RE: [CAD_CAM_EDM_DRO] Re: AC Servo Motors and Drives

What you have are Brushless DC Servo Motors or sometimes referred to as AC
servo motors. The Gecko drives are for Brushed servo motors. Brushless
motors have three phases (the fourth wire is most probably a safety ground).
Commutation of the phases is done electronically by reading in the position
of the rotor and using math to compute how the electrons should flow in the
three phases to get the right magnetic field to align with the rotor.
Brushless DC motor Amplifiers are now as common as brush type amplifiers and
many of these amplifiers will accept either an analog or a step&direction
input as their brushed cousins do. You can look at Advanced Motion controls
or any of the motion control vendors to get amplifiers that run brushless
servo motors.
Madhu

>-----Original Message-----
>From: aussiedude36 [mailto:aussiedude@...]
>Sent: Wednesday, October 01, 2003 12:54 AM
>To: CAD_CAM_EDM_DRO@yahoogroups.com
>Subject: [CAD_CAM_EDM_DRO] 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