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Re: [TCML] Variable RSG
In a message dated 4/10/08 10:25:24 A.M. Eastern Daylight Time,
jimlux@xxxxxxxxxxxxx writes:
>I don't know if the inexpensive drives have a tach input and/or the
>phasing/sync input, but more expensive drives do. If you're doing
>something like a rolling mill or a web printing press, where you've got
>lots of motors that all have to operate as if they were "geared" then
>this capability is quite handy. Exceedingly tough to get to work if the
>load is changing, but a RSG is a pretty stable load.
Usually incremental encoders are used to provide a speed feedback signal,
although I've seen big DC tach-generators used on larger motors. Speed
regulation is on the order of 0.1% or better with encoder feedback. "Sensorless
Vector" drives do pretty darn well if they're tuned in correctly, maybe 1%.
You could also do things backwards, and run an asynchronous motor but
run the *power supply* off a VFD. It might be easier to tune the power line to
stay in synch with the rotary gap, but obviously that can get a little
expensive.
-Phil LaBudde
Center for the Advanced Study of Ballistic Improbabilities
**************Planning your summer road trip? Check out AOL Travel Guides.
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