Re: [CAD_CAM_EDM_DRO] Servo Motor Types

IDA wrote:

>Hi Group
>
>I notice that there are encoders which also handle commutation on brushless motors. If one of these is used with a brushless motor, would it look like a brush motor from an electrical point of view, ie would it work with a Gecko drive.
>
>

yes, if you supplied an external 4-quadrant commutation box. Somebody
actually made brushless motors
that had a commutation controller so they could be dropped right into a
CNC system replacing a brush
motor. The commutation encoder just provides control signals to select
the commutation switches.
You would still need to provide those switches, which would be 6 large
power transistors.

>With brush motors, is it crucial (for use with a Gecko) to use a permanent magnet motor, or would a motor with field windings work. If so, which type of connection is required for the field windings.
>
>

You would need a motor with a shunt field, and no series or compound
field windings.
The field is often a lower voltage, and can be run off the main DC
supply with a big
dropping resistor. I have this on my Bridgeport. 75 V motors with 50 V
field. I don't
know what the Geckos will think if the field current ever fails to come
on, however.
My servo amps just fault with very little fanfare, but I'm not sure a
Gecko would.
it might just sit there at max current until it (or the motor) smokes!
I had intended to
put in a field safety relay but when I found out my servo amps handled
it so benignly,
I didn't bother. You might need to do such a thing to protect a Gecko,
however.

>
>

Jon