or steer me in the right direction. Thank you in advance for your advice.

 

For your own safety, I would recomend that you have a professional install the cord.  From your comments it seems that you have had no experience with 120 volt AC and lack the knowledge to accomplish the job.

Not trying to be a wise guy, just don't want you to hurt yourself or burn down your house.

John Fullerton Home of the BUBB&A  http://www.jeanandjohn.net/trains.html
  • Member since
    February 2007
  • 928 posts
Posted by bfskinner on Monday, August 27, 2007 3:46 PM

clickmatch,

Normally I stay out of discussions of wiring, deferring instead to Bob Nelson (lionelsoni) and certain others; but since I have rewired/rebuilt several postwar transformers, including two ZW's, maybe I can add a little.

My local parts supplier recommends, and I always use, black rubber-insulated "Heater Wire" available at Home Depot or Lowe's, among other sources. As stated above you want two-conductor wire with non-polarized plugs. (The prongs on the plug should be identical; that is, the same width.) You can't hook it up wrong. You should not use a third or "ground) wire.

For a ZW, I use 16 gauge. (It also comes in the small 18 gauge but get the larger 16 ga.) If it has little metal terminals, simply snip them off, strip off the insulation a quarter of an inch or so, and "tin" the ends with solder. Keep things neat and tight so that the tinned wire will pass through the grommets where the connections are to be made.

The most important thing is to put a knot in the cord inside the case. Its position is somewhat critical: it's function is to act as a "strain relief" by being positioned such that if one pulls on the cord, the knot jams against the inside of the case before any stress is placed on the terminals where the cord connects to the primary coil. This is absolutely essential. You may be able to use the old cord as a guide, but it's not rocket science and the correct position of the know should be self-evident once you understand what it is for. Never operate a transformer with a frayed or cracked power cord.

Jefelectric's post popped up while I was writing this. I wouldn't argue with him one bit.

Good luck and welcome.

bf
  • Member since
    August 2007
  • From: North Kingstown, RI
  • 132 posts
Posted by clickmatch on Monday, August 27, 2007 4:00 PM
 jefelectric wrote:

For your own safety, I would recomend that you have a professional install the cord.  From your comments it seems that you have had no experience with 120 volt AC and lack the knowledge to accomplish the job.

Not trying to be a wise guy, just don't want you to hurt yourself or burn down your house.

I'm not a total noob, here. Just the ZW's age makes me nervous. I have installed some switches and plugs, and even replaced the main breaker in my house once. I'm just trying to be on the safe side.

That being said, the comments here are enough to let me understand what I need to do. My reasoning was that if it could be grounded, that would be better, but if not, the comments show me that's not the way to go. My issue too, was that home depot had only a 3 prong plug, but thanks to the other comments now I know to go seek out other departments to see if it's somewhere else in the store.

I also think the 2 wire plug will be easier to knot than the 3 prong with the 3rd wire being unused anyways.

Thanks for all your comments!

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Monday, August 27, 2007 4:39 PM

Rewiring the transformer with a two-wire cord is of course a perfectly reasonable approach.

However, I have replaced the cords of my transformers with the same kind of three-wire cords that you have.  The white (grounded conductor) and black wires replace the two original wires.  I connected the green (equipment ground) wire to the transformer common, which would be the U terminal of a ZW.  This is the terminal that is usually connected to the outside rails.  It is the layout common and is often loosely referred to as "ground".  By connecting it to the green wire, I make it ground literally.

This is the sort of thing that the green wire is intended for.  It is normally connected to any parts of the equipment that a person might normally touch, like the metal cabinet of a clothes washer or a computer.  Any fault that might occur that would otherwise place a dangerous voltage on that cabinet will instead blow a fuse or trip a circuit breaker, protecting the user from electrocution.  So all my track is similarly protected against accidental connection to the 120-volt power line.

(Note that the colors used in other countries' wiring are often different from ours.)

Bob Nelson

  • Member since
    April 2003
  • 305,205 posts
Posted by Anonymous on Monday, August 27, 2007 4:53 PM

This is as easy as replacing a light bulb. Just note where everything is connected and replace the cord with the same type. Don't add anything else. 

