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Re: [TCML] Variable RSG



 
 
In a message dated 4/9/08 3:52:55 P.M. Eastern Daylight Time,  
wavetuner@xxxxxxxxx writes:

>What about using one of the heavy reactors that go out to the  motor? I have

>couple that are meant for three phase setups that I got off Ebay  pretty

>cheap. I think they are meant to protect the VFD and keep noise  from getting

>back into the wiring plant. I suppose RF would go right around it  though.

>They are definately Heavy Duty!  Thoughts?


    Load-side (drive output) reactors are definitely a  help in limiting peak 
voltages seen by the motor, and are mandatory for long  runs of cable between 
the drive and the motor. Safety margin depends on the type  and length of 
cables used. Allen-Bradley also makes some load-side filters,  which from the 
description I've always assumed are some type of solid-state  transient 
protectors. I'd guess either of these will help mitigate voltage peaks  getting back to 
the drive. 
    But I agree with you that I'd also question how  effectively the simple 
reactors would block RF. Granted, a 5% reactor on a 2HP  240VAC drive is a 3mH 
choke, but I'd like to see test results before I'd trust  an open-frame 
multi-layer choke to "completely block" RF.
    Drive manufacturers also offer EMI/RF filters,  especially for strict 
European installations. 
 
-Phil LaBudde

Center for the Advanced Study of Ballistic  Improbabilities



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