Athearn Trainpak Power Pack SDK-789 (ATH9997) pulse power?

[MK]

BTW, if I had a scope I would check it like C855B said.  But I don't. 

[peteski]

Peteski, I'm going to run a simple holiday train around the tree.  I'm going to use a  DC Kato loco.  Maybe run it 2-3 hours straight at prototypical speed.  I've heard that if you use a power pack that has a specific pulse circuitry (e.g., Railpower 1370 but not the 1300) it will destroy the motor by causing it to heat up.  I think this is not PWM as I know that won't be a problem.

Let me rephrase my question then.  I have a DC loco, will it burn up with the above power pack?  I hope this is simple enough.    I note that this same power pack comes bundled with Athearn's all-in-one turnkey train sets.  I figured if it burns up locos they would get a lot of phone calls.  Unless Little Johnny runs it at warp speed. 

Kato has a standard permanent-magnet DC motor with iron core armature (not coreless). No DC power pack (pulse or otherwise) will damage it. Not sure where you heard otherwise.  What can damage DC motors (both the standard ones and coreless) is leaving them sitting on a track powered by DCC.  DCC power consists of full track voltage flipping polarity many times a second. That causes the motor armature to vibrate, heat up and possibly get damaged.  But DC throttles are safe for DC locos.

[MK]

Kato has a standard permanent-magnet DC motor with iron core armature (not coreless). No DC power pack (pulse or otherwise) will damage it. Not sure where you heard otherwise.

Thank you Peteski!!!!    Don't want to ruin the newly acquired Operation North Pole (complete) set.

What can damage DC motors (both the standard ones and coreless) is leaving them sitting on a track powered by DCC.  DCC power consists of full track voltage flipping polarity many times a second. That causes the motor armature to vibrate, heat up and possibly get damaged.  But DC throttles are safe for DC locos.

That part I know as I'm mainly a DCC guy.

[ncbqguy]

This is not current (pun intended!) information as it's been more than a decade since I've been away from repairs and daily consumer customer contact, but back then the only truly damaging wave form was from the "Troller" and related Blue Wave power packs.
I know that many people loved them, but they were suspect in destroying Kato-made Atlas HO motors.   The particular series had the windings ultrasonicly soldered to the commutator plate and it was thought that the Bluewave was unsoldering them.
A caution- not all the Kato (or Bachman) locos have conventional 12v motors so stick to the cheapie train set locos if you're not confident about the power pack...but the Athearn one looks to be a Bachman /Kader built or copy and probably is okay because if there was a major problem with them it would likely be on record.
Charlie Vlk
PS- Pets were a high percentage of the cause of repair cases at both Con-Cor and Kato...from hair in gears and bearings or being chewed on or knocked off the layout. 

[MK]

I decided to give Athearn tech support a call and they said that their Trainpak does not have pulse.  He was well aware of what that is and what it can do to some of the older locos.

I tried calling them yesterday and could not get a hold of anyone (out of office, mailbox full, no operator, etc.) and thus my starting this thread yesterday.  But still I will initially monitor for humming and heat. 

[peteski]

I decided to give Athearn tech support a call and they said that their Trainpak does not have pulse.  He was well aware of what that is and what it can do to some of the older locos.

I tried calling them yesterday and could not get a hold of anyone (out of office, mailbox full, no operator, etc.) and thus my starting this thread yesterday.  But still I will initially monitor for humming and heat. 

I still doubt that it has "un-pulsed" DC output, but I could be wrong.  As I explained earlier, there are "pulses" and then there are "pulses".  Not all are the same, and some can be more detrimental to the motors. 

Here are some examples of what I would expect to  see from a standard DC throttle (without pulse or with pulse feature turned off):



Ignore the top waveform (that is the AC voltage coming from the transformer inside the throttle).
The middle waveform is what most standard throttle will have on their output. It is pulsing (unfiltered) DC voltage.  That should not damage the motor.  That is what Kato throttle output looks like.
The bottom waveform is what you would see in a throttle which also includes a filter cab but has unregulated voltage. The voltage is not close to pure DC (which would be a straight line on the graph), but still has a small pulse component. 

Now for a typical low-end throttle which has pulse feature:



Again, ignore the top waveform. Now you see the difference. This is still DC since the polarity is not changing, but the voltage stays low 50% of the time. That is usually how the "pulsed" throttles are set up.

Charlie mentioned a problem due to heating and  motor construction., I don't believe that any of this will apply to the contemporary N scale motors.  The armature wires are either soldered or crimped to the commutator. They should not come loose.  Yes, a motor will get warm during prolonged running (especially of the loco is pulling a heavy load), but that would happen even if the loco was powered with true filtered DC voltage. The motor is doing work so it gets warm.  While the pulsed supply voltage might cause it to run slightly hotter, it should not get hot enough to cause damage.

Monitoring the model is a good ideal And don't expect it to stay cool - it will get warm - just shouldn't get hot enough to cause damage.

[MK]

Thanks for the info Peteski.  Being an engineer, though not electrical but did have some training in EE, I totally get what you are saying.  Those graphs bring back memories when I was dabbling in EE.  Thanks for the effort of finding them and posting them.  Serves a great reference for everyone.

[Doug G.]

Put the loco on an oval of track. Hook up the Athearn and run the loco for a while.. Check to see how warm/hot the loco gets. Hot? Don't use the Athearn. Normal warmth? Use the Athearn.

No big deal. Way too much is made of pulse power. Even if a pack has pulse power, it is gradually reduced with increased loco speed.

Doug