2 Basic motor Q's

The Pittman, or any other can motor used in model trains, are driven by DC, they all have permanent magnets and a standard commutator.

I don't know of any effect that the chopped wave has on the motor, by the time it gets to the motor it has been filtered and converted to DC.  Also, most model train DC motors are driven by something akin to pulse-width-modulation or using a triac as in the standard Lionel DCDR.

Q1 - Neither. A Pittman is a permanent magnet DC motor that runs on DC only. You can run it on a DC power supply of your choice - there are so many different possibilities in this range - including toy/hobby supplies & "power packs".

Q2 - It depends on the power supply, modulating design, and filtering.

When I hear Pittman, I think of DC motors. Still, weren't the universal motors used by American Model Toys manufactured by Pittman? And Pittman made "O" gauge trolley kits with universal motors.

Virtually all the Pittman or other can motors you see are DC motors.

Thank you all!  I now realize that the motors I mentioned have a variable B-field.  So, with a constant B-field,  they are necessarily DC motors,  right?  Thus,  the AC power supply MUST be rectified before reaching the motor.  I believe/presume that this is done in the manner I said above:  Full-wave rectification + filtering [to reduce the 'ripple'].

to PLCPROF:  Thx for the additional detail,  which I shall study carefully!

Let's not forget that DC can motors react nicely to applied pulse width modulation  (PWM) signals.

phil gresho posted:

Q1.  Is an engine motor  [typically Pittman] a UNIVERSAL motor driven by 60Hz AC,  or is it a SERIES-WOUND DC motor supplied by full-wave rectified and filtered [via capacitors]  60 Hz AC?

There are different model motor types and Pittman isn't "typical" in all cases. Traditional O-gauge had plenty of universal motors which run on either AC or DC. You haven't explained your main point of reference.

Q2.  What effect does a chopped sine wave have on their behavior & performance?

I've used a home-made variable-pulse-width voltage-regulated throttle for DC motors (mostly HO and N) which gives better low-speed control in some cases, particularly for lower-quality mechanisms.

ACE:  Mine was a 'generic' Q...  Before I was informed that [most of] these modern motors use a permanent magnet.

Lionel used universal series motors from Lionel’s inception in 1900 to just a couple of years ago. Since 1970 or so the universal motor made by Lionel has been called “Pullmor”. This motor has a wound rotor and stator and the rotor and stator are wired in series. The hot enters one brush and exits the other brush into the field which is grounded; hence, in series.

The DC traction motors used in real diesel electric locomotives are universal series motors that are very similar in construction to Lionel’s Pullmor motor. In some instances the rotor and stator are wired in series while in others the rotor and stator are excited on separate circuits. Most locomotives before ~1980 used universal motors. Most other locomotives such as the GG1 and such used universal motors. Prototype locomotives never used can motors. The reason that prototype locomotives did not use can motors is that universal motors are more efficient at cheaper cost. Today the majority of heavy freight haul locomotives use asynchronous motors, commonly known as induction motors.

Very briefly, induction motors function by a rotating magnetic field of the stator. The frequency of the rotating magnetic field is dependent upon the frequency of AC. The rotor of the induction motor is made of copper plates. The copper plates are arranged in what looks like a hamster wheel and is often called a “squirrel cage”. The rotating magnetic field induces (hence the name induction motor) current flow in the copper plates which results in the turning of the rotor. By definition, the rotor always turns slower than the rotating magnetic field (called slip) hence it is not synchronous with the rotating magnetic field. If the rotor becomes synchronous with the rotating magnetic field current flow in the copper plates is no longer induced and torque drops to 0.  Advantage of induction motors is that they are very high efficiency (>90%) and very high starting torque.  As far as I know, there are no induction motors used in model railroading.

DC can motors have been nearly eliminated in the RC world by what is called a synchronous motor. The reason for this is that DC can motors are very inefficient compared to synchronous motors. Märklin uses synchronous motors in some of their model trains (called the soft drive or C-sine motor). Märklin is the only one that I know of that uses a synchronous motor in model railroading. Lionel attempted to make a synchronous motor for their trains but failed. Synchronous motors are used in prototype railroading where high starting torque is not needed. Bullet trains like those in Japan or the TGV in France use synchronous motors.  Like induction motors, there is a rotating magnetic field from the stator. The difference is, the rotor rotates synchronous with the rotating magnetic field. Technically, at 0 rpm the rotor produces 0 torque. For a long time, synchronous motors could not self-start, but modern electronics allow for very low frequencies to be used to such a point that they self-start. Unlike induction motors, synchronous motors have either DC powered magnets or permanent magnets and these magnets constitute the rotor. With a synchronous motor, the rotor can be either on the outside or on the inside of the motor. These are called inrunner or outrunner motors. AC is used on the stator which produces the rotating magnetic field which is dependent upon the frequency of the AC signal applied. Advantage of synchronous motors is that they are very efficient (>90%) and their linear torque curve allow for precise control. The so called DC brushless motors are a form of synchronous motor.

DC can motors have already been discussed. Practically all current production of our O gauge trains use DC can motors and the vast majority of the other scales also use DC can motors. Some manufactures still use open-frame DC motors. I will add that just because the motor is in a can does not mean a continuous magnetic field from either the rotor or stator. If you were to take one of the DC motors apart from one of our trains, you would find large gaps between the magnets used for the stator. You can find DC motors manufactured from ring magnets, but those motors are 10 times the cost.  

WBC posted:

Lionel used universal series motors from Lionel’s inception in 1900 to just a couple of years ago.

I'll bet that's news to Lionel, try 20 or more years since there were more than a handful of universal motors used in Lionel products!

Lionel had products with universal motors as recently as the 2014 catalog.  Thus, it appears that Lionel used universal motors in various products from 1900 - 2014.

I would agree that any past production is news to Lionel considering records have not transferred well from one owner to another. 

gunrunnerjohn posted:

WBC posted:

Lionel used universal series motors from Lionel’s inception in 1900 to just a couple of years ago.

I'll bet that's news to Lionel, try 20 or more years since there were more than a handful of universal motors used in Lionel products!

John, His statement was correct.  Lionel and even MTH still use conventional motors to appeal to traditionalist.  Especially in the 90s and early 2000.  Those motors are apparently becoming harder to make though.  G

Yes, they use them in a handful of products, but they're hardly mainstream nowadays.  He was making it sound like they were the principal power in the modern models.

I'll bet that's news to Lionel, try 20 or more years since there were more than a handful of universal motors used in Lionel products!

For some of us twenty years is just a couple of years ago. 

C W Burfle posted:

For some of us twenty years is just a couple of years ago.

There is that, of course.