Re: [CAD_CAM_EDM_DRO] Re: Hot servo motor

----- Original Message -----
From: "k8zre" <rfs@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, April 27, 2004 7:09 PM
Subject: [CAD_CAM_EDM_DRO] Re: Hot servo motor


> Follow-up on Hot Servo...
>
> Y axis servo running hot but functioning. Thought I would re-tweak
> the Kp Ki Kd...set all values to zero to retune. Zzzapp! Fried
> the Y axis driver ... actually went up in flames. Checked servo ...
> 2.2 ohms on windings per spec sheet and when motor moved by hand,
> stays at 2.2 ohms ... didn't find any shorts. Exchanged
> driver...reconnected...Paff! goes another board. Needless to say the
> servo motor is now history. Checking with Rutex to see if boards
> repairable. Other axes work fine. What's the moral to this story?
>
> Regards ... rfs.
>

Sounds like you could have a shorted turn in the motor. One shorted
turn will not change the resistance much. If you can see the commutator,
you should see two segments that show more arcing than the others.

If you can spin the motor with something like an electric drill and connect
the wires to an oscilloscope you will see a pulse in the voltage when you
hit the shorted turn. If you compare the suspect motor with a known
good motor the difference should be obvious.

If you put DC voltage on the suspect motor and on a good motor, the
suspect motor will run much slower.

Pete.