Re: [CAD_CAM_EDM_DRO] How close can the wires be ? - Advice needed.

ja_erickson wrote:

>Greetings,
>
>How far away from a 230 vac spindle motor do you have to keep a
>shielded encoder wire? or dont you have to worry about it.
>Can you zip tie a servo motor output wire and its encoder wire
>together or is this a bad practice.I'm concerned about noise
>and crosstalk and such. Generally speaking how far should I keep
>AC wiring from DC step and dir. wires, encoder wires etc.
>
>

It all depends on many things. A 230 V motor running from the power
mains will not produce much electrical noise except whrn the motor
is turned on, or especially when turned off - the break of the inductive
circuit causes the well known contact sparking, and the same high
Di/Dt and Dv/Dt events produce electrical interference.

The same motor running from a VFD can produce huge amounts of
noise whenever the motor is on, due to the 400+ V pulses produced
by the VFD.

A servo motor drive like the Gecko or Rutex have no output filters,
so the wires have very fast pulses of whatever the DC supply voltage
is on them.

Other servo drives may have output filters, and the noise level on the
output wires may be much less. My servo amps have 2-pole output
filters on each motor wire, and they work so well that you can use an
AM radio in the shop (not that I listen to AM radio much, but it proves
the point). I do have encoder wires bundled with these motor wires, and
there's no problem at all. Some people have had problems with encoder
noise pickup with Gecko drives. The newer G201A drives have filtering
on the encoder wires, which seems to have helped in this department.

Shielded wires from the encoders can help, and using differential signals
from the encoders can make them almost bulletproof.

Jon