explain Cascade Control strategy with the help of a block diagram. also exlain

explain Cascade Control strategy with the help of a block
diagram. also exlain its working in a distillation column

Question Posted / abhinav prateek

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explain Cascade Control strategy with the help of a block diagram. also exlain its working in a di..

Answer / inbu raja e k

cascade control strategy is the one in which you have 2
control loops, a primary loop and a secondary loop. The
output of the secondary controller will the reference or
set point to the primary controller.
Cascade control is most advantageous on applications where
the secondary closed loop can include the major disturbance
and second order lag and the major lag is included in only
the primary loop. The secondary loop should be established
in an area where the major disturbance occurs. It is also
important that the secondary variable respond to the
disturbance. If the slave loop is controlling flow and the
disturbance is in the heat content of the fluid, obviously
the flow controller will not correct for this disturbance.
In distillation column it is used as a composition control
where the feed flow is the primary control and condense
flow out is the secondary loop