Ogaugeoverlord,
Thanks for the prompt reply. My question concerned the “corrected” values in the chart. As I said, I can’t see the chart. 18 VA is only about eighteen watts. I just can’t figure out what the question was to which 18 VA was the answer.
A&Y, the ZW is certainly robust and electrically simple; but I wouldn’t go so far as to call it bulletproof or even entirely safe. Like all of Lionel’s older multiple-output transformers, it has the potential (literally) of burning up itself and the wiring of the layout that it is connected to if any of the outputs become connected together while set to different voltages.
This happens because Lionel used only one circuit breaker, located in the common return of the transformer. So Lee’s proposal to add external (or even internal) circuit breakers is a good one, although I would not use fast-acting ones for the purpose of protecting the trains.
Fuses and fast-acting circuit breakers are often mentioned in the forum as useful for protecting modern electronics-intensive locomotives. Fuses blow when you draw too much current through them. By the time that a locomotive draws excessive current, it is already damaged; so how can a fuse protect it?
A short circuit is not a tidy event in which the faulty path suddenly appears and remains. If it were, the locomotive would just see a sudden drop in voltage to zero, which is not harmful; and that would be the end of it. In real life, the short circuit comes and goes many times in a fraction of a second before it settles down. Switches do this too; it’s called “contact bounce”. Each time the short circuit closes, it draws a lot of current from the transformer. Then, when it opens, the output inductance of the transformer tries to keep that current flowing. That’s what inductance does. With the short circuit open, that current is flowing into an impedance much higher than it had an instant ago. In accordance with Ohm’s law, the voltage on the load therefore rises, possibly to hundreds of volts. This is what damages the locomotive, the aftermath of the short circuit, not the short circuit itself.
lionelsoni wrote,
A better approach is to eliminate the voltage spikes directly, using something like a transient voltage suppressor, or “TVS”, installed across the track (not in series with it and not necessarily between the track and ground).
Interesting and thoughtful post, but I’m still a little unclear and I suspect others are too.
Do I presume correctly that a TVS has only two contacts and that polarity doesn’t matter? If so, could you
(1) give two points inside a locomotive and
(2) two on or near the track to connect the TVS to?
(3) By “not necessarily between track and ground” do you mean “true earth ground?”
(4) Is the TVS sacrificed when it has done it’s job?
Thanks in advance.
Afterthought: is this a picture of the beast?
http://rocky.digikey.com/WebLib/General%20Semi/Web%20Photo/1.5KE%20AXIAL%20SERIES.jpg
lionelsoni wrote,
A better approach is to eliminate the voltage spikes directly, using something like a transient voltage suppressor, or “TVS”, installed across the track (not in series with it and not necessarily between the track and ground).
Interesting and thoughtful post, but I’m still a little unclear.
Do I presume correctly that a TVS has only two contacts and that polarity doesn’t matter? If so, could you
(1) suggest two points inside a locomotive and
(2) two on or near the track to connect the TVS to?
(3) By “not necessarily between track and ground” do you mean “true earth ground?”
(4) Is the TVS sacrificed when it has done its job?
Thanks in advance.
Yes, the TVS has only two terminals; and that could well be a picture of one. There are two kinds, unidirectional and bidirectional. Since we’re dealing with AC here, we want the bidirectional. That’s what the “CA” suffix means.
If connected to the track, the TVS goes across the rails. That is, you connect one TVS lead to the outside rail and the other to the center rail. If you put it inside the locomotive, connect it to the points in the locomotive that connect to those rails, that is, to the frame (wheels) and to the pickup.
Yes, by ground I meant the Earth. Of course, you might have grounded your layout common, in which case there is no difference. However, connecting a TVS from one rail to ground has no real effect if the layout is not itself grounded.
No, the TVS should survive. You can burn them out; but there is not enough energy in the sort of spikes we are after to do that. The 1500-watt rating applies only for a very short pulse. The only way one is likely to be damaged is if you use a TVS with too low a voltage rating for your track voltage. If you think 36 volts might be marginal, you can simply go up a step, to 39 volts. (Remember to multiply the RMS voltage of a sine wave by the square-root of 2 (1.414) to get the peak voltage.)
