Why IRP Used for Interface Between DCS and MCC


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Why IRP panel is used between DCS and MCC?

As there are intelligent MCC is there any option of MCC sensing 24 VDC signal from DCS and providing 24 VAC to drive the motor?

> Why IRP panel is used between DCS and MCC?

I presume by "IRP panel" you are referring 'Interposing Relay Panel panel.'

Most of the time when interposing relays are used between discrete outputs of a DCS (or PAC--Programmable Automation Controller, or PLC--Programmable Logic Controller) it's because the outputs are solid-state outputs and incapable of handling the current which will flow through the circuit when energized or during de-energization when there may be an inductive "kick."

I also presume by "smart MCCs" you mean an MCC which is capable of PROFIBUS or CAN or some other automation protocol. Sure; that's possible, but sometimes it's a more expensive option from both a hardware and software perspective.

Hope this helps!

I believe CSA has answered it perfectly.
But again, by VAC do you mean the motor should be driven by 24 V AC?

Normally a single Phase motor works in 230V, 50Hz (Except some countries like US/Canada where it would be 110V,60Hz) AC. Transmitting 24 VDC signals over large distances is not a wise option as can have a lot of interference. you may have to employ multiple repeaters and filters to achieve the same. (which is possible though).

Employing an IRP in between helps keeping this signal intact for long distances.

Many other modbus/profibus communication schemes are used for the same.
IRP houses Interposing Relays. The reason for using interposing relays are:

1) To electrically isolate two systems with different voltage levels (e.g., DCS @ 24V, MCC @ 220Vdc, or 230Vac 0r 110Vdc). If there is any short circuit or any electrical disturbance at MCC side, Interposing Relays shall protect DCS from them and vice versa.

2) To increase the driving capacity of the final control element like Solenoid coil, MCC contactor etc.