Modbus SL Connection Rules

Introduction

The Modbus client can be installed either:

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

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

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

Connection of Modbus SL Hub to Modbus-SL Client

Connection to the Modbus-SL client depends on the number of Modbus SL hubs.

To connect a single Modbus SL hub, connect it via the stacking accessory and with an IFE server or via a terminal block connector with a Panel Server gateway.

To connect several stacked Modbus SL hubs, use the RJ45 Modbus cable.

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 and Modbus SL hubs 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 and Modbus SL hubs 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 and Modbus SL hubs and in the electrical equipment.

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

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

• Wiring diagram including IFM interfaces and Modbus SL hubs in daisy-chain or star connection and Modbus client installed in the 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 Modbus SL hub interfaces is connected to a Modbus client outside the electrical equipment.

• The Modbus-SL network between the Modbus SL hubs 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 and Modbus SL hub grouped in islands and Modbus client installed in a separate section of electrical equipment from the IFM interfaces and Modbus SL hub 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 Modbus SL hub 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 9,600 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, TRV00210, and Modbus SL Hub

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

Modbus SL hub can be connected or stacked together with IFM interfaces with part number TRV00210 or LV434000.