Re: [CAD_CAM_EDM_DRO] Re: Cooling Rutex drives

Excellent. That's exactly what I was looking for. It's more wattage than
I was thinking but it makes sense, and too much cooling is better than not
enough.
I think I'll save this post for future reference.

C|

On Mon, 19 May 2003, caudlet wrote:

> If you do a little "finger-in-the-wind" type engineering and figure
> that each motor will draw an average of about 450W (9A X 70V X .7
> duty cylce) and that Rutex motor driver is 70% efficient then 135W of
> heat is going to be generated. Given that part of the equation you
> can use the heatsink mfg's curves under the conditions you will have
> (forced air, free air, etc) to get a determination of the square
> inches of surface area you need in a heatsink. This is a rough way
> to do the numbers but it is better than holding your tongue on the
> unit until you have no feeling! Use some thermal grease between the
> Rutex case and the external heatsink to improve the thermal transfer.
> >
> > > 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.
>
> Basic RFI/EMI suppression techniques:
> 1. Keep leads as short as possible
>
> 2. Use Twisted Wires on wires that are low level signals
>
> 3. On power runs longer than a few feet use a large filter cap
> (1000MFD and up) close to the LOAD.
>
> 4. Low level signal wires are the most susceptable to external
> RFI/EMI and need to be run in shielded cable with the shield grounded
> at ONE END ONLY.
>
> 5. Each signal needs its own ground return wire. Have a single
> point ground in the Power Supply cabinet that all grounds terminate
> at.
>
> 6. If you put your motor drive modules in a cabinet away from your
> machine consider using shielded wire for the motor leads. Once again
> ground the shield at the motor driver module end. Don't run your
> encoder wires next to your motor leads, even if both are shielded.
> Keep a few inches separation.
>
> 7. Keep your machine ground and computer grounds separated. Use
> relays or opto isolators for logic signals from the machine (limit
> switches, etc) Use a separate isolated power supply for the
> sensors/switches.
>
> 8. Except on motor driver modules that have a common ground between
> the logic and the power circuit and non-isolated inputs, do not
> ground the negative side of your motor DC to the common ground in
> your controller cabinet.
>
> 9. In EXTREME cases find or make a good earth ground close to your
> machine and ground the machine to that. Run separate heavy copper
> ground wires from the machine chassis to this new ground. If you run
> non-differental encoder signals more than a few inches consider low
> pass filters on the signal lines. Do NOT make a connection from this
> new ground to the PC ground. RFI can creep through on the ground
> lines of the AC. A large common-mode filer on the AC line to the
> computer (it has internal filters that take care of most noise) can
> help but don't count on it to take care of all of the problem.
>
>
> While some have warned not to use any kind of Plasma Torch but the
> Hypertherm because of other units noisy start arc, I have a vintage
> Miller 500 running 15ft from my computer and it's next to my 6' X 6'
> plasma table. It took some careful attention to noise suppression
> but it works fine with both Gecko and Rutex servo drivers and a Gecko
> 201 on the Z axis.
> >
>
> >
> > Unfortunately I can't test the drives under actual conditions
> becuse the
> > machine is still in pieces.
>
> I have several machines in various states of upgrade...I understand.
> >
> > C|
>
>
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