I have 2 ZW transformers that I would like to upgrade so I can run newer trains with them. Can I get a parts list and a link to the wiring diagram for this?
Thank you Jess
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Jess;
I use 3 PW ZW’s on my layout. I added some high speed circuit breakers to protect the electronics in my modern engines. I used this video from the Backshop series and the box has saved my bacon numerous times.
@Jess56 posted:I have 2 ZW transformers that I would like to upgrade so I can run newer trains with them. Can I get a parts list and a link to the wiring diagram for this?
Whenever the topic is discussed, the consensus tends to be to recommend adding both circuit breakers (the faster the better, though more expensive the faster you go) and TVS diodes. The circuit breakers can be placed anywhere in series between the transformer and the load on each circuit (though they're usually clustered near the transformer), but there's a split of opinion on the TVS diodes. Many feel they should be placed across each output at the transformer (since many spikes originate from the transformer), while many others insist the best protection is only afforded by placing them directly across the terminals of each piece of equipment to be protected (or directly on the PCB). I tend toward the latter school, but opting for the easy placement at the transformer will at least provide more protection than omitting the TVS diodes entirely. YMMV . . .
@gunrunnerjohn posted:As for the TVS placement, I refer you to the diagram by @Adrian!, he explained it graphically better than I can.
I don't understand that picture at all and I know how all the protection stuff works. Pinch and bounce are new terms to me.
@CALNNC posted:I don't understand that picture at all and I know how all the protection stuff works. Pinch and bounce are new terms to me.
Well, you may not understand exactly how a TVS is used effectively. 
The wavelengths involved with ESD pulses can be an inch or less, which means within that inch of wire, the voltage in reference to signal ground can vary from very low to several hundred volts. The pulse widths are no more than a couple of nanoseconds, sometimes less.
Although a TVS diode can be placed anywhere in the circuit and potentially provide some benefit, typically they're placed as close as possible to the circuit that you're protecting. I used a ton of TVS diodes when I was designing avionics, they were on the I/O lines of the instrument or control box next to the actual interface components. That's where they are the most effective.
The "pinch" and "bounce" in the picture are attempting to describe the behavior of the ESD event and the effects of the TVS diode. The "pinch" obviously is the diode, and the "bounce" is the voltage of the transient at that particular spot in the conductor.
@CALNNC posted:I don't understand that picture at all and I know how all the protection stuff works. Pinch and bounce are new terms to me.
Yeah, it was a bit dense for me as well, when I first encountered similar discussions. The key for me was when I realized the transient nature of the voltage spike created effects in the radio frequency range. That kicked me into my ham radio background, and the effect of standing waves (illustrated as the loops in the rope). IOW, unlike (much) lower frequency AC, which distributes the alternating polarity fairly evenly around the circuit, such high frequency RF pulses can create "null points" at various points around the circuit, where no voltage can be detected even when the full fluctuating voltage can do damage even a few inches away. If a TVS happens to be installed at or near such a null point, it will provide absolutely no protection (or limited protection) to any other place in the circuit. By placing the TVS *at* the vulnerable point, any spike that creates voltage that could damage the component *will* be grounded, protecting the component. A TVS placed anywhere else will be purely a crap shoot as to whether it will help at all, or how much.
@Steve Tyler posted:... the consensus tends to be to recommend adding both circuit breakers...and TVS diodes.
Breakers optional, TVS diodes mandatory.
Thanks for the info..what size of TVS Diodes do I need?
@Steve Tyler posted:... If a TVS happens to be installed at or near such a null point, it will provide absolutely no protection (or limited protection) to any other place in the circuit. By placing the TVS *at* the vulnerable point, any spike that creates voltage that could damage the component *will* be grounded, protecting the component. A TVS placed anywhere else will be purely a crap shoot as to whether it will help at all, or how much.
That may be well and good for RF, but the wavelength at 60Hz is about 16 million feet, so the chances of finding that null spot is fairly minimal. We used Tranzorbs, TVS diodes, MOV's, and gas discharge tubes in circuits to terminate field cables from a few hundred feet to several miles long with DC and AC signals on them, and you put them where the cable terminated. One of the interesting things was to watch those 600 volt gas tubes fire due to lightning hitting as far away as 7 miles from the cables. From this question, it implies the best place to put a TVS is at the rollers of each loco to protect it, and the output terminals of the transformer to protect that.
@CALNNC posted:From this question, it implies the best place to put a TVS is at the rollers of each loco to protect it,..
Or on board, closest to the point that the circuit gets its track power from the chassis track connections.
@CALNNC posted:That may be well and good for RF, but the wavelength at 60Hz is about 16 million feet, so the chances of finding that null spot is fairly minimal. We used Tranzorbs, TVS diodes, MOV's, and gas discharge tubes in circuits to terminate field cables from a few hundred feet to several miles long with DC and AC signals on them, and you put them where the cable terminated. One of the interesting things was to watch those 600 volt gas tubes fire due to lightning hitting as far away as 7 miles from the cables. From this question, it implies the best place to put a TVS is at the rollers of each loco to protect it, and the output terminals of the transformer to protect that.
You're missing the basic point. We're not dealing with the 60hz power, we're trying to deal with the ESD spikes. Those are in the nanosecond range and generate the RF waveform being discussed. FWIW, a Transorb and a TVS diode are the same thing. An MOV or gas discharge tube is used to protect against voltage surges, which are quite different than a TVS that is there to protect against very short duration ESD spikes.
@CALNNC posted:That may be well and good for RF, but the wavelength at 60Hz is about 16 million feet, so the chances of finding that null spot is fairly minimal. We used Tranzorbs, TVS diodes, MOV's, and gas discharge tubes in circuits to terminate field cables from a few hundred feet to several miles long with DC and AC signals on them, and you put them where the cable terminated. One of the interesting things was to watch those 600 volt gas tubes fire due to lightning hitting as far away as 7 miles from the cables. From this question, it implies the best place to put a TVS is at the rollers of each loco to protect it, and the output terminals of the transformer to protect that.
Well, dunno the details of your setup, but "where the cable terminated" sounds an awful lot like "at the PC board/device being protected". And FWIW, yes, putting TVS diodes both at the transformer *and* at the device being protected would IMHO provide some additional increment of protection (though most transformers are IME usually durable enough to survive a spike on their own), at the cost of requiring more diodes and installation time.