Now if you want to play it safe just order your replacement cord from here > CORD

 You can't go wrong for $5.50 you get the proper replacement cord.

  • Member since
    January 2007
  • From: Southern MD
  • 315 posts
Posted by USNRol on Monday, August 27, 2007 5:48 PM

I would submit since the ZW case is Bakelite and doesn't conduct electricity there is no benefit to be achieved in switching to a grounded plug where as Bob points out the green wire would normally be connected to the chassis/case.  Bob's description of connecting the green wire to the xformer common or "U" terminal would serve only as a redundant source for earth ground potential in most cases where the line neutral (White wire) is attached to a grounded bus bar in the circuit breaker panel.  Edit Also if you try to wire it as Bob wires his, you'll need to be certain your polarity is correct; ie. black hot wire to hot side of transformer and white wire to the common side otherwise you'll be wiring up a direct short guaranteed to produce blackened and charred receptacles in your train room, and tripped breakers in your utility room.

Edit: My mistake Bob, I guess I was thinking there was an electrical connection between the Common "U" and one side of the Primary winding, and that wouldn't be right.  Your point regarding polarity and phasing would be the only concern, and irrespective of the grounded "U". 

The advantage of using the green wire for grounding is that at every point throughout a properly wired house the green wire (Bare copper wire) is attached to a grounded item (or at least what could best be described as ground potential) such as junction boxes, appliance chassis', lighting fixture housings, copper plumbing, etc.  And in any case where that ground is required to shunt away any dangerous voltage, the voltage would have an easier or at least more possible paths to ground.  Although the Neutral white wires are at ground potential in most homes, they are only physically connected to such all the way back at the circuit breaker panel.

I recommend the non-polarized two pronged repair method. Quick easy and done.

Roland

  • Member since
    February 2004
  • From: Rolesville, NC
  • 15,416 posts
Posted by ChiefEagles on Monday, August 27, 2007 6:16 PM
 lionelsoni wrote:

Rewiring the transformer with a two-wire cord is of course a perfectly reasonable approach.

However, I have replaced the cords of my transformers with the same kind of three-wire cords that you have.  The white (grounded conductor) and black wires replace the two original wires.  I connected the green (equipment ground) wire to the transformer common, which would be the U terminal of a ZW.  This is the terminal that is usually connected to the outside rails.  It is the layout common and is often loosely referred to as "ground".  By connecting it to the green wire, I make it ground literally.

This is the sort of thing that the green wire is intended for.  It is normally connected to any parts of the equipment that a person might normally touch, like the metal cabinet of a clothes washer or a computer.  Any fault that might occur that would otherwise place a dangerous voltage on that cabinet will instead blow a fuse or trip a circuit breaker, protecting the user from electrocution.  So all my track is similarly protected against accidental connection to the 120-volt power line.

(Note that the colors used in other countries' wiring are often different from ours.)

Sign - Ditto [#ditto] 
Listen to Bob, I have learned a lot [and I thought I was electrically inclined as took a college course in it] from him.  Sometimes he gets "above my head" but if asked to "splain it", he will.

 God bless TCA 05-58541   Benefactor Member of the NRA,  Member of the American Legion,   Retired Boss Hog of Roseyville Laugh,   KC&D QualifiedCowboy       

              

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Monday, August 27, 2007 6:41 PM

Roland, there is no connection between the primary and secondary windings of the transformer (at least there's not supposed to be one).  So it doesn't actually matter which of the black and white wires is connected to which end of the primary winding, except with regard to the phase of the output voltage.  So, when a transformer like the ZW is supplied from a two-wire cord properly wired only to the primary, the output circuits are isolated and floating.  There is therefore no obstacle to grounding the outputs as I described; and the advantage is as I claimed that one can be (more) confident that the track is not at a dangerous voltage.

If the transformer were wired as you describe, with the U terminal connected to the white wire, simply reversing the (two-pin) plug would put 120 volts on the U terminal and therefore the track, which would be very dangerous.  I'm sure Lionel wouldn't have gotten away with that into the postwar period, not that they had any reason to try it.  Nevertheless, they did sell DC reducers before the war with exactly this feature, both for 110 volts and 220 volts.

