Fieldbus Modules For Abb Drives; Common Recommendations - ABB ACS310 Quick Start Manual

Quickstart Guide
ABB PLC and drives integration using Modbus RTU
Fieldbus modules for ABB drives
The following ABB drives Modbus RTU modules have an option to activate built‐in end termination and pull‐
up/pull‐down resistors.

RMBA‐01 (used with for instance ACS550 and ACS800)

FSCA‐01 (used with for instance ACS880 and ACSM1)
The following ABB drives Modbus RTU module does not have an option to activate built‐in end resistors including
pull‐up/pull‐down resistors.

FMBA‐01 (used with for instance ACS355)
Since the built‐in end termination of the modules (RMBA‐01 and FSCA‐01) automatically also activates pull‐
up/pull‐down resistors, it is recommended to skip the built‐in option.
It is recommended to connect a separate end termination resistor to the first node (i.e. the PLC COM interface)
and the last node (i.e. the last drive on the bus).
For connection examples, see chapter "Installation examples".
Common recommendations
Note! The following bullets are only recommendations and no general rules.

Installation where total cable length is more than 50 m
o Use CPU AC500 rather than AC500‐eCo or AC500‐eCo with TK506 RS 485 isolator for COM1.

Installation where there is a risk that ground connections in different nodes could vary in voltage potential
(typically in ship installations or with cable lengths more than 50 m).
o Use CPU AC500 and do not connect ground cable, only shield → 2‐wire solution, or use AC500‐eCo
with TK506 RS 485 isolator for COM1.

When AC500‐eCo is used
o Use of 3‐wire connection is recommended because the COM interface is not opto‐isolated,
or use AC500‐eCo with TK506 RS 485 isolator for COM1.
o Use of
or use AC500‐eCo with TK506 RS 485 isolator for COM1.

Cable type
o Use only cables with twisted pair wires and braided shields. Foil shields are not robust enough,
cannot be contacted well and have poor HF (High Frequency) properties.
o Ground the cable shield directly with a clip when entering the switch‐gear cabinet. Do not cut the
shield until the cable reaches the connected module.
o The connection between the PE bar and the shield bar must have low impedance.
o Use ABB cable TK505 when suitable for easy installation.
Modbus RTU
cable length more
‐ 8 ‐
than 50m should be realized with
PLC and drives integration
repeaters,