Pump controlled by DCS – issues with motor start/stop
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I have a question for everyone: For pumps controlled by DCS, how is the starting and stopping of the motor achieved? The configuration in DCS handles the start and stop functions; but how is the start and stop of a specific pump controlled? Could someone draw a circuit diagram to explain this? Thank you
Simply put, the DCS program outputs a DO signal to the electrical system, which is the controller for the pump. When the pump’s controller receives this signal, it starts operating; if the signal disappears, it stops.
Where should the two wires going to the electrical side be connected? Is the signal sent by DCS just an on/off signal?
The start signal is sent by the DCS as a dry contact to the electrical system; through an intermediate relay, it is incorporated into the electrical pump-start control circuit to control the pump’s startup, and the same principle applies for stopping the pump.
The DCS outputs 2 dry contacts to the electrical system to control intermediate relays, and functions are achieved through these 2 intermediate relays.
The DCS has two output dry contacts: one normally open and one normally closed. The normally open contact is connected in parallel with the on-site start button, while the normally closed contact is connected in series with the on-site stop button; the output is in the form of pulse signals.
Ladder diagrams work on the same principle as PLCs