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What would cause a engine motor to draw large current on no load?

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  • Member since
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  • From: Brisbane Australia
  • 568 posts
Posted by Alantrains on Thursday, September 24, 2020 6:16 AM

Update,

The replacement motor arrived from ebay (China) a few day ago (ordered on 12th August), and today I put it into the HH660. I had to shorten the shafts, which I did using a dremel cutoff disk, making sure the metal grindings didn't go anywhere near the magnets in the motor. I also filed the ends to a rounded shape like the original. I used a vice to press on the two brass flywheels and to press on the plastic universals. I tested that it ran smoothly after each step.  It now runs as good as new and on the short trains I usually run slowly on my small layout, it only draws 40 mA. At full slip it draws 280mA. Thanks to Trainman440 for the ebay link. I didn't find that the power was too low as RR-Mel suggested, but I don't run long or heavy trains. As you can see it has a nice switching speed.

https://youtu.be/r5oO-1UQDdE

 

Alan Jones in Sunny Queensland (Oz)

 

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Posted by Trainman440 on Sunday, August 30, 2020 12:28 PM

Hi Mel, it makes sense, you're comparing a mabuchi to a motor with no name. Also, the larger in diameter the coil is, logically, the stronger it is. As you stated, is issue is there generally isnt enough room. But I agree, they should start fitting larger motors into engines.

If companies started fiting gigantic motors into their engines like model power did in their E7s, they would be far more powerful and efficient!

OP, you can try to reassemble the motor. If the sprung brush contacts are an issue, I would try to remove them by taking off the end caps on the outside, carefully removing the springs, and sliding the brushes out.

MAKE SURE WHEN DOING SO to not let the springs fly out into oblivion!!!

Good luck!

Charles

---------------------------------------------------------------------------------------------------------------

Modeling the PRR & NYC in HO

Youtube Channel: www.youtube.com/@trainman440

Instagram (where I share projects!): https://www.instagram.com/trainman440

  • Member since
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  • From: Bakersfield, CA 93308
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Posted by RR_Mel on Saturday, August 29, 2020 11:44 AM

Trainman440

It seems pretty clear something is up with the inside of the motor. Ususally, there are some small tabs you can bend to remove/slide the shell off the motor.

 

Tabs located here:

From there, you can see the insides. Whether its a disintegrated magnet(it happened to me once), or worn out brushes, or tons of dirt on the commutator, any of the above(or others) is causing a lot of electrical/physical resistance to the motor. 

In general though, repairing a motor is very difficult, and if they break like your case, chances are there is something seriously wrong with the design. 

That being said, you can find them cheap on Ebay, for $4. 

https://www.ebay.com/itm/DC-12V-24V-22200RPM-High-Speed-5-Pole-Rotor-Motor-Long-Dual-Shaft-Axis-DIY-Toy/124195822808?hash=item1ceaa5dcd8:g:gJoAAOSwHt1b49-9

Good luck!

Charles

 

I ordered the motor you show in your post and it arrived yesterday.  After a few tests I found out it doesn’t have anywhere near the power of the Mabuchi FK-280SA 14200 motor at the same voltage (12).  If the Atlas HH600 has enough room for the Mabuchi it would be a much better replacement.



 


Mel



 
My Model Railroad   
http://melvineperry.blogspot.com/
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.

  • Member since
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Posted by Overmod on Thursday, August 13, 2020 7:56 AM

Look at all 5 sections of the commutator.  Are they all equally worn and 'shaded'?

Look at all the outer pole faces of the armature - are there any raised areas or drag marks?

Inspect the inside faces of the magnet to be sure nothing is adhering or clinging, and if there are any circumferential marks or tracks.

Just for grins you might want to rig up a poise with a couple of leveled knife edges and confirm that the armature is in balance.

You may need to make two small wire tools with L ends to hold the two brushes apart to get the armature back in that end cap.  When you do, turn it it to be sure there is no weird drag, then apply power across the brushes with a voltmeter in the circuit and rotate it to see if there are dead segments or poor continuity.  
I wonder if when they assembled this motor they put inadequate thrust washering on the commutator end?

With the motor back together spin it up at no-load and observe any strange behavior...

  • Member since
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  • From: Brisbane Australia
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Posted by Alantrains on Thursday, August 13, 2020 5:59 AM

Okay Here are some pictures of the disassembled motor. I couldn't find any obvious problems.

Thanks again for everyone's help.

Alan Jones in Sunny Queensland (Oz)

 

  • Member since
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Posted by Overmod on Wednesday, August 12, 2020 9:14 AM

This has all the hallmarks of a loose or fractured permanent magnet, or small piece of crap getting between the magnet face and the armature in the air gap.

I suspect if he sends us clear pictures of the commutator a number of people on here will know the 'electrical history' including dead or 'underperforming' windings pretty quickly.  This sounds mechanical to me, and is much of what's left if you're ruled out beatings or shaft alignment.

Usually you either use small springhooks to pull the brushes back or 'keepers' through slots in the end cap that hold them back and are then pushed out as the commutator is advanced between them.  This would have been done by machine or jig when the motor was assembled unless the brushes and springs were bonded in 'later'.  I confess I don't care for permanent motors with bonded-in unserviceable brushes...

  • Member since
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Posted by gregc on Wednesday, August 12, 2020 9:04 AM

Alantrains
It was still sluggish and drawing 0.5A to one amp depending on the speed controller. Then it suddenly sped up and the current dropped to 0.02amps which is what it used to be when I catalogued it a few year ago.

a motor is just a coil of wire with some resistance what would normally limit the current.  but a coil of wire rotating in a magnetic field produces a back EMF that limits the voltage across the wire, reducing the current.

in other words. if you put a voltage across a motor and prevent it from spinning it draws more current than when it does spin.

it seems like something was sticking causing it to spin slower.   it seems to draw an appropriate current when it can spin freely.

greg - Philadelphia & Reading / Reading

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  • From: Brisbane Australia
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Posted by Alantrains on Tuesday, August 11, 2020 11:38 PM

Hi again,

Motor is now in pieces and I'm pretty sure I can't get it back together. No obvious problems though.  The two thrust washers were a bit dry and a small amount of black dust in there. If I knew how to hold the brushes back so I could reinsert the amarture I might get it back together, but as I haven't found the obvious cause of the high current (no shorted turns on motor, nothing preventing rotation) I can't see the point in struggling with it. I'll wait for ebay to deliver.

thanks for all the advice and help.

 

Alan Jones in Sunny Queensland (Oz)

 

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Posted by SeeYou190 on Tuesday, August 11, 2020 8:07 PM

If the problem is with the armature/windings/commutator you might not be able to detect the failure with mechanical tests.

If the mechanism is not binding, there is a very good chance the new motor will correct the problem.

-Kevin

Living the dream.

  • Member since
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  • From: Brisbane Australia
  • 568 posts
Posted by Alantrains on Tuesday, August 11, 2020 6:29 PM

Thanks everyone,

this is always a helpful group.

I'm going to try pulling the motor apart, but have taken Charles's advice and have a motor ordered from ebay. It should arrive in Australia by mid October.

There doesnt appear to be any strong binding on the motor as I can turn the shaft manually although the motor doesn't continue to spin for long after I remove power so there is something wrong. With the two flywheels I would expect it to continue rotating for a lot longer. Now to remove the flywheels so I can take the end off and look inside.

thanks for all your help.

Alan Jones in Sunny Queensland (Oz)

 

  • Member since
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  • From: From Golden, CO living in Puyallup (Seattle), WA
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Posted by Renegade1c on Tuesday, August 11, 2020 2:38 PM

You may have a busted winding on the motor. If one of the windings in bad it will cause motor to be sluggish and not want to turn over. Same concept as a spark plug not working in a internal combustion engine. It takes extra force on the other windings to get motor to turn past that single winding that is out. 

IF you can get motor apart, an multimeter should be able to tell you if the winding is bad by performing a continuity check on each one. Typically most of our hobby motors are 5 pole, meaning there are 5 sets of windings.

Check each set of continuity. 