In summary, if you do connect the green wire to the U terminal and a circuit breaker trips, it is because the transformer is already faulty, having lost the important isolation between primary and secondary.  In that case you are better off with the circuit breaker tripped, the transformer dead, and no voltage, high or low, on the track.

As for the phase of the output voltage, my policy is to make the output be in phase with the input.  This then guarantees that all the outputs will be in phase with each other when the primaries are plugged into the same 120-volt circuit.  With the U grounded, I simply turn one of the outputs all the way up and measure the voltage between it and the black wire of the line cord.  If that is about 100 volts, I've got it right.  If it is more like 140 volts, I reverse the primary connections.

Bob Nelson

  • Member since
    January 2006
  • 149 posts
Posted by pgtr on Monday, August 27, 2007 11:05 PM

 clickmatch wrote:
My issue too, was that home depot had only a 3 prong plug, but thanks to the other comments now I know to go seek out other departments to see if it's somewhere else in the store.

Actually you can find replacement 'lamp' cords w/ the business end pre-stripped all packaged up and ready to go. These are modern vinyl insulated UL listed cords with a molded plug that is polarized.

Cheaper and easier to find yet - simply go to a discount store like Walmart and purchase an extension cord for LESS than the replacement cord I mentioned above and snip off the w/ the recepticles and toss it. About $2 or $3? These are had in various lengths and in brown or white but not black. Again the molded plug will be polarized. 

I'm now in the habit before tossing out things like say an old broken VCR or other home gizmo beyond repair, of snipping the cord off (usually black) and keeping a stash of replacement cords (or DC wall warts) for whatever...

  • Member since
    May 2005
  • 382 posts
Posted by trigtrax on Tuesday, August 28, 2007 5:36 AM

ZW's were produced before the use of redundant ground (Green Wire) They had a 2 prong non-polarized plug.

The whole idea of a transformer is it isolates the primary from the secondary circuit. If you're using multiple transformers and some have polarized or three wire plugs then you need your ZW to be wired in phase. On the old cords the ribbed wire would be the common connection and the smooth wire was hot. Wire the black to the terminal the smooth wire was at and the white to where the ribbed wire was. You can attach the green to the metal chassis of the ZW, but I don't recommend putting it on the U-Post. The reason being you will then  fix this post to earth ground and if you ever add an out of phase transformer you'll create a short circuit.

You need to remember that through the years much of this equipment was repaired in Hobby Shops by folks who may not even have been aware of standard wiring.

 

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Tuesday, August 28, 2007 6:41 AM

If the out-of-phase transformer that you add has a two-wire cord, its secondary is (should be) isolated, as you say; so it will simply be out of phase with the three-wire transformer, but no short circuit.  If the out-of-phase transformer that you add has a three-wire cord, wired the way I described, both transformer's U terminals are grounded; so connecting them together creates no short circuit, just outputs that are out of phase.

Out-of-phase outputs are avoided, as I described, by making sure that the outputs are consistently in phase with the inputs, so that they will be in phase with each other.

Bob Nelson

  • Member since
    August 2007
  • From: North Kingstown, RI
  • 132 posts
Posted by clickmatch on Tuesday, August 28, 2007 7:45 AM

 trigtrax wrote:
You can attach the green to the metal chassis of the ZW, but I don't recommend putting it on the U-Post. The reason being you will then  fix this post to earth ground and if you ever add an out of phase transformer you'll create a short circuit.

When you say chassis, do you mean one of the two metal parts that "hold" the coils up? (It's held together on top by two clips)

What if I know I'll only ever use one transformer? I have 96 pieces of O-track, a lionel barrel loader which I'm not sure if it will make it on the layout, and I'll probably put LEDs all over the place (50-100?) and I think I have a whistle house and a couple of towers. Does all that warrant another transformer? (I don't think it does)

So I guess the question is what is the benefit from using the 3 prong over the 2, and which stance (chassis or U post) is the safest if the 3 prong is used?

