2
1
Max 25 Nm
Fig. 9
7.6. Power circuit connections of
fixed circuit-breakers
7.6.1. General recommendations
• Choose the conductor cross-sections to suit the
service current and short-circuit current of the
installation.
• Provide suitable supporting insulators near the
terminals of the fixed circuit-breaker or enclosure,
sized according to the electrodynamic stress
caused by the short-circuit current of the
installation.
7.6.2. Assembly of connections
• Make sure that the contact surfaces of the
connections are perfectly flat and without burrs,
traces of oxidation or deformities caused by
drilling or impact sustained.
• The operations indicated in the following table T1
must be performed on the contact surface of the
conductor, depending on the conductive material
used and the surface treatment given.
Assembly procedures
• Put the connections in contact with the circuit-
breaker terminals. Take care to avoid mechanical
stress (tensile / compressive) exercised, for
example, by the busbars on the terminals
themselves.
• Insert a spring washer and flat washer between
the bolt head and connection.
•
Use of DIN class 8.8 standard bolts is
recommended. Refer also to the indications in
table T2.
• In the case of cable connections, carefully comply
with the manufacturer’s instructions when making
the terminations.
T1
Bare copper
•
Clean with a fine file or emery cloth.
•
Fully tighten and smear 5RX Moly grease over the contact
surfaces.
Copper or silver-plated aluminium
•
Clean with a rough dry cloth.
•
Only if there are traces of oxidation that are difficult to
shift, clean with ultra-fine grain emergy cloth and take care
not to remove the surface layer.
•
Repeat the surface treatment if necessary.
Bare aluminum
•
Clean with a metal brush or emery cloth.
•
Immediately smear neutral grease over the contact
surfaces.
•
Insert a bi-metal copper-aluminum strip with dressed
surfaces between the aluminum connection and copper
terminal (copper side touching the terminal, aluminum side
touching the connection).
T2
Bolt
Recommended tightening torque (1)
Without lubricant
With lubricant (2)
M6
10.5 Nm
4,5 Nm
M8
26 Nm
10 Nm
M10
50 Nm
20 Nm
M12
86 Nm
40 Nm
M16
200 Nm
80 Nm
(1) The nominal tightening torque is based on 0.14 thread friction coeffi-
cient (distributed value to which the thread is subjected and which, in
some cases, is not negligible). The nominal tightening torque with lu-
bricant complies with DIN 43673 Standards.
(2) Oil or grease. Lubricated thread and surfaces in contact with head.
Bear in mind the deviations from the general Standards table (e.g. for
systems in contact or terminations) as established in the specific tech-
nical documentation. The thread and surfaces in contact with bolt
heads must be slightly oiled or greased, so as to obtain a correct nomi-
nal tightening torque.
—
7. Installation
Racking-in
Racking-out
28
V D4 G
I N S TA L L AT I O N A N D O P ER AT I N G I N S T R U C T I O N S
