Modbus Connection Rules

Introduction

The Modbus client can be installed either:

• In the same electrical equipment as the IFM interfaces or in a separate section of electrical equipment from the IFM interfaces where the two sections of equipment are bolted together.

• In a separate section of the electrical equipment from the IFM interfaces where the two sections of equipment are not bolted together.

IFM interfaces with part number LV434000 and TRV00210 can be installed on the same Modbus-SL network.

Connection of IFM Interfaces to Modbus-SL Client

Connection to the Modbus-SL client depends on the number of IFM interfaces:

• To connect a single IFM interface, use the RJ45 Modbus T-junction.

• To connect several stacked IFM interfaces, use the RJ45 Modbus cable.

• To interconnect several isolated IFM interfaces, use one of the following:

  • The Modbus splitter block LU9GC3

  • The RJ45 Modbus T-junction

Modbus-SL Network Contained in Electrical Equipment

The Modbus-SL network is contained within the electrical equipment when both conditions below are fulfilled:

• The Modbus-SL network between the IFM interfaces is connected to the Modbus client (a PLC, for example) or to an IFE Ethernet switchboard server integrated in the electrical equipment.

• The Modbus-SL network between the IFM interfaces does not exit the electrical equipment to extend to another electrical equipment.

The Modbus client or the IFE server can be connected directly to the Modbus-SL network of the IFM interfaces in the electrical equipment.

Examples of a Modbus-SL network contained within the electrical equipment are provided:

• Wiring diagram including IFM interfaces grouped in islands and Modbus client installed in the electrical equipment

• Wiring diagram including IFM interfaces in daisy-chain or star connection and Modbus client installed in the electrical equipment

• Ethernet connection linking two pieces of electrical equipment.

Modbus-SL Network Not Contained in Electrical Equipment

The Modbus-SL network is not contained within the electrical equipment when either:

• The Modbus-SL network between the IFM interfaces is connected to a Modbus client outside the electrical equipment.

• The Modbus-SL network between the IFM interfaces exits the electrical equipment to extend to another electrical equipment or another section of electrical equipment where the two sections of equipment are not bolted together.

Connection rules are detailed in Modbus connection linking several pieces of electrical equipment.

Examples are provided for wiring diagrams including IFM interfaces grouped in islands and Modbus client installed in a separate section of electrical equipment from the IFM interfaces where the two sections of equipment are not bolted together:

• With 0 V of power supply floating

• With 0 V of power supply connected to local ground

Modbus Connection Linking Several Pieces of Electrical Equipment

The rules below must be followed when the Modbus client is installed in a separate section of electrical equipment from the IFM interfaces where the two sections of equipment are not bolted together:

• Each Modbus segment installed in two sections of electrical equipment not bolted together includes a polarization at one point, and a Modbus line termination at each end:

  • The line polarization and a termination are integrated in the Modbus client.

  • A Modbus line termination must be connected at the other end (on the last IFM interface or other Modbus server).

• Maximum length (Lmax) of the Modbus trunk cable (excluding tap links):

  • Lmax = 500 m (1,640 ft) at 38,400 Baud

  • Lmax = 1,000 m (3,281 ft) at 19,200 Baud

• A grounding terminal block must be connected to the DIN rail (for example, Linergy part number NSYTRR24DPE or Phoenix Contact part number 3211809). The following components are connected to the ground terminal block:

  • A shield coupling capacitor (for example, Kemet part number C981U103MZVDAA7317).

  • A shield resistor (used to bleed off shield capacitor) with the same operating voltage rating as the shield coupling capacitor.

• The rules for power supply shield connection must be followed.

The following figure shows a Modbus link connecting three pieces of electrical equipment S1 , S2 , and S3 :

• S1 and S2 are bolted together.

• S3 is not bolted to S1 and S2 .

Modbus-SL Network Including IFM Interfaces with Part Number LV434000 and TRV00210

IFM interfaces with part number LV434000 or TRV00210 can be installed on the same Modbus-SL network:

• Any IFM interface with part number TRV00210 present in a ULP system architecture can be replaced by an IFM Interface with part number LV434000.

• IFM interfaces with part number TRV00210 or LV434000 can be connected or stacked together.

Specific rules for ULP connection and power supply apply. Detailed information is described in the appendix related to IFM interface with part number TRV00210 and two-wire RS 485 isolated repeater module.

Example of Wiring Diagram Including IFM Interfaces Grouped in Islands and Modbus Client in the Electrical Equipment

The following wiring diagram is an example. It shows the connections for the Modbus cable and the 24 Vdc power supply:

• The IFM interfaces with part number LV434000 and TRV00210 are grouped in islands via stacking accessories.

• The Modbus client is installed in the same electrical equipment as the IFM interfaces.

Examples of Wiring Diagram Including IFM Interfaces Grouped in Islands and Modbus Client in a Separate Section of Electrical Equipment

The following wiring diagrams are examples. They show the connections for the Modbus cable and the 24 Vdc power supply:

• The IFM interfaces with part number LV434000 and TRV00210 are grouped in islands via stacking accessories.

• The Modbus client is installed in a separate section of electrical equipment from the IFM interfaces where the two sections of electrical equipment are not bolted together.

Example 1: 0 V of power supply is floating.

Section 1 of electrical equipment	Section 2 of electrical equipment

Example 2: 0 V of power supply is connected to local ground.

Section 1 of electrical equipment	Section 2 of electrical equipment

Example of Wiring Diagram Including IFM Interfaces in Daisy-Chain or Star Connection

The following wiring diagram is an example. It shows the connections for the Modbus cable and the 24 Vdc power supply:

• The IFM interfaces with part number LV434000 and TRV00210 are connected in a daisy-chain or in a star connection.

• The Modbus client is installed in the same electrical equipment as the IFM interfaces.

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

Example of Wiring Diagram Including IFM Interfaces in Daisy-Chain or Star Connection Using a RJ45 to Open Connector Modbus Adapter

The following wiring diagram is an example. It shows the connections for the Modbus cable and the 24 Vdc power supply:

• The Modbus cable has free wires.

• The IFM interfaces with part number LV434000 and TRV00210 are connected in a daisy-chain or in a star connection.

• The Modbus client is installed in the same electrical equipment as the IFM interfaces.

Wiring rules:

• 0 VL and 0V of energized LV434000 IFM interface must follow auxiliary power supply rules detailed in ULP system power supply.

• Only one 0V shield connection of SHLD and GND terminals of LV434211 adapter must be connected to the Modbus client.

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