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B-32
Distribution
Definition of Form 4
separation of busbars from the functional units and separation of all functional
units from one another, including the terminals for external conductors which are an
integral part of the functional unit
protection against contacts with live parts and reduction in the risk of faults
between the functional units (propagation of electrical arcs, etc.).
The two types of Form 4 separation as defined by IEC 60439-1
b
b
DD382369
DD382370
Form 4a.
Form 4b.
Form 4a
Terminals for external conductors in the same compartment as the associated
functional unit.
Form 4b
Terminals for external conductors not in the same compartment as the associated
functional unit, but in individual, separate, enclosed protected spaces or
compartments.
b
b
Form 4 configuration
Form 3 switchboard with covers over the terminals for
external conductors.
Prisma Plus offers both Form 4a and Form 4b.
In addition to partitioning of the main busbars (Form 2) and installation of the
horizontal partitions between functional units (Form 3), the cubicle must be equipped
with:
Form 4 gland plates to achieve Form 4a
Form 4 covers for connection transfer assemblies to achieve Form 4b.
b
b
Dd383602
Form 4 partitioning: Form 4a (cubicle on left) and Form 4b (cubicle on right).
Form 4 partitioning
Main distribution