Modbus Cable Characteristics

Introduction

When a Modbus cable other than Schneider Electric part number 50965 is used, it must have the following characteristics:

• Shielded cable with two twisted-pairs:

  • One communication pair for the RS 485 signal, with typical impedance of 120 Ω and minimum cross-section 0.25 mm² (24 AWG). The recommended colors for the wires are white and blue.

  • One 24 Vdc power supply pair. The cross-section depends on the current to be carried and the length of the Modbus cable required, with the following restrictions: 0.32 mm² (22 AWG) minimum for a 1 A 24 Vdc power supply, and 0.5 mm² (20 AWG) minimum for a 3 A 24 Vdc power supply.

    The recommended colors for the wires are black and red.

• Shielding braid, with shielding drain wire (for connecting the shield to the ground terminal on the 5-pin connector of the IFM Modbus-SL interface for one circuit breaker).

• Nominal insulation voltage of the outer sheath: 300 V minimum.

Cable must be compliant with installation requirements for voltage and temperature ratings. It is the responsibility of the user to select for correct cable for the specific installation.

Connection Rules

The Modbus cable recommended below must follow the rules and recommendations for connection defined in this guide.

Part Numbers

The following table lists two recommended Modbus cable part numbers: