Re: [CAD_CAM_EDM_DRO] Brushless DC motor.....

Jon..... I do have or will have the matching drive, won it on e-bay, I am
not sure it can take step and direction signal from the current system that
I have, but if it can, just maybe it will be a winner...does this help, can
you shed some more light on this? Do you know if the Vexta gear head that
come with the motor (vexta 5gd30k) would have backlash, and also the gear
ratio?


Thanks,
Russ

----- Original Message -----
From: Jon Elson <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, April 09, 2002 12:01 AM
Subject: Re: [CAD_CAM_EDM_DRO] Brushless DC motor.....


> RC wrote:
>
> > Does anyone know if the Vexta Brushless DC motor, sample model
#BLD1524-F, is the same as a dc servo motor? Any information about how they
would work in a cnc application also.
>
> It is really not a DC motor. It is essentially a permanent magnet AC
motor. The only
> true DC motor uses brushes. (yes, some purists may flame me over this.)
The term
> "Brushless DC" motor was coined when those motors were used in fans,
because
> they are treated as if the were brush motors, except there are no brushes
to wear out.
> When you want to reverse it, or extract energy when braking, then it gets
a LOT
> more complex, and 2 wires won't do it any more. So, these motors have 3
power
> wires, generally, and more for the encoder that at least tells the drive
which windings
> need current in which direction.
>
> Generally, you need a brushless servo motor drive to use these motors.
because
> the arrangement and phasing of the encoders are not completely standard on
these
> motors, it is pretty risky to try using motors from one manufacturer with
drives from
> someone else. So, for most applications, consider the motor and drive as
a package.
>
> They work fine for CNC, have longer, trouble-free life than a PM brush DC
motor,
> although that is not likely to be a concern for hobby and small-shop class
machines.
>
> Jon
>
>
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