Re: [CAD_CAM_EDM_DRO] Re: Cooling Rutex drives

On Sun, 18 May 2003, caudlet wrote:

>
> The amount of cooling depends a lot on several factors. The voltage
> of your DC power supply, the total average current of all your motors
> and the physical environment you are running in. Which Rutex drives
> do you have and tell us the voltage and currents involved and a more
> accurate answer can be formulated.

What? You mean you can't read my mind? ;-)
I have 3 of the 990H's. The power supply is ~70V and continuous current
for each motor is 9A.

> My unscientific method of telling if I need more heatsink is to run
> the unit under worse case conditions for 15 minutes. If I can hold
> my hand on the actual heat producing object without being
> uncomfortable then I am satisfied. Although mfg's normally rate
> their components to run at 100 deg C that is the internal die temp
> and that is not the final external temp.

Hmm, that would tell me I definitely need a heatsink. I set up one drive
and motor on the bench just for tuning and the drive got warm even at
that. Not uncomfortably warm, but warm.

> All that being said, it would be a good idea to plan a custom bracket
> for you drives that includeds a heatsink as least as large as the
> Rutex open case surfaces with at least .75 inch tall fins. Forced
> air cooling is probably in order. If you do not use a fan directly
> on the heatsinks make sure the fins are mounted vertically to let
> natural convection remove the trapped air between the fins.

That's mostly what I wanted to know, how much heatsink to use. I'm
familiar with at least the basics of thermal design so if I had an
estimate of the power dissipation of each drive I could figure out a
reasonable size heatsink.

> A little attention to heat removal and RFI suppression on the inital
> design will save you having to redo it in the future.

Hmm, I would welcome your thoughts on RFI too.

> I have several Rutex units most of which are still in the bubble wrap
> waiting to go on my full size mill conversion. I am running one 990
> servo drive on a plasma table but the rest of the drives are Gecko's.
> I have minimal heatsinking because my servo's only draw 2 Amps each.

Unfortunately I can't test the drives under actual conditions becuse the
machine is still in pieces.

C|