Fixed voltage transformer

My layout is powered like that.

Years ago I put two 18V transformers (IIRC they were each around 270 watts or so)  into an old battery charger case, put ammeters on and banana sockets for connections. They are phased and connected to a front panel on/off switch,  but outputs are connected only on the common side. The transformers were on sale, as I recall, and the company was offering free shipping. Free shipping for heavy transformers - yikes! They probably figured out the economics of that one eventually.

There is also a three prong 110V outlet on the back for the command base.

These run a pair of TPCs.

Here's some candidates

https://www.ebay.com/itm/power...3:g:y1EAAOSweiFcKYDy

https://www.ebay.com/itm/power...a:g:CnsAAOSwVCpcC5lF

I'm not familiar with that particular topic. I run my layout using something similar though. I have six power supplies made from three, 6.3 V, 20 A connected in series. Yes, you heard me correctly, that's a total of 120 Amps @ 18.9 Volts. Let's just say I have a large layout. 

Just remember, if you decide to power your trains with this type of supply, you won't be able to run conventional unless you have a way to vary the voltage.

Before Lionel produced their PowerHouse transformers, I bought Hammond transformers to provide 18 VAC to my TPCs.  Part numbers  165S18 (10A output), 165U18 (15A), and 165V18 (20A) are appropriate.  Digikey has these in stock for $65 to $85 plus shipping.  Considering the effort and expense of adding circuit breakers, enclosures, plugs and connectors to the bare transformer, buying a PowerHouse is better alternative these days.

Big Boy's transformers in series is an interesting way to achieve 18 VAC.  Will have to experiment with a couple of 9 VAC transformers I have laying about.

I bought two Hammond transformers several years ago. Been very satisfied with them

Just be sure to use a fast acting circuit breaker with them.