BTW, I've been on many websites in my day, and I'll say this community is by far one of the best in terms of response and helpfulness. Wink [;)]

  • Member since
    December 2005
  • From: Sunny So. Cal.
  • 3,784 posts
Posted by dbaker48 on Tuesday, August 28, 2007 8:10 AM
Please, Please, Please.......  For the safety of your family, Go back and listen to what lionelsoni speaks.  HE knows what he is talking about, OR take jefelectric's advice.  How much is risk, and what is the benefit?    Family Safety vs. an old xfmr?????   This is the most sensitive and dangerous area of toy train operation (re: safety), don't take a short cut.  Those two guys ARE experts.  Please heed their advice.

Don

  • Member since
    February 2007
  • 928 posts
Posted by bfskinner on Tuesday, August 28, 2007 12:13 PM

clickmatch,

If you are confused you have every right to be. Bob Nelson always has cogent reasons for what he recommends and he is certainly well-educated and knowledgeable, but sometimes his reasons for doing things may differ somewhat from your needs. As somebody mentioned he favors Lionel Type Z transformers which have metal (conductive) cases; whereas you have a Type ZW transformer which has a plastic (non-conductive) case. If you fully understand Bob's reasons and grasp his concerns, you may want to follow his method. EDIT: I am indebted to Bob Nelson for pointing out that the Lionel Type Z transformer in fact also has a plastic (Bakelite) case.

Be advised, however, that if you follow the advice of jefelectric and dbaker48, and take your ZW to an Authorized Lionel Service Center, they will almost certainly re-equip it with a two- (not three-) wire line cord, non-polarized. The cord should be capable of carrying 15 amps or about 1725 watts without overheating. Lionel used two-wire cords from the get-go and continued to use them until they introduced their new-fangled "electronic transformers," at least some of which use polarized two conductor cords. As far as I know, their service stations still stick with the two-wire, nonpolarized cords when rehabilitating postwar ZW's.

One thing you might want to consider is: when it comes time to sell your ZW, do you want it to be a standard two-wire type or a non-standard variety?

The next thing you want to think about is the circuit-breaker. Is it any good? Does it need replacing? Either way, you will want to consider is placing fuses (or modern, fast-acting circuit breakers) between the transformer and the track -- not to mention lionelsoni's personal favorite, the TVS. And whatever you do, be sure to tie the knot so that there is always slack on the line cord inside the transformer. Smile [:)]

There is a world of material, including books, videos and DVD's on the subject of repairing/rebuilding postwar ZW's. There is also at least one other major forum that you might wish to check out and compare their advice with ours; and especially that of their "house guru" (Jim Barrett). One response does not necessarily fit all situations. Use the "search" or "find" functions on the forums and you can learn a lot in a hurry; but be advised that while much of the advice is excellent, some is incorrect, misinformed and opinionated pap, IMHO.

The title of your original question is illuminating. At least one informed person has publicly called the postwar ZW "an electrocution just waiting to happen,"*  and some folks recommend them only for operating accessories and/or post-war era trains. They don't always play well with others, especially new modern electronic locos and sound systems. Under some circumstances a postwar ZW makes a pretty good arc-welder.

* I have two postwar ZW's that I have completely rehabilitated and neither has killed me yet; but I did a lot of research before plunging in, and followed video-taped instructions line-by-line.
bf
  • Member since
    May 2005
  • 382 posts
Posted by trigtrax on Tuesday, August 28, 2007 2:25 PM

When you say chassis, do you mean one of the two metal parts that "hold" the coils up? (It's held together on top by two clips)

Chassis for our purpose means metal parts not connected to either the primary or secondary circuit.

It's time for some basic AC wiring. In a 115 volt house circuit current electrical code is a three wire system. Black is hot. White is common. the 115 Volts appears here and in working devices all the current runs in these two wires. The green wire or earth ground is just that. It's attached to mother earth through either a water pipe that runs out to the supply through the dirt or a special copper plated steel bar pounded into the dirt. The white and green wires are connected at only one point, in your power distribution or circuit breaker box. The purpose of the green wire attached to equipment chassis is that in the event of failure, hot shorts to chassis, you'll blow the fuse/circuit breaker and you won't find yourself connected between 115 volts AC and your zero volts faucet handle.

