ABB 07CR41, Operating Manual, Page: 55 / 124

Advant Controller AC 31 / Issued: 08.99
4 – 7 Installation
3
4.2 Basic unit and remote unit cabling
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Power supply
The connection of an external thermal fuse is necessary to ensure protection of the devices.
An internal 24 V d.c. power supply is available on 120/ 230 V a.c. versions. This power supply
feeds the digital inputs of the unit and its extensions. The maximum current is 400 mA. This
internal power supply is protected against short circuits and overloads. In such cases it is
available again 10 seconds after elimination of the fault.
It is also possible to use an external 24 V d.c. power supply. In this case, do not forget to
connect the earth of the external 24 V d.c. power supply to terminal C.
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Inputs/outputs cabling
Use rigid or multi-conductor AWG 18 (0.96 mm²) to AWG 14 (1.95 mm²) wires for inputs, and
rigid or multi-conductor AWG 14 (1.95 mm²) wires for the outputs.
- Input cabling: see Figures 12, 13, 14 and 15.
- Output cabling: see Figures 16 and 17.
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Output protection
The relay outputs must be protected externally against disturbances generated by an
inductive load by using the following:
- a varistor or an RC module, with alternating current loads
- a free-wheeling diode with DC loads
The presence of an external thermal fuse, connected to the common power supply of the
outputs, protects the devices connected to the outputs.
The transistor outputs are protected internally against short circuits and overloads. However,
with an inductive load, where L/R is greater than 40 ms, it is necessary to add a free-wheeling
diode.
If an error occurs at one of the transistor outputs, it is reported by the basic unit.
The presence of an external thermal fuse, connected to the common power supply of the
outputs, protects the devices connected at the outputs and also prevents unit damage in the
event of overload at several outputs.