Re: [CAD_CAM_EDM_DRO] Re: Cap at the Gecko, motor heating, fuse protection??

Polaraligned wrote:

>
>So one should look at the total power dissapated by the motor,
>not just the current going through it, when trying to protect it.
>This sounds like good reason not to go over the motors rated
>voltage as some would advocate. Even with the current limiting
>of the driver, the power that the motor may be able to dissapate
>may be overstepped (when using a higher than rated voltage). I guess
>one could figure out how much the motor can dissipate safely, and
>lower the current limit of the driver- Get higher RPM's by using a
>higher voltage, and in return set the current limit lower.
>Does this sound right?
>
>

Well, that's the problem! Power levels well within the continuous ratings
of the motor WILL destroy it if the power is not getting out of the motor.

In other words, say the motor's continuous torque rating allows it to
produce
250 Oz-In. You can feed the motor a current that produces that torque all
day without harm. You can figure out what POWER level that is, by
multiplying
the current by the voltage drop due to the winding resistance. But,
when the motor
is spinning at a high speed, the POWER into the motor will be far greater!
The continuous current should not be exceeded for more than a second or so,
ever. So, that is the real limit - current or torque, NOT POWER!

If you try to watch the iput power, you need to also watch the OUTPUT power,
to know how much heat is being generated.

But, an RMS sensor based on the current will produce a pretty accurate
picture
of the heating that is occurring in the motor. Motor heating is
proportional to
current squared, not power into the motor.

Jon