This green line was never meant to be a part of an active circuit. It's a safety device. For the ZW it's less important because the whole thing is covered in Bakelite. For the KW the bottom is metal but rarely touched. By attaching the Green to your outside rail you are defeating the isolation value of the transformer because you've got one side of the high voltage exposed all over your board. Now in a perfect world that might not matter. But there could be failures in multiple transformer systems that would pump all your AC current through your trains and out to ground. You'll smoke those choo-choo's before your circuit breaker opens.

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Tuesday, August 28, 2007 6:31 PM

The case of the Z transformer is also Bakelite.  The metal frame inside is actually connected to a point between the fixed and variable windings, which is also where the circuit breaker is located in the circuit.  I do not see any good reason to connect the equipment ground to that point and do not propose doing it.

I do propose connecting the equipment ground to the U terminal, no matter how many transformers are used.  This is just the sort of thing that the equipment ground, the green wire, is intended for.

Suppose that you have a microwave oven with a metal case.  If it were powered from a two-wire cord and the circuits connected to those two wires inside the case were completely isolated from the case, as they usually are, there would be no danger to you from touching the case.  If the wire in the two-wire cord that is plugged into the white wire of your house wiring came to touch the inside of the case, you would still not be in danger, since that side of the power circuit is grounded at your service entrance.  But, if the other wire, the one that is plugged into the black wire of the house wiring, came into contact with the case, the entire outside of your microwave oven would become very dangerous to touch, since it would be at a potential of 120 volts relative to ground.

The microwave oven however has three wires, not two, in its power cord.  The third, green, wire is deliberately connected to the case and plugs into the green (or bare) wire in your house wiring, which is connected to ground at the service entrance.  So if the black wire contacts the case, the circuit breaker trips, shutting off the 120 volts that would otherwise be there.  (In the case of the microwave oven, the green wire also protects you from the very high voltages that the oven's circuits generate in normal operation, which might also accidentally contact the case.)

Now consider the transformer and train layout.  The track, like the case of the microwave oven, is completely isolated from the black and white wires of the cord.  But, like the microwave oven, if the black wire should come into contact with the secondary side of the transformer through some failure, all your tracks will be at a potential of around 120 volts.  This is of course dangerous.  Connecting the green wire to the U terminal insures that, if this happens, the house-wiring circuit breaker will trip and protect you from a shock the next time you touch the track.  You are also protected if some other part of the power-line wiring feeding your layout gets connected to the normally low-voltage train wiring, even if this happens outside your transformer.

It seems to me that, unless you are trying to preserve the collector's value of your transformer, you can only improve things by grounding the secondary circuits to make your layout wiring safer.

Bob Nelson

  • Member since
    February 2007
  • 928 posts
Posted by bfskinner on Tuesday, August 28, 2007 7:30 PM

Bob (lionelsoni)

I stand corrected on the composition of the case on the type Z transformer. Were they always that way? I haven't actually seen one in years, but I'd swear I have seen some Lionel transformers with metal cases and I thought the Type Z (not to be confused with the postwar ZW) was among them.

In any event, it supports my other point that much of what is on the internet in general and the forums in particular is pap -- including some of my authorship.

bf
  • Member since
    January 2007
  • From: Southern MD
  • 315 posts
Posted by USNRol on Tuesday, August 28, 2007 7:34 PM

Bob, What happens to your trains or anyone touching the center rail if 115vac accidentally shorts to the center-rail side of your layout?  Is the resistance in the secondary winding low enough so as to offer protection by way of the grounded "U"?  Just pondering the pros/cons of floating trackage vs. grounded outer rails. 

Roland
P.S. see edit to my previous post

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Tuesday, August 28, 2007 9:19 PM
I've never seen a metal one.  The top plate, with the markings on it, is aluminum; and the base is steel.  However, both of these are screwed to the Bakelite case and not connected electrically to anything inside.

