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Generally speaking, using AC in models results in a little more heat because it gets converted to DC, to be used in turn by a DC motor, at least in most modern locomotives.  This conversion process generates a little extra heat because it's not 100% efficient.

For incandescent lamps there is no difference.

For LED's AC again generates a little more heat because the LED, via its diode function, blocks 1/2 of the AC waveform.  This too is not 100% efficient.


Last edited by Mellow Hudson Mike

@Mellow Hudson Mike, the opposite is true of open frame motors. They run measurably hotter on DC whereas in your case with DC can motors, the rectifier emits a negligible mount of heat barely perceptible to performance.

3 Rail O Gauge has been low voltage AC for over a century. There is essentially ****nothing in the 3 rail O Gauge arena that won't operate on AC. Stick with the establishment.

****There are always a few exceptions to the rule - there were some low cost sets that are DC only, but these are very very limited and of no real value to be concerned with.

Last edited by bmoran4
@bmoran4 posted:

@Mellow Hudson Mike, the opposite is true of open frame motors. They run measurably hotter on DC whereas in your case with DC can motors, the rectifier emits a negligible mount of heat barely perceptible to performance.

Okay, now I'm confused (again. )

The "Tracks Ahead" series did a video of the "Robinson Layout", featuring American Flyer S gauge. In that video, the narrater mentions that, by installing rectifiers in his engines, they will run "smoother and cooler" on DC.

Is that because the power source (transformers) are still supplying AC? Really, aren't most, if not all, "modern" engines, equipped with DC can motors, doing the same thing?

Mark in Oregon

The Gilbert universal motors were originally designed to be operated with  AC power but they run great on DC as well. They usually will run slightly quieter on DC but unlikely cooler. The motor performance also depends on what DC is supplied to the motor, ie, half wave, full wave, or filtered constant DC (similar to a battery output.) When Gilbert introduced the open frame DC motors the wound field was replaced with a permanent magnet plus another very important change was made. The armature for the DC motor was redesigned with more turns of a finer wire resulting in double the DC resistance of the AC armature.

Many Gilbert operators prefer DC power since modern full wave bridge rectifiers are so inexpensive. It does not matter where the rectifier is located (in the engine or in the power supply) for operating Gilbert engines.

DC Can motors are completely different, they are not universal motors.

I highly recommend looking at Clinic #42 on the website. It provides more explanation of this subject than you likely want to know. It also provides a thorough discussion of some issues with Gilbert accessories when using DC track power.

There is one more subtle point about operating universal motors on AC vs DC power. The comparisons discussed are for pure sine wave AC such as from a postwar transformer. If a modern power supply is used such as a ZW-L where at less than full voltage the waveform is chopped and full of harmonics these comparisons do not apply. A universal motor will be hotter when a chopped waveform is used than with a pure sine wave even though the engine runs better at low speed with the chopped waveform.

@Strummer, I don't have access to the video to comment specifically, but it doesn't really matter as one can't alter the rules of physics. Universal series wound motors run hotter on DC because of, unlike AC, the non-existent phase angle difference between voltage and current. The AC wave also provides a cooling break that is not provided by DC. You can geek out on the math behind all of this.

To take this a little further: if I run one of my Flyer 300 steamers (no smoke or "choo choo" sound), it runs great (smooth and quiet) on AC. If I use a DC pack, it does sound quieter, but it seems like the difference is that the reverse unit doesn't seem to be "buzzing" slightly, like it does on AC. This applies to my other 300, as well as my this possible, or is it just me?  🙂 I would think the reverse unit would react to either current, whether AC or DC... 🤔

Mark in Oregon

You are correct that the reverse unit solenoid can run quieter on DC. That is because the current is not alternating. When operating on AC, the current is alternating, therefor imparting an alternating magnetic field on the solenoid causing it to audibly vibrate the plunger and therefore buzz. It has been suggested that the alternating magnetic field (as opposed to the static one on DC operation) will also prevent the solenoid plunger from getting "permanently" magnetized and therefore becoming sticky. Also, DC operation of the solenoid will run much hotter and could contribute to premature failure. Recently on the forum here, there was a member who operated an uncoupling solenoid designed for AC on DC and it melted the housing!

In a Gilbert engine using the locking lever just prevents the pawl attached to the solenoid from moving. As Mark says, the current is still flowing through the solenoid of the reverse unit. I find the 120HZ buzzing of the solenoid on AC track power to be louder when it is locked. Using DC track power will quiet the reverse unit solenoid but it will be hotter than on AC power and it will magnetize faster.

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