[TCML] Variable RSG

[FIFTYGUY at aol.com]

In a message dated 4/10/08 10:25:24 A.M. Eastern Daylight Time,  
jimlux at earthlink.net 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



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