Re: shielding for steppers

Peter,

Good evening! The only reason for shielding step motor leads is to
prevent noise from bothering other stuff (limit switches, etc.). The
motor runs open-loop and is not bothered by noise in the slightest.

I would consider using "Cat 5" cable for the motor because it is
universally available, cheap and has a bunch of conductors within the
cable.

Use two twisted pairs for the motor phase leads, a seperate pair to
ground the motor case back to the drive ground and of course ground
the shield wire at one end only. This will keep noise from the
motor/drive combo from injecting itself into everything else.

Interestingly enough the wire resistance has very little effect on
performance. This is because step motor current is at a maximum at
low speeds and drops to low levels at high speeds.

The cable will have the highest voltage drop (due to resistance) at
low speeds where it does not matter. At high speeds (where it does
matter) the voltage drop will be much less due to reduced current
draw from the motor.

Ultimately all that matters is the cable temperature. If it feels
very warm to the touch then it may be too small in wire gauge size
for the application. If it is cool to warm, then everything is OK.

The above does not apply to servo motors. There having the minimum
wire resistance is very important for maximum torque.

Mariss

--- In CAD_CAM_EDM_DRO@y..., cncnut@s... wrote:
> Hi all,
>
> Been struggling with a little problem and hoping to get some
insight
> from the group.
>
> It seem to me that only servos with encoder need shielding for the
> cable to the motors. But do steppers need shielding. It appear to
be
> unnecessary?
>
> Thanks
>
> Peter