Hey Bob N.
Good point to bring up and where would a person buy the TVS units here in south Florida? Does Radio Shack carry these items?
Lee F.
lionelsoni answered a number of questions on 12/21/2007 @ 12:25 PM.
Thanks again Bob. Clear as a bell. I have made a hard-copy.
Not Radio Shack. I have had good luck with and fast service from Mouser. Their full part number is 625-1.5KE36CA-E3.
Okay Bob, acknowledging your essay I will concede to a “bow and arrow proof” ZW as opposed to “bulletproof”. [:)]
Based on my experience with heavy use for 15 years using three ZWs on a 13x28 5-track “run and display” airborne layout and everything I have read and heard over 40 years of o-gauging including from knowledgeable repair folks, I rate the pw ZW as having an excellent safety and performance record. If you have some factual examples of failures as regards safety or performance you should cite them? And, there is no reason a properly reconditioned one is unsafe to use if, the transformer is protected by properly sized modern external breakers or a proper fuse block.
As regards protecting engine circuit boards, I agree, neither breakers or fuses will protect the mini-sized and fragile motor wires or solder traces in the engines circuits. The supressers you note above are inexpensive and simple to connect on the layout. Internally on the engine is more complicated if that is one’s preference.
Aside from the observation that connecting two outputs of the same transformer is tantamount to short-circuiting the part of the transformer secondary between the rollers, with no circuit breaker in the circuit, I do have a few bits of corroborating evidence:
–The warning in the KW-transformer service manual, which could equally well apply to the other models: “Note that the circuit breaker does not protect binding post combinations A-B, B-D and C-U.”
–A couple of Z transformers bought with burned sections in the middles of the secondary windings. The only way excessive current could have flowed there and not elsewhere in the secondary is through the rollers, that is, from one output terminal to another through rollers set at different voltages. (I rebuilt and am using the better of the two.)
–My own measurements of high currents between output terminals, made very briefly to avoid damage. I measured 30 amperes with a 10-volt difference on one of my Z transformers, twice what would have tripped the circuit breaker had it been in the circuit.
Bob,
Thanks for all of your thoughts and expertise on the subject.
I’ve been using my ZW in exactly the manner you warn against, and has the potential for two different voltages to be bridged by locomotive rollers.
In order to minimize the potential for damage, I always try to either move from a powered to an unpowered block, or at least aproximately match the voltage between the two and keep their time bridged short.
Based on your advice, however, I’ve just purchased a pair of fuse holders from Radio Shack, as well as some 8 amp slow-blow fuses. I’ll be shopping around for 15 amps-8 amp was the largest Radio Shack had. I’ll put these on each of my “hot” track feeders.
I also purchased a fuse holder to use with the Z on my Christmas tree layout right now.
I’ll be getting some voltage supressors from Mousser, and hopefully some 15A slow-blow fuses.
At the risk of getting into a “My transformer authority can whip your transformer expert” or ad hominem argument, there are sources who agree with lionelsoni. Consider this quote:
Why did they stop making powerful transformers?
Initially it was due to lack of demand during the 1960’s when just selling trains was a challenge. In 1973 the Consumer Products Safety Commission cracked down on General Mills on transformer design. They felt for some reason that the ZWs and others were “Electrocution hazards waiting to happen”. They came up with lots of new rules and regulations making the manufacture of these transformers near to impossible and financially
unrealizable. To add to this Underwriters Laboratory, which approves products as “safe” for insurance purposes, recently would not approve a redesigned ZW II transformer from LTI. Apparently heat dissipation problems occurred with the large coil. As a replacement Lionel developed the “TrainMaster” system profiled later in this section. Neil Young, the popular singer and Lionel collector, has been contributing greatly to this project. More at http://www.faqs.org/faqs/model-railroad-faq/tinplate/part2/
A useful site, although some of the material is a bit dated. Then again so are the postwar ZW’s.
Rightly or wrongly, it is clear that the postwar ZW could not get UL approval for use as a toy train transformer in this day and age. Is this more Big Brother? A definite maybe.
