Tachometer Follower Application - Emerson Control Techniques Focus 3N User Manual

Focus 3 Drives in Tachometer Follower Application
There are many applications that require a second drive to follow the speed of
the first (or primary) drive. There are two basic methods used, the first is a parallel
method and the second is a cascaded method. In the parallel method the speed
command of the first drive is sent directly to the second drive (as a speed command)
while in the cascaded method, the speed feedback (tachometer) is directed to the
second drive as a speed command. A disadvantage to the parallel method is that if for
some reason the first drive slows down while in a current limit condition, for example,
the second drive would no longer follow since it may not be in a current limit condition.
This is not the case for the cascaded method since the drive is following the actual
speed of the first drive.
Master
The Focus 3 isolator option
since it is powered directly by the Follower drive and connections are minimal.
Page 66
C TAN #130
(F3NSBD)
Focus Isolator
Focus 3 Non-Regen Drives
(p/n F3NSBD) is ideally suited for this purpose
s
Follower