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@OGRNorman posted:

Why is AC Voltage applied to the 3 Rail Track while the Locomotive motors are DC Voltage Motors ?

DC can motors provide smoother and quieter operation, the possibility of cruise control, and much lower current consumption.  Combined with the fact that I'm sure they're cheaper as well, it was an easy choice for the whole industry.

The voltage is obviously converted to DC before it gets to the motors.

Simple history lesson. Lionel trains used AC motors until the 1990's. And perhaps a bit later for some of them. For example, the Platinum Ghost model from about 2000 showcased open frame motors with a clear shell so you could see them in operation. If they had abruptly switched from AC current to DC, all existing trains would have been incompatible with the newer ones. By converting AC to DC in the engines, they all coexist. That way you can run a Lionel from the 1950's with a current engine. Try it sometimes. The old ones have their own magic.


Another history lesson: selenium rectifiers (needed to change AC to DC) were not perfected or in general commercial use until the 1930's. Lionel trains predate that era by 30 years. AC series-wound motors don't need track polarity switching or other fancy electronics; they just use the E unit to reverse the AC polarity inside the motor and Voila!

And -- AC is easily transformed (voltage raised or lowered) with simple transformers.

@OGRNorman posted:


Why is AC Voltage applied to the 3 Rail Track while the Locomotive motors are DC Voltage Motors ?

Were the LIONEL Locomotive motors once AC Voltage Motors ?


Gunrunner answered your first question very well.  The first Lionel, in fact all the early three rail and two rail motors were not only AC they were AC / DC universal motors.  Even these motors run smoother and quieter on DC. Much of the reasons these motors were so common until the sixties is the lack of a suitable low cost material for permanent magnets. Early permanent magnet motors lost their charge just sitting let alone if you used them. The first Alnico alloy was created in Japan around 1930 and took about thirty years to trickle down to consumer products. I suspect WWll played some role in the delay. Even in aircraft where weight is a critical factor the universal AC / DC motor was still used in such applications as trim-tab motors.  Gordon Varney one of the fathers of HO in the United States stated that the lack of suitable motors was one of the big hurtles in the early growth of HO scale. The development of the Alnico magnet was key in the development of a dependable HO sized motor. The fact that O scale was large enough to accommodate  motors with stator windings delayed the adoption of permanent magnet DC motors in O scale / gauge  both for two and three rail.                       j

Last edited by JohnActon
@BOB WALKER posted:

For the record, all electronic based systems function on DC.

Well... not really.  While it's true that there is DC used on these boards as well, there are still AC command boards and conventional boards around, the ERR AC Commander for instance.   It uses triacs to directly switch the AC for the AC motor.  Lionel also has the ACDR board that serves a similar function.

@wild mary posted:

Additionally no special wiring is necessary with AC for reverse loops.

It's the three rails, not the AC, that eliminate the need for special wiring for reverse loops (as well as for wyes and turntables and any other track arrangement that turns trains around).

DC on three-rail does not require special wiring: Frank Ellison's Delta Lines was powered with DC and used outside third rail.  Frank advocated three-rail over two-rail because of the complications in wiring two-rail.

The prototype (full-size trains) also use third rail or catenary which is electrically equivalent to a third rail.  Prototype electrification uses both AC and DC.

Last edited by PGentieu

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