Cascade control system
In some process two or more process variables effect equally on the behavior of each other where on is controlled with the control combination of another
For these kind of process the cascade control is used
Cascade control is a type of control terminology in which a process variable is
controlled by control combination of two process variables
In cascade control two process variables are controlled with a single final control element
In this control system one controller is recognized as master controller and the other as slave controller
The master controller is given a setpoint by operator and its out put becomes the setpoint of the slave controller and output of the slave controller goes to the final control element
Therefore any change of any process variable creates the change in final control element position therefore process is controlled by control combination of both process variables
Following a type of cascade control is given
(in this system temperature is controlled by controlling the flow)
Here burner temperature controller is used as master controller and fuel flow controller is used as slave controller where temperature controller’s out put becomes setpoint of the flow controller and finally out put of flow controller goes on the fuel flow control valve
Hence controlling the flow of fuel the burner’s temprature is controlled
