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4-Wire P-NET bus wiring

Wiring examples:

M36 cluster with local power supply for I/O
M36 cluster as bus power supply
Traditional P-NET device connected to 4-WIRE P-NET – bus powered
Traditional P-NET device connected to 4-WIRE P-NET – local power supply
Mixing 4-WIRE P-NET and Traditional P-NET networks

M36 Clusters to 4-WIRE P-NET notes

When M36 modules are connected to the 4-WIRE P-NET bus, power for the cluster can be taken from the bus to power both the communication interface module and the I/O module(s).
Or I/O modules can be powered by a separate power supply and then, due to the Light-Link, achieve total galvanic isolation from the 4-WIRE P-NET system.
(See also: Voltage drop, Power considerations)

M36 cluster with local power supply for I/O

The interface module and one I/O module are powered by the bus. The other I/Os are powered by the local power supply.

M36 cluster as bus power supply

The interface module, one I/O module and the bus are all powered from this unit.

Connecting traditional P-NET devices to 4-WIRE P-NET

Traditional P-NET devices can be connected to 4-WIRE P-NET by utilizing a PD 990 4-WIRE P-NET Conditioner. The P-NET devices can be powered from the 4-WIRE P-NET bus or from a local power supply.

Connection of bus powered traditional P-NET device

Connection of locally powered traditional P-NET device

A local power supply is only permitted when the P-NET interface is galvanically isolated.

Mixing traditional P-NET and 4-WIRE P-NET

This section only applies when traditional P-NET and 4-WIRE P-NET networks (or devices) are directly electrically connected.

When connecting traditional P-NET and 4-WIRE P-NET it is essential that the “S” terminals on the traditional P-NET section do not have any connection to ground!

All “S” terminals on the traditional P-NET must be connected to the PD 990 4-WIRE P-NET Conditioner in order to establish the same “S” reference potential as is generated internally in each 4-WIRE P-NET device.

Separate power source

The 4-WIRE P-NET section and the Traditional P-NET section could each be power supplied from separate power sources:

Common power source:

If the 4-WIRE P-NET section and the Traditional P-NET section is power supplied from the same source, each section should be connected directly to the power source.
It is not recommended to daisy chain the power supply between sections of different P-NET type.

The P-NET (A and B wires) can be connected as a P-NET ring or P-NET bus topology.
If bus topology is used, a PD 990 4-WIRE P-NET Conditioner or a BM 010, depending of the P-NET type, must terminate each end of the bus.

It is recommended always to use 2 x twisted pair P-NET cable for the traditional P-NET section. One pair for “A” / “B” and one pair for “S”. This allows the shield to be connected to ground.

Assuming a 1 x twisted pair was used, the shield had to be used for the “S” terminals. In this case it would not be allowed to connect the shield to ground. Not connecting the shield to ground will result in an inefficient shielding effect, thus a 1 x twisted pair is not recommended.