Bob Nelson

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Tuesday, August 28, 2007 9:38 PM

If the transformer is in the off position, I'm afraid you'll get 120 volts on the center rail and across any load sitting on the track.  Otherwise, I think the transformer's output impedance would be plenty low enough to keep the track voltage down while you have a race between the house circuit breaker and the transformer's circuit breaker.  If the transformer's trips first, then you will again get 120 on the center rail.

You have raised a good point, Roland.  I think the best solution would be to keep the ground and add transient voltage suppressors to the track.  That way you're protected from overcurrent and from dangerous voltage either between the rails or from the rails to ground.  Another good practice would be to feed the entire layout from a ground-fault interrupter.

 

Bob Nelson

  • Member since
    January 2006
  • 149 posts
Posted by pgtr on Wednesday, August 29, 2007 10:40 PM

...oh yeah and for the really paranoid who operate their ZWs near water... before my better half threw out a defunct hairdryer I snipped off the cord. Guess what's on the plug end of a hair dryer cord? A little gfci device. :) Just another cheapo source for a replacement cord.

 

 

  • Member since
    July 2003
  • From: North Texas
  • 5,707 posts
Posted by wrmcclellan on Thursday, August 30, 2007 12:23 AM

Interesting point made by Bob about grounding the secondary common.

When I have put a 3 wire cord onto a ZW, I attach the green ground wire to the aluminum transformer core frame as it is directly attached (metal screws) to the exposed metal mounting plate on the bottom of the ZW.

Regards, Roy

  • Member since
    August 2007
  • From: North Kingstown, RI
  • 132 posts
Posted by clickmatch on Thursday, August 30, 2007 7:40 PM

Ok, I opened her up to do the cord install, and actually paid more attention. I know I need to clean up the main coil and all that, but I'm wondering if this thing needs more than just a cleaning up. Here's some shots. In particular the lower coil is very hard and looks... just kind of wrong. But for all I know it's resilient and will work fine. I just figured I'd show you all some pictures before I make my own decision on it.

Thanks =)

 

 

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Thursday, August 30, 2007 10:36 PM
I wouldn't expect either coil to be "resilient".  They're densely wound copper wire with some kind of insulating coating, in the case of the primary wrapped in paper saturated with more insulating stuff that hardened when it dried.  The transformer in your pictures looks about right to me.

Bob Nelson

  • Member since
    May 2005
  • 382 posts
Posted by trigtrax on Friday, August 31, 2007 4:23 AM

I think you should consider the way transformers are constructed, tested, and the modes of failure.

The primary and secondary are insulated wire wrapped around a core or bobbin. After the winding the whole assembly is dipped into some form of epoxy or varnish and baked. This fills the voids between the wires, adds dielectric strength, and keeps things from moving. The core is then fitted to the laminations which have also received an interleaf varnish to keep eddy currents down.

Transformers then get a hi-pot or leakage test. Usually 1500 volts is applied between the windings and lamination and the current flow is measured and must be below some level.

There are two failure modes for a transformer. First, a winding opens, no current flows. The transformer just goes dead. The End goodbye.

Second a winding or group of windings short. In that case the short represents a zero resistance load. Current increases, heat rises and poof.. Smoke. You can smell a bad winding years after it failed.

As far as collector value, transformers really don't have any. They've been cranked out in quantity year after year and even the glorious ZW is now dropping in value.

I know in recent years this TMCC earth ground has been all the rage. The magic pill to solve signal problems. But the engineering of original trains never intended for the circuit to be anything but floating. A primary example of this is the fixed voltage windings of the KW. The 20 volt secondary is tapped to provide a 6 and 14 volt output. Proof against this Earth Ground arrangement.

 

  • Member since
    December 2001
  • From: Austin, TX
  • 10,096 posts
Posted by lionelsoni on Friday, August 31, 2007 4:26 PM

You'll have to fill in a few steps in your argument for me.  I don't see how having terminals C and D, respectively 6 and 20 volts relative to U, so 14 volts between them, proves that you can't or shouldn't ground U.

I disavow all knowledge of TMCC.

Bob Nelson

Join our Community!

Our community is FREE to join. To participate you must either login or register for an account.

Search the Community

FREE EMAIL NEWSLETTER

Get the Classic Toy Trains newsletter delivered to your inbox twice a month