Rules for ULP Connection and Power Supply

Power Supply Connection Rules

• The 0 V terminal on IFM interfaces is connected to a functional ground terminal block at only one point of the Modbus line. This point of the Modbus line is either the first stacked IFM or the Modbus client if IFM interfaces are not stacked with IFE server. No other devices must have 0 V connected to ground.

  A	ComPacT NSX , ComPacT NS , or MasterPact NT/NW circuit breaker

• If no IFM interface is installed on the ULP system, 0 V must be connected to a ground terminal block at power supply level. No other devices must have 0 V connected to ground.

• No Modbus device with dedicated 0 V Modbus (for example, Acti 9 Smartlink device) must be connected to an IFM interface. The IFM interface has indeed no dedicated 0 V Modbus. The following diagram illustrates this rule for Acti 9 Smartlink devices:

• If no IFM interface or ComPacT NSX circuit breaker is installed on the ULP system, it is recommended to have a floating auxiliary power supply. Do not connect terminals + and - of the 24 Vdc auxiliary power supply output to ground.

Segmented Power Supply

Segmented power supplies are required in the following cases:

• When the IMUs communicate over Modbus by using the IFM interface, the Modbus cable distributes the 24 Vdc power.

  • If the length of the Modbus cable is such that the voltage drop is excessive (for example, cable longer than 15 m (49.2 ft) with a 3 A power supply), independently powered Modbus cable segments must be created:

  • Only the 24 Vdc wire is interrupted between two segments

  • The continuity of the 0 V wire (which is also the Modbus common) must be assured along the entire length of the Modbus network.

  • The maximum number of power supply segments is three segments for a single Modbus network.

• When an installation consists of a number of Modbus networks, one 24 Vdc power supply must be used for each Modbus network.

  • Since the 0 V of the 24 Vdc power supply is also the Modbus common, the power supplies must be separated to make the Modbus networks independent from one another.

Connection of the 0 V Circuit

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION OR ARC FLASH Connect the 0 V circuit (Modbus common and 0 V of the 24 Vdc power supply) to the protective earth ground. Failure to follow these instructions will result in death or serious injury.

The rules for connection of the 0 V circuit must be followed:

• For the power supply and for all ULP modules of an IMU, a stainless steel DIN rail is recommended rather than an aluminum one in order to provide the most consistent ground. Each DIN rail must be connected to the protective ground.

• If no IFM interface is installed on the ULP system, 0 V must be connected to a ground terminal block at power supply level. No other devices must have 0 V connected to ground.

• If there is at least one IFM interface in the architecture, connection on IFM interfaces must be done as follows:

  • If one or several IFM interfaces are stacked on an IFE server, then at least one of the IFM interfaces must have a jumper on its connector between the 0 V terminal and the protective ground.

    

    NOTICE
    HAZARD OF SIGNIFICANT CURRENT LOOP ON THE SYSTEM When IFM interfaces are present in the architecture, do not connect the 0 V of the power supply on the stainless steel DIN rail. Failure to follow these instructions can result in equipment damage.

  • Do not connect the 24 Vdc of the 24 Vdc power supply to the protective ground.

  • In architectures with one or several IFM interfaces, no power supply should be grounded if there are one or several power supply segments on a single Modbus network.

    

    A	24 Vdc ABL8 power supply for ULP modules
    B	Stainless steel DIN rail
    C	IFE interface or IFE server
    D	IO module
    E	FDM121 display

    The following figure shows the daisy-chain power supply:

• In architectures without IFM interface, the power supply on the second and third segments should be grounded.

Modbus Cable Connection

• The Modbus cable coming from the Modbus client ensures continuity of the Modbus signal (D0, D1, and 0 V). The 24 Vdc wire is not connected when the Modbus client is powered separately.

• The Modbus cable running to the first cubicle ensures continuity of the Modbus signal (D0, D1, and 0 V) and the 24 Vdc power supply for the cubicle.

• The unused channel on the shunt terminal block can be used to connect another Modbus server in the electrical equipment (a PM800 communicating power meter, for example).