It is the armature current that flows through the brushes and the
commutator. Many DC motors have a motor field winding that is isolated from
the armature. This motor requires a current to flow through the field
winding. If no current, or too little current flows through the field, the
motor torque will be greatly reduced, as yours is. Some DC motors have the
field winding wired internally in series with the armature. If not, and the
controller also has a separate motor field current source built into it, it
could be the problem. Some DC motors have permanent magnets and do not have
a field winding and so don't require field current. You said the motor does
not overheat, so that indicates that it is not a loading problem. I guess we
need to know more about your motor and controller to troubleshoot this
further.
"ROBMURR" wrote in message
...
I have a Weslo 815 treadmill I am trying to find out why it bogs down
once I step on the tread belt...any suggestions welcome.
I got this used and want to fix it up.
Here is what I know. With the aid of my multimeter and the
troublshooting instructions inside my treadmill I find.
1. Motor DC 90 volt powered via motor contol board.
I cleaned the brushes and the armature with 1500 grit sandpaper
to smooth them up, they were arcing, now work fine.
Tested continuity all round the motor, looks fine.
Tested resistance all round the motor, about 3.5 ohms avg.
Cleaned any grease off belt pulley. No way to lube bearings
but motor shaft turns ok. Can run it to top speed without me
on it but bogs way down when I get on. Belt adjusted and no
slipping noticed. Motor does not overheat..
2. Controller board. All tests done on it show the motor is getting
volts and amps per the specs except the sliding speed control
specs say it should rise up to about 5k at max mine shows
up to about 9k ohms. At about medium speed the
amps are about 1.5 amps without me on it, when I get on it
the amps raise to about 2.75 amps as it slows down...
Once is slows down it never recovers to the proper speed...
At maximum speed it is getting about 2.5 amps which specs
say is correct....

So at this point I am thinking maybe the motor is going bad...
It is about 8 years old and really too small for this application...
Any other tests I can do?
Thanks
Rob