# Modelling Steam generator with P controller and 4-20mA signal to valve

by jakub.gongol
Tags: 420ma, controller, generator, modelling, steam
 P: 4 Hi . I am modeling a sodium steam generator in Octave. I build a set of differential equations and solve them with Octave DAE solver. My model works just fine. Now i would like to start implementing controls but I am quite confused with P conroler output signal and with what it actually controls For example: I am trying to control the level of water in the boiler . Mesuared value is 4-20mA signal that represents water level. What I want to control is valve that throttles the Feed water dpump discharge. I implemented a control equation: t= time [s] l= water level [m] l_set =required water level [m] f=Kp*(e)=Kp*(l_set-l(t)). I know that the The characteristic of the valve is linear (4mA(0% open) - 20mA(100% open)). What is the relation between value f and the signal that i send to the valve. Do I send the f to the valve?? That does not seem right since when e=0 then f=0 I would be telling the valve to shut to 0% open when the error is 0.(neglect the 4mA signal...I can add bias) That is not right or is it?? How can I model this problem with a differential or algebraic equation?? Thank you Jacob