The O / O27 Power Supply



Lionel electric trains and accessories operate on low voltage ranging from 8 volts to 18 volts, depending on the type and size of the locomotive and train and on the rated voltage of the lamps used in illuminated accessories. This low voltage is generally stepped down from the regular house power lines by means of a Lionel transformer.

While the house power supply used in this country is usually 110 to 120 volts, 60-cycle alternating current (AC), there are a number of exceptions. Some parts of California use 50-cycle current some areas in Canada employ 25-cycle current while some downtown areas in New York City still use ll0-volt direct current (DC) with which a transformer cannot be used without a special DC-to-AC inverter.

Regular O / O27 AC transformers are designed to work on 110 to 125-volt, 60-cycle, alternating current. Other combinations of voltage and frequency (cycles) require special transformers which are available through special order. The voltage and frequency ratings of a transformer are generally listed on the transformer panel. They correspond to the rating of power line or the transformer may be severely damaged. In case of doubt you can ask your company about the type of power you have before buying or installing any equipment which is to be plugged into your wall outlet.


In addition to their voltage and frequency rating, all transformers also bear a wattage rating. The wattage of a transformer corresponds to its capacity, or ability to furnish power. While the voltage and frequency of the transformer you must use are determined by the available power line, the selection of its wattage is guided by the size of your outfit and the number of lights and operating accessories. In planning to expand your railroad always estimate the power you will need to find out if your transformer will be adequate. It is always wisest to get a transformer larger than the one you require for your immediate needs to provide power for future expansion.

As a transformer becomes warm when in use its output normally diminishes. Because of this fact not more than three-quarters of its rated wattage should he drawn from a transformer continuously.


The following table lists the power in watts used by various model railroad components:

"027" locomotive - 25 to 35*

"O" locomotive - 30 to 40*

Smoke generator - 5

Operating accessories - 10 to 40

Automatic track signals - 10 to 15

Each 6-volt lamp - 1.5

Each 14-volt lamp (small) - 2

Each 14-volt lamp (large) - 3

Each 18-volt lamp - 5

* These wattages are drawn by locomotives when pulling the regular number of cars and include the power used by the whistle. However, you must add the wattage used by lamps in illuminated cars.

Power requirements of automatic couplers and operating need not be added in the total since couplers draw current only for an instant and operating cars only when the train is not running. For the same reason do not add the power used by such accessories as the Lumber and Coal Loaders, Automatic Life Bridges and others. All such accessories can be generally used even with the smallest transformers, provided that they are operated when the train is standing still.

Accessory lights and equipment containing steadily burning lamps, such as switches and switch controllers, considerable amount of power and should be added in the total power requirements.


A few words about voltage may help you understand the operation of your transformer so that you can use it to the best advantage. The "fixed" voltages marked on your transformer panel or the voltages indicated by your transformer voltage control at any particular setting are almost never the actual voltages delivered to your track or your accessories. The reasons for this variation are several. The voltages marked on your trans formers are "nominal". That is, they are accurate under certain specified conditions: when the line voltage fed into your transformer is just 115 volts and when no current is drawn from the transformer. Actually, the line voltages may vary from 125 to 110 volts, or even lower, depending on the standards in your locality and on how much electricity is being used at a particular time. This variation, naturally, results in a comparable variation in the output voltage of the transformer. If your train seems to run slower during a sudden storm it's probably because hundreds of people in your neighborhood had switched on their lights and so depressed the line voltage.

In the same way that a heavy demand for power may lower the voltage in your neighborhood, a heavy load on your transformer lowers its output voltage as well. For example, the fixed binding posts which are marked 14 volts may, under actual operating conditions deliver only 12 volts, or even less. In the case of a short circuit so much current is drawn from the transformer that its voltage drops to 2 or 3 volts--too low to operate the train or even light the lamps.

In addition to the voltage loss in the transformer itself, commonly called the "regulation"of the transformer, still further voltage losses occur in connecting wires For this reason, wiring of a large layout should be carefully planned. If a platform is to be used, the wiring is best located on the under surface of the platform. All wires should be as short as possible. To keep your wiring to a minimum, accessories which require the same voltage should be ganged up in "parallel". This "feeder" system. system can be used for wiring operating accessories as well. Can be used for wiring operating accessories, as well


In operating large layouts it is frequently found that the train slows down when running on the portion of track farthest from the Lockon. This is due to voltage losses in the track itself and can be remedied by attaching additional Lockons at the points on the track where the train slows down. See Figure 61. Be careful to connect the No. 1 and No. 2 clips of the auxiliary Lockons to similarly numbered clips of the Lockon connected to the transformer or else a short circuit will result. Ordinary lamp cord is well suited to these connections as well as for "feeders" described above.

The main part of voltage losses in the track is due to loose track pins. These loose connections can be frequently detected by the heating effect of poor electrical contacts. After the layout has been in operation for a half hour or so, run your finger down the rails. Loose rail joints will then become apparent as hot spots on the track.

Click here to return to Basic O/O27 Manual Index

Click here to return to Main Page