Actuators with Fieldbus Controls( Two Wire Actuator Control Systems )
In the conventional hard-wired integral starter actuators, though the number of wires is reduced, still a few wires have to be run for processing the feedback & command signals to the Remote Control Centre (RCC). By adopting the Fieldbus System, these signals can be processed / transmitted through “Two-Wire” cables via an analogue to digital conversion card. A twisted pair cable is used for this purpose, which can be directly connected to DCS / SCADA system. Various options of communication protocols are available e.g. Profibus, Modbus, Interbus, Foundation Fieldbus etc.
The advantages of “Fieldbus System”:
The field wiring is substantially reduced. Ideally only two cables have to be run, one power supply cable from MCC to actuator and the other twisted pair (two-wire) control cable between RCC & actuator.
Being a close-loop system, the communication with master-station is not lost, even if there is a fault with one of the cables.
The settings can also be done locally from a laptop connected to actuator through an RS-232 serial interface.