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Subject: Re: ac servo vs. ac inverter
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Date: 09/25/02 at 8:55 PM
Posted by: Barry Penter
In Reply to: ac servo vs. ac inverter posted by jim on 03/13/02 at 3:34 PM:
You can in fact get very dynamic control similar to servo control by using an AC inverter if your inverter is equipped to do Vector Control. I am running AC Inverters with Closed Loop Vector control on machines that control the movement of metal strip over any length and achieving an accuracie of +/- 0.8mm accuracy on all movements requested.
Of course, this is related to the type of controller used but the point is that the Vector Controlled Variable Speed Drive (Inverter) is capable of achieving this.
Some manufacturers of inverters have algorithms for both Closed Loop and Open Loop control, but you have to test them to see if they work adequately. In my experience this is not always the case.
With Closed Loop systems it is necessary to have some form of feed back from the motor to tell the drive its responses to VSD commands. In Open Loop, the drive calculates from the voltage and current, among other things, the likely responses.
In my opinion, both systems will perform but the standard 3 phase motor and ac inverter is a hell of a lot cheaper.
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