1. General remarks
Low-voltage switchgear has to fulfil mainly the following
functions in electrical energy systems:
- switching (in the sense of
- protecting and
- limiting of the short-circuit
Since the field of application of low voltage is very extensive,
there is a large variety of low-voltage switchgear.
Switches are devices for opening and closing electric circuits
in which all parts necessary for connecting or disconnecting are mounted firmly
on a joint base.
Relays are devices which are influenced by the change of
physical magnitudes and control electrically further devices.
Trips are devices which are influenced by the change of physical
magnitudes and control mechanically further devices.
Regulators are devices provided with resistances for changing
the operating state of electric operating means whose resistance remains
permanently switched on in the circuit.
Plug-and-socket connectors are devices for establishing
connections of current paths without additional auxiliary means, with connection
for electric supply lines.
Fuses are devices for interrupting current paths by melting of a
piece of fusible metal when a current is exceeded in a given period of time. The
fuse comprises all components of which the complete device