Re: [CAD_CAM_EDM_DRO] Re: [DIY-CNC] need transmission ideas / advice re: gantry

Re: heating.
This is probably the case sometimes.
I dont see it, at 48 V, in servo use.
I dont see it, at 24 V, in testing.
And if I do see it, I will use a small cheap basic 24 V computer fan
(rackmount fan) and thats it.
The cooling is a non-issue (for me, in this case).
These are practical real-world observations.

The heat might be a problem if;
-I had longer use
-It was not outside in a metal enclosure (total airflow and very large
metal case surface volume)

As Mariss of geckodrives said somewhere, the heat really builds up at
high voltages.


Danny Miller wrote:

> The overheating is more possible than you think!
>
> For example, your motor is rated at 130V DC 18.5A 6000RPM.
> At 24v, you should get 1107RPM. IIRC the fan's cooling capacity is the
> square of the RPM, so it's like 3% effective, so basically nothing.
>
> Now there's two losses here, one is core loss which is complicated to
> calculate but DC I^2*R wire losses are not.
> You might load the motor down at 18.5A at 1107 RPM. That's "legal" and
> only consumes 444W. This will produce torque comparable to the torque
> at full load at 6000 RPM.
> The I^2*R losses are now exactly the same as the 130V full-power case,
> BUT the cooling is reduced to nothing (or maybe I was wrong on the
> squared basis, maybe it's just linear- in which case we have 18% fan
> cooling power).
>
> So, you have a serious cooling problem! It "might" overheat in a minute
> or two, it's hard to say. Depends on how much extra cooling that motor
> had. Probably ok.
>
> The treadmill motors usually have a fan on the pulley output+flywheel.
> In fact you may not even have one at all, some surplus mfgs don't ship
> the heavy flywheel. In which case you don't even have the fan in the
> first place.
>
> The 24v scooter motor makes much more sense.
>
> Danny
>
> gcode fi (hanermo) wrote:
>