DC Treadmill Motor

[Marktal]

What effect will increasing the wire guage have upon a DC (140-180 Volt) perm magnet motor?
Our rewinding shop did the above job, but guage changed from .67mm to .75mm. They now have the treadmill back, it seems as tho the motor does not have enough HP. It struggles to get up to speed, or take load, without tripping internal c/board o/l. Also once 130 VDC and above applied direct to motor , motor comm/brushes spark.
Will change in guage effect HP and would it have these characteristics?

 

[Skogsgurra]

Only if the increased area made fewer turns necessary. And that is very likely since you now have a (75/67)^2 larger wire area, or about 25 %. It is often very difficult to squeeze in same number of turns when wire area is increased. Especially the tripping and commutation problems at lower-than-rated voltage indicate that you now have less turns than the motor was designed for.



Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

I agree with Gunnar;
With the larger wire you probably have fewer turns. larger wire and the same number of turns would reduce losses and improve speed regulation BUT with larger wire it won't fit. You can't get enough turns in the space available.
respectfully

 

[Marktal]

Apparently the rewinders got the same amount of turns as the original, only thing that changed was different gauge.
He did say it was hard to wind. I am amazed that he didnt think it was the wrong gauge.
SO the effects of the larger gauge, same turns? Will the motor lose HP? Mentioned was the motor losses would be lower, hence improved performance?

 

[stardelta]

Rule #1 when rewinding is "Dont change a thing" Major differences in turns and wire sizes alter the characteristics of the motor and very rarely does the practise make any benificial improvements without careful calculations. Going up a size or two on wire diameter will not increase performance, if it was that easy the makers would be doing it during manufacture. Some of the more acedemic members will be able to explain the exact effect an increase in conducter size will have.
Do not run the motor again and get your rewind company to rewind the "rewind" with the original and correct size wire and the problems will be solved. Incidently they have gone up 2 sizes, after 0.67mm comes 0.71mm then 0.75mm..... I am not surprised he found it difficult to rewind.

 

[edison123]

Changing to a higher wire size within the same slot is possible, if

1. If a better grade of slot insulation and wire insulation (requiring lesser thickness/cover) is used. This is fine and results in a cooler machine. I do it all the time.

2. By reducing the no. of turns - This is a no-no unless it is done with corresponding reduction in the rated voltage.

I think your rewinder goofed up on the turns despite his claims.




*Why a man thinks he outrun a chasing dog when it has twice as many legs?*

 

[Andreb]

Or the winder may have put the same number of windings in but the sparking, low power, and high current could mean he got the timing off on the comm by a segment or two.

These motors tend to be real cheap at surplus places.
_________
Andre' B.

 

[waross]

There is also a possibility that some of the winding insulation was cut by the laminations where it exited the rotor slots. That would be consistent with both "hard to wind" and sparking at the commutator.
respectfully