Alright.. using allenbradley 5000... i have a system to be controlled... which should satisfy the following conditions...
1- 3 pumps are there to pump water(lead, lag, standby)
2- maintain system pressure at a setpoint
3- system pressure varies according to downstream pressure
(a flow transmitter is there to take measurement)
4- when pressure decreases..means the downstream demand is high...
to maintain it, make use of speed controling of motor(ie speed increases)
5- when lead pump reaches 98% of its max speed, lag should start.
6- lead deacreases its speed and lag increases speed... when both come in a line(same speed)..now only it start to maintain the system pressure...
7- when both lead and lag are not able to control pressure... standby start...
8- when lead pump is not able to control high system pressure ie less downstream demand(require below min speed of lead pump) bypass valve open to maintain system pressure.....
I think i need to use a PID speed of motor....