Wiring Rules

The following wiring rules must be respected in order to reduce disturbance due to EMC on the behavior of the LTMT main unit:

• Keep a distance as large as possible between the communication cable and the power or control cables (30 cm or 11.8 in. is recommended).

• Cross over the Modbus RTU cables and the power cables at right angles, if necessary.

• Install the communication cables as close as possible to the grounded plate.

• Do not bend or damage the cables. The maximum bending radius is 10 times the cable diameter.

• Avoid sharp angles of paths or passage of the cable.

• Use the recommended cables only. For more information, refer to Cables section in TeSys Tera Motor Management System User Guide – DOCA0257EN.

• Modbus RTU cable must be a shielded twisted pair cable:

  • The twisted pair cable shield must be connected to a protective ground.

  • The connection of the twisted pair cable shield to the protective ground must be as short as possible.

  • Connect together all the shields, if necessary.

  • Connect the shield to the terminal.

  • Perform the grounding of the shield with a metal clip.

  

• When the LTMT main unit is installed in a withdrawable drawer:

  • Connect together all the shield contacts of the withdrawable drawer part of the auxiliary connector to the ground of the withdrawable drawer to create an electromagnetic barrier.

  • Do not connect the cable shield at the fixed part of the auxiliary connector.

• Place a line terminator at each end of the bus to avoid malfunctions on the communication bus. A line terminator is generally already integrated in the client.

• Wire the bus between each connector directly, without intermediate terminal blocks.

• The common polarity (0 V) must be connected directly to protective ground, preferably at one point only for the entire bus. In general, this point is chosen either on the client device or on the polarization device.

For more information, refer to Electrical Installation Guide (available in English only).