Is there an inexpensive way to keep the voltage of a Z-4000 at 18VAC. I worry when guests run the trains and don't know not to power up to 20VAC. Would like to protect my circuit boards from overvoltage.
Original Post
Replies sorted oldest to newest
Short answer, no method that I know of. Lionel made the unfortunate decision to design their electronics to an 18V maximum, when there was already an established precedent by the mid-1990s for 20V, 22V, or even 24 volts.
If you have a few hundred $$ to burn, you could swap the Z-4000 for a ZW. Plug it into a beefy 15A "Variac" autotransformer, then reduce voltage going into the primary by about 10%. Of course you should probably add a fast-acting circuit breaker and transient voltage suppressor(s).
That being said, 99% of conventional O gauge locos won't take a curve at 18 volts. I'm not sure what you're running. If it's conventional, it will probably derail if they give it more than 18V. If you're running command locos, just put a note by the transformer not to exceed 18 volts. My $.02.
This subject comes up every few years. While there are elegant solid state solutions to reduce maximum voltage, the simplest is to start by using a one-ohm, 5-watt resistor at the output of the transformer going to the center rail. If the train is drawing, say, 2 amps, there will be an approximate 2 volt drop in voltage across the resistor. You can experiment putting 1 ohm resistors in parallel for less voltage drop or in series for a greater voltage drop.
Keep also in mind, that the actual voltage on the track may be less than what the Z-4000 shows on the meter because of all the small voltage drops that may occur in the wiring and connections to the rails. An inexpensive RMS voltmeter is useful for measuring actual voltage on the track.
When your guests leave, remove the resistor(s) !