It is certainly annoying that everything from the air we breathe to the water we drink to the medicines we ingest seem to be fodder for the “Chicken Littles” of the world, and expecially those in California. While it is tempting to dismiss them, one might be mindful that many of those who pooh-pooh
Is it wise to use the TVS with both old and new transfomers?
“Rightly or wrongly, it is clear that the postwar ZW could not get UL approval for use as a toy train transformer in this day and age.”
The postwar ZW was not UL-approved at any time, nor were the Z or the KW. Max output for qpproval seems to have been 150 watts. (This is most likely the reason for the TW, which had two coils and thus 175 watts total rating, but with neither coil exceeding 150 watts.)
I don’t have a specific source for this, but it seems clear from looking through the original catalogs; e.g., referring to the 150 watt VW, the 1949 catalog says (from memory – I can dig up the exact wording) that the VW is “the most powerful transformer with UL listing.” As far as I know, no catalog indicates that the ZW was UL listed. (Nor the KW.) Early RWs (intro 1948) were not UL-listed – they had a circle-L symbol in the upper left corner of the face panel; later production (1949-on) had the UL symbol up there. I’ve seen at least one RW at a train show that had a cardboard UL sticker pasted over the circle-L.
Before the very late '40s, it seems – though I’m not completely certain about this – that none of Lionel’s transformers were UL-listed. Nevertheless, until 1939 and the introduction of the Z, Lionel and other manufacturers conformed to the 150 watt maximum. American Flyer brought out their 250 watt 12B in 1940, no doubt to remain competitive with Lionel. Jefferson (another prominent independent maker of toy train transformers and a/the supplier to American Flyer, made over the years ('20s though '40s) a succession of 150 watt models, but (as far as I know) nothing more powerful. I infer from all this that the UL (and/or some other industry standard?) limited approval to 150 watts.
Finally, many people these days don’t realize that before the passage of legislation in the early '70s (which created the Consumer Product Safety Commission), there
A safe product produced by Lionel:
The 107 direct-current reducer connects one rail directly to one side of the 110-volt power line. Half the time, it will be the grounded side. Whether this is unsafe depends on whether you see your glass as half empty or half full. That white stuff on the top is asbestos, to keep little fingers from getting burned. Also available as the model 170 for those with 220-volt service. Not listed by either “United Laboratories” nor Underwriters Laboratories.
Jjm, a TVS does pretty much nothing until the voltage tries to exceed its rating. Then it clamps the voltage to that value. So there should be no worry about putting one across any kind of power supply as long as the TVS’s voltage rating is higher than any instantaneous voltage from the supply. The CW80, for example, seems to use a 20-volt transformer; so the peak voltage is about 28 volts. A 36-volt TVS should work fine with that. And it could be said that a 33-volt device would be okay.
Good post Martinden.
Much info I had not heard previously although for several years we had a knowledgeable and helpful Underwriters Lab employee who was a member of the OGR Forum. In fact I sold him a new in the box MTH Z-4000 which within months had a blower motor and starboard throttle failure [which thankfully MTH fixed]. He was a fan of the pw ZW but I reminded him that its limited output of about 180-90 watts, split between throttles or assigned to a single throttle, was not sufficient for the layout he planned.
These transformer discussions [in particular on the single core ZW] have occurred repeatedly on OGR since 2001 and opinions are far more abundant than fact. Thanks for your informative report.
KW…ZW…CW… BAH HUMBUG!
I prefer these little beauties! [:D]
Bobby
Thanks for that Info Bob. I’m gonna order some of those. Gotta love Mouser!
Bobby
martinden,
Since you quoted me, let’s be clear that I never said that the postwar ZW, KW or anything else ever had UL approval. What I did say was that the old 1940’s designs would not be able to get UL approval as toy train transformers in this day and age.* So if someone feels the need to run a transformer with UL approval this holiday weekend, the postwar ZW won’t make the cut. I remain pretty comfortable with that assertion.
I will run mine, however; cautiously, as previously stated.
*In the same sense, one couldn’t get “governmental approval” to reproduce and mass-market the 1951 Oldsmobile 88 with the Rocket Engine, as it lacked emissions-control equipment, among other things. However, if I still had one, I’d drive it.