Treadmill motor - power loss

Thread Starter

Elijahwww

Joined Sep 18, 2013
1
I have a treadmill that lost 80% of its power. When i put any load on it (walk on belt), it starts arcing quite a bit and makes noise in proportion with the speed. The motor runs seemingly fine without load at all speeds. At lowest speed I can stall the motor with just a single finger on the belt. But if I rev up the motor to say 50% of its max speed (running speed), I can then do walking pace as the motor labors.

I took the motor apart and did not find anything apparent. The commutator is a little dark, but i can still tell its copper.The segment partitions are black, very narrow. 0.6mm maybe. Brushes are large, 1.5cm in length still, a little charred on one edge. Winding seems ok, but a little dark in some area. I can't tell if that is from lacquer or what. It never smelled burnt. Reed looks ok too. The motor has permanent magnet, spec sticker states 17.5 A, 145 VDC, 5700 rpm, external fan.

Both walking and drive belt tension is just above slipping at this point. I wanted to make sure it wasn't tensioning.

I took the board out, just to give it a visual inspection. I didn't see any resistor charred.

I could use some suggestions. How do I isolate the problem.
 

MaxHeadRoom

Joined Jul 18, 2013
19,425
First try the motor on the bench using an Automotive battery, if the brushes are off set, it is a Uni-directional motor, so the correct polarity will be needed, otherwise you can test it in both directions.
Apply a load if at all possible and or see if you can stop it.
Max.
 

wayneh

Joined Sep 9, 2010
16,128
Measuring current draw might help. I once had a car starter that spun just fine on the bench but wouldn't start the car. Of course this was going on in the depths of winter.

Turns out one of the two windings was open. The problem was easily revealed by a low current draw - about half of spec.
 

MaxHeadRoom

Joined Jul 18, 2013
19,425
Measuring current draw might help. I once had a car starter that spun just fine on the bench but wouldn't start the car. Of course this was going on in the depths of winter.

Turns out one of the two windings was open. The problem was easily revealed by a low current draw - about half of spec.
Mmmm...Starter motor is a series wound motor, runs at uncontrolled RPM off load, must have had parallel fields for it to run with one open?
Max.
 

wayneh

Joined Sep 9, 2010
16,128
Beats me. It was a '67 Barracuda.

Holding a wrench while laying under the car on my back on an ice patch below 0°F is the part I remember most clearly. That and the aha moment when I finally took it out again and had it tested at the auto parts store.
 

MaxHeadRoom

Joined Jul 18, 2013
19,425
Interesting trivia is that when the idea of a series motor be implemented for car engine starting, it was predicted by many that it would burn out after just a few operations.
I guess time has proved them wrong!
Max.
 
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