DC motor help

S

sparrow

Active Member
So I'm grinding some micarta scales today on my homemade treadmill motor grinder, around half the speed. And all of a sudden, It started going full speed, sparking from the rear end of the motor.. VFD controls are not working, I can't slow it down, I can't stop it on the stop button. There is some sort of emergency switch, and that worked.

Now, as soon as I click that main switch, motor starts full speed, sparkin' and all

I tried running VFD on it's own, motor detached.. it's behaving as it should, display working all controls responding. But when I attach motor, display not working and motor going full speed. I should mention, VFD is from the treadmill too, so it should (and did before this) start from the lowest speed and then i would adjust desired speed

Anyone of you guys have the slightest idea what is going on, I am f###ed up.. grinder gone crazy on me :(
 
The most common problems with DC motors are the condition of the brushes and communtator (the part of the armature that the brushes contact). I would take the motor apart and make sure that your brushes are not burned badly and the commutator is not shorted bar-to-bar. Clean the commutator by lightly sanding and brushing and check that there is not continuity bar to bar or bar to ground (shaft). Clean and lightly sand the brush faces or replace them- reassemble and check if runs after that.
 
Sparrow, a DC controller is not a VFD. VFD stands for Variable Frequency Drive and converts AC current (either 115v or 230v) to 230v 3 phase power. It is the 3 phase power that allows the speed control.

Treadmill motors are not sealed and depend on air being sucked through the motor for cooling. In doing this it also sucks the metal grindings into the motor and eventually will short out the motor. Since it still runs perhaps cleaning it out as Ausbrooks suggests may help and extend the life of the motor for a while.
 
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