Re: Synchronizing Variable AC Drives with Different Ratings
04/10/2009 6:25 PM
What do you mean by "synchronize"? Two VFDs trying to run one motor? Or two VFDs running 2 separate motors at the same speed? Or Two VFDs with separate motors connected to the same load trying to share the load?
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Re: Synchronizing Variable AC Drives with Different Ratings
04/12/2009 9:34 AM
What are you synchronizing? Shaft position or speed?
Synchronizing speed is relatively easy compared to synchronizing position when using VFD (variable frequency drives).
We used to have a process that required speed matching of two conveyors. However, in addition to matching speed, they also needed to be synchronized (the conveyors, not the motor shafts). We used two incremental encoders and a PLC that was dedicated just for the snchronizing. We wanted the shortest and the least variations in the PLC's scan time to avoid complications. We also used sensors for sensing the positions of the conveyors. Timers in the PLC calculated how much phase difference there was between the conveyors.
It was a tough little project but we finally got it working well.
regards,
Vulcan
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Re: Synchronizing Variable AC Drives with Different Ratings
04/11/2009 11:15 AM
To get position and speed sync. there are position controllers called virtual shafts. They work relatively well as long as the speed changes are gradual. They are often used in web drawing between isolated machine sections.
You can also use a dancer/accumulator control between the sections.
If you need exact position control with fast speed of response, you must look at servo-controls.
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Re: Synchronizing Variable AC Drives with Different Ratings
04/14/2009 2:36 AM
Vary the speed of one of the two so that the output waveforms are in phase. Then throw the switch when they match.
The equipment used to do this is sometimes called a "synchroscope".
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Synchronizing Variable AC Drives with Different Ratings
Re: Synchronizing Variable AC Drives with Different Ratings
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