LC700 – Users Guide
4.6
Most of the modules do not have visible chassis grounding, nor a connector or a ground terminal,
but they are mounted in the rack, on the DIN rail. The chassis of these modules are grounded by the
DIN rail, through the rear ground spring. In this DIN rail, put a ground connector and connect it to the
BTC ground bar through an individual conductor.
BTC - Housing Ground Bar
The BTC potential is the ground reference for every AC electric part of the equipments inside the
panel. Connect the BTC to the plant’s ground mesh using a copper conductor with 8 AWG
specification, at least, for protection against EMI.
BTA - Analog Ground Bar
The BTA potential is the ground reference for every analog and digital part of the equipments inside
the panel. Connect the BTA to the grounding-electrode system using a copper conductor with 8
AWG specification, at least, for protection against EMI.
Shielded Cables
Some I/O connections, as analog signals, communication, pulse inputs, need shielded cables to
help reduce the effects of electric coupling.
- Each shied must be grounded in only single point. A shield grounded at both ends forms a
ground loop which can cause a system to fault;
- Connect each shield directly on the Analog Ground Bar (BTA);
- Use twisted pair cable.
Avoid interruption of the shield in the junction boxes. Many types of connections of shielded
conductors are available by several manufacturers. If the user needs to interrupt the shield in a
junction box, proceed as follows:
- Connect only Category 2 conductors in the junction box.
- Do not remove the shield protection more than the necessary to do the connection.
- Connect the shields of the two cable segments guaranteeing the continuity along the cable
length.
Energy Distribution
To isolate the plant’s noises, the user can use an isolation transformer to connect the power supply.
The transformer provides DC isolation and protects the equipment against high voltage transient
that can be generated by the energy distribution system.
In many industrial applications a step-down transformer is already necessary to reduce the voltage
to 120 or 220 VCA.
To Next Page
Loading...
