Installation
ABB Control - AC 31 Page 4-5
1SBC 260400 R1001-b 06.99
1.3. Earthing
1.3.1. Basic earthing principles
Use rigid wires or multi-conductor wires AWG 14 (1.95 mm
2
).
The earth and mains wires should be connected in star.
All AC 31 components of a cabinet should be connected to the same earth.
When the remote units are situated outside the cabinet they should be connected to the
nearest earth.
The 40 and 50 series central units are fitted with an earth plate with the DIN rail mounting
system. Also, if the central unit is screwed directly to a metal plate, the screw located at the top
left of the central unit (as seen from the front) ensures an electrical connection to the earth via
the earth plate.
This earthing ensures protection against electromagnetic disturbances.
The safety earthing cable (on terminal block) should be connected to the cabinet chassis.
1.3.2. Earthing principles for numerous cabinets
When the cabinets are close to each other the different earths should be connected together
using a cable with a cross section of at least 16 mm² (see Figure 4-1).
The noise generating devices (actuators, motors, etc.) should not be earthed in-between two
cabinets. The earthing should be done near to the element causing the most disturbance (see
Figure 4-2).
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