Re: [CAD_CAM_EDM_DRO] Servo Motor Types

Thanks for the info. Jon

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, February 03, 2005 5:47 PM
Subject: 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
>
>
>
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