Motor Current limits

[Nathan Jahreis]

Hello everyone,  I don't know if this is the right place to post this but...  I know that motors have their limits, but I am not sure of how much current you can pump through the motors we use in HO scale.  Would the more current mean better control?  (keep it in perspective, i'm not trying to run lightning bolts through a GP40   )  Reason I am asking,  My power packs are around 2 amps,  but I have an auto-transformer that regulates AC 0-130v at 20amps!  If I put a bridge rectifier on it, it probably would burn out every DC thing in sight    (It can fry .22 gauge wire in about 2 seconds) 

Nathan

[richg]

Leave the autotransformer alone. I have been in electricity and electronics for many years. If you have to ask this question, you probably do not have much electrical knowledge.
Autotransformer's do not have primary to secondary isolation like a regular transformer does. To my knowledge, autotransformer's are still like that.

More current does not mean better control.
HO model railroad motors can have current requirements of maybe 200 ma and as much as 2 amps at 12 volts DC.
Get a multimeter and learn how to use it or ask here for possible answers with a particular device.

Rich

[Nathan Jahreis]

Richg,  I didn't think the autotransformer would need primary and secondary winding's, all its doing is adjusting the given wall 120v from 0-120+/-.  I thought unlike hobby transformers it uses the windings themselfs as the regulator, not dropping the voltage down to a max of around 18v, then from there letting a potentiometer and transistors do all the work.  I do have some electrical education (highest grade in my class of seniors, I was a freshmen) but we never worked with high voltage devices such as this, that is why I asked.  I had that class last year, but surprisingly model railroading got me into it , now I want to build a Marx generator   Thanks for the info, Nathan.

[richg]

Please take time to carefully read the below link about transformers. Notice the difference. The auto transformers have no isolation. That can be dangerous under certain conditions.
It is possible to put the wall plug for the auto transformer into the outlet the wrong way and the common terminal becomes the hot terminal. Some pople like to snip of the third prong, the ground prong.
I have used them for quite a few years in hobby applications and industrial applications.
I did a Google search for Marx Generator and does not seem to be for model railroad applications.

The model railroad transformers do not regulate voltage.

Now I am beginning to think you are putting me on.

Rich

[Nathan Jahreis]

No, I am not trying to put you on, sorry if I gave you that impression.  Also, a marx generator most definitely has nothing to do with model railroading just crazy electrical projects.  I didn't understand your explination of the following quote "It is possible to put the wall plug for the auto transformer into the outlet the wrong way and the common terminal becomes the hot terminal. Some pople like to snip of the third prong, the ground prong."  my auto transformer has 5 screw type terminals.

Thanks for your help, sorry if you got a bad impression, Nathan.

[Jhanecker2]

As a QC inspector : mechanical & electric  for thirty years I would advise you not to get that transformer anywhere near Model Railroad equipment . I would also suggest that you acquire any of the numerous books on DC & DCC wiring .  Many companies make   reliable equipment for  model railroad power.  Arm yourself with the current  Walthers reference catalog  , available from Walthers and also from local hobby stores  and checkout whats is available.   Good Luck. j2.

[Jim Banner]

Without an insulated box around those open terminals, I would not be connecting that autotransformer to 120 volts and having it sit on my bench, even if it is rated for 120 volts.  Getting a shock from line voltage is not always a minor inconvenience, unless you consider being dead a minor inconvenience.  Whatever you want to do with this unit, spend a few bucks and get a 4 x4 x 2 PVC box with lid, then drill holes in the bottom of the box to fit over those terminals.  Screw, glue or rivet the box in place, and keep the lid on except when you need to rearrange the connections inside. 


If you really want to use it for running trains, you could connect the input terminals (the two lower ones) to 120 volts through a 5 amp fuse.  Then connect the output terminals (lower left and centre ones) to the input of an 18 volt, 20 amp transformer.  Connect the output of that transformer to a 50 amp, 50 volt bridge rectifier and the outputs of the rectifier to some large scale track via a 20 amp self resetting circuit breaker.  This is a dandy way to control large scale trains, for example, a multi-unit lashup of locomotives, each with two or more motors, pulling a long string of lighted passenger cars.  Bridgewerks, for example, makes a large scale power pack with similar output for similar applications.  While many large scalers would give their eye teeth for such a rig, it has absolutely no application for controlling H0 model trains.

The only time I have ever heard of similar transformers being used with H0 model trains was by John Allen.  He rigged them up to control his train room lights.  By replacing the knobs with gear motors, he could have his lights dim and brighten gradually and automatically.  If you try something like that, build the whole works - autotransformer, gear motor and all - into a closed insulated box.  I think I speak for all of us here on Bachman's Board when I say we would rather be reading what you have been doing with your railroad than reading your obituary.

Jim 

[lessurbf]

I'm new to this board so I hope I'm not doing something wrong.  My question is where can I find the voltage/current requirements for an EMD GP40 diesel?

[RAM]

I don't know if this is what you are after or not.  16 volt max. and I amp dc.

[richg]

I have seen those autotransformers for sale with a three prong plug on a six foot cord is why I posted the reply. They plug into a regular wall outlet. Some have a three prong receptacle for output or the exposed contacts similar to your photo. There are literally dozens of ways these devices are made.
As was said, don't try what you are thinking.
Get a real train power pack until you learn basic electricity,  including at least 120 vac power as used in your home.
Questions like this really scare some of us here.

Rich