Re: I want to cry !!! another fried Gecko + very, very hot motor,

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mike Mueller"
<mueller914@y...> wrote:

> used my mill last night for a few minutes, I made a few very light
> cuts, then the machine sat idle for about 30 minutes, I entered a
> command and nothing happened, I touched the motor (X is the only

axis

> hooked up right now) and i burnt myself.....fuse blown as well.
>
> I plugged the wires into a new motor and the trip light immediatly
> glowed red.(new fuse)
>
> What am I doing wrong? Is it a setting on the computer that is
> causing the motor to overheat? Once the motor overheats, does it

fry

> the Gecko(s) (340)?? my Y gecko wouldn't work as well
>
> who can i send the powersupply w/geckos, motors and computer to
> troubleshoot? I'm about ready to give up !!!!!!
>
>
> the motors are Litton (Clifton Precision-North)
> CPN JDH-2250-FQ-1C
> P/N 4798739
> D/C 9037
> I'm trying to find the specs of these motors, but so far, no luck.
>
> thanks,
>
> Mike Mueller
> Antioch, CA

Servo Motors get very hot for one of two reasons: Two much voltage
and/or two much current or too much load under full power. The 340's
are rated to drive up to 20A. Normally if you run the motor within
the voltage specs they will not draw enough current to burn up.
Since you don't know the specs on your motors how did you determine
what DC voltage to use? The best way would have been to take the
motors and hook them up to a variable supply and run them as DC
motors and monitor the heat. Because of thermal mass the heat takes a
while to build up. If it's too hot to leave you hand on it for
several seconds it's too hot. All of my servos run cool to the touch
under all but the most heavily loaded conditions and even then they
just get warm, not hot. Servo motors run at their appropriate
voltage will not self destruct (get hot enough to burn you).

Here is the possible scenero. The motor voltage is too high. This
will cause the motor to draw excessive current. If the current limit
on the gecko's is set high the motor will sit and cook. It actually
gets worse with no load since no power is being transmitted and it
all goes up as heat. Once the insulation in the motor breaks down
the motor windings short. Geckos will self destruct trying to drive
a dead short. At a minimum you will probably find one or more of the
power fets in the gecko are fried. Fried fets typically fail shorted.
Once the fets are shorted the gecko will just blow fuses.

Return the 340 to gecko and if need be pay Mariss to fix them. Test
your motors with sources that don't cost much. Geckos are very
reliable drives but they won't survive driving a dead shorted motor.

Don't put the gecko's back into the equation until you can determine
the voltage to run things at. The one motor that got too hot is
probably a lump of metal; don't use it. Hooking up another Gecko to
that motor will result in the same sequence of events (another dead
Gecko).