Colorado Front Range Railroad: 
http://www.coloradofrontrangerr.com/

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Posted by PRR8259 on Tuesday, August 11, 2020 11:46 AM

Many of Broadway Limited Imports earlier run Paragon 3 engines (not the Paragon 2 engines which are allegedly ok) have badly manufactured motors that send way too much current to the decoder, causing the decoder to fail.  It can exceed 2 amps no load, which fries the motor control circuit in the decoder (in a couple days of use).  Sometimes BLI just replaces the Paragon 3 decoder with a new one that is "designed" to handle the increased amperage from the motor, but even then some of them are failing, and engines have to go back for repair a second time to get the motor replaced.  The local train stores I frequent are reporting relatively "large" numbers of Paragon 3 failures.

Rather than waiting for BLI's service backlog, possibly two separate times, I sent my son's UP challenger to Seneca at Train Service Depot and ended up having both the crappy P3 decoder and the motor replaced and had the engine back in about 2 weeks flat (but the repairs were not free, however, we avoided possibly 20 weeks of waiting).

Once the Paragon 3 engines are repaired, they run very well indeed.

The one brand new UP 4-6-6-4 I sent to Seneca was drawing 2.2 amps no load prior to replacement of the motor.  That is why Seneca replaced the motor and the decoder.  The engine runs fine now and everything works as it should.  It easily exceeds 60 freight cars on level track now.

John

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Posted by riogrande5761 on Tuesday, August 11, 2020 10:00 AM

A manufacture flaw could cause it.  Many may remember the first run Proto 2000 PA's had motors with a high amp draw which could be a problem if converting to DCC.

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by Trainman440 on Tuesday, August 11, 2020 9:43 AM

It seems pretty clear something is up with the inside of the motor. Ususally, there are some small tabs you can bend to remove/slide the shell off the motor.

 

Tabs located here:

From there, you can see the insides. Whether its a disintegrated magnet(it happened to me once), or worn out brushes, or tons of dirt on the commutator, any of the above(or others) is causing a lot of electrical/physical resistance to the motor. 

In general though, repairing a motor is very difficult, and if they break like your case, chances are there is something seriously wrong with the design. 

That being said, you can find them cheap on Ebay, for $4. 

https://www.ebay.com/itm/DC-12V-24V-22200RPM-High-Speed-5-Pole-Rotor-Motor-Long-Dual-Shaft-Axis-DIY-Toy/124195822808?hash=item1ceaa5dcd8:g:gJoAAOSwHt1b49-9

Good luck!

Charles

---------------------------------------------------------------------------------------------------------------

Modeling the PRR & NYC in HO

Youtube Channel: www.youtube.com/@trainman440

Instagram (where I share projects!): https://www.instagram.com/trainman440

  • Member since
    January 2009
  • From: Bakersfield, CA 93308
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Posted by RR_Mel on Tuesday, August 11, 2020 7:48 AM
If it has had a lot of run time it could be badly worn brushes.  If lubing the motor bearings doesn’t help check the brushes.

 

 
Mel

 


 

My Model Railroad   

http://melvineperry.blogspot.com/

Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.

 

 

 

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Posted by woodone on Tuesday, August 11, 2020 6:58 AM

I would try lubing the motor bearings.

TheY may be dry, use a good lube.

  • Member since
    January 2003
  • From: Brisbane Australia
  • 568 posts
What would cause a engine motor to draw large current on no load?
Posted by Alantrains on Tuesday, August 11, 2020 6:49 AM

Hi all,

I have and Atlas HH600 Silver series with DCC non sound decoder. It has been a great little loco for years now. I noticed the other day that it seemed sluggish and as I am going through servicing my engines, I lubed it and did a test run and noticed the DCC decoder was very hot. My Powercab indicated it was drawing more than half an amp even on slow speeds. So I disconnected the decoder and the drive shafts and clipped some DC leads onto the motor terminals. It was still sluggish and drawing 0.5A to one amp depending on the speed controller. Then it suddenly sped up and the current dropped to 0.02amps which is what it used to be when I catalogued it a few year ago. It ran fine until I changed polarity to run the motor the other way, then it went back to 0.5A and slower speed. I was able to repeat this one more time. I'm not sure what caused this. Perhaps something magnetic is loose inside the motor.  I haven't figured out how to remove the motor yet to see if there is anything obvious causing the problem. The motor also gets very hot when it draws the high current.

Alan Jones in Sunny Queensland (Oz)

 

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