Re: AC Servo Motors and Drives

Hi and thanks for your reply. I have read your reply a few times and
it has become apparent that I have no idea what you said. So perhaps
I can trouble you again or some one else may be able to help. My
gecko drives have a simple 2 wire output, pwm'd dc that reverses
polarity to change direction. This is normally connected to a DC
servo motor. My new motors say AC servo motor and appear to have 4
input wires not counting the encoders. I was told by some one who
may or may not be correct that AC servo motors use a kind of 3 phase
signal and that they do not have brushes. Is this true and does that
some how tie into the sinusoidally or trapezoidaly commutated stuff
you said that is wy over my head. Any body have ideas on a step and
direction iput ac servo drive?

Sincerely

David

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Madhu Annapragada"
<mapr@c...> wrote:

> When one talks about AC servo motors , it usually refers to the

commutation

> of the phases. If the commutation is sinusoidal then the motor is

referred

> to as an AC servo motor or a sinusoidally commutated DC servo

motor. If the

> commutation waveform is not mentioned explicitly, one assumes that

the

> waveform is six step or trapezoidal (using hall effect sensors

directly for

> the commutation information). That said, to run these motors you

can use

> both sinusoidal or trapezoidal commutation although the sinusoidal
> commutation has a number of advantages (lower cogging etc) and a few
> disadvantages (primarily the processing required to produce the

switching

> sequence for the six MOSFETS to produce a sinusoidal output). Most

servo

> drives support both types of commutation and I am not sure if the

Geckos do.

> Madhu
>
> >-----Original Message-----
> >From: aussiedude36 [mailto:aussiedude@e...]
> >Sent: Wednesday, September 24, 2003 1:18 AM
> >To: CAD_CAM_EDM_DRO@yahoogroups.com
> >Subject: [CAD_CAM_EDM_DRO] AC Servo Motors and Drives
> >
> >
> >Hi group, I have been playing with CNC stuff for a while and have
> >built a couple of systems with steppers and Dc servos utilizing
> >Geckos but I recently ended up with some AC Servo motors. As I
> >understand it they are kind of like 3 phase motors in the way they
> >work, 1) am I right & 2) are there any gecko / inexpensive type of
> >drives to run these motors using step and direction pulses?
> >Any direct answers or pointing in the right direction would be
> >greatly appreciated.
> >
> >David