Centralized Modbus Architecture

Introduction

In a centralized Modbus architecture, the intelligent modular units (IMUs) are communicating to communication interfaces (IFE servers or IFM interfaces). The IFE servers and IFM interfaces are grouped in islands, mounted side-by-side on a DIN rail, and interconnected by the stacking accessory.

Centralized Modbus Architecture

The following figure shows an example of a centralized Modbus architecture with three IMUs:

• An IMU consisting of a ComPacT NS circuit breaker, and an IFE Ethernet switchboard server to get an Ethernet connection.

• An IMU consisting of a ComPacT NSX circuit breaker, an IFM interface, and an FDM121 display.

• An IMU consisting of a ComPacT NSX circuit breaker, an IO module, an IFM interface, and an FDM121 display.

Modbus Cable Connection

If there is no IFE server in the centralized architecture, connect the Modbus cable as shown in the following figure.

The Modbus cable coming from the Modbus client is connected to an IFM interface. It ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

Wiring Diagram

The following wiring diagram shows the connections for the Modbus cable and the 24 Vdc power supply:

For information about cable shield management, refer to the rules for Modbus connection linking several pieces of electrical equipment.

IFE Ethernet Switchboard Server Power Supply

When the IFE server is stacked to the IFM interfaces, the 24 Vdc power supply of the IFE server and the serial line Modbus communication are distributed to the IFM interfaces.

Wiring Diagram for IFE Ethernet Switchboard Server

The following wiring diagram shows the connections for the IFE server and the 24 Vdc power supply in detail:

Case of a Single Power Supply Segment

The following figure shows a centralized Modbus architecture with two cubicles and a single power supply segment:

Modbus Cable Connection with a Single Power Supply Segment

• The Modbus cable coming from the Modbus client is connected to an IFM interface. It ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

• The Modbus cable running to the second cubicle can be connected to any IFM interface in the group. It ensures continuity of the Modbus signal to the second cubicle and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

  The 24 Vdc power supply cable running to the second cubicle can be connected to any IFM interface in the group. It ensures continuity of the 24 Vdc power supply to the second cubicle.

Wiring Diagram with a Single Power Supply Segment

The following wiring diagram shows the connections for the Modbus cables and the 24 Vdc power supply in the case of a single power supply segment:

For more information, refer to Modbus connection linking several pieces of electrical equipment.

Case of Several Power Supply Segments

When more than one 24 Vdc power supply is needed (refer to segmented power supply), then several power supply segments are used along the Modbus cable.

The following figure shows a centralized Modbus architecture with three power supply segments:

Connection of Modbus Cable with Several Power Supply Segments

• The Modbus cable coming from the Modbus client ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

• The Modbus cable running to the second cubicle ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

  A separate 24 Vdc power supply is connected to the second cubicle.

• The Modbus cable running to the third cubicle ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

  A separate 24 Vdc power supply is connected to the third cubicle.

Wiring Diagram with Several Power Supply Segments

The following wiring diagram shows the connections for the Modbus cables and the 24 Vdc power supply in the case of several power supply segments:

For information about cable shield management, refer to the rules for Modbus connection linking several pieces of electrical equipment.