1. General remarks

Low-voltage switchgear has to fulfil mainly the following functions in electrical energy systems:

- disconnecting
- switching (in the sense of arbitrary switching)
- protecting and
- limiting of the short-circuit current.

Since the field of application of low voltage is very extensive, there is a large variety of low-voltage switchgear.

Switches

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

Relays are devices which are influenced by the change of physical magnitudes and control electrically further devices.

Trips

Trips are devices which are influenced by the change of physical magnitudes and control mechanically further devices.

Regulators

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

Plug-and-socket connectors are devices for establishing connections of current paths without additional auxiliary means, with connection for electric supply lines.

Fuses

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 consists.