On Tue, 8 Jan 2013, Viesturs L?cis wrote:

> Date: Tue, 8 Jan 2013 21:28:48 +0200
> From: "[UTF-8] Viesturs L?cis" <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
>     <[email protected]>
> To: "Enhanced Machine Controller (EMC)" <[email protected]>
> Subject: Re: [Emc-users] LinuxCNC craziness
> 
> 2013/1/8 Peter C. Wallace <[email protected]>:
>> On Tue, 8 Jan 2013, Viesturs L?cis wrote:
>>>
>>> Should I get a ring for each lead or should I use all 4 leads of each
>>> motor on one ferrite ring?
>>> And is it enough to simply run them through the center or should I
>>> wrap it around at least once (put through center, wrap around and once
>>> again through center in the same direction as first time)?
>>
>> You should put the U/V/W wires (not the ground) from one channel all through
>> one ring (this is what called a common mode choke it has 0 net current flow 
>> so
>> does not saturate from the motor current)
>>
>> The point of this is to add some series impedance to the (very stiff) 28V
>> square wave driving into the cable and motor stator winding/frame
>> capacitance. This limits the amplitude of the current spikes created by
>> driving into this capacitance.
>
> Thanks for the explanation! So is it enough just to put it through
> once or should I wrap at least once around the ferrite?

This depends a lot on the ferrite characteristics. You will probably have to 
experiment.

>
> Since previous replies have got me into considering of replacement of
> motor wires to something with a shield, I have a question - what would
> be minimum recommended wire lead "thickness" (I mean the area in mm^2)
> for 7i39 drive?


the 7I39 can supply 10A continous max through one phase so 14 Ga is about 
right but 12 Ga would be better (~2 to 3.3 MM^2)

>
> -- 
> Viesturs
>
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
>
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Peter Wallace
Mesa Electronics

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