Daisy-Chained Distributed Modbus Architecture

The following figure shows an example of a daisy-chained distributed Modbus architecture with seven IMUs:

An IMU consisting of a PowerPacT P- and R-frame circuit breaker and an IFM interface.
Six IMUs consisting of a PowerPacT H-, J-, and L-frame circuit breaker, an IFM interface, and an FDM121 display each.

A	Modbus cable coming from Modbus client
B	24 Vdc AD power supply for MicroLogic trip units in MasterPacT NT/NW or PowerPacT P- and R-frame circuit breakers
C	Shunt terminal block on the incoming supply
D	24 Vdc ABL8 power supply for ULP modules
E	Modbus cable running to first cubicle
F	NSX cord
G	RJ45 plug ULP cord
H	RJ45 Modbus T-junction
I	IFM interface
J	Modbus cable running to second cubicle
K	Modbus line termination

Cable	Description
	Modbus network
	ULP network
	24 Vdc power supply

For a distributed Modbus architecture, RJ45 Modbus T-junction can be used to connect the upstream Modbus cable and the downstream Modbus cable.

NOTE: Recommendations for installing the Modbus T-junction:

To route cables of the Modbus T-junction, take into account the cable bending radius.
The Modbus T-junction must be installed on DIN rail using EMC clamps. Avoid excessive mechanical stress on the case when screwing the T-junction to the DIN rail.

Shunt Terminal Block on the Incoming Supply

The shunt terminal block on the incoming supply can connect the Modbus cable and the power supply for all the IMUs.

The shunt terminal block consists of four 5-channel spring terminal blocks.

The following figure shows the shunt terminal block on the incoming supply in detail:

A	24 Vdc power supply
B	Modbus cable coming from Modbus client
C	Clip-on plastic end stop
D	End plate
E	Spring terminal block
F	Modbus cable running to first cubicle

The following table lists the part numbers for the shunt terminal block:

Component	Nominal cross-section	Part number
5-channel spring terminal block	2.5 mm² (14 AWG)	NSYTRR24D+NSYTRALV24 (gray)
End plate	–	AB1 RRNACE244
Clip-on plastic end stop	–	AB1 AB8R35

Modbus Cable Connection

The Modbus cable coming from the Modbus client ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).
The Modbus cable running to the first cubicle ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail) for the cubicle.

The 24 Vdc power supply running to the first cubicle ensures continuity of the power supply.
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).

Wiring Diagram of Shunt Terminal Block on the Incoming Supply

A	24 Vdc power supply
B	Modbus cable coming from Modbus client
C	24 Vdc power supply cable running from Modbus servers
D	Modbus cable running to Modbus servers
E	24 Vdc power supply cable running to Modbus servers

NOTE: For information about shield connection, refer to the 24 Vdc power supply cable characteristics.

Modbus Cable Lengths for a Single Power Supply Segment

The following figure shows the Modbus cable lengths in detail for a daisy-chained distributed Modbus architecture with a single power supply segment:

A	Shunt terminal block on the incoming supply
B	Modbus line termination

The total length of all L2s must be less than L1.

Case of Several Power Supply Segments

When more than one 24 Vdc power supply is needed (refer to segmented power), then several power supply segments are used along the Modbus cable.

The following figure shows a daisy-chained distributed Modbus architecture with two power supply segments:

A	Modbus cable coming from Modbus client
B	24 Vdc AD power supply for MicroLogic trip units in MasterPacT NT/NW or PowerPacT P- and R-frame circuit breakers
C	Shunt terminal block on the incoming supply
D	24 Vdc ABL8 power supply for ULP modules
E	Modbus cable running to first cubicle
F	NSX cord
G	RJ45 plug ULP cord
H	RJ45 Modbus T-junction
I	IFM interface
J	Modbus cable running to second cubicle
K	Modbus cable running to third cubicle
L	Shunt terminal block on the cubicle incomer
M	Modbus line termination

Cable	Description
	Modbus network
	ULP network
	24 Vdc power supply

Shunt Terminal Block on the Incomer of the Third Cubicle

The shunt terminal block on the incomer of the third cubicle can be used to connect a new 24 Vdc power supply to power the IMUs in the third cubicle.

The shunt terminal block consists of four 5-channel spring terminal blocks.

The following figure shows the shunt terminal block on the incomer of the third cubicle in detail:

A	24 Vdc power supply
B	Modbus cable coming from second cubicle
C	Clip-on plastic end stop
D	End plate
E	Spring terminal block
F	Modbus cable rising up the third cubicle

Modbus Cable Connection

The Modbus cable from the Modbus client ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).
The Modbus cable running to the first cubicle ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail) for the cubicle.

The 24 Vdc power supply running to the first cubicle ensures continuity of the power supply for the cubicle.
The Modbus cable running to the second cubicle ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail) for the second cubicle.

The 24 Vdc power supply running to the second cubicle ensures continuity of the power supply for the second cubicle.
The Modbus cable running to the third cubicle ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

A separate 24 Vdc power supply is connected to the third cubicle.

Wiring Diagram of Shunt Terminal Block on the Incomer of the Third Cubicle

A	24 Vdc power supply
B	Modbus cable coming from second cubicle
C	Modbus cable rising up the third cubicle
D	24 Vdc power supply cable rising up the third cubicle

NOTE: For information about shield connection, refer to the 24 Vdc power supply cable characteristics.

Modbus Cable Lengths for Several Power Supply Segments

The following figure shows the Modbus cable lengths in detail for a daisy-chained distributed Modbus architecture with several power supply segments:

A	Shunt terminal block on the cubicle incomer
B	Modbus line termination

Modbus cable L3 ensures continuity of the Modbus signal (D0, D1, and 0 VL) and shield continuity by using brass clamps. The brass clamps must have suitable diameter for the cable type and fixings compatible with the installation (for example, screw or DIN rail).

The total length of all L2s must be less than L1 in the corresponding installation.