19
Fig. 8
7.6. Power circuit connections
7.6.1. General warnings
– Check that the circuit-breaker terminals are clean and are free of any
deformation caused by shocks received during transport or storage.
– Select the conductor cross-section according to the service and
short-circuit current of the installation.
– Provide suitable supporting insulators near the fixed circuit-breaker
terminals or the monoblocs of the units, sized according to the
electrodynamic stresses caused by the short-circuit current of the
installation.
The circuit-breaker terminals are always silver-plated. To
clean them, only use dry rags, soaked in a suitable solvent
if necessary.
N.B. Never use a file or emery cloth!
7.6.2. Maximum dimensions of the connections
For the fixed version VD4 circuit-breakers, the connections must be
shaped and installed in conformity with what is indicated in the overall
dimensions, respecting the distances indicated.
7.6.3. Surface treatment of connections
The connections can be made of bare copper or bare aluminium. However,
it is always advisable to silver-plate the contact surfaces.
The surface treatment must have an even and constant thickness.
7.6.4. Mounting connections
– Check that the contact surfaces of the connections are perfectly flat
and do not have any burrs, traces of oxidation or any deformities due
to drilling or shocks.
– According to the conductive material used and the surface treatment
given, carry out the operations indicated in the following table T1 on
the surface contact of the conductor.
7.3.
Preliminary operations
– Clean the insulating parts with clean dry rags.
– Check that the upper and lower terminals are clean and free of any
deformation caused by shocks received during transport or storage.
7.4.
Installation of
fixed
circuit-breakers
The circuit-breaker can be mounted directly on the floor or on supporting
frames provided by the customer (see fig. 8).
The areas on which the supporting frames or truck (if provided) rest
must be on the same plane to avoid any risk of distortion in the breaker
structure.
A minimum degree of protection (IP2X) must be guaranteed from the
front towards live parts.
Fixing can be carried out in the following ways:
– by means of special expansion anchoring bolts with M8 threaded hole
in the case of fixing to cement floors
– by means of M8 bolts in the case of fixing onto metal structures or to
cement floors where special steel sections have been embedded.
In any case, the fixing surface must be well-levelled and all the resting
points must be on the same horizontal plane.
7.5. Installation of
circuit-breaker
for ABB switchgear
The removable circuit-breakers are destined for use in UniSwitch, UniAir
or UniMix switchgear. Special assembly operations are not usually
necessary.
In any case, consult the documentation relative to the switchgear.
Bare copper
– Clean with a fine file or emery cloth
– Smear a film of 5RX Moly grease over the
contact surfaces
Silver-plated copper or aluminium
– Clean with a rough dry cloth
– Only in case of tough oxidation traces, clean with a very
fine emery cloth, taking care not to remove the surface
layer
– If necessary, carry out surface treatment again.
Bare aluminium
– Clean with a metallic brush or emery cloth
– Immediately smear a film of neutral grease over the contact
surfaces
– Insert the bi-metal copper-aluminium strip with beaded
surfaces between the aluminium connection and the copper
terminal (copper side touching the terminal; aluminium side
touching the connection).
T1
